Title : Modern non-invasive methods for in vivo assessment of skin
Abstract:
Recent innovations in spectroscopy and microscopy techniques have enable detailed chemical, structural, and functional analysis without the need for biopsy. The concept of optical biopsy has become a reality allowing clinicians and researchers to obtain molecular and morphological information from skin, preserving tissue integrity In vivo confocal Raman microspectroscopy has enabled detailed non-invasive chemical mapping of skin, quantifying key constituents such as water, natural moisturizing factors, lipids, and sweat components with micrometer depth resolution. Studies have demonstrated its value in assessing skin hydration, barrier function, and biochemical changes in conditions like atopic dermatitis and psoriasis. Furthermore, Raman microspectroscopy has been effectively used to monitor dermal penetration and permeation kinetics of topical products, providing critical insights into skin absorption pathways and formulation performance, thus facilitating skin penetration studies, reducing invasive procedures. Complementing spectroscopy, in vivo microscopy techniques provide high-resolution structural and functional insights. Reflectance confocal microscopy offers subcellular resolution imaging of skin morphology up to depths of 100–150 µm, enabling dynamic visualization of skin architecture and penetration pathways of substances. Line-field confocal optical coherence tomography extends imaging depth and contrast, allowing three-dimensional visualization of skin layers with subcellular resolution. Moreover, in vivo multiphoton microscopy, including two-photon and three-photon tomography combined with fluorescence lifetime imaging, enables dynamic functional analysis of skin properties by capturing fluorescence in multiple dimensions—spatial, spectral, temporal, and anisotropy—thus providing comprehensive data on skin physiology, disease states, and penetration of topically applied active ingredients. Such technologies facilitate a non-invasive optical biopsy approach that integrates in vivo chemical mapping with dynamic functional analysis, offering unprecedented capabilities for dermatological research, clinical diagnostics, and evaluation of topical therapies. We will highlight how these cutting-edge technologies are transforming skin assessment, improving our understanding of skin physiology, monitoring product efficacy, and advancing skin care without the drawbacks of invasive sampling.
