LBL self-assembly of chondroitin sulfate and collagen onto poly(L-lactic acid) surface for improving its cytocompatibility with endothelial cells

Amino groups were covalently introduced onto poly (L-lactic acid) (PLLA) surface by the aminolyzing reaction between 1,6-hexanediamine and the ester groups of PLLA. The amino groups provides the possibility to modify PLLA surface using technology of layer-by-layer (LBL) self-assembly, because these aminolyzed polyesters can be used as the polycationic substrate. Biocompatible chondroitin sulfate A (CS) and collagen type I were chosen to be deposited alternately onto the aminolyzed PLLA membrane surface. The deposition process was monitored by UV-Vis absorbance spectroscopy and energy transfer by fluorescence spectroscopy after the polyelectrolytes were labeled by fluorescein isothiocyanate (FIT() and rhodamine isothiocyanate, respectively. The layer thickness increased linearly at first with the increase of the deposited layers, and then increased slowly due to the layer interpenetration. The existed collagen improved the cytocompatibility of PLLA to human endothelial cells. The cell attachment, activity and proliferation increased greatly on the PLLA membranes assembled with only one bilayers of CS/collagen (with collagen as the outermost layer). Cells also showed morphology of flat endothelium, and a confluent cell layer was reached after being cultured for 4 d. Due to the advantages of those traditional methods, LBL self-assembly technique will attract many attentions in scaffold modification in tissue engineering.