Lee, Do Nam

Abstract Background: The antibiotic resistance of pathogenic microbes due to the overuse of antibiotics is a growing threat to the public health and can eventually reduce the therapeutic effects of antibiotics. Hydrogel-based systems for local delivery of antibiotics can be a solution to this problem. Metal-organic frameworks (MOFs) have received considerable interest for use as antimicrobial materials due to their high porosity, large surface area to volume, diverse structures, and tunable topologies. Methods: In this study, we developed MOF-encapsulated and dual (photo & chemical)-crosslinkable alginate hydrogel as an antimicrobial scaffold. We synthesized antimicrobial Cu(AZPY)-MOF using solvothermal reaction and encapsulated them in an alginate-based hydrogel via visible light photo-crosslinking and calcium ion-induced chemical-crosslinking processes. Results: Powder X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy confirmed the successful fabrication of Cu(AZPY)-MOF encapsulated alginate hydrogel. The mechanical strength of the dual-crosslinked hydrogels was better than that of the photo-crosslinked hydrogel. Encapsulation of Cu(AZPY)-MOF in an alginate hydrogel resulted in a further increase in the mechanical strength of the hydrogel owing to the additional interaction of alginate with Cu-MOF. Moreover, the Cu(AZPY)-MOF encapsulated alginate hydrogel exhibited excellent antibacterial and antifungal properties against two bacterial strains (i.e., MRSA and S. mutans) and one fungal strain (C. albicans) as well as negligible cytotoxicity toward MEFs. Conclusions: The antimicrobial agents encapsulated dual-crosslinkable alginate hydrogel developed in this study is a promising candidate for use in tissue engineering and biomedical field.

Compared to most of nano-sized particles, core–shell-structured nanoflowers have received great attention as bioactive materials because of their high surface area with the flower-like structures. In this study, core–shell-structured Si-based NiO nanoflowers, Si@NiO, were prepared by a modified chemical bath deposition method followed by thermal reduction. The crystal morphology and basic structure of the composites were characterized by powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and porosity analysis (BJT), and inductively coupled plasma optical emission spectrometry (ICP-OES). The electrochemical properties of the Si@NiO nanoflowers were examined through the redox reaction of ascorbic acid with the metal ions present on the surface of the core–shell nanoflowers. This reaction favored the formation of reactive oxygen species. The Si@NiO nanoflowers showed excellent anticancer activity and low cytotoxicity toward the human breast cancer cell line (MCF-7) and mouse embryonic fibroblasts (MEFs), respectively, demonstrating that the anticancer activities of the Si@NiO nanoflowers were primarily derived from the oxidative capacity of the metal ions on the surface, rather than from the released metal ions. Thus, this proves that Si-based NiO nanoflowers can act as a promising candidate for therapeutic applications.

Polyurethane foams (PUFs) have attracted attention as biomaterials because of their low adhesion to the wound area and suitability as biodegradable or bioactive materials. The composition of the building blocks for PUFs can be controlled with additives, which provide excellent anti-drug resistance and biocompatibility. Herein, nanosized Cu-BTC (copper(II)-benzene-1,3,5-tricarboxylate) was incorporated into a PUF via the crosslinking reaction of castor oil and chitosan with toluene-2,4-diisocyanate, to enhance therapeutic efficiency through the modification of the surface of PUF. The physical and thermal properties of the nanosized Cu-BTC-incorporated PUF (PUF@Cu-BTC), e.g., swelling ratio, phase transition, thermal gravity loss, and cell morphology, were compared with those of the control PUF. The bactericidal activities of PUF@Cu-BTC and control PUF were evaluated against Pseudomonas aeruginosa, Klebsiella pneumoniae, and methicillin-resistant Staphylococcus aureus. PUF@Cu-BTC exhibited selective and significant antibacterial activity toward the tested bacteria and lower cytotoxicity for mouse embryonic fibroblasts compared with the control PUF at a dose of 2 mg mL−1. The Cu(II) ions release test showed that PUF@Cu-BTC was stable in phosphate buffered saline (PBS) for 24 h. The selective bactericidal activity and low cytotoxicity of PUF@Cu-BTC ensure it is a candidate for therapeutic applications for the drug delivery, treatment of skin disease, and wound healing.