Chloride ion-driven transformation from Ag3PO4 to AgCl on the hydroxyapatite support and its dual antibacterial effect against Escherichia coli under visible light irradiation

Synthesis of M-Ag3PO4, (M = Se, Ag, Ta) Nanoparticles and Their Antibacterial and Cytotoxicity Study

Silver Phosphate, Ag3PO4, being a highly capable clinical molecule, an ultrasonic method was employed to synthesize the M-Ag3PO4, (M = Se, Ag, Ta) nanoparticles which were evaluated for antibacterial and cytotoxicity activities post-characterization. Escherichia coli and Staphylococcus aureus were used for antibacterial testing and the effects of sonication on bacterial growth with sub-MIC values of M-Ag3PO4 nanoparticles were examined. The effect of M-Ag3PO4 nanoparticles on human colorectal carcinoma cells (HCT-116) and human cervical carcinoma cells (HeLa cells) was examined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay and DAPI (4′,6-diamidino-2-phenylindole) staining. Additionally, we analyzed the effect of nanoparticles on normal and non-cancerous human embryonic kidney cells (HEK-293). Ag-Ag3PO4 exhibited enhanced antibacterial activity followed by Ta-Ag3PO4, Ag3PO4, and Se-Ag3PO4 nanoparticles against E. coli. Whereas the order of antibacterial activity against Staphylococcus aureus was Ag3PO4 > Ag-Ag3PO4 > Ta-Ag3PO4 > Se-Ag3PO4, respectively. Percentage inhibition of E. coli was 98.27, 74.38, 100, and 94.2%, while percentage inhibition of S. aureus was 25.53, 80.28, 99.36, and 20.22% after treatment with Ag3PO4, Se-Ag3PO4, Ag-Ag3PO4, and Ta-Ag3PO4, respectively. The MTT assay shows a significant decline in the cell viability after treating with M-Ag3PO4 nanoparticles. The IC50 values for Ag3PO4, Se-Ag3PO4, Ag-Ag3PO4, and Ta-Ag3PO4 on HCT-116 were 39.44, 28.33, 60.24, 58.34 µg/mL; whereas for HeLa cells, they were 65.25, 61.27, 75.52, 72.82 µg/mL, respectively. M-Ag3PO4 nanoparticles did not inhibit HEK-293 cells. Apoptotic assay revealed that the numbers of DAPI stained cells were significantly lower in the M-Ag3PO4-treated cells versus control.

Silver-doped hydroxyapatite for formaldehyde determination by digital-image colorimetry

Silver-hydroxyapatite material (Ag-HAP) was first proposed as material for trace-level formaldehyde detection based on Tollens' reaction on the material surface. By using this Ag-HAP material, the chemical reduction caused by formaldehyde occurred directly on the solid surface. The material color changed from off-white to the yellow or brown of silver nanoparticles depending on the formaldehyde concentration. The color intensity of the materials was measured from their smartphone digital images using Image-J software. The effect of silver ion concentration, sodium hydroxide concentration, contact time, and sample volume on formaldehyde detection were investigated. Under optimized conditions, the working range for formaldehyde detection was determined to be 15 to 200 μg L^-1. The method was successfully applied to detect trace formaldehyde in water samples and a recovery of 86 to 111%, with an RSD of 3 to 8%, was observed. With a lowest concentration for the detection of 15 μg L^-1 and good accuracy and precision, the method showed promise for formaldehyde determination.