Jung-Wan Kim

One-step synthesis of cellulose/silver nanobiocomposites using a solution plasma process and characterization of their broad spectrum antimicrobial efficacy

Solution plasma process (SPP) is a one-step synthesis technique which expeditiously produces ultra-pure, stable, and uniform nanoparticles in polymer solutions with plasma discharge. Silver nanoparticles (AgNPs) were synthesized in a cellulose matrix as biocomposites by discharging plasma for 180 s at 800 V with a frequency of 30 kHz using a pulsed unipolar power supply into solutions containing cellulose (1–3%) and AgNO3 (1–5 mM). 3D scaffolds of the resulting cellulose/AgNP biocomposites were prepared by lyophilization and cross-linked with UV irradiation. UV-Vis spectroscopy showed a characteristic absorbance maximum in the range of 350–440 nm for the AgNP biocomposites with increase in the intensity of the peaks as the concentration of AgNO3 increased. The peaks exhibited a red shift transition due to the AgNP formation. The nanobiocomposites were pure when examined by FTIR spectroscopy. The 3D scaffolds had a micro-porous structure with pores of (68–74) ± 2 μm in diameter when observed using a FE-SEM instrument equipped with an EDS function. TEM analysis showed that spherical AgNPs in the size range of 5–30 nm were well distributed in the biocomposites of C3Ag3 and C3Ag5. The nanobiocomposites had a broad spectrum of antimicrobial activity against various pathogens with a minimal inhibition concentration of 5.1–20.4 μg ml−1 for bacteria and 81.6–255.0 μg ml−1 for fungi. They killed gram negative bacteria most effectively, but did not affect fungal growth very well, implying their potential as topical antimicrobial agents for the topical treatment of wounds. SPP seems to be the most effective and safest method to synthesize various biocompatible polymer–metal nanoparticle biocomposites.

An evidence of C16 fatty acid methyl esters extracted from microalga for effective antimicrobial and antioxidant property

Fatty acid methyl esters (FAME) derived from lipids of microalgae is known to have wide bio-functional materials including antimicrobials. FAME is an ideal super-curator and superior anti-pathogenic. The present study evaluated the efficiency of FAME extracted from microalgae Scenedesmus intermedius as an antimicrobial agent against Gram positive (Staphylococcus aureus, Streptococcus mutans, and Bacillus cereus) Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and Fungi (Aspergillus parasiticus and Candida albicans). The minimal inhibitory concentration (MIC) for the gram negative bacteria was determined as 12-24 μg mL-1, whereas MIC for gram positive bacteria was 24-48 μg mL-1. MIC for the fungi was as high as 60-192 μg mL-1. The FAME profiles determined by gas chromatography showed 18 methyl esters. Among them, pharmacologically active FAME such as palmitic acid methyl ester (C16:0) was detected at high percentage (23.08%), which accounted for the bioactivity. FAME obtained in this study exhibited a strong antimicrobial activity at the lowest MIC than those of recent reports. This result clearly indicated that FAME of S. intermedius has a strong antimicrobial and antioxidant property and that could be used as an effective resource against microbial diseases.

Solution plasma mediated formation of low molecular weight chitosan and its application as a biomaterial

Low molecular weight (LMW) chitosan has been a great attention in bio-molecular chemistry, medicine, and drug delivery system in particular. Depolymerization of high molecular weight (HMW) chitosan to LMW chitosan was achieved by solution plasma process (SPP) without affecting its chemical structures. Chitosan in solution was depolymerized by discharging plasma at 800 V with 35 kHz for various times (15-120 min). Gel permeation chromatography analysis revealed that molecular weight of chitosan decreased from 3.0 × 105 Da to 7.8 × 103 Da in 30 min plasma treatment, and further to 4.6 × 103 Da in 90 min. Dynamic light scattering and zeta potential studies confirmed formation of chitosan nano-aggregates. Interestingly, the LMW chitosan samples showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans with minimal inhibitory concentration of 80-1200 μg·mL-1. They also exhibited an excellent antioxidant activity (58-75%) and swelling ratio of 0.2-2.0 mg·mg-1. LMW chitosan was likely to have potential for sustainable usage as carrier molecules, biomaterials, and biomedical applications.