Photofunctional Nanomaterials for Biomedical Applications E-Book
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- Herausgeber: Wiley-VCH
- Kategorie: Fachliteratur
- Sprache: Englisch
Summary of the controlled synthesis of photofunctional nanoparticles and their hybrid nanocomposites, as well as their potential in biomedical applications
Photofunctional Nanomaterials for Biomedical Applications presents the latest research and developments surrounding photofunctional nanomaterials, including rare earth luminescence nanomaterials and photothermal agents, for biomedical applications related to imaging, biosensing, controlled drug delivery and release, and tumor diagnosis and therapy, as well as other applications such as bacteria engineering, optical information storage, acoustic sensing, and temperature detection. The book elucidates the underlying functioning mechanisms of these nanomaterials in depth and extensively discusses their current challenges and future development prospects.
Written by two highly qualified professors with significant research experience in the field, Photofunctional Nanomaterials for Biomedical Applications discusses sample topics including:
- Fabrication of composites based on lanthanide-doped up conversion nanomaterials and metal-organic frameworks
- Photosensitizers for photodynamic therapy (PDT), covering basic principles of PDT, classifications of various photosensitizers, mechanisms during treatment, and x-ray-activated PDT
- Nanomaterials-induced pyroptosis and immunotherapy including pyroptosis pathways and their potential in immunotherapy, especially in activating effector T cells and promoting dendritic cell maturation
- Design of ternary quantum dots, antibacterial mechanisms in photofunctional antibacterial nanomaterials, and inorganic nanomaterials in photothermal therapy
Establishing a robust groundwork for the future clinical translation, Photofunctional Nanomaterials for Biomedical Applications is an essential up-to-date reference on the subject for materials scientists, photochemists, biochemists, and electronic engineers.
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Veröffentlichungsjahr: 2025
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Table of Contents
Cover
Table of Contents
Title Page
Copyright
Foreword
Preface
Acknowledgments
1 General Introduction and Background of Photofunctional Nanomaterials in Biomedical Applications
1.1 Introduction to Nanomaterials
1.2 Introduction and Classification of Photofunctional Nanomaterials
1.3 Introduction to Nanobiomedicine
1.4 Classification of Photofunctional Nanomaterials
1.5 Conclusion
References
2 Mechanism in Rare-Earth-Doped Luminescence Nanomaterials
2.1 Introduction
2.2 Composition of RE-Doped Luminescence Nanomaterials: Substrate (Host), Activator, and Sensitizer
2.3 Mechanism of RE-Doped Luminescence Nanomaterials
2.4 Luminescence Modulation
References
3 Upconversion and NIR-II Luminescence Modulation of Rare-Earth Composites Using Material Informatics
3.1 Introduction
3.2 Typical Processes of Upconversion Luminescence
3.3 Synthesis Methods of Upconversion Nanoparticles
3.4 Material Informatics in UCL
3.5 Cancer Therapy Based on UCNPs
3.6 Conclusion and Perspective
References
4 Composites Based on Lanthanide-Doped Upconversion Nanomaterials and Metal-Organic Frameworks: Fabrication and Bioapplications
4.1 Introduction
4.2 Fabrications of Composites
4.3 Bioapplications
4.4 Conclusion and Perspectives
References
5 Lanthanide-Doped Nanomaterials for Luminescence Biosensing and Biodetection
5.1 Introduction
5.2 Basics of Optical Bioprobe and Lanthanide-Doped Nanoparticles
5.3 Synthesis and Functionalization of Lanthanide-Dope Nanocrystals
5.4 Applications of Luminescence Biosensing and Biodetection
5.5 Integrated Devices for Point-of-Care Testing
5.6 Summary
References
6 Rare Earth Luminescent Nanomaterials for Gene Delivery
6.1 Introduction
6.2 UCNPs Nanovectors
6.3 Surface Modification
6.4 Increasing Endosomal Escape
6.5 Controlling Delivery Strategy
6.6 Gene Therapy and Syndication
6.7 Other Lanthanide-Based Nanovectors
6.8 Perspective
References
7 Biosafety of Rare-Earth-Doped Nanomaterials
7.1 Internalization of UCNPs into Cells
7.2 Distribution of UCNPs
7.3 Excretion Behavior of UCNPs
7.4 The Toxic Effect of Cell Incubated with UCNPs
7.5 Toxic Effect of UCNPs In Vivo
7.6 Conclusions and Prospects
References
8 Design and Construction of Photosensitizers for Photodynamic Therapy of Tumor
8.1 Introduction
8.2 Small Molecule Photosensitizers
8.3 Metal Complexes
8.4 Inorganic Photosensitizers
8.5 Conclusions and Perspectives
References
9 Persistent Luminescent Materials for Optical Information Storage Applications
9.1 Introduction
9.2 Luminescent Mechanism of Persistent Luminescent Materials with Deep Traps
9.3 Persistent Luminescent Materials with Deep Traps
9.4 Outlooks
References
10 The Application of Ternary Quantum Dots in Tumor-Related Marker Detection, Imaging, and Therapy
10.1 Introduction
10.2 Conclusion
References
11 Nanomaterials-Induced Pyroptosis and Immunotherapy
11.1 Discovery and Definition of Pyroptosis
11.2 Mechanisms of Pyroptosis
11.3 Pyroptosis and Tumor Immunotherapy
11.4 Summary and Outlook
References
12 NIR Light-Activated Conversion Nanomaterials for Photothermal/Immunotherapy
12.1 Introduction
12.2 The Photothermal Conversion Mechanism
12.3 Classification of Inorganic Photothermal Materials
12.4 Mechanisms of PTT and Immunotherapy
12.5 Nanomaterial-Based Photothermal/Immunotherapy
12.6 Summary and Outlook
References
13 Near-Infrared Region-Responsive Antimicrobial Nanomaterials for the Treatment of Multidrug-Resistant Bacteria
13.1 Introduction
13.2 The Antibacterial Mechanisms of Photofunctional Antibacterial Nanomaterials
13.3 Photofunctional Nanomaterials and Antibacterial Activity Against MDR Bacteria
13.4 Limitations and Challenges
13.5 Conclusions
References
14 Photoelectrochemical Nanomaterials for Biosensing Applications
14.1 Introduction
14.2 Classification of Photoelectrochemical Materials
14.3 Introduction to Biorecognition Elements
14.4 Factors Affecting the Photocurrent Signal
14.5 Signal Amplification and Bursting Strategies
14.6 Applications of Photoelectrochemical Biosensors
14.7 Challenges and Potential Clinical Applications
References
15 X-Ray-Induced Photodynamic Therapy for Deep-Seated Tumors
15.1 Introduction
15.2 Mechanisms of Interaction Between X-Rays and Scintillation Materials
15.3 X-Ray-Sensitive Materials
15.4 X-Ray-Activated Therapy
15.5 Conclusions and Perspectives
References
16 Conclusions and Perspectives
Index
End User License Agreement
List of Tables
Chapter 8
Table 8.1 Summary of organic photosensitizers.
Chapter 9
Table 9.1 Representative deep-trap PersL materials and their major propertie...
Chapter 13
Table 13.1 The application of representative NIR-responsive gold nanomateria...
Table 13.2 MDR antibiotics.
List of Illustrations
Chapter 1
Figure 1.1 Inorganic light-responsive nanomaterials have been widely applied...
Figure 1.2 Summary of photoactive nanomaterials for regulation of biomolecul...
Figure 1.3 (a) Energy diagrams for bulk semiconductor and QDs. (b) Example o...
Figure 1.4 (a) Illustration of the detection of pathogen bacteria with the p...
Figure 1.5 Development and application of rare earth-based nanomaterials. Th...
Figure 1.6 Schematic illustration of the principles of imaging modes and cor...
Figure 1.7 Schematic illustration of upconversion nanoparticles based FRET a...
Figure 1.8 (a) Planar luminophoric molecules such as perylene tend to aggreg...
Figure 1.9 Overview of the mechanisms, categories, and applications of photo...
Figure 1.10 Schematic illustration of the preparation of organic phototherma...
Figure 1.11 (a) Schematic view of the cancer cells recognized by the immune-...
Figure 1.12 Schematic representation of the preparation of PDMS-PA-BP-PQ nan...
Figure 1.13 (a) Schematic therapeutic process of the biomineralized melanin ...
Figure 1.14 Nanoparticles in photodynamic therapy.
Figure 1.15 (a) Schematic illustration demonstrates that X-ray-induced persi...
Figure 1.16 (a) UCNPs structured with an energy-concentrating zone to boost ...
Figure 1.17 (a) Schematic of the general instrumentation and working princip...
Figure 1.18 Schematic diagram of PEC bioassay based on local surface plasmon...
Figure 1.19 Schematic illustration of this PEC assay for DNA detection based...
Figure 1.20 Illustration of a signal-switchable photoelectrochemical biosens...
Figure 1.21 (a) Photoacoustic generation. (1) Light absorption in a light-ab...
Figure 1.22 (a) Schematic showing bacteria eating gold nanoparticles for agg...
Figure 1.23 (a) Rational design of dyes GX as a novel class-activated NIR-II...
Figure 1.24 (a) Schematic diagram showing the mechanism of CTSK-APPA for ima...
Chapter 2
Figure 2.1 Energy level diagrams of trivalent Ln
3+
ions in CaF
2
. Typical...
Figure 2.2 Scheme for the CF splitting of the electronic ELs of Eu
2+
ion...
Figure 2.3 Schematic illustration of UCL mechanisms: (a) ESA, (b) ETU, (c) C...
Figure 2.4 Schematic illustration of typical QC mechanisms.
Figure 2.5 Schematic representation illustrates the disruption of crystallog...
Figure 2.6 (a,b) The PAET process in NaErF
4
@NaYF
4
NPs occurs at high tempera...
Figure 2.7 Schematic illustrations of dye-sensitized enhanced luminescence o...
Figure 2.8 Schematic of different ESA mechanisms upon dual-wavelength excita...
Figure 2.9 (a) Schematic diagram of STED microscope. (b) Low-doped Tm (1%) a...
Figure 2.10 A simplified energy level diagram illustrating the splitting of ...
Figure 2.11 Effect of external magnetic field on the green UCL of NaGdF
4
: Nd...
Figure 2.12 The tetragonal lattice of Er-doped BTO films (a) without and (b)...
Figure 2.13 (a) The UCL spectra of the BTO:Yb/Er film under different DC bia...
Figure 2.14 (a) Diagrammatic representation of Cu
2−
x
S-MoO
3
-NaYF
4
:Yb
3+
...
Chapter 3
Figure 3.1 UCL mechanisms of (a) excited state absorption (ESA), (b) photon ...
Figure 3.2 Lanthanide-doped imaging probe based on ESA.
Figure 3.3 Multilayer core–shell nanostructure based on ET.
Figure 3.4 The highest intensity, spectra, and optimization results of each ...
Figure 3.5 Intensities of 340 phosphors doping with (a) Ce
3+
and (b) Tb
3
...
Figure 3.6 (a) Size variation against the concentration of Y
3+
. (b) Size...
Figure 3.7 Schematic illustration of the preparation and functional diagram ...
Figure 3.8 Synthesis and application of UCNPs@mSiO
2
-Au-Cys nanomotors for na...
Figure 3.9 Photoactivatable immunodevice through the integration of UCNPs wi...
Figure 3.10 Schematic illustration of the NIR light-activatable multifunctio...
Chapter 4
Figure 4.1 Schematic illustration of the formation process of the upconversi...
Figure 4.2 (a) Schematic diagram for synthesizing H-USH. (b–d) Transmission ...
Figure 4.3 Schematic illustration of heterogeneous nucleation and Ostwald ri...
Figure 4.4 (a) Schematic illustration of the synthesis of upconversion nanop...
Figure 4.5 (a) Schematic illustration of the fabrication of upconversion nan...
Figure 4.6 (a) Illustration of the composite synthesized with bare upconvers...
Figure 4.7 (a) Illustration of self-assembled MOF-upconversion nanoparticle ...
Figure 4.8 Illustration of the preparation and PDT process of the UCNM-MOF-T...
Figure 4.9 (a) Cell viability of 4T1 cells with different treatments (Data: ...
Figure 4.10 (a) Schematic Illustration of antitumor mechanism of the Janus U...
Figure 4.11 Dual-mode targeted imaging based on the NaYF
4
:Yb/Er@Fe-MIL-101-N...
Figure 4.12 (a) Schematic diagram of H
2
S detection by the triple-signal sens...
Chapter 5
Figure 5.1 Observed energy levels of the rare earth ions. The thickness of e...
Figure 5.2 Energy diagram showing the processes for downshifting and upconve...
Figure 5.3 Schematic diagrams indicating concentration quenching and cross-r...
Figure 5.4 The light absorption spectra of water within (a) 700–1700 nm and ...
Figure 5.5 Schematic diagrams of the ET process in bioprobe design. The term...
Figure 5.6 (a) Simplified energy scheme of the Nd
3+
and Yb
3+
emittin...
Figure 5.7 (a) Upconversion emission signals decoding of UCNPs using time-re...
Figure 5.8 (a) Overlaid spectra of the upconversion luminescence of the UCNP...
Figure 5.9 (a) TEM images of pyramids assembled with Au NPs and UCNPs in 10 ...
Figure 5.10 Schematic illustration of the preparation of (a) LLD and (b) upc...
Figure 5.11 Working principle of the activatable DNA nanodevice for NIR ligh...
Figure 5.12 Scheme for detection of AFP and mucin-1 based on Au-Au-UCNP-trim...
Figure 5.13 Schematic representation of (a) conventional DELFIA immunoassay ...
Figure 5.14 (a) Energy-level diagram illustrating the luminescence process o...
Figure 5.15 (a) Scheme of the designed composite probe Er-CSSNPs@Cy925. The ...
Figure 5.16 Schematic illustration showing the ratiometric response of DSNP@...
Figure 5.17 (a) Energy transfer mechanism in the NaErF
4
:2 %Ho@NaYF
4
core–she...
Figure 5.18 (a) Scheme of the ONOO
−
-responsive nanosensor DSNP@MY-1057...
Figure 5.19 Schematic illustration of household fluorescent LFS platform. Th...
Figure 5.20 Design of a swallowable multimodal X-ray dosimeter. (a) The dosi...
Chapter 6
Figure 6.1 Rare earth-based nanovectors for gene delivery.
Figure 6.2 Schematic illustration of silica-coated UNCPs nanovector for deli...
Figure 6.3 Schematic illustration of a NIR activated UCNP-based gene editing...
Figure 6.4 Schematic illustration of UCNP-peptide-AIEgen nanoprobe for the d...
Figure 6.5 Schematic illustration of upconversion superballs for programmabl...
Figure 6.6 Schematic illustration of UCNP-cy-siRNA for programmed delivery o...
Chapter 7
Figure 7.1 The SK-BR-3 cells absorb 20 nm UCNP particles. The upper row depi...
Figure 7.2 The behavior of subcutaneously injected cit-UCNPs for 30 minutes....
Figure 7.3 Fluorescence imaging (a,b,c) was performed before and (d,e,f) thr...
Figure 7.4 The UCL imaging of mice was conducted following the intravenous i...
Figure 7.5 Confocal microscope images of zebrafish injected with PEG-UCNPs. ...
Figure 7.6 SPECT/CT imaging of Kunming mice after feeding 153 Sm-labeled cit...
Chapter 8
Figure 8.1 Simplified Jablonski diagram illustrating the photophysical and p...
Figure 8.2 Porphyrin photosensitizers. (a) Chemical structures of convention...
Figure 8.3 Phthalocyanine photosensitizers. (a) Synthetic schematic diagram ...
Figure 8.4 (a) Illustration of metallacycle-based supramolecular PSs with tw...
Figure 8.5 (a) Illustration of PCN-224 structure. 6-connected Zr6 cluster (Z...
Figure 8.6 (a) Schematic illustration of the C
3
N
4
-mediated water splitting p...
Figure 8.7 Schematic illustration of PDT with a Trojan-horse-like approach....
Figure 8.8 (a) Fabrication and photosynthesis-promoted PDT schematics of Cya...
Figure 8.9 (A) Schematic illustration, XRD patterns, and TEM images of the s...
Figure 8.10 (a) Synthesis illustration and schematic depiction of UCNP-Ce6/A...
Chapter 9
Figure 9.1 (a) Semantics of energy-level model of deep trap persistent lumin...
Figure 9.2 (a) Persistent luminescent spectra of the NaYF
4
:Tb
3+
@NaYF
4
(T...
Figure 9.3 (a) Photographs of a PMMA-polymer film containing 40 wt% CsCdCl
3
:...
Figure 9.4 Schematics of light-storage-based TTIs. The release of trapped ca...
Figure 9.5 (a) Photographs and grayscale images of LFPs deposited on glass b...
Figure 9.6 (a) Trial-and-error method for discovering Persistent luminescent...
Figure 9.7 Stacked vacuum referred binding energy (VRBE) diagrams of Y
3
Al
5−x
...
Figure 9.8 (a) Photographs of the Y
3
Al
2
Ga
3
O
12
:Pr
3+
transparent ceramic s...
Figure 9.9 HRBE (left ordinate) and VRBE (right ordinate) schemes of Ln
2+
...
Chapter 10
Figure 10.1 The bandgap of QDs becomes narrower with the increase in size, a...
Figure 10.2 Schematic diagram of thermal injection methods and nucleation an...
Figure 10.3 Schematic illustration of fluoroimmunoassay for IL-6 with aqueou...
Figure 10.4 Schematic diagram of metabolic regulation of selenium and cadmiu...
Figure 10.5 Comparison of fluorescence intensity before and after alloying A...
Figure 10.6 Types of core–shell QDs.
Figure 10.7 Illustration of AgInS
2
QDs-based fluorescence probe for dopamine...
Figure 10.8 Schematic diagram of CYFRA21-1 DNA detection based on hybrid cha...
Figure 10.9 Nuclear antigen detection and double labeling. (a) Nuclear antig...
Figure 10.10 Schematic illustration of the nanobioprobe preparation and appl...
Figure 10.11 Schematic illustration of CuInSe
2
/ZnS nanoprobes for circulatin...
Figure 10.12 Scheme of “all-in-one” CuInS/ZnS QDs.
Figure 10.13 Schematic illustration of synthesis route of nanomedicine, tumo...
Figure 10.14 Schematic depiction of the assembling process and targeting tum...
Figure 10.15 The preparation of AgInS
2
@BSA@ZIF-67 nanocomposites and schemat...
Figure 10.16 The preparation of nanovaccines and the imaging of the traffick...
Chapter 11
Figure 11.1 Molecular mechanism of pyroptosis. In the canonical pathway, PAM...
Figure 11.2 Pyroptosis is an inflammatory form of cell death triggered by in...
Figure 11.3 (a) Cartoon of the experimental design. Purified GSDMA3(N + C) w...
Figure 11.4 Bioactive nanomaterials for ion interference antitumor therapy....
Figure 11.5 Illustration of therapeutic mechanism of Na
2
S
2
O
8
nanoparticles....
Figure 11.6 Uptake of Lip-MOF nanoparticles leads to pyroptosis of cells in ...
Figure 11.7 Biodegradable Ca
2+
nanomodulators as the pyroptosis inducers...
Figure 11.8 Schematic illustration of the fabrication and mechanism to induc...
Figure 11.9 Schematic illustration of the fabrication and mechanism of sodiu...
Figure 11.10 Schematic illustration of CCNP for antitumor immune response by...
Figure 11.11 DFNA5 is downregulated in tumor cells of breast cancer (BRCA) a...
Figure 11.12 Schematic illustration for the construction of the lipo-(PpIX/C...
Figure 11.13 (a) Schematic illustration of the ROS-responsive GOD-loaded the...
Figure 11.14 Illustration of the material synthesis and therapeutic process....
Chapter 12
Figure 12.1 Different mechanisms of the photothermal effect.
Figure 12.2 (a) Schematic illustration of the typical wetting and nonwetting...
Figure 12.3 (a) Schematic illustrations for the fabrication of Au
2
Pt-PEG-Ce6...
Figure 12.4 Schematic illustration of the preparation process and action mec...
Figure 12.5 Schematic illustration of preparation of MoSe
2
/CoSe
2
nanosheets ...
Figure 12.6 (a) Schematic illustration of synthesis and therapeutic procedur...
Figure 12.7 Characteristics of ICD.
Figure 12.8 PTT generates ICD when an optimal thermal dose is administered t...
Figure 12.9 The Cells in the TME.
Figure 12.10 The hypothesized mechanism of antitumor immune responses induce...
Figure 12.11 Schematic illustration of fabrication and mechanism of PEGylate...
Figure 12.12 (a) Schematic diagram of CoFe
2
O
4
@MnFe
2
O
4
nanoparticles. (b) The...
Figure 12.13 Schematic presentation of synergistic cancer therapy mechanism ...
Figure 12.14 (a) Schematic illustration of FePSe
3
@APP@CCM. (b) Tumor growth ...
Figure 12.15 (a) Schematic diagram of PdPtCu nanozymes-mediated combination ...
Figure 12.16 Schematic diagram of combined photothermal and immunotherapy us...
Figure 12.17 Schematic illustration of (a) fabrication of the MoS
2
-CuO@BSA/R...
Figure 12.18 Schematic diagram of AuNSP@αCD16-mediated TME modulation for ro...
Figure 12.19 Schematic illustration and characterization of BPQD-CCNVs combi...
Chapter 13
Figure 13.1 The antibacterial mechanisms of photofunctional antibacterial na...
Figure 13.2 The structure of porphyrin derivatives and antibacterial effects...
Figure 13.3 The structure of phthalocyanines derivatives and antibacterial e...
Figure 13.4 The semiconductor NPs and antibacterial effects. (a) antibacteri...
Figure 13.5 Antibacterial effects of QDs related materials. (a) and the surv...
Figure 13.6 The structure of phthalocyanines derivatives and antibacterial e...
Chapter 14
Figure 14.1 Diagram of typical photoelectrochemical biosensing system.
Figure 14.2 Schematic illustration of the basic principles of RCA. (a) Makin...
Figure 14.3 (a–c) Fundamentals of HCR. The initiator (I) triggers a chain hy...
Figure 14.4 (a) Schematic diagram of the formation of 3D CdSe QDs-DNA nanone...
Figure 14.5 (a) In situ synthesis of a porous COP onto an ITO glass substrat...
Figure 14.6 Principle of the energy transfer-based photoelectrochemical sens...
Figure 14.7 Scheme of electron transfer in different status: in the presence...
Figure 14.8 Fabrication process of the photoelectrochemical immunosensor....
Figure 14.9 Schematic illustration of the fabrication of Pt NCs-cystine-TMNT...
Figure 14.10 (a) Photoelectrochemical detection mechanism of glucose by CDs/...
Figure 14.11 Overview of photoelectrochemical biosensor array platform. (a) ...
Figure 14.12 Illustration of the proposed photoelectrochemical biosensor for...
Chapter 15
Figure 15.1 General mechanism of indirect excitation of X-PDT.
Figure 15.2 Schematic Illustration of SSCP with (a) tunable structural and (...
Figure 15.3 Schematic illustration of the working mechanism of X-PDT (a) and...
Figure 15.4 Schematic illustration of the Gd-containing polyoxometalates-con...
Figure 15.5 (a) Transmission electron microscope (TEM) micrograph of NaLuF
4
:...
Figure 15.6 (a) Schematic representation of X-ray-induced luminescence of en...
Figure 15.7 (a) Schematic illustration of fabrication and modification of Hf...
Figure 15.8 Left: Schematic showing the synthesis, morphologies, and topolog...
Figure 15.9 (a) Process to prepare organic nanoparticles in aqueous solution...
Figure 15.10 Rational design and application of PLGA-SS-D@BPQDs to tumor rad...
Figure 15.11 Diagram illustrating the preparation and mechanisms of X-PDT us...
Figure 15.12 Schematic illustration of X-ray-activated PLNP-mediated PDT nan...
Figure 15.13 Schematic illustration of TBDCR NPs structure and preparation f...
Figure 15.14 (a) Mechanism of NaGdF
4
:Eu
3+
@SiO
2
-S-nitrosothiol (SNO)/indo...
Figure 15.15 Schematic illustration of the synthetic route to RBS-T-SCNPs an...
Figure 15.16 Schematic illustrations of the process of the preparation of RG...
Figure 15.17 Schematic illustration of nano-bio therapeutic emulsion formula...
Guide
Cover
Table of Contents
Title Page
Copyright
Foreword
Preface
Acknowledgments
Begin Reading
Index
End User License Agreement
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Photofunctional Nanomaterials for Biomedical Applications
Edited byChunxia Li and Jun Lin
Editors
Prof. Chunxia LiShandong University72 Binhai Road266237 QingdaoChina
Prof. Jun LinChangchun Institute of AppliedChemistry, Chinese Academy of Sciences,5625 Renmin Street130022 ChangchunChina
Cover Image: © LAGUNA DESIGN/Getty Images
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Foreword
According to the data by the International Agency for Research on Cancer of the World Health Organization, the global incidence rate of cancer can potentially escalate to 29.5 million by 2040. Even in the present era, cancer continues to persist as a prominent contributor to the deaths of humans worldwide. Tumor metastasis, as the leading factor, accounts for approximately 90% of cancer-related fatalities. In fact, metastasis may occur even at the time of cancer diagnosis for a number of patients. Importantly, plenty of individuals afflicted with lung cancer exhibit metastatic disease, as evidenced by an over 80% diagnosis rate. Furthermore, recent research have revealed the presence of diverse bacteria within the majority of solid tumors, which has been evidenced to be responsible for tumor metastasis and colonization. The current prevailing treatment modalities, such as chemotherapy, hormonal therapy, and radiation therapy, have achieved significant progress in treating metastatic cancer and prolonging the survival of patients to certain extents; unfortunately, the overall therapeutic efficacy remains unsatisfactory.
The advancements in nanotechnology have aroused significant progress or even breakthroughs in the biomedical fields. Photofunctional nanomaterials, being a novel class of light-responsive materials, have gained extensive attention and utilization. For example, they as carriers can achieve targeted drug delivery and controlled release, resulting in the enhanced efficacy of medications. After ingenious modifications with functional molecules, such as photosensitizers, photothermal agents, chemotherapeutic drugs, and gene composites, photofunctional nanomaterials exhibit great potential for advancing various therapeutic modalities such as photodynamic therapy, photothermal therapy, chemotherapy, antibacterial therapy, gene therapy, and biosensing. Moreover, these nanomaterials also enable simultaneous image-guided multi-modal therapy. Therefore, photofunctional nanomaterials hold immense promise in the biomedical fields.
Based on this, in this book, Professor Chunxia Li, Professor Jun Lin, and their collaborators have reviewed and summarized recent research progress on photofunctional nanomaterials for biomedical fields in a comprehensive and well-organized manner. Impressively, the authors have elucidated the underlying functioning mechanisms of these nanomaterials in depth and extensively discussed the challenges encountered by photofunctional nanomaterials along with their future development prospects. This book offers researchers in the nanomedicine field a highly methodical and professional compendium and reference summarizing the application of photofunctional nanomaterials in a broad spectrum.
Finally, it is anticipated that this publication will greatly benefit further advancements in the research and applications of photofunctional nanomaterials and establish a robust groundwork for the future clinical translation.
January 30, 2024
Prof. Jianlin Shi
State Key Laboratory of High PerformanceCeramics and Superfine MicrostructureShanghai Institute of CeramicsChinese Academy of SciencesShanghai, China
Preface
In recent years, morbidity and mortality of cancer have obviously increased; therefore, cancer has become a serious threat to human health. Thus, how to provide new clues to prewarning and early diagnosis and therapy of cancer is highly demanded. To achieve this goal, the new material chemistry is essential because the nanoparticles have to be uniform and tunable in terms of physical properties such as size, shape, and surface. Photofunctional nanomaterials are light-driven functional materials that can effectively convert and utilize light energy, an inexhaustible source of clean and renewable energy. Especially, near-infrared (NIR) light is a highly accurate non-physical and non-invasive external stimulation method that has the unique advantages of high penetration depth and low fluorescence background interference, achieving synchronous control of time and space. Therefore, the light can be utilized to achieve controllable chemotherapy or photodynamic therapy (PDT). Photothermal nanomaterials can convert light energy into heat energy, resulting in local overheating and tumor ablation (photothermal therapy, PTT). Therefore, the design and applications of photofunctional nanocomposites are an important branch of biomedical functional materials and have become the frontier research direction in interdisciplinary fields.
This book will focus on providing researchers and graduate/undergraduate students in interdisciplinary fields including chemistry, materials science, and biomedicine, highlighting their full potential in biomedical applications including tumor diagnosis and therapy, photogenetically engineered bacteria, optical information storage, and biosensing.
Chapter 1 demonstrates a basic introduction and classification of photofunctional nanomaterials as well as their applications in biomedical fields.
From Chapters 2–7, the rare earth luminescence nanomaterials are systematically introduced, mainly shedding light on their luminescence mechanism, multiform luminescence modulation, construction of composites, and the corresponding applications in gene delivery as well as the biosafety evaluation.
Chapter 8 provides an overview of photosensitizers for PDT. The basic principles of PDT, classifications of various photosensitizers, and the mechanisms during treatment are outlined.
Chapter 9 introduces the persistent luminescent materials for optical information storage applications. And the design of ternary quantum dots and their application in tumor-related marker detection, imaging, and therapy are mentioned in Chapter 10.
Chapter 11 summarizes nanomaterial-induced pyroptosis and immunotherapy including pyroptosis pathways and the potential for immunotherapy, especially in activating effector T cells and promoting dendritic cell maturation.
Chapter 12 mainly highlights the latest developments of inorganic nanomaterials in PTT. The mechanism and application of nanomaterial-based PTT against cancer by photothermal immunotherapy are also expounded.
Chapter 13 begins by presenting an overview of the antibacterial mechanisms inherent in photofunctional antibacterial nanomaterials, focusing on the approaches developed to overcome resistance in multidrug-resistant (MDR) pathogens and the prominent challenges in the field of photofunctional antibacterial nanomaterials.
Chapter 14 focuses on the applications of photoelectrochemicals nanomaterials in biosensing.
Chapter 15 describes the concept of X-ray-activated PDT, outlines the interaction mechanisms between X-rays and nanosystems, and introduces the application of X-ray-activated nanosystems in photodynamic therapy for deep-seated tumors.
And, the last chapter, Chapter 16, introduces the perspectives on the opportunities and potential benefits of photofunctional nanomaterials for biomedicine.
Finally, we greatly acknowledge the substantial contribution from Prof. Hongjie Zhang, Prof. Rongjun Xie, Prof. Yulei Chang, Prof. Ruichan Lv, Prof. Xiaoji Xie, Prof. Renren Deng, Prof. Tao Zhang, Prof. Guanying Chen, Prof. Jing Feng, Prof. Yixi Zhuang, Prof. Ziyong Cheng, Prof. Bingbing Ding, Prof. Ping’an Ma, Prof. Zhiyao Hou, Prof. Biao Dong, Prof. Lin Wang, Prof. Piaoping Yang, Prof. Jinliang Liu, and Dr. Qianqian Sun to this book.
26 January 2024Qingdao, China
Professor Chunxia Li
Shandong University, Qingdao, China
Professor Jun Lin
Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,Changchun, China
Acknowledgments
We greatly acknowledge the substantial contribution from Prof. Hongjie Zhang, Prof. Rongjun Xie, Prof. Yulei Chang, Prof. Ruichan Lv, Prof. Xiaoji Xie, Prof. Renren Deng, Prof. Tao Zhang, Prof. Guanying Chen, Prof. Jing Feng, Prof. Yixi Zhuang, Prof. Ziyong Cheng, Prof. Ping’an Ma, Prof. Zhiyao Hou, Prof. Biao Dong, Prof. Lin Wang, Prof. Piaoping Yang, Prof. Jinliang Liu, and Dr. Qianqian Sun to this book.
1General Introduction and Background of Photofunctional Nanomaterials in Biomedical Applications
Chunxia Li1 and Jun Lin2
1Shandong University, School of Chemistry and Chemical Engineering, Institute of Frontier Chemistry, Binhai Road, Qingdao 266237, P.R. China
2Chinese Academy of Sciences, Changchun Institute of Applied Chemistry, State Key Laboratory of Rare Earth Resource Utilization, Renmin Avenue, Changchun 130022, P.R. China
1.1 Introduction to Nanomaterials
From the perspective of human history, the history of human knowledge of the world is the history of the development of scale and materials. With the continuous development of science and technology, human cognition of the world has long exceeded the single macroscopic world, and the emergence of nanotechnology in 1984 has directly brought human beings into an infinite and mysterious “small size, big world.” Therefore, as an important tool for human beings to explore the microscopic world, the research and application of nanomaterials have been widely valued by many disciplines in recent years [1].
Nanomaterials are materials that have at least one dimension in three-dimensional space in the nanoscale range (1–100 nm, 1 nm = 10−9 m) or are composed of them as basic units [2, 3] and are known as “the most promising materials of the 21st century.” As research progresses, scientists are gradually discovering that materials with dimensions at the nanoscale can exhibit unique properties that are superior to those of conventional materials in terms of physics, chemistry, optics, thermodynamics, and magnetism [4–6]. This is because the ratio of the number of atoms on the surface of nanomaterials to the total number of atoms increases dramatically as the particle size decreases. The special properties of nanomaterials are as follows.
1.1.1 Surface and Interfacial Effects
When the size of a material is reduced to the nanoscale, the number of surface atoms, the surface area, and the surface energy increase dramatically, and at the same time, a large number of unsaturated bonds, dangling bonds, and active centers appear in nanomaterials, and the surface defects of the material also increase. These defects introduce many surface states in the energy barrier band gap, which become traps for electrons or holes, seriously affecting the optical, photoelectrochemical, and nonlinear optical properties of the materials [7–10]. Therefore, many new properties of nanomaterials are inextricably linked to their surface and interfacial effects.
1.1.2 Small Size Effect
When the size of the material is comparable to or smaller than physical quantities, such as the wavelength of light waves (less than 100 nm), the radius of exciton bands of De Broglie wavelengths (1–10 nm), or the coherence length of superconductivity, the periodic boundary conditions of the internal crystals will be disrupted, and the density of atoms near the surface layer of the particles of amorphous nanoparticles will be reduced. This will lead to significant changes in the macroscopic physical and chemical properties (such as sound, light, electricity, magnetism, heat, and mechanics) of the nanomaterials [11–14].
1.1.3 Quantum Size Effect
When the size of the material is reduced to the nanometer scale, the electronic energy levels near the metallic Fermi energy level change from continuous to discrete, and the continuous energy band, valence band, and conduction band of semiconductors become discrete energy level structures, and the bandgap broadening phenomenon is called the quantum size effect [15–18]. When the energy level spacing is greater than the thermal, magnetic, electrostatic, photonic, or superconducting condensation energy, nanomaterials will exhibit a range of properties that are very different from those of bulk materials.
1.1.4 Macroscopic Quantum Tunneling Effects
When the scale of a material enters the nanometer range, certain macroscopic quantities of nanoparticles (such as particle magnetization intensity, magnetic flux in quantum coherent devices, and electric charge) exhibit tunneling effects that can cross the potential barriers of the macroscopic system and produce changes, known as macroscopic quantum tunneling effect [19–22]. Macroscopic quantum tunneling is the theoretical basis for future microelectronic and optoelectronic devices.
Because of the special properties mentioned above, nanomaterials have many more excellent physicochemical properties than macroscopic materials. Physically, nanomaterials have good electrical conductivity, dielectricity, magnetism, and mechanical properties. From a chemical point of view, nanomaterials are highly active on the surface and are particularly prone to adsorbing other atoms or chemically reacting with other atoms, which greatly improves the catalytic ability of the reaction. As a result, nanomaterials have broad application prospects in many fields such as optoelectronics, environmental science, and biomedicine.
1.2 Introduction and Classification of Photofunctional Nanomaterials
The development and application of materials are a sign of the progress of time and human civilization. The history of materials is as long as the history of mankind. Mankind has gone through a long period of Stone Age, Bronze Age, and Iron Age. Nowadays, with the continuous improvement of nanomaterial synthesis technology, research on nanomaterials has gradually shifted to refinement and functionalization. At the same time, with the growing demand for material functions in science and technology and living standards, as well as the cross-fertilization of the frontiers of various disciplines, a wide range of functionalized nanomaterials have emerged.
Functionalized nanomaterials are diverse and wide-ranging, and there are many ways to classify them. Functional nanomaterials can be classified into electrical nanomaterials, magnetic nanomaterials, optical nanomaterials, thermal nanomaterials, acoustic nanomaterials, chemical nanomaterials, invisible nanomaterials, and so on according to their performance, which is spectacular, and a large number of new functional nanomaterials have been introduced every year. Among them, a series of nanomaterials with unique optical properties (light-functional nanomaterials) have been successfully prepared [23–28], which has become one of the hotspots in the field of functionalized nanomaterials in recent years and has been widely applied in many fields, such as bioanalysis and sensing, illumination and display, environmental monitoring and purification, energy conversion and storage, biomedicine, anticounterfeiting, and information.
In fact, the understanding of optical phenomena in nature has a long history, and it can be said that human beings have progressed along with the knowledge of optical phenomena in nature. For example, fire is man’s first perception of light, without which human society would not have survived. The propagation and absorption of light profoundly affect all aspects of nature, and without the phenomena of selective absorption, scattering, transmission, and reflection of light by matter, there would be no colors, no heat, no energy transformed by light, and no production of all biomass in nature. Photofunctional nanomaterials are light-driven functional materials that can effectively convert and utilize light energy, an inexhaustible source of clean and renewable energy. To date, the applications of photofunctional nanomaterials are very diverse, but essentially, the same physical and chemical processes take place and follow similar laws, including photon capture, photon absorption and utilization (conversion), and physicochemical processes at the surface interface [29].
1.2.1 Capture of Photons
Light has a fluctuating and particle duality (wave-particle duality), and when considering the energy conversion between light and electrons, light is treated as a particle called a photon. The trapping of photons is the first step in the process of light conversion and utilization by photofunctional nanomaterials, and the more photons that are trapped, the greater the chance that they will be absorbed. It can also be assumed that the photon trapping ability of a material determines the upper limit of its light conversion efficiency. In general, the photon trapping capability of photofunctional nanomaterials can be increased in three directions: broadening the absorption spectral range of the material, reducing the loss of light after it has passed through the material, and increasing the optical range of light in the material.
1.2.2 Absorption and Conversion of Photons
In addition to trapping as many photons as possible, photofunctional nanomaterials must have the ability to absorb and convert the trapped photons into phonon vibrations, photogenerated electron-hole pairs, or other energies. When light is shone on a material, various physicochemical effects such as photothermal effect, photoluminescence, photoelectric effect, and photochemical effect, are produced due to electromagnetic vibrations of electromagnetic waves or inelastic collisions of photons.
Among them, the photothermal effect refers to the fact that photothermal materials, after absorbing the energy of light radiation, do not directly cause a change in the internal electronic state but convert the absorbed light energy into the vibration of the crystal point structure (which means the production of phonons), thus causing a temperature rise and the generation of thermal energy [30]. As the research progressed, it was found that the photothermal effect of photofunctional nanomaterials depends not only on the incident light but also on the absorption spectrum of the material itself. Materials are dense systems consisting of a large number of atoms and molecules, and thermal energy is the average kinetic energy of the irregular motion of these particles. In other words, the accelerated motion of atoms and molecules at the microscopic level corresponds exactly to the increased temperature of the material at the macroscopic level (known as heating). The characteristic frequencies of the continuous relative vibrations and rotations of the atoms and molecules in the material are similar to those of infrared light, so they can resonate with external infrared light. Therefore, when a material is irradiated with infrared light, the motion of the atoms and molecules of the material will be enhanced, and a large amount of heat will be emitted. In contrast, the material absorbs less blue-violet light, resulting in less heat generation and a poorer thermal effect.
Photoluminescence is the process by which a material absorbs photons and then re-radiates them [31]. When the material is irradiated with light of a certain wavelength, the electrons in the ground state of the material (mainly π electrons and f and d electrons) are excited to a high-energy state, and when the external light stops, the electrons in the excited state will jump back to the ground state. In the process of the electron jump, some of the energy is emitted in the form of photons to accomplish the purpose of the light. Photoluminescence can be divided into two categories according to the delay time: fluorescence and phosphorescence [32]. Fluorescence is the emission of photons immediately after the substance is excited, and the luminescence time is ≤10−8 seconds. Phosphorescence can continue to emit light for a long time, and usually, the luminescence time is ≥10−8 seconds. According to light excitation and emission, photoluminescent nanomaterials can be classified into upconversion luminescence or downconversion luminescence nanomaterials according to the nature of their light emission. Among them, upconversion luminescence is a photoluminescence phenomenon that violates Stokes’ law, which is manifested by the conversion of several low-energy (long-wavelength) photons into one high-energy (short-wavelength) photon [33]. Downconversion luminescence is a photoluminescence phenomenon that obeys Stokes’ law and is manifested by the conversion of a high-energy photon into one or more low-energy photons [34]. When one low-energy photon is emitted, it is commonly referred to as luminescence, and when two or more low-energy photons are emitted, it is referred to as quantum clipping of luminescence.
Photoelectric effect, which is the electrical effect of light, refers to the material in the light of the phenomenon of emission of electrons, the essence of photon excitation material to produce electrons and hole pairs; electrons migrate into the external circuit to do work, manifested as electrical energy [35]. Photochemical effect is the chemical effect of light, which refers to the material used in the photon excitation to produce electrons and hole pairs. They were with the reactant redox reaction, stored as chemical energy phenomenon [36].
1.2.3 Physical-chemical Processes at the Surface Interface
The physical processes at the surface interface of photofunctional nanomaterials mainly involve thermal radiation dissipation and relaxation quenching of photogenerated photons. In photothermal materials, by controlling the composition and structure of the nanomaterials, the radiation angle coefficients of the materials can be effectively reduced, thereby reducing the dissipation of thermal energy and improving the utilization of photothermal conversion energy. In luminescent materials, photons generated by photoluminescence can be recaptured by the material and achieve relaxation by nonradiative bonding, thus reducing the luminescence effect. In semiconductor nanomaterials, photoelectrons migrate to the surface of the material and return to the interior of the material to recombine with holes after work is done by the external circuit, achieving the conversion of light energy into electrical energy.
Surface interface chemical reactions of photofunctional nanomaterials usually occur during photocatalysis of the materials. Photogenerated electrons and holes migrate to the surface or interface of the material and combine with electron acceptors or donors adsorbed on the surface of the photocatalytic material to undergo a redox reaction, storing the energy in the chemical bonds of the products and realizing the conversion of light energy into chemical energy. The detailed process of the chemical reaction at the surface interface roughly involves the following processes. First, the reactants must diffuse around the material and pass through the Helmholtz layer to be adsorbed onto the active sites of the material. Next, the reactants undergo structural rearrangement at the active site and undergo redox reactions with photogenerated electron holes. Finally, the reaction products desorb from the surface of the material and return to the reaction solution. In the whole process, a series of elementary reactions such as adsorption of reactants, charge exchange, and desorption of products together constitute the whole interfacial reaction process.
1.3 Introduction to Nanobiomedicine
In recent years, nanomaterials have been gradually integrated with biology and medicine in the development process, gradually forming a new discipline, namely “nanobiomedicine” (Figure 1.1) [38, 39]. Some people call the cooperation between nanomaterials and biomedicine “a great change” because it not only opens the door for nanobiology and nanomedicine but also brings new opportunities for biomedical research and clinical application. Governments around the world have increased the investment of funds and personnel in nanomedicine research, and nanobiomedicine has rapidly become a frontier and hot topic in the development of the biotechnology field in various countries, attracting more and more attention and expectations.
To be more precise, nanobiomedicine is an emerging discipline that applies nanomaterials to biomedical field, which involves materials science, physics, chemistry, biology, medicine, quantum science, and many other fields, and has very distinctive multidisciplinary cross characteristics. The research directions of nanobiomedicine include but are not limited to drug delivery and release [40–42], bioimaging [43], diagnosis and treatment of diseases (especially tumors) [44, 45], biosensing [46, 47], tissue engineering, and so on [48–50].
1.3.1 Nano-drug Delivery Systems
Through the design and preparation of nanocarriers such as nanoparticles, nanocapsules, nanofibers, and drugs are encapsulated in nanoscale structures to achieve precise drug delivery and release. Such nano-drug delivery systems can improve drug bioavailability, reduce side effects, and enable targeted therapy.
1.3.2 Nano-imaging Technology
High-resolution nano-imaging technology has been developed by exploiting the special optical, magnetic, and acoustic properties of nanomaterials. For example, nanoparticles can be used as contrast agents for fluorescence imaging, magnetic resonance imaging (MRI), and photoacoustic imaging (PAI) to achieve accurate imaging of biological tissues and lesions.
1.3.3 Nano-diagnostic Technologies
By exploiting the special properties of nanomaterials, nano-diagnostic technologies have been developed for biomarker detection, early diagnosis of diseases, and prognostic assessment. For example, nanoprobes can be used to detect the presence and activity state of specific molecules, enabling highly sensitive and selective diagnosis.
Figure 1.1 Inorganic light-responsive nanomaterials have been widely applied to four main research fields of light-responsive biomaterials, which consist of PTT and PDT, light-guided devices for remote actuation and drug delivery, nongenetically optical modulation of cells, and dynamic biomaterials for regenerative medicine.
Source: [51]/John Wiley & Sons/CC by 4.0.
1.3.4 Nanotherapeutic Technology
Using the special properties of nanomaterials, therapeutic methods have been developed for thermotherapy, phototherapy, drug release, and other therapeutic methods. For example, thermal therapy for tumors can be achieved by absorbing light energy from nanomaterials to produce thermal effects or by using nanoparticles with specific responsiveness to achieve targeted drug release.
1.3.5 Nano-biosensors
Using the special properties of nanomaterials and biorecognition molecules, nano-biosensors have been developed to monitor biomolecules, cellular activities, and biological processes. These sensors can monitor physiological and pathological changes in organisms in real time and provide timely diagnostic and therapeutic feedback.
1.3.6 Tissue Engineering
Nanotechnology can be used to create materials such as scaffolds, nanoparticles, and nanofibers with nanoscale structures to support and guide cell growth and differentiation. These nanomaterials can mimic the microstructure of human tissues and provide a suitable physical and chemical environment to promote cell adhesion, proliferation, and differentiation. In addition, nanotechnology can be used to prepare nanocarriers with controlled drug release to enhance the therapeutic efficacy of tissue-engineered constructs.
At present, nanobiomedicine has become an important direction in the development of nanotechnology, and its booming momentum will continue to provide new technologies and methods for modern biomedical research, open up new horizons for important biomedical problems at the nanoscale, and reveal the relevant new principles and possible practical applications.
In the biomedical field, the choice of light has unique requirements. As a common external stimulus with the advantages of noninvasiveness, high spatial and temporal resolution, and spatial and temporal controllability (including controllable light intensity and wavelength), light sources play an important role in biology and medicine [37, 51] and can induce organisms to perform or regulate many specific biological processes at a given site, such as gene transfection, cell function, signaling, ion channel opening, protein activity, molecular isolation, and tissue regeneration (Figure 1.2) [52]. However, most current photosensitive components respond only to ultraviolet or visible light, so the use of light as an excitation source for biomedical applications is subject to certain dilemmas that jeopardize its potential applications; for example, ultraviolet or visible light is readily absorbed and scattered in living tissues and has a very shallow tissue penetration depth [53, 54]. In addition, ultraviolet is phototoxic and is likely to damage biomolecules such as nucleic acids, proteins, and lipids. These issues need to be addressed from two perspectives. On the one hand, since biological tissues cannot efficiently absorb near-infrared (NIR) light themselves, NIR light sources with lower tissue absorption, less light scattering, and deeper tissue penetration should be used to replace ultraviolet and visible light for biomedical research and applications [55]. On the other hand, there is a need to actively research and develop photofunctional nanomaterials or devices that can absorb NIR light and convert it into the desired signal or energy.
Figure 1.2 Summary of photoactive nanomaterials for regulation of biomolecules, neurons, and nerve tissues.
Source: Reproduced with permission from Ref. [52]; © 2022/American Chemical Society.
1.4 Classification of Photofunctional Nanomaterials
At this point, it should be stated in advance that due to the wide range of photofunctional nanomaterials, it is impossible to study them in detail one by one. Therefore, in connection with the theme of this book-“Photofunctional nanomaterials for biomedical applications,” we will discuss the fluorescent, photothermal, photodynamic, photoelectrochemical, and photoacoustic parts of photofunctional nanomaterials and their research in biomedical fields such as biodetection [56], optogenetics [57], antibacterial [46], tumor diagnosis and treatment [45, 58], and other biomedical fields.
1.4.1 Fluorescent Nanomaterials
Fluorescent nanomaterials are nanoscale materials with special optical properties that absorb light energy at specific wavelengths and emit fluorescence at specific wavelengths. Compared with traditional organic dye fluorescent molecules, fluorescent nanomaterials have the advantages of better optical stability, higher fluorescence intensity, and easy regulation of shape, size, and function [59, 60]. As a result, fluorescent nanomaterials have attracted great attention and have undergone rapid development in the biomedical field. At the cellular level, small-sized fluorescent nanomaterials can enter cells through endocytosis and infiltration and can be used as cellular fluorescent imaging probes to identify and localize specific cells or molecules in a highly selective manner. At the in vivo level, fluorescent nanomaterials can be passively and actively delivered to the lesion site after entering the bloodstream and can be used as fluorescent probes for early diagnosis of disease to provide structural and dynamic information of living samples [61]. In addition, the combination of fluorescent nanomaterials with antibacterial and antitumor drugs through nanotechnology can achieve the integration of diagnosis and treatment [62–65]. In conclusion, fluorescent nanomaterials have become a key link in the cross-integration of materials science, optics, biomedicine, and other disciplines, and they have great application value and prospects.
Fluorescent nanomaterials widely used in biomedicine mainly include quantum dot materials, silicon-based fluorescent nanomaterials, rare earth luminescent nanomaterials, organic fluorescent nanomaterials, and composite nanomaterials of different fluorescent materials.
1.4.1.1 Quantum Dots
Quantum dots, also known as artificial atoms, are generally spherical or spheroidal in shape, and their diameters are often between 2-20 nm, with high crystallinity and micro-size being their typical features. When the size of quantum dots is less than or equal to the exciton Bohr radius, the electrons and holes inside them are quantum limited, and the continuous energy band structure becomes a discrete energy level structure with molecular properties, so the quantum dots produce strong light absorption and luminescence effects (Figure 1.3) [61]. As the size of the quantum dots decreases, the energy difference between the highest valence band and the lowest conduction band increases, which means that the quantum dots require more energy to excite, and at the same time, more energy is released when the crystal returns to the ground state. At this point, the wavelengths at which the quantum dots absorb and emit light are shifted toward shorter wavelengths of higher energy, known as the blue shift. This allows researchers to tune the optical properties of quantum dots according to their size for better applications in biology, medicine, and other fields. In addition to size tuning, the development of new methods for synthesizing quantum dots, such as core-shell structures, alloying, doping, surface ion modification, and voltage tuning, is likely to further facilitate the application of quantum dots in biomedical fields.
Quantum dots can be divided into semiconductor quantum dots (such as II–VI and III–V elements) [56], IV (carbon and silicon) quantum dots, and lead halide chalcogenide (perovskite) quantum dots according to the different constituent elements. Quantum dot materials used in biomedical applications do not contain toxic heavy metal elements such as cadmium or lead, and the most commonly used are carbon quantum dots, zinc-based quantum dots (ZnS, ZnO, and ZnSe), and Ag-based quantum dots (Ag2S and Ag2Se) [65–68]. In addition, most of the current quantum dots are mainly synthesized by the most classical high-temperature pyrolysis method and therefore their surfaces are often covered with alkyl chains. Achieving phase transfer (oil to water) of quantum dots is an important first step in their entry into biological applications. In addition, some quantum dots (like carbon quantum dots) can be synthesized directly in the aqueous phase, making their use in biological environments more convenient [69].
Figure 1.3 (a) Energy diagrams for bulk semiconductor and QDs. (b) Example of cysteine-capped CdTe/ZnTe core/shell QDs synthesized in aqueous media, with a size-dependent luminescence. Upper panel: photographic images of CdTe/ZnTe QDs dispersed in water under UV irradiation. The emitted peak wavelength is marked in white numbers on the top of the image. Lower panel provides an illustration of the corresponding core/shell nanoparticle size from 2 to 8 nm. These core/shell QDs were prepared at the Institute for Lasers, Photonics, and Biophotonics, University at Buffalo.
Source: Reproduced with permission from Ref. [39]; © 2016/American Chemical Society.
Since the first publication of research using quantum dots as bioprobes for fluorescence imaging of living cells in science in 1998, the exploration of quantum dots in the field of biomedical imaging has mushroomed [70]. Carbon quantum dots are widely used in cellular/bacterial imaging and in vivo imaging due to their high fluorescence stability, tunable optical properties, wide source of synthetic raw materials, low cost, and good biocompatibility. Depending on the variation of their fluorescence intensity, they can also be used to detect a wide range of anions and cations (K+, Al3+, Fe3+, ONOO−) [71], drug molecules (antibiotics, tetracycline, methotrexate), biomolecules (DNA, proteins, cysteine, hemoglobin, and cholesterol), bacteria, pH, and fingerprints. Tan and coworkers have used carbon dots encapsulated in organosilicon shells to achieve targeted specific capture of bacteria (Figure 1.4) [72]. The carbon dots@organosilicon surface was modified with anti-Staphylococcus aureus antibodies, which could selectively capture the target bacteria. At the same time, the bacteria were separated using antibody-modified magnetic nanoparticles. The organosilicon shell is then destroyed by reducing the sodium boron hydride (NaBH4), releasing the carbon dots, and causing them to fluoresce. The fluorescence signal was significantly enhanced by the hundreds of carbon dots encapsulated in each organosilicon particle. The fluorescence signal of this method is enhanced by a factor of 108 compared to the conventional assay using only carbon dots as markers. Ag2Se quantum dots with a narrow direct band gap (0.15 eV) are a new type of fluorescent probe in the NIR-II region that has received great attention in recent years [68]. To overcome the problem of low fluorescence quantum, yield due to a large number of cation vacancies and crystal defects caused by the high mobility of Ag ions, Wang and coworkers synthesized silver-gold-selenium (AgAuSe) quantum dots with tunable fluorescence emission spectra in the range of 820–1170 nm by alloying for the first time, which is an important impetus for the research of in vivo fluorescence imaging as well as therapeutic tracing [73].
Figure 1.4 (a) Illustration of the detection of pathogen bacteria with the proposed method and (b) conventional method.
Source: Reproduced with permission from Ref. [72]; © 2018/American Chemical Society.
1.4.1.2 Silicon-Based Fluorescent Nanomaterials
Silicon is a fundamental building block of the human body. Silicon-based fluorescent nanomaterials exhibit good biocompatibility, attractive optical properties, and easy surface modification and have attracted widespread attention and research in the fields of biosensing, disease detection, and imaging. Fluorescence imaging based on silicon-based fluorescent nanomaterials enables long-range real-time imaging for the analysis of cancer, bacterial-related diseases, and ophthalmic diseases. In 2016, researchers in Japan developed a silicon-based fluorescent nanomaterial with a core-double-shell structure [74]. In this structure, crystalline silicon nanoparticles serve as the core, while hydrocarbon groups and surfactants are encapsulated on the surface. Two-photon excitation fluorescence imaging showed that the silicon nanoparticles would efficiently emit light when absorbing NIR light, while the hydrocarbon groups in the coating would increase the luminescence quantum yield. This work enabled the first successful bioimaging of silicon-based fluorescent nanomaterials under 650–1000 nm light irradiation, known as the “bio-optical window.” As the research progressed, the scientists found that conventional fluorescent probes suffered from the need to reintroduce
