High efficient strategy for the production of hydroxyapatite/silk sericin nanocomposites

Abstract

BACKGROUND: 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.

Continuous Production of Highly Tuned Silk/Calcium-Based Composites: Exploring New Pathways for Skin Regeneration

“…CaP that is synthetized using wet chemical precipitation and physiological conditions of temperature (37 °C) and pH (6–9) often results in HAp particles with poor crystallinity [ 3 , 13 , 25 , 26 ]. CaP-SS-Ce particles have an amorphous structure, since no peaks were identified ( Table 2 , Figure 1 ).…”

“…Regarding size and morphology, TEM ( Figure 2 ) evidences the size and the morphology of primary CaPs particles. CaP1-nano is composed of aggregated nanoparticles in the form of rods similar to other HAp particles obtained using wet chemical precipitation [ 3 , 12 , 13 , 30 ]. Similar nanorods organized in microcapsules are present in commercial HAp.…”

“…The effectiveness of cell attachment and proliferation on CaP composite particles highly depends on their physicochemical characteristics, which in turn is directly dependent on the processing strategy. Continuous flow regimes operated through oscillatory flow reactors (OFRs) provided with smooth periodic constrictions (SPCs) improved mixing efficiency and mass transfer processes in multiphase systems, generating a product with uniform and controlled characteristics [ 12 , 13 ]. The liquid or multiphase fluid is typically oscillated in the axial direction and this motion interacts with the SPCs forming vortices, the mixing intensity being controlled by the oscillation frequency ( f ) and amplitude ( x 0 ) [ 12 , 14 ].…”

An update on hydroxyapatite/collagen composites: What is there left to say about these bioinspired materials?

“…Low crystallinity and a partially carbonated structure is also typical of biological HAp. 4 However, the use of HAp has limitations due to its low toughness and poor mechanical resistance under complex stress states, characteristic of most ceramics, which increases the risk of fracture and limits the clinical applications of this material. Thereby, the preparation of HAp composites for bone regeneration has several advantages, namely, the possibility of improving HAp properties, such as mechanical strength and biological response.…”

“…Special attention has been given to nano‐HAp because of its similarity in size, crystallinity, and chemical composition with bone, which is characterized by rod‐like or needle‐like structures with a size that can vary from several nm to more than 100 nm. Low crystallinity and a partially carbonated structure is also typical of biological HAp 4 …”