Study On Antibacterial Action And Hydrogel-Based Delivery Of Arginine End-Tagging Peptides

The rapid increase in the incidence of multidrug-resistant bacteria has become a global public health problem.Moreover,the decline in the effectiveness of advanced anti-biological therapies has worsened the treatment of bacterial infections.Therefore,there is an urgent need to discover new antimicrobial agents and advanced therapies.Antimicrobial peptides(AMPs)have attracted much attention due to their broad-spectrum activity,multiple mechanisms of action,and low drug resistance tendency.However,poor physiological stability and low biocompatibility severely restrict the bioavailability of peptide-based antimicrobial drugs.Different strategies have been adopted to address this issue,including engineered peptidomimetics and peptide dendrimers through chemical methods.Considering the diversity of AMPs’ structure and sequence and that the chemical modification significantly changes the physical and chemical properties and spatial arrangement of AMPs,the influence on the biological activity and toxicity of AMPs is often uncontrollable.Development and optimization of delivery systems for AMPs are another strategy,i.e.,through nanomedicine-based approaches,including attachment,encapsulation,responsive release,and co-assembly for the controlled release of AMPs directly at the infection sites.Given this,we designed different amino acid end-tagging AMPs and screened out arginine end-tagging peptides with great activity,high biocompatibility,and excellent stability in this study.Meanwhile,a supramolecular nano hydrogel with a sustained-release function was assembled via physical cross-linking.Specific research contents are as follows:(1)"RWWWR" was used as the central motif,and its end was tagged with different amino acids.The activity and toxicity experiments showed that the central motif with arginine(R)end-tagging had high antimicrobial activity(including clinically acquired multidrug-resistant bacteria)and outstanding biocompatibility.It also has a robust ability to inhibit and disrupt methicillin-resistant Staphylococcus aureus(MRSA)biofilm.Studies on the mechanism of action showed that arginine end-tagging peptide killed pathogenic microorganisms through physical membrane breaking,and drug resistance analysis of30 days of serial passages showed that arginine end-tagging peptide almost did not cause bacterial drug resistance.These results indicate that arginine end-tagging peptide has excellent clinical application potential.(2)Stability experiment results showed that arginine end-tagging peptide in physiological salt concentration solution,serum,and high-temperature environment maintain excellent antimicrobial ability.Therefore,different animal experiments were used to further study the in vivo activity of arginine endtagging peptide(Pep 6).After Pep 6 treatment,the bacterial load in the wound of mice with skin burn infection decreased significantly.In E.coli bacteremia models,Pep 6 reduces bacterial colonization and substantially reduces inflammatory responses in animals.Meanwhile,studies of severe sepsis found that Pep 6 significantly increased the survival rate of mice.Based on the above,Pep 6 has great potential to address bacterial infections in the clinic.(3)Hydrogel-RL with supramolecular nanostructure was prepared by physical cross-linking of arginine end-tagging peptide(Pep 6).The hydrogel can sustainably release Pep 6 for 120 h and has excellent sustained antimicrobial ability and the effect of elimination-resistant bacteria biofilm.In addition,a single administration of Hydrogel-RL to a mouse model of chronic wound MRSA infection can significantly reduce the bacterial load in the wound.Further studies have shown that Hydrogel-RL promoted mice’s skin cell proliferation,reduced inflammation,accelerated re-epithelialization,and regulated muscle and collagen fiber formation,rapidly healing full-thickness skin wounds.Taken together,the characteristics of "RWWWR" and various amino acid end-tagging were used to design an arginine end-tagging peptide with great application potential in this study,which could be used to solve the public health problem of multidrug-resistant bacteria infection.Meanwhile,a supramolecular hydrogel with a sustained-release function was designed utilizing physical cross-linking.This study provides a favorable guarantee for solving the problem of toxicity and stability of AMPs and lays a solid foundation for the practical application of AMPs and fighting the problem of bacterial drug resistance.