Resumo Microesferas de α-TCP foram obtidas atomizando uma suspensão aquosa contendo 50% em massa de α-TCP com baixa cristalinidade e 1% em massa de ácido cítrico. Poli(etileno glicol) e poli(álcool vinílico) foram testados como ligantes. O processo de spray drying resultou em microesferas com diâmetros médios de aproximadamente 20 μm e esfericidade (razão de comprimentos na horizontal e na vertical) próxima a um, características essenciais para várias aplicações, como a liberação controlada de drogas e cimentos ósseos injetáveis. A adição dos ligantes foi necessária para reduzir a quantidade de partículas soltas e aumentar a fluidez do pó, mas também resultou em uma redução na molhabilidade e na área superficial das microesferas. Os melhores resultados foram obtidos com 3% de PVA já que as microesferas apresentaram a maior área superficial, molhabilidade e esfericidade. As microesferas preparadas neste estudo podem ser utilizadas como precursoras de cimentos ósseos injetáveis, já que a sua geometria esférica e sua fluidez favorecem a homogeneidade e injetabilidade das pastas sobrepujando as principais dificuldades dos cimentos injetáveis atuais.

Abstract a-TCP microspheres were obtained by atomizing aqueous slurries containing 50 wt% of low crystallinity α-TCP and 1 wt% of citric acid. Poly(ethylene glycol) and poly(vinyl alcohol) were tested as a binder. The spray drying process yielded to microspheres with mean diameter around 20 μm and sphericity (horizontal and vertical length ratio) closest to one, which is essential to many applications, such as drug delivery and injectability of cements. The addition of binders was necessary to decrease the amount of loose particles and to improve powder flowability but it also caused a reduction in wettability and surface area. Best results were achieved with 3 wt% of PVA, as the microspheres presented the highest specific surface area, wettability, and sphericity. The microspheres prepared in this study may be used as injectable bone cements precursor since their geometry and flowability would favor paste homogeneity and injectability overcoming many drawbacks of today’s injectable bone cements.

Calcium phosphate cements (CPCs) have potential to be used on repairing damaged bones due to their moldability, bioactivity and bioresorbability. These materials combine calcium orthophosphate powders with a liquid leading to a paste that hardens spontaneously at low temperatures. Hence, CPCs could be applied as scaffolds to support cell/tissue growth. This paper studies CPC scaffolds processing by foaming cement's liquid phase in which was added gelatin and chitosan. The former acted to increase the foam stability while the ladder acted as a foaming agent. Moreover, these polymers would enhance scaffold's biological properties by controlling material's total porosity and in vivo resorption. The method proposed led to scaffolds with 58.71% porosity with sizes ranging from 160 to 760 µm and compressive strength of 0.70MPa. After foaming, pores' size, distribution and interconnectivity changed significantly leading to a material that could be applied on bone regeneration since it would allow nutrient's transport, cell attachment and an increase in material degradation rate.