A PH-responsive Mesoporous Silica Antimicrobial Material Based On Imine Bonding

The volatility of natural active compounds makes it difficult to apply them on a large scale.Therefore,a controlled release means needs to be introduced to overcome its drawbacks.Mesoporous silica nanoparticles（MSNs）have attracted the attention of many researchers and are widely used in various fields because of their uniform pore size and particle size distribution,good biocompatibility,large specific surface area,and functionalized multifunctionality.In the past two decades,with the development of nanoswitch technology,a variety of intelligent controlled release systems have been developed based on mesoporous silica nanoparticles.Therefore,in this context,the p H-responsive mesoporous silica antimicrobial material based on imine bonding was constructed in this topic,so as to realize the controlled release of the inhibitory material to the inhibitory substance.In this project,four main aspects of this controlled-release antibacterial material were investigated as follows:1.characterization of the preparation of silica nanomaterials encapsulating citral and the study of bacterial inhibitionThe essential oil of citral was found to have excellent performance in bacterial inhibition through literature review,so citral was chosen as the experimental object.A series of characterization of silica nanomaterials encapsulated with citral was carried out to demonstrate the success of encapsulation.It was then investigated for bacterial inhibition experiments as well as in vitro release experiments,which revealed a better improvement in bacterial inhibition,probably because the ordered mesoporous structure slowed down its release and volatilization,making him more available.2.Preparation and characterization of p H-responsive mesoporous silica antimicrobial materials based on imine bondingIn this experiment,citral（CIT）with good antimicrobial properties was selected as the antimicrobial agent and"gating factor",and the amino-functionalized silica nanomaterials were used as carriers and loaded with citral by adjusting the p H value to obtain p H-responsive controlled-release antimicrobial materials.The materials were then examined by standard techniques,including scanning electron microscopy（SEM）,Fourier transform infrared spectroscopy（FT-IR）,thermogravimetric analysis（TGA）,N2 adsorption/desorption isotherms,and zeta potential analyzer.The results show that this material not only helps to stabilize the antimicrobial active substance,but also can be more attractive to foodborne microorganisms due to the structure and surface charge of the material.3.p H-responsive mesoporous silica antimicrobial material based on imine bonding for controlled release and its antibacterial effectThe p H of E.coli will drop to about 5.2 during the growth process,so the controlled release ability of the synthesized materials can be tested by adjusting the corresponding environmental p H.Through the experiment,it was found that the citral could be controlled stably at p H>6.8,while at p H≤6.8,the citral started to be released rapidly.And the release rate of citral was faster as the acidification level increased.This finding demonstrated the p H sensitivity of this amine-bond-based bacterial inhibitory material and confirmed the p H-responsive controlled-release bacterial inhibitory ability of the material.It was then subjected to in vitro bacterial inhibition experiments,where a typical food-borne microorganism,Escherichia coli,was chosen as a reference.By comparing the antibacterial properties as well as the long-lasting inhibition ability between different inhibition materials,it was found that this p H-responsive mesophilic inhibition material not only has long-term antibacterial performance,but also improves the antibacterial efficiency of citral.Therefore,it is feasible to apply this material for p H-responsive inhibition as well as long-lasting inhibition,which has considerable development prospects.4.p H-responsive mesoporous silica antimicrobial materials based on imine bonding for coconut milk sterilization applicationIn this experiment,the prepared p H-responsive antibacterial materials（M-NH₂-CIT@CIT）and the silica nanomaterials encapsulated with citral only（M-CIT）were used to sterilize coconut juice inoculated with E.coli respectively.The bactericidal ability of the materials was measured,and it was found that the bactericidal performance of M-NH₂-CIT@CIT was slightly better than that of M-CIT,but the long-lasting bactericidal performance of M-NH₂-CIT was much better than that of M-CIT.In addition,various sensory measurements of the coconut juice after the bactericidal treatment were performed,and it was found that this cold sterilization treatment had less effect on the food quality.Therefore,the application of this p H-responsive bacteriostatic material to food sterilization has a very high potential and prospect.