Conformational changes induced by cellulose nanocrystals in collaboration with calcium ion improve solubility of pea protein isolate.

The low solubility of pea protein isolate (PPI) greatly limits its functional properties and its wide application in food field. Thus, this study investigated the effects and mechanisms of cellulose nanocrystals (CNC) (0.1-0.4 %) and CaCl2 (0.4-1.6 mM) on the solubility of PPI. The results showed that the synergistic effect of CNC (0.3 %) and Ca2+ (1.2 mM) increased the solubility of PPI by 242.31 %. CNC and Ca2+ changed the molecular conformation of PPI, enhanced intermolecular forces, and thus induced changes in the molecular morphology of PPI. Meanwhile, the turbidity of PPI decreased, while surface hydrophobicity, the absolute zeta potential value, viscoelasticity, ß-sheet ratio, and thermal properties increased. CNC bound to PPI molecules through van der Waals force and hydrogen bond. Ca2+ could strengthen the crosslinking between CNC and PPI. In summary, it is proposed a valuable combination method to improve the solubility of PPI, and it is believed that this research is of great significance for expanding the application fields of PPI and modifying plant proteins.

Remodeling mechanism of gel network structure of soy protein isolate amyloid fibrils mediated by cellulose nanocrystals.

The differences in the gelling properties of soy protein isolate (SPI) and soy protein isolate amyloid fibrils (SAFs) as well as the role of cellulose nanocrystals (CNC) in regulating their gel behaviors were investigated in this study. The binding of CNC to ß-conglycinin (7S), glycinin (11S), and SAFs was predominantly driven by non-covalent interactions. CNC addition reduced the particle size, turbidity, subunit segments, and crystallinity of SPI and SAFs, promoted the conversion of α-helix to ß-sheet, improved the thermal stability, exposed more tyrosine and tryptophan residues, and enhanced the intermolecular interactions. A more regular and ordered lamellar network structure was formed in the SAFs-CNC composite gel, which could be conducive to the improvement of gel quality. This study would provide theoretical reference for the understanding of the regulatory mechanism of protein amyloid fibrils gelation as well as the high-value utilization of SAFs-CNC complex as a functional protein-based material or food ingredient in food field.

[In vitro evaluation of the function of sheet biomaterials in platelet activation].

In China, the evaluation of hemocompatibility of biomaterials is limited to hemolysis, coagulation time,and the number and morphology of platelets adhered on biomaterials. The present research, however, is aimed to establish a method for evaluating the function of sheet biomaterials in platelet activation. Platelet activation caused by glass, polyvinyl chloride or polymethylvinylsiloxane sheets was evaluated by measuring alpha-granule membrane protein (GMP-140) in platelet poor plasma, using a reasonable blood-material contact model vibrating at different speed. The result showed that the difference in platelet activation was not significantly different among the three above-mentioned materials at 140r/m or 200r/m. However, when it comes to 230r/m, significant difference was observed among these three groups, with glass > polyvinyl chloride > polymethylvinylsiloxane. But the order was reversed at 270r/m, which may be due to the different interfacial tension of different materials. Therefore, the method is suitable to evaluate platelet activation caused by sheet biomaterials, but an appropriate vibrating speed should be chosen. The interfacial tension plays an important role in the model and should be considered for results assessment.

[Study and evaluation on hemocompatibility of biomaterials].

Hemocompatibility is an important component of biocompatibility; it reflects the degree of interaction between material and blood. Hemocompatibility is multifaceted, so that the material's impact on the blood and the underlying mechanism are very complicated. This article presents a review of researches probing the impact of material on blood via contact activation and plasma protein adsorption; via the platelet activated and the formation of thrombin; via the complement system activated and the activation of leukocytes as well as other mechanisms of hemolysis. The current methods for evaluation and the future trend of development are also introduced.

[In-vitro evaluation of haemocompatibility of biomaterials].

In-vitro test is usually conducted as a preliminary screening test in the evaluation of the haemocompatibility of biomaterials for its short-term consuming, convenience and less expense. The selection of appropriate model for blood-biomaterial interaction, the choice of sensitive and specific parameters, and the minimization of additional blood activation are most important in the in-vitro test. In addition, the time and the style of blood-biomaterial interaction, the choice of sensitive and specific parameters, and the minimization of additional blood activation are most important in the in-vitro test. In addition, the time and the style of blood-biomaterial interaction, the selection of primary reference materials and the shear rate should be considered. In recent years, though great progress has been made in the in-vitro evaluation of haemocompatibility of biomaterials, all these influencing factor should be standardized for more effective evaluation of the haemocompatibility of biomaterials.

Evaluation of a bioactive bone-inducing material consisting of collagen scaffolds and collagen-binding bone morphogenetic protein 2.

Bioactive bone-inducing material (BBIM) is a collagen-based scaffold composed of demineralized bone matrix and collagen-binding domain bone morphogenetic protein 2 (BMP-2). BBIM is regarded as a promising bone-inducing scaffold to repair bone defects. In this work, we evaluated the biocompatibility and osteogenecity of BBIM. Using enzyme-linked immunosorbent assay, the level of BMP-2 on BBIM was detected and considered adequate. Kunming mice were used as the animal model to investigate the acute systemic toxicity, long-term bone regeneration, ectopic bone formation, and chronic systemic toxicity. Results show that BBIM induced no serious inflammatory reaction or acute and chronic systemic toxicity. Our analyses also demonstrated significant homogeneous ectopic bone formation as well as significantly high numbers of erythrocytes in the BBIM groups in the chronic systemic toxicity study, a phenomenon which may provide indirect proof of the bone regeneration capacity of BBIM, which may be considered as a bioactivity indicator in future studies.

Immobilized heparin and its anti-coagulation effect on polysulfone membrane surface.

Polysulfone has been widely used as hemodialysis membrane material because of its excellent physiochemical performance. There is still a need to further improve its anti-coagulation property in clinical practice. In this work, we covalently immobilized heparin onto polysulfone membrane to improve its anti-coagulation performance. Low temperature plasma technique with environmentally friendly nitrogen as the gas source, as well as N-ethyl-N'-[3-dimethylaminopropy] carbodiimide hydrochloride/hydroxy-2,5-dioxopyrolidine-3-sulfonicacid sodium chemistry were utilized to immobilize heparin onto the surface of polysulfone membrane. X-ray photoelectron spectroscopy, attenuated total reflectance Fourier-transform infrared spectroscopy, as well as water contact angle results confirmed successful binding of heparin to the membrane surface. Only slight permeability differences were observed between the immobilized surface and the unmodified surface, while the polysulfone membrane had become more hydrophilic after immobilization. The blood coagulation time was greatly prolonged after modification and less platelets adhesion was observed on the heparin immobilized surface. Also, compared with heparin injection doses in clinical, the heparinized process in our work consumed less heparin. Our study suggests that the immobilized heparin has local anti-coagulation effect, while reducing the doses.