Biocompatibility enhancement via post-processing of microporous scaffolds made by optical 3D printer

Providing a 3D environment that mimics the native extracellular matrix is becoming increasingly important for various applications such as cell function studies, regenerative medicine, and drug discovery. Among the most critical parameters to consider are the scaffold’s complicated micro-scale geometry and material properties. Therefore, stereolithography based on photopolymerization is an emerging technique because of its ability to selectively form volumetric structures from liquid resin through localized polymerization reactions. However, one of the most important parameters of the scaffold is biocompatibility, which depends not only on the material but also on the exposure conditions and post-processing, which is currently underestimated. To investigate this systematically, microporous scaffolds with pore sizes of 0.05 mm3 corresponding to a porosity of 16,4% were fabricated using the stereolithography printer Asiga PICO2 39 UV from the widely used resins FormLabs Clear and Flexible. The use of various polymers is usually limited for cells because, after wet chemical development, the non-negligible amount of remaining monomers intertwined in the photopolymerized structures is significantly toxic to cells. Therefore, the aim of this research was to find the best method to remove monomers from the 3D scaffold by additional UV exposure. For this purpose, a Soxhlet extractor was used for the first time, and the monomers were immersed in different alcohols. A Raman microspectroscopy was also used to investigate whether different post-processing methods affect DC (cross-linking) to find out if this specifically affects the biocompatibility of the scaffolds. Finally, mesenchymal stem cells from rat dental pulp were examined to confirm the increased biocompatibility of the scaffolds and their ability to support cell differentiation into bone tissue cells

Conformational analysis of the telomerase RNA pseudoknot hairpin by Raman spectroscopy

We have measured the temperature-dependent Raman spectra of two 30-mer ribonucleotides that represent the wild-type (WT) and dyskeratosis congenita (DKC) mutant (MT) GC (107–108) → AG structures of the pseudoknot hairpin region of human telomerase RNA. We have used these structures, previously characterized by UV-melting and NMR, as a model system for our Raman investigation. We observe that Raman hypochromism of vibrational bands, previously assigned to specific bases or conformational RNA markers, reflect temperature-dependent alterations in the pentaloop and stem structures of these two oligonucleotides. We also observe that the intense ν(s)(O-P-O) band at 812 cm(−1) indicates the presence of A-form backbone structure at relatively low temperatures in both the WT and MT RNA sequences. The mutation induces a decrease in the intensity of the uridine (rU) band at 1244 cm(−1) associated with C2′-endo/anti ribose conformation in the pentaloop. Two transition temperatures (T(m)) were determined from the analysis of Raman difference intensity-temperature profiles of the 1256 cm(−1) band, which is associated with vibrations of cytidine (rC) residues, in particular, the C2′-endo/anti ribose conformation (T(m)1 = 23.6 ± 1.6°C for WT and 19.7 ± 2.8°C for MT; T(m)2 = 68.9 ± 1.8°C for WT and 70.9 ± 1.1°C for MT). From these results we can conclude that the DKC mutant 30-mer exhibits a lower stability in the pentaloop region and a slightly higher stability in the stem region than the WT 30-mer. This demonstrates that Raman bands, previously assigned to specific bases or conformational RNA markers, can be used to probe local structural features of the telomerase pseudoknot hairpin sequence

Phe-MetNH_2 terminal bombesin subfamily peptides : potential induced changes in adsorption on Ag, Au, and Cu electrodes monitored by SERS

Surface-enhanced Raman scattering, electro- chemistry, and generalized two-dimensional correlation analysis methods were used to characterize phyllolitorin and a peptide derived from Pseudophryne guntheri (PG-L). Phyllolitorin and PG-L were deposited onto Ag, Au, and Cu electrode surfaces at different applied electrode potentials in an aqueous solution at physiological pH, and the orientations and adsorption mechanisms of peptides were determined based on the enhancement, broadening, and shifts in the wavenumbers of specific bands. On the basis of these analyses, specific conclusions were drawn regarding the peptide geometry and changes in the geometry that occurred when the electrode type and applied electrode potential were varied. The phyllolitorin and PG-L deposited onto the Ag, Au, and Cu electrode surfaces showed bands that were due to the vibrations of moieties in contact with or in close proximity to the electrode surfaces and were thus located on the same side of the polypeptide backbone. These moieties included the Phe and Trp rings, the sulfur atom of Met, and the amide bond. Variations in the arrangement of these fragments were observed with changes in the metal surface and the applied electrode potential

Effect of potential on temperature-dependent SERS spectra of neuromedin B on Cu electrode

Adsorption of decapeptide neuromedin B (NMB) on copper electrode has been investigated by in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry in the temperature interval from 12 to 72 1 Cat 0.600 and 1.000 V potentials. It was found that intensities of peptide bands decrease at temperatures above 30 1 C with higher decrease slope at 1.000 V. Frequency of F12 mode (1004 cm 1 ) of non-surface-interactive phenylalanine residue was found to be insensitive to temperature variation at both studied electrode potentials, while frequency–temperature curves for surface-interactive groups (Amide-III, methylene) were found to be controlled by the potential. In particular, opposite frequency–temperature trends were detected for Amide-III (Am-III) mode indicating decrease in H-bonding interaction strength of amide C Q O and N–H groups above 38 1 Cfor 0.600 V, and increase in H-bonding interaction strength between 12 and 72 1 Cfor 1.000 V. Anomalous Am-III temperature- dependence of the frequency at 1.000 V was explained by temperature-induced transformation of a disordered secondary structure to a helix-like conformation. The potential-difference spectrum revealed interaction of methylene groups with Cu surface at sufficiently negative potential values because of the appearance of a soft C–H stretching band near 2825 cm 1 and a broad band near 2904 cm 1 assigned to vibration of a distal C–H bond of the surface-confined methylene group. Consequently, a rapid decrease in frequency of CH 2 -stretching band with temperature was observed at 1.000 V, while no essential frequency changes were detected for this mode at 0.600 V. The results show that electrode potential controls the temperature-dependence of the frequency for vibrations associated with surface- interactive molecular group