Infrared Spectroscopic Verification of a α-Helical Collagen Structure in Glutaraldehyde-Free Crosslinked Bovine Pericardium for Cardiac Implants

Figure 1. Processing of spectral data obtained by IR spectroscopy. (A) Brightfield image of bovine pericardium cross-section with the scan area. (B) Intensity map of the analyzed sample region. (C) Plot of raw spectra obtained from IR spectroscopy. (D) Intensity map of the spectral region 1480 cm−1–1705 cm−1 after the selection of outliers (represented by white pixels). (E) Plot of the selected and offset corrected spectra. IR—infrared.

Figure 2. Centroid spectra after cluster analysis of GA-fixed (A) and SULEEI-treated bovine pericardium samples (B). The resulting subbands after curve fitting are exemplarily shown below (Figure 3) for the blue spectrum in (B). GA—Glutaraldehyde, SULEEI—Stabilization and sterilization of acellular pericardial scaffolds combining photo-initiated Ultraviolet cross-linking with Low-Energy Electron Irradiation.

Figure 3. (A) Plot of the calculated subbands together with the resulting envelope and the original centroid spectrum. (B) Box-whisker plot of the calculated band area variations for GA-fixed (white bars) and SULEEI-treated (grey bars) samples. GA—Glutaraldehyde, SULEEI—Stabilization and sterilization of acellular pericardial scaffolds combining photo-initiated Ultraviolet cross-linking with Low-Energy Electron Irradiation.

Figure 4. Box–whisker plots representing the differences in relative band area between GA-fixed and SULEEI-treated samples for side chains (A) and α-helix (B) and amino groups (C). n = 5. Unpaired t-test. * p ≤ 0.05. GA—Glutaraldehyde, SULEEI—Stabilization and sterilization of acellular pericardial scaffolds combining photo-initiated Ultraviolet cross-linking with Low-Energy Electron Irradiation.

Figure 5. (A) RGB images of GA-fixed samples. The red channel reflects band areas of 1532 cm−1 (amino groups), the green channel visualizes band areas of 1601 cm−1 (side chains), and the blue channel represents band areas of 1656 cm−1 (α-helix). (B) H&E sections parallel stained to RGB images. Numbers 1–5 represent biological replicates of the bovine pericardium. RGB—Red—Green—Blue, GA—Glutaraldehyde, H&E—Hematoxylin and Eosin.

Figure 6. (A) RGB images of SULEEI-treated samples. The red channel reflects band areas of 1532 cm−1 (amino group), the green channel visualizes band areas of 1601 cm−1 (side chains), and the blue channel represents band areas of 1656 cm−1 (α-helix). (B) H&E sections parallel stained to RGB images. Numbers 1–5 represent biological replicates of the bovine pericardium. RGB—Red—Green—Blue, SULEEI—Stabilization and sterilization of acellular pericardial scaffolds combining photo-initiated Ultraviolet cross-linking with Low-Energy Electron Irradiation, H&E—Hematoxylin and Eosin.