Ultrastructural Study on the Specific Binding of Genetically Engineered Epidermal Growth Factor to Type I Collagen Fibrils

Collagen-binding bone morphogenetic protein-2 designed for use in bone tissue engineering

Bone tissue engineering using biodegradable porous scaffolds is a promising approach for restoring oral and maxillofacial bone defects. Recently, attempts have been made to incorporate proteins such as growth factors to create bioactive scaffolds that can engage cells to promote tissue formation. Collagen-based scaffolds containing bone morphogenetic protein-2 (BMP2) have been studied for bone formation. However, controlling the initial burst of BMP2 remains difficult. Here we designed a functional chimeric protein composed of BMP2 and a collagen-binding domain (CBD), specifically the A3 domain of von Willebrand factor, to sustain BMP2 release from collagen-based scaffolds. Based on the results of computer-based structural prediction, we prepared a chimeric protein consisting of CBD and BMP2 in this order with a peptide tag for affinity purification. The chimeric protein had a collagen-binding capacity and enhanced osteogenic differentiation of human mesenchymal stem cells. These results are consistent with insights from in silico structural prediction.

Immobilization of Growth Factors for Cell Therapy Manufacturing

Cell therapy products exhibit great therapeutic potential but come with a deterring price tag partly caused by their costly manufacturing processes. The development of strategies that lead to cost-effective cell production is key to expand the reach of cell therapies. Growth factors are critical culture media components required for the maintenance and differentiation of cells in culture and are widely employed in cell therapy manufacturing. However, they are expensive, and their common use in soluble form is often associated with decreased stability and bioactivity. Immobilization has emerged as a possible strategy to optimize growth factor use in cell culture. To date, several immobilization techniques have been reported for attaching growth factors onto a variety of biomaterials, but these have been focused on tissue engineering. This review briefly summarizes the current landscape of cell therapy manufacturing, before describing the types of chemistry that can be used to immobilize growth factors for cell culture. Emphasis is placed to identify strategies that could reduce growth factor usage and enhance bioactivity. Finally, we describe a case study for stem cell factor.

Design and Use of Chimeric Proteins Containing a Collagen-Binding Domain for Wound Healing and Bone Regeneration

Collagen-based biomaterials are widely used in the field of tissue engineering; they can be loaded with biomolecules such as growth factors (GFs) to modulate the biological response of the host and thus improve its potential for regeneration. Recombinant chimeric GFs fused to a collagen-binding domain (CBD) have been reported to improve their bioavailability and the host response, especially when combined with an appropriate collagen-based biomaterial. This review first provides an extensive description of the various CBDs that have been fused to proteins, with a focus on the need for accurate characterization of their interaction with collagen. The second part of the review highlights the benefits of various CBD/GF fusion proteins that have been designed for wound healing and bone regeneration.

Stability, cytotoxicity and cell uptake of water-soluble dendron-conjugated gold nanoparticles with 3, 12 and 17 nm cores

This article describes the synthesis of water-soluble dendron-conjugated gold nanoparticles (Den-AuNPs) with various average core sizes and the evaluation of stability, cytotoxicity, cell permeability and uptake of these materials. The characterization of Den-AuNPs using various techniques including transmission electron microscopy (TEM), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), 1H NMR, FT-IR, and UV-vis spectroscopy confirms the dendron conjugation to the glutathione-capped gold nanoparticles (AuNPs). The stability of AuNPs and Den-AuNPs in solutions of different pH and salt concentration is determined by monitoring the changes in surface plasmon bands of gold using UV-vis spectroscopy. The stability of Den-AuNPs at different pH remained about the same compared to that of AuNPs. In comparison, the Den-AuNPs are found to be more stable than the precursor AuNPs maintaining their solubility in the aqueous solution with the salt concentration of up to 100 mM. The improved stability of Den-AuNPs suggests that the post-functionalization of thiol-capped gold nanoparticle surfaces with dendrons can further improve the physiological stability and biocompatibility of gold nanoparticle-based materials. Cytotoxicity studies of AuNPs and Den-AuNPs with and without fluorophores are also performed by examining cell viability for 3T3 fibroblasts using a MTT cell proliferation assay. The conjugation of dendrons to the AuNPs with a fluorophore is able to decrease the cytotoxicity brought about by the fluorophore. The successful uptake of Den-AuNPs in mouse fibroblast 3T3 cells shows the physiological viability of the hybrid materials.

Engineering the regenerative microenvironment with biomaterials

Modern synthetic biomaterials are being designed to integrate bioactive ligands within hydrogel scaffolds for cells to respond and assimilate within the matrix. These advanced biomaterials are only beginning to be used to simulate the complex spatio-temporal control of the natural healing microenvironment. With increasing understanding of the role of growth factors and cytokines and their interactions with components of the extracellular matrix, novel biomaterials are being developed that more closely mimic the natural healing environments of tissues, resulting in increased efficacy in applications of tissue repair and regeneration. Herein, the important aspects of the healing microenvironment, and how these features can be incorporated within innovative hydrogel scaffolds, are presented.

Construction of multifunctional proteins for tissue engineering: epidermal growth factor with collagen binding and cell adhesive activities

The development of different techniques based on natural and polymeric scaffolds are useful for the design of different biomimetic materials. These approaches, however, require supplementary steps for the chemical or physical modification of the biomaterial. To avoid such steps, in the present study, we constructed a new multifunctional protein that can be easily immobilized onto hydrophobic surfaces, and at the same time helps enhance specific cell adhesion and proliferation onto collagen substrates. A collagen binding domain was fused to a previously constructed protein, which had an epidermal growth factor fused to a hydrophobic peptide that allows for cell adhesion. The new fusion protein, designated fnCBD-ERE-EGF is produced in Escherichia coli, and its abilities to bind to collagen and promote cell proliferation were investigated. fnCBD-ERE-EGF was shown to keep both collagen binding and cell growth-promoting activities comparable to those of the corresponding unfused proteins. The results obtained in this study also suggest the use of a fnCBD-ERE-EGF as an alternative for the design of multifunctional ECM-bound growth factor based materials.