Resumo Objetivou-se desenvolver, caracterizar e avaliar in vitro biomateriais compósitos de quitosana com hidroxiapatita (CHI/HA) para atuarem como substitutos ósseos. As quitosanas de baixa (L-CHI) e média (M-CHI) massa molecular foram previamente caracterizadas por gravimetria, viscosimetria e espectrofotometria ultravioleta. Os compósitos de CHI/HA foram produzidos por precipitação in situ, seguida de centrifugação (micropartículas) ou spray drying (nanopartículas), e caracterizados por microscopia eletrônica de varredura, espectroscopia de infravermelho com transformada de Fourier e difração de raios X. A citotoxicidade in vitro foi determinada por teste de viabilidade celular. L-CHI e M-CHI apresentaram, respectivamente, 15,7% e 16,4% de umidade, 0,51% e 0,18% de cinzas, 79,5% e 77,7% de grau de desacetilação e 4,18.104 e 17,3.104 de massa molecular média viscosimétrica. Os compósitos exibiram grupos característicos dos materiais de origem e escassa citotoxicidade. Concluiu-se que as técnicas foram eficazes para produção dos biomateriais, com características físico-químicas e biológicas adequadas para utilização nas terapias ósseas.

Abstract It was aimed to develop, characterize and evaluate in vitro the biomaterial composites of chitosan with hydroxyapatite (CHI/HA) to be applied as bone substitutes. Chitosans of low (L-CHI) and medium (M-CHI) molecular weight were previously characterized by the gravimetry, viscosimetry and ultraviolet spectrophotometry. The composites of CHI/HA were produced by in situ precipitation, followed by centrifugation (microparticles) or spray drying (nanoparticles), and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray diffraction. In vitro cytotoxicity was determined by the cell viability test. The L-CHI and M-CHI presented, respectively, 15.7% and 16.4% of humidity, 0.51% and 0.18% ash, 79.5% and 77.7% deacetylation degree, and 4.18x104 and 17.3x104 mean molecular weight by viscosimetry. The composites exhibited characteristic groups of the source materials and scarce cytotoxicity. It was concluded that the techniques were effective for the production of biomaterials, with adequate physicochemical and biological characteristics for use in bone therapies.

Some chemical properties of metal adsorption by chitosan are evaluated in this research work. Thus, the power of chitosan adsorption by Cu2+ metallic ion was comparatively studied at different pH values and stirring times. The adsorbed Cu2+ ion content was determined by atomic absorption, pH 5 being the most appropriate one for its adsorption. On the other hand, several trials were performed to analyze the possibility of chitosan to protect tomato plantlets from toxic levels of Cu2+, so proving a bigger root growth and a height decrease of plants treated with the product, effects counteracting toxicity by Cu2+.

En este trabajo se evalúan algunas de las propiedades químicas de la adsorción de metales por quitosana. Para ello se estudió comparativamente el poder de adsorción de la quitosana con el ion metálico Cu2+ a diferentes pH y tiempos de agitación. El contenido de ion Cu2+ adsorbido se determinó por absorción atómica, siendo el pH 5 el más adecuado para su adsorción. Por otra parte, se realizaron ensayos analizando la posibilidad de que la quitosana pudiera proteger a plántulas de tomate cultivadas con niveles tóxicos de Cu2+, evidenciándose un mayor crecimiento radical y una disminución de la altura de las plantas tratadas con el producto, efectos que contrarrestan el efecto de la toxicidad por Cu2+.

The kinetic study of the photopolymerisation of gels of acrylic acid (AA) and chitosan (CHI) prepared by three different methods was accomplished. The kinetic parameters such as conversion and polymerisation rate were determined. The influence of the composition and the preparation method on these parameters was elucidated. The effect of the mixing order on the formation of chitosan-acrylic acid complexes (CHI+AA-) was determined by measuring the viscosity of non-polymerised gels. The presence of polyacrylic acid (PAA) grafted on to a CHI matrix after photopolymerisation and the influence of the method of preparation and feed composition on the proportion of CHI-PAA interpolymer network were demonstrated by FTIR spectroscopy. The possible mechanism of the graft copolymerisation is discussed in detail.

Copolymers of furfuryl methacrylate (M) with N-vinyl-2-pyrrolidone (P) were prepared by free radical copolymerization in DMF solution at 50°C, using 2,2'-azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were calculated according to the general copolymerization equation using the Fineman-Röss and Kelen-Tüdos linearization methods, as well as the Tidwell-Mortimer non linear least-squares treatment and the Monte Carlo random method. The values of the reactivity ratios calculated using the first methodology were rM = 3.92 and rP = 0.004. Similar results were obtained by both, the Monte Carlo and the non-linear least square techniques that certified the precision of the proposed method. The microstructure of copolymer chains based on the first order Markov statistics is described.

Copolymers of furfuryl acrylate (A) with 2-hydroxyethyl methacrylate (H) were prepared by free radical copolymerization in DMF solution at 50°C, using 2,2'-azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of both monomers were calculated according to the general copolymerization equation using the Fineman-Röss and Kelen-Tüdos 1inearization methods, as well as the Tidwell-Mortimer non linear least-squares treatment and the Monte Carlo random method. The reactivity ratios obtained were rA = 0.93 and rH = 1.42. Similar results were obtained by both, the Monte Carlo and the non-linear least squares methods. The microstructure of copolymer chains based on the first order Markov statistics is described.