Preparation And Application Of ZIF-8-based Composite Antibacterial Materials

The rapid emergence of antibiotic-resistant bacteria is occurring worldwide,endangering the efficacy of antibiotics,which leads to great losses to the world economy.Therefore,developing novel antibacterial materials is an urgent demand.Zeolitic imidazolate framework-8?ZIF-8?are built from zine ions and 2-methylimidazolate.They have unique merits including easy functionalization,good biocompatibility,high porosity,and large loading capacity,which is an ideal carrier for preparing composite antibacterial materials.However,these ZIF-8-based antibacterial nanocomposites mostly used single antibacterial method,and their antibacterial effect was limited.It is therefore important to combine two or more antibacterial methods into one composite material for increased antibacterial effect.In the present work,we firstly decorate AgNPs on ZIF-8 by assistance of PDA shell to enhance the stability of AgNPs,and then integrate chemical antibacterial?from AgNPs?and photothermal antibacterial methods into one composite material to realize more efficient antibacterial effects.This study including two aspects as follows:In the first part,AgNPs is grafted on the surface of PDA-modified ZIF-8 to form ZIF-8/PDA/AgNPs nanocomposites by in site reduction of Ag⁺,which is favorable for decorating AgNPs with 23 nm and highly dispersive.PDA as a polymeric nanocoating possess a strong adhesion property and a unique ability to in situ reduce.The nanocomposites morphology can be easily tuned through adjusting the concentration of HDA and silver nitrate and the reaction time.Moreover,this nanocomposites has excellent antibacterial activity against E.coli and S.aureus with MIC of 8?g/mL.In the second part,ICG was incorporated in ZIF-8 to form ICG@ZIF-8,then we decorate AgNPs onto the PDA-modified ICG@ZIF-8 to form ICG@ZIF-8/PDA/AgNPs nanocomposites.When 3.6 mM of ICG and 0.065 mg/mL of silver nitrate were added,composites with uniform morphology,good photothermal effect,and uniformly loaded AgNPs could be obtained.At a concentration of 250?g/mL,ICG_3.6@ZIF-8/PDA/AgNPs can be easily heated up to 69.5°C after 808 nm laser irradiation for 5 min,which is 7.6 and 16.4°C higher than ICG_3.6@ZIF-8/PDA and ICG_3.6@ZIF-8,indicating that both the PDA shell and AgNPs can also enhance the photothermal effect of the nanomaterial.Moreover,the inactivation of E.coli and S.aureus by ICG_3.6@ZIF-8/PDA/AgNPs?100?g/mL?reached 100%after 808 nm laser irradiation for 20 min.ICG_3.6@ZIF-8/PDA/AgNPs also has a certain antibacterial effect without laser irradiation,which proved chemical antibacterial effects from AgNPs and photothermal effects can effectively inhibits bacterial growth.The composite materials attach on the cellular membrane of E.coli and S.aureus and destruct the bacterial membrane due to the local overheating,which are observed by SEM.In short,this novel chemo-photothermal synergistic strategy shows great potential in combating bacteria than the use of single method.