Medical grade 3D printable bioabsorbable PLDL/Mg and PLDL/Zn composites for biomedical applications.

Medical grade PLDL, PLDL/Mg and PLDL/Zn filaments were manufactured by a dual extrusion method and used to prepare coupons and scaffolds with controlled porosity by fused filament fabrication. The mechanical properties, degradation mechanisms and biological performance were carefully analyzed. It was found that the presence of 4 vol.% of Mg and Zn particles did not substantially modify the mechanical properties but accelerated the degradation rate of PLDL. Moreover, the acidification of the pH due to degradation of the PLDL was reduced in the presence of metallic particles. Finally, cell adhesion and proliferation were excellent in the medical grade PLDL as well as in the polymer/metal composites. These results demonstrate the potential of bioabsorbable metal/polymer composites to tailor the mechanical properties, degradation rate and biocompatibility for specific clinical applications.

Interlocking Matrix and Filler for Enhanced Individualization and Reinforcement in Polymer-Single-Walled Carbon Nanotube Composites.

Poor individualization and interfacial adhesion prevent single-walled carbon nanotube (SWNT)-polymer composites from reaching outstanding mechanical properties. With much larger diameters, but common structural features (high aspect ratio and absence of functional groups for covalent or supramolecular attachment with the polymer), carbon fibers face similar problems, which are addressed by covering the fibers with a thin layer of polymer. This sizing strategy has allowed carbon fibers to become the filler of choice for the highest performing materials. Inspired by this, here we investigate the use of the mechanical bond to wrap SWNTs with a layer of polymeric material to produce SWNTs mechanically interlocked with a layer of polymer. We first validate the formation of mechanically interlocked nanotubes (MINTs) using mixtures of SWNTs of relatively large average diameter (1.6 ± 0.4 nm), which are commercially available at reasonable prices and therefore could be technologically relevant as polymer fillers. We then design and synthesize by ring-opening metathesis polymerization (ROMP) a polymer decorated with multiple U-shaped molecules, which are later ring-closed around the SWNTs using metathesis. The obtained hybrids contain a high degree of individualized SWNTs and exhibit significantly increased mechanical properties when compared to the matrix polymer. We envision that this strategy could be employed to produce SWNTs interlocked with polymer layers with various designs for polymer reinforcement.

Effect of Fiber-Matrix Interface on the Mechanical Response of a Woven Carbon Fiber/PEEK Composite Material.

This work studies the relationship between the interface shear strength (IFSS) and the mechanical response of a carbon fiber-reinforced composite with a polyether-ether-ketone (PEEK) thermoplastic matrix. Two types of laminates were studied: the first kind was manufactured with as-received fiber fabrics, while specimens belonging to the second one were fabricated with thermally treated fibers where the original sizing agent was removed. IFSS values were measured with the push-in test, showing that treated fibers exhibit a 25% higher critical shear stress. Microscopic inspection of the laminates revealed that untreated specimens were prone to debonding, generating a much higher crack density. This difference was detected by the C-Scan technique and triggered in the response of both laminates under tensile tests at ±45∘ fiber orientation, where maximum stress and strain at break values of desized specimens showed an increase of 37% and 190%, respectively. Results confirmed that the original fiber sizing weakened the fiber-matrix interface. Lastly, the tensile response of the composite is analyzed in light of interface quality.

Nanostructured medical sutures with antibacterial properties.

Bacterial repellence in suture materials is a desirable property that can potentially improve the healing process by preventing infection. We describe a method for generating nanostructures at the surface of commercial sutures of different composition, and their potential for preventing biofilm formation. We show how bacteria attachment is altered in the presence of nanosized topographies and identify optimum designs for preventing it without compromising biocompatibility and applicability in terms of nanostructure robustness or tissue friction. These studies open new possibilities for flexible and cost-effective realization of topography-based antibacterial coatings for absorbable biomedical textiles.