Investigating the release of active compounds and cytotoxicity of thymol/gallic acid/β-cyclodextrin bio-nanocomposite: a targeted strategy with the approach of disrupting the genes involved in the quorum sensing system and biofilm formation in P. aeruginosa (PAO1).

The quorum sensing (QS) system and cell-to-cell communication have had a significant impact on biofilm formation and virulence factor increase in Pseudomonas aeruginosa (P. aeruginosa), making this opportunistic pathogen a global concern and potentially life-threatening agent. The present study aimed to create an innovative pharmaceutical bio-nanocomposite (BNC) comprising thymol (THY) and gallic acid (GA) based on β-cyclodextrin (β-CD), which was used to investigate the release kinetics of active compounds, the level of cytotoxicity, antibacterial and anti-biofilm potential, and measuring the expression of genes effective in QS in the strain PAO1 pays P. aeruginosa. Based on this, physicochemical characteristics of the synthesized BNC were determined using Fourier transform infrared spectroscopy analysis (FTIR), UV-vis measurement, dynamic light scattering (DLS), zeta potential, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The BNC's antibacterial and anti-biofilm capabilities were assessed using the PAO1 reference strain of P. aeruginosa and the expression level of QS-effective genes (rhlI, rhlR, lasI, and lasR) in bacteria was also evaluated in the presence of the synthesized BNC. The results of FTIR spectroscopy show the formation of intramolecular hydrogen bonds between THY, GA and β-CD. Absorption peaks of the UV-vis spectroscopy spectrum of the synthesized BNC at wavelengths of 217 and 272 nm are confirmed successful encapsulation of the THY and GA into the β-CD. The maximum size of the synthesized BNC was recorded as 356.3 nm with a polydispersity index (PDI) of 0.816. SEM and TEM micrographs show the presence of THY/GA active compounds in the pores in β-CD and the formation of a dense polymer network. After 360 minutes of release kinetics, more than 70% of the complex's active chemicals had been released. The biological complex's low toxicity is indicated by average cell survival of more than 65% and the ability to preserve the spindle shape of normal fibroblast cells at high concentrations. The PAO1 strain has minimum inhibitory concentrations (MIC) of 323 and 199.6 μg/mL for minimal biofilm inhibition concentration 50% (MBIC₅₀). The decrease in rhlI and rhlR gene expression relative to the control group (without treatment) suggests that the active chemicals released from the biological complex interact and disrupt the QS pathway. Overall, the synthesized pharmaceutical complex has promise as a clever and effective option for future research and practical advances, as well as the development of complementary therapies.