Maria Elena Leyva

Electrochemical preparation and characterization of PNIPAM-HAp scaffolds for bone tissue engineering

In the last decade, a variety of methods for fabrication of three-dimensional biomimetic scaffolds based on hydrogels have been developed for tissue engineering. However, many methods require the use of catalysts which compromises the biocompatibility of the scaffolds. The electrochemical polymerization (ECP) of acrylic monomers has received an increased attention in recent years due to its versatility in the production of highly biocompatible coatings for the electrodes used in medical devices. The main aim of this work was the use of ECP as scaffold fabrication technique to produce highly porous poly(N-isopropylacrylamide) (PNIPAM)/hydroxyapatite (HAp) composite for bone tissue regeneration. The prepared PNIPAM-HAp porous scaffolds were characterized by SEM, FTIR, water swelling, porosity measurements and X-ray diffraction (XRD) techniques. FTIR indicates that ECP promotes a successful conversion of NIPAM to PNIPAM. The water swelling and porosity were shown to be controlled by the HAp content in PNIPAM-HAp scaffolds. The PNIPAM-HAp scaffolds exhibited no cytotoxicity to MG63 cells, showing that ECP are potentially useful for the production of PNIPAM-HAp scaffolds. To address the osteomyelitis, a significant complication in orthopedic surgeries, PNIPAM-HAp scaffolds were loaded with the antibiotic oxacillin. The oxacillin release and the bacterial killing activity of the released oxacillin from PNIPAM-HAp against S. aureus and P. aeruginosa were demonstrated. These observations demonstrate that ECP are promising technique for the production of non-toxic, biocompatible PNIPAM-HAp scaffolds for tissue engineering.

Influência da Estrutura química do co-monômero nas propriedades mecânicas e adesivas de redes epoxídicas

The mechanical and adhesive properties of epoxy formulations based on diglycidyl ether of bisphenol A cured with various aliphatic amines were evaluated in the glass state. Impact and uniaxial compression tests were used to determine the impact energy, elastic modulus and yield stress, respectively. The adhesion tests were carried out in steel-steel joints using single lap shear, T-peel and impact adhesive joints geometry. The better mechanical and adhesive behavior of the networks is obtained for highly flexible chains and/or a high elastic modulus. The 1-(2-aminoethyl)piperazine epoxy network presents the best adhesive properties, high flexibility, and the largest impact energy. However, it possesses low elastic modulus and yield stress. Also, it exhibits increased peel strength and impact energy with a reduction in the lap shear strength.

Estudo da mistura do éter diglicidílico do bisfenol-A com poli(etileno-co-acetato de vinila)-g-poli(metacrilato de metila) por espectroscopia dielétrica e calorimetria exploratória diferencial

The calorimetric curves and the dielectric relaxation spectra corresponding to blends of diglycidyl ether of bisfenol-A with different concentration of poly(ethylene-co-vinyl acetate)-g-poly(methyl methacrylate) (EVA-g-PMMA) were obtained using differential scanning calorimetry (DSC) and dielectric relaxation espectroscopy (DSR), respectively. The glass transition temperature (Tg) of the PMMA segment of increases with the copolymer content in the blends. The Tg behavior was described by the Gordon-Taylor equation, using the weight fraction of PMMA. In the dielectric relaxation spectrum, α relaxations of the two molecular segments are deserved. In this case, the increase in copolymer concentration led to the increase of α -relaxation corresponding to the PMMA segment, and there was not change in α -relaxation for the EVA fraction. These behaviors show that the structural segments have very different interactions with the epoxy monomer. The PMMA segment of is miscible in the epoxy resin, therefore, provoked strong interactions with the resin when compared to EVA fraction, which presented no apparent interaction and gave origin to the system heterogenity.

Novas tendências dos polímeros epoxídicos: propriedades biológicas in vitro de formulações para aplicações médicas

In this paper the in vitro biological properties are presented for three epoxy networks based on diglycidyl ether of bisphenol-A epoxy prepolymer cured with aliphatic amines, namely triethylenetetramine (TETA), 1-(2-aminoethyl) piperazine (AEP) and isophoronediamine (IPD). The biological interactions between the fully-cured epoxy materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented using a UV/VIS spectrometer and SEM analysis. Studies of protein adsorption onto polymeric surfaces showed that the three epoxy materials adsorbed more albumin than fibrinogen. Studies about platelet adhesion and thrombus formation of two epoxy polymers indicated that AEP and IPD network exhibits good hemocompatible behavior. The epoxy materials revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing a satisfactory cytocompatibility. Therefore, the citotoxicity assays suggest that the three epoxy polymers are biocompatible materials.In this paper the in vitro biological properties are presented for three epoxy networks based on diglycidyl ether of bisphenol-A epoxy prepolymer cured with aliphatic amines, namely triethylenetetramine (TETA), 1-(2-aminoethyl) piperazine (AEP) and isophoronediamine (IPD). The biological interactions between the fully-cured epoxy materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented using a UV/VIS spectrometer and SEM analysis. Studies of protein adsorption onto polymeric surfaces showed that the three epoxy materials adsorbed more albumin than fibrinogen. Studies about platelet adhesion and thrombus formation of two epoxy polymers indicated that AEP and IPD network exhibits good hemocompatible behavior. The epoxy materials revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing a satisfactory cytocompatibility. Therefore, the citotoxicity assays suggest that the three epoxy polymers are biocompatible materials.

New trend for epoxy polymers: in vitro biological properties of formulations for medical applications

In this paper the in vitro biological properties are presented for three epoxy networks based on diglycidyl ether of bisphenol-A epoxy prepolymer cured with aliphatic amines, namely triethylenetetramine (TETA), 1-(2-aminoethyl) piperazine (AEP) and isophoronediamine (IPD). The biological interactions between the fully-cured epoxy materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented using a UV/VIS spectrometer and SEM analysis. Studies of protein adsorption onto polymeric surfaces showed that the three epoxy materials adsorbed more albumin than fibrinogen. Studies about platelet adhesion and thrombus formation of two epoxy polymers indicated that AEP and IPD network exhibits good hemocompatible behavior. The epoxy materials revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing a satisfactory cytocompatibility. Therefore, the citotoxicity assays suggest that the three epoxy polymers are biocompatible materials.In this paper the in vitro biological properties are presented for three epoxy networks based on diglycidyl ether of bisphenol-A epoxy prepolymer cured with aliphatic amines, namely triethylenetetramine (TETA), 1-(2-aminoethyl) piperazine (AEP) and isophoronediamine (IPD). The biological interactions between the fully-cured epoxy materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented using a UV/VIS spectrometer and SEM analysis. Studies of protein adsorption onto polymeric surfaces showed that the three epoxy materials adsorbed more albumin than fibrinogen. Studies about platelet adhesion and thrombus formation of two epoxy polymers indicated that AEP and IPD network exhibits good hemocompatible behavior. The epoxy materials revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing a satisfactory cytocompatibility. Therefore, the citotoxicity assays suggest that the three epoxy polymers are biocompatible materials.

Material compósito epóxi-amina para restauração dentária

The aim of this study was to develop composites materials based on diglycidyl ether of bisphenol-A (DGEBA) for applications as dental restorative material for use in fixed prostheses. The composites were formulated by using diglycidyl ether of bisphenol-A (DGEBA) epoxy prepolymer, triethylenetetramine (TETA) isophorone diamine (IPD) and 1-(2-aminoethyl)piperazine (AEP) as hardeners with micro-particles of quartz. The formulations were obtained through the optimization of the systems by methods of chemical titration of the functionality groups, and the incorporation of different amounts of the inorganic material. The formulations were examined by mechanical tests (compression) and in vitro biological tests using chinese hamster ovary cells. The system with AEP shows a bigger deformation after the yield stress. The increase of inorganic material on the composites increases the yield strain and the yield stress. However, it provokes a significant decrease on the rupture resistance value. The composites with TETA and AEP present the best mechanical behaviors. The epoxy polymers revealed no signs of cytotoxicity in the biological tests. The work resulted in new biomaterials with good mechanical and biological properties suitable for the manufacture of prostheses orthodontics and it is easy to manufacture and possesses low cost compared with materials already used.