Pheomelanin subunit non-destructive quantification by Raman spectroscopy and multivariate curve resolution-alternating least squares (MCR-ALS)

To date no direct methods are available for the subunit quantification of pheomelanin, sulfur-containing melanin form whose structure increases melanoma risk. Here we apply Raman spectroscopy combined with chemometrics (MCR-ALS method) to quantify benzothiazine (BT) and benzothiazole (BZ), constituent monomers pheomelanin. The spectra synthetic pheomelanins only composed BT or BZ were markedly different from those natural mixed BT-BZ, indicating necessity using a multivariate curve resolution method extract pure profiles these in complex samples. MCR-ALS correlation constraint was applied pheomelanized feathers 26 bird species predict BT-BZ concentrations. methodology able R2 ?= ?0.91 relative error 9%, range 100–1000 ?ng/mg. However, model did not perform well quantification. In addition, could retrieve profile associated keratin, major component (interference) feathers. deconvolution spectra, which predicts total pheomelanin content, MCR-ALS, can therefore provide complete determination at monomeric level. This represents non-destructive analytical subunits, opening door investigate differential cytotoxicity subunits high diversity biological samples, including melanoma.