Novel Poly-(Lactic-Co-Glycolic Acid) Targeted Nanoparticles Conjunct with Antibody for the Enhancement of Antibacterial Activity against Ralstonia solanacearum

Due to the strong pathogenicity of Ralstonia solanacearum, a variety of strategies have been used to develop antibacterial agents; however, antibacterial drugs with targeted effects on R. solanacearum remain lacking. Herein, we present a nanoagent targeting R. solanacearum based on our previous research on poly-(lactic-co-glycolic acid) (PLGA) particles (PLGA-NPs) loaded with methyl caffeate and caffeic acid phenethyl ester. Antibodies that have specific effects on R. solanacearum, which were verified using immuno-PCR, were first used to prepare PLGA-targeted nanoparticles (PLGA-TNPs). The antibody coupling process was investigated in terms of antibody binding degree and antibacterial activity. The EC50 value of PLGA-TNPs was 0.021 mg/mL, which was significantly reduced by 92% in comparison to PLGA-NPs. PLGA-TNPs had a perforating effect on the cell membrane of R. solanacearum, but no effects on Escherichia coli according to the SEM results. In addition, a downregulation of the pathogenicity-related genes compared to PLGA-NP treatment was observed, and the expression of egl, phcA, phcB, pilT, polA-238, and pehC decreased by 78, 79, 87, 61, 58, and 41%, respectively. Therefore, PLGA-targeted nanoparticles not only enhance the activity against R. solanacearum, but also provide a new idea for controlling bacterial wilt.