Sustained release and efficacy of Kn2-7-loaded chitosan nanoparticles under low pH conditions.

Delivery of antimicrobial peptides to low-pH sites is a significant challenge, and results in reduced treatment efficacy for vaginal infections. Chitosan nanoparticles (CNPs) could be ideal vehicles for drugs to acidic pH environments and sustain their therapeutic effects. CNPs were synthesized using the ionic gelation technique and loaded with Kn2-7 peptide. The CNPs were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, high-resolution transmission and scanning electron microscopes. The stability and antibacterial effects of Kn2-7-loaded CNPs were evaluated at low and normal pH levels. The CNPs had a size distribution of 327–416 nm and a zeta potential of 9.61–23.9 mV. The size distribution (340.2–753.7 nm) and Zeta potential (15.9–67.7 mV) of CNPs changed after loading Kn2-7. The CNPs loading capacity and Kn2-7 entrapment efficiency were 35.6% and 78.3%, respectively. The Kn2-7-CNPs were not stable at low-pH and released Kn2-7 instantly; however, stabilization of Kn2-7-CNPs with poly (acrylic acid) (PAA) and tripolyphosphate (TPP) increased their stability and sustained Kn2-7 release at acidic pH. The Kn2-7-CNPs_1 mg/mL TPP-PAA inhibited the growth of Staphylococcus aureus at pH 3.8 better than the Kn2-7 alone. Therefore, the Kn2-7-CNPs_1mg/mL TPP-PAA could serve as a promising candidate for protecting and delivering drugs in low-pH environments.