A Dual-Responsive Antibiotic-Loaded Nanoparticle Specifically Binds Pathogens and Overcomes Antimicrobial-Resistant Infections

Magnetic silk fibroin nanospheres loaded with amphiphilic polypeptides and antibiotics for biofilm eradication

The eradication of established biofilms is a highly challenging task, due to the protective barrier effect of extracellular polymeric substances (EPS) and the presence of persister cells. Both increased drug permeability and elimination of persister cells are essential for the eradication of biofilms. Here, magnetic silk fibroin nanospheres loaded with antibiotics and host defense peptide (HDP) mimics (MPSN/S@P) were developed to demonstrate a new strategy for biofilm eradication. As an HDP mimic, an amphiphilic polypeptide containing 90% L-lysine and 10% L-valine (Lys90Val10) was selected for loading onto magnetic silk fibroin nanospheres via electrostatic interactions. Lys90Val10 exhibited excellent antibacterial activities against both planktonic and persister cells of Staphylococcus aureus (S. aureus). As a representative of the hydrophobic drug, spiramycin (SPM) was conveniently embedded into the β-sheet domain during the self-assembly process of silk fibroin. The sustained release of SPM during biofilm eradication enhanced the antibacterial efficacy of MPSN/S@P. The antibacterial test demonstrated that the extract from the MPSN/S@P suspension can kill both planktonic and persister cells of S. aureus, as well as inhibiting biofilm formation. Importantly, with the assistance of magnetic guidance and photothermal effects derived from Fe3O4 nanoparticles (Fe3O4 NPs), over 92% of bacteria in the biofilm were killed by MPSN/S@P, indicating the successful eradication of mature biofilms. The simple preparation method, integration of photothermal and magnetic responsiveness, and persister cell killing functions of MPSN/S@P provide an accessible strategy and illustrative paradigm for efficient biofilm eradication.

Smart self-defensive coatings with bacteria-triggered antimicrobial response for medical devices

Bacterial colonization and biofilm formation on medical devices represent one of the most urgent and critical challenges in modern healthcare. These issues not only pose serious threats to patient health by increasing the risk of infections but also exert a considerable economic burden on national healthcare systems due to prolonged hospital stays and additional treatments. To address this challenge, there is a need for smart, customized biomaterials for medical device fabrication, particularly through the development of surface modification strategies that prevent bacterial adhesion and the growth of mature biofilms. This review explores three bioinspired approaches through which antibacterial and antiadhesive coatings can be engineered to exhibit smart, stimuli-responsive features. This responsiveness is greatly valuable as it provides the coatings with a controlled, on-demand antibacterial response that is activated only in the presence of bacteria, functioning as self-defensive coatings. Such coatings can be designed to release antibacterial agents or change their surface properties/conformation in response to specific stimuli, like changes in pH, temperature, or the presence of bacterial enzymes. This targeted approach minimizes the risk of developing antibiotic resistance and reduces the need for continuous, high-dose antibacterial treatments, thereby preserving the natural microbiome and further reducing healthcare costs. The final part of the review reports a critical analysis highlighting the potential improvements and future evolutions regarding antimicrobial self-defensive coatings and their validation.

Dual osmotic controlled release platform for antibiotics to overcome antimicrobial-resistant infections and promote wound healing

Methicillin-Resistant Staphylococcus aureus forming into biofilms can trigger chronic inflammation and disrupt skin wound healing processes. Prolonged and excessive use of antibiotics can expedite the development of resistance, primarily because of their limited ability to penetrate microbial membranes and biofilms, especially antibiotics with intracellular drug targets. Herein, we devise a strategy in which virus-inspired nanoparticles control the release of antibiotics through rapid penetration into both bacterial cells and biofilms, thereby combating antimicrobial-resistant infections and promoting skin wound healing. Lipid-based nanoparticles based on stearamine and cholesterol were designed to mimic viral highly ordered nanostructures. To mimic the arginine-rich fragments in viral protein transduction domains, the primary amines on the surface of the lipid-based nanoparticles were exchanged by guanidine segments. Levofloxacin, an antibiotic that inhibits DNA replication, was chosen as the model drug to be incorporated into nanoparticles. Hyaluronic acid was coated on the surface of nanoparticles acting as a capping agent to achieve bacterial-specific degradation and guanidine explosion in the bacterial microenvironment. Our virus-inspired nanoparticles displayed long-acting antibacterial effects and powerful biofilm elimination to overcome antimicrobial-resistant infections and promote skin wound healing. This work demonstrates the ability of virus-inspired nanoparticles to achieve a dual penetration of microbial cell membranes and biofilm structures to address antimicrobial-resistant infections and trigger skin wound healing.

Cascade-targeting polymeric particles eliminate intracellular C. neoformans in fungal infection therapy

C. neoformans, a life-threatening invasive fungal pathogen, can hijack the pulmonary macrophages as 'Trojan horse', leading to cryptococcal meningitis and recurrence. Combatting these elusive fungi has posed a long-standing challenge. Here, we report an inhaled cascade-targeting drug delivery platform that can sequentially target host cells and intracellular fungi. The delivery system involves encapsulating amphotericin B (AMB) into polymeric particles decorated with AMB, creating a unique surface pattern, denoted as APP@AMB. The surface topology of APP@AMB guides the efficient macrophages internalization and intracellular drugs accumulation. Following endocytosis, the surface-functionalized AMB specifically targets intracellular fungi by binding to ergosterol in the fungal membrane, as demonstrated through co-localization studies using confocal microscopy. Through on-site AMB delivery, APP@AMB displays superior efficacy in eliminating C. neoformans in the lungs and brain compared to free AMB following inhalation in infected mice. Additionally, APP@AMB significantly alleviates the nephrotoxicity associated with free AMB inhalation therapy. Thus, this biocompatible delivery system enabling host cells and intracellular fungi targeting in a cascade manner, provides a new avenue for the therapy of fungal infection.

From bench to bedside: Platelet biomimetic nanoparticles as a promising carriers for personalized drug delivery

In recent decades, there has been a burgeoning interest in cell membrane coating strategies as innovative approach for targeted delivery systems in biomedical applications. Platelet membrane-coated nanoparticles (PNPs), in particular, are gaining interest as a new route for targeted therapy due to their advantages over conventional drug therapies. Their stepwise approach blends the capabilities of the natural platelet membrane (PM) with the adaptable nature of manufactured nanomaterials, resulting in a synergistic combination that enhances drug delivery and enables the development of innovative therapeutics. In this context, we present an overview of the latest advancements in designing PNPs with various structures tailored for precise drug delivery. Initially, we describe the types, preparation methods, delivery mechanisms, and specific advantages of PNPs. Next, we focus on three critical applications of PNPs in diseases: vascular disease therapy, cancer treatment, and management of infectious diseases. This review presents our knowledge of PNPs, summarizes their advancements in targeted therapies and discusses the promising potential for clinical translation of PNPs.

Tailored Phototherapy Agent by Infection Site In Situ Activated Against Methicillin-Resistant S. aureus

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is a promising treatment approach for multidrug resistant infections. PDT/PTT combination therapy can more efficiently eliminate pathogens without drug resistance. The key to improve the efficacy of photochemotherapy is the utilization efficiency of non-radiation energy of phototherapy agents. Herein, a facile phototherapy molecule (SCy-Le) with the enhancement of non-radiative energy transfer is designed by an acid stimulation under a single laser. Introduction of the protonated receptor into SCy-Le results in a distorted intramolecular charge in the infected acidic microenvironment, pH ≈ 5.5, which in turn, enhances light capture, reduces the singlet-triplet transition energies (ΔES1-T1), promotes electron system crossing, enhances capacity of reactive oxygen species generation, and causes a significant increase in temperature by improving vibrational relaxation. SCy-Le shows more than 99% bacterial killing rate against both methicillin-resistant Staphylococcus aureus and its biofilms in vitro and causes bacteria-induced wound healing in mice. This work will provide a new perspective for the design of phototherapy agents, and the emerging photochemotherapy will be a promising approach to combat the problem of antibiotic resistance.

Nitrite reductase-mimicking catalysis temporally regulating nitric oxide concentration gradient adaptive for antibacterial therapy

The unique bacterial infection microenvironment (IME) usually requires complicated design of nanomaterials to adapt to IME for enhancing antibacterial therapy. Here, an alternative IME adaptative nitrite reductase-mimicking nanozyme is constructed by in situ growth of ultrasmall copper sulfide clusters on the surface of a nanofibrillar lysozyme assembly (NFLA/CuS NHs), which can temporally regulate nitric oxide (NO) gradient concentration to kill bacteria initially and promote tissue regeneration subsequently. Benefiting from a copper nitrite reductase (CuNIR)-inspired structure with CuS cluster as active center and NFLA as skeleton, NFLA/CuS NHs efficiently boost the catalytic reduction of nitrite to NO. The inherent supramolecular fibrillar networks displays excellent bacterial capture capability, facilitating initial high-concentration NO attacks on the bacteria. The subsequent catalytic release of low-concentration NO by NFLA/CuS NHs-mediated nitrite reduction remarkably promotes cell migration and angiogenesis. This work paves the way for dynamically eliminating MDR bacterial infection and promoting tissue regeneration in a simple and smart way through CuNIR-mimicking catalysis.

AMP-Mimetic Antimicrobial Polymer-Involved Synergic Therapy with Various Coagents for Improved Efficiency

The misuse of antibiotics contributes to the emergence of multidrug-resistant (MDR) bacteria. Infections caused by MDR bacteria are rapidly evolving into a significant threat to global healthcare due to the lack of effective and safe treatments. Antimicrobial peptides (AMPs) with broad-spectrum antibacterial activity kill bacteria generally through a membrane disruption mechanism; hence, they tend not to induce resistance readily. However, AMPs exhibit disadvantages, such as high cost and susceptibility to proteolytic degradation, which limit their clinical application. AMP-mimetic antimicrobial polymers, with low cost, stability to proteolysis, broad-spectrum antimicrobial activity, negligible antimicrobial resistance, and rapid bactericidal effect, have received extensive attention as a new type of antibacterial drugs. Lately, AMP-mimetic polymer-involved synergic therapy provides a superior alternative to combat MDR bacteria by distinct mechanisms. In this Review, we summarize the AMP-mimetic antimicrobial polymers involved in synergic therapy, particularly focusing on the different combinations between the polymers with commercially available antimicrobials, organic small molecule photosensitizers, inorganic nanomaterials, and nitric oxide.

Precise antibiotic delivery to the lung infection microenvironment boosts the treatment of pneumonia with decreased gut dysbiosis

Bacterial pneumonia is a common disease with significant health risks. However, the overuse antibiotics in clinics face challenges such as inadequate targeting and limited drug utilization, leading to drug resistance and gut dysbiosis. Herein, a dual-responsive lung inflammatory tissue targeted nanoparticle (LITTN), designed for targeting lung tissue and bacteria, is screened from a series of prepared nanoparticles consisting of permanent cationic lipids, acid-responsive lipids, and reactive oxygen species-responsive and phenylboronic acid-modified lipids with different surface properties. Such nanoparticle is further verified to enhance the adsorption of vitronectin in serum. Additionally, the optimized nanoparticle exhibits more positive charge and coordination of boric acid with cis-diol in the infected microenvironment, facilitating electrostatic interactions with bacteria and biofilm penetration. Importantly, the antibacterial efficiency of dual-responsive rifampicin-loaded LITTN (Rif@LITTN) against methicillin-resistant staphylococcus aureus is 10 times higher than that of free rifampicin. In a mouse model of bacterial pneumonia, the intravenous administration of Rif@LITTN could precisely target the lungs, localize in the lung infection microenvironment, and trigger the responsive release of rifampicin, thereby effectively alleviating lung inflammation and reducing damage. Notably, the targeted delivery of rifampicin helps protect against antibiotic-induced changes in the gut microbiota. This study establishes a new strategy for precise delivery to the lung-infected microenvironment, promoting treatment efficacy while minimizing the impact on gut microbiota. STATEMENT OF SIGNIFICANCE: Intravenous antibiotics play a critical role in clinical care, particularly for severe bacterial pneumonia. However, the inability of antibiotics to reach target tissues causes serious side effects, including liver and kidney damage and intestinal dysbiosis. Therefore, achieving precise delivery of antibiotics is of great significance. In this study, we developed a novel lung inflammatory tissue-targeted nanoparticle that could target lung tissue after intravenous administration and then target the inflammatory microenvironment to trigger dual-responsive antibiotics release to synergistically treat pneumonia while maintaining the balance of gut microbiota and reducing the adverse effects of antibiotics. This study provides new ideas for targeted drug delivery and reference for clinical treatment of pneumonia.

Bioinspired Hybrid Nanostructured PEEK Implant with Enhanced Antibacterial and Anti-inflammatory Synergy

Implant-associated infections and excessive immune responses are two major postsurgical issues for successful implantation. However, conventional strategies including antibiotic treatment and inflammatory regulation are always compromised due to the comodification of various biochemical agents and instances of functional interference. It is imperative to provide implant surfaces with satisfactory antibacterial and anti-inflammatory properties. Here, a dual-effect nanostructured polyetheretherketone (PEEK) surface (NP@PDA/Zn) with bionic mechano-bactericidal nanopillars and immobilized immunomodulatory Zn2+ is designed. The constructed hybrid nanopillars display remarkable antibacterial performance against Gram-negative and Gram-positive strains through the synergy of physical and chemical bactericidal effects imposed by nanopillars and Zn2+. Meanwhile, the immunoregulatory property is evaluated through the investigation of macrophage polarization both in vitro and in vivo, and the results reveal that NP@PDA/Zn could downregulate the expression of M1-related cytokines and decrease the M1 macrophage recruitment to lower the inflammatory response. Notably, the surface exhibited exceptional biocompatibility with discerning biocidal activity between bacterial and mammalian cells and antioxidant performance that effectively scavenges ROS, minimizing potential cytotoxicity. Taken together, NP@PDA/Zn presents a convenient and promising strategy of combining synergistic bactericidal activity and inflammatory regulation without any mutual interference, which can support the development of multifunctional implant-associated materials.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

Multimodal nanoimmunotherapy engages neutrophils to eliminate Staphylococcus aureus infections

The increasing prevalence of antimicrobial resistance in Staphylococcus aureus necessitates alternative therapeutic approaches. Neutrophils play a crucial role in the fight against S. aureus but suffer from deficiencies in function leading to increased infection. Here we report a nanoparticle-mediated immunotherapy aimed at potentiating neutrophils to eliminate S. aureus. The nanoparticles consist of naftifine, haemoglobin (Hb) and a red blood cell membrane coating. Naftifine disrupts staphyloxanthin biosynthesis, Hb reduces bacterial hydrogen sulfide levels and the red blood cell membrane modifies bacterial lipid composition. Collectively, the nanoparticles can sensitize S. aureus to host oxidant killing. Furthermore, in the infectious microenvironment, Hb triggers lipid peroxidation in S. aureus, promoting neutrophil chemotaxis. Oxygen supplied by Hb can also significantly enhance the bactericidal capability of the recruited neutrophils by restoring neutrophil respiratory burst via hypoxia relief. This multimodal nanoimmunotherapy demonstrates excellent therapeutic efficacy in treating antimicrobial-resistant S. aureus persisters, biofilms and S. aureus-induced infection in mice.

Phage-based delivery systems: engineering, applications, and challenges in nanomedicines

Bacteriophages (phages) represent a unique category of viruses with a remarkable ability to selectively infect host bacteria, characterized by their assembly from proteins and nucleic acids. Leveraging their exceptional biological properties and modifiable characteristics, phages emerge as innovative, safe, and efficient delivery vectors. The potential drawbacks associated with conventional nanocarriers in the realms of drug and gene delivery include a lack of cell-specific targeting, cytotoxicity, and diminished in vivo transfection efficiency. In contrast, engineered phages, when employed as cargo delivery vectors, hold the promise to surmount these limitations and attain enhanced delivery efficacy. This review comprehensively outlines current strategies for the engineering of phages, delineates the principal types of phages utilized as nanocarriers in drug and gene delivery, and explores the application of phage-based delivery systems in disease therapy. Additionally, an incisive analysis is provided, critically examining the challenges confronted by phage-based delivery systems within the domain of nanotechnology. The primary objective of this article is to furnish a theoretical reference that contributes to the reasoned design and development of potent phage-based delivery systems.

Charge adaptive phytochemical-based nanoparticles for eradication of methicillin-resistant staphylococcus aureus biofilms

The intrinsic resistance of MRSA coupled with biofilm antibiotic tolerance challenges the antibiotic treatment of MRSA biofilm infections. Phytochemical-based nanoplatform is a promising emerging approach for treatment of biofilm infection. However, their therapeutic efficacy was restricted by the low drug loading capacity and lack of selectivity. Herein, we constructed a surface charge adaptive phytochemical-based nanoparticle with high isoliquiritigenin (ISL) loading content for effective treatment of MRSA biofilm. A dimeric ISL prodrug (ISL-G2) bearing a lipase responsive ester bond was synthesized, and then encapsulated into the amphiphilic quaternized oligochitosan. The obtained ISL-G2 loaded NPs possessed positively charged surface, which allowed cis-aconityl-d-tyrosine (CA-Tyr) binding via electrostatic interaction to obtain ISL-G2@TMDCOS-Tyr NPs. The NPs maintained their negatively charged surface, thus prolonging the blood circulation time. In response to low pH in the biofilms, the fast removal of CA-Tyr led to a shift in their surface charge from negative to positive, which enhanced the accumulation and penetration of NPs in the biofilms. Sequentially, the pH-triggered release of d-tyrosine dispersed the biofilm and lipase-triggered released of ISL effectively kill biofilm MRSA. An in vivo study was performed on a MRSA biofilm infected wound model. This phytochemical-based system led to ∼2 log CFU (>99 %) reduction of biofilm MRSA as compared to untreated wound (P < 0.001) with negligible biotoxicity in mice. This phytochemical dimer nanoplatform shows great potential for long-term treatment of resistant bacterial infections.

An Antibiotic Nanobomb Constructed from pH-Responsive Chemical Bonds in Metal-Phenolic Network Nanoparticles for Biofilm Eradication and Corneal Ulcer Healing

In the treatment of refractory corneal ulcers caused by Pseudomonas aeruginosa, antibacterial drugs delivery faces the drawbacks of low permeability and short ocular surface retention time. Hence, novel positively-charged modular nanoparticles (NPs) are developed to load tobramycin (TOB) through a one-step self-assembly method based on metal-phenolic network and Schiff base reaction using 3,4,5-trihydroxybenzaldehyde (THBA), ε-poly-ʟ-lysine (EPL), and Cu2+ as matrix components. In vitro antibacterial test demonstrates that THBA-Cu-TOB NPs exhibit efficient instantaneous sterilization owing to the rapid pH responsiveness to bacterial infections. Notably, only 2.6 µg mL-1 TOP is needed to eradicate P. aeruginosa biofilm in the nano-formed THBA-Cu-TOB owing to the greatly enhanced penetration, which is only 1.6% the concentration of free TOB (160 µg mL-1). In animal experiments, THBA-Cu-TOB NPs show significant advantages in ocular surface retention, corneal permeability, rapid sterilization, and inflammation elimination. Based on molecular biology analysis, the toll-like receptor 4 and nuclear factor kappa B signaling pathways are greatly downregulated as well as the reduction of inflammatory cytokines secretions. Such a simple and modular strategy in constructing nano-drug delivery platform offers a new idea for toxicity reduction, physiological barrier penetration, and intelligent drug delivery.

ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Advanced application of carbohydrate-based micro/nanoparticles for rheumatoid arthritis

Rheumatoid arthritis (RA) is a kind of synovitis and progressive joint destruction disease. Dysregulated immune cell activation, inflammatory cytokine overproduction, and subsequent reactive oxidative species (ROS) production contribute to the RA process. Carbohydrates, including cellulose, chitosan, alginate and dextran, are among the most abundant and important biomolecules in nature and are widely used in biomedicine. Carbohydrate-based micro/nanoparticles(M/NPs) as functional excipients have the ability to improve the bioavailability, solubility and stability of numerous drugs used in RA therapy. For on-demand therapy, smart reactive M/NPs have been developed to respond to a variety of chemical and physical stimuli, including light, temperature, enzymes, pH and ROS, alternating their physical and macroscopic properties, resulting in innovative new drug delivery systems. In particular, advanced products with targeted dextran or hyaluronic acid are exploiting multiple beneficial properties at the same time. In addition to those that respond, there are promising new derivatives in development with microenvironment and chronotherapy effects. In this review, we provide an overview of these recent developments and an outlook on how this class of agents will further shape the landscape of drug delivery for RA treatment.

Mussel-Inspired Polymer-Based Coating Technology for Antifouling and Antibacterial Properties

Zwitterionic coatings provide a promising antifouling strategy against biofouling adhesion. Quaternary ammonium cationic polymers can effectively kill bacteria on the surface, owing to their positive charges. This strategy can avoid the release of toxic biocides, which is highly desirable for constructing coatings for biomedical devices. The present work aims to develop a facile method by covalently grafting zwitterionic and cationic copolymers containing aldehydes to the remaining amine groups of self-polymerized dopamine. Reversible addition-fragmentation chain transfer polymerization was used to copolymerize either zwitterionic 2-methacryloyloxyethyl phosphorylcholine monomer (MPC) or cationic 2-(methacryloyloxy)ethyl trimethylammonium monomer (META) with 4-formyl phenyl methacrylate monomer (FPMA), and the formed copolymers poly(MPC-st-FPMA) and poly(META-st-FPMA) are denoted as MPF and MTF, respectively. MPF and MTF copolymers were then covalently grafted onto the amino groups of polydopamine-coated surfaces. PDA/MPF/MTF-coated surfaces exhibited antibacterial and antifouling properties against S. aureus, E. coli, and bovine serum albumin protein. In addition, they showed excellent viability of normal human lung fibroblast cells MRC-5. We expect the facile surface modification strategy discussed here to be applicable to medical device manufacturing.

Polymeric Nanoparticles for Drug Delivery

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of more sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Furthermore, polymeric nanoparticles have the ability to navigate various biological barriers to precisely target specific sites within the body, encapsulate a diverse range of therapeutic cargo and efficiently release this cargo in response to internal and external stimuli. However, despite these remarkable advantages, the presence of polymeric nanoparticles in wider clinical application is minimal. This review will provide a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles. The biological barriers affecting drug delivery will be outlined first, followed by a comprehensive description of the various nanoparticle designs and preparation methods, beginning with the polymers on which they are based. The review will meticulously explore the current performance of polymeric nanoparticles against a myriad of diseases including cancer, viral and bacterial infections, before finally evaluating the advantages and crucial challenges that will determine their wider clinical potential in the decades to come.

Dextran-based antibacterial hydrogel-derived fluorescent sensors for the visual monitoring of AgNPs

The unpredictable release behavior of metal nanoparticles/metal ions from metal nanoparticle-loaded hydrogels, without a suitable in situ detection method, is resulting in serious cytotoxicity. To optimize the preparation and design of antibacterial hydrogels for in situ detection of metal nanoparticles, an in-situ detection platform based on the fluorescence signal change caused by the potential surface energy transfer of silver nanoparticles (AgNPs) and carbon dots (CD) through silver mirror reaction and Schiff base reaction was established. The antimicrobial test results show that the composite antimicrobial hydrogel, with lower dosages of AgNPs and CD, exhibited a higher inhibition rate of 99.1 % against E. coli and 99.8 % against S. aureus compared to the single antimicrobial component. This suggests a potential synergistic antimicrobial activity. Furthermore, the fluorescence detection platform was established with a difference of <3 μg between detected values and actual values over a period of 72 h. This demonstrates the excellent in situ detection capability of the hydrogel in antimicrobial-related applications.

Tobramycin-mediated self-assembly of DNA nanostructures for targeted treatment of Pseudomonas aeruginosa-infected lung inflammation

Pseudomonas aeruginosa (PA) is one of the most common multidrug-resistant pathogens found in clinics, often manifesting as biofilms. However, due to the emergence of superbugs in hospitals and the overuse of antibiotics, the prevention and treatment of PA infections have become increasingly challenging. Utilizing DNA nanostructures for packaging and delivering antibiotics presents an intervention strategy with significant potential. Nevertheless, construction of functional DNA nanostructures with multiple functionalities and enhanced stability in physiological settings remains challenging. In this study, the authors propose a magnesium-free assembly method that utilizes tobramycin (Tob) as a mediator to assemble DNA nanostructures, allowing for the functionalization of DNA nanostructures by combining DNA and antibiotics. Additionally, our study incorporates maleimide-modified DNA into the nanostructures to act as a targeting moiety specifically directed towards the pili of PA. The targeting ability of the constructed functional DNA nanostructure significantly improves the local concentration of Tob, thereby reducing the side effects of antibiotics. Our results demonstrate the successful construction of a maleimide-decorated Tob/DNA nanotube (NTTob-Mal) for the treatment of PA-infected lung inflammation. The stability and biocompatibility of NTTob-Mal are confirmed, highlighting its potential for clinical applications. Furthermore, its specificity in recognizing and adhering to PA has been validated. In vitro experiments have shown its efficacy in inhibiting PA biofilm formation, and in a murine model, NTTob-Mal has exhibited significant therapeutic effectiveness against PA-induced pneumonia. In summary, the proposed antibiotic drug-mediated DNA nanostructure assembly approach holds promise as a novel strategy for targeted treatment of PA infections.

A disulfide molecule-vancomycin nanodrug delivery system efficiently eradicates intracellular bacteria

Intracellular bacteria often lead to chronic and recurrent infections; however, most of the known antibiotics have poor efficacy against intracellular bacteria due to their poor cell membrane penetration efficiency into the cytosol. Here, a thiol-mediated nanodrug delivery system, named Van-DM NPs, was developed to improve vancomycin's penetration efficiency and intracellular antibacterial activities. Van-DM NPs were prepared through self-assembly of vancomycin (Van) and the disulfide molecule (DM) in NaOH buffer solution. On the one hand, the disulfide exchange reaction between Van-DM NPs and the bacterial surface enhances vancomycin accumulation in bacteria, increasing the local concentration of vancomycin. On the other hand, the disulfide exchange reaction between Van-DM NPs and the mammalian cell membrane triggered the translocation of Van-DM NPs across the mammalian cell membrane into the cell cytosol. These dual mechanisms promote antibacterial activities of vancomycin against both extracellular and intracellular bacteria S. aureus. Furthermore, in an intravenous S. aureus infection mouse model, Van-DM NPs exhibited high antibacterial capability and efficiently reduced the bacterial load in liver and spleen, where intracellular bacteria tend to reside. Altogether, the reported Van-DM NPs would be highly promising against intracellular pathogenic infections.

Cell membrane-coated biomimetic nanomedicines: productive cancer theranostic tools

As the second-leading cause of human death, cancer has drawn attention in the area of biomedical research and therapy from all around the world. Certainly, the development of nanotechnology has made it possible for nanoparticles (NPs) to be used as a carrier for delivery systems in the treatment of tumors. This is a biomimetic approach established to craft remedial strategies comprising NPs cloaked with membrane obtained from various natural cells like blood cells, bacterial cells, cancer cells, etc. Here we conduct an in-depth exploration of cell membrane-coated NPs (CMNPs) and their extensive array of applications including drug delivery, vaccination, phototherapy, immunotherapy, MRI imaging, PET imaging, multimodal imaging, gene therapy and a combination of photothermal and chemotherapy. This review article provides a thorough summary of the most recent developments in the use of CMNPs for the diagnosis and treatment of cancer. It critically assesses the state of research while recognizing significant accomplishments and innovations. Additionally, it indicates ongoing problems in clinical translation and associated queries that warrant deeper research. By doing so, this study encourages creative thinking for future projects in the field of tumor therapy using CMNPs while also educating academics on the present status of CMNP research.

Progress of stimulus responsive nanosystems for targeting treatment of bacterial infectious diseases

In recent decades, due to insufficient concentration at the lesion site, low bioavailability and increasingly serious resistance, antibiotics have become less and less dominant in the treatment of bacterial infectious diseases. It promotes the development of efficient drug delivery systems, and is expected to achieve high absorption, targeted drug release and satisfactory therapy effects. A variety of endogenous stimulation-responsive nanosystems have been constructed by using special infection microenvironments (pH, enzymes, temperature, etc.). In this review, we firstly provide an extensive review of the current research progress in antibiotic treatment dilemmas and drug delivery systems. Then, the mechanism of microenvironment characteristics of bacterial infected lesions was elucidated to provide a strong theoretical basis for bacteria-targeting nanosystems design. In particular, the discussion focuses on the design principles of single-stimulus and dual-stimulus responsive nanosystems, as well as the use of endogenous stimulus-responsive nanosystems to deliver antimicrobial agents to target locations for combating bacterial infectious diseases. Finally, the challenges and prospects of endogenous stimulus-responsive nanosystems were summarized.

Microenvironment responsive charge-switchable nanoparticles act on biofilm eradication and virulence inhibition for chronic lung infection treatment

Chronic pulmonary infection caused by Pseudomonas aeruginosa (P. aeruginosa) is a common lung disease with high mortality, posing severe threats to public health. Highly resistant biofilm and intrinsic resistance make P. aeruginosa hard to eradicate, while powerful virulence system of P. aeruginosa may give rise to the recurrence of infection and eventual failure of antibiotic therapy. To address these issues, infection-microenvironment responsive nanoparticles functioning on biofilm eradication and virulence inhibition were simply prepared by electrostatic complexation between dimethylmaleic anhydride (DA) modified negatively charged coating and epsilon-poly(l-lysine) derived cationic nanoparticles loaded with azithromycin (AZI) (DA-AZI NPs). Charge reversal responsive to acidic condition enabled DA-AZI NPs to successively penetrate through both mucus and biofilms, followed by targeting to P. aeruginosa and permeabilizing its outer/inner membrane. Then in situ released AZI, which was induced by the lipase-triggered NPs dissociation, could easily enter into bacteria to take effects. DA-AZI NPs exhibited enhanced eradication activity against P. aeruginosa biofilms with a decrease of >99.999% of bacterial colonies, as well as remarkable inhibitory effects on the production of virulence factors and bacteria re-adhesion & biofilm re-formation. In a chronic pulmonary infection model, nebulization of DA-AZI NPs into infected mice resulted in prolonged retention and increased accumulation of the NPs in the infected sites of the lungs. Moreover, they significantly reduced the burden of P. aeruginosa, effectively alleviating lung tissue damages and inflammation. Overall, the proposed DA-AZI NPs highlight an innovative strategy for treating chronic pulmonary infection.

Bletilla Striata polysaccharides thermosensitive gel for photothermal treatment of bacterial infection

Skin is the most important defense shield which touched external environment directly. Effectively clearing microbes in infected wound via non-antibiotic therapy is crucial for the promotion of recovery in complex biological environments, and the wound healing is a crucial process after sterilization to avoid superinfection. Herein, a kind of Prussian blue-based photothermal responsive gel, Bletilla striata polysaccharide-mingled, isatin-functionalized Prussian blue gel (PB-ISA/BSP gel) was reported for effective treatment of bacterial infection and wound healing. The introduction of effective components of traditional Chinese medicine (TCM), isatin (ISA), enhanced the efficiency of sterilization synergistically. Furthermore, the process of wound healing was promoted by Bletilla striata polysaccharides (BSP). PB-ISA@BSP had a considerable antibacterial rate with 98.5 % under an 808 nm laser for 10 min in vitro. Besides, PB-ISA/BSP gel showed an effective antibacterial efficacy in vivo and a fast wound healing rate as well. The as-prepared functional particles can invade and destroy bacteria membrane to kill microbes. This work highlights that PB-ISA/BSP gel is a promising antibacterial agent based on synergistically enhanced photothermal effect and wound healing promotion ability and provides inspiration for future therapy based on the synergy between photothermal agent and active components in TCM.

Smart chitosan-based microgels for enhanced photothermal-assisted antibacterial activity

During recent years, antibiotic-resistant bacteria have rapidly emerged owing to the irrational use of antibiotics, rendering a global problem. Currently, few studies introduce customized antibacterial nanoplatforms to overcome antibiotic-resistance according to specific characteristic of bacteria, rather than abuse of antibiotic. Herein, with regard to personalized antibacterial nanoplatform, we design a novel antibiotic delivery nanocarrier composed of polyaniline-grafted-chitosan, presenting pH-responsive, conductive, photothermal, and biodegradable properties. After treatment with divalent anion (SO42-), the negatively charged nanocarriers are obtained for improving the loading efficacy of cationic vancomycin. Meanwhile, the controlled vancomycin release is achieved by lysozyme-triggered degradation of the nanocarrier. With the assistance of photothermal effect, the photothermal-assisted antibacterial effect of the nanocarriers have been effectively enhanced rather than that of a single antibacterial effect of vancomycin. Owing to the low heat resistance of Escherichia coli, photothermal effect can break the antibiotic-resistant bacteria membrane to render the convenient antibiotic entry, leading to the improved antibacterial efficacy. Therefore, the customization of a photothermal-assisted antibacterial on account of the characteristic of specific bacteria can definitely expand our arsenal for enhancing the antibacterial effect against antibiotic-resistant bacteria.

Supramolecular Nano-Assembly of Caffeate-Strengthened Phenylboronic Ester with Multistep ROS Scavenging Ability for Targeted Therapy of Acute Kidney Injury

Acute kidney injury (AKI) is a life-threatening complication with a considerable occurrence among patients. AKI is typically accompanied by an elevation in reactive oxidative species (ROS) in renal tissues, which is the main contributor to kidney damage. Herein, a supramolecular nano-assembly (Ser-HPEC) containing an ethyl caffeate-strengthened phenylboronic ester with ROS-triggered antioxidative ability is proposed for AKI-targeted therapy. Nano-assemblies can rapidly accumulate in the ischemia-reperfusion-injured kidney via kidney injury molecule-1 (Kim-1)-mediated homing ability of l-serine. By consuming pathological levels of ROS, two different antioxidants, ethyl caffeate and 4-hydroxybenzyl alcohol, are spontaneously released from a single module to relieve oxidative stress and diminish acute inflammation in injured renal tissue. The multistep ROS scavenging strategy combined with a precise targeting capability endows the aforementioned nano-assembly with effectiveness in preserving the integrity and functions of the injured kidney, providing new inspiration for the treatment of inflammatory diseases, including AKI.

Nanotechnology-Based Drug Delivery Systems to Control Bacterial-Biofilm-Associated Lung Infections

Airway mucus dysfunction and impaired immunological defenses are hallmarks of several lung diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary diseases, and are mostly causative factors in bacterial-biofilm-associated respiratory tract infections. Bacteria residing within the biofilm architecture pose a complex challenge in clinical settings due to their increased tolerance to currently available antibiotics and host immune responses, resulting in chronic infections with high recalcitrance and high rates of morbidity and mortality. To address these unmet clinical needs, potential anti-biofilm therapeutic strategies are being developed to effectively control bacterial biofilm. This review focuses on recent advances in the development and application of nanoparticulate drug delivery systems for the treatment of biofilm-associated respiratory tract infections, especially addressing the respiratory barriers of concern for biofilm accessibility and the various types of nanoparticles used to combat biofilms. Understanding the obstacles facing pulmonary drug delivery to bacterial biofilms and nanoparticle-based approaches to combatting biofilm may encourage researchers to explore promising treatment modalities for bacterial-biofilm-associated chronic lung infections.

An integrated quorum quenching biocatalytic nanoplatform for synergistic chemo-photothermal eradication of P. aeruginosa biofilm infections

Decontamination of biofilm-associated infections presents a significant challenge due to the physical and chemical barrier created by the formation of extracellular matrices. This barrier restricts the access of antibiotics to the bacterial communities within the biofilm and provides protection to the persister cells, potentially leading to antibiotic resistance. In this study, we have developed an integrated quorum quenching biocatalytic nanoplatform for the synergistic chemo-photothermal eradication of P. aeruginosa biofilm infections. Ciprofloxacin (Cip), a model antibiotic, was absorbed onto PDA NPs through π-π stacking. Additionally, acylase (AC) was immobilized on PDA NPs through Schiff base reaction and Michael addition, resulting in the formation of the biocatalytic nanoplatform (PDA-Cip-AC NPs). This biocatalytic nanoplatform was able to enzymatically degrade AHL signaling molecules, thus achieving efficient quorum quenching activity to prevent biofilm formation. Furthermore, the NIR light-triggered on-demand Ciprofloxacin release further enhanced the eradication of P. aeruginosa biofilm infections with a synergy of local hyperthermia. We envision that this integrated quorum quenching nanoplatform provides a reliable tool for combating P. aeruginosa biofilm infections. STATEMENT OF SIGNIFICANCE: An integrated quorum quenching biocatalytic nanoplatform has been developed for the eradication of P. aeruginosa biofilm infections. Quorum-sensing signals play a crucial role in modulating bacterial cell-to-cell communication, biofilm formation, and secretion of virulence factors. This biocatalytic nanoplatform efficiently degrades AHL signaling molecules, thereby blocking cell-to-cell communication and preventing biofilm formation. Additionally, local hyperthermia and on-demand Ciprofloxacin release were achieved through NIR irradiation, working synergistically to eradicate P. aeruginosa biofilm infections.

Designing peptide amphiphiles as novel antibacterials and antibiotic adjuvants against gram-negative bacteria

Gram-negative strains are intrinsically resistant to most antibiotics due to the robust and impermeable characteristic of their outer membrane. Self-assembling cationic peptide amphiphiles (PAs) have the ability to disrupt bacteria membranes, constituting an excellent antibacterial alternative to small molecule drugs that can be used alone or as antibiotic adjuvants to overcome bacteria resistance. PA1 (C16KHKHK), self-assembled into micelles, which exhibited low antibacterial activity against all strains tested, and showed strong synergistic antibacterial activity in combination with Vancomycin with a Fractional Inhibitory Concentration index (FICi) of 0.15 against E. coli. The molecules, PA2 (C16KRKR) and PA3 (C16AAAKRKR), also self-assembled into micelles, displayed a broad-spectrum antibacterial activity against all strains tested, and low susceptibility to resistance development over 21 days. Finally, PA1, PA 2 and PA3 displayed low cytotoxicity against mammalian cells, and PA2 showed a potent antibacterial activity and low toxicity in preliminary in vivo models using G. mellonella. The results show that PAs are a great platform for the future development of effective antibiotics to slow down the antibiotic resistance and can act as antibiotic adjuvants with synergistic mechanism of action, which can be repurposed for use with existing antibiotics commonly used to treat gram-positive bacteria to treat infections caused by gram-negative bacteria.

Natural antibacterial agent-based nanoparticles for effective treatment of intracellular MRSA infection

Intracellular MRSA is extremely difficult to eradicate by traditional antibiotics, leading to infection dissemination and drug resistance. A general lack of facile and long-term strategies to effectively eliminate intracellular MRSA. In this study, glabridin (GLA)-loaded pH-responsive nanoparticles (NPs) were constructed using cinnamaldehyde (CA)-dextran conjugates as carriers. These NPs targeted infected macrophages/MRSA via dextran mediation and effectively accumulated at the MRSA infection site. The NPs were then destabilized in response to the low pH of the lysosomes, which triggered the release of CA and GLA. The released CA downregulated the expression of cytotoxic pore-forming toxins, thereby decreasing the damage of macrophage and risk of the intracellular bacterial dissemination. Meanwhile, GLA could rapidly kill intracellularly entrapped MRSA with a low possibility of developing resistance. Using a specific combination of the natural antibacterial agents CA and GLA, NPs effectively eradicated intracellular MRSA with low toxicity to normal tissues in a MRSA-induced peritonitis model. This strategy presents a potential alternative for enhancing intracellular MRSA therapy, particularly for repeated and long-term clinical applications. STATEMENT OF SIGNIFICANCE: Intracellular MRSA infections are a growing threat to public health, and there is a general lack of a facile strategy for efficiently eliminating intracellular MRSA while reducing the ever-increasing drug resistance. In this study, pH-responsive and macrophage/MRSA-targeting nanoparticles were prepared by conjugating the phytochemical cinnamaldehyde to dextran to encapsulate the natural antibacterial agent glabridin. Using a combination of traditional Chinese medicine, the NPs significantly increased drug accumulation in MRSA and showed superior intracellular and extracellular bactericidal activity. Importantly, the NPs can inhibit potential intracellular bacteria dissemination and reduce the development of drug resistance, thus allowing for repeated treatment. Natural antibacterial agent-based drug delivery systems are an attractive alternative for facilitating the clinical treatment of intracellular MRSA infections.

Precision Dosing of Antibiotics and Potentiators by Hypoxia-Responsive Nanoparticles for Overcoming Antibiotic Resistance in Gram-Negative Bacteria

The stalling development of antibiotics, especially against intrinsically resistant Gram-negative pathogens associated with outer membranes, leads to an emerging antibiotic crisis across the globe. To breathe life into existing drugs, we herein report a hypoxia-responsive nanoparticle (NP) that encapsulates a hydrophobic antibiotic, rifampicin, and a cationic potentiator, polysulfonium. The simultaneous release of antibiotics and potentiators can be promoted and inhibited in response to the severity of bacterial-induced hypoxia, leading to antimicrobial dosing in a precision manner. Under the synergism of polysulfoniums with membrane-disruption capability, the NPs can intensively decrease the antibiotic dose by up to 66-95% in eliminating planktonic Gram-negative P. aeruginosa bacteria and achieve an 8-log reduction of bacteria in mature biofilms at rifampicin MIC. The NP formulation demonstrates that precision dosing of antibiotics and potentiators regulated by hypoxia provides a promising strategy to maximize efficacy and minimize toxicity in treating Gram-negative bacterial infection.

pH Window for High Selectivity of Ionizable Antimicrobial Polymers toward Bacteria

Antimicrobial polymers exhibit great potential for treating drug-resistant bacteria; however, designing antimicrobial polymers that can selectively kill bacteria and cause relatively low toxicity to normal tissues/cells remains a key challenge. Here, we report a pH window for ionizable polymers that exhibit high selectivity toward bacteria. Ionizable polymer PC6A showed the greatest selectivity (131.6) at pH 7.4, exhibiting low hemolytic activity and high antimicrobial activity against bacteria, whereas a very high or low protonation degree (PD) produced relatively low selectivity (≤35.6). Bactericidal mechanism of PC6A primarily comprised membrane lysis without inducing drug resistance even after consecutive incubation for 32 passages. Furthermore, PC6A demonstrated synergistic effects in combination with antibiotics at pH 7.4. Hence, this study provides a strategy for designing selective antimicrobial polymers.

Hierarchical Superstructure of Plant Polyphenol and Arginine Surfactant for Long-Lasting and Target-Selective Antimicrobial Application

Antimicrobial agents are massively used to disinfect the pathogen contaminated surfaces since the Corona Virus Disease 2019 (COVID-19) outbreak. However, their defects of poor durability, strong irritation, and high environmental accumulation are exposed. Herein, a convenient strategy is developed to fabricate long-lasting and target-selective antimicrobial agent with the special hierarchical structure through bottom-up assembly of natural gallic acid with arginine surfactant. The assembly starts from rodlike micelles, further stacking into hexagonal columns and finally interpenetrating into spherical assemblies, which avoid explosive release of antimicrobial units. The assemblies show anti-water washing and high adhesion on various surfaces; and thus, possess highly efficient and broad-spectrum antimicrobial activities even after using up to eleven cycles. Both in vitro and in vivo experiments prove that the assemblies are highly selective in killing pathogens without generating toxicity. The excellent antimicrobial virtues well satisfy the increasing anti-infection demands and the hierarchical assembly exhibits great potential as a clinical candidate.

Self-Adaptive Antibiofilm Effect and Immune Regulation by Hollow Cu2MoS4 Nanospheres for Treatment of Implant Infections

Implant infections are difficult to cure by traditional antibiotic therapy due to bacterial biofilm-induced antibiotic tolerance and impaired immune responses. To efficiently treat implant infections, therapeutic agents need to kill bacteria and regulate the inflammatory response of immune cells during the biofilm elimination process. Herein, multifunctional smart hollow Cu₂MoS₄ nanospheres (H-CMS NSs) with pH-responsive enzyme-like activities were prepared for self-adaptively eliminating biofilms and regulating the inflammation of macrophages in implant infections. During biofilm infection, the tissue microenvironment around implants is acidic. H-CMS NSs with oxidase (OXD)/peroxidase (POD)-like activities can catalyze reactive oxidative species (ROS) generation for directly killing bacteria and polarizing macrophages to a proinflammatory phenotype. Moreover, the POD-like activity and antibacterial property of H-CMS NSs can be further enhanced under ultrasound (US) irradiation. After the elimination of biofilms, the tissue microenvironment around implants shifts from acidic to neutral. H-CMS NSs show catalase (CAT)-like activity and eliminate excessive ROS, which polarizes macrophages to anti-inflammatory phenotype and promotes healing of infected tissue. This work provides a smart nanozyme with self-adaptive regulation of the antibiofilm activity and immune response by regulating ROS generation/elimination according to the different pathological microenvironments in implant infections during the different therapeutic stages.

Dual-targeted poly(amino acid) nanoparticles deliver drug combinations on-site: an intracellular synergistic strategy to eliminate intracellular bacteria

Multi-drug combinations are a common strategy for the treatment of intracellular bacterial infections. However, different internalized pathways and the accumulation of the composite drugs at different subcellular organelles very much reduce their efficacy. Herein, an intracellular synergistic strategy is proposed, which is realized by on-site delivery of a drug combination using a macrophage/intracellular bacterium-dual targeted drug delivery system (DDS). The DDS is fabricated by encapsulating vancomycin (Van) and curcumin (Cur) into poly(α-N-acryloyl-phenylalanine)-block-poly(β-N-acryloyl-D-aminoalanine-co-2-O-acetyl-α-D-mannosyloxy) nanoparticles, denoted by (Van + Cur)@F(AM) NPs. Mannose ligands on (Van + Cur)@F(AM) NPs trigger their specific internalization in macrophages, while aminoalanine moieties subsequently drive the NPs to target intracellular methicillin-resistant Staphylococcus aureus (MRSA). Thereafter, Van and Cur are durably released in a synergistic dose at the residence site of intracellular MRSA. Under this intracellular synergistic effect, (Van + Cur)@F(AM) NPs show superior elimination efficiency in vitro and in vivo compared to the control groups, including free Van, (Van + Cur), the DDS encapsulated Van and the DDSs separately-encapsulated Van and Cur. Furthermore, (Van + Cur)@F(AM) NPs significantly enhance the in vivo antibacterial capacity by modulating the immune response. Therefore, this dual-targeted DDS-assisted intracellular synergistic antibacterial strategy of drug combination is an effective therapeutic against intracellular bacteria.

Endocytosis-mediated redistribution of antibiotics targets intracellular bacteria

The increasing emergence and dissemination of antibiotic resistance pose a severe threat to overwhelming healthcare practices worldwide. The lack of new antibacterial drugs urgently calls for alternative therapeutic strategies to combat multidrug-resistant (MDR) bacterial pathogens, especially those that survive and replicate in host cells, causing relapse and recurrence of infections. Intracellular drug delivery is a direct efficient strategy to combat invasive pathogens by increasing the accumulation of antibiotics. However, the increased accumulation of antibiotics in the infected host cells does not mean high efficacy. The difficulty of treatment lies in the efficient intracellular delivery of antibiotics to the pathogen-containing compartments. Here, we first briefly review the survival mechanisms of intracellular bacteria to facilitate the exploration of potential antibacterial targets for precise delivery. Furthermore, we provide an overview of endocytosis-mediated drug delivery systems, including the biomedical and physicochemical properties modulating the endocytosis and intracellular redistribution of antibiotics. Lastly, we summarize the targets and payloads of recently described intracellular delivery systems and their modes of action against diverse pathogenic bacteria-associated infections. This overview of endocytosis-mediated redistribution of antibiotics sheds light on the development of novel delivery platforms and alternative strategies to combat intracellular bacterial pathogens.

Structural optimization of BODIPY photosensitizers for enhanced photodynamic antibacterial activities

Enhancing the interactions between photosensitizers and bacteria is key to developing effective photodynamic antibacterial agents. However, the influence of different structures on the therapeutic effects has not been systematically investigated. Herein, 4 BODIPYs with distinct functional groups, including the phenylboronic acid (PBA) group and pyridine (Py) cations, were designed to explore their photodynamic antibacterial activities. The BODIPY with the PBA group (IBDPPe-PBA) exhibits potent activity against planktonic Staphylococcus aureus (S. aureus) upon illumination, while the BODIPY with Py cations (IBDPPy-Ph) or both the PBA group and Py cations (IBDPPy-PBA) can significantly minimize the growth of both S. aureus and Escherichia coli (E. coli). In particular, IBDPPy-Ph can not only eliminate the mature S. aureus biofilm and E. coli biofilm in vitro, but also promote the healing of the infected wound. Our work provides an alternative for reasonable design of photodynamic antibacterial materials.

Macrophage Polarization Induced by Bacteria-Responsive Antibiotic-Loaded Nanozymes for Multidrug Resistance-Bacterial Infections Management

Inherited bacterial resistance and biofilm-induced local immune inactivation are important factors in the failure of antibiotics to fight against bacterial infections. Herein, antibiotic-loaded mesoporous nanozymes (HA@MRuO₂ -Cip/GOx) are fabricated for overcoming bacterial resistance, and activating the local immunosuppression in biofilm microenvironment (BME). HA@MRuO₂ -Cip/GOx are prepared by physical adsorption between ciprofloxacin (Cip) or glucose oxidase (GOx) and MRuO₂ NPs, and modified with hyaluronic acid (HA). In vitro, HA@MRuO₂ -Cip/GOx cleaves extracellular DNA (eDNA) to disrupt biofilm, thereby enhancing Cip kill planktonic bacteria. Furthermore, HA@MRuO₂ -Cip/GOx can induce polarization and enhance phagocytosis of a macrophage-derived cell line. More importantly, in vivo therapeutic performance confirms that HA@MRuO₂ -Cip/GOx can trigger macrophage-related immunity, and effectively alleviate MRSA-bacterial lung infections. Accordingly, nanocatalytic therapy combined with targeted delivery of antibiotics could enhance the treatment of bacterial infections.

Micro-structured P-N junction surfaces: large-scale preparation, antifouling properties, and a synergistic antibacterial mechanism

Constructing an antifouling surface cost-effectively is vitally important for many applications. Herein, a series of silicon substrates with micro-pyramid structures and p-n junctions were fabricated following a simple industrial processing flow, among which the p⁺n-Si substrate, fabricated through boron doping of a micro-pyramid structured n-type silicon wafer, exhibited the most pronounced antibacterial performance. Broad-spectrum bactericidal and bacteriostatic activity of p⁺n-Si under ambient light illumination was observed, with an inhibition ability of 73-100% compared to that of a bare glass against both airborne and contact-transmitted bacteria in the intensive care unit. The synergetic effect of mechanical rupture and electric injury was supposed to be responsible for the potent antibacterial activity. This work proposes a state-of-the-art concept that p-n junctions enhance the anti-infection ability of micro-structured surfaces and provide a promising strategy for fabricating practical antifouling surfaces with a large-size, a facile manufacturing procedure, and gentle working conditions, as well as broad-spectrum and physical antibacterial mechanisms.

Ru(II) Complexes with Enaminone Structures for Rapid Sterilization of Staphylococcus aureus and MRSA with Little Accumulation of Drug Resistance

Drug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), pose a serious threat to human life. Therefore, there is urgent need to develop antibiotics with new chemical structures and antibacterial mechanisms, especially those that elicit little drug resistance after long-term use. Herein we synthesized three novel ruthenium complexes (Ru1-Ru3) containing the enaminone structures for the first time. At a concentration of 5 μM, Ru1-Ru3 can lead to a CFU reduction of about 5 log units towards S. aureus and MRSA. Interestingly, Ru3 displayed rapid bactericidal effects and could decrease the CFU numbers of both pathogens by 5 log units within 40 min. The control compounds (Ru4 and Ru5) without the enaminone structures displayed very poor antibacterial activity under the same conditions. Moreover, S. aureus did not show apparent drug resistance towards Ru3 after 20 passages incubation with a sublethal concentration. These results highlight the critical role of enaminone structures for antibacterial applications.

Recent progress and applications of poly(beta amino esters)-based biomaterials

Poly(beta-amino esters, PBAEs) are a promising class of cationic polymers synthesized from diacrylates and amines via Michael addition. Recently, PBAEs have been widely developed for drug delivery, immunotherapy, gene therapy, antibacterial, tissue engineering and other applications due to their convenient synthesis, good bio-compatibility and degradation properties. Herein, we mainly summarize the recent progress in the PBAEs synthesis and their applications. The amine groups of PBAEs could be protonated in low pH environment, exhibiting proton sponge and pH-sensitive abilities. Furthermore, the positive PBAEs can interact with negative genes via electrostatic interactions for efficient delivery of nucleic acids. Moreover, positive PBAEs could also directly kill bacteria by disrupting their membranes at high doses. Finally, PBAEs can augment the immune responses, and improve the bioactivity of hydrogels in tissue engineering.

Targeted Drug Delivery Systems for Eliminating Intracellular Bacteria

The intracellular survival of pathogenic bacteria requires a range of survival strategies and virulence factors. These infections are a significant clinical challenge, wherein treatment frequently fails because of poor antibiotic penetration, stability, and retention in host cells. Drug delivery systems (DDSs) are promising tools to overcome these shortcomings and enhance the efficacy of antibiotic therapy. In this review, the classification and the mechanisms of intracellular bacterial persistence are elaborated. Furthermore, the systematic design strategies applied to DDSs to eliminate intracellular bacteria are also described, and the strategies used for internalization, intracellular activation, bacterial targeting, and immune enhancement are highlighted. Finally, this overview provides guidance for constructing functionalized DDSs to effectively eliminate intracellular bacteria.

Research progress of stimulus-responsive antibacterial materials for bone infection

Infection is one of the most serious complications harmful to human health, which brings a huge burden to human health. Bone infection is one of the most common and serious complications of fracture and orthopaedic surgery. Antibacterial treatment is the premise of bone defect healing. Among all the antibacterial strategies, irritant antibacterial materials have unique advantages and the ability of targeted therapy. In this review, we focus on the research progress of irritating materials, the development of antibacterial materials and their advantages and disadvantages potential applications in bone infection.

Intracellular infection-responsive release of NO and peptides for synergistic bacterial eradication

Bacteria have the ability to invade and survive in host cells to form intracellular bacteria (ICBs), and challenges remain in the intracellular delivery of sufficient antibiotics to remove ICBs. Herein, antimicrobial peptide of epsilon-poly-l-lysine (ePL) and nitric oxide (NO) donors are integrated into nanoparticles (NPs) for ICB treatment without using any antibiotics. ePL was grafted with dodecyl alcohol through ethyl dichlorophosphate to prepare ePL-C₁₂, followed by conjugation of nitrate-functionalized NO donors to obtain ePL-C₁₂NO. PNO/C NPs were prepared from mixtures of ePL-C₁₂NO and ePL-C₁₂ and the optimal ePL-C₁₂NO ratio was 7% in terms of bactericidal effect and macrophage toxicity. Once being engulfed by bacteria-infected macrophages (BIMs), NPs are disintegrated when encountering with ICB-secreted phosphatase, and the NP degradation accelerates intracellular NO release in response to the elevated glutathione levels in BIMs. The selective and abrupt release of NO and ePL with different antimicrobial mechanisms exhibits synergistic eradication of ICBs and no apparent toxicity to macrophages. ICB-infected mice show persistent weight loss and 100% of mortality rate after treatment with ePL-C₁₂ NPs for 7 days, while PNO/C treatment causes entire survival of infected mice and full recovery of body weights to normal values. ICB-infected mice are also accompanied with apparent hepatomegaly and splenomegaly, which are only eliminated by PNO/C treatment without associated any pathological abnormality. PNO/C treatment reduces bacterial burdens in livers (2.45 log), spleens (2.16 log) and kidneys (3.46 log) and restores hepatic and renal function to normal levels. Thus, this study provides a feasible strategy to selectively release NO and cationic peptides in response to intracellular infection-derived signals, achieving synergistic eradication of ICBs and function restoration of the main tissues.

Dual-Cascade Responsive Nanoparticles Enhance Pancreatic Cancer Therapy by Eliminating Tumor-Resident Intracellular Bacteria

The limited drug penetration and robust bacteria-mediated drug inactivation in pancreatic cancer result in the failure of chemotherapy. To fight against these issues, a dual-cascade responsive nanoparticle (sNP@G/IR) that can sequentially trigger deep penetration, killing of intratumor bacteria, and controlled release of chemo-drug, is reported. sNP@G/IR consists of a hyaluronic acid (HA) shell and glutathione (GSH)-responsive polymer-core (NP@G/IR), that encapsulates gemcitabine (Gem) and photothermal agent (IR1048). The polymer core, as an antibiotic alternative, is tailored to exert optimal antibacterial activity and selectivity. sNP@G/IR actively homes in on the tumor due to the CD44 targeting of the HA shell, which is subsequently degraded by the hyaluronidase in the extracellular matrix. The resultant NP@G/IR in decreased size and reversed charge facilitates deep tumor penetration. After cellular endocytosis, the exposed guanidine on NP@G/IR kills intracellular bacteria through disrupting cell membranes. Intracellular GSH further triggers the controlled release of the cargo. Thus, the protected Gem eventually induces cell apoptosis. Under laser irradiation, the hyperthermia of IR1048 helps further elimination of tumors and bacteria. Moreover, sNP@G/IR activates immune response, thereby reinforcing anticancer capacity. Therefore, this dual-cascade responsive sNP@G/IR eliminates tumor-resident intracellular bacteria and augments drug delivery efficacy, providing a new avenue for improving cancer therapy.

Advancements in antimicrobial nanoscale materials and self-assembling systems

Antimicrobial resistance is directly responsible for more deaths per year than either HIV/AIDS or malaria and is predicted to incur a cumulative societal financial burden of at least $100 trillion between 2014 and 2050. Already heralded as one of the greatest threats to human health, the onset of the coronavirus pandemic has accelerated the prevalence of antimicrobial resistant bacterial infections due to factors including increased global antibiotic/antimicrobial use. Thus an urgent need for novel therapeutics to combat what some have termed the 'silent pandemic' is evident. This review acts as a repository of research and an overview of the novel therapeutic strategies being developed to overcome antimicrobial resistance, with a focus on self-assembling systems and nanoscale materials. The fundamental mechanisms of action, as well as the key advantages and disadvantages of each system are discussed, and attention is drawn to key examples within each field. As a result, this review provides a guide to the further design and development of antimicrobial systems, and outlines the interdisciplinary techniques required to translate this fundamental research towards the clinic.

In Situ Surface-Directed Assembly of 2D Metal Nanoplatelets for Drug-Free Treatment of Antibiotic-Resistant Bacteria

The development of antibiotic resistance among bacterial strains is a major global public health concern. To address this, drug-free antibacterial approaches are needed. Copper surfaces have long been known for their antibacterial properties. In this work, a one-step surface modification technique is used to assemble 2D copper chloride nanoplatelets directly onto copper surfaces such as copper tape, transmission electron microscopy (TEM) grids, electrodes, and granules. The nanoplatelets are formed using copper ions from the copper surfaces, enabling their direct assembly onto these surfaces in a one-step process that does not require separate nanoparticle synthesis. The synthesis of the nanoplatelets is confirmed with TEM, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Antibacterial properties of the Cu nanoplatelets are demonstrated in multidrug-resistant (MDR) Escherichia coli, MDR Acinetobacter baumannii, MDR Staphylococcus aureus, E. coli, and Streptococcus mutans. Nanoplatelets lead to a marked improvement in antibacterial properties compared to the copper surfaces alone, affecting bacterial cell morphology, preventing bacterial cell division, reducing their viability, damaging bacterial DNA, and altering protein expression. This work presents a robust method to directly assemble copper nanoplatelets onto any copper surface to imbue it with improved antibacterial properties.