Piyachat Chuysinuan

Preparation and Characterization of Caffeic Acid-Grafted Electrospun Poly(l-Lactic Acid) Fiber Mats for Biomedical Applications

Caffeic acid (CA) was chemically immobilized onto the surfaces of the individual electrospun poly(l-lactic acid) (PLLA) fibers to enhance the hydrophilicity and impart the antioxidant activity to the obtained fibrous membranes. This was done in two sequential steps. First, amino groups were covalently introduced onto the surfaces through the reaction with 1,6-hexamethylenediamine (HMD). In the second step, the amino moieties reacted with CA, which had been preactivated sequentially with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The success of the reactions was confirmed by the ninhydrin assay and X-ray photoelectron spectroscopic analysis (XPS). Indirect cytotoxicity evaluation with murine dermal fibroblasts (L929) and human dermal fibroblasts (HDFa) revealed that the neat and the modified PLLA fibrous matrices released no substances in the levels that were harmful to the cells. Direct culturing of HDFa on these fibrous substrates indicated that they supported the proliferation of the cells on days 2 and 3 very well and that the CA-immobilized substrates exhibited the highest cell viability. Lastly, the antioxidant activity of the CA-immobilized substrates, as revealed by the 1,1-diphenyl-2-picryldrazyl (DPPH) radical scavenging assay, was as high as 88% on average.

Development of a gallic acid-loaded chitosan and polyvinyl alcohol hydrogel composite: Release characteristics and antioxidant activity

The physico-chemical properties of a chitosan and polyvinyl alcohol (CS/PVA)-based hydrogel composite were investigated. Tetraethyl orthosilicate (TEOS) was employed as a crosslinking agent. The results indicated that the chitosan-based composite presented a thermal resistance up to 200°C. The structural properties, which were evaluated using FTIR and DSC, showed good miscibility between chitosan and polyvinyl alcohol. SEM presented a compact and homogeneous structure. The release profile of the chitosan-based hydrogel composite was investigated using gallic acid (GA). It showed high antioxidant activities, which were monitored using DPPH radical scavenging. Diffusion of water into the chitosan-based hydrogel was assumed to be pseudo-Fickian in PBS solution. The CS/PVA-based hydrogel composite exhibited good properties as a drug delivery system.

Characterization of essential oil from Ocimum gratissimum leaves: Antibacterial and mode of action against selected gastroenteritis pathogens

Essential oil of fresh leaves of Ocimum gratissimum (OGEO) was water-steam distilled and analyzed by GC-MS. Thirty-seven compounds were identified, with eugenol (55.6%) as the major component followed by cis-ocimene (13.9%), γ-muurolene (11.6%), (Z,E)-α-farnesene (5.6%), α-trans-bergamotene (4.1%), and β-caryophyllene (2.7%). Antimicrobial activity of OGEO was tested against four gastroenteritis pathogens (Staphylococcus aureus, Escherichia coli, Salmonella Typhimurium, and Shigella flexneri). OGEO exhibited antibacterial effect, with MICs of 1-2 mg ml-1, against the tested species. OGEO also displayed rapid killing effect within 5 s at four times of MIC against both E. coli and S. Typhimurium. Various assays were performed to investigate the mode of action of the oil. OGEO increased the permeability of microbial cell membrane as evidenced by LIVE/DEAD BacLight assay. Analyses of the release of absorbing materials at 260 nm, protein leakage, SDS-PAGE, and SEM strongly suggested the disruptive action of the oil on the cytoplasmic membrane of the tested microorganisms. Results revealed that the antibacterial property of OGEO could be due to membrane disruption.

Physico-Chemical and In Vitro Cytotoxic Properties of Alginate/Soy Protein Isolated Scaffolds for Tissue Engineering

Three-dimensional (3D) porous alginate/soy protein isolated (Alg/SPI) tissue engineering scaffolds were achieved by freeze-drying. The physico-chemical attributes of the scaffolds including morphology, chemical structure, mechanical properties and in vitro cytotoxicity were investigated for different SPI blends. Results indicated that increasing SPI content to 40 wt% in the blends resulted in the partial existence of closed pores and reduced pore size. The mechanical values of the scaffolds under compression also reduced with increasing SPI in the blends. The addition of SPI did not significantly enhance the cell viability of the scaffolds investigated for in vitro culture with human fibroblasts, which remained in the high (90 – 100%) range. Results demonstrated that Alg/SPI scaffolds have potential for use as tissue engineering scaffolds.

Poly(Lactic Acid) (PLA) Electrospun Fibers Containing Rice Extract: Release Characteristics and their Antioxidant Activity

This study aimed to fabricate electrospun poly(lactic acid) (PLA) fiber mats containing 3 kinds of rice extract (rice bran, riceberry and LeumPhum rice extracts) by using electrospinning. The rice extract has been reported to exhibit antioxidant activities. The neat and rice extract-loaded PLA fiber mats were smooth and no beads formed on the fiber surface with diameters ranging from 450-656 nm. Release characteristics of the rice extract-loaded electrospun PLA fiber mats were investigated using total immersion methods. The scavenging ability of LeumPhum rice extract-loaded electrospun fibers showed superior scavenging activity as determined using the DPPH radical scavenging method. The results suggested that rice extract incorporated in PLA nanofibers had no negative effect on antioxidant activity when using an electrospinning process.