Real-Time In Vivo Human Skin Testing Using a Handheld Fourier Transform Infrared Spectrometer with a Three-Bounce Two-Pass Attenuated Total Reflection Interface

Attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FT-IR) is used to characterize a vast array of materials at the molecular level in various industry types. Here we compare the performance of a portable spectrometer with a novel three-bounce-two-pass (3B2P) ATR scanning interface to the same device with a standard one-bounce (1B) ATR, and to a benchtop spectrometer with a 10-bounce (10B) ATR, in ideal sample-interface conditions and an applied dermatological study setting. In both application settings, the benchtop 10B ATR interface showed the highest signal-to-noise ratio (SNR), however, the novel 3B2P produced a six-fold increase in the sensitivity of the portable spectrometer when analyzing isopropanol and showed the greatest consistency of SNR of all devices when analyzing isopropanol and in vivo skin samples. Spectral data were sourced from a recently undertaken dermatological study involving a cohort of 180 healthy, full-term babies, using both 1B and 3B2P interfaces. Use of the 3B2P interface resulted in a 55% greater successful high-quality spectrum collection rate, compared to the 1B, and showed significantly superior SNR at both observed study time points, i.e., birth (1B: 68.37; 3B2P: 77.37), and at four weeks (1B: 74.53; 3B2P: 80.22). The utility of ATR FT-IR spectrometers as a dermatological clinical tool was also exemplified here, by quantifying the moisture level of newborn skin. By gathering rich spectroscopic data on the molecular structure of the skin, this technique holds great promise for the quantification of skin disease-specific biomarkers.