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- High efficient strategy for the production of hydroxyapatite/silk sericin nanocompositesPublication . Veiga, Anabela; Castro, Filipa; Oliveira, Ana L.; Rocha, FernandoBACKGROUND: Sericin (SS) induces nucleation of bone-like hydroxyapatite (HAp) when used as an organic matrix. HAp/SS nanocomposites have been conventionally synthesized through precipitation in stirred tank reactors (STs). Despite its simplicity, this process is time consuming and presents difficulties in scale-up. In our study, HAp/SS nanocomposites were successfully synthesized in a ST and in a meso-oscillatory flow reactor (meso-OFR), to compare the efficiency of both reactors and to study HAp mineralization using SS as a template. RESULTS: The production of stable HAp, indicated by pH stabilization, was achieved after 180 min in the ST and after 30 min in the meso-OFR. X-ray diffraction and Fourier transform infrared analyses showed that the particles obtained in both reactors are HAp/SS nanocomposites with low crystallinity. Scanning electron microscopy evidenced the formation of rod- and plateshaped nanoparticles and revealed that the presence of SS led to the production of larger particles. The latter observation was confirmed by laser diffraction. Additionally, increasing SS concentration resulted in the formation of more plate-like particles. CONCLUSIONS: Precipitation is more efficient in the meso-OFR, HAp/SS being obtained four times faster. The presence and concentration of SS led to differences in the size and morphology of the synthesized particles, suggesting a critical role of SS in the mineralization process. This work reports a new approach for the manufacture of high-added-value nanocomposites with similar characteristics to biological bone and the results of a study of the influence of SS as an organic component in HAp nucleation. Further, the use of this protein and technology leads to significant waste minimization.
- Protein-based Hydroxyapatite materials: tuning composition towards biomedical applicationsPublication . Veiga, Anabela; Castro, Filipa; Rocha, Fernando; Oliveira, AnaSynthetic hydroxyapatite (HAp) has been successfully produced with the aim of obtaining biomaterials that meet the biomechanical requirements for bone tissue engineering while being compatible with the surrounding biochemical and cellular environment. Combining proteins with HAp can generate improved composite biomaterials, which are environmentally friendly, renewable and biocompatible. In this context, HAp/protein-based composite materials have been widely exploited since the late 20th century to the present day. In this review, we explore the biomedical relevance of the association of HAp with several proteins of interest such as fibroin, sericin, fibrin and keratin. The processing strategies for their synthesis and effect on the obtained shape and physicochemical, mechanical and biological performance are herein discussed. This work can provide useful information for the design of HAp-based biomaterials with specific emphasis on bone tissue regeneration characteristics for biomedical applications.