Published 2020 | Version v1
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Synthesis of pH-responsive biodegradable mesoporous silica - calcium phosphate nanoparticles as osteopontin-drug delivery: biomimetic intrafibrillar mineralization of type I collagen

Description

Polymer-Induced Liquid-Precursor (PILP) mineralization concept is based on ions stabilization and subsequent amorphous phase mineral formation by high negative electrical charge polymers, commonly polyaspartic acid (pAsp). In view of excellent results obtained on in vitro studies, the biomaterial development to medical and dental applications based on this process became relevant. However, PILP mineral formation could be negatively affected by physiological environmental changes. Therefore, the aim of this study was to investigate the effect of different pH conditions on the PILP mineralization. In addition, the application of a pH-responsive biodegradable mesoporous silica−calcium phosphate nanoparticle (MSN-CaP) as a PILP-drug delivery system was investigated. Osteopontin (OPN), a highly negatively charged non-collagenous protein with a strong affinity for Ca2+ ions, was used as an inducing agent for PILP-type mineral formation. Particles were synthesized using the modified Stöber method. Morphological characterizations were performed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (MET) and Dynamic Light Scattering (DLS). Elementary analysis was performed by Energy-dispersive X-ray spectroscopy (EDX) and Infrared Spectroscopy (Ftir). Degradation test of MSN-CaP was carried out under different pH conditions (5.5, 6.5, and 7.4) during 48 h by calcium release evaluation (650 nm). Particles were loaded with OPN via impregnation method. The measurement of proteins loaded and released by MSN-CaP was performed using the Lowry method. OPN nanoparticles releasing test was performed in PBS solutions with different pH values (5.5, 6.5 and 7.4). In vitro mineralization tests were performed using type I reconstituted collagen sponges. Mineralizing solution containing 9 mM CaCl2.2H2O and 4.2 mM K2HPO4 was prepared for the experiments under different pH conditions. The collagen samples remained in mineralizing solution (48 h, 37°C) and were characterized using SEM/EDX afterwards. Spherical nanoscale particles (approximately 136.3 nm) were obtained. MSN-CaP showed a pH-dependent behavior during the degradation process. Greater Ca2+ releasing was observed at pH 5.5. Approximately 66% of efficiency in loading the protein with the particles was achieved regardless of protein concentration used in the loading process. The pattern of protein release at the first hour of exposure was similar to the results of Ca2+ release. However, the particles showed the same pattern of OPN release for all pH conditions after the first hour. Intrafibrillar mineralization was observed in the OPN experimental group at pH 7.4. However, osteopontin was not able to induce mineral formation under acidic pH conditions. The MSN-CaP experimental groups showed the same pattern in both pH situations. Therefore, it is concluded that acidic pH conditions negatively influence the OPN-induced mineralization process. Additionally, it is suggested that MSN-CaP can act as an OPN loading agent in different pH situations. (author)

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Additional details

Publishing Information

Imprint Pagination
46 p.
Report number
INIS-BR--23963

INIS

Country of Publication
Brazil
Country of Input or Organization
Brazil
INIS RN
52054087
Subject category
MATERIALS SCIENCE;
Resource subtype / Literary indicator
Thesis
Quality check status
Yes
Descriptors DEI
BIOLOGICAL MATERIALS; DRUG DELIVERY; FOURIER TRANSFORMATION; INFRARED SPECTRA; MINERALIZATION; NANOPARTICLES; POLYMERS; POROUS MATERIALS; PROTEINS; SILICA; X-RAY SPECTROSCOPY;
Descriptors DEC
INTEGRAL TRANSFORMATIONS; MATERIALS; MINERALS; ORGANIC COMPOUNDS; OXIDE MINERALS; PARTICLES; SPECTRA; SPECTROSCOPY; TRANSFORMATIONS;