Bacteria-Activated Theranostic Nanoprobes against Methicillin-Resistant Staphylococcus aureus Infection

How nanomaterials act against bacterial structures? a narrative review focusing on nanoparticle molecular mechanisms

OBJECTIVE

In recent years, significant progress has been made in the field of nanotechnology for the treatment and prevention of biofilm formation and Multidrug-resistant bacteria (MDR). MDR bacteria challenges is hazardous when microorganisms induce the formation of biofilms, which amplify resistance to antibiotics and promote the development of multidrug-resistant conditions. The unique physicochemical properties of certain nanomaterials make nanotechnology a promising option for combating MDR infections. Several studies have introduced nanomaterials with different antibacterial mechanisms that can effectively destroy MDR bacteria and their biofilms. This study reviews the research results, focusing on the various nanoparticle mechanisms that target bacterial structures.

METHOD

To accomplish this study, we conducted investigations to gather articles and relevant studies from validated medical databases such as Scopus, PubMed, Google Scholar, and Web of Science. The selected publications from 2007 to 2023. In this review, we provide a brief overview of nanoparticles, their mechanisms, and how they function against the structure of bacteria. Furthermore, we discuss the recent advancements in using certain nanoparticles to combat infection-induced biofilms and complications caused by multidrug resistance.

FINDING

Our findings demonstrate that various nanoparticles have the potential to effectively overcome bacterial infectious diseases by targeting biofilms and antibiotic-resistant strains. Additionally, the development of a new drug delivery approach based on nanosystems shows promise in overcoming antibiotic resistance and biofilms.

Versatile self-assembled near-infrared SERS nanoprobes for multidrug-resistant bacterial infection-specific surveillance and therapy

The rise of multidrug-resistant bacteria (MDRB) has made bacterial infection one of the biggest health threats, causing numerous antibiotics to fail. Real-time monitoring of bacterial disease treatment efficacy at the infection site is required. Herein, we report a versatile Raman tag 3,3'-diethylthiatricarbocyanine iodide (DTTC)-conjugated star-shaped Au-MoS2@hyaluronic acid (AMD@HA) nanocomposite as a surface-enhanced Raman scattering (SERS) nanoprobe for quick bacterial identification and in-situ eradication. Localized surface plasmon resonance (LSPR) from the hybrid metallic nanostructure makes AMD@HA highly responsive to the near-infrared laser, enabling it to demonstrate a photothermal (PTT) effect, increased SERS activity, and peroxidase-like catalytic reaction to release reactive oxygen species. The tail vein injection of AMD@HA nanoprobes is invasive, however SERS imaging for bacterial identification is non-invasive and sensitive, making it an efficient residual bacteria monitoring method. The detection limit for methicillin-resistant Staphylococcus aureus (MRSA) is as low as 102 CFU·mL-1, and the substrates allow for taking 120 s to acquire a Raman image of 1600 (40 × 40) pixels. In mouse models of MRSA-induced wound infection and skin abscess, the combination of AMD@HA-mediated PTT and catalytic therapy demonstrates a synergistic effect in promoting wound healing through rapid sterilization. This SERS-guided therapeutic approach exhibits little toxicity and does not cause considerable collateral damage, offering a highly promising intervention for treating diseases caused by MDRB. STATEMENT OF SIGNIFICANCE: This research introduces a SERS nanoprobe, AMD@HA, for the rapid identification and eradication of multidrug-resistant bacteria (MDRB), a critical health threat. The nanoprobe leverages localized surface plasmon resonance for photothermal therapy and enhanced Raman signals, offering a sensitive, non-invasive diagnostic tool. With a low detection limit for MRSA and a synergistic therapeutic effect in mouse models, our approach holds significant promise for treating MDRB-driven infections with minimal toxicity, advancing the field of antimicrobial strategies.

Prevention and potential remedies for antibiotic resistance: current research and future prospects

The increasing threat of antibiotic resistance and shrinking treatment options for infections have pushed mankind into a difficult position. The looming threat of the return of the pre-antibiotic era has caused a sense of urgency to protect and conserve the potency of antibiotic therapy. One of the perverse effects of antibiotic resistance is the dissemination of its causative agents from non-clinically important strains to clinically important strains and vice versa. The popular saying "Prevention is better than cure" is appropriate for tackling antibiotic resistance. On the one hand, new and effective antibiotics are required; on the other hand, better measures for the use of antibiotics, along with increased awareness in the general public related to antibiotic use, are essential. Awareness, especially of appropriate antibiotic use, antibiotic resistance, its dissemination, and potential threats, can help greatly in controlling the use and abuse of antibiotics, and the containment of antibiotic resistance. Antibiotic drugs' effectiveness can be enhanced by producing novel antibiotic analogs or adding adjuvants to current antibiotics. Combinatorial therapy of antibiotics has proven successful in treating multidrug-resistant (MDR) bacterial infections. This review aims to highlight the current global situation of antibiotic resistance and discuss the methods used to monitor, prevent, inhibit, or reverse bacterial resistance mechanisms in the fight against antibiotic resistance.

Dysbiosis and diabetic foot ulcers: A metabolic perspective of Staphylococcus aureus infection

Staphylococcus aureus (S. aureus) infection is the most prevalent and resistant bacterial infection, posing a worldwide health risk. Compared with healthy people, diabetes patients with weak immune function and abnormal metabolism are more vulnerable to bacterial infection, which aggravates the intensity of infection and causes a series of common and dangerous complications, such as diabetes foot ulcer (DFU). Due to metabolic abnormalities of diabetic patients, S. aureus on the skin surface of DFU transitions from a commensal to an invasive infection. During this process, S. aureus resists a series of unfavorable conditions for bacterial growth by altering energy utilization and metabolic patterns, and secretes various virulence factors, causing persistent infection. With the emergence of multiple super-resistant bacteria, antibiotic treatment is no longer the only treatment option, and developing new drugs and therapies is urgent. Regulating the metabolic signaling pathway of S. aureus plays a decisive role in regulating its virulence factors and impacts adjuvant therapy for DFU. This article focuses on studying the impact of regulating metabolic signals on the virulence of S. aureus from a metabolism perspective. It provides an outlook on the future direction of the novel development of antimicrobial therapy.

Immunomodulation in Non-traditional Therapies for Methicillin-resistant Staphylococcus aureus (MRSA) Management

The rise of methicillin-resistant Staphylococcus aureus (MRSA) poses a significant challenge in clinical settings due to its ability to evade conventional antibiotic treatments. This overview explores the potential of immunomodulatory strategies as alternative therapeutic approaches to combat MRSA infections. Traditional antibiotics are becoming less effective, necessitating innovative solutions that harness the body's immune system to enhance pathogen clearance. Recent advancements in immunotherapy, including the use of antimicrobial peptides, phage therapy, and mechanisms of immune cells, demonstrate promise in enhancing the body's ability to clear MRSA infections. However, the exact interactions between these therapies and immunomodulation are not fully understood, underscoring the need for further research. Hence, this review aims to provide a broad overview of the current understanding of non-traditional therapeutics and their impact on immune responses, which could lead to more effective MRSA treatment strategies. Additionally, combining immunomodulatory agents with existing antibiotics may improve outcomes, particularly for immunocompromised patients or those with chronic infections. As the landscape of antibiotic resistance evolves, the development of effective immunotherapeutic strategies could play a vital role in managing MRSA infections and reducing reliance on traditional antibiotics. Future research must focus on optimizing these approaches and validating their efficacy in diverse clinical populations to address the urgent need for effective MRSA management strategies.

Nanoparticles-Delivered Circular RNA Strategy as a Novel Antitumor Approach

Anticancer therapy urgently needs the development of novel strategies. An innovative molecular target is represented by circular RNAs (circRNAs), single-strand RNA molecules with the 5' and 3' ends joined, characterized by a high stability. Although circRNA properties and biological functions have only been partially elucidated, their relationship and involvement in the onset and progression of cancer have emerged. Specific targeting of circRNAs may be obtained with antisense oligonucleotides and silencing RNAs. Nanotechnology is at the forefront of research for perfecting their delivery. Continuous efforts have been made to develop novel nanoparticles (NPs) and improve their performance, materials, and properties regarding biocompatibility and targeting capabilities. Applications in various fields, from imaging to gene therapy, have been explored. This review sums up the smart strategies developed to directly target circRNAs with the fruitful application of NPs in this context.

Advances in bioinspired nanomaterials managing microbial biofilms and virulence: A critical analysis

Microbial virulence and biofilm formation stand as a big concern against the goal of achieving a green and sustainable future. Microbial pathogenesis is the process by which the microbes (bacterial, fungal, and viral) cause illness in their respective host organism. 'Nanotechnology' is a state-of-art discipline to address this problem. The use of conventional techniques against microbial proliferation has been challenging against the environment. To tackle this problem, there has been a revolution in this multi-disciplinary field, to address the aspect of bioinspired nanomaterials in the antibiofilm and antimicrobial sector. Bioinspired nanomaterials prove to be a potential antibiofilm and antimicrobial agent as they are non-hazardous to the environment and mostly synthesized using a single-step reduction protocol. They exhibit synergistic effects against bacterial, fungal, and viral pathogens and thereby, control the virulence. In this literature review, we have elucidated the potential of bioinspired nanoparticles as well as nanomaterials as a promising anti-microbial treatment pedagogy and throw light on the advancements in how smart photo-switchable platforms have been designed to exhibit both bacterial releasing as well as bacterial-killing properties. Certain limitations and possible outcomes of these bio-based nanomaterials have been discussed in the hope of achieving a green and sustainable ecosystem.

Emerging trends and future challenges of advanced 2D nanomaterials for combating bacterial resistance

The number of multi-drug-resistant bacteria has increased over the last few decades, which has caused a detrimental impact on public health worldwide. In resolving antibiotic resistance development among different bacterial communities, new antimicrobial agents and nanoparticle-based strategies need to be designed foreseeing the slow discovery of new functioning antibiotics. Advanced research studies have revealed the significant disinfection potential of two-dimensional nanomaterials (2D NMs) to be severed as effective antibacterial agents due to their unique physicochemical properties. This review covers the current research progress of 2D NMs-based antibacterial strategies based on an inclusive explanation of 2D NMs' impact as antibacterial agents, including a detailed introduction to each possible well-known antibacterial mechanism. The impact of the physicochemical properties of 2D NMs on their antibacterial activities has been deliberated while explaining the toxic effects of 2D NMs and discussing their biomedical significance, dysbiosis, and cellular nanotoxicity. Adding to the challenges, we also discussed the major issues regarding the current quality and availability of nanotoxicity data. However, smart advancements are required to fabricate biocompatible 2D antibacterial NMs and exploit their potential to combat bacterial resistance clinically.

Nanotechnology's frontier in combatting infectious and inflammatory diseases: prevention and treatment

Inflammation-associated diseases encompass a range of infectious diseases and non-infectious inflammatory diseases, which continuously pose one of the most serious threats to human health, attributed to factors such as the emergence of new pathogens, increasing drug resistance, changes in living environments and lifestyles, and the aging population. Despite rapid advancements in mechanistic research and drug development for these diseases, current treatments often have limited efficacy and notable side effects, necessitating the development of more effective and targeted anti-inflammatory therapies. In recent years, the rapid development of nanotechnology has provided crucial technological support for the prevention, treatment, and detection of inflammation-associated diseases. Various types of nanoparticles (NPs) play significant roles, serving as vaccine vehicles to enhance immunogenicity and as drug carriers to improve targeting and bioavailability. NPs can also directly combat pathogens and inflammation. In addition, nanotechnology has facilitated the development of biosensors for pathogen detection and imaging techniques for inflammatory diseases. This review categorizes and characterizes different types of NPs, summarizes their applications in the prevention, treatment, and detection of infectious and inflammatory diseases. It also discusses the challenges associated with clinical translation in this field and explores the latest developments and prospects. In conclusion, nanotechnology opens up new possibilities for the comprehensive management of infectious and inflammatory diseases.

Gelatinase-responsive biodegradable targeted microneedle patch for abscess wound treatment of S. aureus infection

Abscess wound caused by bacterial infection is usually difficult to heal, thus greatly affect people's quality of life. In this study, a biodegradable drug-loaded microneedle patch (MN) is designed for targeted eradication of S. aureus infection and repair of abscess wound. Firstly, the bacterial responsive composite nanoparticle (Ce6@GNP-Van) with a size of about 182.6 nm is constructed by loading the photosensitizer Ce6 into gelatin nanoparticle (GNP) and coupling vancomycin (Van), which can specifically target S. aureus and effectively shield the phototoxicity of photosensitizer during delivery. When Ce6@GNP-Van is targeted and enriched in the infected regions, the gelatinase secreted by the bacteria can degrade GNP in situ and release Ce6, which can kill the bacteria by generating ROS under laser irradiation. In vivo experiments show that the microneedle is basically degraded in 10 min after inserting into skin, and the abscess wound is completely healed within 13 d after applying Ce6@GNP-Van-loaded MN patch to the abscess wound of the bacterial infected mice with laser irradiation, which can simultaneously achieve the eradication of biofilm and subsequent wound healing cascade activation, showing excellent synergistic antibacterial effect. In conclusion, this work establishes a synergistic treatment strategy to facilitate the repair of chronic abscess wound.

Acid-Responsive Aggregation of Gold Nanoparticles for the Photothermal Treatment of Bacterial Infections

Photothermal therapy (PTT) is considered to be one of the promising methods to combat pathogenic bacteria. However, traditional PTT is prone to generate undesired temperature increase to surrounding normal tissues, which limits the application of PTT. Herein, an acid-responsive PTT system (Au nanoparticles system: AuNPs-S) was constructed based on the photothermal feature of spherical gold nanoparticles (AuNPs) and the low pH of the bacterial infected site. AuNPs-S is composed of two kinds of AuNPs: AuNPs modified with Asp-Asp-Asp-Asp-Asp-Cys (peptide A) were denoted as AuNPs-A; AuNPs modified with 2,3-dimethylmaleic anhydride (DA) grafted Lys-Gly-Gly-Lys-Gly-Gly-Lys-Cys (peptide B) were denoted as AuNPs-B/DA. AuNPs-B/DA with an acid-responsive moiety showed a charge-convertible feature. The negatively charged AuNPs-B/DA became positively charged AuNPs-B at low pH, aggregating with the negatively charged AuNPs-A via an electrostatic interaction, reaching the threshold to the interparticle plasmonic coupling effect among AuNPs, thereby killing bacteria precisely under the irradiation of near-infrared (NIR) light through the elevated temperature at the targeted area. This acid-responsive PTT strategy supplies an excellent mode for combating bacterial infections with no vital damage to normal tissues.

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

Recent advance on nanoparticles or nanomaterials with anti-multidrug resistant bacteria and anti-bacterial biofilm properties: A systematic review

Objective

With the wide spread of Multidrug-resistant bacteria (MDR) due to the transfer and acquisition of antibiotic resistance genes and the formation of microbial biofilm, various researchers around the world are looking for a solution to overcome these resistances. One potential strategy and the best candidate to overcome these infections is using an effective nanomaterial with antibacterial properties against them.

Methods

and analysis: In this study, we overview nanomaterials with anti-MDR bacteria and anti-biofilm properties. Hence, we systematically explored biomedical databases (Web of Sciences, Google Scholar, PubMed, and Scopus) to categorize related studies about nanomaterial with anti-MDR bacteria and anti-biofilm activities from 2007 to December 2022.

Results

In total, forty-one studies were investigated to find antibacterial and anti-biofilm information about the nanomaterial during 2007-2022. According to the collected documents, nineteen types of nanomaterial showed putative antibacterial effects such as Cu, Ag, Au, Au/Pt, TiO2, Al2O3, ZnO, Se, CuO, Cu/Ni, Cu/Zn, Fe3O4, Au/Fe3O4, Au/Ag, Au/Pt, Graphene O, and CuS. In addition, seven types of them considered as anti-biofilm agents such as Ag, ZnO, Au/Ag, Graphene O, Cu, Fe3O4, and Au/Ag.

Conclusion

According to the studies, each of nanomaterial has been designed with different methods and their effects against standard strains, clinical strains, MDR strains, and bacterial biofilms have been investigated in-vitro and in-vivo conditions. In addition, nanomaterials have different destructive mechanism on bacterial structures. Various nanoparticles (NP) introduced as the best candidate to designing new drug and medical equipment preventing infectious disease outbreaks by overcome antibiotic resistance and bacterial biofilm.

Targeting and arginine-driven synergizing photodynamic therapy with nutritional immunotherapy nanosystems for combating MRSA biofilms

The resistance and immune escape of methicillin-resistant Staphylococcus aureus (MRSA) biofilms cause recalcitrant infections. Here, we design a targeting and synergizing cascade PDT with nutritional immunotherapy nanosystems (Arg-PCN@Gel) containing PCN-224 as PDT platform for providing reactive oxygen species (ROS), incorporating arginine (Arg) as nitric oxide (NO) donor to cascade with ROS to produce more lethal ONOO- and promote immune response, and coating with gelatin as targeting agent and persistent Arg provider. The nanosystems adhered to the autolysin of MRSA and inhibited Arg metabolism by down-regulating icdA and icaA. It suppressed polysaccharide intercellular adhesin and extracellular DNA synthesis to prevent biofilm formation. The NO broke mature biofilms and helped ROS and ONOO- penetrate into biofilms to inactivate internal MRSA. Arg-PCN@Gel drove Arg to enhance immunity via inducible NO synthase/NO axis and arginase/polyamine axis and achieve efficient target treatment in MRSA biofilm infections. The targeting and cascading PDT synergized with nutritional immunotherapy provide an effective promising strategy for biofilm-associated infections.

Confined Cascade Metabolic Reprogramming Nanoreactor for Targeted Alcohol Detoxification and Alcoholic Liver Injury Management

Alcoholic liver injury (ALI) is the leading cause of serious liver disease, whereas current treatments are mostly supportive and unable to metabolize alcohol directly. Here we report a metabolic reprogramming strategy for targeted alcohol detoxification and ALI management based on a confined cascade nanoreactor. The nanoreactor (named AA@mMOF) is designed by assembling natural enzymes of alcohol oxidase (AOx) and aldehyde dehydrogenase (ALDH) in the cavity of a mesoporous metal organic framework (mMOF) nanozyme with intrinsic catalase (CAT)-like activity. By conducting confined AOx/CAT/ALDH cascade reactions, AA@mMOF enables self-accelerated alcohol degradation (>0.5 mg·mL^-1·h^-1) with negligible aldehyde diffusion and accumulation, reprogramming alcohol metabolism and allowing high-efficiency detoxification. Administered to high-dose alcohol-intoxicated mice, AA@mMOF shows surprising liver targeting and accumulation performance and dramatically reduces blood alcohol concentration and rapidly reverses unconsciousness and acute liver injury to afford targeted alcoholism treatment. Moreover, AA@mMOF dramatically alleviates fat accumulation and oxidative stress in the liver of chronic alcoholism mice to block and reverse the progression of ALI. By conducting confined AOx/CAT/ALDH cascade reactions for high-efficiency alcohol metabolism reprogramming, AA@mMOF nanoreactor offers a powerful modality for targeted alcohol detoxification and ALI management. The proposed confined cascade metabolic reprogramming strategy provides a paradigm shift for the treatment of metabolic diseases.

Mesoporous silica nanoparticles as carrier to overcome bacterial drug resistant barriers

Antibiotic resistance has become a global threat to health due to abuse of antibiotics. Lots of existing antibiotics have lost their effect on drug resistant bacteria. Moreover, the discovery of novel antibiotics becomes more and more difficult. It is necessary to develop new strategies to fight against antibiotic resistance. Nano-drug delivery systems endow old antibiotics with new vitality to defeat the antibiotic resistant barrier by protecting antibiotics against hydrolysis, increasing uptake and circumventing efflux pump. Among them, mesoporous silica nanoparticles (MSNs) are one of the most extensively investigated as carrier of antibiotics due to large drug loading capability, tunable physicochemical characteristics, and biocompatibility. MSNs can improve the delivery of antibiotics to bacteria greatly by reducing size, modifying surface, and regulating shapes. Furthermore, MSNs hybridized metal ions or metal nanoparticles exert stronger antibacterial effect by controlling the release of metal ions or increasing active oxygen species. In addition, metal capped MSNs are also able to load antibiotics to exert synergistic antibacterial effect. This paper firstly reviewed the current application of various nanomaterials as antibacterial agents, and then focused on the MSNs including the introduction of MSNs and various approaches for improving antibacterial effect of MSNs.

ε-poly-L-lysine-modified polydopamine nanoparticles for targeted photothermal therapy of drug-resistant bacterial keratitis

Bacterial keratitis can lead to intraocular infection and even blindness without prompt and potent treatments. Currently, clinical abuse of antibiotics encouraged the evolution of resistant bacteria. Conventional antibiotic eye drops based keratitis treatment has been heavily restricted due to the lack of bactericidal efficiency and easy induction of bacterial resistance. Hence, developing an effective treatment strategy for bacterial keratitis is of great significance. In this work, we investigated ε-poly-l-lysine (EPL)-modified polydopamine (PDA) nanoparticles (EPL@PDA NPs)-mediated antibacterial photothermal therapy (aPTT), to cope with methicillin-resistant Staphylococcus aureus (MRSA)-induced keratitis. The surface modification of cationic peptide EPL enables EPL@PDA NPs to specifically target negatively charged MRSA and induces local hyperthermia to kill the bacteria under low ambient temperature. Under near-infrared (NIR) irradiation, the sterilization efficiency of EPL@PDA NPs suspension for MRSA in vitro was up to 99.96%. The EPL@PDA-mediated aPTT presented potent antibacterial efficacy in treating MRSA-induced keratitis with little corneal epithelial cytotoxicity and good biocompatibility. In conclusion, the bacterial-targeting aPTT platform in this work provides a prospective method for the management of MRSA-induced refractory bacterial keratitis.

Vibrational Optical Activity Study of Four Antibiotic (Lipo)glycopeptides: Vancomycin, Oritavancin, Dalbavancin, and Teicoplanin

The antibiotic glycopeptide class, of which vancomycin is the original compound, has received due attention over the past few decades in search of antibiotics to overcome resistances developed by bacteria. Crucial for the understanding and further development of glycopeptides that possess desired antibacterial effects is the determination of their conformational behavior, as this sheds light on the mechanism of action of the compound. Among others, vibrational optical activity (VOA) techniques (vibrational circular dichroism and Raman optical activity) can be deployed for this, but the question remains to what extent these spectroscopic techniques can provide information concerning the molecular class under investigation. This contribution takes the last hurdle in the search for the capabilities of the VOA techniques in the conformational analysis of the antibiotic glycopeptide class by extending research that was previously conducted for vancomycin toward its three derivatives: oritavancin, dalbavancin, and teicoplanin. The principal information that can be drawn from VOA spectra is the conformation of the rigid cyclic parts of the glycopeptides and the aromatic rings that are part hereof. The addition or removal of carbohydrates does not induce noticeable VOA spectral responses, preventing the determination of the conformation they adopt.

Decoy Nanozymes Enable Multitarget Blockade of Proinflammatory Cascades for the Treatment of Multi-Drug-Resistant Bacterial Sepsis

Sepsis is a life-threatening organ dysfunction characterized by severe systemic inflammatory response to infection. Effective treatment of bacterial sepsis remains a paramount clinical challenge, due to its astonishingly rapid progression and the prevalence of bacterial drug resistance. Here, we present a decoy nanozyme-enabled intervention strategy for multitarget blockade of proinflammatory cascades to treat multi-drug-resistant (MDR) bacterial sepsis. The decoy nanozymes (named MCeC@MΦ) consist mesoporous silica nanoparticle cores loaded with CeO2 nanocatalyst and Ce6 photosensitizer and biomimetic shells of macrophage membrane. By acting as macrophage decoys, MCeC@MΦ allow targeted photodynamic eradication of MDR bacteria and realize simultaneous endotoxin/proinflammatory cytokine neutralization. Meanwhile, MCeC@MΦ possess intriguing superoxide dismutase and catalase-like activities as well as hydroxyl radical antioxidant capacity and enable catalytic scavenging of multiple reactive oxygen species (ROS). These unique capabilities make MCeC@MΦ to collaboratively address the issues of bacterial infection, endotoxin/proinflammatory cytokine secretion, and ROS burst, fully cutting off the path of proinflammatory cascades to reverse the progression of bacterial sepsis. In vivo experiments demonstrate that MCeC@MΦ considerably attenuate systemic hyperinflammation and rapidly rescue organ damage within 1 day to confer higher survival rates (>75%) to mice with progressive MDR Escherichia coli bacteremia. The proposed decoy nanozyme-enabled multitarget collaborative intervention strategy offers a powerful modality for bacterial sepsis management and opens up possibilities for the treatment of cytokine storm in the COVID-19 pandemic and immune-mediated inflammation diseases.

A self-assembled bilayer polypeptide-engineered hydrogel for spatiotemporal modulation of bactericidal and anti-inflammation process in osteomyelitis treatment

Background

Drug resistance of pathogens and immunosuppression are the main causes of clinical stagnation of osteomyelitis. The ideal treatment strategy for osteomyelitis is to achieve both efficient antibacterial and bone healing through spatiotemporal modulation of immune microenvironment.

Methods

In this study, a bilayer hydrogel based on genetically engineered polypeptide AC10A and AC10ARGD was prepared by self-assembly. Ag2S QDs@DSPE-mPEG2000-Ce6/Aptamer (AD-Ce6/Apt) was loaded in the top layer AC10A hydrogel (AA) for antibacterial, and bone marrow-derived mesenchymal stem cells (BMSCs) were loaded in the lower layer AC10ARGD hydrogel (MAR) for bone healing. The AD-Ce6/Apt can be released from the AA hydrogel to target S. aureus before bacterial biofilm formation and achieved significant bactericidal effect under irradiation with a 660 nm laser. Moreover, AD-Ce6/Apt can induce M1 type polarization of macrophages to activate the immune system and eliminate residual bacteria. Subsequently, BMSCs released from the MAR hydrogel can differentiate into osteoblasts and promote the formation of an anti-inflammatory microenvironment by regulating the M2 type polarization of macrophages. The bilayer AA-MAR hydrogel possessed good biocompatibility.

Results

The in vitro and in vivo results showed that the AA-MAR hydrogel not only realized efficient photodynamic therapy of S. aureus infection, but also promoted the transformation of immune microenvironment to fulfill the different needs of each stage, which ultimately improved bone regeneration and mechanical properties post-surgery.

Conclusion

This work presents an approach for spatiotemporal modulation of immune microenvironment in the treatment of osteomyelitis.

Graphical Abstract

Engineering hierarchical FeS2/TiO2 nanotubes on Ti mesh as a tailorable flow-through catalyst belt for all-day-active degradation of organic pollutants and pathogens

The increasing organic and microbiological pollutions in fresh water caused by human activities and industrial development have become a global concern nowadays. In this study, three-dimensional (3D) hierarchical FeS₂/TiO₂ structures with nanotube geometries were grown on a Ti mesh (M-TNTAs-FeS₂). Benefitting from the abundant available reactive sites on the open 3D micro/nanoporous structures, excellent photocatalytic activity of FeS₂/TiO₂ heterostructure in solar light, and satisfactory Fenton activity of FeS₂, the obtained M-TNTAs-FeS₂ exhibits outstanding performance as an all-day-active catalyst. Importantly, flexible meshes can be easily tailored and enveloped into fluorinated ethylene propylene (FEP) pockets in a series as a flow-through belt for large-capacitance applications (998 L m^-2 at a flow rate of 417 L m^-2 h^-1 for a four-pockets belt), as indicated by the degradation of azo dyes, antibiotics, pesticides, and pathogens. This study may inspire a new tailorable catalyst design for a promising point-of-use purification device.

Lanthanide/Cu2-xSe Nanoparticles for Bacteria-Activated NIR-II Fluorescence Imaging of Infection

A material system enabling specific NIR-II fluorescence imaging of Gram-positive bacteria is described. The material system is based on the electrostatic binding of Cu_2-xSe and vancomycin-modified NaGdF₄:Nd,Yb@NaGdF₄ downconversion nanoparticles (DCNPs), the fluorescence of which is weak owing to the spectral overlap of Cu_2-xSe absorption with the DCNP NIR emission. The presence of Gram-positive bacteria precisely disconnects the bond between vancomycin-modified DCNPs and Cu_2-xSe, thus enabling a strong fluorescent signal. In vivo studies show that the material system can be specifically activated at the site of Gram-positive bacterial infection but is essentially nonfluorescent in the area of Gram-negative bacterial infection.

Nanotechnology Approaches for Rapid Detection and Theranostics of Antimicrobial Resistant Bacterial Infections

As declared by WHO, antimicrobial resistance (AMR) is a high priority issue with a pressing need to develop impactful technologies to curb it. The rampant and inappropriate use of antibiotics due to the lack of adequate and timely diagnosis is a leading cause behind AMR evolution. Unfortunately, populations with poor economic status and those residing in densely populated areas are the most affected ones, frequently leading to emergence of AMR pathogens. Classical approaches for AMR diagnostics like phenotypic methods, biochemical assays, and molecular techniques are cumbersome and resource-intensive and involve a long turnaround time to yield confirmatory results. In contrast, recent emergence of nanotechnology-assisted approaches helps to overcome challenges in classical approaches and offer simpler, more sensitive, faster, and more affordable solutions for AMR diagnostics. Nanomaterial platforms (metallic, quantum-dot, carbon-based, upconversion, etc.), nanoparticle-based rapid point-of-care platforms, nano-biosensors (optical, mechanical, electrochemical), microfluidic-assisted devices, and importantly, nanotheranostic devices for diagnostics with treatment of AMR infections are examples of rapidly growing nanotechnology approaches used for AMR management. This review comprehensively summarizes the past 10 years of research progress on nanotechnology approaches for AMR diagnostics and for estimating antimicrobial susceptibility against commonly used antibiotics. This review also highlights several bottlenecks in nanotechnology approaches that need to be addressed prior to considering their translation to clinics.

Synthesis of a Two-Dimensional Molybdenum Disulfide Nanosheet and Ultrasensitive Trapping of Staphylococcus Aureus for Enhanced Photothermal and Antibacterial Wound-Healing Therapy

Photothermal therapy has been widely used in the treatment of bacterial infections. However, the short photothermal effective radius of conventional nano-photothermal agents makes it difficult to achieve effective photothermal antibacterial activity. Therefore, improving composite targeting can significantly inhibit bacterial growth. We inhibited the growth of Staphylococcus aureus (S. aureus) by using an extremely low concentration of vancomycin (Van) and applied photothermal therapy with molybdenum disulfide (MoS₂). This simple method used chitosan (CS) to synthesize fluorescein 5(6)-isothiocyanate (FITC)-labeled and Van-loaded MoS₂-nanosheet hydrogels (MoS₂-Van-FITC@CS). After modifying the surface, an extremely low concentration of Van could inhibit bacterial growth by trapping bacteria synergistically with the photothermal effects of MoS₂, while FITC labeled bacteria and chitosan hydrogels promoted wound healing. The results showed that MoS₂-Van-FITC@CS nanosheets had a thickness of approximately 30 nm, indicating the successful synthesis of the nanosheets. The vitro antibacterial results showed that MoS₂-Van-FITC with near-infrared irradiation significantly inhibited S. aureus growth, reaching an inhibition rate of 94.5% at nanoparticle concentrations of up to 100 µg/mL. Furthermore, MoS₂-Van-FITC@CS could exert a healing effect on wounds in mice. Our results demonstrate that MoS₂-Van-FITC@CS is biocompatible and can be used as a wound-healing agent.

Improving the Hemocompatibility of Antimicrobial Peptidomimetics through Amphiphilicity Masking Using a Secondary Amphiphilic Polymer

Antimicrobial peptidomimetics (AMPMs) have received widespread attention as potentially powerful weapons against antibiotic resistance. However, AMPMs' membrane disruption mechanism not only brings resistance-resistant nature, but also nonspecific binding and disruption toward eukaryotic cell membranes, and consequently, their hemolytic activity is the primary concern on clinical applications. Here, the preparation and screening of an AMPM library is reported, through which a best-performing hit, PT-b1, can be obtained. To further improve PT-b1's hemocompatibility, a strategy is devised to mask the amphiphilicity of the AMPM using a charge-free, FDA-approved amphiphilic polymer, Pluronic F-127 (PF127). A PF127 solution containing PT-b1 can form a temperature-sensitive, absorbable hydrogel at higher concentration, but dissolve and complex with PT-b1 through hydrophobic interactions at lower concentration or lower temperature. The complexation from PF127 can mask the amphiphilicity of PT-b1 and render it extremely hemocompatible, yet the reversibility in such nanocomplexation and the existence of a secondary mechanism of action ensure that the AMPM's potency remains unchanged. The in vivo effectiveness of this antimicrobial hydrogel system is demonstrated using a mice wound infection model established with Methicillin-resistant Staphylococcus aureus, and observations indicate the hydrogel can promote wound healing and suppress bacteria-caused inflammation even when resistant pathogens are involved.

Environment tolerant, adaptable and stretchable organohydrogels: preparation, optimization, and applications

Multiple stretchable materials have been successively developed and applied to wearable devices, soft robotics, and tissue engineering. Organohydrogels are currently being widely studied and formed by dispersing immiscible hydrophilic/hydrophobic polymer networks or only hydrophilic polymer networks in an organic/water solvent system. In particular, they can not only inherit and carry forward the merits of hydrogels, but also have some unique advantageous features, such as anti-freezing and water retention abilities, solvent resistance, adjustable surface wettability, and shape memory effect, which are conducive to the wide environmental adaptability and intelligent applications. This review first summarizes the structure, preparation strategy, and unique advantages of the reported organohydrogels. Furthermore, organohydrogels can be optimized for electro-mechanical properties or endowed with various functionalities by adding or modifying various functional components owing to their modifiability. Correspondingly, different optimization strategies, mechanisms, and advanced developments are described in detail, mainly involving the mechanical properties, conductivity, adhesion, self-healing properties, and antibacterial properties of organohydrogels. Moreover, the applications of organohydrogels in flexible sensors, energy storage devices, nanogenerators, and biomedicine have been summarized, confirming their unlimited potential in future development. Finally, the existing challenges and future prospects of organohydrogels are provided.

Heterostructured Metal-Organic Frameworks/Polydopamine Coating Endows Polyetheretherketone Implants with Multimodal Osteogenicity and Photoswitchable Disinfection

Clinically, bacteria-induced contagion and insufficient osseointegrative property inevitably elicit the failure of orthopedic implants. Herein, a heterostructured coating consisting of simvastatin (SIM)-laden metal-organic frameworks and polydopamine nanolayers is created on a porous bioinert polyetheretherketone implant. The heterostructured coating significantly promotes cytocompatibility and osteogenic differentiation through multimodal osteogenicity mechanisms of zinc ion (Zn²⁺ ) therapy, SIM drug therapy, and surface micro-/nano-topological stimulation. Under the illumination of near-infrared (NIR) light, singlet oxygen (¹ O₂ ) and local hyperthermia are produced; besides, NIR light dramatically accelerates the release of Zn²⁺ ions from heterostructured coatings. Gram-positive and -negative bacteria are effectively eradicated by the synergy of photothermal/photodynamic effects and photo-induced accelerated delivery of Zn²⁺ ions. The superior osteogenicity and osseointegration, as well as photoswitchable disinfection controlled by NIR light are corroborated via in vivo results. This work highlights the great potential of photoresponsive heterostructured orthopedic implants in treatment of the noninvasive bone reconstruction of bacteria-associated infectious tissues through multimodal phototherapy and photoswitchable ion-therapy.

NIR-regulated dual-functional silica nanoplatform for infected-wound therapy via synergistic sterilization and anti-oxidation

Nature-derived bioactive components and photothermal synergistic therapy bring potential strategies for fighting bacterial infection and accelerating would healing by virtue of their excellent therapeutic efficiencies and ignorable side effects, where photothermal property not only acts as sterilization energy but also as a doorkeeper to control the natural component release. Herein, by integrating the excellent antibacterial property of cinnamaldehyde (CA) and the outstanding photothermal performance of copper sulfide nanoparticles (CuS NPs), a multifunctional nanoplatform of SiO₂ @CA@CuS nanospheres (NSs) is constructed with silica nanosphere (SiO₂ NSs) as carrier. SiO₂ @CA@CuS NSs exhibit photothermal property, bacterial absorption capacity, extraordinary antibacterial activity and antioxidant property. Mechanism characteriazation and antibacterial experiment indicate that positive charged SiO₂ @CA@CuS can adhere to the negative charged surface of bacteria, and quickly kill bacteria through the synergistic action of the released CA and heat produced under near infrared light (NIR) irradiation at 980 nm. The sterilization efficiencies for Escherichia coli (E. coli) and S. aureus reach 99.86% and 99.84%, respectively. Furthermore, NIR-regulated SiO₂ @CA@CuS perform great biocompatibility, as well as effective effects for accelerating S. aureus-infected wound healing at a low photothermal temperature (45 °C) relying on synergistic sterilization and anti-oxidation.

Nanophysical Antimicrobial Strategies: A Rational Deployment of Nanomaterials and Physical Stimulations in Combating Bacterial Infections

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.

Nanoantibiotics to fight multidrug resistant infections by Gram-positive bacteria: hope or reality?

The spread of antimicrobial resistance in Gram-positive pathogens represents a threat to human health. To counteract the current lack of novel antibiotics, alternative antibacterial treatments have been increasingly investigated. This review covers the last decade's developments in using nanoparticles as carriers for the two classes of frontline antibiotics active on multidrug-resistant Gram-positive pathogens, i.e., glycopeptide antibiotics and daptomycin. Most of the reviewed papers deal with vancomycin nanoformulations, being teicoplanin- and daptomycin-carrying nanosystems much less investigated. Special attention is addressed to nanoantibiotics used for contrasting biofilm-associated infections. The status of the art related to nanoantibiotic toxicity is critically reviewed.

Photoactivated Release of Nitric Oxide and Antimicrobial Peptide Derivatives for Synergistic Therapy of Bacterial Skin Abscesses

It is of paramount importance to develop novel approaches for combating bacterial resistance and the integration of different antibacterial mechanisms is essential to achieve synergistic bactericidal efficiency while reducing the associated side effects. Herein, amphiphilic antimicrobial copolymers derived from poly-l-lysine (PLL), black phosphorus quantum dots (BPQDs) as near-infrared (NIR) sensitizer, and S-nitrosocysteamine (SNO) as nitric oxide (NO) donor, are assembled into PELI@BPQD-SNO nanoparticles through electrostatic interactions. Amphiphilic copolymers with isopentanyl grafts on PLL at a ratio of 50% achieve an optimal balance between antibacterial activity and hemolysis rate. Photothermal effect of BPQDs leads to NIR-responsive release of NO and the combination with amphiphilic copolymers mutually enhances long-term inhibition of bacterial growth. In an S. aureus-infected subcutaneous abscess model, the bactericidal rate of PELI@BPQD-SNO/NIR treatment reaches nearly 99.6%, which is significantly higher than those without NO release (38%) or amphiphilic copolymers (24%) or NIR irradiation (17%). PELI@BPQD-SNO/NIR treatment shows full recovery of infected wounds, efficient retardation of inflammatory cells, and reconstruction of blood vessels similar to those of healthy skin. Therefore, the electrostatic assembly demonstrates a promising strategy to deliver charged therapeutic agents and the photoactivated release of NO and amphiphilic copolymers achieves synergistic antibacterial efficacy without using any antibiotics.

pH-switchable nanozyme cascade catalysis: a strategy for spatial-temporal modulation of pathological wound microenvironment to rescue stalled healing in diabetic ulcer

The management of diabetic ulcer (DU) to rescue stalled wound healing remains a paramount clinical challenge due to the spatially and temporally coupled pathological wound microenvironment that features hyperglycemia, biofilm infection, hypoxia and excessive oxidative stress. Here we present a pH-switchable nanozyme cascade catalysis (PNCC) strategy for spatial–temporal modulation of pathological wound microenvironment to rescue stalled healing in DU. The PNCC is demonstrated by employing the nanozyme of clinically approved iron oxide nanoparticles coated with a shell of glucose oxidase (Fe₃O₄-GOx). The Fe₃O₄-GOx possesses intrinsic glucose oxidase (GOx), catalase (CAT) and peroxidase (POD)-like activities, and can catalyze pH-switchable glucose-initiated GOx/POD and GOx/CAT cascade reaction in acidic and neutral environment, respectively. Specifically, the GOx/POD cascade reaction generating consecutive fluxes of toxic hydroxyl radical spatially targets the acidic biofilm (pH ~ 5.5), and eradicates biofilm to shorten the inflammatory phase and initiate normal wound healing processes. Furthermore, the GOx/CAT cascade reaction producing consecutive fluxes of oxygen spatially targets the neutral wound tissue, and accelerates the proliferation and remodeling phases of wound healing by addressing the issues of hyperglycemia, hypoxia, and excessive oxidative stress. The shortened inflammatory phase temporally coupled with accelerated proliferation and remodeling phases significantly speed up the normal orchestrated wound-healing cascades. Remarkably, this Fe₃O₄-GOx-instructed spatial–temporal remodeling of DU microenvironment enables complete re-epithelialization of biofilm-infected wound in diabetic mice within 15 days while minimizing toxicity to normal tissues, exerting great transformation potential in clinical DU management. The proposed PNCC concept offers a new perspective for complex pathological microenvironment remodeling, and may provide a powerful modality for the treatment of microenvironment-associated diseases.

Accelerated antibacterial red-carbon dots with photodynamic therapy against multidrug-resistant Acinetobacter baumannii

The emergence of antibiotic resistance in bacteria is a major public-health issue. Synthesis of efficient antibiotic-free material is very important for fighting bacterial infection-related diseases. Herein, red-carbon dots (R-CDs) with a broad range of spectral absorption (350-700 nm) from organic bactericides or intermediates were synthesized through a solvothermal route. The prepared R-CDs not only had intrinsic antibacterial activities, but also could kill multidrug-resistant bacteria (multidrug-resistant Acinetobacter baumannii (MRAB) and multidrug-resistant Staphylococcus aureus (MRSA)) effectively by generating reactive oxygen species. Furthermore, R-CDs could eliminate and inhibit the formation of MRAB biofilms, while conferring few side effects on normal cells. A unique property of R-CDs was demonstrated upon in vivo treatment of antibiotic-sensitive MRAB-induced infected wounds. These data suggested that this novel R-CDs-based strategy might enable the design of next-generation agents to fight drug-resistant bacteria.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available for this article at 10.1007/s40843-021-1770-0 and is accessible for authorized users.

In situ formation of a near-infrared controlled dual-antibacterial platform

An in situ formed antibacterial platform was designed for near-infrared controlled pharmacotherapy and photothermal therapy of drug-resistant bacteria.

One-step synthesis of quaternized silica nanoparticles with bacterial adhesion and aggregation properties for effective antibacterial and antibiofilm treatments

Preservation of intact cell morphology of bacteria is recognized as one important cause of bacterial drug resistance, and hence developing new antibacterial agents capable of fighting against bacteria via disrupting...

Formation of a ZnO nanorods-patterned coating with strong bactericidal capability and quantitative evaluation of the contribution of nanorods-derived puncture and ROS-derived killing

To endow Ti-based orthopedic implants with strong bactericidal activity, a ZnO nanorods-patterned coating (namely ZNR) was fabricated on Ti utilizing a catalyst- and template-free method of micro-arc oxidation (MAO) and hydrothermal treatment (HT). The coating comprises an outer layer of ZnO nanorods and a partially crystallized inner layer with nanocrystalline TiO₂ and Zn₂TiO₄ embedded amorphous matrix containing Ti, O and Zn. During HT, Zn²⁺ ions contained in amorphous matrix of the as-MAOed layer migrate to surface and react with OH⁻ in hydrothermal solution to form ZnO nuclei growing in length at expense of the migrated Zn²⁺. ZNR exhibits intense bactericidal activity against the adhered and planktonic S. aureus in vitro and in vivo. The crucial contributors to kill the adhered bacteria are ZnO nanorods derived mechano-penetration and released reactive oxygen species (ROS). Within 30 min of S. aureus incubation, ROS is the predominant bactericidal contributor with quantitative contribution value of ∼20%, which transforms into mechano-penetration with prolonging time to reach quantitative contribution value of ∼96% at 24 h. In addition, the bactericidal contributor against the planktonic bacteria of ZNR is relied on the released Zn²⁺. This work discloses an in-depth bactericidal mechanism of ZnO nanorods.

(1)

A templates and catalysts-free method is used to fabricate ZnO nanorods on Ti

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ZnO nanorods-arrayed coating shows intense broad-spectrum bactericidal activity

(3)

Main bactericidal contributor of ZnO nanorods to adhered bacteria is mechano-puncture

(4)

Main bactericidal contributor of ZnO nanorods to planktonic bacteria is released Zn²⁺

Aggregation-Induced Emission-Based Platforms for the Treatment of Bacteria, Fungi, and Viruses

The prevention and control of pathogenic bacteria, fungi, and viruses is a herculean task for all the countries since they greatly threaten global public health. Rapid detection and effective elimination of these pathogens is crucial for the treatment of related diseases. It is urgently demanded to develop new diagnostic and therapeutic strategies to combat bacteria, fungi, and viruses-induced infections. The emergence of aggregation-induced emission (AIE) luminogens (AIEgens) is a revolutionary breakthrough for the treatment of many diseases, including pathogenic infections. In this review, the main focus is on the applications of AIEgens for theranostic treatment of pathogenic bacteria, fungi, and viruses. Due to the AIE characteristic, AIEgens are promising fluorescent probes for the detection of bacteria, fungi, and viruses with excellent sensitivity and photostability. Moreover, AIEgen-based theranostic platforms can be fabricated by introducing bactericidal moieties or designing AIE photosensitizers and AIE photothermal agents. The current strategies and ongoing developments of AIEgens for the treatment of pathogenic bacteria, fungi, and viruses will be discussed in detail.

Bacteria-Triggered Multifunctional Hydrogel for Localized Chemodynamic and Low-Temperature Photothermal Sterilization

Pathogenic infections seriously threaten public health and have been considered as one of the most critical challenges in clinical therapy. Construction of a safe and efficient photothermal antibacterial platform is a promising strategy for treatment of bacterial infections. Considering that high temperature does harm to the normal tissues and cells, herein, a bacteria-triggered multifunctional hydrogel is constructed for low-temperature photothermal sterilization with high efficiency by integrating localized chemodynamic therapy (L-CDT). The hydrogel is constructed by incorporating copper sulfide nanoparticles (CuS_NPs ) with photothermal profile into the network of hyaluronic acid (HA) and Fe³⁺ -EDTA complexes, named as CHFH (CuS_NPs -HA-Fe³⁺ -EDTA hydrogel). Bacteria can be accumulated on the surface of CHFH, which secretes hyaluronidase to decompose the HA and release Fe³⁺ . The Fe³⁺ is reduced into Fe²⁺ in microenvironment of bacteria to trigger Fenton reaction. The generated hydroxyl radicals result in sterilization based on L-CDT within short range. By integrating with photothermal property of CuS_NPs , low-temperature photothermal therapy (LT-PTT) for sterilization is realized, which improves the antibacterial efficiency while minimizes damage to normal tissues. The CHFH is further used to prepare Band aid which effectively promotes the Staphylococcus aureus-infected wound healing process in vivo, confirming the great potential for clinical application.

Infection microenvironment-related antibacterial nanotherapeutic strategies

The emergence and spread of antibiotic resistance is one of the biggest challenges in public health. There is an urgent need to discover novel agents against the occurrence of multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. The drug-resistant pathogens are able to grow and persist in infected sites, including biofilms, phagosomes, or phagolysosomes, which are more difficult to eradicate than planktonic ones and also foster the development of drug resistance. For years, various nano-antibacterial agents have been developed in the forms of antibiotic nanocarriers. Inorganic nanoparticles with intrinsic antibacterial activity and inert nanoparticles assisted by external stimuli, including heat, photon, magnetism, or sound, have also been discovered. Many of these strategies are designed to target the unique microenvironment of bacterial infections, which have shown potent antibacterial effects in vitro and in vivo. This review summarizes ongoing efforts on antibacterial nanotherapeutic strategies related to bacterial infection microenvironments, including targeted antibacterial therapy and responsive antibiotic delivery systems. Several grand challenges and future directions for the development and translation of effective nano-antibacterial agents are also discussed. The development of innovative nano-antibacterial agents could provide powerful weapons against drug-resistant bacteria in systemic or local bacterial infections in the foreseeable future.

Smart Asymmetric Hydrogel with Integrated Multi-Functions of NIR-Triggered Tunable Adhesion, Self-Deformation, and Bacterial Eradication

Multifunctional hydrogels acting as wound dressing have received extensive attention in soft tissue repair; however, it is still a challenge to develop a non-antibiotic-dependent antibacterial hydrogel that has tunable adhesion and deformation to achieve on-demand removal. Herein, an asymmetric adhesive hydrogel with near-infrared (NIR)-triggered tunable adhesion, self-deformation, and bacterial eradication is designed. The hydrogel is prepared by the crosslinking polymerization of N-isopropylacrylamide and acrylic acid, during the sedimentation of conductive PPy-PDA nanoparticles based on the polymerization of pyrrole (Py) and dopamine (DA). Due to the conversion capacity from NIR light into heat for PPy-PDA NPs, the formed temperature-sensitive hydrogel exhibits tissue adhesive as well as NIR-triggered tunable adhesion and self-deformation property, which can achieve an on-demand dressing refreshing. Systematically in vitro/in vivo antibacterial experiments indicate that the hydrogel shows excellent disinfection capability to both Gram-negative and Gram-positive bacteria. The in vivo experiments in a full-layer cutaneous wound model demonstrate that the hydrogel has a good treatment effect to promote wound healing. Overall, the asymmetric hydrogel with tunable adhesion, self-deformation, conductive, and photothermal antibacterial activity may be a promising candidate to fulfill the functions of adhesion on skin tissue, easy removing on-demand, and accelerating the wound healing process.

A transformable gold nanocluster aggregate-based synergistic strategy for potentiated radiation/gene cancer therapy

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 (<2 nm), leading to the tumor microenvironment-responsive size transformation of the nano-radiosensitizer and activated release of the loaded antisense oligonucleotides to perform gene silencing. The in vitro experiments demonstrated that AuNC-ASON could amplify and improve the radio-sensitivity of tumor cells (the sensitization enhancement ratio was about 1.81) as a result of the synergistic effect of the transformable gold nanocluster radiosensitizer and survivin gene interference. Remarkably, the size transformation capability realized the high tumor retention/penetration and renal metabolism of AuNC-ASON in vivo and boosted the radio-susceptibility of cancer cells with the assistance of survivin gene interference, synergistically achieving potentiated tumor radiation/gene therapy. The proposed concept of transformable nano-radiosensitizer aggregate-based synergistic therapy can be utilized as a general strategy to guide the design of activatable multifunctional nanosystems for cancer theranostics.

Photoenhanced Dual-Functional Nanomedicine for Promoting Wound Healing: Shifting Focus from Bacteria Eradication to Host Microenvironment Modulation

Pathogenic bacterial infection has become a serious medical threat to global public health. Once the skin has serious defects, bacterial invasion and the following chain reactions will be a thorny clinical conundrum, which takes a long time to heal. Although various strategies have been used to eradicate bacteria, the treatment which can simultaneously disinfect and regulate the infection-related host responses is rarely reported. Herein, inspired by the host microenvironment, a photoenhanced dual-functional nanomedicine is constructed (Hemin@Phmg-TA-MSN) for localized bacterial ablation and host microenvironment modulation. The "NIR-triggered local microthermal therapy" and positively charged surface endow the nanomedicine with excellent bacterial capture and killing activities. Meanwhile, the nanomedicine exhibits broad-spectrum reactive oxygen species (ROS) scavenging activity via the synergistic effect of hemin and tannic acid with photoenhanced electron and hydrogen transfers. Furthermore, the in vivo experiments demonstrate that the dual-functional nanomedicine not only presents robust bacterial eradication capability, but also triggers the oxidative stress and inflammatory microenvironment regulation. The work not only shows a facile and effective way for infected wound management but also provides a new horizon for designing novel and efficient anti-infection therapy shifting focus from bacteria treatment to host microenvironment modulation.

Curcumin-loaded high internal phase emulsions stabilized with lysine modified lignin: a biological agent with high photothermal protection and antibacterial properties

Bacterial infections and multidrug resistance can seriously endanger the health and lives of humans, therefore the development of novel and efficient antibacterial strategies and drugs is urgently needed. Herein, a series of highly biocompatible lysine modified enzymatic hydrolysis lignins (EHL-Lys-x) were synthesized using the Mannich reaction. The sterilizing efficiency of EHL-Lys-2.0 against S. aureus and E. coli at 20 mg mL^-1 is 93% and 50%, respectively, which is 26% higher than pure EHL. Quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) analysis showed that the adsorption and adhesive force between EHL-Lys-x and bacteria increase with the increased amount of grafting of Lys on EHL owing to the increase of the electrostatic interaction between the EHL-Lys-x and bacteria, which results in an improvement in the antimicrobial activity of EHL-Lys-x. Subsequently, EHL-Lys-x combined with alkyl polyglucoside (APG) was used to stabilize the high internal phase emulsion containing curcumin (HIPEs-cur). The dispersed phase fraction of HIPE-cur is 87 vol%, which is the highest internal phase reported to date in the medical research area. The highest residual levels of curcumin in HIPEs are 60-fold, 3-fold and 5-fold compared to that in bulk oil after treatment with UV radiation, thermal emittance and after storage, respectively. The minimum inhibitory concentrations of HIPEs-cur against S. aureus and E. coli were found to be 1.56 and 6.25 mg mL^-1, respectively, which are far higher than that of pure EHL-Lys-x. This strategy not only increases the chemical stability and bioavailability of curcumin, but also provides a novel method for the application of lignin in biomedical science.

Facile Synthesis of Thermo-Sensitive Composite Hydrogel with Well Dispersed Ag Nanoparticles for Application in Superior Antibacterial Infections

In this study, we have described a facile process for fabrication of multifunctional composite hydrogel, in which sodium alginate was subjected to cross-linking using Ca²⁺ derived from ZnO/CaCO₃/Ag composite nanospheres. The ZnO/CaCO₃/Ag composite nanospheres were prepared based on our previously reported AA-[Zn(OH)₄]^2- composite nanosphere reaction conducted with silver and calcium salt following hydrothermal method, that led to the disintegration and release of Ca²⁺ under acidic conditions for application as a cross-linking agentto catalyze reaction with sodium alginate. Ag nanoparticles were well-dispersed in the multifunctional composite hydrogel, exhibiting excellent antibacterial activity. Additionally, polydopamine (PDA) with photothermal effect was also added to obtain a multifunctional composite hydrogel, and this hydrogel showed photothermal conversion performance and facilitated the release of Ag⁺ to achieve the rapid antibacterial effect. Simultaneously, PDA NPs could scavenge free radicals and improve cell adhesion. All such features would promote wound healing. The potent antimicrobial activity of the prepared composite hydrogel was demonstrated in the mouse model of S. aureus infection, and biosafety of the hydrogel was confirmed by conducting histopathological examination in the mouse model. This type of multifunctional hydrogel wound dressing with photosensitive and antibacterial properties presents with broad applications and prospects in antibacterial treatment.