Immobilization of chondroitin sulfate for the fabrication of biomimetic brush structures

Intervertebral disc (IVD) degeneration is accompanied by a loss of proteoglycans (PGs) in the nucleus pulposus (NP), resulting in a loss of charged chondroitin sulfate (CS) chains, decreasing mechanical function of the disc. PG mimics may be employed to restore NP functionality. Synthesis of CS bottle brush structures requires immobilization of CS at its terminal end. In this study, we have investigated commercially available CS for use in CS bottle brush synthesis. A primary amine (PA) at the terminal end of CS was identified and utilized to conjugate amine-reactive monomers to CS. Conjugation of monomers to CS was confirmed using the fluorescamine assay. Percent PA conjugations of 26%, 80% and 99% were seen for acrolein, acrylic acid and allyl glycidyl ether respectively. CS was also immobilized onto epoxy and aldehyde functionalized surfaces via the CS terminal primary amine. CS attachment was determined by monitoring changes in substrate sulfur content (energy-dispersive X-ray EDAX microanalysis) and surface wettability (contact angle). The modification and immobilization of CS demonstrated here will facilitate the synthesis of CS bottle brush PG mimics.