Preparation Of Mesoporous Composite Nanoparticles And Their Application In Capturing Heavy Metals

BackgroundWith the rapid development of modern industrial technology,a large number of heavy metal ions have been dispersed into the air,such as Pb,Cd,Hg,Cr,As,etc.They can greatly enter and damage the human body through traditional food chain.Therefore,it is very necessary to remove heavy metal ions from the body.Owning to their high specific surface area,uniform tunable pore size,high affinity for heavy metals and high adsorption,Mesoporous silica nanoparticles(MSNs)have been used as in capturing agent in removing those heavy metal ions.However,the ability to capture of pure MSNs is relatively low because of their limited affinity.In order to further enhance their adsorption capacity of heavy metals,the MSNs can be modified with metal chelating agent on their surface with special active group to form new composite mesoporous nanomaterials.This work will provide a useful way to solve the above problems.PurposeThe mesoporous silica nanoparticles were modified with several grafted compound to form composite mesoporous nanomaterials as the trapping agent of heavy metal ions Pb²⁺and Cd²⁺.The removal effects of them on Pb²⁺and Cd²⁺were investigated under simulated conditions of gastrointestinal tract(p H 1.1 and 7.4).The biocompatibility of the materials was investigated through cytotoxicity experiments,which will provide scientific basis on the capture and removal of heavy metal ions in vivo.MethodMSNs were synthesized by sol-gel method,and the surface amino modification of MSNs(NH₂-MSN)was to increase the active sites on the surface of MSNs.On this basis,metal chelating agent(EDTA,glutathione,glutamic acid)was used to modify its surface to prepare nano-composite materials with better trapping effect.Then,the composite mesoporous materials were characterized by FT-IR,TEM,TGA,BET,small-angle XRD and particle size potential analyzer.MTT method was used to detect the biocompatibility of pure MSNs and composite mesoporous materials by Caco-2 cell line.Results1.The results showed that the MSNs synthesized by sol-gel method appeared uniform particle size and the fingerprint-like mesoporous structure could be seen.The inner porous was about 7 nm and the particle size was about 100 nm in diameter.2.The results of the in vitro adsorption on the capturing of heavy metals such as Pb²⁺and Cd²⁺in different initial concentration of deionized water solution showed that all the removal rates of the new fabricated composite mesoporous nanomaterials were more than reached 85%,regardless of the dosages of trapping agent and the different p H of deionized water.3.The Langmuir model and Freundlich model can be used to interpret the adsorption isotherms of the two heavy metal ions.The results showed that the fitting curve adsorption pattern isotherm was consistent with Freundlich model,which indicated that the adsorption of was not limited to monomolecular layer adsorption,but to multi-layer adsorption.4.The cytotoxicity of Caco-2 cell lines and the hemolysis of rat red blood cells were investigated to evaluate the biocompatibility of the prepared trapping agent.The results showed that when different concentration gradients of MSNs were added,the cell survival rate could reach more than 95%or even more than 100%,while the hemolytic experiment indicated that the hemolysis rate was less than 5%.ConclusionMesoporous nanomaterials have significant removal effect on Pb²⁺and Cd²⁺,and have good biocompatibility,providing theoretical and technical support for the capture of heavy metal ions in vivo.