The development of drug delivery systems that are able to respond to the different pH gradients found in the human body is a research field of vast scientific and technological interests. With such a responsive system, a specific pH condition can be used as a stimulus to trigger the local drug-releasing, increasing the efficiency of treatments in comparison to the traditional ones of systemic drug administration. In this study, a responsive drug nanocarrier to acid pH was produced by coating mesoporous silica nanoparticles with an outer chitosan layer that was covalently bonded to the nanoparticle. Fluorescein dye (FL) was loaded into the nanocarrier and used as a spectroscopic probe to evaluate the kinetics of release in buffered solutions with pH 6.0, 7.2 and 8.0. The kinetics analysis using mathematical models demonstrated higher rates of release in pH 6.0 than in pH 7.2 or 8.0. However, the experimental procedure used to load the dye into the nanocarrier had a huge influence on the kinetic mechanisms of delivering. When the dye was loaded into the nanocarrier before the chitosan coating had been made, the FL release was sustained and controlled through a Fickian's transport mechanism. When the dye was loaded after the nanocarrier coating a burst release effect was observed in every pH evaluated, which indicated that the dye was loaded only in the external coating of CS and did not inside of the silica mesopores.

能够响应人体中不同pH梯度的药物输送系统的开发是一个具有广泛科学技术兴趣的研究领域。通过这种响应系统，特定的pH条件可以用作刺激来触发局部药物释放，与传统的全身药物给药相比，可以提高治疗效率。在这项研究中，通过用共价键合到纳米粒子上的壳聚糖外层包被介孔二氧化硅纳米粒子，制得了对酸pH值敏感的药物纳米载体。将荧光染料（FL）加载到纳米载体中，并用作光谱探针，以评估在pH 6.0、7.2和8.0的缓冲溶液中释放的动力学。使用数学模型进行的动力学分析表明，pH 6.0的释放速率高于pH 7.2或8.0。然而，用于将染料加载到纳米载体中的实验程序对传递的动力学机理有很大的影响。当在制备脱乙酰壳多糖涂层之前将染料加载到纳米载体中时，通过Fickian的转运机制来维持和控制FL的释放。当在纳米载体涂层之后负载染料时，在所评估的每个pH中观察到破裂释放效果，这表明染料仅负载在CS的外涂层中，而不负载在二氧化硅介孔的内部。当在制备脱乙酰壳多糖涂层之前将染料加载到纳米载体中时，通过Fickian的转运机制来维持和控制FL的释放。当在纳米载体涂层之后负载染料时，在所评估的每个pH中观察到破裂释放效果，这表明染料仅负载在CS的外涂层中，而不负载在二氧化硅介孔的内部。当在制备脱乙酰壳多糖涂层之前将染料加载到纳米载体中时，通过Fickian的转运机制来维持和控制FL的释放。当在纳米载体涂层之后负载染料时，在每个评估的pH中观察到爆裂释放效果，这表明染料仅负载在CS的外涂层中而不在二氧化硅介孔的内部。