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.

pH‐sensitive microparticles formed by combination of a synthetic copolymer and sodium alginate in presence of calcium chloride were prepared in mild conditions for specific water‐soluble drug delivery. The copolymers of acryloxyethyl‐trimethylammonium chloride and N ‐vinyl‐2‐pyrrolidone were synthesized by radical polymerization in aqueous solution at 60°C using sodium persulfate as initiator. Fourier transform infrared spectroscopic characterization confirmed the structure of the copolymers and their compositions were determined by potentiometric method. Scanning Electron Microscopy study revealed that microparticles have a rough morphology with size ranging from 450 to 800 µm as measured by optical microcopy. Cefotaxime as a model drug was encapsulated in the microparticles to evaluate the in vitro release behavior under different pH conditions. At physiological temperature, the amount of drug released increased with increasing pH. The amount of drug release from microparticles after 24 h (84%) was more extensive in simulated intestinal fluid when compared with acidic pH environment (20%). These preliminary results suggest that the new microparticles can be used as good candidate for oral drug controlled release in the treatment to colon diseases. POLYM. ENG. SCI., 55:981–987, 2015. © 2014 Society of Plastics Engineers

The aim of the present work was to develop an in situ preparation of chitosan/apatite nanocomposites and evaluate their bioactivity, physiological stability and enzymatic biodegradation. Composites of different chitosan/hydroxyapatite ratios were prepared by wet chemistry using different kinds of chitosan. The method of preparation used to obtain composites in this work could be more attractive with respect to previous procedures because it allows more homogeneous systems and to control the composition and structure of the resulting materials. The bioactivity of the studied material was evidenced by the deposition in its surface of a calcium phosphate layer with apatite morphology after immersion in simulated body fluid (SBF). A higher biodegradation of composites with respect to apatite was obtained due to the presence of chitosan. Also the biodegradability of the composites increased with the chitosan content. Both, biodegradation and bioactivity could be controlled by the molecular weight of chitosan polymer matrix Along the different kinds of chitosan used, a better in vitro biological result was obtained using a chitosan with lower molecular weight. The in vitro biological characteristics of composites indicate that they are promising materials for bone substitution in guided bone regeneration.

Chitosan/apatite (CHI/Ap) composites are attracting great attention as biomaterials for bone repair and regeneration procedures. The reason is their unique set of properties: bioactivity and osteoconductivity provided by Ap and resorbability supplied by CHI among others. Thus, in this study, CHI/Ap and CHI/Si-doped Ap composites were prepared and characterized. Particle size, surface area, in vitro physiological stability, enzymatic biodegradation, and bioactivity were evaluated. Unimodal particle size distribution was obtained for composites with high CHI/Ap ratios while bimodal distribution was present in composites with low CHI/Ap ratio. Physiological stability decreased with Si doping and with the CHI content. Acetylation degree and molecular weight of CHI did not affect in vitro stability. Rate of enzymatic degradation increased with the CHI content in composites. Si-doped Ap composites also showed increased degradation with respect to non-doped ones. The bioactivity of the composites was evidenced by the deposition on their surface of a calcium phosphate layer with Ap morphology after immersion in simulated body fluid. Both, biodegradation and bioactivity were dependent on the molecular weight of the polymeric CHI matrix. These results suggest that the CHI/Ap composites obtained are promising materials for bone regeneration applications.

In the past 20 years, there has been a growing trend towards the development and use of biomaterials for the repairing and restoration of damaged bone tissue. The calcium phosphate bioceramics have attracted great attention in the field of orthopaedics because of its similarity to the mineral component of bone tissue. They have been used as granules for example in non-load bearing small implants, such as middle ear implants, in coatings on metals as dental implants, as well as in porous implants to stimulate bone growth within the implant; and cements, which are implanted in a paste like form and harden in vivo. The clinical disadvantages associated with them are primarily focused on poor mechanical strength and slow resorption kinetics as compared with the surrounding tissue. Therefore, current studies are aimed at creating new formulations combining calcium phosphate compounds with biopolymers, in order to avoid the frequent migration of bioceramic particles from the implant site, reducing potential damage to soft tissue in the vicinity of the implant and to improve biodegradability, curing properties, mechanical strength and injectability. The aims of this paper is to bring a review of the literature concerning chitosan-hydroxyapatite composites for bone restoration, and to mention the main methods of preparation, physico-chemical and biological properties, and tissue engineering techniques using these materials.

En los ultimos 20 anos se observa una tendencia creciente del desarrollo y empleo de biomateriales para la reparacion y regeneracion del tejido oseo danado. Las bioceramicas de fosfatos de calcio han despertado gran interes en el campo de la ortopedia debido a su similitud con el componente mineral del tejido oseo. Estas se han utilizado como granulos en implantes pequenos que no tengan que soportar cargas, como el oido medio; en recubrimientos sobre metales que las refuercen, como los implantes dentales, los implantes porosos para estimular el crecimiento de un hueso dentro del implante, y los cementos que se implantan en estado pastoso y fraguan in vivo. Los inconvenientes clinicos asociados con las bioceramicas se centran fundamentalmente en la pobre resistencia mecanica y la lenta cinetica de reabsorcion en comparacion con el tejido circundante. Es por ello que los estudios actuales estan encaminados a crear nuevas formulaciones compuestas por fosfatos de calcio y biopolimeros, con vistas a evitar la migracion frecuente de las particulas bioceramicas del sitio del implante, disminuir la posibilidad de danos a los tejidos blandos proximos al implante, mejorar la biodegradabilidad, las propiedades de fraguado, la resistencia mecanica y la inyectabilidad de los biomateriales. El objetivo de este articulo es ofrecer una revision de la informacion actualizada sobre materiales compuestos de hidroxiapatita y quitosana como sistemas soporte del tejido oseo; mencionar los principales metodos de preparacion, las propiedades fisico-quimicas y biologicas, y las tecnicas de ingenieria de tejidos que utilizan estos materiales

The objective of this work was to develop nanocrystalline apatite (Ap) dispersed in a chitosan (CHI) matrix as a material for applications in bone tissue engineering. CHI/Ap composites of different weight ratios (20/80, 50/50 and 80/20) and with CHI of different molecular weights were prepared by a biomimetic stepwise route. Firstly, CaHPO(4).2H(2)O (DCPD) crystals were precipitated from Ca(CH(3)COO)(2) and NaHPO(4) in the bulk CHI solution, followed by the formation of CHI/DCPD beads by coacervation. The beads were treated with Na(3)PO(4)/Na(5)P(3)O(10) solution (pH 12-13) to crosslink the CHI and to hydrolyse the DCPD to nanocrystalline Ap. This new experimental procedure ensured that complete conversion of DCPD into sodium-substituted apatite was achieved without appreciable increases in its crystallinity and particle size. In addition, composites with silicon-doped Ap were prepared by substituting Na(3)PO(4) by Na(2)SiO(3) in the crosslinking/hydrolysis step. Characterization of the resultant composites by scanning electron microscopy, X-ray powder diffraction (XRD), thermal analysis and Fourier transform infrared spectroscopy confirmed the formation, within the CHI matrix, of nanoparticles of sodium- and carbonate-substituted hydroxyapatite [Ca(10-x)Na(x)(PO(4))(6-x)(CO(3))(x)(OH)(2)] with diameters less than 20nm. Relatively good correspondence was shown between the experimentally determined inorganic content and that expected theoretically. Structural data obtained from its XRD patterns revealed a decrease in both crystal domain size and cell parameters of Ap formed in situ with increasing CHI content. It was found that the molecular weight of CHI and silicate doping both affected the nucleation and growth of apatite nanocrystallites. These effects are discussed in detail.

Fueron sintetizados varios copolimeros a partir del cloruro de acriloiloxietil-trimetilamonio y el metacrilato de 2-hidroxietilo mediante polimerizacion en solucion a 60 °C usando persulfato de potasio como iniciador. Dichos copolimeros se caracterizaron mediante RMN-1H y RMN-13C y la composicion copolimerica se determino mediante analisis potenciometrico dada la presencia de iones cloruro en la estructura del cloruro de acriloiloxietil-trimetilamonio. La reaccion entre el poli(cloruro de acriloiloxietil-trimetilamonio-co-metacrilato de 2- hidroxietilo) y el alginato de sodio con diferentes composiciones fue seguida mediante medidas de conductividad obteniendose una estequiometria 1:1 para el complejo interpolimerico formado.