Carlos Fernandes

Abstract Antibacterial resistance poses a critical public health threat, challenging the prevention and treatment of bacterial infections. The search for innovative antibacterial agents has spurred significant interest in quaternary heteronium salts (QHSs), such as quaternary ammonium and phosphonium compounds as potential candidates. In this study, a library of 49 structurally related QHSs was synthesized, varying the cation type and alkyl chain length. Their antibacterial activities against Staphylococcus aureus, including antibiotic-resistant strains, were evaluated by determining minimum inhibitory/bactericidal concentrations (MIC/MBC) <= 64 mu g/mL. Structure-activity relationship analyses highlighted alkyl-triphenylphosphonium and alkyl-methylimidazolium salts as the most effective against S. aureus CECT 976. The length of the alkyl side chain significantly influenced the antibacterial activity, with optimal chain lengths observed between C-10 and C-14. Dose-response relationships were assessed for selected QHSs, showing dose-dependent antibacterial activity following a non-linear pattern. Survival curves indicated effective eradication of S. aureus CECT 976 by QHSs at low concentrations, particularly compounds 1e, 3e, and 5e. Moreover, in vitro human cellular data indicated that compounds 2e, 4e, and 5e showed favourable safety profiles at concentrations <= 2 mu g/mL. These findings highlight the potential of these QHSs as effective agents against susceptible and resistant bacterial strains, providing valuable insights for the rational design of bioactive QHSs.

Abstract Catechol-O-methyltransferase inhibitors (iCOMT), such as entacapone, have been successfully employed to treat tremor-related symptoms of Parkinson's disease. However, iCOMT has been associated with a short half-life and poor oral bioavailability. Nanobased drug delivery systems have often been used to overcome this type of setbacks. Therefore, entacapone was encapsulated in PEGylated poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles (NPs) via a nanoprecipitation process, as well as in PEGylated nanostructured lipid carriers (NLCs) using a solvent emulsification/evaporation method. Both nanoformulations presented sub-200 nm populations, with zeta-potential (ZP) values close to -30 mV, and showed stability at different pHs, while maintaining their physicochemical properties mostly intact, presenting only a change in their superficial charge (ZP values), indicating their interaction. Both nanoformulations presented interaction with mucins, which anticipates good permeation and bioavailability for oral and topical administration. No cytotoxic effects were observed for lyophilized PLGA NPs encapsulating entacapone, in which 2-hydroxypropyl-ss-cyclodextrin (HP beta CD) was used as a cryoprotectant at 3% concentration (HP-PLGA@Ent), in human hepatocellular carcinoma (HepG2), human neuroblastoma (SH-SY5Y), or human epithelial colorectal adenocarcinoma (Caco-2) cell lines. Conversely, NLCs encapsulating entacapone (W-NLCs@Ent) presented cytotoxic effects on the HepG2 cell line, likely due to intracellular lipid accumulation or storage. Both nanoformulations maintained a COMT inhibition effect in HepG2 cells, using 3-BTD as the COMT probe. An increase of entacapone permeability in both monolayer and coculture models (Caco-2 and Caco-2/HT29-MTX, respectively) was observed for the developed nanoformulations. Overall, this work shows that encapsulated entacapone in different nanocarriers could be a stimulating alternative to solve entacapone setbacks, since they improve its physicochemical properties and permeability while still maintaining the COMT inhibitory activity.