Dual Drug Loaded pH-sensitive Micelles for Efficient Bacterial Infection Treatment

Bimetal-organic framework/GOx-based hydrogel dressings with antibacterial and inflammatory modulation for wound healing

Antibiotic resistance of bacteria and persistent inflammation are critical challenges in treating bacteria infected wounds. Thus, it is urgent to develop versatile wound dressings that possess high-efficiency antibacterial performance and inflammation regulation. Herein, we have successfully constructed a hydrogel wound dressing consisting of the bimetallic metal-organic framework (MOF) loaded with glucose oxidase (GOx), termed as MOF(Fe-Cu)/GOx-polyacrylamide (PAM) gel. Hydrogel dressings can provide an efficient cascade-catalyzed system to accelerate wound healing via synergistic antibacterial and inflammatory modulation. Importantly, the catalytic property of the bimetallic MOF(Fe-Cu) is about five times that of the monometallic MOF(Fe). Based on such a cascade-catalyzed system, the abundant gluconic acid and H₂O₂ can be continuously produced by decomposing glucose via GOx. Such gluconic acid can notably improve the peroxidase performance of MOF(Fe-Cu), which can further efficiently decompose H₂O₂ to achieve the antibacterial. Meanwhile, MOF (Fe Cu)/GOx PAM gel can induce macrophages to change into an M2 phenotype, which can accelerate the transformation of the wound microenvironment to a remodeling state and then accelerate angiogenesis and neurogenesis. This work provides multifunctional bioactive materials for accelerating wound healing and will have great potential in clinical applications. STATEMENT OF SIGNIFICANCE: Antibiotic resistance and persistent inflammation are still the critical reasons for the slow healing of bacteria infected wounds. Herein, we prepared a hydrogel wound dressing composed of bimetallic metal organic framework (MOF) loaded with glucose oxidase (GOx). The catalytic activity of the bimetallic MOF(Fe-Cu) is significantly enhanced due to doping of copper, which makes it possess outstanding antibacterial ability based on cascade catalysis. Such dressing can promote the remodeling of inflammatory immunity by regulating macrophage polarization to suppress over-reactive inflammation, further accelerating the healing of bacteria-infected wounds. This study provides an innovative and effective way to accelerate the healing of bacteria infected wound by combining bacteria killing and inflammation modulation.

Progress and prospects of nanomaterials against resistant bacteria

Drug-resistant bacterial infections are increasingly heightening, which lead to more severe illness, higher cost of treatment and increased risk of death. Nanomaterials-based therapy, an "outrider", serving as a kind of innovative antimicrobial therapeutics, showing promise in replacing antimicrobial agents and enhancing the activity of antibiotics, generally bases on the various inorganic and/or organic materials. When the size of those materials is below to a certain nano-level and the content of nanomaterials is above a certain amount, they are lethal to the resistant bacteria, which bypass the traditional bacterial resistance mechanisms. This review highlights the effect of nanomaterials in combating extracellular/intracellular bacteria and eradicating biofilms. Based on the studies searched on the Web of Science through relevant keywords, this review article starts with analyzing the current situation, resistance mechanisms, and treatment difficulties of bacteria resistance. Then, the efficacy of nanomaterials against resistant bacteria and their mechanisms (e.g., physical impairment, biofilm lysis, regulating bacterial metabolism, protein and DNA replication as well as enhancing the antibiotics concentration in infected cells) are collected. Lastly, the factors affecting the antibacterial efficacy are argued from the side of nanomatrials and bacterium, which followed by the emerging challenges and recent perspectives of achieving higher targeting released nanomaterials as antibacterial therapeutics.

pH-responsive silica nanoparticles for the treatment of skin wound infections

Chronic wounds are not only a burden for patients but also challenging for clinic treatment due to biofilm formation. Here, we utilized the phenomenon that chronic wounds possess an elevated local pH of 8.9 and developed pH-sensitive silica nanoparticles (SiNPs) to achieve a targeted drug release on alkaline wounds and optimized drug utility. Chlorhexidine (CHX), a disinfectant and antiseptic, was loaded into SiNPs as the model drug. The loaded CHX displayed a release 4 - 5 fold higher at pH 8.0 and 8.5 than at pH 6.5, 7.0 and 7.4. CHX-SiNPs furthermore exhibited a distinctive antibacterial activity at pH 8.0 and 8.5 against both Gram-negative and -positive bacterial pathogens, while no cytotoxicity was found according to cell viability analysis. The CHX-SiNPs were further formulated into alginate hydrogels to allow ease of use. The antibacterial efficacy of CHX-SiNPs was then studied with artificial wounds on ex vivo human skin. Treatment with CHX-SiNPs enabled nearly a 4-lg reduction of the viable bacterial cells, and the alginate formulated CHX-SiNPs led to almost a 3-lg reduction compared to the negative controls. The obtained results demonstrated that CHX-SiNPs are capable of efficient pH-triggered drug release, leading to high antibacterial efficacy. Moreover, CHX-SiNPs enlighten clinic potential towards the treatment of chronic wound infections. STATEMENT OF SIGNIFICANCE: A platform for controlled drug release at a relatively high pH value i.e., over 8, was established by tuning the physical structures of silica nanoparticles (SiNPs). Incorporation of chlorhexidine, an antimicrobial agent, into the fabricated SiNPs allowed a distinctive inhibition of bacterial growth at alkaline pHs, but not at acidic pHs. The efficacy of the SiNPs loaded with chlorhexidine in treating wound infections was further validated by utilizing ex vivo human skin samples. The presented work demonstrates clinic potential of employing alkaline pH as a non-invasive stimulus to achieve on-demand delivery of antimicrobials through SiNPs, showcasing a valuable approach to treating bacterial infections on chronic wounds.