Construction and Evaluation of Alginate Dialdehyde Grafted RGD Derivatives/Polyvinyl Alcohol/Cellulose Nanocrystals IPN Composite Hydrogels.

To enhance the mechanical strength and cell adhesion of alginate hydrogel, making it satisfy the requirements of an ideal tissue engineering scaffold, the grafting of Arg-Gly-Asp (RGD) polypeptide sequence onto the alginate molecular chain was conducted by oxidation of sodium periodate and subsequent reduction amination of 2-methylpyridine borane complex (2-PBC) to synthesize alginate dialdehyde grafted RGD derivatives (ADA-RGD) with good cellular affinity. The interpenetrating network (IPN) composite hydrogels of alginate/polyvinyl alcohol/cellulose nanocrystals (ALG/PVA/CNCs) were fabricated through a physical mixture of ion cross-linking of sodium alginate (SA) with hydroxyapatite/D-glucono-δ-lactone (HAP/GDL), and physical cross-linking of polyvinyl alcohol (PVA) by a freezing/thawing method, using cellulose nanocrystals (CNCs) as the reinforcement agent. The effects of the addition of CNCs and different contents of PVA on the morphology, thermal stability, mechanical properties, swelling, biodegradability, and cell compatibility of the IPN composite hydrogels were investigated, and the effect of RGD grafting on the biological properties of the IPN composite hydrogels was also studied. The resultant IPN ALG/PVA/CNCs composite hydrogels exhibited good pore structure and regular 3D morphology, whose pore size and porosity could be regulated by adjusting PVA content and the addition of CNCs. By increasing the PVA content, the number of physical cross-linking points in PVA increased, resulting in greater stress support for the IPN composite hydrogels of ALG/PVA/CNCs and consequently improving their mechanical characteristics. The creation of the IPN ALG/PVA/CNCs composite hydrogels' physical cross-linking network through intramolecular or intermolecular hydrogen bonding led to improved thermal resistance and reduced swelling and biodegradation rate. Conversely, the ADA-RGD/PVA/CNCs IPN composite hydrogels exhibited a quicker degradation rate, attributed to the elimination of ADA-RGD by alkali. The results of the in vitro cytocompatibility showed that ALG/0.5PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels showed better proliferative activity in comparison with other composite hydrogels, while ALG/PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels displayed obvious proliferation effects, indicating that PVA, CNCs, and ADA-RGD with good biocompatibility were conducive to cell proliferation and differentiation for the IPN composite hydrogels.

Development of a novel thermostable Newcastle disease virus vaccine vector for expression of a heterologous gene.

Thermostable Newcastle disease virus (NDV) vaccines have been used widely to control Newcastle disease for village poultry flocks, due to their independence of cold chains for delivery and storage. To explore the potential use of thermostable NDV as a vaccine vector, an infectious clone of thermostable avirulent NDV strain TS09-C was developed using reverse genetics technology. The GFP gene, along with the self-cleaving 2A gene of foot-and-mouth disease virus and ubiquitin monomer (2AUbi), were inserted immediately upstream of the NP (nucleocapsid protein), M (matrix protein) or L (large polymerase protein) gene translation start codon in the TS09-C infectious clone. Detection of GFP expression in the recombinant virus-infected cells showed that the recombinant virus, rTS-GFP/M, with the GFP gene inserted into the M gene expressed the highest level of GFP. The rTS-GFP/M virus retained the same thermostability, growth dynamics and pathogenicity as its parental rTS09-C virus. Vaccination of specific-pathogen-free chickens with the rTS-GFP/M virus conferred complete protection against virulent NDV challenge. Taken together, the data suggested that the rTS09-C virus could be used as a vaccine vector to develop bivalent thermostable vaccines against Newcastle disease and the target avian diseases for village chickens, especially in the developing and least-developed countries.

Nano-SiO2 reinforced alginate-chitosan-gelatin nanocomposite hydrogels with improved physicochemical properties and biological activity.

Alginate (Alg) hydrogels possess desirable advantages for application in tissue engineering; however, they are limited by their weak mechanical properties, poor chronical stability in phosphate buffered saline, and absence of mammalian cell recognition sites, severely restricting their biomedical applications. To overcome these limitations, we integrated Alg hydrogels with nano-silica (SiO2) to produce nano-SiO2 reinforced Alg-chitosan-gelatin nanocomposite hydrogels (Alg/SiO2-CHI-GA NCH) for biomedical purposes, utilizing Chitosan (CHI) and gelatin (GA) in an alternate electrostatic adsorption. Specifically, we investigated the regulatory and promotional effects of the nano-SiO2 on the morphological structure, mechanical properties, thermal stability, rheological properties, swelling, biodegradability, biomineralization and cytocompatibility of the resultant Alg/SiO2-CHI-GA NCH. The experimental findings demonstrate that the constructed Alg/SiO2-CHI-GA NCH exhibited uniform morphology and a regular structure. Upon freeze-drying, the internal cross-sections of the NCH exhibited a honeycomb porous structure. Furthermore, the physicochemical properties and biological activities of the prepared Alg/SiO2-CHI-GA NCH were regulated to some extent by nano-SiO2 content. Notably, nano-SiO2 inclusion enhanced the attachment and viability of MG63 and MC3T3-E1 cells and induced three-dimensional cell growth in ALG/SiO2-CHI-GA NCH. Among the fabricated NCH, Alg/SiO2-CHI-GA NCH with 0.5% and 1.0% (w/v) nano-SiO2 exhibited significant proliferative activity, which is attributable to their high porosity and uniform cell adhesion. Furthermore, the alkaline phosphatase activity in the cells gradually increased with increasing of nano-SiO2 amount, indicating the favorable effect of nano-SiO2 on the osteogenic differentiation of MG63 and MC3T3-E1 cells. Our study findings provide a comprehensive foundation for the structural- and property-related limitations of Alg hydrogels in biomedicine, thereby expanding their potential applications in tissue engineering.

Improved stability of liposome-stabilized emulsions as a co-encapsulation delivery system for vitamin B2, vitamin E and ß-carotene.

To realize the co-encapsulation of multiple nutraceuticals with different solubilities, Pickering emulsions stabilized by freshly-prepared liposome suspension stabilized emulsion (Fre-Lip-Sus-E) and hydrated lyophilized liposome stabilized emulsion (Hyd-Lyo-Lip-E) were prepared, in comparison with the phospholipid stabilized emulsion (Pho-E). The particle size, zeta-potential, emulsification activity (EAI), emulsion stability (ESI), morphology, environmental stability and rheological properties of the three emulsions were compared. In addition, the in vitro digestive stability and bioaccessibility of three emulsions loaded with vitamin B2, vitamin E and ß-carotene were assessed. The results showed that the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E were characterized by smaller particles and higher environmental stability than the Pho-E. The slight difference between the Hyd-Lyo-Lip-E and Fre-Lip-Sus-E might be due to the partial destruction of the phospholipid bilayer during the lyophilization of lyophilized liposomes. Rheological analysis demonstrated that all emulsions had high interfacial viscosity and significant shear thinning characteristics of pseudoplastic fluids. Compared with the Pho-E, the liposome-stabilized emulsions demonstrated good environmental stability and antioxidant properties, and the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E exhibited comparable stabilising effects. Higher bioaccessibility of vitamin B2 and vitamin E in the Fre-Lip-Sus-E and Hyd-Lyo-Lip-E was observed, while ß-carotene had higher bioaccessibility in Pho-E. These results provide valuable insight into the potential for designing emulsion co-encapsulation delivery systems using liposomes as stabilizers.