Electrical field induce mBMSCs differentiation to osteoblast via protein adsorption enhancement.

Electrical stimulation as a useful and simple method attracts a lot of attention due to its potential to influence cell behaviors. Reports on the change of cell interior structures and membrane under electrical field would be the possible mechanisms. However, changes in cell behavior caused by protein adsorption under different electric field has not been noticed and discussed yet. In this study, a composite hydrogel PDA-GO-PAAM with conductivity of 8.23 × 10-4 S/cm and has similar elastic modulus with pure PAAM was fabricated. It was found that BSA adsorption was higher on composite hydrogel，while electrical stimulation would further enhance BSA adsorption. Cell experiments revealed that electrical stimulation of mBMSCs insignificantly affect cell proliferation, and strongly promoted the expression of cell adhesion factors compared to the unstimulated control. Meanwhile, mBMSCs showed a spreading morphology on composite hydrogel and such spreading became even wider under the electrical stimulation. Under the effect of electrical stimulation, the larger the cell adhesion area was found on the hydrogel, the more the osteoblasts genotype and phenotype expression were, especially under the parameter of 1 V/cm and 1 h. Our results hence illustrate that electrical stimulation regulates osteogenic differentiation of mBMSCs via tuning cell adhesion and cell spreading mediated by protein adsorption.

Role of Stiffness versus Wettability in Regulating Cell Behaviors on Polymeric Surfaces.

Substrate wettability and stiffness, two factors impacting cell behaviors simultaneously, have been attracting much attention to elaborate which one dominates. In this study, hydrophilic poly(2-hydroxyethyl methacrylate) brushes were grafted onto the surfaces of poly(dimethylsiloxane) (PDMS) with elastic moduli of 3.66, 101.65 and 214.97 MPa and decreasing water contact angle from 120.4° to 38.5°. Cell behaviors of three cell lines including mBMSCs, ATDC-5, and C28/I2 were then investigated on the hydrophilic and hydrophobic PDMS with different stiffness, respectively. The proliferation of three cell lines was faster on the hydrophilic PDMS than the hydrophobic PDMS, but the stiffness of the hydrophilic or hydrophobic PDMS did not have a significant impact on cell proliferation. The increase of the stiffness enhanced cell migration, the cell spread and the gene expression proportion of extracellular matrix/intercellular adhesion molecules (integrin + FAK/NCAM + N-cadherin) for all three cell lines, but the increase of the wettability showed small enhancement in cell migration, cell spread and gene expression. Moreover, the cartilage-specific gene expression of SOX9 and COL2 downregulated for all three cell lines with the increasing stiffness. The interpretation of the effect of substrate wettability and stiffness on cell behaviors would function as very useful guideline to direct scaffold fabrication.

A Dexamethasone-Eluting Porous Scaffold for Bone Regeneration Fabricated by Selective Laser Sintering.

Additive manufacture (AM) has been widely and rapidly applied in fabrication of 3D porous scaffolds for tissue engineering applications. For synthetic polymers of high melting temperature, the melting-extruding technique is the most applied AM method for such fabrication of polymer porous scaffolds. This results in a big challenge to directly process the scaffolds using the polymers and thermosensitive substances simultaneously because of deactivation under high temperature. In this article, the selective laser sintering (SLS) method was proposed to make a poly(l-lactic acid) (PLLA) porous scaffold containing dexamethasone (Dex) simultaneously. Dex was encapsulated in two groups of PLLA-bioactive glass (BG) composite microspheres with an average diameter of 115-120 µm and loading amounts of 0.68 ± 0.09 and 0.84 ± 0.10 µg/mg, respectively. The drug-loading composite microspheres were then fabricated into scaffolds under a laser fluence of 0.83-2.08 J/mm2. The average pore size and compressive modulus for the porous scaffold were 450-500 µm and 18-25 MPa, respectively. Drug release experiments showed that Dex was released from the scaffold in a controlled manner until about a month. The eluting time of HPLC tests before or after SLS processing both presented at 4 min indicated no chemical structure changes for the drug. Ex vivo cell experiments also testified the comparable effect of released Dex with commercial products, showing that the bioactivities were not affected after SLS. Implantation of the composite scaffolds in rat cranium defects demonstrated that new bone and blood vessel formation was faster in the Dex-releasing scaffolds than in the groups without drug loading.