Assessment of the elicitation response in subjects weakly sensitized top-phenylenediamine

Development of photo-amino acid derivative reactivity assay: a novel in chemico alternative method for predicting photoallergy

Photoallergy test of cosmetics and several types of pharmaceutical substances is often necessary for obtaining approval from authorities. However, there are no official test guidelines for photoallergy evaluation. Therefore, we tried to establish a photoallergy test by utilizing an in chemico alternative sensitization method, amino acid derivative reactivity assay (ADRA). To determine the criteria for judging the photoallergy potential, photo-ADRA with or without photoirradiation was performed using 60 photoallergenic chemicals, and cysteine and lysine derivatives were detected using high-performance liquid chromatography either by absorbance or fluorescence measurement. The accuracy of prediction was 81.4% (48 of 59) and 80.0% (48 of 60) using the absorbance and fluorescence methods, respectively. However, as chemicals can breakdown into multiple chemicals during photoirradiation, the absorbance method often cannot perform accurate detection due to co-elution, whereas the fluorescence method can do this due to lack of co-elution. Moreover, all eight chemicals that were found to be negative or false-positive for photoirritation in the 3T3 neutral red uptake phototoxicity test were confirmed as positive for photoallergy using this method. Furthermore, we prepared three types of pseudo-mixtures where we added one photoallergen along with five nonphotoallergens and performed the photo-ADRA by the ultraviolet and fluorescence methods. The result of the fluorescence method was almost the same as that obtained with the use of a single photoallergen and hence the outcome was not affected by the mixture. Thus, this study not only showed a method of evaluating the photoallergy potential of a single chemical but also a mixture, making it useful as an in chemico photoallergy alternative test.

One-pot synthesis of active copper-containing carbon dots with laccase-like activities

Herein, an effective strategy for designing a new type of nanozyme, blue fluorescent laccase mimics, is reported. Active copper-containing carbon dots (Cu-CDs) were synthesized through a simple, nontoxic and one-pot hydrothermal method, which showed favorable photoluminescence properties and good photostability under high-salt conditions or in a broad pH range (3.0-13.5). The Cu-CDs possessed intrinsic laccase-like activities and could catalyze the oxidation of the laccase substrate p-phenylenediamine (PPD) to produce a typical color change from colorless to brown. Poly(methacrylic acid sodium salt) (PMAA) not only was used as the carbon source and reducing agent, but also provided carboxyl groups to assist flocculation between Cu-CDs and polyacrylamide, which facilitated the removal of PPD. Importantly, the intrinsic fluorescence of the as-prepared Cu-CDs could indicate the presence of hydroquinone, one of the substrates of laccases, based on laccase mimics and fluorescence quenching.

Cross-elicitation responses to 2-methoxymethyl-p-phenylenediamine under hair dye use conditions in p-phenylenediamine-allergic individuals

BACKGROUND

The factors influencing elicitation responses in individuals allergic to p-phenylenediamine (PPD) in hair dyes are not well understood.

OBJECTIVES

Investigation of the elicitation response to the new, less-sensitizing PPD alternative 2-methoxymethyl-p-phenylenediamine (ME-PPD) under simulated hair dye use conditions.

METHODS

The cross-elicitation response to ME-PPD (2% in a hair dye test product for 30 min on forearm then rinsing) was analysed at days 2 and 3 in 30 PPD-allergic individuals with diagnostic patch test grades +, ++ or +++ according to the classification of the International Contact Dermatitis Research Group.

RESULTS

Cross-reactivity to the ME-PPD-containing hair dye test product was elicited in nine of 30 subjects (30%), while 70% were negative. Cross-reactivity was elicited in two of four cases with grade +++, three of 10 with grade ++ and four of 16 with grade +. Under identical conditions, PPD was previously found to elicit a response in 21 of 27 PPD-allergic individuals. In 18 of these 21 individuals, either the strength of the cross-elicitation response to ME-PPD was decreased or no response occurred.

CONCLUSIONS

Under simulated hair dye use conditions, a significantly lower degree of cross-elicitation to ME-PPD (30%) was observed than previously reported for PPD (32 of 38, 84%). Additionally, a decreased cross-elicitation strength was observed across all three patch test grades, likely reflecting the reduced skin-sensitization properties of ME-PPD. Consequently, careful dermatological evaluation is required to assess cross-reactivity to ME-PPD in patients allergic to hair dyes.