Weilin Yu

A Novel Albumin-Based Tissue Scaffold for Autogenic Tissue Engineering Applications

Tissue scaffolds provide a framework for living tissue regeneration. However, traditional tissue scaffolds are exogenous, composed of metals, ceramics, polymers, and animal tissues, and have a defined biocompatibility and application. This study presents a new method for obtaining a tissue scaffold from blood albumin, the major protein in mammalian blood. Human, bovine, and porcine albumin was polymerised into albumin polymers by microbial transglutaminase and was then cast by freeze-drying-based moulding to form albumin tissue scaffolds. Scanning electron microscopy and material testing analyses revealed that the albumin tissue scaffold possesses an extremely porous structure, moderate mechanical strength, and resilience. Using a culture of human mesenchymal stem cells (MSCs) as a model, we showed that MSCs can be seeded and grown in the albumin tissue scaffold. Furthermore, the albumin tissue scaffold can support the long-term osteogenic differentiation of MSCs. These results show that the albumin tissue scaffold exhibits favourable material properties and good compatibility with cells. We propose that this novel tissue scaffold can satisfy essential needs in tissue engineering as a general-purpose substrate. The use of this scaffold could lead to the development of new methods of artificial fabrication of autogenic tissue substitutes.

Prokaryotic expression, refolding, and purification of functional human vascular endothelial growth factor isoform 165: Purification procedures and refolding conditions revisited

Human vascular endothelial growth factor isoform 165 (VEGF165) is the first known member belonging to the VEGF protein family that plays a critical role in new blood vessel formation in vivo. This study presents a new protocol with optimized conditions for rapidly producing untagged recombinant and biological active human VEGF165 (rhVEGF165) using Escherichia coli cells. Protein was isolated from inclusion bodies, purified by gel filtration and ion exchange chromatography, and subjected to protein refolding and renaturation. The biological activity of rhVEGF165 is comparable with VEFG from eukaryotic source according to human umbilical vein endothelial cells (HUVEC) proliferation assay. Therefore, the present procedures provide a fast and easy way to produce this therapeutic protein.

Synthesis and interfacing of biocompatible iron oxide nanoparticles through the ferroxidase activity of Helicobacter Pylori ferritin

Ferritin is an iron storage protein that is often used to coat metallic nanoparticles, such as iron oxide nanoparticles (IONPs). However, the synthesis and biocompatibility of ferritin-coated IONPs remain unclear. Therefore, this study reports the synthesis of a ferritin gene cloned and expressed from Helicobacter pylori (HPFn). The ferroxidase activity of the synthase HPFn was used for the de novo synthesis of HPFn-coated IONPs under mild conditions. Gel filtration chromatography and transmission electron microscopy analyses demonstrated that the core-shell structure of both the 5.0 nm IONP nanocore and the 12.4 nm HPFn shell were correctly assembled. The cellular uptake of mouse macrophage cells (RAW 264.7 cells) has shown that only a few HPFn-coated IONPs (3%) were taken up after 24 h of incubation. This study compares the biocompatibility of HPFn-coated IONPs, superparamagnetic iron oxide nanoparticles (SPIOs) and ferric salt (ferric ammonium citrate) in respect to cell growth inhibition, reactive oxygen species generation and pro-inflammatory cytokine TNF-α release. Assessment results showed that the responses elicited by HPFn-coated IONPs were similar to those elicited by SPIO treatment but milder than those elicited by ferric salt treatment. This accounts for the notion that ferritin-coated IONPs are biocompatible iron agents. These findings show that the ferroxidase activity of ferritin can be used to synthesize biocompatible IONPs. The favorable properties of HPFn-coated IONPs suggest that they can be used as a non-macrophage contrast agent through further surface conjugation.