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.

"Dual-setting" calcium phosphate cements (DS-CPCs), characterized by a polymerization reaction that proceeds along with the conventional hydraulic setting, were prepared and studied. Acrylamide (AA), 2-hydroxyethyl methacrylate (HEMA), and N-vinyl-2-pyrrolydone (VP) in 5, 10, and 20 wt./vol.-% were added to the liquid of α-tricalcium phosphate (α-TCP) and tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/ DCPA) conventional cements. N,N´-methylenebisa-crylamide was used as cross linking agent. N,N,N´,N´-tetramethylethylendiamine in the liquid, and ammonium persulfate in the powder, were employed as polymerization catalyst and initiator, respectively. Diametral tensile strength (DTS), setting time, phase composition, conversion rate, and microstructure of the DS-CPC were compared with those of non-added cements. The DTS increased 22 % for α-TCP and 85 % for TTCP/DCPA DS-CPCs by adding 20 wt./vol.-% AA. The HEMA and VP had no positive effect on DTS. The extent of the hydraulic setting reaction for α-TCP DS-CPC was only slightly decreased by the addition of 20 wt./vol.-% of AA to the mixing liquid.

Os compósitos de Al2O3/ZrO2 são indicados para desempenhar funções estruturais dentro do organismo em decorrência de suas qualidades mecânicas, podendo ser otimizados mediante a obtenção de uma camada de material bioativo. O método biomimético propõe a obtenção dessa camada mediante a utilização de solução sintética que simula o plasma sanguíneo. Porém, isso não impede que a presença desses materiais no corpo interfira no mecanismo de defesa, além de influenciar nas doses de antibióticos necessárias. Uma maneira de prevenção e tratamento de infecções microbianas é a utilização de sais de prata, neste caso sendo incorporados juntamente com a camada usada. O presente trabalho otimizou o processamento de compósito ZTA (alumina tenacificada por zircônia ) e da obtenção da camada com características bioativas e bactericidas. O método de produção, bem como de recobrimento dos compósitos, foram eficientes nas condições estudadas e a morfologia da camada bioativa sofreu alteração quando imersa na solução de AgNO3, apresentando a formação de fosfato de prata.

Al2O3/ZrO2 composites are indicated to play structural functions inside the organism due to their mechanical qualities, being able to be optimized by means of the attainment of a layer of bioactive material. The biomimetic method considers the attainment of this layer using a synthetic solution that simulates the body fluid. However, this does not prevent that these materials in the body interfere with the defense mechanism, besides influence in the necessary doses of antibiotics. A way of prevention and treatment of bacterial infections is the use of silver salts, in this case being incorporated to the coating. The present work optimized the processing of zirconia-toughened alumina (ZTA) composites with bioactive and bacterial characteristics. The production method, as well as the implant coatings, had been efficient in the studied conditions and the morphology of the bioactive layer on the composite suffered alteration when immersed in the AgNO3 solution, with the formation of silver phosphate.