Exposure to microwave irradiation at constant culture temperature slows the growth of Escherichia coli DE3 cells, leading to modified proteomic profiles.

Despite a few decades of research, interest continues in understanding the potential influences of low energy microwave irradiation on biological systems. In the present study, growth of E. coli DE3 in LB media slowed in the presence of microwave irradiation (max. 10 W) while the temperature of cultures was maintained at 37 °C. Viable cell counts in microwave-irradiated cultures were also significantly lower. When microwave irradiation was ceased, E. coli growth was restored. A top-down proteomic analysis of total proteins isolated from control and microwave-irradiated E. coli cultures revealed differential abundance of 10 resolved protein spots, with multiple proteins identified in each following mass spectrometric analysis. Among these proteins, a number are involved in metabolism, suggesting alterations to metabolic activities following microwave irradiation. Furthermore, four amino acid-tRNA ligases were also identified, pointing to the possibility of stress responses in E. coli under microwave irradiation.

Abrasive treatment of microtiter plates improves the reproducibility of bacterial biofilm assays.

Microtiter plate-based bacterial biofilm assay is frequently used to study bacterial biofilm development and growth. While this assay is simple and relatively high-throughput, it frequently shows difficulty in establishing robust biofilm attachment in the wells. We report that the consistency of bacterial biofilm assays carried out in microtiter plates subjected to abrasive treatment, by sandblasting or drill press grinding, is significantly improved in a Pseudomonas fluorescens Pf0-1 model. Scanning electron microscopy imaging suggests that the treated surfaces could provide points of attachment to facilitate the recruitment of bacteria in the initial phase of biofilm colony establishment. The sandblast treated polypropylene, but not polystyrene, plates were found suitable in studying the impact of flavonoid quercetin on the biofilm formation in Bacillus subtilis FB17. Further investigation revealed that due to the hydrophobicity of the polystyrene surfaces, a greater amount of quercetin was adsorbed on the plate surface, effectively lowering the concentration of the flavonoid in solution.

Microwave-assisted delivery of an anticancer drug to cancer cells.

Exposure of MCF-7 breast and PC-3 prostate cancer cells to 10 W microwaves at 2.45 GHz increased their uptake of the cancer drug doxorubicin from media by almost 100%, concomitantly increasing cell death, while microwave exposure alone had no cellular toxicity. Addition of inhibitors of endocytosis during the treatment of MCF-7 cells with doxorubicin and microwaves showed no impact on the uptake of the anticancer drug. Furthermore, the uptake of oligonucleotides by MCF-7 cells is not affected by the treatment with microwaves. These observations suggest that endocytosis is not involved in the uptake of doxorubicin while cells are exposed to microwave irradiation. Thus, targeted low power microwave irradiation could be a safe and effective means of promoting chemotoxin delivery to cancer cells, potentially reducing the dosages and side effects of anti-cancer drugs.

Microwave-assisted syntheses of BODIPY-sugar conjugates through click chemistry and conjugate assembly into liposomes.

BODIPY fluorophores bearing azide or terminal alkyne functions were conjugated with glycans modified with terminal alkyne or azido through the Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) chemistry under microwave heating while these reactions did not proceed when heated in an oil-bath. The BODIPY-glycan conjugate product 8a undergoes self-assembly into liposomes when hydrated. Formation of liposomes was confirmed by both bright field and confocal microscopy. Fluorescent emission within the liposome was shifted from green to red due to effective high concentrations.