Design And Synthesis Of Photosensitizer Quaternary Ammonium Salt And Its Application In Seawater Desalination And Hemostatic Materials

Microbial contamination has always been one of the most severe pollutions in the world.It not only appears in the food and medical fields but also impacts industry,energy,and other fields.How people fight against microbial contamination has also developed from physical and chemical methods to various antibiotics.Physical methods are cumbersome and inefficient,chemical methods have limited application scenarios,and antibiotics have high efficiency and low dosage.They can kill most bacteria,making them the most widely used anti-biofouling methods.However,with the widespread use and even abuse of antibiotics,bacterial resistance to antibiotics has become a severe problem,and antibiotic resistance(AMR)has become one of the significant public health threats in the 21 st century.In order to cope with antibiotic resistance,scientists have developed a new type of antibacterial mechanism-photodynamic antibacterial.The basic principle of photodynamic antibacterial is that photosensitizers use light sources of appropriate wavelengths to convert oxygen molecules into reactive oxygen species that destroy cell structures.The advantage of this antibacterial method is that it will not increase the resistance of bacteria,but the disadvantage is that a fixed light source is required.Therefore,in order to solve this ’ flaw ’,I combined photosensitizer with a quaternary ammonium salt,using the efficient bactericidal characteristics of photosensitizer to make up for the lack of bactericidal efficiency of quaternary ammonium salt,and using the cationic antibacterial mechanism of quaternary ammonium salt to make up for the short board of light source needed by the photosensitizer.Based on theoretical calculations,we designed and synthesized a photosensitizer quaternary ammonium salt 3T-DMAEMA.The main research contents and results are as follows:(1)The 3T-DMAEMA with low HOMO-LUMO energy gap value and high water solubility was designed by Gaussian,Molinspiration and Marvin Sketch software,and the ΔEst value was further calculated from 1.2808 e V for 3T-CHO to 1.0654 e V for 3T-DMAEMA to confirm the side effects of 3T-DMAEMA.The antibacterial properties of 3T-DMAEMA were also investigated and it was found that 3T-DMAEMA exhibited excellent antibacterial activity under light conditions,with an antibacterial rate of nearly 100%,and also 40% under dark conditions,indicating that 3T-DMAEMA has both photosensitive and quaternary antibacterial properties.Finally,ABDA and EPR experiments proved that the photodynamic antibacterial substance of 3T-DMAEMA was singlet oxygen.Combined with Zeta potential experiments,the antibacterial mechanism of3T-DMAEMA was explored.On the one hand,3T-DMAEMA relies on cationic groups to adsorb on the surface of negatively charged bacteria,resulting in uneven surface charges of bacteria and eventually leading to cell membrane rupture,content logistics,and bacterial death;on the other hand,3T-DMAEMA adsorbed on the surface of bacteria can also kill bacteria by using a light source to produce singlet oxygen and destroy cell structure.(2)The photosensitizer 3T-DMAEMA was grafted onto the cellulose acetate membrane by the grafting method.FTIR and XPS proved that the compound was successfully combined with the membrane by grafting.Then the contact angle,permeation flux,salt rejection,thermal stability,and periodicity of the grafted membrane QCA-RO were measured,proving that the grafting reaction did not have a great influence on the performance of the membrane itself.Finally,the antibacterial properties and anti-biofilm ability of the QCA-RO membrane were verified.It was proved that the QCA-RO membrane also had antibacterial properties under dark and light conditions and removed mature biofilm.(3)Application of the photosensitiser quaternary ammonium salt3T-DMAEMA to haemostatic sponges by freeze-drying and unidirectional freezing techniques to produce a haemostatic sponge material CMCSQ with124% porosity and 35 times the fluid absorption multiplier in an optimal raw material ratio;then,the therapeutic significance of CMCSQ on bacterially infected wounds was evaluated by establishing a mouse back wound model,as well as tissue analysis and inflammatory factor analysis of wounds.Finally,by establishing a mouse femoral artery trauma model,it was proved that the prepared CMCSQ sponge material has the potential to be applied in practice.