Multifunctional Platform for Covalent Titanium Coatings: Micro-FTIR, XPS, and NEXAFS Characterizations.

This work aims at preparing and characterizing a versatile multifunctional platform enabling the immobilization of macromolecules on a titanium surface by robust covalent grafting. Functionalized titanium is widely used in the biomedical field to improve its properties. Despite its high biocompatibility and osteointegrability, titanium implants are not very stable in the long term due to the onset of inflammation and bacterial infections. The proposed method allows the superficial insertion of three different organic linkers to be used as anchors for the attachment of biopolymers or bioactive molecules. This strategy used green solvents and is a good alternative to the proposed classic methods that employ organic solvents. The uniformly modified surfaces were characterized by micro-Fourier transform infrared spectroscopy (micro-FTIR), X-ray Photoelectron spectroscopy (XPS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS). The latter made it possible to assess the orientation of the linker molecules with respect to the titanium surface. To test the efficiency of the linkers, two polymers (alginate and 2-(dimethylamino)-ethyl methacrylate (PDMAEMA)), with the potential ability to increase biocompatibility, were covalently attached to the titanium surfaces. The obtained results are a good starting point for the realization of stable polymeric coatings permanently bonded to the surface that could be used to extend the life of biomedical implants.

Cerium Coatings on Pristine and Nanostructured Ti and Ti6Al4V Surfaces: Bioactivity, Resistance in Simulated Inflammatory Conditions, and Antibacterial Performance.

Despite the significant contribution of titanium and its alloys for hard tissue regenerative medicine, some major issues remain to be solved. Implants' long-term stability is threatened by poor osseointegration. Moreover, bacterial adhesion and excessive inflammatory response are also to be considered in the design of a device intended to be integrated into the human body. Here, a cerium mixed oxide (CeOx) coating was realized on pristine and nanotubular-structured Ti and Ti6Al4V surfaces using a simple layer-by-layer drop-casting technique. Bioactivity, resistance in simulated inflammatory conditions, and bactericidal capacity were evaluated as a function of morphological surface characteristics combined with the cerium quantity deposited. The results obtained suggest that the presence of CeOx on the surfaces with nanotubes enhanced osseointegration, while on the non-nanostructured surfaces, this coating improved resistance under oxidative stress and provided excellent antibacterial properties.

Self-assembling nanowires from a linear l,d-peptide conjugated to the dextran end group.

Preparation and characterization of a block-like l,d-octapeptide-dextran conjugate DEX29-(l-Val-d-Val)4 self-assembling into nanowire structures is reported. The conjugate was prepared by solid phase click-chemistry on an alkyne group N-terminus functionalized peptide with a regularly alternating enantiomeric sequence. Low molecular weight dextran (Xn = 29) with moderately low dispersity (1.30) was prepared by controlled acid hydrolysis and dialysis with selected cut-off and functionalized with an azido group on the reducing end by reductive amination. The strong hydrogen bonds and hydrophobic interactions of the (l-Val-d-Val)4 linear peptide drive the conjugate to self-assemble into long (0.1-1 µm) nanowires. To our knowledge, this is the first example of a peptide-polysaccharide conjugate that can self-assemble into a nanowire architecture.

Identification of remodeled collagen fibers in tumor stroma by FTIR Micro-spectroscopy: A new approach to recognize the colon carcinoma.

The tumor stroma plays a pivotal role in colon cancer genesis and progression. It was observed that collagen fibers in the extracellular matrix (ECM) of cancer stroma, undergo a strong remodeling. These fibrous proteins result more aligned and compact than in physiological conditions, creating a microenvironment that favors cancer development. In this work, micro-FTIR spectroscopy was applied to investigate the chemical modifications in the tumor stroma. Using Fuzzy C-means clustering, mean spectra from diseased and normal stroma were compared and collagen was found to be responsible for the main differences between them. Specifically, the modified absorptions at 1203, 1238, 1284 cm-1 and 1338 cm-1 wavenumbers, were related to the amide III band and CH2 bending of side chains. These signals are sensitive to the interactions between the α-chains in the triple helices of collagen structure. This provided robust chemical evidence that in cancer ECM, collagen fibers are more parallelized, stiff and ordered than in normal tissue. Principal Component Analysis (PCA) applied to the spectra from malignant and normal stroma confirmed these findings. Using LDA (Linear Discriminant Analysis) classification, the absorptions 1203, 1238, 1284 and 1338 cm-1 were examined as spectral biomarkers, obtaining quite promising results. The use of a PCA-LDA prediction model on samples with moderate tumor degree further showed that the stroma chemical modifications are more indicative of malignancy compared to the epithelium. These preliminary findings have shown that micro-FTIR spectroscopy, focused on collagen signals, could become a promising tool for colon cancer diagnosis.