Search

Bacterial infection of wounds delays the healing process, increases the risk of chronic trauma associated with pain and complications, and offers a breeding ground for drug-resistant bacteria. A rapid and effective eradication of the bacterial species in the wound area is thus important. Herein, we designed a phototherapeutic antibacterial platform based on peptides and copper sulfide nanodots (CuS NDs) for multi-mechanistic eradication of bacteria colonized on the wound surface. The antimicrobial peptide weaves into a network in the form of a hydrogel, which supports CuS NDs to generate heat and produce reactive oxygen species (ROS) under the irradiation of near-infrared light (NIR). The heat and ROS generated

Nanozymes, a type of nanomaterials that function similarly to natural enzymes, receive extensive attention in biomedical fields. However, the widespread applications of nanozymes are greatly plagued by their unsatisfactory enzyme-mimicking activity. Localized surface plasmon resonance (LSPR), a nanoscale physical phenomenon described as the collective oscillation of surface free electrons in plasmonic nanoparticles under light irradiation, offers a robust universal paradigm to boost the catalytic performance of nanozymes. Plasmonic nanozymes (PNzymes) with elevated enzyme-mimicking activity by leveraging LSPR, emerge and provide unprecedented opportunities for biocatalysis. In this review, the physical mechanisms behind PNzymes are thoroughly revealed including near-field enhancement, hot carriers, and the photothermal effect. The rational design and applications of PNzymes in biosensing, cancer therapy, and bacterial infections elimination are systematically introduced. Current challenges and further perspectives of PNzymes are also summarized and discussed to stimulate their clinical translation. It is hoped that this review can attract more researchers to further advance the promising field of PNzymes and open up a new avenue for optimizing the enzyme-mimicking activity of nanozymes to create superior nanocatalysts for biomedical applications.

Intranasal administration, which can bypass the blood–brain barrier (BBB), is widely recognized as a promising strategy for high-efficiency drug delivery to the brain. Herein, for the purpose of effectively delivering drugs to the brain via intranasal administration, glutathione (GSH)-modified gellan gum (GSH-GG) with ion/temperature dual responsive properties was synthesized and encapsulated on galanthamine hydrobromide (GH)-loaded liposomes (GH-Lipo) for effective GH delivery to the brain (GH-Lipo@GSH-GG). Our results demonstrated that GSH-GG greatly decreased the gelation temperature of GG from 44.0 °C to 22.1 °C without compromising its ion responsiveness. Moreover, GSH-GG had a good protection ability for GH-loaded liposomes without affecting its drug release. Most importantly, the finally obtained GH-Lipo@GSHGG showed acceptable targeted delivery of GH to the brain upon in vivo administration. Therefore, this formulation can be employed as a potential delivery system in nasal-to-brain delivery.

Damage or injury to the skin creates wounds that are vulnerable to bacterial infection, which in turn retards the process of skin regeneration and wound healing. In patients with severe burns and those with chronic diseases, such as diabetes, skin infection by multidrug-resistant bacteria can be lethal. Therefore, a broad-spectrum therapy to effectively eradicate bacterial infection through a mechanism different from that of antibiotics is much sought after. We successfully synthesized antibacterial photodynamic gold nanoparticles (AP-AuNPs), which are self-assembled nanocomposites of an antibacterial photodynamic peptide and poly(ethylene glycol) (PEG)-stabilized AuNPs. The AP-AuNPs exhibited aqueous and light stability, a satisfactory generation of reactive oxygen species (ROS), and a remarkable antibacterial effect toward both Gram-positive

Staphylococcus aureus (S. aureus) related staphylococcal infection is one of the most common types of hospital-acquired infections, which requires selective and effective treatment in clinical practice. Considering gelatinase as a characteristic feature of S. aureus, gelatinase-responsive release of the antibiotic reagent thereby can target the pathogenic S. aureus while sparing beneficial bacteria in the microflora. In this work, we design a hybrid antibacterial photodynamic peptide (APP, Ce6-GKRWWKWWRRPLGVRGC) based on the polycationic antimicrobial peptide GKRWWKWWRR by introducing a photosensitizer chlorin e6 (Ce6) at the N-terminus, a cysteine residue at the C-terminus, and a gelatinase cleavage site (PLGVRG) inserted between the C-terminal cysteine and the polycationic peptide. This multi-motif peptide assembles with gold nanoclusters (AuNc) via Au–thiol bonding and affords a gelatinase-responsive antibacterial photodynamic nanocomposite (GRAPN). In vitro results show that the gelatinase secreted by S. aureus can cleave and release APP from AuNc, thereby resulting in preferential killing of S. aureus over E. coli. In a mouse model of staphylococcal skin wound infection, by integrating gelatinase-responsive drug release and the synergistic effect of a photodynamic agent and APP, GRAPN exhibits a marked photodynamic antibacterial activity, effectively eradicates S. aureus infection, and promotes rapid healing of the infected wounds.

Sensitive diagnosis and elimination of multidrug-resistant bacterial infections at an early stage remain paramount challenges. Herein, we present a gelatinase-responsive turn-on nanoprobe for in situ near-infrared (NIR) fluorescence imaging and localized photothermal treatment (PTT) of in vivo methicillin-resistant Staphylococcus aureus (MRSA) infections. The designed nanoprobe (named AuNS-Apt-Cy) is based on gold nanostars functionalized with MRSA-identifiable aptamer and gelatinase-responsive heptapeptide linker (CPLGVRG)-cypate complexes. The AuNS-Apt-Cy nanoprobe is non-fluorescent in aqueous environments due to the fluorescence resonance energy transfer between the gold nanostar core and cypate dye. We demonstrate that the AuNS-Apt-Cy nanoprobe can achieve MRSA targeting and accumulation as well as gelatinase (overexpressed in MRSA environments)-responsive turn-on NIR fluorescence due to the cleavage of the CPLGVRG linker and localized in vitro PTT via a mechanism involving bacterial cell wall and membrane disruption. In vivo experiments show that the AuNS-Apt-Cy nanoprobe can enable rapid (1 h post-administration) and in situ turn-on NIR fluorescence imaging with high sensitivity (105 colony-forming units) in diabetic wound and implanted bone plate mouse models. Remarkably, the AuNS-Apt-Cy nanoprobe can afford efficient localized PTT of diabetic wound and implanted bone plate-associated MRSA infections under the guidance of turn-on NIR fluorescence imaging, showing robust capability for early diagnosis and treatment of in vivo MRSA infections. In addition, the nanoprobe exhibits negligible damage to surrounding healthy tissues during PTT due to its targeted accumulation in the MRSA-infected site, guaranteeing its excellent in vivo biocompatibility and solving the main bottlenecks that hinder the clinical application of PTT-based antibacterial strategies.

The emergence of bacterial resistance due to the evolution of microbes under antibiotic selection pressure, and their ability to form biofilm, has necessitated the development of alternative antimicrobial therapeutics. Physical stimulation, as a powerful antimicrobial method to disrupt microbial structure, has been widely used in food and industrial sterilization. With advances in nanotechnology, nanophysical antimicrobial strategies (NPAS) have provided unprecedented opportunities to treat antibiotic-resistant infections, via a combination of nanomaterials and physical stimulations. In this review, NPAS are categorized according to the modes of their physical stimulation, which include mechanical, optical, magnetic, acoustic, and electrical signals. The biomedical applications of NPAS in combating bacterial infections are systematically introduced, with a focus on their design and antimicrobial mechanisms. Current challenges and further perspectives of NPAS in the clinical treatment of bacterial infections are also summarized and discussed to highlight their potential use in clinical settings. The authors hope that this review will attract more researchers to further advance the promising field of NPAS, and provide new insights for designing powerful strategies to combat bacterial resistance.

Reactive oxygen species (ROS) are the weapons of neutrophiles against bacterial pathogens, and also the central effectors in reactive oxygen therapy for skin and soft tissue infection. Nanozymes that spontaneously generate ROS under physiological conditions are new antibacterials that hold promise towards multidrug resistant pathogens. The clinical use of the nanozymes is however limited by their low biocompatibility and toxicity in vivo. Here, we develop an oleic acid (OA) nanoemulsion template method for the one-pot synthesis of OA-manganese dioxide (MnO2) nanozyme. The OA-MnO2 nanozyme showed high stability and biocompatibility under physiological conditions with marked oxidase-like activity. The ROS generated by the OA-MnO2 nanozyme effectively kill the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli strains. Moreover, the OA-MnO2 nanozyme shows promising abilities to prevent and destruct biofilm formation by Staphylococcus aureus, and result in superior in vivo antibacterial performance as compared to vancomycin. The reactive oxygen therapy based on OA-MnO2 nanozyme cures the infected skin and promotes wound healing in mice, manifesting its potential use in skin and soft tissue infection.

Staphylococcus aureus (S. aureus) related staphylococcal infection is one of the most common types of hospital-acquired infections, which requires selective and effective treatment in clinical practice. Considering gelatinase as a characteristic feature of S. aureus, gelatinase-responsive release of the antibiotic reagent thereby can target the pathogenic S. aureus while sparing beneficial bacteria in the microflora. In this work, we design a hybrid antibacterial photodynamic peptide (APP, Ce6-GKRWWKWWRRPLGVRGC) based on the polycationic antimicrobial peptide GKRWWKWWRR by introducing a photosensitizer chlorin e6 (Ce6) at the N-terminus, a cysteine residue at the C-terminus, and a gelatinase cleavage site (PLGVRG) inserted between the C-terminal cysteine and the polycationic peptide. This multi-motif peptide assembles with gold nanoclusters (AuNc) via Au-thiol bonding and affords a gelatinase-responsive antibacterial photodynamic nanocomposite (GRAPN). In vitro results show that the gelatinase secreted by S. aureus can cleave and release APP from AuNc, thereby resulting in preferential killing of S. aureus over E. coli. In a mouse model of staphylococcal skin wound infection, by integrating gelatinase-responsive drug release and the synergistic effect of a photodynamic agent and APP, GRAPN exhibits a marked photodynamic antibacterial activity, effectively eradicates S. aureus infection, and promotes rapid healing of the infected wounds.

Biofilm infections can induce chronic inflammation and stall the normal orchestrated course of wound-healing cascades. Herein, pH-switchable antimicrobial hydrogel with nanofiber networks for biofilm eradication and rescuing stalled healing in chronic wounds is reported on the basis of the self-assembly of a designed octapeptide (IKFQFHFD) at neutral pH. This hydrogel is biocompatible and exhibits an acidic pH (pathological environment of infected chronic wounds)-switchable broad-spectrum antimicrobial effect via a mechanism involving cell wall and membrane disruption. The antimicrobial activity of hydrogel is derived from its acidic pH-dependent nanofiber network destabilization and activated release of IKFQFHFD, which is antimicrobial only at acidic pH due to the antimicrobial peptide-like molecular structure. In addition, supramolecular nanofiber networks loaded with drugs of cypate (photothermal agent) and proline (procollagen component) are further developed. In vitro experiments show that loaded drugs exhibit acidic pH (pH ∼ 5.5)-responsive release profiles, and synergistic biofilm eradication and subsequent healing cascade activation of cells proliferation are achieved on the basis of the supramolecular nanofiber networks. Remarkably, the nanofiber networks of hydrogel enable in vivo complete healing of MRSA biofilm infected wound in diabetic mice within 20 days, showing great potential as promising chronic wound dressings. The proposed synergistic strategy for eradicating biofilm and activating subsequent healing cascades may offer a powerful modality for the management of clinical chronic wounds.

Bacterial infections pose mounting public health concerns and cause an enormous medical and financial burden today. Rapid and sensitive detection of pathogenic bacteria at the point of care (POC) remains a paramount challenge. Here, we report a novel concept of bacteria-instructed click chemistry and employ it for POC microbial sensing. In this concept of bacteria-instructed click chemistry, we demonstrate for the first time that pathogenic bacteria can capture and reduce exogenous Cu2+ to Cu+ by leveraging their unique metabolic processes. The produced Cu+ subsequently acts as a catalyst to trigger the click reaction between gold nanoparticles (AuNPs) modified with azide and alkyne functional molecules, resulting in the aggregation of nanoparticles with a color change of the solution from red to blue. In this process, signal amplification from click chemistry is complied with the aggregation of functionalized AuNPs, thus presenting a robust colorimetric strategy for sensitive POC sensing of pathogenic bacteria. Notably, this colorimetric strategy is easily integrated in a smartphone app as a portable platform to achieve one-click detection in a mobile way. Moreover, with the help of the magnetic preseparation process, this smartphone app-assisted platform enables rapid (within 1 h) detection of Escherichia coli with high sensitivity (40 colony-forming units/mL) in the complex artificial sepsis blood samples, showing great potential for clinical early diagnosis of bacterial infections.

Nano-radiosensitizers provide a powerful tool for cancer radiation therapy. However, their limited tumor retention/penetration and the inherent or adaptive radiation resistance of tumor cells hamper the clinical success of radiation therapy. Herein, we report a synergistic strategy for potentiated cancer radiation/gene therapy based on transformable gold nanocluster aggregates loaded with antisense oligonucleotide-targeting survivin mRNA (named AuNC-ASON). AuNC-ASON exhibited acidic pH-triggered structure splitting from a gold nanocluster aggregate (around 80 nm) to gold nanocluster (

As the barrier between the human body and the outside world, the skin is vulnerable to pathogenic microorganisms, especially when suffering from skin injuries such as burns. Staphylococcus aureus remains the most common type of bacteria that infects humans, and the surging drug resistance poses a major threat to the treatment of these infections. Here we report the development of antibacterial photodynamic peptides (APPs) that are constructed based on the covalent conjugation of an antibacterial peptide and the photosensitizer chlorin e6 (Ce6). Peptide conjugation significantly increases the photo-stability of Ce6, while retaining its ROS generation capability under photo-irradiation. The APPs combine the antibacterial activity of the peptide and the photodynamic therapy of Ce6, and under the assistance of mild laser irradiation, can eradicate bacterial infection and inhibit the formation of bacterial biofilms ex vivo. One of the APPs, (GKRWWKWWRR)2KGGK(Ce6)G, AMP2-Ce6, with Ce6 conjugated with the dimeric peptide, showed exceptional antibacterial activity with an MIC90 value around 3.2 μM without photo-irradiation and

Sensitive diagnosis and elimination of multidrug-resistant bacterial infections at an early stage remain paramount challenges. Herein, we present a gelatinase-responsive turn-on nanoprobe for in situ near-infrared (NIR) fluorescence imaging and localized photothermal treatment (PTT) of in vivo methicillin-resistant Staphylococcus aureus (MRSA) infections. The designed nanoprobe (named AuNS-Apt-Cy) is based on gold nanostars functionalized with MRSA-identifiable aptamer and gelatinase-responsive heptapeptide linker (CPLGVRG)-cypate complexes. The AuNS-Apt-Cy nanoprobe is non-fluorescent in aqueous environments due to the fluorescence resonance energy transfer between the gold nanostar core and cypate dye. We demonstrate that the AuNS-Apt-Cy nanoprobe can achieve MRSA targeting and accumulation as well as gelatinase (overexpressed in MRSA environments)-responsive turn-on NIR fluorescence due to the cleavage of the CPLGVRG linker and localized in vitro PTT via a mechanism involving bacterial cell wall and membrane disruption. In vivo experiments show that the AuNS-Apt-Cy nanoprobe can enable rapid (1 h post-administration) and in situ turn-on NIR fluorescence imaging with high sensitivity (105 colony-forming units) in diabetic wound and implanted bone plate mouse models. Remarkably, the AuNS-Apt-Cy nanoprobe can afford efficient localized PTT of diabetic wound and implanted bone plate-associated MRSA infections under the guidance of turn-on NIR fluorescence imaging, showing robust capability for early diagnosis and treatment of in vivo MRSA infections. In addition, the nanoprobe exhibits negligible damage to surrounding healthy tissues during PTT due to its targeted accumulation in the MRSA-infected site, guaranteeing its excellent in vivo biocompatibility and solving the main bottlenecks that hinder the clinical application of PTT-based antibacterial strategies.

Solar cavity receiver is one of the most crucial components in a solar power tower system, where the solar-thermal conversion process is achieved. Optimizing the surface properties (viz. absorptivity and emissivity) of a designed cavity receiver is a viable option to improve its thermal efficiency. In the present paper, an integrated simulation approach was employed to quantify the influence of surface optical and radiative properties on the thermal performance of a typical water/steam solar cavity receiver. Firstly, the different candidate surface materials, solar selective and non-coated, were compared. The results showed that the thermal efficiency of the receiver with the ideal coating and Pyromark 2500 is respectively enhanced by 12.5% and 7.8% compared with that of the non-coated receiver. And then, the effects of surface spectral selectivity on the thermal performance of the receiver were carefully analyzed. It can be found that the solar absorptivity is the most critical parameter for improving the receiver efficiency, which is enhanced by about 12.6% as the solar absorptivity rises from 0.8 to 1.0. However, the receiver efficiency shows different variation tendencies with the thermal emissivity of active surfaces, which are closely related to the infrared heat transfer direction between the passive surfaces and the active surfaces. Furthermore, with the increase of reflectivity of passive surfaces over the full spectrum, the receiver efficiency is determined by a trade-off between the increasing reflective heat loss and the decreasing radiative and convective heat losses. For the present receiver, the thermal efficiency is improved by about 4.8% with the reflectivity increasing from 0 to 1.0 due to its great cavity effect. Therefore, the passive surfaces should be highly reflective throughout the spectrum inside the present receiver.

A nanowire-integrated thermoresponsive microfluidic platform is developed for bacterial enrichment and on-demand release. This microfluidic platform can enable selective and highly sensitive S. aureus detection in blood samples down to trace concentrations (40 CFU mL-1) by the naked eye with the help of a click reaction-assisted colorimetric assay.

The performance of cavity receiver plays a fatal role in light-heat conversion process in a concentrating solar power (CSP) plant. In our present work, an experimental platform is designed and built, in which a solar simulator consisting of seven mutually independent xenon lamp units is used for supplying the solar energy needed. The cold start-up and steady state performance of the cavity receiver were studied under 0.5MPa. The results show that for a certain cavity structure, temperatures on boiling panels and thus the heat loss can be affected not merely by the heat flux, other parameters can influence the temperature of absorbing surfaces, such as the heat transfer in the boiling tubes, fluid flow states and the wind effect, so the temperature distribution is highly non-uniform on boiling panels. However, the temperatures of passive surfaces depend greatly on the input solar energy, thus the heat losses of the passive surfaces will vary with the input energy. Overheat occurs if a high heat flux doesn’t have a sufficient heat transfer inside boiling tubes internal. The stagnation zone does exist in the cavity and its boundary varies with a different input energy, thus the convective heat loss can be affected. The cavity receiver thermal efficiency is 72.92% under 0.5MPa, may be the reason behind this low efficiency is the strong cooling wind of the solar simulator.

In recent years, traditional fossil fuels are constantly depleted, and the world is facing a serious energy crisis. Solar energy is a clean and abundant renewable energy resource which offers an option for solving the serious environmental problem caused by the consumption of the fossil energy. Among different forms of renewable energy, solar energy has also become an essential part of daily human life. Solar thermal power generation technology is regarded as one of the most potential power generation methods in the future. Solar thermal power generation technology is important to alleviate the energy crisis and to protect the ecological environment. Due to the intermittent of the solar energy, a conceivable way is to store it to provide the solar energy continuously. Thermal energy storage system is necessary for steady and continuous solar thermal power generation. In this paper, among the existing three kinds of solar thermal energy storage technology: sensible heat storage, latent heat storage system and thermochemical energy storage system, we analyzed the obvious advantages of thermochemical energy storage- high energy density and large scale storage and convenient remote transportation. The material or matrix chosen to act as solar thermochemical energy storage medium must meet the following criteria: high energy storage density, low charging temperature, higher rate of reaction, appropriate heat and mass transfer properties, easy to handle, low cost and thermal stability. According to these standards, we chose five suitable solar thermochemical energy storage systems, namely, methane reforming system, metal oxide system, metal hydride system, hydroxide system and amino thermochemical system. The latest research progress of the existing five kinds of thermochemical energy storage system were introduced on the reaction mechanism, reaction model and design of reactor by the numerical, experimental and technological study methods. Advantages and disadvantages of each system were analyzed. Based on the problems of reaction system, we put forward the main research directions of each thermochemical energy storage system. For methane reforming system, strengthening the heat transfer process in the reactor and the development of high performance catalysts or oxygen carriers are important. Furthermore, the combination of reforming reaction with methanation reaction to form energy storage cycle also need to develop. The problems of metal oxide system include too high temperature and high thermal hysteresis. Therefore, doped with other metal oxides may be a promising method. To improve the reaction rate of metal hydride system, the method of doping with other metal hydrides can also be carried out. The bottleneck of metal hydride system and the amino thermochemical system is too high hydrogen pressure, therefore the research on reactor structure for high efficient and low cost with large scale storage of hydrogen is necessary. The future research on hydroxide system should focus on the settlement of sintering and corrosion, so the particle design is important. In general, we pointed out that future research will mainly develop in two directions: greater scale and more detailed mechanism, specifically the construction of solar thermal energy storage demonstration system and a deeper and more detailed study of the mechanisms of heat and mass transfer coupling with chemical reaction.

Accurate tumor margin demarcation in situ remains a paramount challenge. Herein, a NanoFlare (also known as spherical-nucleic-acid technology) based strategy is reported for in situ tumor margin delineation by transforming and amplifying the pathophysiological redox signals of tumor microenvironment. The NanoFlare designed (named AuNS-ASON) is based on gold nanostar (AuNS) coated with a dense shell of disulfide bridge-inserted and cyanine dyes-labeled antisense oligonucleotides (ASON) targeting survivin mRNA. The unique anisotropic ASON-spike nanostructure endows the AuNS-ASON with universal cellular internalization of tumor cells, while the disulfide bridge inserted confers response specificity toward redox activation. In vitro experiments demonstrate that the AuNS-ASON can discriminate tumor cells rapidly with activated fluorescence signals (>100-fold) in 2 h, and further achieve synergistic gene/photothermal tumor cells ablation upon near-infrared laser irradiation. Remarkably, in situ tumor margin delineation with high accuracy and outstanding spatial resolution (