Sensitizer contained in heat-decomposed dye

Recently a new resorbable P(LA/CL) monofilament suture made of L-lactide and epsilon-caprolactone was developed. The sensitization test was carried out using a guinea pig maximization test according to the Japanese Guidelines. As a result of this test, it was revealed that the methanol extract of P(LA/CL) suture contains a skin sensitizer. It was suggested that the D&C Violet No. 2 contained in P(LA/CL) sutures is decomposed during the melt-spinning process and that the decomposed dye induces skin sensitization. To characterize the sensitizer (the decomposed dye) it was separated and collected by HPLC. To determine the molecular formula of the sensitizer, MS, IR, and NMR spectra were obtained. The molecular weight of the sensitizer was estimated as 240 by measuring the MS. Considering the chemical structure of the dye and the molecular weights, it was determined that the sensitizer was 1,4-dihydroxyanthraquinone (quinizarin). The D&C Violet No. 2 contained in P(LA/CL) sutures was decomposed by the melt-spinning procedure to form quinizarin, one type of anthraquinone dye, and the sensitizer was identified to be, indeed, quinizarin. To evaluate the sensitizing potential of quinizarin, we tested skin sensitization using the maximization test method. Quinizarin induced skin sensitization in guinea pigs, and the minimum sensitizing concentration was approximately 100 ppm. The concentration of quinizarin contained in the P(LA/CL) suture was 1-5 ppm, a value that is lower than the minimum sensitizing concentration of quinizarin. This suggests that P(LA/CL) suture has a low risk with regard to contact dermatitis.