Byung Wook Jo

Polymer prodrug approaches applied to paclitaxel

Paclitaxel possesses a unique mechanism of drug action as a new class of microtubule stabilizing agent which finally leads to disrupted mitosis and cell death. Recent findings have shown that paclitaxel initiates apoptosis through multiple mechanisms. However, the strong hydrophobicity of paclitaxel drastically limits its use in natural form. In addition, significant toxicity which is mainly ascribed to the non-specific, indiscriminate distribution among the tissues limited the application of paclitaxel in cancer therapy. Therefore, it remains of interest to improve their use by enhancing solubility, selectivity and in vivo delivery by preparing functional prodrugs selectively activable in tumour areas. This article summarizes results and information derived recently from paclitaxel prodrugs based mainly on macromolecular conjugates and their interactions with body fluids. We also explore the potential application of site-specific carriers in the development of tumor-targeting paclitaxel conjugates.

Degradation of fucoidans from Sargassum fulvellum and their biological activities.

A fucoidan extracted from Sargassum fulvellum, was degraded by ultrasound (US) or electron beam (EB) irradiation in the presence of hydrogen peroxide aqueous solution. From the energetic point of view, the most effective method for the fucoidan degradation was found to be EB radiation method in H2O2 with a yield of scission Gs 3.310 × 10(-8)mol/J at the reaction condition of 1.5% hydrogen peroxide and irradiation 2.5 kGy. The degradation took place by the formation of a reactive hydroxyl radical due to the dissociation of H2O2 in the presence of US or EB. The low molecular weight fucoidans (LMWFs) prevented P-selectin binding to Sialyl Lewis X with an IC50 (inhibitory concentration 50) of 20 nM as compared to 400 nM for heparin and 25,000 nM for dextran sulfate. The LMWFs showed no hemolytic activity at concentrations up to 950 μg/ml.

DNA-Templated Preparation of Gold Nanoparticles

DNA-mediated gold nanoparticles were prepared by chemical reduction of DNA-Au(III) complex. The DNA-Au(III) was first formed by reacting DNA with HAuCl4 at a pH of 5.6. The complex in solution was reacted with hydrazine reducing Au(III) to Au. The reduced Au formed nanodimensional aggregates. The particle distributions were obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). This method resulted in a rather uniform dispersion of Au nanoparticles of near-spherical shape and 45~80 nm in diameter. Gold nanoparticles were embedded and stabilized by DNA.

Transesterification and compatibilization in the blends of bisphenol-A polycarbonate and poly(trimethylene terephthalate)

Melt blending of Bisphenol A polycarbonate(PC) and poly(trimethylene terephthalate)(PTT) was carried out over the entire composition range. The mixing time was varied up to 90 min. The resulting samples were analyzed by FT-IR, DSC, XRD, DMTA,1H NMR, and SEM. The process of transesterification between the two polymers and their resulting compatibilization were observed. The behaviors of the PTT-rich and PC-rich blends were different and an equilibrium was found to exist. Peculiar behavior, which was different from that of the PTT-rich and PC-rich blends, was exhibited by the 50/50(PTT/PC) blend.