Near-Infrared-Light-Assisted in Situ Reduction of Antimicrobial Peptide-Protected Gold Nanoclusters for Stepwise Killing of Bacteria and Cancer Cells

Engineering ultrasmall gold nanoclusters: tailored optical modulation for phototherapeutic and multimodal biomedical applications

Ultrasmall gold nanoclusters (Au NCs) with core sizes below 2 nm exhibit distinctive physicochemical properties and hold remarkable promise in a variety of biomedical applications. Through precise synthesis and surface engineering, Au NCs can be endowed with high quantum yields, excellent stability, and favorable biocompatibility. Recent studies have demonstrated the versatility of Au NCs in imaging modalities-ranging from fluorescence and Raman to photoacoustics-as well as in light-driven therapeutics such as photodynamic therapy (PDT) and photothermal therapy (PTT). This review provides an overview of Au NC design strategies, highlighting ligand-assisted synthesis and supramolecular self-assembly for optimizing optical features and biological performance. Representative biomedical applications in optical imaging, biosensing, and phototherapy are summarized to illustrate the multifaceted benefits of Au NCs in disease diagnosis and treatment. Finally, challenges related to large-scale production, long-term biosafety, and clinical translation are discussed, along with future perspectives on leveraging Au NCs for next-generation theranostic platforms.

Rational Design of Quinoidal Conjugated Polymers for Photothermal Antibacterial Therapy

The increasing prevalence of antibiotic resistance, driven by the overuse and misuse of conventional antibiotics, has become a critical public health concern. Photothermal antibacterial therapy (PTAT) utilizes heat generated by photothermal agents under light exposure to inhibit bacterial growth without inducing resistance, attracting more and more attention. Quinoid conjugated polymers, especially para-azaquinodimethane (AQM) polymer, are a class of organic semiconductors known for efficient π-electron delocalization, near-infrared absorption, and narrow bandgap, showing great potential in the application of photothermal reagents. However, current AQM polymers face challenges related to their solubility, photostability, and biocompability. In this study, tetraglycol is introduced onto the AQM core for improving the drawbacks of the resulting polymers. Two AQM polymers with different electron donor (thiophene and 2,2'-bithiophene) are synthesized and evaluated for their various properties. PAQMT exhibited superior performance, including higher extinction coefficients, improved light absorption, and greater stability under repeated NIR irradiation. PAQMT is further developed into nanoparticles via encapsulation, resulting in excellent colloidal stability, effective bacterial inhibition under 808 nm NIR light. This work provides new strategy in improving the solubility, photostability, and photothermal properties of AQM polymers, offers opportunities for promoting the application of quinoidal conjugated polymers in PTAT.

Antimicrobial peptide biological activity, delivery systems and clinical translation status and challenges

Antibiotic resistance is currently one of the most significant threats to global public health and safety. And studies have found that over the next 25 years, 39 million people will die directly and 169 million indirectly due to antibiotic-resistant diseases. Consequently, the development of new types of antimicrobial drugs is urgently needed. Antimicrobial peptides (AMPs) constitute an essential component of the innate immune response in all organisms. They exhibit a distinctive mechanism of action that endows them with a broad spectrum of biological activities, including antimicrobial, antibiofilm, antiviral, and anti-inflammatory effects. However, AMPs also present certain limitations, such as cytotoxicity, susceptibility to protein hydrolysis, and poor pharmacokinetic properties, which have impeded their clinical application. The development of delivery systems can address these challenges by modifying AMP delivery and enabling precise, controlled release at the site of infection or disease. This review offers a comprehensive analysis of the mechanisms of action and biological advantages of AMPs. and systematically evaluate how emerging drug delivery systems, such as nanoparticles and hydrogels, enhance the stability and bioavailability of AMPs, discussing both their strengths and limitations. Moreover, unlike previous reviews, this review highlight the most recent clinically approved AMP-based drugs and those currently in development, emphasizing the key challenges in translating these drugs into clinical practice. With these perspectives, it is hoped that this review will provide some insights into overcoming translational barriers and advancing AMPs drugs into clinical practice.

Biomolecular ligands as tools to modulate the optical and chiroptical properties of gold nanoclusters

Biomolecule-stabilized gold nanoclusters (AuNCs) have become functional nanomaterials of interest because of their unique optical properties, together with excellent biocompatibility and stability under biological conditions. In this review, we explore the recent advancements in the application of biomolecular ligands for synthesizing AuNCs. Various synthesis approaches that are employing amino acids, peptides, proteins, and DNA as biomolecular scaffolds are reviewed. Furthermore, the influence of the synthesis conditions and nature of the biomolecule on the emerging optical (absorption and photoluminescence) and chiroptical properties of AuNCs is discussed. Finally, the latest research on the applications of biomolecule-stabilized AuNCs for biosensing, bioimaging, and theranostics is presented.

Ultrasmall metal nanoclusters as efficient luminescent probes for bioimaging

Ultrasmall metal nanoclusters (NCs, <2 nm) have emerged as a novel class of luminescent probes due to their atomically precise size and tailored physicochemical properties. The rapid advancements in the design and utilization of metal NC-based luminescent probes are facilitated by the atomic-level manipulation of metal NCs. This review article explores (i) the engineering of metal NCs' functions for bioimaging applications, and (ii) the diverse uses of metal NCs in bioimaging. We begin by presenting an overview of the engineering functions of metal NCs as luminescent probes for bioimaging applications, highlighting key strategies for enhancing NCs' luminescence, biocompatibility and targeting capabilities towards biological specimens. Our discussion then centers on the bioimaging applications of metal NCs in subcellular organelles, individual cells, tissues, and entire organs. Finally, we offer a perspective on the challenges and potential developments in the future use of metal NCs for bioimaging applications.

Three-in-One: Molecular Engineering of D-A-π-A Featured Type I and Type II Near-Infrared AIE Photosensitizers for Efficient Photodynamic Cancer Therapy and Bacteria Killing

Bacterial infections are closely correlated with the genesis and progression of cancer, and the elimination of cancer-related bacteria may improve the efficacy of cancer treatment. However, the combinatorial therapy that utilizes two or more chemodrugs will increase potential adverse effects. Image-guided photodynamic therapy is a highly precise and potential therapy to treat tumor and microbial infections. Herein, four donor-acceptor-π-bridge-acceptor (D-A-π-A) featured near-infrared (NIR) aggregation-induced emission luminogens (AIEgens) (TQTPy, TPQTPy, TQTC, and TPQTC) with type I and type II reaction oxygen species (ROS) generation capabilities are synthesized. Notably, TQTPy shows mitochondria targeted capacity, the best ROS production efficiency, long-term tumor retention capacity, and more importantly, the three-in-one fluorescence imaging guided therapy against both tumor and microbial infections. Both in vitro and in vivo results validate that TQTPy performs well in practical biomedical application in terms of NIR-fluorescence imaging-guided photodynamic cancer diagnosis and treatment. Moreover, the amphiphilic and positively charged TQTPy is able to specific and ultrafast discrimination and elimination of Gram-positive (G+) Staphylococcus aureus from Gram-negative (G-) Escherichia coli and normal cells. This investigation provides an instructive way for the construction of three-in-one treatment for image-guided photodynamic cancer therapy and bacteria elimination.

Prospects of nano-theranostic approaches against breast and cervical cancer

The bottleneck on therapeutics and diagnostics is removed by an alternate approach known as theranostics which combines both therapeutics and diagnostics within a single platform. Due to this "all in one" nature of theranostics, it is now extensively applied in the medicinal field mainly in cancer treatment over the conventional therapy. Recently, FDA approval of lutetium 177 (177Lu) DOTATATE and 177Lu-PSMA-based radionuclide theranostics are clinically used and very few theranostics specific to breast cancer are in clinical trials. In this review, we are willing to draw special attention to the application of theranostics in the most relevant cancers in women, the breast and the cervical as these cancers affect women harshly but talked very silently due to the social restrictions and discriminations mainly in rural areas of developing and under developing countries. This approach not only combines therapeutics and diagnostics but targeting moieties can also be accommodated for the precise medication. Herein, our main objective is to enlighten the broader aspects of different kinds of theranostic devices based on radioisotopes, nanoparticles, graphene quantum dots, dendrimers and their fruitful application against breast and cervical cancer. The development of synthetic nano-theranostics was reported by accommodating therapeutic drugs, imaging probes and targeting ligands through conjugation or encapsulation. The imaging modalities like optical fluorescence, photosensitizers and radiotracers are used to get the diagnostic images through NIR, PET, MRI and CT/SPECT to detect the progress of cancer non-invasively and also at the same time targeting ligands such as antibodies, proteins and peptides in attachment with the theranostics enhances the therapeutic efficacy in addition to the clarity in diagnostics. The applications of theranostics from the last decade with their present scenario in clinics and future perspectives, as well as the pitfalls with the hurdles that still leave questions to rethink from the root are also been discussed in this review.

Intratumoral Microbiota as a Target for Advanced Cancer Therapeutics

In recent years, advancements in microbial sequencing technology have sparked an increasing interest in the bacteria residing within solid tumors and its distribution and functions in various tumors. Intratumoral bacteria critically modulate tumor oncogenesis and development through DNA damage induction, chronic inflammation, epigenetic alterations, and metabolic and immune regulation, while also influencing cancer treatment efficacy by affecting drug metabolism. In response to these discoveries, a variety of anti-cancer therapies targeting these microorganisms have emerged. These approaches encompass oncolytic therapy utilizing tumor-associated bacteria, the design of biomaterials based on intratumoral bacteria, the use of intratumoral bacterial components for drug delivery systems, and comprehensive strategies aimed at the eradication of tumor-promoting bacteria. Herein, this review article summarizes the distribution patterns of bacteria in different solid tumors, examines their impact on tumors, and evaluates current therapeutic strategies centered on tumor-associated bacteria. Furthermore, the challenges and prospects for developing drugs that target these bacterial communities are also explored, promising new directions for cancer treatment.

Highly intense NIR emissive Cu4Pt2 bimetallic clusters featuring Pt(i)-Cu4-Pt(i) sandwich kernel

Metal nanoclusters (NCs) capable of near-infrared (NIR) photoluminescence (PL) are gaining increasing interest for their potential applications in bioimaging, cell labelling, and phototherapy. However, the limited quantum yield (QY) of NIR emission in metal NCs, especially those emitting beyond 800 nm, hinders their widespread applications. Herein, we present a bright NIR luminescence (PLQY up to 36.7%, ∼830 nm) bimetallic Cu4Pt2 NC, [Cu4Pt2(MeO-C6H5-C[triple bond, length as m-dash]C)4(dppy)4]2+ (dppy = diphenyl-2-pyridylphosphine), with a high yield (up to 67%). Furthermore, by modifying the electronic effects of R in RC[triple bond, length as m-dash]C- (R = MeO-C6H5, F-C6H5, CF3-C6H5, Nap, and Biph), we can effectively modulate phosphorescence properties, including the PLQY, emission wavelength, and excited state decay lifetime. Experimental and computational studies both demonstrate that in addition to the electron effects of substituents, ligand modification enhances luminescence intensity by suppressing non-radiation transitions through intramolecular interactions. Simultaneously, it allows the adjustment of emitting wavelengths by tuning the energy gaps and first excited triplet states through intermolecular interactions of ligand substituents. This study provides a foundation for rational design of the atomic-structures of alloy metal NCs to enhance their PLQY and tailor the PL wavelength of NIR emission.

Photofunctional Gold Nanocluster Composites for Bioapplications

Gold nanoclusters (AuNCs), with customized structures and diverse optical properties, are promising optical materials. Constructing composite systems by the assembly and incorporation of AuNCs can utilize their optical properties to achieve diagnostic and therapeutic applications in the biological field. Therefore, the exploration of the assembly behaviors of AuNCs and the enhancement of their performance has attracted widespread interest. In this review, we introduce multiple interactions and assembly modes that are prevalent in nanocomposites and microcomposites based on AuNCs. Then, the functions of AuNC composites for bioapplications are demonstrated in detail. These composite systems have inherited and enhanced the inherent optical performances of the AuNCs to meet diverse requirements for biological sensing and optical treatments. Finally, we discuss the prospects of AuNC composites and highlight the challenges and opportunities in biomedical applications.

Nucleus-targeted carbon dots as peroxidase nanozyme for photoacoustic imaging and phototherapy of tumor

High-purity carbon dots (CDs) with a highly π-conjugated sp2-hybridized graphite structure were prepared by the pulse electrolysis method using the graphite plate as raw material. Photoacoustic signal together with photothermal effect was found in the CDs-dispersed suspensions under near-infrared (NIR) irradiation. For the suspension with the CDs concentration of 500 μg/mL, the photothermal conversion efficiency is high up 64.3% and the solution's temperature can be increased to 82.2 °C under NIR irradiation. Moreover, CDs can be effectively endocytosed by human hepatoma (HepG2) cells with a few hours, act as peroxidase nanozyme to decompose H2O2 and facilitate the production of reactive oxygen species. Under NIR irradiation, CDs exhibit an outstanding apoptosis-inducing effect on HepG2 cells by the photothermal effect. In addition, in vivo experiments show that CDs can be used in photoacoustic imaging (PAI) and guiding the tumor treatment. As a result, the nucleus-targeted CDs with an unique combination of PAI and photothermal effect have potential in cancer diagnosis and treatment.

The roles of templates consisting of amino acids in the synthesis and application of gold nanoclusters

Gold nanoclusters (AuNCs) with low toxicity, high photostability, and facile synthesis have attracted great attention. The ligand is of great significance in stabilizing AuNCs and regulating their properties. Ligands consisting of amino acids (proteins and peptides) are an ideal template for synthesizing applicative AuNCs due to their inherent bioactivity, biocompatibility, and accessibility. In this review, we summarize the correlation of the template consisting of amino acids with the properties of AuNCs by analyzing different peptide sequences. The selection of amino acids can regulate the fluorescence excitation/emission and intensity, size, cell uptake, and light absorption. By analyzing the role played by AuNCs stabilized by proteins and peptides in the application, universal rules and detailed performances of sensors, antibacterial agents, therapeutic reagents, and light absorbers are reviewed. This review can guide the template design and application of AuNCs when selecting proteins and peptides as ligands.

An Au5Ag12(SR)9(dppf)4 alloy nanocluster: structural determination and optical property and photothermal conversion investigation

Photothermal conversion has garnered significant attention due to its potential for efficient energy conversion and application in targeted therapies. However, controlling photothermal properties at the atomic level remains a challenge in current materials synthesis. In this study, we report the synthesis and structural determination of a phosphine and mercaptan co-protected Au5Ag12(SR)9(dppf)4 (Au5Ag12) nanocluster with an extremely low quantum yield (∼0%). For comparative purposes, we synthesized three alloy nanoclusters of similar size. Notably, Au5Ag12 demonstrates a remarkably superior photothermal conversion performance, significantly outperforming the other clusters. We investigated this variance from both absorption and emission perspectives. This research not only opens new avenues for the application of clusters with extremely low quantum yields, but also provides experimental evidence for understanding the photothermal conversion properties of cluster materials at the atomic level.

Drug delivery systems for enhanced tumour treatment by eliminating intra-tumoral bacteria

Cancer remains one of the serious threats to human health. The relationship between bacteria and various tumours has been widely reported in recent years, and studies on intra-tumoral bacteria have become important as intra-tumoral bacteria directly affect the tumorigenesis, progression, immunity and metastatic processes. Therefore, eliminating these commensal intra-tumoral bacteria while treating tumour is expected to be a potential strategy to further enhance the clinical outcome of tumour therapy. Drug delivery systems (DDSs) are widely used to deliver antibiotics and chemotherapeutic drugs for antibacterial and anticancer applications, respectively. Thus, this review firstly provides a comprehensive summary of the association between intra-tumoral bacteria and a host of tumours, followed by a description of advanced DDSs for improving the therapeutic efficacy of cancer treatment through the elimination of intra-tumoral bacteria. It is hoped that this review will provide guidelines for the therapeutic and "synergistic antimicrobial and antitumour" drug delivery strategy.

Biosynthesis of metal nanoparticles: Bioreduction and biomineralization

The biosynthesis of metal nanoparticles by plants, bacteria, and cells has been receiving considerable attention in recent years. The traditional synthesis of metal nanoparticles always needed high temperatures, high pressure, and toxic agents. However, the biosynthesis process (including bioreduction and biomineralization) is simpler, safe, economical, and green. The process of biosynthesis can insulate toxic agents, streamline flux, increase the transition efficiency of interactants, and improve the product yield. The biosynthesized metal nanoparticles share similar characteristics with traditional ones, serving as photosensors to achieve light-to-heat/energy transduction, or a drug delivery system. The biosynthetic metal nanoparticles thus could be widely applied in the medical field for disease diagnosis and treatment. It contributed a novel modality for the facile and green synthesis of metal nanoparticles. Increasing studies have been exploring the mechanism for the biosynthesis of metal nanoparticles, devoted to a controllable biosynthesis process. Combined with our previous studies on the biosynthesis of gold nanoparticles with green tea, tumor cells, and cell components, we reviewed the green methods of bioreduction and biomineralization of metal nanoparticles including the internal mechanism, aimed to make a comprehensive introduction to the biosynthesis of metal nanoparticles and relevant biomedical applications, and inspired further research.

A Review on Gold Nanoclusters for Cancer Phototherapy

Cancer phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has been extensively studied in recent years because of its noninvasive properties, high efficiency, improved selectivity, and reduced side effects. Gold nanoclusters (AuNCs) have the advantages of high biocompatibility, high biosafety, excellent photoresponse, and high tumor penetration ability. This review analyzes the use of AuNCs in tumor phototherapy in recent years from three aspects, namely, AuNCs in PDT, AuNCs in PTT, and AuNCs in combination therapy, and presents the high potential of AuNCs in cancer phototherapy. This review aims to provide readers with the unique advantages, diversified application approaches, and bright application prospects of AuNCs in phototherapy and to provide insights into strategies for applying AuNCs to tumor phototherapy.

Green Synthesis of Antimicrobial Peptide-Protected Silver Nanoclusters with Regulated Antibacterial Behavior

The antibacterial system based on the silver element has been a very promising antibacterial material. However, the antibacterial activity of silver nanomaterials largely depends on their chemical composition and physical properties. Herein, we prepared ultrasmall silver nanoclusters by directly reducing silver ions with antimicrobial peptide in a green way. The positively charged peptide ligands drove the silver nanoclusters binding to bacteria by electrostatic attraction. Contrary to the large-sized silver nanomaterials, the ultrasmall silver nanoclusters were able to rapidly penetrate bacteria membranes via strong hydrophobic association, significantly promoting the generation of reactive oxygen species, and the subsequent high oxidative stress led to bacterial death. Moreover, the silver nanoclusters with antibacterial peptide ligand exhibited good stability, low cytotoxicity, and long-term antibacterial activity. Besides, synergistic enhancement of silver nanoclusters on antibacterial activity was observed. Therefore, the silver nanoclusters conjugated with the antimicrobial peptide can act as a synergistic antibacterial agent, in which their bio-interactions with bacteria have been regulated to achieve a rapid, long-lasting, and broad-spectrum antibacterial effect.

Iron-Doped Metal-Zinc-Centered Organic Framework Mesoporous Carbon Derivatives for Single-Wavelength NIR-Activated Photothermal/Photodynamic Synergistic Therapy

Recently, single-wavelength synergetic photothermal/photodynamic (PTT/PDT) therapy is beginning to make its mark in cancer treatment, and the key to it is a photosensitizer. In this work, an iron-doped metal-zinc-centered organic framework mesoporous carbon derivative (denoted as Fe_x-Zn-NC_T) with a similar porphyrin property was successfully synthesized by a mild, simple, and green aqueous reaction. The effects of different Fe contents and pyrolysis temperatures on the morphology, structure, and PTT/PDT of Fe_x-Zn-NC_T were investigated. Most importantly, we found that Fe₅₀-Zn-NC₉₀₀ exhibited excellent PTT/PDT performance under single-wavelength near-infrared (808 nm) light irradiation in a hydrophilic environment. The photothermal conversion efficiency (η) was counted as ∼81.3%, and the singlet oxygen (¹O₂) quantum yield (Φ) was compared with indocyanine green (ICG) as ∼0.0041. Furthermore, Fe₅₀-Zn-NC₉₀₀ is provided with a clear ability for generating ¹O₂ in living tumor cells and inducted massive necrosis/apoptosis of tumor cells with single-wavelength near-infrared laser irradiation. All of these are clear to consider that Fe₅₀-Zn-NC₉₀₀ displays great potential as an excellent photosensitizer for single-wavelength dual-mode PTT/PDT therapy.

Inhalable GSH-Triggered Nanoparticles to Treat Commensal Bacterial Infection in In Situ Lung Tumors

Bacterial infection has been considered one of the primary reasons for low survival rate of lung cancer patients. Herein, we demonstrated that a kind of mesoporous silica nanoparticles loaded with anticancer drug doxorubicin (DOX) and antimicrobial peptide HHC36 (AMP) (MSN@DOX-AMP) can kill both commensal bacteria and tumor cells under GSH-triggering, modulating the immunosuppressive tumor microenvironment, significantly treating commensal bacterial infection, and eliminating in situ lung tumors in a commensal model. Meanwhile, MSN@DOX-AMP encapsulated DOX and AMP highly efficiently via a combined strategy of physical adsorption and click chemistry and exhibited excellent hemocompatibility and biocompatibility. Importantly, MSN@DOX-AMP could be inhaled and accumulate in lung by a needle-free nebulization, achieving a better therapeutic effect. This system is expected to serve as a straightforward platform to treat commensal bacterial infections in tumors and promote the translation of such inhaled GSH-triggered MSN@DOX-AMP to clinical treatments of lung cancer.

Ligands engineering of gold nanoclusters with enhanced photoluminescence for deceptive information encryption and glutathione detection

Gold nanoclusters (Au NCs) have appeared as an essential alternative to traditional quantum dots and fluorescent molecules for the development of intelligent stimuli-responsive photoluminescence (PL), but the low PL emission of Au NCs restricts their broad applications. Herein, we reported a simple yet effective strategy for preparing Au NCs with high PL by ligands engineering of 4-hydroxy-2-mercapto-6-methylpyrimidine (MTU) and L-Arginine (Arg). Owing to the rigidified shell and the ligand-to-metal charge transfer (LMCT) effects, it was found that the assembly of Arg ligand on MTU-protected Au NCs (Arg/MTU-Au NCs) led to a significantly enhanced PL in the alkaline solution up to 30 times. Moreover, utilizing the tunable LMCT, the Arg/MTU-Au NCs displayed rapid responses to multi-type ionic interaction in a reversible manner, such as H+/OH- and Cu2+/glutathione (GSH) pairs. Inspired by these intriguing ions-responsive LMCT and the associated switchable PL emission, the Arg/MTU-Au NCs were successfully used as excellent stimuli-responsive PL probes for intriguing deceptive information encryption and biosensing as well. This work would provide new insight into regulating the PL emission of Au NCs by ligands engineering and advance their potential applications in information encryption and bioassay.

Inorganic nanomaterials for intelligent photothermal antibacterial applications

Antibiotics are currently the main therapeutic agent for bacterial infections, but they have led to bacterial resistance, which has become a worldwide problem that needs to be addressed. The emergence of inorganic nanomaterials provides a new opportunity for the prevention and treatment of bacterial infection. With the continuous development of nanoscience, more and more inorganic nanomaterials have been used to treat bacterial infections. However, single inorganic nanoparticles (NPs) are often faced with problems such as large dosage, strong toxic and side effects, poor therapeutic effect and so on, so the combination of inorganic nano-materials and photothermal therapy (PTT) has become a promising treatment. PTT effectively avoids the problem of bacterial drug resistance, and can also reduce the dosage of inorganic nanomaterials to a certain extent, greatly improving the antibacterial effect. In this paper, we summarize several common synthesis methods of inorganic nanomaterials, and discuss the advantages and disadvantages of several typical inorganic nanomaterials which can be used in photothermal treatment of bacterial infection, such as precious metal-based nanomaterials, metal-based nanomaterials and carbon-based nanomaterials. In addition, we also analyze the future development trend of the remaining problems. We hope that these discussions will be helpful to the future research of near-infrared (NIR) photothermal conversion inorganic nanomaterials.

One-step synthesized antimicrobial peptide-functionalized gold nanoclusters for selective imaging and killing of pathogenic bacteria

The development of multifunctional nanomaterials with bacterial imaging and killing activities is of great importance for the rapid diagnosis and timely treatment of bacterial infections. Herein, peptide-functionalized gold nanoclusters (CWR11-AuNCs) with high-intensity red fluorescence were successfully synthesized via a one-step method using CWR11 as a template and by optimizing the ratio of CWR11 to HAuCl4, reaction time, pH, and temperature. The CWR11-AuNCs bound to bacteria and exhibited selective fluorescence microscopy imaging properties, which is expected to provide a feasible method for locating and imaging bacteria in complex in vivo environments. In addition, CWR11-AuNCs not only retained the antibacterial and bactericidal activities of CWR11 but also exhibited certain inhibitory or killing effects on gram-negative and gram-positive bacteria and biofilms. The MICs of CWR11-AuNCs against Escherichia coli and Staphylococcus aureus were 178 and 89 μg/ml, respectively. Surprisingly, cell viability in the CWR11-AuNC-treated group was greater than that in the CWR11-treated group, and the low cytotoxicity exhibited by the CWR11-AuNCs make them more promising for clinical applications.

Multifunctional Gold Helix Phototheranostic Biohybrid That Enables Targeted Image-Guided Photothermal Therapy in Breast Cancer

The preparation of multifunctional smart theranostic systems is commonly achieved through complicated strategies, limiting their biomedical applications. Spirulina platensis (SP) microalgae, as a natural helix with some of the intrinsic theranostic functionalities (e.g., fluorescent and photosensitizer pigments), not only facilitates the fabrication process but also guarantees their biosafety for clinical applications. Herein, the helical architecture of gold nanoparticles (AuNPs) based on a SP biotemplate was engineered as a safe, biodegradable, and tumor-targeted biohybrid for imaging-guided photothermal therapy (PTT) to combat triple-negative breast cancer. The quasi-spherical AuNPs were embedded throughout the SP cell (Au-SP) with minimally involved reagents, only by controlling the original morphological stability of SP through pH adjustment of the synthesis media. SP thiolation increased the localization of AuNPs selectively on the cell wall without using a reducing agent (Au-TSP). SP autofluorescence, along with the high X-ray absorption of AuNPs, was employed for dual-modal fluorescence and computed tomography (FL/CT) imaging. Furthermore, the theranostic efficacy of Au-SP was improved through a targeting process with folic acid (Au-SP@CF). High tumor inhibition effects were obtained by the excellent photothermal performance of Au-SP@CF in both in vitro and in vivo analyses. Of particular note, a comparison of the photothermal effect of Au-SP@CF with the naked SP and calcined form of Au-SP@CF not only indicated the key role of the helical architecture of AuNPs in achieving a high photothermal effect but also led to the formation of new gold microspiral biohybrids (Au-MS) over the calcination process. In short, well-controllable immobilization of AuNPs, appropriate biodegradability, good hemocompatibility, long-term biosafety, accurate imaging, high tumor suppression, and low tumor metastasis effects under laser irradiation are an array of intriguing attributes, making the proposed biohybrid a promising theranostic system for FL/CT-imaging-guided PTT.

The anticancer properties of metal-organic frameworks and their heterogeneous nanocomposites

Herein, silver-based metal-organic framework (AgMOF) and its graphene oxide (GO)-decorated nanocomposite (GO-AgMOF) are proposed for use in emerging biomedical applications. The nanocomposites are characterized, and hence, in vitro apoptotic and antibacterial features of AgMOF and GO-AgMOF nanomaterials were investigated. An MTT cytocompatibility assay indicates that these nanomaterials have dose-dependent toxicity in contact with SW480, colon adenocarcinoma cells. In addition, the cell death mechanism was explored by analyzing flow cytometry and caspase activity. Furthermore, the expressions of pro-apoptotic and anti-apoptotic genes were investigated using quantitative polymerase chain reaction (qPCR). Comparing the control group with the groups treated by the nanomaterials indicates up-regulation of the BAX/BCl2 ratio. We also measured the minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) of these nanomaterials acting on S. mutans and S. aureus, which indicates excellent antibacterial properties. Showing inhibition effect on the viability of cancerous cells through apoptosis and antibacterial effects simultaneously, AgMOF and GO-AgMOF can be regarded as potential therapeutics for cancer.

Engineering Gold Nanostructures for Cancer Treatment: Spherical Nanoparticles, Nanorods, and Atomically Precise Nanoclusters

Cancer is a major global health issue and is a leading cause of mortality. It has been documented that various conventional treatments can be enhanced by incorporation with nanomaterials. Thanks to their rich optical properties, excellent biocompatibility, and tunable chemical reactivities, gold nanostructures have been gaining more and more research attention for cancer treatment in recent decades. In this review, we first summarize the recent progress in employing three typical gold nanostructures, namely spherical Au nanoparticles, Au nanorods, and atomically precise Au nanoclusters, for cancer diagnostics and therapeutics. Following that, the challenges and the future perspectives of this field are discussed. Finally, a brief conclusion is summarized at the end.

Composite of gold nanoclusters and basified human serum albumin significantly boosts the inhibition of Alzheimer's β-amyloid by photo-oxygenation

Photo-oxygenation has become an effective way to inhibit Alzheimer's β-amyloid protein (Aβ) fibrillogenesis, which involves oxidative modification of Aβ by photo-oxidants. However, limitations of the current photo-oxidants, such as low biocompatibility and low affinity for Aβ, hinder the progression of the photo-oxygenation strategy. Herein, using human serum albumins (HSA) with binding affinity for Aβ as a platform, we have fabricated HSA-stabilized gold nanoclusters (AuNCs@HSA) and further modified the AuNCs@HSA with ethylenediamine to create basified HSA (HSA-B)-stabilized AuNCs. The basified composite, AuNCs@HSA-B, showed significantly higher potency on the inhibition of β-amyloid formation and capability of reactive oxidative species generation than AuNCs@HSA. In addition to the inhibition effect, under near-infrared (NIR) laser irradiation, AuNCs@HSA-B generated singlet oxygen to oxygenate Aβ monomers, distinctly alleviating Aβ-mediated neurotoxicity at a low concentration. In vivo studies demonstrated that NIR-activated AuNCs@HSA-B promoted the lifespan extension of transgenic C. elegans strain CL2006 by decreasing the Aβ burden. This well-designed AuNCs@HSA-B integrates inhibition, Aβ targeting, and photo-oxygenation, providing new insights into the development of protein-based photo-oxidant against Alzheimer's β-amyloid. STATEMENT OF SIGNIFICANCE: Alzheimer's disease (AD) has been threatening human health for more than 100 years. Recently, researchers have focused on inhibiting β-amyloid protein (Aβ) aggregation by exploring photo-excited biomaterials, which enable modulation of Aβ fibrillization with high spatiotemporal controllability. The present work demonstrates the fabrication of basified human serum albumins (HSA-B)-stabilized gold nanoclusters (AuNCs@HSA-B), and shows the potential of this near-infrared (NIR) laser-activated AuNCs@HSA-B as a photo-oxidant against Aβ aggregation by photo-oxygenation. Our work should open a new horizon in the design of protein-based photo-oxidant for treating AD in the future.

Controlling the Interaction between Fluorescent Gold Nanoclusters and Biointerfaces for Rapid Discrimination of Fungal Pathogens

Nondestructive detection and discrimination of fungal pathogens is essential for rapid and precise treatment, which further effectively prevents antifungal resistance from overused drugs. In this work, fluorescent gold nanoclusters served as the basis for discriminating Candida species. Varied on surface ligands, these gold nanoclusters demonstrated different optical properties as a result of the perturbation effects of ligands. The biointerface interaction between the surface ligands of gold nanoclusters and the cell walls of Candida species can be constructed, and their restriction on ligands perturbation effect produced enhanced fluorescence signals. Owing to the variation of the cell wall composition, cells of different Candida species demonstrated different degrees of association with the gold nanoclusters, leading to discriminable amounts of fluorescence enhancements. The reverse signal response from these gold nanoclusters gives rise to a synergistic and effective assay that allows identification of Candida species.

Spider Toxin Peptide-Induced NIR Gold Nanocluster Fabrication for GSH-Responsive Cancer Cell Imaging and Nuclei Translocation

Goldnanoclusters (GNCs) have become a promising nanomaterial for bioimaging because of their unique optical properties and biocompatibility. In this study, lycosin-I peptide, which possesses a highly selective anticancer activity by affecting the permeability of cancer cell membrane, was firstly modified for constructing fluorescent GNCs (LGNCs) for bioimaging of tumor cells. The obtained LGNCs exhibited strong near-infrared (NIR) fluorescence, which can be further enhanced by the peptide-induced aggregation and selectively stained three cancerous cell lines over normal cell lines with low intrinsic toxicity. After uptake by tumor cells, LGNC aggregates can be depolymerized into ultrasmall nanoclusters by high-level glutathione (GSH) and realize the nuclear targeting translocation. Collectively, our work suggests the potential of natural active biomolecules in designing NIR fluorescent GNCs for bioimaging.

Intramolecular Charge Transfer-Based Conjugated Oligomer with Fluorescence, Efficient Photodynamics, and Photothermal Activities

To develop efficient photoactive agents with satisfactory fluorescence, photodynamic, and photothermal effects is crucial for a phototherapeutic strategy to combat cancer diseases and pathogenic microbes. Herein, a water-soluble donor-acceptor-donor (D-A-D) structured conjugated oligomer was designed and synthesized, consisting of two cyclopenta-dithiophene (CDT) units as the electron donor and boron dipyrromethene (BODIPY) as the electron acceptor. Upon excitation, dual emission was observed for CDT-BODIPY with blue and red fluorescence peaks at 463 nm and at 730 nm, respectively, which was ascribed to intramolecular charge transfer (ICT). Due to the ICT effect, the singlet-to-triplet intersystem crossing rate of CDT-BODIPY was also enhanced, leading to an outstanding photodynamic behavior to produce reactive oxygen species (ROS). Meanwhile, its low bandgap also enabled it a moderate photothermal capability with a conversion efficiency of 33.1%. Taking advantage of its phototriggered activities, this conjugated oligomer exhibited an effective inhibition behavior on the pathogenic growth of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans), which can be guided by dual-wavelength fluorescence imaging. This D-A-D type conjugated oligomer with balanced photophysical characteristics provides a promising strategy to imaging-guided photoactive therapy.

State of the Art and Perspectives on the Biofunctionalization of Fluorescent Metal Nanoclusters and Carbon Quantum Dots for Targeted Imaging and Drug Delivery

The interface of nanobio science and cancer nanomedicine is one of the most important current frontiers in research, being full of opportunities and challenges. Ultrasmall fluorescent metal nanoclusters (MNCs) and carbon quantum dots (CQDs) have emerged as promising fluorescent nanomaterials due to their unique physicochemical and optical properties, facile surface functionalization, good photostability, biocompatibility, and aqueous dispersity. These characteristics make them advantageous over conventional fluorophores such as organic dye molecules and semiconductor quantum dots (QDs) for the detection, diagnosis, and treatment of various diseases including cancer. Recently, researchers have focused on the biofunctionalization strategy of the MNCs and CQDs which can tailor their physicochemical and biological properties and, in turn, can empower these biofunctionalized nanoprobes for diverse applications including imaging, drug delivery, theranostics, and other biomedical applications. In this invited feature article, we first discuss some fundamental structural and physicochemical characteristics of the fluorescent biocompatible quantum-sized nanomaterials which have some outstanding features for the development of multiplexed imaging probes, delivery vehicles, and cancer nanomedicine. We then demonstrate the diverse surface engineering of these fluorescent nanomaterials with reactive target specific functional groups which can help to construct multifunctional nanoprobes with improved targeting capabilities having minimal toxicity. The promising future of the biofunctionalized fluorescent quantum-sized nanomaterials in the field of bioanalytical and biomedical research is elaborately demonstrated, showing selected recent works with relevant applications. This invited feature article finally ends with a short discussion of the current challenges and future prospects of the development of these bioconjugated/biofunctionalized nanomaterials to provide insight into this burgeoning field of MNC- and CQD-based diagnostics and therapeutic applications.

Synthesis of highly stable fluorescent poly(methacrylic acid-co-itaconic)-protected silver nanoclusters and sensitive detection of Cu2

Stable fluorescent silver nanoclusters (AgNCs) were synthesized through one-step UV photoreduction using the multiple carboxyl copolymer poly(methacrylic acid-co-itaconic acid) P(MAA-co-IA) as a novel template. The fluorescence lifetime and the quantum yield of the obtained AgNCs were 1.84 ns and 8.9% in an aqueous solution, respectively. Owing to the multiple carboxyls of the protective P(MAA-co-IA) template, the obtained AgNCs have excellent advantages such as good dispersity, and high stability, which make them suitable for highly sensitive and selective detection of Cu²⁺ by fluorescence quenching. A good linear relationship exists between the degree of fluorescence quenching for silver nanoclusters and Cu²⁺ concentration ranging from 0 to 10 μM. The limit of detection (LOD) is 6.36 nM. The result implies that the as-synthesized AgNCs show great potential in the analysis field.

Multifunctional theranostic nanoparticles for biomedical cancer treatments - A comprehensive review

Modern-day search for the novel agents (their preparation and consequent implementation) to effectively treat the cancer is mainly fuelled by the historical failure of the conventional treatment modalities. Apart from that, the complexities such as higher rate of cell mutations, variable tumor microenvironment, patient-specific disparities, and the evolving nature of cancers have made this search much stronger in the latest times. As a result of this, in about two decades, the theranostic nanoparticles (TNPs) - i.e., nanoparticles that integrate therapeutic and diagnostic characteristics - have been developed. The examples for TNPs include mesoporous silica nanoparticles, luminescence nanoparticles, carbon-based nanomaterials, metal nanoparticles, and magnetic nanoparticles. These TNPs have emerged as single and powerful cancer-treating multifunctional nanoplatforms, as they widely provide the necessary functionalities to overcome the previous/conventional limitations including lack of the site-specific delivery of anti-cancer drugs, and real-time continuous monitoring of the target cancer sites while performing therapeutic actions. This has been mainly possible due to the association of the as-developed TNPs with the already-available unique diagnostic (e.g., luminescence, photoacoustic, and magnetic resonance imaging) and therapeutic (e.g., photothermal, photodynamic, hyperthermia therapy) modalities in the biomedical field. In this review, we have discussed in detail about the recent developments on the aforementioned important TNPs without/with targeting ability (i.e., attaching them with ligands or tumor-specific antibodies) and also the strategies that are implemented to increase their tumor accumulation and to enhance their theranostic efficacies for effective biomedical cancer treatments.

An orthobiologics-free strategy for synergistic photocatalytic antibacterial and osseointegration

Tissue damage caused by hyperthermia during photothermal therapy (PTT) has largely limited its clinical applications for implant infection. However, rescue of tissue regeneration by conjugating orthobiologics with PTT has been problematic as they can easily deactivate biologics while eradicating bacteria. Herein, we report an orthobiologics-free strategy to synergistically couple photocatalytic antibacterial with pro-osteogenic capacity via self-assembly of copper sulphide nanoparticle (CuS NP) and reduced graphene oxide (rGO) on implant surface. This strategy not only offers enhanced photothermal effects for bacterial eradiation via near-infrared light (NIR), but also promotes vascularized osseointegration via cooperation of copper ion with rGO. In vitro and in vivo data showed that coupling CuS and rGO synergistically increased antibacterial efficacy of implants by 40 times and successfully destroyed bacterial biofilm upon NIR. Moreover, CuS/rGO decorated surface substantially improved bone marrow stromal cell adhesion, proliferation, as well as subsequent differentiation toward osteoblast. We also revealed that enhanced peri-implant vascularization may be attributed to the sustained release of copper ion from CuS NPs, which further collaborated with rGO to promote vascularized osseointegration. Altogether, this novel orthobiologics-free approach offers a practical alternative to circumvent the intrinsic drawbacks of PTT and endows powerful antibacterial and pro-osteogenic capacities for implant associated infections.

Gold Nanomaterials as a Promising Integrated Tool for Diagnosis and Treatment of Pathogenic Infections-A Review

This review summarizes research on functionalized gold nanomaterials as pathogen detection sensors and pathogen elimination integrated tools. After presenting the challenge of current severe threat from pathogenic bacteria and the increasingly serious growth rate of drug resistance, the first section mainly introduces the conspectus of gold nanostructures from synthesis, characterization, physicochemical properties and applications of gold nanomaterials. The next section deals with gold nanomaterials-based pathogen detection sensors such as colorimetric sensors, fluorescence sensors and Surface-Enhanced Raman Scattering sensors. We then discuss strategies based on gold nanomaterials for eliminating pathogenic infections, such as the dual sterilization strategy for grafting gold nanomaterials with antibacterial substances, photothermal antibacterial and photodynamic antibacterial methods. The fourth part briefly introduces the comprehensive strategy for diagnosis and sterilization of pathogen infection based on gold nanomaterials, such as the diagnosis and treatment strategy for pathogen infection using Roman signals real-time monitoring and photothermal sterilization. A concluding section that summarizes the current status and challenges of the novel diagnosis and treatment integrated strategy for pathogenic infections, gives an outlook on potential future perspectives.

Free Radical Polymerization of Gold Nanoclusters and Hydrogels for Cell Capture and Light-Controlled Release

Gold nanocluster (AuNC) decorated hydrogels have attracted considerable attention as versatile biomaterials. To date AuNCs and hydrogels have mainly been mixed as independent components. Here, we report the use of AuNCs as reactive monomers in the polymerization of hydrogels. We used a free radical polymerization to copolymerize AuNCs with acrylamide and N-acryloyl glycinamide to prepare stimuli-responsive smart hydrogels. Multiple C═C bonds were decorated on the surface of the AuNCs as active sites for polymerization. These C═C bonds not only protected the structure of the AuNCs from oxidation by free radicals during polymerization but also covalently connected the AuNCs with the polymer chains. This structure ensured good photothermal performance of the AuNCs while preserving the thermoresponsive hydrogen bonds of polymers. Moreover, the copolymerized AuNCs acted as cross-linkers, which improved the mechanical properties of the hydrogels. These smart hydrogels had good stability, efficient photothermal conversion, and a sensitive thermoresponsive. We examined their potential for capture of MDA-MB-231 cells with hyaluronic acid as target molecules. The captured cells were released under 660 nm irradiation. This process of targeted capture and light-controlled remote release could be repeatedly applied. These results suggest that systems based on AuNCs copolymerized with hydrogels have great potential for biomedical applications.

Development of General Methods for Detection of Virus by Engineering Fluorescent Silver Nanoclusters

Viruses have caused significant damage to the world. Effective detection is required to relieve the impact of viral infections. A biomolecule can be used as a template such as deoxyribonucleic acid (DNA), peptide, or protein, for the growth of silver nanoclusters (AgNCs) and for recognizing a virus. Both the AgNCs and the recognition elements are tunable, which is promising for the analysis of new viruses. Considering that a new virus such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) urgently requires a facile sensing strategy, various virus detection strategies based on AgNCs including fluorescence enhancement, color change, quenching, and recovery are summarized. Particular emphasis is placed on the molecular analysis of viruses using DNA stabilized AgNCs (DNA-AgNCs), which detect the virus's genetic material. The more widespread applications of AgNCs for general virus detection are also discussed. Further development of these technologies may address the challenge for facile detection of SARS-CoV-2.

Catalytic Nanomaterials toward Atomic Levels for Biomedical Applications: From Metal Clusters to Single-Atom Catalysts

Single-atom catalysts (SACs) featuring the complete atomic utilization of metal, high-efficient catalytic activity, superior selectivity, and excellent stability have been emerged as a frontier in the catalytic field. Recently, increasing interests have been drawn to apply SACs in biomedical fields for enzyme-mimic catalysis and disease therapy. To fulfill the demand of precision and personalized medicine, precisely engineering the structure and active site toward atomic levels is a trend for nanomedicines, promoting the evolution of metal-based biomedical nanomaterials, particularly biocatalytic nanomaterials, from nanoparticles to clusters and now to SACs. This review outlines the syntheses, characterizations, and catalytic mechanisms of metal clusters and SACs, with a focus on their biomedical applications including biosensing, antibacterial therapy, and cancer therapy, as well as an emphasis on their in vivo biological safeties. Challenges and future perspectives are ultimately prospected for SACs in diverse biomedical applications.

Antibacterial nanosystems for cancer therapy

Bacteria and cancer cells share a unique symbiotic relationship in the process of cancer development and treatment. It has been shown that certain bacteria can mediate cancer and thrive inside cancerous tissues. Moreover, during cancer treatment, microbial infections have been shown to impair the therapeutic efficacy and lead to serious complications. In the past decades, the application of antibiotics has achieved great success in fighting numerous bacteria but the administration route, low localization effects and related drug resistance limit the further utilization of antibiotics. Recently, advances in nanotechnology have made a significant impact in the medical field, which enhance the drug solubility and can target lesion sites, and some nanomaterials can even be applied as the therapeutic agent itself. In this review, we introduce anti-bacterial nanosystems for cancer therapy in the aspects of spontaneous and triggered anti-bacterial action, and our notions, as well as proposed research directions for the further development of this field, are discussed.

Development of coinage metal nanoclusters as antimicrobials to combat bacterial infections

Infections from antibiotic-resistant bacteria have caused huge economic loss and numerous deaths over the past decades. Researchers are exploring multiple strategies to combat these bacterial infections. Metal nanomaterials have been explored as therapeutics against these infections owing to their relatively low toxicity, broad-spectrum activity, and low bacterial resistance development. Some coinage metal nanoclusters, such as gold, silver, and copper nanoclusters, can be readily synthesized. These nanoclusters can feature multiple useful properties, including ultra-small size, high catalytic activity, unique photoluminescent properties, and photothermal effect. Coinage metal nanoclusters have been investigated as antimicrobials, but more research is required to tap their full potential. In this review, we discuss multiple advantages and the prospect of using gold/silver/copper nanoclusters as antimicrobials.

Self-assembled nanogels of luminescent thiolated silver nanoclusters and chitosan as bactericidal agent and bacterial sensor

Multifunctional theranostic agents with the features of good biocompatibility, long-term antibacterial efficacy, and rapid bacterial detection are the desired future medicine for infectious diseases, but which poses huge challenges on the design of such multifunctional nanocomposites in a single entity. Herein, self-assembled nanogels of thiolated silver nanoclusters (Ag NCs) and chitosan was designed and synthesized, which combines the desirable biocompatible, targeting specific, luminescent properties. This nanogel displays an amplified luminescence via strong matrix-ligand coordination between thiolate ligands and chitosan matrix to rigidify the molecular structure on the surface of Ag NCs. Concomitantly, this nanogel exhibits exceptional bactericidal activity, with approximately >10-fold stronger activity compared to its counterpart Ag NCs. Furthermore, a bacterial detection system was developed based on the bacterial binding on the fluorescent nanogels. This work provides a new strategy in designing multifunctional theranostic agents and this new composite Ag NC nanogel holds great promise for practical applications as the theranostic nanomedicines.

Regulating the Optical Properties of Gold Nanoclusters for Biological Applications

Gold nanoclusters are promising optically functional materials because of their attractive optical properties, such as luminescence, two-photon absorption, photothermal conversion, and photodynamics. Regulating the optical functions of gold nanoclusters and improving their performance have attracted wide interest in biological applications. In this Review, we introduce the principles to manipulate both the intrinsic optical properties and the apparent optical performance of gold nanoclusters. Manipulating the surface ligands and compounding with other nanomaterials are facile and efficient strategies. Based on the regulated optical properties, the gold nanoclusters can be well applied in various biomedical applications from multimodal bioimaging toward theranostics. By correlating structures and optical properties, we expect a better utilization of the optical gold nanoclusters in the biological field.