Enzyme-Responsive Ag Nanoparticle Assemblies in Targeting Antibacterial against Methicillin-Resistant Staphylococcus Aureus.

The abuse of antibiotics resulted in the emergence of antibiotics-resistant bacteria, which has raised a great social concern together with the impetus to develop effective antibacterial materials. Herein, the synthesis of biocompatible enzyme-responsive Ag nanoparticle assemblies (ANAs) and their application in the high-efficiency targeted antimicrobial treatment of methicillin-resistant Staphylococcus aureus (MRSA) have been demonstrated. The ANAs could collapse and undergo stable/collapsed transition on approaching MRSA because of the serine protease-like B enzyme proteins (SplB)-triggered decomposition of the branched copolymers which have been employed as the macrotemplate in the synthesis of responsive ANAs. This transition contributed greatly to the high targeting affinity and efficiency of ANAs to MRSA. The minimum inhibitory concentration and minimum bactericidal concentration against MRSA were 2.0 and 32.0 µg mL-1, respectively. Skin wound healing experiments confirmed that the responsive ANAs could serve as an effective wound dressing to accelerate the healing of MRSA infection.

Activatable Cell-Penetrating Peptide Conjugated Polymeric Nanoparticles with Gd-Chelation and Aggregation-Induced Emission for Bimodal MR and Fluorescence Imaging of Tumors.

Activatable cell-penetrating peptide (ACPP) conjugated polymeric nanoparticles containing gadolinium (Gd)-chelates and aggregation-induced emission fluorogens (AIEgens) have been synthesized and applied as a magnetic resonance imaging (MRI) and fluorescence imaging (FI) bimodal imaging probe with active tumor targeting. The polymeric nanoparticles have been generated by dissolving presynthesized linear block copolymers into water directly. With AIEgens, N-BP5-Gd-ACPPs showed tumor cell penetration, which can be characterized by in vitro FI. Preliminary in vivo experiments of Gd-chelated nanoparticles have demonstrated promising characteristics as a tumor-targeting MRI contrast agent with good biocompatibility. This study impacts the synthesis of functional copolymers and polymeric nanoparticles for their applications in bioimaging.

Thermoresponsive in Situ Forming Hydrogel with Sol-Gel Irreversibility for Effective Methicillin-Resistant Staphylococcus aureus Infected Wound Healing.

An in situ forming hydrogel has emerged as a promising wound dressing recently. As physically cross-linked hydrogels are normally unstable, most in situ forming hydrogels are chemically cross-linked. However, big concerns have remained regarding the slow gelation and the potential toxicity of residual functional groups from cross-linkers or the polymer matrix. Herein, we report a sprayable in situ forming hydrogel composed of poly(N-isopropylacrylamide166-co-n-butyl acrylate9)-poly(ethylene glycol)-poly(N-isopropylacrylamide166-co-n-butyl acrylate9) copolymer (P(NIPAM166-co-nBA9)-PEG-P(NIPAM166-co-nBA9), denoted as PEP) and silver-nanoparticles-decorated reduced graphene oxide nanosheets (Ag@rGO, denoted as AG) in response to skin temperature. This thermoresponsive hydrogel exhibits intriguing sol-gel irreversibility at low temperatures for the stable dressing of a wound, which is attributed to the inorganic/polymeric dual network and abundant coordination interactions between Ag@rGO nanosheets and PNIPAM. The biocompatibility and antibacterial ability against methicillin-resistant Staphylococcus aureus (MRSA) of this PEP-AG hydrogel wound dressing are confirmed in vitro and in vivo, which could transparently promote the healing of a MRSA-infected skin defect.