Piperazine linked chitosan schiff base nanoparticles as a novel antibiofilm and antibacterial strategy against clinically relevant pathogens.

The development of multifunctional antimicrobial materials capable of targeting both planktonic bacteria and biofilm-associated infections remains a critical challenge in combating antimicrobial resistance. In this study, a novel piperazine-linked chitosan Schiff base (Cs-TPA-PiP) and its ionically crosslinked nanoparticle formulation (Cs-TPA-PiP NPs) were synthesized and structurally characterized. The antimicrobial potential of both Cs-TPA-PiP and Cs-TPA-PiP NPs was evaluated against a panel of nine standard clinically significant bacterial strains. The compounds demonstrated significant and broad-spectrum antibacterial activity. The minimum inhibitory concentration (MIC) values demonstrated potent efficacy, with Cs-TPA-PiP and its Cs-TPA-PiP NPs ranging from 0.63 to 2.50 mg/mL and 1.00-5.00 mg/mL, respectively. Notably, both agents exhibited a strong dose-dependent inhibitory effect on biofilm formation. While Cs-TPA-PiP showed lower MIC values against planktonic cells, the corresponding Cs-TPA-PiP NPs with an ultra-small spherical size of 15.6 nm exhibited superior antibiofilm performance, ranging from 73.00% to 95.00% inhibition of biofilm biomass at 1× MIC in strong biofilm-producing strains. Transmission electron microscopy (TEM) confirmed severe morphological alterations and membrane disruption in treated bacterial cells, consistent with a membrane-targeting mechanism. In silico molecular docking studies suggested that the compound has favorable binding affinity for the critical bacterial cell wall target, Sortase A, thereby identifying it as a potential theoretical target requiring further validation. Our findings collectively establish Cs-TPA-PiP and its Cs-TPA-PiP NPs as effective antibacterial and anti-biofilm candidates, with their activity primarily attributed to membrane disruption. The proposed role of Sortase A inhibition remains hypothetical and warrants further investigation. These findings highlight their potential as multifunctional antibacterial platforms for managing biofilm-associated and resistant bacterial infections.