Preparation of Porous Composites Consisting of Apatite and Poly(D,L-Lactide)
Preparation of Porous Composites Consisting of Apatite and Poly(D,L-Lactide)
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磷灰石与聚(D,L-丙交酯)多孔复合材料的制备
DOI：
10.4028/www.scientific.net/kem.240-242.167
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Y. Yokogawa
中科院分区：
文献类型：
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作者：
F. Nagata;T. Miyajima;Y. Yokogawa
在常温常压条件下制备了由生物可降解材料组成的微球多孔复合材料。以磷酸钙沉淀法为稳定剂，采用无皂乳液溶剂挥发法制备了聚乳酸（PLA）和羟基磷灰石（HAp）微球。将所得微球与溶解在溶剂中的PLA一起成型，并通过溶剂蒸发形成多孔材料。引言使用生物可降解微球形成多孔材料将有可能获得易于三维设计的骨移植材料[1]。生物可降解聚合物，如聚（D，L-丙交酯），聚乳酸，现在被用作骨植入材料。一般而言，PLA微球是在表面活性剂的辅助下通过乳液法制备的，但指出这些表面活性剂残留在最终产品中[2]，并且由于其不可生物降解性，可能对人体产生影响，例如过敏样反应。聚乙烯醇（PVA）最常用作表面活性剂，以稳定PLA微球的水包油乳化，但残留的PVA也被怀疑具有致癌性[3]。为了解决这一问题，我们一直在研究无表面活性剂的聚乳酸和羟基磷灰石微球的制备。本文报道了无表面活性剂的聚乳酸和羟基磷灰石微球的制备以及由微球组成的多孔材料的形成。方法采用水包油乳液溶剂挥发法制备聚乳酸/磷酸钙微球。将由PLA（Mw = 20，000;和子）和二氯甲烷组成的有机相倒入各种浓度的（CH 3COOH）2Ca水溶液中。搅拌混合物以产生乳液。将（NH 4）2 HPO 4水溶液加入到乳液中。为了比较，也在没有（CH 3COOH）2Ca和（NH 4）2 HPO 4水溶液的蒸馏水中搅拌有机相。将悬浮液在室温下搅拌24 - 72小时以除去二氯甲烷。将悬浮液过滤、洗涤并干燥以获得微球。将所得微球分成以下尺寸范围：<38; 38-75; 75-150; 150-300;和>300 μm。将得到的特定尺寸范围的微球与溶解的PLA混合，并通过注射过滤法或离心法成型以形成圆盘。使用SEM（HITACHI，S3000）和显微镜（Keyence，VH-6300）观察微球和模制盘的形态。通过XRD（MAC science，MXP 3）分析微球的相。关键工程材料在线：2003-05-15 ISSN：1662-9795，Vols. 240-242，pp 167-170 doi：10.4028/www.scientific.net/KEM.240-242.167 © 2003 Trans Tech Publications Ltd，Switzerland版权所有。未经Trans Tech Publications Ltd（www.scientific.net）的书面许可，不得以任何形式或任何方式复制或传播本文的任何内容。（Semanticscholar.org-13/03/20，21：20：33）结果和讨论使用磷酸钙沉淀制备无表面活性剂的微球。微球的形成取决于制备条件。当将有机相倒入蒸馏水中时，几乎所有的PLA作为附聚物沉积在搅拌磁体上，并且少量的颗粒分散在蒸馏水中。分散的颗粒没有形成微球。相比之下，当将有机相倒入（CH 3COOH）2Ca水溶液中，然后将（NH 4）2 HPO 4水溶液逐滴加入到乳液中时，通常获得微乳液并且回收微球。在（CH 3COOH）2Ca水溶液中制备的产物的SEM分析显示，没有观察到没有微球的其它产物（图1）。EDX分析证实了微球上Ca和P元素的存在（图2）。这些结果表明，磷酸钙在微球制备中起稳定剂的作用，并与PLA形成微球复合材料。微球的XRD图谱的峰与HAp的JCPDS值很好地一致，但它们很宽，这表明微球上的沉淀物是不完全结晶的HAp（图3）。从图4中可以看出，模制盘由微球的聚集体构成。盘的横截面图像显示它们在其基质中具有许多孔。CA
Porous composites made of microspheres consisting of only biodegradable materials were prepared under the condition at ordinary temperature and pressure. Poly (D,L-lactide) (PLA) and hydroxyapatite (HAp) microspheres were prepared by a surfactant-free emulsion solvent evaporation method using calcium phosphate precipitation as stabilizer. The obtained microspheres were molded with dissolved PLA in solvent and porous materials were formed by solvent evaporation. Introduction Formation of porous materials using biodegradable microspheres would have the possibility to obtain easily three-dimensional designed materials for bone grafts[1]. Biodegradable polymers such as poly (D,L-lactide), PLA are now used as bone implant materials. In general, PLA microspheres are prepared by emulsion method with the aid of surfactants, however it is pointed out that these surfactants remain in the final products[2] and may be affected to human body such as an allergy-like reaction because of their non-biodegradability. Poly(vinyl alcohol), PVA, is most frequently used as a surfactant to stabilize the oil-in-water emulsification for PLA microspheres, but the residual PVA is also suspected of carcinogenicity[3]. In order to solve this problem, we have been studying preparation of PLA and hydroxyapatite (HAp) microspheres without surfactants. In this paper, we report surfactant-free preparation of PLA and HAp microspheres and formation of porous materials consisting of the microspheres Methods An oil-in-water emulsion solvent evaporation method was used for PLA/calcium phosphate microsphere fabrication. The organic phase composed of PLA (Mw = 20,000; WAKO) and dichloromethane was poured in various concentrations of (CH3COOH)2Ca aqueous solution. The mixture was stirred to yield emulsion. (NH4)2HPO4 aqueous solution was added into the emulsion. For the sake of comparison, the organic phase was also stirred in the distilled water without both (CH3COOH)2Ca and (NH4)2HPO4 aqueous solutions. The suspension was stirred for 24 -72 h at room temperature to remove the dichloromethane. The suspension was filtered, washed and dried to obtain microspheres. The resulting microspheres were separated into the following size ranges: <38; 38-75; 75-150; 150-300; and >300 μm. The obtained microspheres of a specific size range were mixed with dissolved PLA and molded by injecting filtration method or centrifugation method to form a disc. The morphology of microspheres and molded discs were observed using SEM (HITACHI, S3000) and microscope (Keyence, VH-6300). Phase of the microspheres was analyzed by XRD (MAC science, MXP3). Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 167-170 doi:10.4028/www.scientific.net/KEM.240-242.167 © 2003 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,21:20:33) Results and Discussion Surfactant-free microspheres were prepared using precipitation of calcium phosphate. The formation of microspheres depends upon preparation condition. When the organic phase was poured in the distilled water, almost all of PLA were deposited as agglomeration on a stirring magnet and small amounts of particles dispersed in the distilled water. The dispersed particles were not form into microsphere. In contrast, microemulsions were generally obtained and microspheres recovered when the organic phase was poured in (CH3COOH)2Ca aqueous solution and then (NH4)2HPO4 aqueous solution was added drop by drop into the emulsion. SEM analysis of the products prepared in (CH3COOH)2Ca aqueous solution revealed that no other products were observed without microspheres (Fig. 1). EDX analysis confirmed the presence of the Ca and P elements on microspheres (Fig. 2). These results indicated that calcium phosphate played a role as stabilizer for microsphere fabrication and formed microsphere composites together with PLA. The peaks of XRD pattern of the microspheres were in good agreement with the JCPDS value of HAp but they were broad, which indicated the precipitate on the microspheres to be incompletely crystallized HAp (Fig. 3). As can be seen from Fig. 4, the molded discs were made up of aggregates of the microspheres. A cross section image of the discs revealed that they had many pores in their matrix. Ca