Functionalization Mesoporous Silica Nanomaterials,Drug Loading And Release Studies In Vitro

Chemotherapy is still the most important cancer treatment strategy in clinical practice at present.However,due to the inability of chemical drugs to identify normal cells and cancer cells,the treatment process caused great physical and psychological pain to patients.In response to this defect,the researchers proposed the concept of drug delivery system（DDS）,which aims to deliver chemical drugs to cancer site in a more controlled manner to minimize their side effects.Mesoporous silica nanomaterilas（MSN）has been widely used in drug delivery systems due to its unique mesoporous structure,easy surface modification,good biocompatibility and degradability.The research also showed that the morphology of MSN has a unique advantage in its biological effects.Therefore,three kinds of MSN with different surface morphology characteristics were prepared in this paper,and the folic acid（FA）targeting molecules and polyethylene glycol（PEG）molecules were modified with silane coupling agent,and a functional drug delivery system（DOX@MSN-x-PEG-FA）with p H response,targeting and good blood compatibility was constructed.The drug loading and release mechanism of DOX@MSN-x-PEG-FA was preliminarily explained through a kinetic model,and its cytological behavior was investigated in vitro.（1）In this paper,three kinds of mesoporous silica nanomaterials with different surface morphology characteristics（MSN-x,x is the amount of rosin added,mg）were synthesized by controlling the amount of rosin.Among them,MSN-80 has the largest specific surface area and pore volume,S_BETis 726.44 m²g^-1,and pore volume is 0.136cm³g^-1.The post-grafting method was used to modify the surface carboxyl groups of the prepared MSN and further loaded with the anti-tumor drug doxorubicin hydrochloride（DOX）.The loading rate of the drug were calculated to be 8.398%（MSN-40）and 7.260%（MSN-60）and 9.545%（MSN-80）.The kinetic model fitting data of the drug loading process showed that the DOX loading process has the highest correlation with the pseudo-second-order kinetic model,and the correlation coefficient R²is greater than 0.99,suggesting that the drug loading process is mainly carried out by chemical adsorption（covalent bond bonding）.（2）Using the amino-active sites at both ends of the amino-terminated polyethylene glycol（NH₂-PEG-NH₂）and the carboxyl sites on the folic acid molecule and MSN-x-COOH molecule,a good biocompatibility and targeted drug delivery system was constructed,The synthesis of amino terminated polyethylene glycol and the grafting of functional molecules were characterized by ¹HNMR,IR,XRD,TG and Zeta potential etc.Evaluation of the hemolytic properties of MSN-x through blood compatibility assay:due to the shielding effect of PEG chains on the reactive oxygen species（ROS）induced by the surface of silanol groups and the electrostatic interaction between silica and membrane proteins,PEG-modified MSN significantly reduced its hemolysis rate by 1.681%（MSN-40-PEG）,1.733%（MSN-60-PEG）and2.253%（MSN-80-PEG）.（3）In order to simulate the drug release process in tumor tissues,we conducted in vitro drug release experiments under different physiological conditions（p H=7.4and p H=5）,and performed kinetic fitting to explain the possible drug release mechanism initially:First of all,DOX@MSN-x-PEG-FA showed a obvious p H-responsive drug release behavior,and achieved a"zero release"characteristic within the first 3-4 h.The whole process of drug release was segmentally fitted according to the Korsmeyer–Peppas equation.The values of n in the anterior segment were more than 0.89,indicating that the mechanism of action is skeleton dissolution.The values of n in the posterior segment was in the range of 0.45–0.89,indicating that the release mechanism is the anomalous（non-Fick）transport mechanism.Therefore,the release of DOX from the carrier materials（DOX@MSN-x-PEG-FA）may be jointly affected by the dissolution of the skeleton and the diffusion of irregular diffusion（non-Fick）.Based on these values and the drug release fit curve,the process of speculating the release mechanism may be as follows:（1）First,the solvent penetrates into the drug carrier material.Due to the function of chemical bonds and polymer encapsulation,DOX exhibited zero pre-release in the initial 3–4 hours,then the drug molecules began to penetrate gradually;（2）DOX diffuses to the surface of the drug carrier materials under a concentration gradient and further releases the drug;（3）The covalent bond dissociates and drug desorption occurs on the surface of the nanocarriers,and then diffuses into the solvent gradually.（4）In vitro cytological evaluation of the DOX@MSN-x-PEG-FA drug delivery system using MTT:the DOX-loaded nanoparticles exhibited concentration-dependent cytotoxicity.Among them,MSN-60 and MSN-80 exhibited higher cytotoxicity.The modification of folic acid molecule significantly improved the targeted uptake ability of DOX@MSN-x-PEG-FA drug delivery system to Hela cells.The phagocytosis of the cell leads to the strong local deformation of the membrane,and the local contact between the membrane and the non spherical particles is conducive to cell uptake.In addition,the apoptosis rate of DOX@MSN-80-PEG-FA（84.86%）was significantly higher than that of the other two groups of DOX@MSN-40-PEG-FA（37.93%）and DOX@MSN-60-PEG-FA（40.22%）,which may be due to the highest drug loading amount of DOX@MSN-80-PEG-FA and the thinner surface morphology（favorable for cell internalization）.