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In the quest for advancing the performance of metallic implants, surface modification emerges as a pivotal strategy to mitigate ion depletion, enhance the host's biological response, and exhibit anti-microbial behavior with reduced cytotoxicity. In this study, we developed a non-traditional electrophoretic deposition (EPD) hybrid coating for medical-grade stainless steel 316 L (SS316L) surfaces covered with a segmented polyurethane (SPU). These coatings are composed of anatase TiO₂ nanotubes (TiO₂_A), and antibiotics (nisin N or gentamicin G). We characterized the modified metals using FTIR and Raman spectroscopy, contact angle measurements, AFM, TGA, SEM-EDX, as well as assessing their antimicrobial response and cell cytotoxicity. The results demonstrate the formation of porous surfaces with embedded nanotubes and antibiotics within and on the polyurethane surfaces. Samples with SPU+ TiO₂_AG EPD exhibited superior coverage, antimicrobial properties, and enhanced viability compared to cases where only particles or antibiotics were coated individually. Additionally, samples of SPU+ TiO₂_AN EPD displayed favorable hydrophilicity and suitable cytotoxicity. Therefore, the synergistic effect of nanoparticles and antibiotics positively influences the functionality of the coating.

The electrical, mechanical and piezoresistive responses of vinyl ester nanocomposites made of two types of multilayer graphene sheets (GSs) and multiwall carbon nanotube hybrid fillers at different relative concentrations is presented. Two types of GSs are used in order to evaluate the role of their physicochemical properties. The best mechanical properties were achieved with hybrids at 75% relative concentration of GSs. Collaborative effects were also observed in the electrical conductivity of the hybrids at this relative concentration. The flexural piezoresistive response yielded low sensitivity (with both, positive and negative gage factors) at the compression side of the flexural coupon. On the contrary, the tensile side of the coupon always presented positive resistance changes and significantly higher piezoresistive sensitivity. The highest piezoresistive sensitivity was found for hybrid materials with 75% relative concentration of GSs, using the graphenic sheets with larger lateral dimensions and higher structural quality (lower Raman I/I ratio).

Segmented polyurethanes based on polycaprolactone, 4,4 (metylene-bis-cyclohexyl) isocyanate, and L-lysine were synthesized, manufactured as small vascular grafts and characterized according to ISO 7198 standard for cardiovascular implants—tubular vascular prosthesis. In terms of mechanical properties, the newly synthesized polyurethane films exhibited lower secant modulus than Tecoflex™ SG 80A, a well-known medical grade polyurethane. Similarly, when tested as grafts, the L-lysine-based polyurethane exhibited lower longitudinal failure load (11.5 N vs. 116 N), lower circumferential failure load per unit length (5.67 N/mm vs. 14.0 N/mm) and lower suture forces for both nylon (13.3 N vs. 24.0 N) and silk (14.0 N vs. 19.3 N) when compared to Tecoflex™ SG 80A grafts. L-Lysine-based graft exhibited a burst strength of 3620 mmHg (482.6 kPa) and a compliance of 0.16%/mmHg. The cell adhesion was demonstrated with NIH/3T3 fibroblasts where cell adhesion was observed on both films and grafts, while cell alignment was observed only on the grafts. The mechanical properties of this polyurethane and the possibility of strain-induced PCL crystals as the switching phase for shape memory materials, allowed a strain recovery ratio and a strain fixity ratio with values higher than 95% and 90%, respectively, with a repeatability of the shape-memory properties up to 4 thermo-mechanical cycles. Overall, the properties of lysine-based polyurethanes are suitable for large diameter vascular grafts where cell alignment can be controlled by their shape memory potential.

The synthesis of novel polyurethanes is a subject of increasing interest, especially those that involve biologically active molecules. Generally, the reports on the synthesis of segmented polyurethanes using modified amino acids as chain extenders assume that the reaction occurs due to functionalities (OH and NH2) of the last compounds. However, few works really prove the reaction takes place with unmodified amino acids. In this work, spectroscopic techniques such as 1H, 13C, and 1H-1H COSY NMR and FTIR were used to chemical characterization of poly(ureaamide)urethanes synthesized from polycaprolactone diol (PCL diol 530), 4,4¿-methylene-bis(cyclohexyl isocyanate) (H12MDI), and amino acids such as L-arginine, glycine or L-aspartic acid as chain extenders. In addition, model compounds (without PCL diol) were analyzed to confirm reaction of amino acids via urea and amide formation. Additionally, the polymers exhibited different physicochemical and mechanical properties depending on the chain extender used. These results suggest that unmodified amino acids can be used as chain extenders in the synthesis of poly(amide-urea) urethanes for biomedical applications

Nanocomposites prepared with segmented polyurethane (SPU) and commercially available nanoclays (Cloisite™ Na+, Cloisite™ 15A, Cloisite™ 30B) were studied using thermogravimetric analysis coupled with Fourier Transform Infrared Spectroscopy (TGA/FTIR). The results showed that the thermal degradation of unfilled SPU and the 4, 6 and 10 wt% hand mixed nanocomposites occurred in two stages being the first due to degradation of hard segments and the second due to the degradation of soft segments. It was also found that the thermal stability of these nanocomposites was not improved by increasing nanoclay concentration except for SPU/Cloisite™ 15A nanocomposites were a 40 °C increase was observed. In a similar manner, FTIR spectra of the evolved gases obtained after the thermal degradation of these nanocomposites were qualitatively similar to the unfilled polymer except in those containing Cloisite™ 30B where isocyanate absorptions were detected. In contrast, SPU/Cloisite™ 30B nanocomposites prepared by in-situ polymerization, exhibited higher thermal stability than the corresponding hand mixed nanocomposites. In addition, these nanocomposites exhibited the presence of carbon dioxide in the evolved gases during its second degradation stage which was not observed in the hand mixed nanocomposites. In this case, it can be said that the presence of clays in the nanocomposites has a significant effect on the thermal degradation pathways.

The thermal degradation behavior of polymethacrylates containing amine groups such as poly(N,N-diethyl aminoethyl methacrylate), PDEAEM, and poly(N-ethyl-m-tolyl-aminoethyl methacrylate), PMEET, has been studied using thermogravimetry coupled with infrared spectroscopy (TGA/FTIR). PDEAEM showed two degradation stages whereas PMEET displayed only one. The thermal degradation of PDEAEM initially takes place through ester cleavage of the polymethacrylate, generating volatile tertiary amines and alcohols and polymethacrylic anhydride in the remaining solid material. This is followed by further fragmentation of the modified polymeric chain formed. It was also observed that storage of the original polymer affected the thermal decomposition behavior of PDEAEM. The main thermal degradation pathway for PMEET is an immediate backbone chain scission to yield oligomers.