A tubular-shaped Janus nanoparticle based on polydopamine that responds to near-infrared, magnetic, and pH stimuli is reported. The robust tubular polydopamine structure was obtained by optimizing the halloysite template-to-dopamine ratio during synthesis. The inner and outer surfaces of the tube were exposed at different steps of the template–sonication–-etching process, enabling the differential surface modification of these surfaces. Poly(ethylene glycol) (PEG) and poly(N-isopropylacrylamide) (PNIPAM) were grafted to the outer and inner surface of the nanotube, respectively. The PEG-coated surface limited aggregation of the nanoparticles at elevated temperatures. The PNIPAM-coated interior enhanced doxorubicin loading and endowed the nanoparticle with temperature-responsive behavior. The deposition of precipitated Fe₃O₄ nanoparticles further modified the nanoparticles. The resulting magnetic Janus nanoparticles responded to pH, temperature, and magnetic fields. Temperature changes could be induced by near-infrared laser, and all three stimuli were found to influence release rates of adsorbed doxorubicin from the nanoparticles. The interaction of the stimuli on release kinetics was elucidated using a linear mixed model; reduced pH and NIR irradiation enhanced release while applying a static magnetic field retarded release. Furthermore, the mechanism was shifted toward Fickian behavior by applying a static magnetic field and low pH conditions. However, NIR irradiation only shifted the behavior toward Fickian behavior at low pH.

中文翻译：

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多刺激响应 Janus 空心聚多巴胺纳米管

据报道，一种基于聚多巴胺的管状 Janus 纳米颗粒可响应近红外、磁和 pH 刺激。通过在合成过程中优化埃洛石模板与多巴胺的比例，获得了坚固的管状聚多巴胺结构。管的内表面和外表面在模板-超声-蚀刻过程的不同步骤中暴露出来，从而能够对这些表面进行不同的表面改性。聚（乙二醇）（PEG）和聚（N-异丙基丙烯酰胺）（PNIPAM）分别接枝到纳米管的外表面和内表面。PEG 涂层表面限制了纳米颗粒在高温下的聚集。涂有 PNIPAM 的内部增强了阿霉素的负载量，并赋予纳米颗粒温度响应行为。析出的 Fe ₃ O _4的沉积纳米颗粒进一步修饰了纳米颗粒。由此产生的磁性 Janus 纳米粒子对 pH、温度和磁场有反应。近红外激光可以诱导温度变化，并且发现所有三种刺激都会影响纳米颗粒中吸附的阿霉素的释放速率。使用线性混合模型阐明了刺激对释放动力学的相互作用；在施加静磁场延迟释放的同时，降低 pH 值和近红外辐射增强了释放。此外，通过施加静磁场和低 pH 条件，该机制向 Fickian 行为转变。然而，近红外辐射仅在低 pH 值下将行为转变为 Fickian 行为。