Perforation Does Not Compromise Patterned Two-Dimensional Substrates for Cell Attachment and Aligned Spreading

Controlling the Surface Chemistry of a Hydrogel for Spatially Defined Cell Adhesion

A two-step synthesis is described for activating the surface of a fully hydrated hydrogel that is of interest as a possible scaffold for neural regeneration devices. The first step exploits the water content of the hydrogel and the hydrophobicity of the reaction solvent to create a thin oxide layer on the hydrogel surface using a common titanium or zirconium alkoxide. This layer serves as a reactive interface that enables rapid transformation of the hydrophilic, cell-nonadhesive hydrogel into either a highly hydrophobic surface by reaction with an alkylphosphonic acid, or into a cell-adhesive one using a (α,ω-diphosphono)alkane. Physically imprinting a mask ("debossing") into the hydrogel, followed by a two-step surface modification with a phosphonate, allows for patterning its surface to create spatially defined, cell-adhesive regions.

Self-assembled monolayers of phosphonates promote primary chondrocyte adhesion to silicon dioxide and polyvinyl alcohol materials

The optimal solution for articular cartilage repair has not yet been identified, in part because of the challenges in achieving integration with the host. Coatings have the potential to transform the adhesive features of surfaces, but their application to cartilage repair has been limited. Self-assembled monolayer of phosphonates (SAMPs) have been demonstrated to increase the adhesion of various immortalized cell types to metal and polymer surfaces, but their effect on primary chondrocyte adhesion has not been studied. The objective of this study was to investigate the response of primary chondrocytes to SAMP coatings. We hypothesized a SAMP terminated with an α,ω-bisphosphonic acid, in particular butane-1,4-diphosphonic acid, would increase the number of adherent primary chondrocytes to polyvinyl alcohol (PVA). To test our hypothesis, we first established our ability to successfully modify silicon dioxide (SiO2) surfaces to enable chondrocytes to attach to the surface, without substantial changes in gene expression. Secondly, we applied identical chemistry to PVA, and quantified chondrocyte adhesion. SAMP modification to SiO2 increased chondrocyte adhesion by ×3 after 4 hr and ×4.5 after 24 hr. PVA modification with SAMPs increased chondrocyte adhesion by at least ×31 after 4 and 24 hours. Changes in cell morphology indicated that SAMP modification led to improved chondrocyte adhesion and spreading, without changes in gene expression. In summary, we modified SiO2 and PVA with SAMPs and observed an increase in the number of adherent primary bovine chondrocytes at 4 and 24 hr post-seeding. Mechanisms of chondrocyte interaction with SAMP-modified surfaces require further investigation.