Fabrication of positively charged poly(ethylene glycol)-diacrylate hydrogel as a bone tissue engineering scaffold

Abstract

To improve cell attachment and to understand the effects of positive charge on the behavior of osteoblasts, 2-(methacryloyloxy)ethyl-trimethylammonium chloride (MAETAC), a positively charged monomer, was incorporated into poly(ethylene glycol)-diacrylate (PEGDA) hydrogel. The physicochemical properties of the resultant polymers, including the degree of acrylation of PEGDA, pKa of MAETAC, swelling ratio, zeta potential, and protein adsorption were investigated. Meanwhile, osteoblast-like MC3T3-E1 cells were seeded on the hydrogel to evaluate the effect of the positive charge on the behavior of the cells, including attachment, proliferation, and differentiation. The results revealed that PEGDA was synthesized with 90 percent of acrylation and MAETAC had been successfully incorporated into PEGDA. The pKa value of MAETAC was 9.4 determined by acid-based titration. The electrically charged nature of modified hydrogels was confirmed by zeta potential. With increasing concentration of MAETAC, the swelling ratio of the hydrogel in deionized water increased, while the swelling ratio stayed constant in phosphate buffer solution. The protein adsorption of the hydrogel also increased with increasing concentration of MAETAC. The modification of positive charge not only enhanced the attachment and proliferation of osteoblast-like MC3T3-E1 cells on the hydrogel, but also up-regulated alkaline phosphatase activity in the cells as well as gene expression of focal adhesion kinase and osteogenic markers, including collagen I, osteopontin, and osteocalcin. These findings indicate that the positively charged PEGDA may not only be a promising scaffold candidate for bone tissue engineering, but also a good platform to study the effect of positive charge on cell behavior due to the controllable charge density.

Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant

“…An explanation was made in term of ion crowding in the electric double layer [43,44,45], whereby the crowding of counterions dominates screening. When KNN were immersed into cell culture medium, since most proteins are negatively charged under physiological conditions, as a result of an isoelectric point less than 6 [50,51], negative protein were selectively adsorbed on positive KNN surface, forming a protein layer that contributes to cell adhesion [52] (Figure 6a). While on negative KNN surface, cations including Ca 2+ counter-ions, which is considered to promote osteoblast cell adhesion by attracting negatively charged proteins from cell medium [16] and by supplying Ca 2+ to binding sites in transmembrane proteins responsible for cell adhesion and proliferation [53], were closely attracted, contributing to the adhesion and proliferation of cells on this surface (Figure 6b).…”

Enhancement of adhesion and promotion of osteogenic differentiation of human adipose stem cells by poled electroactive poly(vinylidene fluoride)

“…Cell adhesion is a fundamental factor in the biomaterials field and is regulated by biological, biochemical and environmental factors. Previous findings have indicated that the surface charge of the biomaterial plays an important role in cell attachment and differentiation in chondrocytes and in bone tissue engineering . The mechanism by which the charges and piezoelectric properties affect the responses at this biological interface has been investigated; however, not a single mode of action has been identified to date.…”

The Role of Gap Junctions and Mechanical Loading on Mineral Formation in a Collagen-I Scaffold Seeded with Osteoprogenitor Cells

“…An alternative strategy for bridging large bone defects is the use of tissue engineering scaffolds, i.e., natural or synthetic scaffolds that can be seeded with osteogenic cells. For example, hard scaffold materials such as polycaprolactone (PCL) or hydroxyapatite can contribute to measurable bone repair (7,8), as can "soft" scaffolds composed of natural or synthetic products (7,8). Among the many choices of soft natural biomaterials for bone tissue engineering, type I collagen is popular as it is abundant and is the primary organic component of bone matrix (9).…”