中国组织工程研究与临床康复 第 13 卷 第 22 期 20090528 出版 Journal of Clinical Rehabilitative Tissue Engineering Research May 28, 2009 Vol.13, No.22 ISSN 1673-8225 CN 21-1539/R CODEN: ZLKHAH 43741 Tianjin Key Laboratory of Biomaterial Research, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences 2Department of Cardiovascular Surgery, TEDA International Cardiovascular Hospital, Tianjin 300457, China L Feng, Doctor, Assistant Researcher, Tianjin Key Laboratory of Biomaterial Research, Institute of Biomedical Engineering, Chinese Academy of Medical Sciences Tianjin High-Tech Research and Development Program, No. 05YFGZSF02900* Received: 2009-01-07 Accepted: 2009-04-16 (20090107002/M) L F, Liu TJ, Zhao J, Liu XC, Song CX.Preparation of intramyocardial bilayered porous biodegradable drug delivery stents. Zhongguo Zuzhi Gongcheng Yanjiu yu Linchuang Kangfu. 2009;13(22): 4374-4376. http:/www.crter.cn http:/en.zglckf.com apparatus (Sotax AT7, OSI, Paris, France) and agitated at a speed of 100 r/min at 37 C for 5 weeks. At specific times, the solution was removed completely and the release study was continued after replacing the solution with the same volume of fresh PBS. One milliliter of the release medium was quantified in terms of amount of released BSA using the Coomassie brilliant blue assay. Each in vitro release study was performed in triplicate. Composition, morphology, and mechanical strength of stents The surface morphology and the section cross structures of stents were investigated through the use of scanning electron microscope (SEM, XL30ESEM, Philips). The radial compression strength of biodegradable drug stent was tested with universal material testing machines (MS00-10KN, Testometric, Britain). Effects of stent on infracted animal heart A standard animal model of chronic myocardial ischemia was used 12. Miniswines, weighing 12 to 15 kg, were anesthetized. At the initial operation, with sterile technique, the heart was exposed through a small left thoracotomy, and the pericardium was opened. Following successful induction of chronic myocardial ischemia, animals were randomly assigned into a blank control and a stent group (n = 6 for each group). The proximal left circumflex artery was dissected free, and a super drill set (CT-800, Wah Luen Electronic Tools Co., Ltd., China) with an internal diameter of 3 mm was placed in the same location for each animal, specifically around the origin of the left circumflex artery. In the stent group, the stent was put in the myocardial channel and fixed. The pericardium and chest were then closed. The animals were allowed to recover and were ambulatory before leaving the operating room suite. Six weeks later, the animals were harvested. The myocardial tissue and stent were taken out for characterization. Main outcome measures BSA content in stent and the volume released in vitro; mechanical property of stent; stent structure; in vitro evaluation of stent effects on myocardial channel after TMR. Design, enforcement and evaluation All authors. RESULTS Morphological and structural study of stents A bi-layer porous system, with two different biodegradable polyesters in PCL and PLGA, was prepared. The system comprised a base support layer made from PCL, which represents the stent materials, and a drug eluting PLGA layer. Figure 1 shows the bi-layered and 1-mm-diameter porous structure of stent. In vitro BSA release In vitro release of BSA from PLGA stents in PBS at 37 was investigated. Figure 2 represents the in vitro BSA accumulated release data for 30 days at regular intervals. It was found that almost 60% of BSA was released in the first day with a burst release. In the following days, it was a sustained release compared to the first day. After 30 days, about 80% of BSA was released. Mechanical strength of stents The stress-strain relationship of stents showed that the imporous stent diminished 80% of initial scale under the stress of 1.7 MPa. The porous stent could sustain less pressure, only 1.2 MPa at the same condition. Effects of stent on animal myocardial channel Two animals were excluded because of an intractable ventricular fibrillation after ligation. Twelve animals survived for the subsequent procedures. Stent implantation did not induce severe events of malignant arrhythmia, embolization, bleeding and hemodynamic abnormality, etc. Six weeks later, the animals were harvested. The myocardial tissue with stent was taken out and subjected to scanning electron microscopy. As shown in Figure 3, the myocardial channel was still kept open with stent. The stent did not degrade fully and loss the sustain ability. The results showed that the drug release layer had degraded fully and the properties of PCL remained. However, in the blank control group, the TMR channels of animals were closed. Figure 1 Morphologica