Preparation, optimization, characterization and antimicrobial activity of chitosan and calcium nanoparticles loaded with streptomyces rimosus extracted compounds as drug delivery systems

Anotace: The present study aims to search for a nano-delivery system that enables access of antimicrobial compounds to the targeting site of the microbial pathogens. To achieve this objective, the antimicrobial compounds extracted from the local isolate Streptomyces rimosus were loaded on chitosan (CS) and calcium phosphate (CaP) nanoparticles (NPs) to facilitate drug delivery to some species of bacteria (Escherichia coli ATCC25922, Staphylococcus aureus ATCC25923 and Bacillus cereus ATCC6633) and the yeast Candida albicans ATCC10231. The best incubation period for the production of antifungal and antibacterial compounds, pH, temperature, carbon sources and nitrogen sources were around the third day, 7.0, 30°C, starch and potassium nitrate, respectively. The extracted compounds were identified using gas chromatography-mass spectrometry (GC-MS) analysis which revealed to the identification of nine antimicrobial organic acids. The prepared NPs were characterized using transmission electron microscopy (TEM) and Zeta potential analyser. Results showed those chitosan nanoparticles (CSNPs) were spherical shaped NPs with an average size ≈22 ± 2 nm. The CSNPs loaded with the antimicrobial molecule’s diameter was ranged from 55 upto 100 nm. Calcium phosphates nanoparticles (CaPNPs) were also spherical shaped NPs with diameter range from 70 to 95 nm. Loading of antimicrobial compounds onto CaPNPs made them appeared in rod shape with width varying from 14 to 27 nm and length from 274 to 397 nm. The synthesized NPs showed negative values confirming their high dispersity and long-term stability. The tested strains were resistant to solo NPs; but the loaded NPs with the extracted antimicrobial compounds, particularly the CaPNPs, augmented the potency of the isolated antimicrobial compounds, with emergence of differential antimicrobial activity. The activity of the NPs-bound antimicrobial compounds was more evident against bacteria than fungi, Gram-positive bacteria than Gram-negative bacteria and against B. cereus than S. aureus.