Biodegradation and mechanical characteristics of poly(lactic-co-glycolic acid) biliary stents in vitro

Bing HAN; Liang YU; Shan MIAO; Xuemin LIU

ABSTRACT

BACKGROUND:

The biliary stents commonly used in clinic are made of plastics and metal, both of which have some irresolvable defects. New type of material characterizing by great biocompatibility and degradation for the making of biliary stents needs to be found and studied.

OBJECTIVE:

To evaluate the biodegradation law and the change in radical force of five different mole-ratios of biliary stents made of poly (lactic-co-glycolic acid) (PLGA) in human bile in vitro.DESIGN, TIME AND

SETTING:

A Completely random design was performed at the Laboratory of Hepatobiliary Surgery, the First Affiliated Hospital of Medical College, Xi'an Jiaotong University between July and December 2006.MATERIALS Five different mole-ratios of PLGA hiliary stents (90L/10G, 80L/20G, 70L/30G, 60L/40G, and 50L/50G) were provided by Dalgang Biological Science and Technology Co., Ltd., Jinan; Human fresh bile was obtained from the patients who underwent external drainage of bile in the Department of Hepatobiliary Surgery, the First Affiliated Hospital of Medical College, Xi'an Jiaotong University.

METHODS:

Thirty-two PLGA biliary stents of each proportion were respectively divided into eight groups, with four stents in each group. All of them were independently submerged into test tubes with 10 mL fresh human bile which were then placed in constant temperature oscillator. The temperature was set at 37 ℃. The bile was changed every day. After incubated for one week to eight weeks, the PLGA biliary stents were respectively taken out of test tubes from the first to the eighth group each week. They were washed with distilled water and dried in calorstat for 24 hours.MAIN OUTCOME

MEASURES:

① Gross morphology, color and integrality of PLGA stents; ② Scanning electron microscope; ③ the mass and the radical force of PLGA stents.

RESULTS:

① Five different mole-ratios of PLGA stents followed a similar changing law as to gross morphology stents remained intact → stents became soft → the surface ofstents became coarse and cracked → stents collapsed → stents were degraded into pieces → stents were completely degraded. ② Before degradation limpid stereo reticular structure of PLGA; One week after degradation PLGA was corroded and the reticular structure was decreased; Three weeks after degradation airspace was gradually disappeared and the reticular structure was further decreased; Five weeks after degradation airspace and the reticular structure were completely damaged, which was in an indefinite form. ③ The mass loss of each proportion of PLGA stents gradually speeded up along with the time extension. Furthermore, with the content of PGA increasing, the mass loss of the stents became faster. The initial radical force was different among five different mole-ratios of hiliary stents. With the content of PLA increasing, the radical force of the stents became stronger.

CONCLUSION:

The material of PLGA possesses adjustable biodegradation and good mechanical feature, so it is suitable for preparation of biliary stents.