Papers by Author: Chun Yan Li

Abstract: The method of high performance liquid chromatography (HPLC) is established to determine the content of antibacterial agent — ciprofloxacin (CF) in the degradation solution of ciprofloxacin-polyurethane (CFPU) and investigate the in vitro degradation kinetics by plotting and fitting the cumulative release curves to inspect the effects of different medium and different concentrations on drug release. The results showed that the HPLC method is accurate, reliable and simple. The drug-release of CFPU was bioresponsive and could be accorded with first order kinetics. It was observed that CF was released from CFPU by a combination of diffusion and erosion mechanism, mainly in the manner of diffusion in the absence of infection while erosion mechanism in the presence of infection.

Abstract: A novel photosensitizer, pentalysine β-carbonyl-phthalocyanine zinc [ZnPc-(Lys)₅] has tendency to form aggregate in aqueous solution. The observed in vivo Photodynamic therapy (PDT) effect of ZnPc-(Lys)₅ suggests a disaggregation mechanism. In this study, the equilibrium binding constant K_a, the numbers of binding sites n and the distance of Forster radii r between ZnPc-(Lys)₅ and human serum albumin (HSA) are measured by Spectroscopy. A molecular model of HSA-ZnPc-(Lys)₅ complex was generated according to these datum. This molecular model provides rationale that the molecular interaction between HSA and ZnPc-(Lys)₅ facilitates the dissociation of ZnPc aggregates.

Abstract: Bacterial induced infection is a major complication associated with the use of medical implants. Degradable antibacterial ciprofloxacin-polyurethanes (CFPU) have been synthesized in attempts to address this problem. It is supposed that the material may be sensitively hydrolyzed by inflammatory enzyme, cholesterol esterase (CE), and the drug could be released according to the state of infection. The enzyme biodegradation experiments showed an extra release of ciprofloxacin when CFPU was incubated by enzyme solutions than by phosphate-buffer saline (PBS). Results showed that the drug release was enhanced as the concentration of the enzyme increased. The antimicrobial activities of degradation solutions were tested by broth dilution assay. The enzyme degradation solutions exhibited an ability to kill bacteria. The cell cytotoxicity assay indicated that the degradation products were hypotoxicity to human beings according to the cytotoxicity grade of United States Pharmacopoeia (USP).