In Vitro Evaluation of Antibacterial Properties of NIR-Light Responsive Alginate Hydrogels Embedding Polydopamine Nanoparticles

Bacterial infections are one of the most serious health problems worldwide and represent a significant threat to humans. In this article, we designed an injectable alginate-based hydrogel embedding polydopamine nanoparticles (nPDA) and applied it as a (nano)phototherapeutic agent and nanocarrier for photodynamic (PDT) and photothermal (PTT) therapies with the perspective of treating bacterial infections and overcoming microbial resistance. For this purpose, nPDA were functionalized with Chlorin e6 as a photosensitizer and embedded in an alginate hydrogel to apply the PDT treatment. The photothermal properties of nPDA were exploited for the “on demand” local release of antibiotics such as Ciprofloxacin (for Gram-negative bacteria) and Rifampicin (for Gram-positive bacteria) to address respectively Escherichia coli and Staphylococcus s aureus as these antimicrobial-resistant pathogens are commonly found in bacterial infections. In vitro experiments have shown that PDT and PTT treatments were both highly efficient for the treatment of S. aureus, leading to the complete eradication of this bacterium. On the contrary, PDT was less effective for treating E. coli, while PTT revealed an excellent antibacterial activity toward this pathogen.