The inhibitory effects of silver diamine fluorides on cysteine cathepsins

Abstract

Objective: The expression of cysteine cathepsins in human carious dentin suggests that this enzyme contributes to the collagen degradation in caries progress. This study investigated whether silver diamine fluoride (SDF) inhibited the activity of cysteine cathepsins. Method: Three commercial SDF solutions with concentrations at 38%, 30% and 12% were studied. This study prepared two sodium fluoride solutions with the same fluoride ion (F-) concentrations as the 38% and 12% SDF solutions, and 2 silver nitrate solutions with the same silver ion (Ag+) concentrations as the 38% and 12% SDF solutions. Five samples of each experimental solution were used to study their inhibitory effect on two cathepsins, cathepsin B and cathepsin K, using cathepsin assay kits. Control solution containing assay buffer and cathepsin dilution was used to calculate the percentage inhibition (difference between the mean readings of the test and the control groups divided by that of the control group).

Result: The percentage inhibition of 38%, 30% and 12% SDF on cathepsin B were 92.0%, 91.5% and 90.3%, respectively (p<0.001); on cathepsin K were 80.6%, 78.5% and 77.9%, respectively (p<0.001). Two-way ANOVA demonstrated that Ag+ and F- had interaction inhibitory effect in both cathepsin B and K. Besides, Ag+ was significantly more effective in inhibition of cathepsins B and K activity than F-(p<0.01).

Conclusion: Higher concentrations of SDF solution have greater inhibitory effect on cathepsins B and K. Furthermore, Ag+ is more effective than F- in inhibiting the activity of cathepsins B and K.

This abstract is based on research that was funded entirely or partially by an outside source: This study was supported by the NSFC/RGC Joint Research Scheme (Grant No. N_HKU 776/10 and NSFC No.81061160511).