A General Synthetic Strategy toward the Truxillate Natural Products via Solid-State Photocycloadditions.

The truxillates constitute a large class of dimeric natural products featuring a central, highly substituted cyclobutane core. In principle, these structures could be efficiently synthesized via [2 + 2] photocycloaddition. However, the difficulty in controlling the high-energy electronically excited reactive intermediates in the solution state can lead to poor regio- and diastereocontrol. This has limited the use of photocycloaddition methodology toward the synthesis of this important class of natural products. Herein, we demonstrate that acid-controlled precipitation of C-acyl imidazoles promotes a highly selective solid-state photocycloaddition, and the products of this reaction can be quickly transformed into truxillate natural products.

Macrofungal Mediated Biosynthesis of Silver Nanoparticles and Evaluation of Its Antibacterial and Wound-Healing Efficacy.

Recently, the utilization of biological agents in the green synthesis of nanoparticles has been given interest. In this study, silver nanoparticles were synthesized from an aqueous extract of macrofungus (mushroom), namely Phellinus adamantinus, in a dark room using 20 µL of silver nitrate. Biosynthesized silver nanoparticles were confirmed by analyzing them using a UV-Vis (ultraviolet-visible) spectrophotometer. The synthesized silver nanoparticles were optimized at different pH and temperatures with various dosages of AgNO3 (silver nitrate) and fungal extracts. The synthesized AgNPs (silver nanoparticles) were characterized using TEM (transmission electron microscopy) and EDX (energy-dispersive X-ray) analyses, which confirmed the presence of silver nanoparticles. The size of the nanosilver particles was found to be 50 nm with higher stability. The mycosynthesized AgNPs showed effective antibacterial activity against strains of Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (E. coli and Pseudomonas aeruginosa) bacteria. The minimum inhibitory concentration (MIC) was found to be 3.125 µg/mL by MIC assay. The MTT assay (3-[4,5-dimethylthiazol-2-yl] 2,5-diphenyl-2H-tetrazolium bromide) was performed to study cytotoxicity, and reduced cell viability was recorded at 100 µg/mL. Silver-Polygalacturonic acid-Polyvinyl alcohol ((Ag-PGA)-PVA) nanofiber was prepared using the electrospinning method. The in vitro wound scratch assay was demonstrated to study the wound-healing efficacy of the prepared nanofiber. The wound-healing efficacy of the AgNP-incorporated nanofiber was found to be 20% after 24 h. This study will lay a platform to establish a unique route to the development of a novel nanobiomaterial and its application in antibacterial and wound-healing therapy.

pH-Responsive Cellulose/Silk/Fe3O4 Hydrogel Microbeads Designed for Biomedical Applications.

In this study, cellulose/Fe3O4 hydrogel microbeads were prepared through the sol-gel transition of a solvent-in-oil emulsion using various cellulose-dissolving solvents and soybean oil without surfactants. Particularly, 40% tetrabutylammonium hydroxide (TBAH) and 40% tetrabutylphosphonium hydroxide (TBPH) dissolved cellulose at room temperature and effectively dispersed Fe3O4, forming cellulose/Fe3O4 microbeads with an average diameter of ~15 µm. Additionally, these solvents co-dissolved cellulose and silk, allowing for the manufacture of cellulose/silk/Fe3O4 hydrogel microbeads with altered surface characteristics. Owing to the negatively charged surface characteristics, the adsorption capacity of the cellulose/silk/Fe3O4 microbeads for the cationic dye crystal violet was >10 times higher than that of the cellulose/Fe3O4 microbeads. When prepared with TBAH, the initial adsorption rate of bovine serum albumin (BSA) on the cellulose/silk/Fe3O4 microbeads was 18.1 times higher than that on the cellulose/Fe3O4 microbeads. When preparing TBPH, the equilibrium adsorption capacity of the cellulose/silk/Fe3O4 microbeads for BSA (1.6 g/g) was 8.5 times higher than that of the cellulose/Fe3O4 microbeads. The pH-dependent BSA release from the cellulose/silk/Fe3O4 microbeads prepared with TBPH revealed 6.1-fold slower initial desorption rates and 5.2-fold lower desorption amounts at pH 2.2 than those at pH 7.4. Cytotoxicity tests on the cellulose and cellulose/silk composites regenerated with TBAH and TBPH yielded nontoxic results. Therefore, cellulose/silk/Fe3O4 microbeads are considered suitable pH-responsive supports for orally administered protein pharmaceuticals.