Defining the reactivity of nanoparticles to peptides through direct peptide reactivity assay (DPRA) using a high pressure liquid chromatography system with a diode array detector.

The possibility of inducing skin sensitization reactions following exposure to various chemicals can lead to skin diseases, and the evaluation of skin sensitivity to such substances is very important. However, as animal tests for skin sensitization are prohibited, the OECD Test Guideline 442 C was designated as part of an alternative testing method. Therefore, in this study, the reactivity of cysteine and lysine peptides to nanoparticle substrates was identified through HPLC-DAD analysis according to the skin sensitization animal replacement test method specified in the OECD Test Guideline 442 C. In this study, all criteria for skin sensitization experiments specified in OECD Test Guideline 442 C were satisfied. As a result of analyzing the disappearance rates of cysteine and lysine peptides for the five types of nanoparticle substrates (TiO2, CeO2, Co3O4, NiO, and Fe2O3) using the established analytical method, all were identified as positive. Therefore, our findings suggest that basic data from this technique can contribute to skin sensitization studies by providing the depletion percentage of cysteine and lysine peptides for nanoparticle materials that have not yet been tested for skin sensitization.

Pre-validation study of spectrophotometric direct peptide reactivity assay (Spectro-DPRA) as a modified in chemico skin sensitization test method.

Skin sensitization is induced when certain chemicals bind to skin proteins. Direct peptide reactivity assay (DPRA) has been adopted by the OECD as an alternative method to evaluate skin sensitization by assessing a substance's reaction to two model peptides. A modified spectrophotometric method, Spectro-DPRA, can evaluate skin sensitization, in a high throughput fashion, to obviate some limitations of DPRA. Pre-validation studies for Spectro-DPRA were conducted to determine transferability and proficiency, within- and between-laboratory reproducibility, and predictive ability based on GLP principles at three laboratories (AP, KTR, and KCL). All laboratories confirmed high (> 90%) concordance for evaluating the sensitivity induced by ten chemical substances. The concordance among the three tests performed by each laboratory was 90% for AP, 100% for KTR, and 100% for KCL. The mean accuracy of the laboratories was 93.3% [compared to the standard operating procedure (SOP)]. The reproducibility among the three laboratories was as high as 86.7%; the accuracy was 86.7% for AP, 100% for KTR, and 86.7% for KCL (compared to the SOP). An additional 54 substances were assessed in 3 separate labs to verify the prediction rate. Based on the result, 29 out of 33 substances were classified as sensitizers, and 19 out of 21 identified as non-sensitizers; the corresponding sensitivity, specificity, and accuracy values were 87.9%, 90.5%, and 88.9%, respectively. These findings indicate that the Spectro-DPRA can address the molecular initiating event with improved predictability and reproducibility, while saving time and cost compared to DPRA or ADRA.

Sulfone-mediated syntheses of crocetin derivatives: regioselectivity of highly functionalized building blocks.

New C5 sulfone building blocks containing a masked polar end group have been devised for the efficient synthesis of carotenoids with polar termini. Chemoselectivity or the regiochemical issue of the highly functionalized units has been carefully addressed depending on the soft or hard nature of electrophiles. These building blocks have been successfully applied to the syntheses of crocetin derivatives, crocetin dial and the novel crocetin dinitrile.