A Sequential Therapeutic Strategy Based on Aptamer/Polymer-Functionalized PDA/Ag for Precise Acinetobacter Baumannii Imaging and Pneumonia Treatment

Abstract

Acinetobacter baumannii (A. baumannii) is a leading cause of pneumonia. Conventional antibiotics can increase the risk of drug resistance and non-specifically harm microflora, disrupting their balance. In addition to pathogenic bacteria, lung inflammation also damages tissue. This study develops an aptamer/polymer-functionalized mesoporous polydopamine/silver nanocomposite (Apt/ODEA-PDA/Ag-ICG) to specifically target A. baumannii and sequentially exhibit antibacterial/antioxidative properties for pneumonia treatment. After synthesizing the polyzwitterion (ODEA), the polymer/aptamer is conjugated with the PDA/Ag core, and ICG is further labeled to fabricate the nanocomposite. Upon intratracheal instillation, nanocomposites penetrate the mucus barrier with the help of polyzwitterions. The nanocomposite precisely targets A. baumannii through specific recognition by the aptamer, without affecting other microflora. Moreover, ICG is conjugated and distributed disorderedly within the polymer. ICG near the PDA/Ag core contributes to high NIR-I absorbance and good photothermal ability. ICG further from the PDA/Ag acts as a fluorescent molecule for specific A. baumannii imaging. Furthermore, PDA/Ag efficiently exhibits synergistic antibacterial activity owing to the acidic environment/heat-accelerated Ag⁺ release and photothermal effect. Importantly, alongside Ag⁺ release, the antioxidant ability of PDA scavenges reactive oxygen species and alleviates inflammation, thereby accelerating pneumonia treatment. In summary, nanocomposites provide an alternative approach for designing advanced antibacterial systems.