Antibiofilm and Immunomodulatory Effects of Cinnamaldehyde in Corneal Epithelial Infection Models: Ocular Treatments Approach

<b>Background:</b> Bacterial keratitis, a major cause of corneal blindness, is frequently associated with biofilm-forming pathogens such as <i>Klebsiella pneumoniae</i>. Cyclic-di-GMP (c-di-GMP) controls biofilm development, which increases antibiotic resistance and makes treatment more difficult, highlighting the need for innovative therapeutic approaches. <b>Methods</b>: This study investigated cinnamaldehyde as a potential ocular therapeutic using combined computational and experimental approaches. Molecular docking and in vitro assays (XTT, resazurin reduction, crystal violet staining, qRT-PCR, and fluorescence microscopy) were used to evaluate the anti-biofilm and immunomodulatory activities of cinnamaldehyde (CA) against <i>Klebsiella pneumoniae</i>. <b>Results</b>: CA inhibited biofilm formation in a dose-dependent manner (≈89% at 1000 µM; >50% at 250 µM), reduced bacterial attachment to contact lenses, and downregulated key biofilm genes (<i>mrkA</i>, <i>mrkC</i>, <i>ybtS</i>, <i>bolA</i>). Docking analysis revealed strong binding affinity to the <i>mrkH</i> regulator (-5.46 kcal/mol. CA maintained more than 80% corneal cell viability by increasing IL-10, suppressing inflammatory mediators (IL-1β, IL-6, and TNF-α), and improving bacterial clearance. <b>Conclusions</b>: This study combines computational docking, biofilm quantification, immune cell assays, and functional gene expression analyses to reveal the ability of cinnamaldehyde not only to suppress biofilm formation but also to enhance macrophage-mediated clearance and modulate corneal immune responses, a multi-target approach not previously described in the context of bacterial keratitis. Such effects highlight its potential as a novel ocular drug candidate for protecting corneal integrity in infectious keratitis.