Photoresponsive CuS@polyaniline nanocomposites: An excellent synthetic bactericide against several multidrug-resistant pathogenic strains

Abstract

Surface modifications can optimize the antibacterial properties of inorganic materials; however, their high-cost, lengthy synthesis, and limited efficacy remain challenges in combating antibiotic resistance. Herein, we employed a rapid and low-cost solvothermal synthesis technique, followed by in situ oxidative polymerization of aniline to develop polyaniline-coated copper sulfide nanocomposites (CuS@PANI NCs), utilizing CuS and PANI as reactants to achieve efficient alternative bactericides. The as-prepared CuS@PANI NCs were initially investigated for structural, morphological, optical, and other spectroscopic analyses, confirming the successful coating of PANI onto the CuS nanoparticles. The in vitro case–control studies demonstrate the exceptional bactericidal performance of the CuS@PANI NCs against both Gram-positive (S. aureus and S. pneumoniae) and Gram-negative (E. coli and P. aeruginosa) bacteria with higher efficacy under visible light exposure at a dose as low as 30 μg ml⁻¹, compared to the pure CuS (60 μg ml⁻¹) and standard antibiotic ciprofloxacin (15 μg ml⁻¹), respectively, as evidenced by the respective zone inhibition assays. Radical trapping experiments coupled with electron spin resonance (ESR) measurements confirm that the ˙O₂⁻ and h⁺ stand as the primary active species in the system. Moreover, the obtained results from computational simulations (in silico) of the as-synthesized materials against selected proteins (β-lactamase^{E. Coli} and DNA gyrase^{E. coli}) are in good agreement with the in vitro antibacterial findings, providing consistent validation. This study provides compelling evidence supporting potential of the polymers@inorganic composite materials as a powerful tool to combat antibiotic resistance to reduce the risk of infectious diseases.