An analytical technique for measuring protein carbonyl in the stratum corneum using surface plasmon resonance

Protein carbonyl groups in the stratum corneum may be used as a biomarker for skin photo-stress. To evaluate the relationship between the protein carbonyl to total protein (TP) ratio (carbonylation ratio) and skin photo-stress, the authors established a methodology by which protein carbonyl can be easily and highly sensitively analysed using an optical technique based on surface plasmon resonance (SPR). To collect the stratum corneum, tape stripping was employed. Firstly, the protein carbonyl was reacted with 2,4-dinitrobenzenesulfonic acid dihydrate, and the quantity of dinitrophenylated (DNP)-protein carbonyl was determined using an anti-dinitrophenyl (anti-DNP) antibody. The mass of DNP-protein carbonyl was measured using SPR. A truncated sampling-reporting cycle of <5 min allowed speedy reporting of DNP-protein carbonyl levels. A significant difference was observed in the protein carbonyl/TP ratio (carbonylation ratio) between a sun-protected area (mid-ventral arm) and a sun-exposed area (upper cheek, P < 0.05). Additionally, the carbonylation ratio of the sun-exposed area showed a higher value than that of the sun-protected area. It was suggested that the carbonylation ratio might be a useful index of skin photo-stress.