Synthesis and antibacterial activity study of anti-biofilm agents based on American oyster defensin analog A4

Abstract

Chronic infections caused by bacterial biofilms represent a challenging clinical issue. The formation of biofilms markedly complicates the treatment of bacterial infections and frequently contributes to the development of drug-resistant strains. Anti-biofilm agents, encompassing a class of chemically or biologically active substances, are capable of inhibiting the formation of microbial biofilms or disrupting pre-existing biofilm structures. Antimicrobial peptides, as anti-biofilm agents, effectively interfere with the formation and stability of biofilms. As an analog of American oyster defensin (AOD), A4 displays superior antibacterial activity, diverse modes of action (including DNA interaction and inhibition of DNA amplification), and low toxicity. The purpose of this study is to develop new anti-biofilm agents with higher activity and better stability based on A4. By tuning amino acid configuration and substituting disulfide bonds, four analogs (D-A4, A4-T1, A4-T2, and A4-T3) were designed and synthesized. Results of antibacterial assays indicated that all analogs maintained broad-spectrum antibacterial activity, with D-A4 exhibiting enhanced antibacterial efficacy. Crystal violet staining assays demonstrated that D-A4 effectively inhibited biofilm formation at concentrations as low as 1/2 × MIC. Stability assays revealed that D-A4 exhibited high stability in both proteolytic and serum environments. With potent activity, excellent stability, and low toxicity, D-A4 holds great promise as an anti-biofilm agent against multidrug-resistant bacterial infections.