Singh Rinki, Pal Dipayan, Chattopadhyay Sudeshna
Discipline of Biosciences and Biomedical Engineering, Indian Institute of Technology Indore, Indore 453552, India.
Discipline of Physics, Indian Institute of Technology Indore, Indore 453552, India.
ACS Omega. 2020 Aug 20;5(34):21768-21780. doi: 10.1021/acsomega.0c02817. eCollection 2020 Sep 1.
Superparamagnetism has been widely used for many biomedical applications, such as early detection of inflammatory cancer and diabetes, magnetic resonance imaging (MRI), hyperthermia, etc., whereas incorporation of superparamagnetism in stimulus-responsive hydrogels has now gained substantial interest and attention for application in these fields. Recently, pH-responsive superparamagnetic hydrogels showing the potential use in disease diagnosis, biosensors, polymeric drug carriers, and implantable devices, have been developed based on the fact that pH is an important environmental factor in the body and some disease states manifest themselves by a change in the pH value. However, improvement in pH sensitivity of magnetic hydrogels is a dire need for their practical applications. In this study, we report the distinctly high pH sensitivity of new synthesized dual-responsive magnetic hydrogel nanocomposites, which was accomplished by copolymerization (free-radical polymerization) of two pH-sensitive monomers, acrylic acid (AA) and vinylsulfonic acid (VSA) with an optimum ratio, in the presence of presynthesized superparamagnetic iron oxide nanoparticles (FeO(OH) ). The monomers contain pH-sensitive functional groups (COO and SO for AA and VSA, respectively), and they have also been widely used as biomaterials because of the good biocompatibility. The pH sensitivity of the superparamagnetic hydrogel, poly(acrylic acid--vinylsulfonic acid), PAAVSA/FeO, was investigated by swelling studies at different pH values from pH 7 to 1.4. Distinct pH reversibility of the system was also demonstrated through swelling/deswelling analysis. Thermal stability, chemical configuration, magnetic response, and structural properties of the system have been explored by suitable characterization techniques. Furthermore, the study reveals a pH-responsive significant change in the overall morphology and packing fraction of iron oxide nanoparticles in PAAVSA/FeO via energy-dispersive X-ray (EDX) elemental mapping with the field emission scanning electron microscopy (FESEM) study (for freeze-dried PAAVSA/FeO, swelled at different pH values), implying a drastic change in susceptibility and induced saturation magnetization of the system. These important features could be easily utilized for the purpose of diagnosis using magnetic probe and/or impedance analysis techniques.
超顺磁性已被广泛应用于许多生物医学领域，如炎症性癌症和糖尿病的早期检测、磁共振成像（MRI）、热疗等，而将超顺磁性引入刺激响应水凝胶目前已在这些领域的应用中引起了广泛关注。最近，基于pH是体内重要的环境因素且某些疾病状态会通过pH值变化表现出来这一事实，已开发出在疾病诊断、生物传感器、聚合物药物载体和可植入设备中具有潜在用途的pH响应超顺磁性水凝胶。然而，提高磁性水凝胶的pH敏感性是其实际应用的迫切需求。在本研究中，我们报道了新合成的双响应磁性水凝胶纳米复合材料具有显著的高pH敏感性，这是通过两种pH敏感单体丙烯酸（AA）和乙烯基磺酸（VSA）以最佳比例在预先合成的超顺磁性氧化铁纳米颗粒（FeO(OH) ）存在下进行共聚（自由基聚合）实现的。这些单体含有pH敏感官能团（AA和VSA分别为COO 和SO ），并且由于良好的生物相容性，它们也已被广泛用作生物材料。通过在pH值从7到1.4的不同pH值下进行溶胀研究，对超顺磁性水凝胶聚（丙烯酸 - 乙烯基磺酸）PAAVSA/FeO的pH敏感性进行了研究。通过溶胀/去溶胀分析也证明了该系统具有明显的pH可逆性。通过合适的表征技术探索了该系统的热稳定性、化学结构、磁响应和结构性质。此外，该研究通过场发射扫描电子显微镜（FESEM）研究（针对在不同pH值下溶胀的冻干PAAVSA/FeO）结合能量色散X射线（EDX）元素映射揭示了PAAVSA/FeO中氧化铁纳米颗粒的整体形态和堆积分数随pH的响应性显著变化，这意味着该系统的磁化率和感应饱和磁化强度发生了剧烈变化。这些重要特性可很容易地用于使用磁性探针和/或阻抗分析技术进行诊断的目的。
