Synthesis and characterization of biodegradable polyurethane films based on HDI with hydrolyzable crosslinked bonds and a homogeneous structure for biomedical applications.

Synthetic biodegradable polymers are considered strategic in the biomaterials field and are used in various applications. Among the polymers used as biomaterials, polyurethanes (PUs) feature prominently due to their versatility and the ability to obtain products with a wide range of physical and mechanical properties. In this work, new biodegradable polyurethane films were developed based on hexamethylene diisocyanate (HDI) and glycerol as the hard segment (HS), and poly(caprolactone) triol (PCL triol) and low-molecular-weight poly(ethylene glycol) PEG as the soft segment (SS) without the use of a catalyst. The films obtained were characterized by structural, mechanical and biological testing. A highly connected network with a homogeneous PU structure was obtained due to crosslinked bonds. The films showed amorphous structures, high water uptake, hydrogel behavior, and susceptibility to hydrolytic degradation. Mechanical tests indicated that the films reached a high deformation at break of up to 425.4%, an elastic modulus of 1.6 MPa and a tensile strength of 3.6 MPa. The materials presented a moderate toxic effect on MTT assay and can be considered potential materials for biomedical applications.

Synthesis, characterization and cytocompatibility of spherical bioactive glass nanoparticles for potential hard tissue engineering applications.

Nanotechnology offers a new strategy to develop novel bioactive materials, given that nano-scaled biomaterials exhibit an enhanced biocompatibility and bioactivity. In this work, we developed a method for the synthesis of spherical bioactive glass nanoparticles (BGNP) aimed at producing biomaterials for potential use in the repair of hard tissues. The BGNP were prepared using the sol-gel process based on the reaction of alkoxides and other precursors in aqueous media for obtaining the oxide-ternary system with the stoichiometric proportion of 60% SiO2, 36% CaO and 4% P2O5. The system was extensively characterized by Fourier transform infrared, x-ray diffraction and scanning electron microscope/energy-dispersive x-ray spectroscopy with regard to chemical composition, crystallinity and morphology. Moreover, the results suggested the BGNP to be highly bioactive, which was confirmed by the formation of a hydroxyapatite biomimetic layer on the material surfaces upon immersion in simulated body fluid solution. In addition, the bioactivity response toward the developed BGNPs was assessed by direct contact of osteoblast cells using resazurin and alkaline phosphatase assays. The new BGNP have presented a significant increase in the osteoblast in vitro cytocompatibility behavior as compared to similar micro-sized bioactive glass particles. Such improvement in the overall bioactive behavior of BGNP was attributed to the much higher surface area causing enhanced interactions at the cell-nanomaterial interfaces. Hence, based on the results, the BGNP produced are the biomaterials to be potentially utilized in hard tissue engineering applications.

Development of biodegradable polyurethane and bioactive glass nanoparticles scaffolds for bone tissue engineering applications.

The development of polymer/bioactive glass has been recognized as a strategy to improve the mechanical behavior of bioactive glass-based materials. Several studies have reported systems based on bioactive glass/biopolymer composites. In this study, we developed a composite system based on bioactive glass nanoparticles (BGNP), obtained by a modified Stöber method. We also developed a new chemical route to obtain aqueous dispersive biodegradable polyurethane. The production of polyurethane/BGNP scaffolds intending to combine biocompatibility, mechanical, and physical properties in a material designed for tissue engineering applications. The composites obtained were characterized by structural, biological, and mechanical tests. The films presented 350% of deformation and the foams presented pore structure and mechanical properties adequate to support cell growth and proliferation. The materials presented good cell viability and hydroxyapatite layer formation upon immersion in simulated body fluid.