Man Ken Cheung

In vitro cytotoxicity, hemolysis assay, and biodegradation behavior of biodegradable poly(3‐hydroxybutyrate)–poly(ethylene glycol)–poly(3‐hydroxybutyrate) nanoparticles as potential drug carriers

Nanoparticles based on amorphous poly(3-hydroxybutyrate)-poly(ethylene glycol)-poly(3-hydroxybutyrate) (PHB-PEG-PHB) are potential drug delivery vehicles, and so their cytotoxicity and hemolysis assay were investigated in vitro using two kinds of animal cells. The PHB-PEG-PHB nanoparticles showed excellent biocompatibility and had no cytotoxicity on animal cells, even when the concentrations of the PHB-PEG-PHB nanoparticle dispersions were increased to 120 microg/mL. Moreover, no hemolysis was detected with the PHB-PEG-PHB nanoparticles, suggesting that the PHB-PEG-PHB nanoparticles were obviously much hemocompatible for drug delivery applications. In the presence of intracellular enzyme esterase, the biocompatible PHB-PEG-PHB nanoparticles might be hydrolyzed, and their biodegradable behavior was monitored by the fluorescence spectrum and the pH meter. The initial biodegradation rate of the PHB-PEG-PHB nanoparticles was closely related to the enzymatic amount and the PHB block length. Compared with that obtained from the fluorescence determination, the initial biodegradation rate from pH measurement was faster. The biodegraded products mainly consisted of 3HB monomer and dimer, which were the metabolites present in the body.

Investigation of the effects of the types of food waste utilized as carbon source on the molecular weight distributions and thermal properties of polyhydroxybutyrate produced by two strains of microorganisms

Abstract The average molecular weight and molecular weight distribution of polyhydroxybutyrate can be affected by different bacterial strains, different cultivation time and also different carbon sources. Food waste was proven to have a high potential in the induction of biosynthesis of polyhydroxybutyrate with different production yields and physical properties. A specific culture of Alcaligenes latus DSM 1124 and Staphylococcus epidermidis, which was isolated from sesame oil, were selected to ferment several types of food wastes as nutrients, including malt waste, soy waste, confectionery waste, milk waste, vinegar waste and sesame oil, into polyhydroxybutyrate in this study. Average molecular weight and molecular weight distribution of polyhydroxybutyrate were measured by gel permeation chromatography. By comparing the results with those obtained using sucrose as a carbon source, the average molecular weight of polyhydroxybutyrate produced from food wastes was increased for Alcaligenes latus; however, it was decreased for S. epidermidis. Thermal analyses of the biopolymer produced by S. epidermidis indicated that the melting point of the polymer produced from sesame oil as carbon source was 188°C, the highest temperature among those polymers produced by using ice cream, malt, and soya wastes.