Collagen formation observed from healing calvarial defects with principal component analysis of Raman scattering

Functionalizing Collagen Membranes with MSC-Conditioned Media Promotes Guided Bone Regeneration in Rat Calvarial Defects

Functionalizing biomaterials with conditioned media (CM) from mesenchymal stromal cells (MSC) is a promising strategy for enhancing the outcomes of guided bone regeneration (GBR). This study aimed to evaluate the bone regenerative potential of collagen membranes (MEM) functionalized with CM from human bone marrow MSC (MEM-CM) in critical size rat calvarial defects. MEM-CM prepared via soaking (CM-SOAK) or soaking followed by lyophilization (CM-LYO) were applied to critical size rat calvarial defects. Control treatments included native MEM, MEM with rat MSC (CEL) and no treatment. New bone formation was analyzed via micro-CT (2 and 4 weeks) and histology (4 weeks). Greater radiographic new bone formation occurred at 2 weeks in the CM-LYO group vs. all other groups. After 4 weeks, only the CM-LYO group was superior to the untreated control group, whereas the CM-SOAK, CEL and native MEM groups were similar. Histologically, the regenerated tissues showed a combination of regular new bone and hybrid new bone, which formed within the membrane compartment and was characterized by the incorporation of mineralized MEM fibers. Areas of new bone formation and MEM mineralization were greatest in the CM-LYO group. Proteomic analysis of lyophilized CM revealed the enrichment of several proteins and biological processes related to bone formation. In summary, lyophilized MEM-CM enhanced new bone formation in rat calvarial defects, thus representing a novel 'off-the-shelf' strategy for GBR.

Polycaprolactone/Beta-Tricalcium Phosphate Scaffolds Obtained via Rotary Jet-Spinning: in vitro and in vivo Evaluation

This study aimed to evaluate in vitro and in vivo polymeric membranes obtained by a rotary jet-spinning process for the repair of critical bone defects in the calvaria of Wistar rats, for future use in tissue engineering. Experimental sample collections were performed on the 30, 60 and 90th postoperative days, and the analyses performed were histomorphometric, immunohistochemistry, and western blotting. Reducing inflammatory infiltrate in all groups and experimental periods, angiogenesis on the 30th day did not show any difference between the groups, on the 60th day, 5% polycaprolactone/beta-tricalcium phosphate(PCL/β-TCP) was high compared to control (C), and on the 90th day, the same group reduced when compared to C and 10% PCL/β-TCP. The fibroplasia presented oscillations in every segment; on the 30th and 60th day, there was an increase in 5% PCL/β-TCP, which decreased by the 90th day compared to group C. 10% PCL/β-TCP decreased compared to C on the 60th and 90th day. The percentage of the collagen area remained high in all groups and all experimental periods. Immunohistochemistry quantifications showed variations in bone metabolism suggesting new bone formation. The 5 and 10% PCL/β-TCP scaffold were promising for the bone regeneration process because they participated in the modulation of inflammation, angiogenesis, fibroplasia, and collagenosis.

RAMAN AND ATR-FTIR SPECTROSCOPY TOWARDS CLASSIFICATION OF WET BLUE BOVINE LEATHER USING RATIOMETRIC AND CHEMOMETRIC ANALYSIS

Abstract

There is a substantial loss of value in bovine leather every year due to a leather quality defect known as “looseness”. Data show that 7% of domestic hide production is affected to some degree, with a loss of $35 m in export returns. This investigation is devoted to gaining a better understanding of tight and loose wet blue leather based on vibrational spectroscopy observations of its structural variations caused by physical and chemical changes that also affect the tensile and tear strength. Several regions from the wet blue leather were selected for analysis. Samples of wet blue bovine leather were collected and studied in the sliced form using Raman spectroscopy (using 532 nm excitation laser) and Attenuated Total Reflectance - Fourier Transform InfraRed (ATR-FTIR) spectroscopy. The purpose of this study was to use ATR-FTIR and Raman spectra to classify distal axilla (DA) and official sampling position (OSP) leather samples and then employ univariate or multivariate analysis or both. For univariate analysis, the 1448 cm− 1 (CH2 deformation) band and the 1669 cm− 1 (Amide I) band were used for evaluating the lipid-to-protein ratio from OSP and DA Raman and IR spectra as indicators of leather quality. Curve-fitting by the sums-of-Gaussians method was used to calculate the peak area ratios of 1448 and 1669 cm− 1 band. The ratio values obtained for DA and OSP are 0.57 ± 0.099, 0.73 ± 0.063 for Raman and 0.40 ± 0.06 and 0.50 ± 0.09 for ATR-FTIR. The results provide significant insight into how these regions can be classified. Further, to identify the spectral changes in the secondary structures of collagen, the Amide I region (1600–1700 cm− 1) was investigated and curve-fitted-area ratios were calculated. The 1648:1681 cm− 1 (non-reducing: reducing collagen types) band area ratios were used for Raman and 1632:1650 cm− 1 (triple helix: α-like helix collagen) for IR. The ratios show a significant difference between the two classes. To support this qualitative analysis, logistic regression was performed on the univariate data to classify the samples quantitatively into one of the two groups. Accuracy for Raman data was 90% and for ATR-FTIR data 100%. Both Raman and ATR-FTIR complemented each other very well in differentiating the two groups. As a comparison, and to reconfirm the classification, multivariate analysis was performed using Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). The results obtained indicate good classification between the two leather groups based on protein and lipid content. Principal component score 2 (PC2) distinguishes OSP and DA by symmetrically grouping samples at positive and negative extremes. The study demonstrates an excellent model for wider research on vibrational spectroscopy for early and rapid diagnosis of leather quality.

Graphical abstract

Single red blood cell analysis reveals elevated hemoglobin in poikilocytes

Abnormally shaped red blood cells (RBCs), called poikilocytes, can cause anemia. At present, the biochemical abnormalities in poikilocytes are not well understood. Normal RBCs and poikilocytes were analyzed using whole-blood and single-cell methods. Poikilocytes were induced in rat blood by intragastrically administering titanium dioxide (TiO₂) nanoparticles. Complete blood count and inductively coupled plasma mass spectrometry analyses were performed on whole-blood to measure average RBC morphology, blood hemoglobin (HGB), iron content, and other blood parameters. Follow-up confocal Raman spectroscopy was performed on single RBCs to analyze cell-type-specific HGB content. Two types of poikilocytes, acanthocytes and echinocytes, were observed in TiO₂ blood samples, along with normal RBCs. Acanthocytes (diameter 7.7  ±  0.5  μm) and echinocytes (7.6  ±  0.6  μm) were microscopically larger (p  <  0.05) than normal RBCs (6.6  ±  0.4  μm) found in control blood samples (no TiO₂ administration). Similarly, mean corpuscular volume was higher (p  <  0.05) in TiO₂ whole-blood (70.70  ±  1.97  fl) than in control whole-blood (67.42  ±  2.03  fl). Poikilocytes also had higher HGB content. Mean corpuscular hemoglobin was higher (p  <  0.05) in TiO₂ whole-blood (21.84  ±  0.75  pg) than in control whole-blood (20.8  ±  0.32  pg). Iron content was higher (p  <  0.001) in TiO₂ whole-blood (697.0  ±  24.5  mg  /  l) than in control whole-blood (503.4  ±  38.5  mg  /  l), which supports elevated HGB as iron is found in HGB. HGB-associated Raman bands at 1637, 1585, and 1372  cm^-  1 had higher (p  <  0.001) amplitudes in acanthocytes and echinocytes than in RBCs from control blood and normal RBCs from TiO₂ blood. Further, the 1585-cm^-  1 band had a lower (p  <  0.05) amplitude in normal RBCs from TiO₂ versus control RBCs. This represents biochemical abnormalities in normal appearing RBCs. Overall, poikilocytes, especially acanthocytes, have elevated HGB.