Hybrid Plasmonic Nanodumbbells Engineering for Multi-Intensified Second Near-Infrared Light Induced Photodynamic Therapy

Advancements of Porphyrin-Derived Nanomaterials for Antibacterial Photodynamic Therapy and Biofilm Eradication

The threat posed by antibiotic-resistant bacteria and the challenge of biofilm formation has highlighted the inadequacies of conventional antibacterial therapies, leading to increased interest in antibacterial photodynamic therapy (aPDT) in recent years. This approach offers advantages such as minimal invasiveness, low systemic toxicity, and notable effectiveness against drug-resistant bacterial strains. Porphyrins and their derivatives, known for their high molar extinction coefficients and singlet oxygen quantum yields, have emerged as crucial photosensitizers in aPDT. However, their practical application is hindered by challenges such as poor water solubility and aggregation-induced quenching. To address these limitations, extensive research has focused on the development of porphyrin-based nanomaterials for aPDT, enhancing the efficacy of photodynamic sterilization and broadening the range of antimicrobial activity. This review provides an overview of various porphyrin-based nanomaterials utilized in aPDT and biofilm eradication in recent years, including porphyrin-loaded inorganic nanoparticles, porphyrin-based polymer assemblies, supramolecular assemblies, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Additionally, insights into the prospects of aPDT is offered, highlighting its potential for practical implementation.

Polyethyleneimine surface-modified silver-selenium nanocomposites for anti-infective treatment of wounds by disrupting biofilms

Bacterial biofilm formation is associated with the pathogenicity of pathogens and poses a serious threat to human health and clinical therapy. Complex biofilm structures provide physical barriers that inhibit antibiotic penetration and inactivate antibiotics via enzymatic breakdown. The development of biofilm-disrupting nanoparticles offers a promising strategy for combating biofilm infections. Hence, polyethyleneimine surface-modified silver-selenium nanocomposites, Ag@Se@PEI (ASP NCs), were designed for synergistic antibacterial effects by destroying bacterial biofilms to promote wound healing. The results ofin vitroantimicrobial experiments showed that, ASP NCs achieved efficient antibacterial effects againstStaphylococcus aureus (S. aureus)andEscherichia coli (E. coli)by disrupting the formation of the bacterial biofilm, stimulating the outbreak of reactive oxygen species and destroying the integrity of bacterial cell membranes. Thein-vivobacterial infection in mice model showed that, ASP NCs further promoted wound healing and new tissue formation by reducing inflammatory factors and promoting collagen fiber formation which efficiently enhanced the antibacterial effect. Overall, ASP NCs possess low toxicity and minimal side effects, coupled with biocompatibility and efficient antibacterial properties. By disrupting biofilms and bacterial cell membranes, ASP NCs reduced inflammatory responses and accelerated the healing of infected wounds. This nanocomposite-based study offers new insights into antibacterial therapeutic strategies as potential alternatives to antibiotics for wound healing.

Ternary heterostructure-driven photoinduced electron-hole separation enhanced oxidative stress for triple-negative breast cancer therapy

Zinc oxide nanoparticles (ZnO NPs) stand as among the most significant metal oxide nanoparticles in trigger the formation of reactive oxygen species (ROS) and induce apoptosis. Nevertheless, the utilization of ZnO NPs has been limited by the shallowness of short-wavelength light and the constrained production of ROS. To overcome these limitations, a strategy involves achieving a red shift towards the near-infrared (NIR) light spectrum, promoting the separation and restraining the recombination of electron-hole (e--h+) pairs. Herein, the hybrid plasmonic system Au@ZnO (AZ) with graphene quantum dots (GQDs) doping (AZG) nano heterostructures is rationally designed for optimal NIR-driven cancer treatment. Significantly, a multifold increase in ROS generation can be achieved through the following creative initiatives: (i) plasmonic Au nanorods expands the photocatalytic capabilities of AZG into the NIR domain, offering a foundation for NIR-induced ROS generation for clinical utilization; (ii) elaborate design of mesoporous core-shell AZ structures facilitates the redistribution of electron-hole pairs; (iii) the incorporation GQDs in mesoporous structure could efficiently restrain the recombination of the e--h+ pairs; (iv) Modification of hyaluronic acid (HA) can enhance CD44 receptor mediated targeted triple-negative breast cancer (TNBC). In addition, the introduced Au NRs present as catalysts for enhancing photothermal therapy (PTT), effectively inducing apoptosis in tumor cells. The resulting HA-modified AZG (AZGH) exhibits efficient hot electron injection and e--h+ separation, affording unparalleled convenience for ROS production and enabling NIR-induced PDT for the cancer treanment. As a result, our well-designed mesoporous core-shell AZGH hybrid as photosensitizers can exhibit excellent PDT efficacy.

Functional nanomaterials as photosensitizers or delivery systems for antibacterial photodynamic therapy

Bacterial infection is a global health problem that closely related to various diseases threatening human life. Although antibiotic therapy has been the mainstream treatment method for various bacterial infectious diseases for decades, the increasing emergence of bacterial drug resistance has brought enormous challenges to the application of antibiotics. Therefore, developing novel antibacterial strategies is of great importance. By producing reactive oxygen species (ROS) with photosensitizers (PSs) under light irradiation, antibacterial photodynamic therapy (aPDT) has emerged as a non-invasive and promising approach for treating bacterial infections without causing drug resistance. However, the insufficient therapeutic penetration, poor hydrophilicity, and poor biocompatibility of traditional PSs greatly limit the efficacy of aPDT. Recently, studies have found that nanomaterials with characteristics of favorable photocatalytic activity, surface plasmonic resonance, easy modification, and high drug loading capacity can improve the therapeutic efficacy of aPDT. In this review, we aim to provide a comprehensive understanding of the mechanism of nanomaterials-mediated aPDT and summarize the representative nanomaterials in aPDT, either as PSs or carriers for PSs. In addition, the combination of advanced nanomaterials-mediated aPDT with other therapies, including targeted therapy, gas therapy, and multidrug resistance (MDR) therapy, is reviewed. Also, the concerns and possible solutions of nanomaterials-based aPDT are discussed. Overall, this review may provide theoretical basis and inspiration for the development of nanomaterials-based aPDT.

H2O2 self-supplying and GSH-depleting nanosystem for amplified NIR mediated-chemodynamic therapy of MRSA biofilm-associated infections

Reactive oxygen species (ROS) has emerged as potent therapeutic agents for biofilm-associated bacterial infections. Chemodynamic therapy (CDT), involving the generation of high-energy ROS, displays great potential in the therapy of bacterial infections. However, challenges such as insufficient hydrogen peroxide (H2O2) and over-expressed glutathione (GSH) levels within the microenvironment of bacterial biofilms severely limit the antibacterial efficacy of CDT. Herein, we have developed a multifunctional nanoplatform (CuS@CaO2@Dex) by integrating copper sulfide (CuS) and calcium peroxide (CaO2) into dextran (Dex)-coated nanoparticles. This innovative platform enhanced ROS generation for highly efficient biofilm elimination by simultaneously supplying H2O2 and depleting GSH. The Dex-coating facilitated the penetrability of CuS@CaO2@Dex into biofilms, while CaO2 generated a substantial amount of H2O2 in the acidic biofilm microenvironment. CuS, through a Fenton-like reaction, catalyzed the conversion of self-supplied H2O2 into hydroxyl radicals (•OH) and consumed the overexpressed GSH. Additionally, the incorporation of near-infrared II (NIR II) laser irradiation enhanced the photothermal properties of CuS, improving the catalytic efficiency of the Fenton-like reaction for enhanced antibacterial effects. In vivo experiments have demonstrated that CuS@CaO2@Dex exhibited remarkable antibacterial and antibiofilm efficacy, exceptional wound healing capabilities, and notable biosafety. In summary, the Dex-coated nanoplatform proposed in this study, with its self-sterilization capability through ROS, holds significant potential for future biomedical applications.

Type I photodynamic antimicrobial therapy: Principles, progress, and future perspectives

The emergence of drug-resistant bacteria has significantly diminished the efficacy of existing antibiotics in the treatment of bacterial infections. Consequently, the need for finding a strategy capable of effectively combating bacterial infections has become increasingly urgent. Photodynamic therapy (PDT) is considered one of the most promising emerging antibacterial strategies due to its non-invasiveness, low adverse effect, and the fact that it does not lead to the development of drug resistance. However, bacteria at the infection sites often exist in the form of biofilm instead of the planktonic form, resulting in a hypoxic microenvironment. This phenomenon compromises the treatment outcome of oxygen-dependent type-II PDT. Compared to type-II PDT, type-I PDT is not constrained by the oxygen concentration in the infected tissues. Therefore, in the treatment of bacterial infections, type-I PDT exhibits significant advantages over type-II PDT. In this review, we first introduce the fundamental principles of type-I PDT in details, including its physicochemical properties and how it generates reactive oxygen species (ROS). Next, we explore several specific antimicrobial mechanisms utilized by type-I PDT and summarize the recent applications of type-I PDT in antimicrobial treatment. Finally, the limitations and future development directions of type-I photosensitizers are discussed. STATEMENT OF SIGNIFICANCE: The misuse and overuse of antibiotics have accelerated the development of bacterial resistance. To achieve the effective eradication of resistant bacteria, pathfinders have devised various treatment strategies. Among these strategies, type I photodynamic therapy has garnered considerable attention owing to its non-oxygen dependence. The utilization of non-oxygen-dependent photodynamic therapy not only enables the effective elimination of drug-resistant bacteria but also facilitates the successful eradication of hypoxic biofilms, which exhibits promising prospects for treating biofilm-associated infections. Based on the current research status, we anticipate that the novel type I photodynamic therapy agent can surmount the biofilm barrier, enabling efficient treatment of hypoxic biofilm infections.

2D MOF based-heterostructure with hierarchical architecture as antibacterial wound dressing

Bacterial infections pose a huge threat to human health due to the inevitable emergency of drug resistance. Metal-organic frameworks (MOFs) consisting of metal ions and organic linkers, as emerging efficient antibacterial material, have the merits of structural flexibility and adjustable physicochemical property. With assistance of photosensitive agents as organic linkers, MOFs have great potential in antibacterial application through photocatalytic therapy by the generation of reactive oxygen species (ROS). However, the limited light use efficiency and short lifespan of ROS are two obstacles for their applications. Inspired by the semiconductor heterostructure in photocatalysis, we rationally design and precisely synthesize MOFs based heterostructures, in which the TiO2 nanoclusters are filled into the pores of Cu-TCPP nanosheets (i.e. TiO2 NCs@Cu-TCPP HSs). And the composite materials possess three-dimensional (3D) hierarchical architectures, which have advantages of large surface area, excellent light-absorbing ability and photocatalytic efficiency. Significantly, this novel material displays >99.99 % antibacterial efficiency against E. coli and S. aureus within 30 min and preserves the excellent antibacterial ability during reusing three times, which is superior to recently reported photocatalystic-based antibacterial materials. Our study provides new insights into the energy band engineering for enhanced antibacterial performance, paving a way for designing advanced clinical wound dressings.

Urchin-like Fe3O4@Bi2S3 Nanospheres Enable the Destruction of Biofilm and Efficiently Antibacterial Activities

Biofilm-associated infections (BAIs) have been considered a major threat to public health, which induce persistent infections and serious complications. The poor penetration of antibacterial agents in biofilm significantly limits the efficiency of combating BAIs. Magnetic urchin-like core-shell nanospheres of Fe3O4@Bi2S3 were developed for physically destructing biofilm and inducing bacterial eradication via reactive oxygen species (ROS) generation and innate immunity regulation. The urchin-like magnetic nanospheres with sharp edges of Fe3O4@Bi2S3 exhibited propeller-like rotation to physically destroy biofilm under a rotating magnetic field (RMF). The mild magnetic hyperthermia improved the generation of ROS and enhanced bacterial eradication. Significantly, the urchin-like nanostructure and generated ROS could stimulate macrophage polarization toward the M1 phenotype, which could eradicate the persistent bacteria with a metabolic inactivity state through phagocytosis, thereby promoting the recovery of implant infection and inhibiting recurrence. Thus, the design of magnetic-driven sharp-shaped nanostructures of Fe3O4@Bi2S3 provided enormous potential in combating biofilm infections.

Deepened Photodynamic Therapy through Skin Optical Clearing Technology in the Visible Light Window

The trade-off that shorter wavelength light facilitates the efficient generation of reactive oxygen species (ROS) from photosensitizer (PS) while facing the drawback of limited penetration depth through skin tissue restricts the further development of photodynamic therapy (PDT). Here, we address this contradiction and achieve visible-light-tailored deep PDT combined with the skin optical clearing technology. With the help of the prepared skin optical clearing gel, the refractive index inhomogeneity between skin tissue components is greatly attenuated, and the light scattering effect within the skin tissue is remarkably reduced. As a consequence, the transmittance of visible light at 600 nm through in vitro porcine skin and in vivo mouse skin after treatment increases from approximately 10 and 40 to 70 and 70%, respectively. Furthermore, in the tumor cell eradication experiment, the local ROS generation efficiency in the experimental group is several times higher than that in the control group owing to improved visible transmittance, which is thus responsible for the complete eradication of tumor cells, even when shaded by skin tissue. The results suggest that this strategy may serve as a valuable supplement to the current deep PDT strategies.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

Water flow promoted charge separation in piezoelectric Bi4Ti3O12 for the enhanced photocatalytic degradation of antibiotic

Addressing the issue of antibiotic residues in the environment is key to improving the quality of aquatic environments and reducing human health risks. In this study, piezoelectric bismuth titanate (Bi4Ti3O12) nanosheets are synthesized and employed to conduct antibiotic degradation. The piezoelectric potential induced by the water flow shear force is utilized to facilitate charge separation and migration in the photocatalytic process and enhance the catalytic degradation of antibiotic wastewater. As a result, 85% of tetracycline hydrochloride (TC) is degraded within 90 min. The piezo-photocatalytic process exhibits a 2.4 times faster reaction rate and a 15% higher mineralization rate than photocatalysis. Different environmental factors are investigated for their effects on the catalytic activity in piezo-photocatalysis. In situ electrochemical measurement and photoluminescence (PL) spectroscopy under stress demonstrated that the piezoelectric potential shifted the energy band of Bi4Ti3O12 and promoted the charge migration and separation, which produce more active species that favor the efficient catalytic degradation. Finally, the intermediate products of the tetracycline hydrochloride degradation process are analyzed and possible degradation pathways are suggested. This study elucidates the degradation mechanism of Bi4Ti3O12 as a piezo-photocatalyst for antibiotic pollutants, and meticulously investigates the charge transfer mechanism of the catalyst material in response to micro-stress. Hence, it provides an efficient solution for organic wastewater treatment and can potentially provide theoretical support for the development and performance optimization of catalyst materials applied in natural environments.

Photocatalytic microbial disinfection under indoor conditions: Prospects and challenges of near IR-photoactive materials

The accumulation of microbes especially in the air and in water bodies is causing the major disease outbreaks. Indoor environment remediation methods are necessary today to clean up these microbes. Among the remediation methods available, in situ generation of highly reactive and oxidizing radical species by advanced oxidation processes (AOPs) inactivate most of the microbes unselectively. Of these AOPs, photocatalytic microbial disinfection especially under indoor conditions is of great interest to maintain microbe-free indoor environment. For efficient microbes' inactivation under indoor conditions, the near IR and IR response of the photocatalysts must be improved. Though the photocatalytic disinfection of microbes using semiconductor-based photocatalysts has been extensively investigated, most of the photocatalysts that have been investigated are either weekly responsive or totally not irresponsive to IR photons due to inappropriate bandgap energies. Several strategies have been investigated to enhance the light harvesting properties of semiconductor based photocatalysts under indoor conditions and make them active to near IR and IR radiations. This review summarizes the recent progress in the field of materials for photocatalysts employed for microbial removal in indoor environments over the past decade as well as outlines key perspectives to enlighten future researches. The paper details the fundamentals of photocatalysis and basic properties of photocatalytic materials in the disinfection of common microbes under indoor conditions. The applications of photocatalytic materials in the disinfection of microbes in indoor environmental conditions are discussed and reviewed. Finally, the remaining challenges and future strategies/prospects in the design and synthesis of IR (and near IR) responsive photocatalysts are discussed.

Gold Nanorod/Titanium Dioxide Hybrid Nanoparticles for Plasmon-Enhanced Near-Infrared Photoproduction of Hydroxyl Radicals and Photodynamic Therapy

Gold nanoparticles, such as nanorods (AuNRs), present exceptionally high absorption cross sections that can be tuned to the near-infrared (NIR), the optimal window for light penetration in biological tissues. This makes them valuable photosensitizers for the treatment of cancer using photothermal therapy, where absorbed light energy is converted into heat. In addition, there is a strong interest in using hot electron carriers generated in AuNRs by NIR irradiation to produce cytotoxic radical oxygen species in order to enhance the efficiency of the phototherapy. Here, we show that hybrid nanoparticles composed of AuNRs with TiO2 deposited at their extremities are efficient sensitizers to produce hydroxyl radical species under NIR irradiation. We attribute this phenomenon to the transfer of hot electrons generated from the plasmon excitation in AuNR to the TiO2 tips, followed by reduction of dioxygen. We then functionalize these hybrid AuNR/TiO2 nanoparticles with block poly(ethylene glycol)-phosphonate polymer ligands to stabilize them in a physiological medium. We finally demonstrate that the photodynamic effect induces cell death upon irradiation with a greater efficiency than the photothermal effect alone.

Partial Chemicalization of Nanoscale Metals: An Intra-Material Transformative Approach for the Synthesis of Functional Colloidal Metal-Semiconductor Nanoheterostructures

Heterostructuring colloidal nanocrystals into multicomponent modular constructs, where domains of distinct metal and semiconductor phases are interconnected through bonding interfaces, is a consolidated approach to advanced breeds of solution-processable hybrid nanomaterials capable of expressing richly tunable and even entirely novel physical-chemical properties and functionalities. To meet the challenges posed by the wet-chemical synthesis of metal-semiconductor nanoheterostructures and to overcome some intrinsic limitations of available protocols, innovative transformative routes, based on the paradigm of partial chemicalization, have recently been devised within the framework of the standard seeded-growth scheme. These techniques involve regiospecific replacement reactions on preformed nanocrystal substrates, thus holding great synthetic potential for programmable configurational diversification. This review article illustrates achievements so far made in the elaboration of metal-semiconductor nanoheterostructures with tailored arrangements of their component modules by means of conversion pathways that leverage on spatially controlled partial chemicalization of mono- and bi-metallic seeds. The advantages and limitations of these approaches are discussed within the context of the most plausible mechanisms underlying the evolution of the nanoheterostructures in liquid media. Representative physical-chemical properties and applications of chemicalization-derived metal-semiconductor nanoheterostructures are emphasized. Finally, prospects for developments in the field are outlined.

Gold-semiconductor nanohybrids as advanced phototherapeutics

Phototherapeutics is gaining momentum as a mainstream treatment for cancer, with gold-semiconductor nanocomposites showing promise as potent phototherapeutic agents due to their structural tunability, biocompatibility and functional diversity. Such nanohybrids possess plasmonic characteristics in the presence of gold and the catalytic nature of semiconductor units, as well as the unexpected physicochemical properties arising from the contact interface. This perspective provides an overview of the latest research on gold-semiconductor nanocomposites for photodynamic, photothermal and photocatalytic therapy. The relationship between the spatial configuration of these nanohybrids and their practical performance was explored to deliver comprehensive insights and guidance for the design and fabrication of novel composite nanoplatforms to enhance the efficiency of phototherapeutics, promoting the development of nanotechnology-based advanced biomedical applications.

Precise Engineering of a Se/Te Nanochaperone for Reinvigorating Cancer Radio-Immunotherapy

Facilely synthesized nanoradiosensitizers with well-controlled structure and multifunctionality are greatly desired to address the challenges of cancer radiotherapy. In this work, a universal method is developed for synthesizing chalcogen-based TeSe nano-heterojunctions (NHJs) with rod-, spindle-, or dumbbell-like morphologies by engineering the surfactant and added selenite. Interestingly, dumbbell-shaped TeSe NHJs (TeSe NDs) as chaperone exhibit better radio-sensitizing activities than the other two nanostructural shapes. Meanwhile, TeSe NDs can serve as cytotoxic chemodrugs that degrade to highly toxic metabolites in acidic environment and deplete GSH within tumor to facilitate radiotherapy. More importantly, the combination of TeSe NDs with radiotherapy significantly decreases regulatory T cells and M2-phenotype tumor-associated macrophage infiltrations within tumors to reshape the immunosuppressive microenvironment and induce robust T lymphocytes-mediated antitumor immunity, resulting in great abscopal effects on combating distant tumor progression. This study provides a universal method for preparing NHJ with well-controlled structure and developing nanoradiosensitizers to overcome the clinical challenges of cancer radiotherapy.

Drug-Free Antimicrobial Nanomotor for Precise Treatment of Multidrug-Resistant Bacterial Infections

Manufacturing heteronanostructures with specific physicochemical characteristics and tightly controllable designs is very appealing. Herein, we reported NIR-II light-driven dual plasmonic (AuNR-SiO₂-Cu₇S₄) antimicrobial nanomotors with an intended Janus configuration through the overgrowth of copper-rich Cu₇S₄ nanocrystals at only one high-curvature site of Au nanorods (Au NRs). These nanomotors were applied for photoacoustic imaging (PAI)-guided synergistic photothermal and photocatalytic treatment of bacterial infections. Both the photothermal performance and photocatalytic activity of the nanomotors are dramatically improved owing to the strong plasmon coupling between Au NRs and the Cu₇S₄ component and enhanced energy transfer. The motion behavior of nanomotors promotes transdermal penetration and enhances the matter-bacteria interaction. More importantly, the directional navigation and synergistic antimicrobial activity of the nanomotors could be synchronously driven by NIR-II light. The marriage of active motion and enhanced antibacterial activity resulted in the expected good antibacterial effects in an abscess infection mouse model.

Active Site Engineering on Plasmonic Nanostructures for Efficient Photocatalysis

Plasmonic nanostructures have shown immense potential in photocatalysis because of their distinct photochemical properties associated with tunable photoresponses and strong light-matter interactions. The introduction of highly active sites is essential to fully exploit the potential of plasmonic nanostructures in photocatalysis, considering the inferior intrinsic activities of typical plasmonic metals. This review focuses on active site-engineered plasmonic nanostructures with enhanced photocatalytic performance, wherein the active sites are classified into four types (i.e., metallic sites, defect sites, ligand-grafted sites, and interface sites). The synergy between active sites and plasmonic nanostructures in photocatalysis is discussed in detail after briefly introducing the material synthesis and characterization methods. Active sites can promote the coupling of solar energy harvested by plasmonic metal to catalytic reactions in the form of local electromagnetic fields, hot carriers, and photothermal heating. Moreover, efficient energy coupling potentially regulates the reaction pathway by facilitating the excited state formation of reactants, changing the status of active sites, and creating additional active sites using photoexcited plasmonic metals. Afterward, the application of active site-engineered plasmonic nanostructures in emerging photocatalytic reactions is summarized. Finally, a summary and perspective of the existing challenges and future opportunities are presented. This review aims to deliver some insights into plasmonic photocatalysis from the perspective of active sites, expediting the discovery of high-performance plasmonic photocatalysts.

General approach to surface-accessible plasmonic Pickering emulsions for SERS sensing and interfacial catalysis

Pickering emulsions represent an important class of functional materials with potential applications in sustainability and healthcare. Currently, the synthesis of Pickering emulsions relies heavily on the use of strongly adsorbing molecular modifiers to tune the surface chemistry of the nanoparticle constituents. This approach is inconvenient and potentially a dead-end for many applications since the adsorbed modifiers prevent interactions between the functional nanosurface and its surroundings. Here, we demonstrate a general modifier-free approach to construct Pickering emulsions by using a combination of stabilizer particles, which stabilize the emulsion droplet, and a second population of unmodified functional particles that sit alongside the stabilizers at the interface. Freeing Pickering emulsions from chemical modifiers unlocks their potential across a range of applications including plasmonic sensing and interfacial catalysis that have previously been challenging to achieve. More broadly, this strategy provides an approach to the development of surface-accessible nanomaterials with enhanced and/or additional properties from a wide range of nano-building blocks including organic nanocrystals, carbonaceous materials, metals and oxides.

Cu-In-S/ZnS:Gd3+ quantum dots with isolated fluorescent and paramagnetic modules for dual-modality imaging in vivo

Gd³⁺-doped quantum dots (QDs) have been widely used as small-sized bifunctional contrast agents for fluorescence/magnetic resonance (FL/MR) dual-modality imaging. However, Gd³⁺ doping will always compromise the FL of host QDs. Therefore, balancing the Gd³⁺ doping and the optical properties of QDs is crucial for constructing high-performance bifunctional nanoprobes. Additionally, most paramagnetic QDs are synthesized in the organic phase and need to be transferred to the aqueous phase for bioimaging. Herein, ingeniously designed shell-doped Cu-In-S/ZnS:Gd³⁺ QDs have been prepared in the aqueous phase. It has been demonstrated that isolating paramagnetic Gd³⁺ from fluorescent Cu-In-S core via doping Gd³⁺ into ZnS shell not only avoided the decrease of FL quantum yield (QY), but also ensured the water accessibility of paramagnetic Gd³⁺ ions, by which the FL QY and r₁ relaxivity of Cu-In-S/ZnS:Gd³⁺ QDs achieved as much as 15.6% and 15.33 mM^-1·s^-1, respectively. These high-performance QDs with excellent stability, low biotoxicity, and good tumor permeability were successfully applied for in vivo tumor FL/MR dual-modality imaging, and have shown significant potential in the precision detection and diagnosis of diseases.

Plasmon enhanced catalysis-driven nanomotors with autonomous navigation for deep cancer imaging and enhanced radiotherapy

Radiosensitizers potentiate the radiotherapy effect while effectively reducing the damage to healthy tissues. However, limited sample accumulation efficiency and low radiation energy deposition in the tumor significantly reduce the therapeutic effect. Herein, we developed multifunctional photocatalysis-powered dandelion-like nanomotors composed of amorphous TiO2 components and Au nanorods (∼93 nm in length and ∼16 nm in outer diameter) by a ligand-mediated interface regulation strategy for NIR-II photoacoustic imaging-guided synergistically enhanced cancer radiotherapy. The non-centrosymmetric nanostructure generates stronger local plasmonic near-fields close to the Au-TiO2 interface. Moreover, the Au-TiO2 Schottky heterojunction greatly facilitates the separation of photogenerated electron-hole pairs, enabling hot electron injection, finally leading to highly efficient plasmon-enhanced photocatalytic activity. The nanomotors exhibit superior motility both in vitro and in vivo, propelled by H2 generated via NIR-catalysis on one side of the Au nanorod, which prevents them from returning to circulation and effectively improves the sample accumulation in the tumor. Additionally, a high radiation dose deposition in the form of more hydroxyl radical generation and glutathione depletion is authenticated. Thus, synergistically enhanced radiotherapeutic efficacy is achieved in both a subcutaneous tumor model and an orthotopic model.

Germanene-modified chitosan hydrogel for treating bacterial wound infection: An ingenious hydrogel-assisted photothermal therapy strategy

The elaborate design of an ingenious hydrogel-assisted photothermal therapy (PTT) platform is a promising strategy for treating bacterial wound infections. Herein, a new generation of germanene nanocrystals (Ge NCs) with excellent photothermal performance are prepared via an ice-bath sonication liquid-phase exfoliation technique. Whereafter, by crosslinking interaction between chitosan and zinc acetate, as well as self-assembly property between Ge NCs and chitosan, we successfully construct an innovative germanene-modified chitosan antimicrobial hydrogel (CS/Ge NCs^0.8) integrating capture and killing bacteria performances. When co-cultured with bacteria, CS/Ge NCs^0.8 hydrogel with the positive charge can adsorb and restrict bacteria in the range of PTT destruction. Once the near-infrared laser is introduced, CS/Ge NCs^0.8 hydrogel will effectively convert light energy into localized heat, further inducing bacterial death. By this entirely novel modality, CS/Ge NCs^0.8 hydrogel exhibits marvelous antibacterial property against E. coli and S. aureus in vitro. Furthermore, in vivo studies demonstrate that CS/Ge NCs^0.8 hydrogel possesses the ability to significantly rescue S. aureus-induced skin wound infections, suggesting CS/Ge NCs^0.8 hydrogel can be served as an antibacterial dressing. Strikingly, this is the first-ever report of CS/Ge NCs^0.8 hydrogel in the antibacterial field, which may spur a wave of developing Ge-based biomaterials to benefit biomedical applications.

Advances in Electrostatic Spinning of Polymer Fibers Functionalized with Metal-Based Nanocrystals and Biomedical Applications

Considering the metal-based nanocrystal (NC) hierarchical structure requirements in many real applications, starting from basic synthesis principles of electrostatic spinning technology, the formation of functionalized fibrous materials with inorganic metallic and semiconductor nanocrystalline materials by electrostatic spinning synthesis technology in recent years was reviewed. Several typical electrostatic spinning synthesis methods for nanocrystalline materials in polymers are presented. Finally, the specific applications and perspectives of such electrostatic spun nanofibers in the biomedical field are reviewed in terms of antimicrobial fibers, biosensing and so on.

Recent Advancements on Photothermal Conversion and Antibacterial Applications over MXenes-Based Materials

HIGHLIGHTS

Fabrication, characterizations and photothermal properties of MXenes are systematically described. Photothermal-derived antibacterial performances and mechanisms of MXenes-based materials are summarized and reviewed. Recent advances in the derivative applications relying on antibacterial properties of MXenes-based materials, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics, are investigated.

ABSTRACT

The pernicious bacterial proliferation and emergence of super-resistant bacteria have already posed a great threat to public health, which drives researchers to develop antibiotic-free strategies to eradicate these fierce microbes. Although enormous achievements have already been achieved, it remains an arduous challenge to realize efficient sterilization to cut off the drug resistance generation. Recently, photothermal therapy (PTT) has emerged as a promising solution to efficiently damage the integrity of pathogenic bacteria based on hyperthermia beyond their tolerance. Until now, numerous photothermal agents have been studied for antimicrobial PTT. Among them, MXenes (a type of two-dimensional transition metal carbides or nitrides) are extensively investigated as one of the most promising candidates due to their high aspect ratio, atomic-thin thickness, excellent photothermal performance, low cytotoxicity, and ultrahigh dispersibility in aqueous systems. Besides, the enormous application scenarios using their antibacterial properties can be tailored via elaborated designs of MXenes-based materials. In this review, the synthetic approaches and textural properties of MXenes have been systematically presented first, and then the photothermal properties and sterilization mechanisms using MXenes-based materials are documented. Subsequently, recent progress in diverse fields making use of the photothermal and antibacterial performances of MXenes-based materials are well summarized to reveal the potential applications of these materials for various purposes, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics. Last but not least, the current challenges and future perspectives are discussed to provide theoretical guidance for the fabrication of efficient antimicrobial systems using MXenes. [Image: see text]

Synergetic Dual-Atom Catalysts: The Next Boom of Atomic Catalysts

Dual-atom catalysts (DACs) are an important branch of single-atom catalysts (SACs), in which the former can effectively break the dilemma faced by the traditional SACs. The synergetic effects between bimetallic atoms provide many active sites, promising to improve catalytic performance and even catalyze more complex reactions. This paper reviews the recent research progresses of two kinds of DACs, including homonuclear and heteronuclear DACs, and their applications in oxygen reduction, carbon dioxide reduction, hydrogen evolution, oxygen evolution, Zn-air batteries, tandem catalytic reactions, and so on. In addition, in order to promote the further development of DACs, the challenges and perspectives of DACs are put forward.

Harnessing immune response using reactive oxygen Species-Generating/Eliminating inorganic biomaterials for disease treatment

With the increasing understanding of various biological functions mediated by reactive oxygen species (ROS) in the immune system, a number of studies have been designed to develop ROS-generating/eliminating strategies to selectively modulate immunogenicity for disease treatment. These strategies potentially exploit ROS-modulating inorganic biomaterials to harness host immunity to maximize the therapeutic potency by eliciting a favorable immune response. Inorganic biomaterial-guided in vivo ROS scavenging can exhibit several effects to: i) reduce the secretion of pro-inflammatory factors, ii) induce the phenotypic transition of macrophages from inflammatory M1 to immunosuppressive M2 phase, iii) minimize the recruitment and infiltration of immune cells. and/or iv) suppress the activation of nuclear factor kappa-B (NF-κB) pathway. Inversely, ROS-generating inorganic biomaterials have been found to be capable of: i) inducing immunogenic cell death (ICD), ii) reprograming tumor-associated macrophages from M2 to M1 phenotypes, iii) activating inflammasomes to stimulate tumor immunogenicity, and/or iv) recruiting phagocytes for antimicrobial therapy. This review provides a systematic and up-to-date overview on the progress related to ROS-nanotechnology mediated immunomodulation. We highlight how the ROS-generating/eliminating inorganic biomaterials can converge with immunomodulation and ultimately elicit an effective immune response against inflammation, autoimmune diseases, and/or cancers. We expect that contents presented in this review will be beneficial for the future advancements of ROS-based nanotechnology and its potential applications in this evolving field.

A cationic BODIPY photosensitizer decorated with quaternary ammonium for high-efficiency photodynamic inhibition of bacterial growth

On account of the constant evolution of antibiotic-resistant bacteria, the effects of existing antibacterial materials are being gradually weakened, and the difficulty in curing infectious diseases is increasing. Therefore, more novel antibacterial materials or methods are eagerly required to combat microbial infections. Recently, the advantages of photodynamic therapy in the antibacterial field have gradually been validated. Herein, a trimethylamine (TMA) salt-modified 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) photosensitizer (BODIPY-TMA) was synthesized for antibacterial applications. Due to the positive charge of the TMA group, enhanced interactions were observed between the prepared BODIPY-TMA nanoparticles (BODIPY-TMA NPs) and negatively-charged bacterial membranes. The BODIPY-TMA NPs showed much better antibacterial effect toward both S. aureus and E. coli compared with their BODIPY-Br NPs counterpart without a positive charge. Moreover, the BODIPY-TMA NPs efficiently prevented the formation of biofilms and destroyed pre-established biofilms. Thus, such positively-charged photosensitizers may pave the way for the exploration of highly effective antibacterial agents.

Defect engineering of layered double hydroxide nanosheets as inorganic photosensitizers for NIR-III photodynamic cancer therapy

Although two-dimensional (2D) layered double hydroxides (LDHs) have been widely used as efficient nanoagents for biological diagnosis and treatment, they have been found to be inert as photosensitizers (PSs) for photodynamic therapy (PDT). Herein, we report the defect engineering of ultrathin 2D CoMo-LDH and NiMo-LDH nanosheets as highly active inorganic PSs for PDT in the third near-infrared (NIR-III) window. Hydrothermal-synthesized 2D CoMo-LDH and NiMo-LDH nanosheets are etched via a simple acid treatment to obtain defect-rich CoMo-LDH and NiMo-LDH nanosheets. Importantly, the defect-rich CoMo-LDH nanosheets exhibit much higher activity (~97 times) for generation of reactive oxygen species than that of the pristine CoMo-LDH nanosheets under a NIR-III 1567 nm laser irradiation. Therefore, after modification with polyethylene glycol, the defect-rich CoMo-LDH nanosheets can be used as an efficient inorganic PS for PDT to efficiently induce cancer cells apoptosis in vitro and eradicate tumors in vivo under 1567 nm laser irradiation.

Defect engineering of 2 dimensional layered double hydroxide sheets improves their photocatalytic activity. Here, the authors etch sheets in acid and show that the etched sheets generate substantially more reactive oxygen species that untreated sheets and the treated sheets can be used to kill cancer cells in vitro and in vivo.

A porphyrin-based metallacage for enhanced photodynamic therapy

In this study, we designed an effective nanoplatform to improve the photodynamic therapy (PDT) of porphyrins. Combining a porphyrin-based metallacage (PM), hyaluronidase (HAase) and DSPE-mPEG2000 together, the nanoparticle (PM@HAase-mPEG) showed enhanced PDT efficacy. The PM improved the stability of the porphyrin, avoided its aggregation and provided cavities to concentrate oxygen molecules, which was beneficial for enhancing PDT. HAase degraded HA to increase the intracellular accumulation of nanoparticles, normalized blood vessels and relieved hypoxia in tumors. PM@HAase-mPEG inhibited the growth of tumors in a 4T1 mouse model by the generated singlet oxygen with excellent PDT efficacy. This study resolved the problems of the instability of PSs, less cellular accumulation of drugs, and tumor hypoxia that limited the anti-tumor application of PDT.

NIR-II Hydrogen-Bonded Organic Frameworks (HOFs) Used for Target-Specific Amyloid-β Photooxygenation in an Alzheimer's Disease Model

Phototherapy has emerged as a powerful approach for interrupting β-amyloid (Aβ) self-assembly. However, deeper tissue penetration and safer photosensitizers are urgent to be exploited for avoiding damaging nearby normal tissues and improving therapeutic effectiveness. A hydrogen-bonded organic framework (HOF)-based NIR-II photooxygenation catalyst is presented here to settle the abovementioned challenges. By encapsulating the pyridinium hemicyanine dye DSM with a large two-photon absorption (TPA) cross-section in NIR-II window into the porphyrin-based HOF, the resultant DSM@n-HOF-6 exhibits significant two-photon NIR-II-excited Fluorescence Resonance Energy Transfer (FRET) to generate singlet oxygen (1 O2 ) for Aβ oxidation. Further, the target peptides of KLVFFAED (KD8) are covalently grafted on DSM@n-HOF-6 to enhance the blood-brain barrier (BBB) permeability and Aβ selectivity. The HOF-based photooxygenation catalyst shows an outstanding inhibitory effect of Aβ aggregation upon the NIR-II irradiation. Further in vivo studies demonstrate the obvious decrease of craniocerebral Aβ plaques and recovery of memory deficits in triple-transgenic AD (3×Tg-AD) model mice.

Anisotropic Plasmonic Pd-Tipped Au Nanorods for Near-Infrared Light-Activated Photoacoustic Imaging Guided Photothermal-Photodynamic Cancer Therapy

The integration of photothermal therapy (PTT) and photodynamic therapy (PDT) has become a promising cancer treatment method. Herein, anisotropic metal hetero-nanostructure Pd-tipped Au nanorods (PTA NRs) were fabricated, which exhibit...

Bacterial microenvironment-responsive dual-channel smart imaging guided on-demand self-regulated photodynamic/chemodynamic synergistic sterilization and wound healing

Bacterial infections pose a serious threat to public health. The integration of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has emerged as a promising means to combat bacterial infection. However,...

Enhancing the antibacterial activity of near-infrared light-triggered photothermal therapy using hybrid Au/ZnSe nanodumbbells

Hybrid plasmonic Au/ZnSe nanodumbbell heterostructures prevent the contact of hot electrons with the surrounding medium, resulting in higher PT conversion efficiency.

AIE-active Ir(iii) complexes functionalised with a cationic Schiff base ligand: synthesis, photophysical properties and applications in photodynamic therapy

Two AIE-active Ir(iii) cationic complexes containing Schiff base ligands were synthesised. Ir-2-N+ NPs are shown to be good PSs in vitro for PDT.

Stimulus-responsive nanomaterials under physical regulation for biomedical applications

Cancer is a growing threat to human beings. Traditional treatments for malignant tumors usually involve invasive means to healthy human tissues, such as surgical treatment and chemotherapy. In recent years the use of specific stimulus-responsive materials in combination with some non-contact, non-invasive stimuli can lead to better efficacy and has become an important area of research. It promises to develop personalized treatment systems for four types of physical stimuli: light, ultrasound, magnetic field, and temperature. Nanomaterials that are responsive to these stimuli can be used to enhance drug delivery, cancer treatment, and tissue engineering. This paper reviews the principles of the stimuli mentioned above, their effects on materials, and how they work with nanomaterials. For this aim, we focus on specific applications in controlled drug release, cancer therapy, tissue engineering, and virus detection, with particular reference to recent photothermal, photodynamic, sonodynamic, magnetothermal, radiation, and other types of therapies. It is instructive for the future development of stimulus-responsive nanomaterials for these aspects.

Implications of photodynamic cancer therapy: an overview of PDT mechanisms basically and practically

BACKGROUND

Tumor eradication is one of the most important challengeable categories in oncological studies. In this account, besides the molecular genetics methods including cell therapy, gene therapy, immunotherapy, and general cancer therapy procedures like surgery, radiotherapy, and chemotherapy, photodynamic adjuvant therapy is of great importance. Photodynamic therapy (PDT) as a relatively noninvasive therapeutic method utilizes the irradiation of an appropriate wavelength which is absorbed by a photosensitizing agent in the presence of oxygen. In this procedure, a series of events lead to the direct death of malignant cells such as damage to the microvasculature and also the induction of a local inflammatory function. PDT has participated with other treatment modalities especially in the early stage of malignant tumors and has resulted in decreasing morbidity besides improving survival rate and quality of life. High spatial resolution of PDT has attracted considerable attention in the field of image-guided photodynamic therapy combined with chemotherapy of multidrug resistance cancers. Although PDT outcomes vary across the different tumor types, minimal natural tissue toxicity, minor systemic effects, significant reduction in long-term disease, lack of innate or acquired resistance mechanisms, and excellent cosmetic effects, as well as limb function, make it a valuable treatment option for combination therapies.

SHORT CONCLUSION

In this review article, we tried to discuss the potential of PDT in the treatment of some dermatologic and solid tumors, particularly all its important mechanisms.

Multifunctional BODIPY for effective inactivation of Gram-positive bacteria and promotion of wound healing

Bacterial infectious diseases and antimicrobial resistance seriously endanger human health, so alternative therapies for bacterial infections are urgently needed. Recently, photodynamic therapy against bacteria has shown great potential because of its high efficiency and low acquired resistance. Here, we design and synthesize a dipyrromethene boron difluoride (BODIPY) photosensitizer containing a guanidine group LIBDP for combating bacterial infections. The positively charged guanidine can destroy the bacterial membrane and inhibit the proliferation of bacteria to a certain extent. Upon light irradiation, LIBDP can produce reactive oxygen species (ROS), which can destroy the pre-formed biofilm and induce potent antibacterial activity. In addition, the guanidine of LIBDP can be oxidized to nitric oxide (NO) by the generated ROS, which can not only improve the antibacterial effect, but also promote wound healing. The strategy in this work paves the way for synthesizing high-performance antibacterial materials.