D-Squame tapes were applied to the skin areas of interest in a single female subject with long hair before hair treatment, and at different time points after application of shampoo and conditioner. The shampoo and conditioner were rinsed off normally during a regular shower and the head was allowed to dry for 20 mintues.
D-squame tapes were applied and collected on the skin areas of interest after 30 minutes, 1 hour, 2 hours for the shampoo and conditioner. D-squame tapes were applied to the skin areas of interest in the same female subject 3 days later before hair treatment, and after using a leave-in styling product. D-squame tapes were applied and collected on the skin areas of interest after 30 minutes, 1 hour, 2 hours, and 4 hours for the leave-in styling product. D-squame tapes were then scanned by ATR-FTIR imaging spectroscopy to assess hair product deposition on the specific skin areas at various time points (Figure 1).
The top selling shampoo, conditioner, and styling cream in U.S. salons (based on Kline PRO database Q1-Q3 2018) was used for the study. FTIR spectra were recorded on the shampoo, conditioner, and styling product to identify infrared (IR) markers that could be used to follow specifically hair product deposition on the skin. The IR markers were in a spectral area with almost no skin contribution in this spectral area (Figure 2, Figure 3).
To visualize the presence of hair products on specific skin areas before and after treatment, we generated specific ATR-FTIR images from skin cells extracted by the D-squame tapes. There is absence (dark blue) of hair product residue before applying shampoo/conditioner or the leave-in styling product. Up to 2 hours after using shampoo and conditioner, there is significant (red, yellow, green) hair product deposition remaining on the scalp (Figure 4), forehead, cheek, and upper back (Figure 5). Up to 4 hours after using the leave-in styling product, there is significant (red, yellow, green) hair product deposition remaining on the scalp (Figure 6), forehead, cheek, and upper back (Figure 7).
All the FTIR images were acquired with a Spotlight 400 imaging system (Perkin Elmer Instruments, USA) using a MCT (mercury-cadmium-telluride) focal plane array detector. FTIR Images were collected in reflective mode with an ATR imaging accessory at a spectral resolution of 4 cm-1 in the mid-infrared (MIR) region between 4000 and 750 cm-1 with a spatial resolution of 6.25 x 6.25 μm and sample size of 300 x 300 μm. These conditions allowed us to obtain good quality spectra with acceptable recording time (7 minutes per hyperspectral image).
This FTIR Imaging System produces hyperspectral images that can provide maps showing the co-localization of specific molecular components or spectroscopic parameters. These images are generated with false colors where the red represent highest values and blue lowest values for each parameter investigated. These images were used to visualize the deposition and the retention of rinse-off and leave-in hair products on the skin surfaces at specific locations.
All the FTIR spectra and FTIR images presented in this study were processed using GRAMS/AI (Thermo Fisher Scientific) or ISys software from Spectral Dimensions (Olney, MD). Us-