Inhibition of MMP-9 by Use of Quaternary Ammonium Methacrylates

Matrix metalloproteinases (MMPs) bound to dentin have been thought to contribute to the progressive degradation of collagen fibrils in hybrid layers.  Inhibition of host-derived MMPs may slow the degradation of resin-dentin bonds over time.  Chlorhexidine (CHX) has been shown to have anti-MMP activity. However, CHX is water soluble which might compromise the long-term effect. Quaternary ammonium methacrylates (QAMs)are chemically analogous to CHX. Objectives:  To evaluate the effect of five commercially available QAMs on the enzymatic activity of MMP-9. Methods: Using recombinant human MMP-9 obtained from SensoLyte" Generic MMP Assay Kit (AnaSpec, CA, USA), 96-well plates were set up to measure the degree of inhibition of MMP-9 using thiopeptolide proprietary substrate, at two different concentrations, using appropriate kit controls.  After incubating the plates at 37°C for 2 hr, the developed color was measured at 412 nm. Data were analyzed using ANOVA/Tukey (p<0.05). Results: ANOVA showed significant differences among tested QAMs (p<0.001). QAMs inhibited MMP-9 activity between 16-82% (Table 1). These inhibitory results were confirmed by a different functional assay that assayed the total collagenolytic activity of demineralized dentin matrices. 

Table:  The mean percent inhibition and SD were:

ATA = 2-acryloxyethyltrimethyl ammoniumchloride; MCMS = methacryloylcholine methyl sulfate; METMAC = methacryloyloxyethyltrimethyl ammoniumchloride; DDAC = diallyldimethyl ammoniumchloride; MAPTAC = [3-(methacryloylamino)propyl]trimethyl ammoniumchloride.

Conclusion: QAMs inhibit the endogenous MMPs of dentin matrices in both their soluble and bound forms.  It remains to be determined if the incorporation of QAM into commercial dental adhesives will improve the durability of resin-dentin bonds in vitro and ultimately, in vivo.

  Supported, in part, by R01 DE015306-06 from the NIDCR to DP (P.I.) and by a grant to ATM (P.I) by the Academy of Finland.