Design of novel antimicrobial nanocarriers against antibiotic resistant pathogens based on anti-quorum sensing signaling molecules

Trabajo presentado a XXXIX Reunión Bienal de la Real Sociedad Española de Química, celebrada en Zaragoza del 25 al 29 de junio de 2023.

Antibiotic resistance is a serious global public health threat, particularly important in the treatment of lower respiratory tract infections (LRTI)[1]. Its clinical relevance has increased during the ongoing COVID-19 pandemic due to secondary bacterial infections in severe hospitalized cases requiring mechanical ventilation or assisted respiration[2]. Antibiotic resistance induces therapeutic failure on respiratory infectious diseases, which aims urgent development of innovative antimicrobials alternative to conventional antibiotics[3]. A main bacterial pathogen causing LRTI is Haemophilus influenzae, resistant to ampicillin, which is especially relevant in chronic obstructive pulmonary disorder (COPD) and forms biofilms that favors chronic infection and antibiotic resistance[4]. Nowadays there are no anti-biofilm therapies available against H. influenzae. Conversely, the formation, maturation and dispersion of biofilms is regulated by intra- and intercellular signaling systems. Autoinducers play an important role in the intercellular signaling, or quorum sensing. In the case of H. influenzae, autoinducer-2 (AI.2, dihydroxypentanedione-DPD) mediated signaling plays a role in biofilm formation[5]. Based on these needs and evidence, polymeric nanocarriers based on an AI-2 autoinducer analog (trans-2-nonenal) have been developed. Polymeric nanoparticles based on the widely used poly-lactic-co-glycolic-acid (PLGA) have been designed and optimized enclosing trans-2-nonenal as active molecule by simple emulsion-solvent evaporation method. Different parameters of the synthetic procedure have been studied, such as drug/polymer ratio, volume, and composition of aqueous and organic phases, as well as sonication and evaporation times. The physico-chemical properties of the nanocarriers have been analyzed through dynamic light scattering, differential scanning calorimetry and scanning electron microscopy. Encapsulation efficiency and controlled drug release kinetics at 4ºC, RT and 37ºC have been determined by gas chromatography. Once the system was optimized, in vitro efficacy tests were performed against H. influenzae biofilms. Under optimal conditions, monodisperse, stable and reproducible nanoparticles with an average hydrodynamic diameter of 200 nm were obtained. Within the kinetic studies, it was determined that 85% of the drug is progressively released over the first 24 h. In vitro experiments showed that the minimum inhibitory concentration was 50 µg/ml. Also, these nanoparticles were found to be effective in the eradication of preformed H. influenzae biofilms.