RESUMO
Segmented polyurethanes were prepared with polycaprolactone diol as soft segment and various amounts of 4,4´-Methylenebis(cyclohexyl isocyanate) and atorvastatin, a statin used for lowering cholesterol, in order to obtain SPU with different content of rigid segments. Polyurethanes with 35% or 50% of rigid segment content were physicochemically characterized and their biocompatibility assessed with L929 fibroblasts. High concentrations of atorvastatin were incorporated by increasing the content of rigid segments as shown by FTIR, Raman, NMR, XPS and EDX. Thermal and mechanical characterization showed that polyurethanes containing atorvastatin and 35% of rigid segments were low modulus (13 MPa) semicrystalline polymers as they exhibited a glass transition temperature (Tg) at -38 °C, melting temperature (Tm) at 46 °C and crystallinity close to 35.9% as determined by DSC. In agreement with this, X-ray diffraction showed reflections at 21.3° and 23.6° for PCL without reflections for atorvastatin suggesting its presence in amorphous form with higher potential bioavailability. Low content of rigid segments led to highly degradable polymer in acidic, alkaline and oxidative media with an acceptable fibroblast cytotoxicity up to 7 days possibly due to low atorvastatin content.
Assuntos
Atorvastatina/química , Materiais Biocompatíveis/química , Cianatos/química , Poliésteres/química , Poliuretanos/química , Animais , Atorvastatina/toxicidade , Materiais Biocompatíveis/toxicidade , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Camundongos , Estrutura Molecular , Microscopia Óptica não Linear , Poliésteres/toxicidade , Poliuretanos/toxicidade , Espectrofotometria Infravermelho , TemperaturaRESUMO
Electrospun polycaprolactone (PCL)/chitosan (CH) blend scaffolds with different CH weight ratios were prepared to study the effect of scaffold composition on its physicochemical and biological properties. Scanning electron microscopy showed bead-free homogeneous randomly arranged nanofibers whose average diameter decreased from 240 to 110 nm with increasing CH content. The infrared spectra of the PCL/CH blends were very similar to the neat PCL scaffold. Energy-dispersive x-ray spectroscopy analysis confirmed the presence of carbon, oxygen and nitrogen in the scaffolds, although fluorine-from chemicals used as solvent-was also detected. The water contact angle decreased from 113° (for PCL) to 52° with increasing chitosan content. The biocompatibility was evaluated using fibroblasts and Schwann cell (SC) cultures. Cytotoxicity assays using fibroblasts demonstrated that electrospun scaffolds could be considered as non-cytotoxic material. Biocompatibility tests also revealed that the SCs adhered to scaffolds with different CH content, although the formulation containing CH at 5 wt% exhibited the highest proliferation on days 1 and 3. A better cell distribution was observed in the CH/PCL blends than in the neat PCL or CH scaffolds, where the cells were clustered. Immunochemistry analysis confirmed that SCs expressed the specific p75 cell marker on the scaffolds, suggesting that PCL/CH scaffolds would be good candidates for peripheral nerve tissue engineering.
Assuntos
Quitosana/química , Poliésteres/química , Células de Schwann/citologia , Engenharia Tecidual/métodos , Alicerces Teciduais/química , Animais , Materiais Biocompatíveis/química , Proliferação de Células , Sobrevivência Celular , Eletroquímica , Fibroblastos/metabolismo , Camundongos , Microscopia Eletrônica de Varredura , Nanofibras/química , Neurônios/metabolismo , Ratos , Solventes , Resistência à Tração , Fatores de TempoRESUMO
The aim of this work was to provide some fundamental information for optimization of silanization of hydroxyapatite intended for bone cement formulations. The effect of 3-(trimethoxysilyl) propyl methacrylate (MPS) concentration and solvent system (acetone/water or methanol/water mixtures) during HA silanization was monitored by X-ray diffraction (XRD), FTIR spectroscopy and EDX analysis. The effect of silanized HA on the mechanical properties of acrylic bone cements is also reported. It was found that the silanization process rendered hydroxyapatite with lower crystallinity compared to untreated HA. Through EDX, it was observed that the silicon concentration in the HA particles was higher for acetone-water than that obtained for methanol-water system, although the mechanical performance of cements prepared with these particles exhibited the opposite behavior. Taking all these results together, it is concluded that methanol-water system containing MPS at 3wt.% provides the better results during silanization process of HA.
Assuntos
Cimentos Ósseos/química , Durapatita/química , Silanos/química , Cimentos Ósseos/metabolismo , Força Compressiva , Módulo de Elasticidade , Teste de Materiais , Metacrilatos/química , Silício/química , Solventes/química , Resistência à TraçãoRESUMO
In this work, the effect of the incorporation of comonomers containing amine groups on the mechanical and fracture properties of acrylic bone cements was studied. Cements were prepared with either diethyl amino ethyl acrylate (DEAEA), dimethyl amino ethyl methacrylate (DMAEM) or diethyl amino ethyl methacrylate (DEAEM) as comonomer in the liquid phase. It was found that strength and modulus decreased with increasing comonomer content in the bending and compressive tests. It was also observed that fracture toughness (K(IC)) and the critical strain energy release rate (G(IC)) increase with increasing comonomer concentration and are significantly higher compared to the control formulation. The mechanical and fracture properties of cements were also evaluated after soaking the specimens in Simulated Body Fluid (SBF) for 3 and 6 months. It was found that the mechanical properties of cements decreased when the samples were stored in SBF, although the impact strength increased in the first 3 months and then decreased. SEM micrographs were in agreement with the results obtained during mechanical characterization as the increase in toughness was confirmed by the appearance of ductile tearing pattern which is associated with plastic deformation.