BACKGROUND: Implantation of current used bare metal stent, metal drug-eluting stent, or alloy stent would result in local intimal hyperplasia, thrombosis and increase incidence of adverse cardiovascular event. Therefore, the development and preparation of high molecular polymer biodegradable stent has aroused increasing attention.
OBJECTIVE: To study the behavior and histocompatibility of novel fully biodegradable material of poly trimethylene carbonate-co-d, l-lactide (PDLLA/TMC) in vivo.
METHODS: The early-stage synthetized materials of PDLLA/TMC (50/50) were used in the experiment group and the PLLA/TMC (50/50) and PLLA in the control. The patches of each kind of the three polymers above were implanted into the subcutaneous tissue of the 144 Wistar mouse with equal gender, six months old. The polymers patches and their surrounding tissues were taken out and weighed and sliced for hematoxylin-esoin staining at the phases of different test time. Their biodegradable behaviors in vivo were tested by the methods of size exclusion chromatography (SEC), gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and environmental scanning electron microscope (ESEM), and their histocompatibility was evaluated by inflammation cells counting in quantity with light microscope.
RESULTS AND CONCLUSION: In the first 60 days of implantation, there was no significant difference in the percentage of mass loss among the three groups, and their velocity of degradation was relatively slow, though it was slightly faster in the PDLLA/TMC than in the PLLA/TMC and PLLA. During the 60 days to 180 days, PDLA/TMC degradation velocity accelerated obviously, and its percentage of mass loss was much higher than the other two polymers. At 180 days, most of the PDLLA/TMC degraded while the PLLA/TMC and PLLA degraded less. When the three polymers were implanted into the mouse body, at first their molecular declined rapidly, then the decline went into a slow stage gradually. With the time extended, their smooth and orderly superficial structure transformed into ruffle, twist, turbulent, full of hole and hollow, which was rather obvious in the polymer of PDLLA/TMC. Also, there were relative lower inflammation cells counting in the PDLLA/TMC and PLLA/TMC group at the phase of different test time, compared to the PLLA group the differences had statistic significance (P < 0.05), but there was no statistic significance between the PDLLA/TMC and PLLA/TMC group (P > 0.05). The polymer of PDLLA/TMC, which has favorable degradation performance and histocopatibility, is a novel fully biodegradable material and capable of manufacturing the implanted cardiovascular stent.