The novelty of the present work was focused on the synthesis of pH- and temperature-responsive cross-linked poly(methacrylic acid-co-acrylamide) (p(MAA-co-AM)) microgels for controlled drug delivery. A series of cross-linked microgels was successfully prepared by inverse-suspension polymerization using N,N′-methylenebisacrylamide as a cross-linking agent and potassium persulfate as an initiator. The swelling of the microgels was investigated as a function of pH (2.1 and 7.4) and temperature (20–50°C). The prepared microgels were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), particle size analysis and drug-release behavior analysis. FTIR and thermal studies confirmed the formation of a new cross-linked p(MAA-co-AM) polymer. SEM revealed that the microgels were made of spherical, slightly rough and cross-linked particles. To study the controlled-drug-release behavior of microgels, captopril was successfully loaded as a model drug by using an in situ method. The maximum in vitro drug release was up to 96 and 55% at pH 7.4 and 2.1, respectively. All formulations showed pH-dependent drug release following the Higuchi model of drug-release mechanism. In light of the results obtained from the study, it was concluded that p(MAA-co-AM) microgels have potential applications in release of drugs in a controlled manner with respect to pH and temperature.

中文翻译：

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刺激敏感的可控药物微凝胶的开发和评估

本工作的新颖性集中于合成pH值和温度响应的交联聚（甲基丙烯酸-共-丙烯酰胺）（p（MAA-共-AM））微凝胶以控制药物的输送。通过N，N的逆悬浮聚合成功制备了一系列交联的微凝胶。'-亚甲基双丙烯酰胺为交联剂，过硫酸钾为引发剂。研究了微凝胶的溶胀与pH（2.1和7.4）和温度（20–50°C）的关系。通过傅立叶变换红外光谱（FTIR），差示扫描量热法，X射线衍射，热重分析，扫描电子显微镜（SEM），粒度分析和药物释放行为分析对制备的微凝胶进行表征。FTIR和热学研究证实了新的交联p（MAA- co-AM）聚合物。扫描电镜显示，微凝胶是由球形，略微粗糙和交联的颗粒制成的。为了研究微凝胶的药物释放控制行为，通过使用原位方法成功地将卡托普利加载为模型药物。在pH 7.4和2.1下，最大的体外药物释放分别高达96％和55％。遵循Higuchi药物释放机理模型，所有制剂均显示pH依赖性药物释放。根据从研究中获得的结果，可以得出结论，p（MAA- co- AM）微凝胶在控制pH和温度的方式释放药物方面具有潜在的应用。