Degradable Poly(β-amino ester) Nano Delivery Systems with On-Demand Release for Synergistic Control of Tomato Bacterial Wilt

Structural design of degradable polymers provides a versatile platform for precision agrochemical delivery; however, the application of poly(β-amino esters) (PAE)─a class of materials widely utilized in biomedical fields─remains largely unexplored in managing complex soil-borne agricultural diseases. In this study, poly(β-amino esters) (PAE) with precisely controlled hydrophilic–hydrophobic balances were synthesized via Michael addition polymerization to encapsulate the potent antibiotic pleuromutilin (PLE). To align the delivery profile with the “acute outbreak and persistent infection” stages of tomato bacterial wilt ( Ralstonia solanacearum ), a mixed delivery system was innovatively engineered by blending fast- and slow-release PAE variants at a 2:1 mass ratio. Pot experiments demonstrated that this binary blended system achieved superior and stable control efficiencies of 71.42% and 52.63% at 7 and 14 days postinoculation, respectively, effectively resolving the inherent spatiotemporal mismatch of conventional formulations. Temporally, the dual-release profile bridges the efficacy gap associated with rapid decay. Spatially, the cationic PAE overcame off-target leaching by ensuring targeted deposition and localized retention (>90%) within the rhizosphere (0–4 cm). Crucially, the system exhibited negligible upward systemic translocation, reinforcing root-targeted delivery while minimizing pesticide residue risks in above-ground edible tissues. Mechanistically, this cationic PAE also promoted synergistic antibacterial activity via electrostatic membrane disruption. Furthermore, PAE encapsulation significantly enhanced the environmental stability of PLE, maintaining >50% retention after 4000 min of intense UV irradiation. Coupled with a 10-fold reduction in acute toxicity toward nontarget earthworms, this structurally tunable PAE platform provides a robust and sustainable strategy for the precision spatiotemporal management of soil-borne bacterial diseases.