posted on 2021-08-31, 17:14authored byRita M. Pinto, Claudia Monteiro, Sofia A. Costa Lima, Susana Casal, Patrick Van Dijck, M. Cristina L. Martins, Cláudia Nunes, Salette Reis
Bacterial biofilms
are a major health concern, mainly due to their
contribution to increased bacterial resistance to well-known antibiotics.
The conventional treatment of biofilms represents a challenge, and
frequently, eradication is not achieved with long-lasting administration
of antibiotics. In this context, the present work proposes an innovative
therapeutic approach that is focused on the encapsulation of N-acetyl-l-cysteine (NAC) into lipid nanoparticles
(LNPs) functionalized with d-amino acids to target and disrupt
bacterial biofilms. The optimized formulations presented a mean hydrodynamic
diameter around 200 nm, a low polydispersity index, and a high loading
capacity. These formulations were stable under storage conditions
up to 6 months. In vitro biocompatibility studies
showed a low cytotoxicity effect in fibroblasts and a low hemolytic
activity in human red blood cells. Nevertheless, unloaded LNPs showed
a higher hemolytic potential than NAC-loaded LNPs, which suggests
a safer profile of the latter. The in vitro antibiofilm
efficacy of the developed formulations was tested against Staphylococcus epidermidis (Gram-positive) and Pseudomonas aeruginosa (Gram-negative) mature biofilms.
The results showed that the NAC-loaded LNPs were ineffective against S. epidermidis biofilms, while a significant reduction
of biofilm biomass and bacterial viability in P. aeruginosa biofilms were observed. In a more complex therapeutic approach,
the LNPs were further combined with moxifloxacin, revealing a beneficial
effect between the LNPs and the antibiotic against P. aeruginosa biofilms. Both alone and in combination
with moxifloxacin, unloaded and NAC-loaded LNPs functionalized with d-amino acids showed a great potential to reduce bacterial viability,
with no significant differences in the presence or absence of NAC.
However, the presence of NAC in NAC-loaded functionalized LNPs shows
a safer profile than the unloaded LNPs, which is beneficial for an in vivo application. Overall, the developed formulations
present a potential therapeutic approach against P.
aeruginosa biofilms, alone or in combination with
antibiotics.