Navegando por Palavras-chave "Spray Drying"

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    Grânulos De Fosfato De Cálcio Co-Dopado Com Silício E Estrôncio: Estudo Da Injetabilidade Do Cimento Ósseo E Aplicação Na Manufatura Aditiva
    (Universidade Federal de São Paulo (UNIFESP), 2017-07-24) Reno, Caroline De Oliveira [UNIFESP]; Motisuke, Mariana [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The persuit for injectable biomaterials to repair the bone tissue has increased in recent years, since they offer several benefits to the patient, such as: faster bone repair and patient recovery, smaller incisions and shorter hospital stay, which, besides of reducing the risks of infection, decreases the health costs. In this context, it is relevant to develop injectable materials that are able to suit any bone defect and present good biocompatibility. Calcium phosphate cements (CPCs) is suitable to be applied in minimally invasive procedures for bone repairs, since they have the ability to form a moldable and/or injectable paste that hardens spontaneously ensuring stability to the implantation site, and when injected directly into the bone defect may provide benefits in several clinical situations. In addition, cements based on ionic substituted calcium phosphate may have their chemical, physical and biological properties optimized. Substitution with silicon, for example, decreases the thermal stability of the a -TCP phase, precursor powder of the cement; and the substitution with strontium has beneficial effects on bone regeneration. Notwithstanding, the development of injectable calcium phosphate cements (CPCs) presents some challenges such as to avoid phases segregation during injection, regardless of the applied force; needle clogging and; low mechanical strength and cohesion of the material after application. Injectability and cohesion of CPC pastes could be improved by the use of round particles, which could be easily obtained by spray drying, and the addition of viscous polymers. Through these strategies, in addition to improving the flowability of the powder and paste, others CPC properties, such as compressive strength, could be enhanced. Therefore, in this work it was studied the influence of atomization and ionic substitution on the injectability, compressive strength and microstructure of the bone cements, obtained from four different calcium phosphates: I) a-TCP (TCP); II) Sr, Si-a-TCP (TCP_D); III) atomized a-TCP (TCP_A) and; IV) atomized Sr, Si-a- TCP (TCP_DA). The atomization process lead to an unquestionable enhancement on the cement properties, such as: better injectability, higher mechanical strength and higher surface area, an important parameter to improve the biological behavior, since it increases the available surface for cellular and/or tissue interaction. Moreover, due to atomization, the liquid-to-powder ratios could be decreased resulting in cements with even higher mechanical behavior. The addition of carboxymethylcellulose was necessary in order to reduce the cohesion time, making this material an excellent candidate in order to permit cement’s use in minimally invasive surgeries, ie the polymer increased the material cohesiveness. Furthermore, the ionic substitution had a significant effect on the setting reaction, retarding the a-TCP hydrolysis, whereas for the cement made from TCP_D, even after seven days of immersion in Ringer ®, calcium deficient hydroxyapatite was not formed. Nevertheless, when the precursor powder was TCP_DA, the setting reaction even though slow, was possible, but due to the long setting times, has avoided its application as injectable material. In addition, the doped cements exhibited a lower mechanical strength probably due to less efficient entanglement of the precipitated crystals as a result of the slower setting reaction. Nevertheless, these doped cements are still good candidates for bone replacement, if they are applied as ready-made pieces, since they have mechanical resistance in the range of cancellous bone. In addition to the application of cement pastes as injectable material, the pastes could also be employed as "inks" for application in additive manufacture, by robocasting technique. Thus, from the results obtained for the moldable cements, it was possible to determine favorable conditions to apply on the development of CPC scaffolds by robocasting. CPC scaffolds were obtained by robocasting in a BCN3D + Reprapbcn machine that prints 3D parts by injecting pastes ("inks") following a 3D model made in a CAD software. TCP_A and TCP_DA pastes were tested, as well as different cement consolidation processes, resulting in scaffolds with different combinations of crystalline phases. The obtained scaffolds presented macroporosity and interconnectivity between the pores. They are potential materials to be applied in replacement of cancellous bone, and with the advantage of being printed at any geometry.
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    Injetabilidade De Grânulos De β-Tcp E Wollastonita Obtidos Pelo Método De Spray Drying Para Preenchimento De Defeito Ósseo
    (Universidade Federal de São Paulo (UNIFESP), 2017-05-29) Almeida, Gleice Ellen Morais De [UNIFESP]; Motisuke, Mariana [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The need for biomaterials to treat bone defects is growing considerably. Thereby, the importance of studies that seek alternatives to treat bone tissue and postpone the need for more severe surgeries increases every day. To this end, the use of bioceramics, such as calcium silicates (wollastonite - CaSiO3) and β-TCP becomes interesting since they are bioactive and osteoconductive. There are many studies in the literature evaluating the possibility of using these bioceramics for filling bone defects. Therefore, the production of granules with controlled shape and porosity becomes interesting since it may allow cell adhesion, assist bone growth and facilitates the filling of an irregular defect. The granules can be obtained by spray drying, which is a granulation process widely used in industry and, in the last recent years, this process has been used to the manufacture of granules for biomedical applications because it is a versatile process that allows the production in a large scale, with low risk of contamination and high reproducibility. The application of granules for filling bone defects through minimally invasive surgical techniques becomes interesting since its spherical morphology improves the fluidity of the material and, consequently, improves the injectability of the material. The use of minimally invasive surgical techniques allows quick recovery of the paicent due to rapid bone repair and more simple procedures. From this context, the objective of this work is to obtain and characterize wollastonite and β-TCP granules obtained by the spray drying process to be applied in bone defects by means of minimally invasive techniques. It was possible to obtain cohesive granules when using β-TCP and calcium silicate samples with PEG binder. It was possible to obtain spherical granules and with high fluidity when using gelatin as a binder. The mixture of granules and with a sodium alginate solution lead to an injectable paste, which was homogenized by two different mixing methods, amalgamator and glass plate. After mixing, it observed greater presence of intact granules when the paste was mixed in the glass plate. Injectable pastes obtained by calcined granules and a polymer phase with lower viscosity favored the injectability and cohesion of the paste, becoming the best condition analyzed. The calcination of the granules resulted in higher mechanical properties and, consequently, granules integrity after mixing and injection, being the best condition to be used.