The Effect Of Dopamine On The Activity Of Matrix Metalloproteinases And Degradation Of Dentin Collagen

Objective To investigate the inhibition effect of dopamine on the activity of matrix metalloproteinases(MMP) and the effect of dopamine on degradation of dentin collagen for its potential use in caries treatment and dentin adhesive.Methods 2mg/ml dopamine+100u/ml highly purified collagenase type Ⅶfrom clostridium histolyticum was served as the experimental group, deionized water+100u/ml highly purified collagenase type Ⅶfrom clostridium histolyticumwas served as the negative control group, 2mg/ml dopamine+ deionized water was served as the positive control group1, 2% chlorhexidine+100u/ml highly purified collagenase type Ⅶ from clostridium histolyticum was served as the positive control group2, the mixture volume ratio of the two ingredients in every group was 1:9. After 15 minutes, the enzyme activity of each sample was tested by MMP activity colerimetric quantitative detection kits, and the test was repeated 5 times in each group. In the experiment of collagen degradation, the dentin slices were demineralized with 37% phosphoric acid for 1 min. In sequence, 2 dentine slices observation of morphology, and the remaining 30 dentine slices were randomly divided into three groups(n=10) according to random number table: the negative control ones were stored in 100 μl deionized water and 900 μl collagenase(7 days, 37 ℃), the positive control ones were stored in 100 μl chlorhexidine and 900 μl collagenase(7 days, 37 ℃) and the experimental specimens were stored in 100 μl dopamine and 900 μl collagenase(7 days, 37 ℃). The degraded collagen was investigated by assaying hydroxyproline. The framework of collagen was evaluated with field emission scanning electron microscope(FE-SEM). To evaluate the effect of dopamine on morphology of dehydrated dentin collagen matrix, a dentin slice was divided into four equal parts and demineralized with 37% phosphoric acid for 30 seconds, and followed by(1) immersing into deionized water for 5 minutes without dry before SEM abservation;(2) immersing into dopamine solution for 5 minutes, without dry before SEM abservation;(3) immersing into deionized water, for 5 minutes,then dried with compressed air;(4) immersing into dopamine solution for 5 minutes dried with compressed air. All the samples were observed with SEM.Results The statistical results showed that the MMP activity and the amount of degraded collagen of the negative control group[(0.089±0.011) μmol·min-1 and(2836.88±200.71) μg/cm2] were significantly higher than those of the positive control group[(0.038±0.006) μmol·min-1 and(1288.47±171.78) μg/cm2] and the experimental group[(0.030±0.009) μmol·min-1 and(1388.93±254.80) μg/cm2](P<0.05). SEM observation indicated that the structural integrity of the collagen network on dentin still existed in experiment samples and positive control groups, however, collagen fibrils were destructed and the structural integrity disappeared in the negative control groups. The demineralized dentin collagen matrix preconditioned with dopamine could maintain its original morphology regardless of the surface moisture conditions or dry.Conclusions Dopamine can inhibit MMP activity, reduce the degradation of demineralized dentin collagen matrix, and contribute to maintain the morphology of demineralized dentin collagen matrix.