Depth-sensitive Raman spectroscopy for skin wound evaluation in rodents

Abstract

Raman spectroscopy has demonstrated great potential for skin wound assessment. Given that biochemical changes in wound healing is depth dependent as the skin is a layered structure, depth sensitive Raman spectroscopy could enhance the power of Raman spectroscopy in this application. Considering the critical importance of rodent studies in the field of skin wound assessment, it is necessary to develop and validate a system that can perform depth sensitive measurements in rat skin with a proper target depth range. In this manuscript, we report the design, optimization and evaluation of a new snapshot depth-sensitive Raman instrument for rat skin measurements. The optical design and optimization process are presented first. The depth sensitive measurement performance is characterized on both ex vivo porcine skin with a gradient of layer thickness and ex vivo rat skin samples with wounds. The statistical analysis of the measured Raman spectra demonstrates the feasibility of differentiation between the wound edge and healthy skin. Moreover, the accuracy of classification improves monotonically as more data from new depths are used, which implies that each depth offers additional information useful for classification. This instrument demonstrates the ability to perform snapshot depth sensitive Raman measurements from rat skin, which paves the way towards in vivo preclinical studies of rat skin wounds.

Kinetics of optical clearing of human skin studiedin vivousing portable Raman spectroscopy

“…Figures 2(a)-(d) shows the Raman spectra in the fingerprint region of human skin (wrist sites), glycerol, Omnipaque, and PEG 300, respectively. The many Raman peaks emitted from the skin tissue correspond to vibrational modes of different skin constituents [21]. The shape of the skin Raman spectrum in this research resembles that of Villaret [22].…”

Towards non-invasive monitoring of non-melanoma skin cancer using spatially offset Raman spectroscopy

“…In SORS measurements, the excitation and collection signals on the surface of the material are decoupled and their distance (i.e., offset) corresponds to the depth of Raman photon origin, 15 which can reach up to a few centimeters, 16 revealing the chemical composition of subsurface components that are covered by superficial, turbid layers. Although SORS has been employed in a number of biomedical applications, such as transfusion blood [17][18][19] and breast cancer, 20,21 studies on skin are still limited to wound assessment on rodents 22 and salmon skin assessment. 23 To our knowledge, our group is the only one to have employed a spatially offset mode to investigate skin-deep layer profiles of healthy human skin, 24 and with this study we aim to extend the application to skin cancer biopsies.…”

“…, offset) corresponds to the depth of Raman photon origin, 15 which can reach up to a few centimeters, 16 revealing the chemical composition of sub-surface components that are covered by superficial, turbid layers. Although SORS has been employed in a number of biomedical applications, such as transfusion blood 17–19 and breast cancer, 20,21 studies on skin are still limited to wound assessment on rodents 22 and salmon skin assessment. 23…”

Quantitative Assessment of Low-Dose Photodynamic Therapy Effects on Diabetic Wound Healing Using Raman Spectroscopy

“…The ability to study the burn-induced conformational changes of collagen using RS was confirmed [ 49 ]. Furthermore, RS has allowed for the development of other techniques, such as depth-sensitive RS, to perform depth-sensitive measurements [ 50 ]. In previous studies with RS, the difficulties facing wound healing, such as diabetes complications, were not studied, nor was a quantitative assessment and comparison of wound healing treatment using LDPDT with different parameters.…”