Synthesis of thiolated glycosaminoglycans and grafting to solid surfaces

Glycosaminoglycans (GAGs) with varying degree of sulfation were chemically modified to obtain thiolated analogues (tGAGs) for subsequent surface grafting on vinyl-terminated self-assembled monolayers. Thiolation was achieved by the use of the disulfide containing crosslinker 3,3'-dithiobis(propanoic hydrazide) and subsequent reduction of the disulfide with dithiothreitol. Two different molar ratios of the crosslinker were used for conjugation. The tGAGs were characterized by 1H-NMR, Raman and flow-field-flow-fractionation (A4F) to determine the chemical composition, structure and molecular weight of the products. Ellman's reagent was used to quantify the thiol concentration of tGAGs. The tGAGs were immobilized onto vinyl-terminated glass and silicon via thiol-ene reaction. This was achieved by homogeneous immobilization from solution as well as with microcontact printing and exposure to UV light. The results of water contact angle measurement (WCA), ellipsometry and confocal laser scanning microscopy (CLSM) demonstrated that the resulting surface coverage was dependent on the degree of thiolation of GAGs.