Apatite formation on collagen fibrils in the presence of polyacrylic acid.

Recently, we reported the formation of bone-like apatite on collagen fibrils by biomimetic method. Compounds containing carboxyl moieties are believed to be effective in the formation of apatite. Polyacrylic acid [-CH2CH(COOH)-]n (PAAc) is widely used in dentistry. In the present study, the effect of PAAc in the formation of apatite from revised simulated body fluid (R-SBF) on collagen fibrils was studied. Two different experimental approaches were tried to study the effect of PAAc present in the collagen and in the R-SBF solution. In the first, collagen gel was soaked with 1 mg/ml PAAc (molecular weights 25000 and 100000) for the time intervals of 30 min and 6 h. The gels were then dried in air and incubated in R-SBF. Characterization of the precipitates formed on the collagen fibrils in gel showed that the formation of apatite was inhibited when soaked in PAAc for 6 h. In the second experiment, when PAAc (0.1 and 1.0 mg/ml) was mixed with R-SBF the microstructure of the precipitates formed on collagen fibrils was affected partially. Hence, it is confirmed that the presence of PAAc in the biomimetic environment of collagen affects the mineralization of apatite.