Conformation changes of albumin and lysozyme on electrospun TiO2 nanofibers and its effects on MSC behaviors.

Protein adsorption plays a key role in bone repair and regeneration by affecting cell behavior. In this study, TiO2 nanofibers (TiO2 NFs) with different structures, including anatase TiO2 nanofibers (A-NFs), anatase TiO2 nanofibers with beads (B-NFs), anatase-rutile TiO2 nanofibers (AR-NFs) and rutile TiO2 nanofibers (R-NFs), were prepared by electrospinning method. Bovine serum albumin (BSA) and lysozyme (LYZ) were used to explore the adsorption behaviors of TiO2 NFs and then the effects of materials with protein on bone marrow mesenchymal stem cells (MSCs) were studied. Pure titanium metal (PT) was used as control. The results displayed that the adsorption amounts of BSA on samples were B-NFs > AR-NFs > A-NFs ≈ R-NFs > PT, and that for LYZ were B-NFs > AR-NFs > R-NFs > A-NFs > PT. The conformation of proteins changed remarkably when they were adsorbed on meterials. Soaking the TiO2 NFs with and without protein into SBF revealed that the BSA and LYZ on B-NFs, A-NFs and AR-NFs could accelerate the HA deposition on its surface, but it had no promoting effect on HA deposition on B-NFs. MTT and PCR tests showed that the BSA and LYZ adsorbed on materials could promote the proliferation and osteogenic differentiation of MSCs to different degrees due to their different adsorption amount and conformation changes on different TiO2 NFs. The current work demonstrated that the surface properties and crystal structure of TiO2 NFs could influence the adsorption behavior and conformational change of BSA and LYZ, and then further regulate MSCs biological behavior.

Synergistic effects of fibronectin and bone morphogenetic protein on the bioactivity of titanium metal.

To improve the biological properties of bioactive titanium metal, recombinant human bone morphogenetic protein 2(rhBMP-2) and fibronectin (Fn) were adsorbed on its surface solely or contiguously to modify the anodic oxidized titanium (AO-Ti), acid-alkali-treated titanium (AA-Ti), and polished titanium (P-Ti). It is found that the different bioactive titanium surface structures had great influence on protein adsorption. The adsorption amounts of BMP adsorbed solely and Fn/BMP adsorbed contiguously were AA-Ti > P-Ti > AO-Ti, and that for Fn adsorbed solely was AA-Ti ≈ P-Ti > AO-Ti. The conformation of proteins was changed remarkably after the adsorption. For BMP, the α-helix decreased on AA-Ti and stabilized on P-Ti and AO-Ti. For Fn, the ß-sheet on PT-Ti and AA-Ti increased significantly. For Fn/BMP, the percentage of ß-sheet on AA-Ti increased, and that of α-helix on all samples was stable. MSCs showed greater adhesion and spreading on Fn/BMP groups. MTT and Elisa tests showed that the synergistic effects of proteins made the cells proliferate and differentiate faster. It indicated both the surface structure and the synergistic effects of proteins could influence the biological properties of titanium metals. It provides research foundation for improving the biological properties of bioactive titanium metals by simultaneous application of several proteins. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2485-2498, 2017.

Effects of microwave radiation and conductive heating on Tribolium castaneum microstructure.

Microwave radiation and conductive heating were used to completely kill adult Tribolium castaneum (Coleoptera: Tenebrionidae) in wheat flour to protect the flour during storage without significantly effecting its quality. The microstructure of T. castaneum was analyzed to reveal the mechanisms leading to death under microwave and heat treatments. Microwave radiation and conductive heating had different effects on the microstructure of the cuticle of adult T. castaneum and on the ultrastructure of the cells of the epidermis, fat body, and midgut. Both treatments caused a large cavity to appear in the nucleus and the disappearance of mitochondria and the Golgi apparatus. After microwave treatment, there was little change in the surface microstructure but the epidermis was of uneven thickness and the four outer layers of the cuticle were thinner. Nuclear size was essentially unchanged, but fat body cells were fewer and coalesced together. In contrast, conductive heating led to a disordered arrangement of cells on the surface of T. castaneum and indistinct boundaries between layers of the cuticle. The nuclei were enlarged and the fat body cells noticeably fewer and indistinct with a scattered distribution. Thus, microwave treatment produced less severe effects on the surface microstructure and cellular ultrastructure of T. castaneum than did conductive heating. It is concluded that these cellular and surface changes were responsible for the death of T. castaneum.

Studies on fish and pork paste gelation by dynamic rheology and circular dichroism.

The muscle paste of fish, pork, and their mixtures were prepared to study the gelling characteristics by dynamic rheological measurement. The gelation mechanisms of muscle paste were also investigated by circular dichroism. Gel formation of fish paste occurred in 2 steps of 5 to 35 and 51 to 90 degrees C respectively, while pork paste mainly in 1 step of 49 to 72 degrees C. Gel formation was relative to the alpha-helix unfolding of myosin, which responded the melting temperatures of 40 and 50 degrees C for fish myosin and 50 and 60 degrees C for pork myosin, respectively. Alpha-helix unfolding of myosin was beneficial for gel formation. During gel formation, G' of muscle paste was linearly related to alpha-helical content of myosin. The interactions of fish and pork proteins at high temperature (>35 degrees C) could change the gel forming characteristics of muscle paste. Mixed paste exhibited a similar gelation pattern to individual fish paste with 2 visible increases in G'. Addition of pork could suppress the breakdown of fish gel structure at approximately 50 degrees C. Mixing pork and silver carp in a certain ratio could improve the gel properties of silver carp products.