Stability of collagen in the presence of 3,4-dihydroxyphenylalanine (DOPA)

Many cross-linking agents for collagen are available with varying levels of toxicity and some are in use in biomedical implants of collagen. L-DOPA (3,4-dihydroxyphenylalanine), a neurotransmitter, is a naturally present compound in the living system and is the target in therapeutic strategy of Parkinson's disease. This work reports the effect of the neurotransmitter DOPA on the stability of collagen solution using circular dichroism (CD), fluorescence spectroscopy, melting and shrinkage temperature. Collagen solution treated with various concentrations of DOPA ranging from 10(-2) to 10(-5) M was analyzed using fluorescence and CID spectra. When collagen was treated with DOPA, the intensity of emission was found to increase indicating the possibility of interaction of DOPA with collagen and maximum emission intensity was observed between 10(-3) and 10(-4) M for L-DOPA and DL-DOPA, respectively. CID studies show possible aggregation of collagen even in the presence of low concentrations of DOPA. The shrinkage temperature of DOPA treated collagen fibres was experimentally determined to be 69 +/- 4 degrees C. The melting temperature of DOPA cross linked collagen solution also exhibited a significant increase from 35 to 40 degrees C (+/- 0.1) (P < 0.05). The experimental results suggest that the optimum concentration for cross linking collagen with DOPA ranges between 10(-3) and 10(-4) M. Thus, DOPA may be a useful stabilizing agent for collagen for biomedical applications. (c) 2009 Elsevier B.V. All rights reserved.