Fibronectin and culture temperature modulate the efficacy of an avidin-biotin binding system for chondrocyte adhesion and growth on biodegradable polymers.

Cell adhesion to a scaffold is a prerequisite for tissue engineering. Many studies have been focused on enhancing cell adhesion to synthetic materials that are used for scaffold fabrication. Previously, we showed that immobilization of biotin molecules to chondrocyte surfaces enhanced cell adhesion to avidin-coated biodegradable polymers such as poly-L-lactic acid, poly-D,L-lactic acid and polycaprolactone. However, the endocytosis of cell membrane biotin molecules decreases binding strength between biotinylated-chondrocytes (B-chondrocytes) and avidin-coated substrata, and therefore decreases cell spreading and discourages long-term chondrocytes culture. In this study, we proposed two strategies to solve the shortcoming of the avidin-biotin binding system. First, the avidin-biotin binding system is combined with the intrinsic integrin-dependent adhesion systems in order to enhance long-term cell culture. Second, the incubation temperature is lowered in order to slow down the endocytosis process. We found that the avidin-biotin binding system in combination with FN-integrin binding system enhanced cell adhesion, cell spreading and cell growth. Decrease of cell culture temperature to 4 degrees C enhanced the adhesion of B-chondrocytes to the avidin-coated surfaces, but decreased cell viability and proliferation, compared to culture temperature of 37 degrees C. Whether there is an optimal seeding temperature between 4 and 37 degrees C for both adhesion and proliferation of B-chondrocytes needs further investigation. Our results indicated that modulation of the adhesion conditions could further enhance the efficacy of the avidin-biotin binding system in mediating cell adhesion, and subsequent tissue culture.