Surface charges dominated protein adsorption on hydrogels
Candidate materials towards soft tissue engineering require anti-fouling materials that are biocompatible, protein anti-fouling, and mechanically flexible. Conventional hydrogels having more than 70 wt% water are available to design with these criteria in mind. However, some of hydrogels are difficulty to apply hydrogels in internal body organs, because some undesirable proteins absorption on their surfaces. Previously, due to the lack of an effective method in observing the true charge densities of hydrogels, the reason why electrostatic interactions dominate protein absorption behavior is still unclear. In this work, we adopt the microelectrode technique (MET) to study the electrical potential of hydrogels that having negative, positive and neutral potentials, and demonstrate the protein absorption behavior on those hydrogels. The results show that the MET is an effective method to obtain the surface charge densities of various hydrogels. Furthermore, the amount of proteins absorbed to the gel is quantified by the charge density of hydrogels. These results indicate that the electrostatic absorption was quantitatively dominated by a combination of the charge density of hydrogels and the overall charges of proteins. With the knowledge obtained in this work, the effect of surface charges in a hydrogel on protein absorption could be well understood, and this result could be prospective to promote the application of hydrogel in tissue engineering.