Antimicrobial potential of different bee product-loaded carboxymethyl chitosan nanoparticles against...

Antimicrobial resistance is one of the major public health threats facing humanity. Hence, the current investigation aimed to develop alternative therapeutic strategies by integrating apitherapy with biopolymer-based nanotechnology to combat multidrug-resistant (MDR) microbial pathogens.

Out of 100 clinical microbial isolates, 29 highly MDR clinical pathogens from different infections, including Gram-negative and Gram-positive bacteria, as well as fluconazole-resistant Candida spp., were selected for the study. Three bee products (Turkish propolis extract (P), Egyptian honey (H), and Egyptian royal jelly (RJ)) were used, and their polyphenolic contents were determined via HPLC analysis. These bee products were encapsulated within carboxymethyl chitosan nanoparticles (CMC NPs). The resulting nano-formulations, namely Carboxymethyl chitosan-Propolis extract nanoparticles (CMC-P NPs), Carboxymethyl chitosan-Honey nanoparticles (CMC-H NPs), and Carboxymethyl chitosan-Royal Jelly nanoparticles (CMC-RJ NPs), were characterized in terms of particle size, surface charge, and chemical composition. Their antimicrobial activity and preliminary cytocompatibility were evaluated using standard microbiological assays and the MTT assay, respectively.

HPLC analysis confirmed the presence of diverse polyphenolic compounds in the bee products. The highest concentrations were detected in the ethanolic extract of propolis (EEP) (51.0-40993 µg/g), followed by honey (1.06-1591.16 µg/g) and royal jelly (0.53-2796.37 µg/g). Among the nano-formulations, CMC-P NPs emerged as the most potent formulation (size: 100.7 nm, zeta potential: -70 mV), showing significant bactericidal activity (P < 0.05) against all MDR isolates. Notably, CMC-P NPs exhibited inhibition zones (17.67-31.33 mm) and MIC values (0.019-1.25 mg/mL) that were superior to standard antibiotic controls. CMC-H NPs and CMC-RJ NPs exhibited variable antimicrobial effects, depending on the pathogen and the encapsulated bee product. Indeed, all three nano-formulations demonstrated strong antimicrobial action against highly resistant Klebsiella pneumoniae and Klebsiella ozaenae. Further, MTT assay results confirmed the preliminary biocompatibility of the nanostructures, showing no significant toxicity toward RPE1 cells.

Encapsulation of bee products within CMC NPs significantly enhances their antimicrobial performance against a wide range of MDR clinical pathogens. The developed nano-formulations exhibited suitable physicochemical properties, potent antimicrobial activity, and promising preliminary biocompatibility, supporting their potential as safe and effective antimicrobial candidates for further preclinical investigation.