Rapid fabrication of nitric oxide releasing hydroxyapatite microspheres using liquid nitrogen as an antibiotic-free alternative.

Bacterial infections are a major global health challenge. Although antibiotics are the dominant therapeutic approach, the problem of resistance resulting from their widespread use has led to an urgent need to develop new, safe, and effective alternative antimicrobial strategies. In this work, antimicrobial SNAP-HA microspheres with controlled release of NO were successfully prepared by loading S-nitroso-N-acetyl penicillamine (SNAP) in hydroxyapatite (HA). The loading of SNAP in SNAP-HA microspheres ranged from 1.05 % to 16.42 %. The NO release from SNAP-HA microspheres was measured by chemiluminescence, and the longest NO release time reached ∼66 h 1H NMR also characterized the decomposition products of SNAP. In addition, the structure, thermal properties, and morphology of SNAP-HA microspheres were fully characterized. SNAP was present in HA microspheres in the amorphous form. In antibacterial studies, the SNAP-HA microspheres were able to reach 100 % of the optimal antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). SNAP-HA microspheres are antimicrobial by releasing NO gas, which does not stimulate the development of drug-resistant strains of bacteria and is expected to be a new alternative antimicrobial product.