Assessment of transdermal delivery of topical compounds in skin scarring using a novel combined approach of Raman spectroscopy and HPLC

Objective: The goal of any topical formulation is efficient transdermal delivery of its active components. However, delivery of compounds can be problematic with penetration through tough layers of fibrotic dermal scar tissue. Approach: We propose a new combined approach using high performance liquid chromatography (HPLC) and Raman spectroscopy (RS) in assessment of penetration of topicals used in scar management. Results: Positive detection of compounds within the treatment topical using both techniques was validated with mass spectrometry. RS detected conformational structural changes; the 1655/1446 cm-1 ratio estimating collagen content significantly decreased (p<0.05) over weeks (W) 4, 12, and 16 compared to Day (D) 0. The amide I band, known to represent collagen and protein in skin, shifted from 1667 cm-1 to 1656 cm-1 which may represent a change from β-sheets in elastin to α-helices in collagen. Confirmatory elastin immunohistochemistry decreased compared to D0, conversely the collagen I/III ratio increased in the same samples by W12 (p<0.05, and p<0.0001 respectively), in keeping with normal scar formation. OCT attenuation coefficient representing collagen deposition was significantly decreased at W4 compared to D0 and increased at W16 (p<0.05). Innovation: This study provides a platform for further research on the simultaneous evaluation of the effects of compounds in cutaneous scarring by RS, and a role for RS in the therapeutic evaluation and theranostic management of skin scarring. Conclusions: RS can provide non-invasive information on the effects of topicals on scar pathogenesis and structural composition, validated by other analytical techniques such as HPLC.