The optical properties of mouse skin in the visible and near infrared spectral regions

• We present μa, μ′s, μ′t and δ of albino and pigmented mice skin from both genders, from 400 to 1400 nm.
• Dense connective tissues are more abundant in males and present strong scattering.
• Males present stronger absorption by heme-proteins indicating higher blood content.
• Albino mice present more intense infrared absorption due to higher water content.
• Melanin in depilated pigmented mouse skin is irrelevant for light absorption.

Visible and near-infrared radiation is now widely employed in health science and technology. Pre-clinical trials are still essential to allow appropriate translation of optical methods into clinical practice. Our results stress the importance of considering the mouse strain and gender when planning pre-clinical experiments that depend on light–skin interactions. Here, we evaluated the optical properties of depilated albino and pigmented mouse skin using reproducible methods to determine parameters that have wide applicability in biomedical optics. Light penetration depth (δ), absorption (μa), reduced scattering (μ′s) and reduced attenuation (μ′t) coefficients were calculated using the Kubelka–Munk model of photon transport and spectrophotometric measurements. Within a broad wavelength coverage (400–1400 nm), the main optical tissue interactions of visible and near infrared radiation could be inferred. Histological analysis was performed to correlate the findings with tissue composition and structure. Disperse melanin granules present in depilated pigmented mouse skin were shown to be irrelevant for light absorption. Gender mostly affected optical properties in the visible range due to variations in blood and abundance of dense connective tissue. On the other hand, mouse strains could produce more variations in the hydration level of skin, leading to changes in absorption in the infrared spectral region. A spectral region of minimal light attenuation, commonly referred as the “optical window”, was observed between 600 and 1350 nm.

Light-based technologies have been widely employed in health sciences. Since skin is the most common optical barrier in non-invasive techniques, its optical properties must be very well known. Our study investigated the light interaction with skin of bother genders from albino and pigmented strains. Our findings show a band of minimal light attenuation, referred as the “optical window”, between 600 and 1350 nm. Heme-containing proteins and water are main absorbing components in mouse skin, while melanin and fatty acids are minimally important. Gender mostly affects mouse skin optical properties in the visible range due to variations in blood and dense connective tissue abundance, while strains can introduce variations in the hydration level of skin, leading to absorption divergences in the infrared spectral region.Figure optionsDownload as PowerPoint slide