Đặc điểm phổ Raman của biểu bì và chân bì da người dưới tác động của Formaldehyd trong 6 tháng

Abstract

rmis and dermis under the effect of formaldehyde during the fixation and preservation process in 6-months. 
Materials and methods: A prospective, longitudinal experimental study was conducted on 12 human skin tissue samples, which were fixed and preserved according to the Melnikov-Razvedenkov principle at Institute 69. A 785 nm excitation laser source integrated into a Raman microspectrometer was used to examine the characteristic molecular bonding features within the epidermis and dermis of the experimental samples. Raman spectra were acquired from cryosections at six time points: the initial fresh tissue, and after 1 week, 5 weeks, 11 weeks, 3 months, and 6 months of storage; the intensities of the spectral bands were normalized against the phenylalanine band at 1003 cm⁻¹. UV-Vis spectrophotometry was employed to quantify the formaldehyde concentration in the solutions used to preserve the samples at each experimental time interval. 
Results: After one week of fixation, two spectral bands at 1041 cm⁻¹ (methylene glycol) and at 1492 cm⁻¹ appeared in both the epidermis and the dermis; these were absent from original fresh tissue and are associated with formaldehyde bound to the tissue. The normalized intensity of the 1041 cm⁻¹ band was highest after fixation (epidermis 0.57 ± 0.12; dermis 0.55 ± 0.13). It then decreased in a statistically significant manner over the subsequent observation periods, up to 5 weeks (p < 0.01), after which no statistically significant differences were observed at later time points (0.31 - 0.33 at the 3-month and 6-month marks). The 1492 cm⁻¹ band did not change significantly across stages (0.24 - 0.26; p > 0.05). In the solution used for sample preservation, the formaldehyde concentrations were 18.86 ± 3.13 mg/L after 11 weeks, 26.27 ± 2.14 mg/L after 3 months and 27.40 ± 0.44 mg/L after 6 months. 
Conclusion: The Raman spectral characteristics of formaldehyde are preserved in both the epidermal and dermal layers during the fixation and preservation process. The signal for free formaldehyde decreases after the tissue is transferred to a formaldehyde-free solution, subsequently remaining relatively stable, while the signal at bands 1492 cm⁻¹ remains stable for up to 6 months of preservation.