Effect Of Iron Oxide Nanozymes In Cooperation With Probiotics And Microenvironment Regulation Strategy On Bacteria Inhibition And Wound Healing

Nowadays,antibiotic resistance has become a global health threat.Abusing of antibiotics can’t improve the germicidal efficacy but cause drug-resistant bacteria.Antibiotics is losing its efficacy.The strong momentum of antibiotic research gradually stagnated at the beginning of this century and the pace of new antibiotic development can’t catch up with the appearing of drug-resistant bacteria.One of the strategies to resist the risk of antibiotic resistance is to develop new antimicrobial agents as soon as possible.As an emerging nano material,nanozymes broke the limitations of typical enzymes(such as poor stability and high cost)and updated the definition of nano materials.It not only possesses the characteristics of nano materials but also owns the similar catalytic function like enzymes under physiological conditions,showing significant development potential in many important fields,especially in the field of biomedical sciences.Although H2O2 has been used for sterilization in clinic,the toxicity of high-dose H2O2 has always been a big problem.Iron oxide nanozymes(IONzymes)with peroxidase activity can catalyze low-dose H2O2 to hydroxyl radicals(·OH)thus reducing the drug toxicity of it.What’s more,·OH is easier to seep into the bacterial biofilms and can rapidly increase the intracellular ROS level of bacteria to kill them.It really owns so many advantages in the biofilm degradation.Lactobacillus is known as a typical kind of probiotics which is widely used in dairy production,gastrointestinal function regulation,immunity enhancement and so on.It is safe and controllable.Lactobacillus can provide IONzymes with acidic environment to play the roles of peroxidase activity and can also continuously secrete lactic acid to be catalyzed to H2O2 in low dose by exogenous lactic oxidase.Compared with the way of adding H2O2 in higher dose at one time,it showed safer and more lasting antibacterial effect.With the development of modern bioengineering technology,more and more gene engineering bacteria are applied to prevent and treat the diseases.It has been proved that chemokine CXCL12 can promote cell migration and accelerate tissue repair.We combined the function of the engineering Lactobacillus which can express CXCL12,ROS sterilization mechanism and micro-environment regulation strategy together to realize faster regrowth of Staphylococcus aureus infected wounds.This paper is divided into two parts about the oral biofilm degradation and wound healing acceleration.Here are the details:1.Iron oxide nanozymes in cooperation with Lactobacillus plantarum against the oral biofilmStreptococcus mutans is the most typical cariogenic bacteria.The key to prevent and cure dental caries is to control the biofilm of it.In this chapter,iron oxide nanozymes(IONzymes)in 40nm was prepared by solvothermal method.Its dispersion,stability and peroxidase activity got a big improvement by size reduction.We constructed an oral dual-species biofilm model of Streptococcus mutans and Lactobacillus plantarum.In this mixed biofilm model,lactic acid secreted by Lactobacillus plantarum could not only be continuously decomposed into low concentration H2O2 by lactic oxidase but also could be used to provide IONzymes with the necessary acidic environment for the peroxidase activity,thus triggering the chain catalytic reaction from H2O2 to·OH.It was observed that Lactobacillus plantarum made biofilm’s dense structure loose which was beneficial for drug to penetrate.IONzymes in experimental concentration had little toxicity to normal oral epithelial cells showing its good biosafety.After analyzing the result of dry weight and bacterial colonies number,we found that our scheme made the number of Streptococcus mutans in the biofilms decreased about 99.99%and the biofilm degradation rate could point to about 50%-65%for different time of treatment.Moreover,intracellular ROS level of Streptococcus mutans in biofilms significantly increased by 4 times after treatment.Whether it was on the surface of hydroxyapatite or human tooth slices,our scheme played a good effect against Streptococcus mutans and its biofilms.2.Iron oxide nanozymes in cooperation with engineering lactobacillus and micro-environment regulation strategy to accelerate wound healingCXCL12 is reported to be able to induce cell migration and accelerate damaged tissue regrow.In this chapter,we combined the function of gene engineering LactobacillusMG1363-CXCL12,ROS sterilization mechanism and micro-environment regulation strategy to kill Staphylococcus aureus and accelerate Staphylococcus aureus infected wound healing.MG1363-CXCL12 used in this research was proved to be able to secrete chemokines CXCL12.Together incubated for 24 hours,it could effectively induce HUVEC and RAW264.7’s migration and promote their scratch to get smaller.As a protease that plays an important role in inflammation and immune function,CD26 could not only catalyze chemokines but also affect the endothelial cells and angiogenesis.The enzyme activity result showed that CD26 was easily inactivated in acidic environment.Lactic acid secreted by MG1363-CXCL12 reduced the pH value of wound and thus inhibited the activity of CD26 to improve the bioavailability of CXCL12 and accelerate wound recovery.H2O2 catalyzed from lactic acid by lactate oxidase was able to kill bacteria in situ.’OH,catalyzed from H2O2 by IONzymes,could further accelerated the death of Staphylococcus aureus.Applied for 4 days,about 99%of the Staphylococcus aureus in the wound was inhibited,togethering with CXCL12 to push the wound recovery process.The animal experiment result showed that after 12 days’ treatment,mice in the control group still had about 50%unhealed wounds while the mice in the experimental group recovered completely.In fact,the wound recover rate of the experimental group had reached more than 60%on the 6th day.Histopathology results showed that our scheme could make CXCL12 has higher expression in the wound and induce macrophage to be recruited at that target area leading to less inflammatory cells,more collagen fibers and neovascularization.In a word,mice in the experimental group owned the fastest and best wound recovery situation among the six groups.Moreover,no significant adverse effects on the mice weight,main organs,blood routine index,hepatic and renal functions were observed indicating that our scheme had good biosafety.