Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1049-001 Lisboa, Portugal.
Nanoscale. 2017 Sep 21;9(36):13485-13494. doi: 10.1039/c7nr03395h.
Mesoporous silica nanoparticles (MSNs) are excellent nanocarriers, featuring very high cargo capacity due to their large surface area and pore volume. The particle and pore dimensions can be accurately tuned, and both the internal and external surfaces allow versatile functionalization. We developed hybrid MSNs with diameters around 140 nm, with the external surface selectively modified with a temperature-responsive biocompatible copolymer to control cargo release. The nanoparticles feature either a polymer brush or a gel-like responsive shell, produced by grafting from RAFT polymerization of PEG-acrylate macromonomers. The hybrid nanoparticles have fluorescent molecules incorporated into the inorganic network providing excellent optical properties for traceability and imaging. The cargo release profiles are explained by a temperature-controlled "pumping" mechanism: at low temperature (ca. 20 °C) the polymer shell is hydrophilic and expanded, opposing cargo diffusion out of the shell and retaining the molecules released from the mesopores; above room temperature (ca. 40-50 °C) the polymer network becomes more hydrophobic and collapses onto the silica surface, releasing the cargo by a sponge-like squeezing effect. The release kinetics depends on the polymer shell type, with better results obtained for the gel-coated nanoparticles. Our proof-of-concept system shows that by modulating the temperature, it is possible to achieve a pumping regime that increases the release rate in a controlled way.
介孔硅纳米颗粒（MSNs）是出色的纳米载体，由于其具有较大的表面积和孔体积，因此具有很高的载物能力。颗粒和孔径可精确调节，内外表面都可进行多功能化修饰。我们开发了直径约 140nm 的混合 MSNs，其外表面经温度响应性生物相容性共聚物选择性修饰，以控制载物释放。纳米颗粒具有聚合物刷或凝胶状响应壳，通过 PEG-丙烯酰胺大分子单体的 RAFT 聚合接枝生成。这些混合纳米颗粒将荧光分子掺入无机网络中，为跟踪和成像提供了极好的光学性能。载物释放曲线可以通过温度控制的“泵送”机制来解释：在低温（约 20°C）下，聚合物壳亲水且膨胀，阻止壳内的货物扩散，并保留从介孔中释放的分子；高于室温（约 40-50°C）时，聚合物网络变得更疏水，并通过海绵状挤压作用塌陷到硅石表面，释放货物。释放动力学取决于聚合物壳类型，具有凝胶涂层的纳米颗粒的效果更好。我们的概念验证系统表明，通过调节温度，可以实现一种泵送模式，以可控的方式增加释放速率。
