Development of amphiphilic, enzymatically-degradable PEG-peptide conjugate as cell crosslinker for spheroid formation.

In this study, we developed a novel kind of PEG-peptide conjugated cell crosslinker which is composed of amphiphilic oleyl-polyethylene glycol (PEG) derivatives conjugated with an enzymatically degradable peptide. The oleyl groups at both ends of the polymer chain act as anchoring moiety which can incorporate into cell membrane bilayer via hydrophobic interaction while the incorporation of the peptide sequence in the polymer chain renders the cell crosslinker enzymatically degradable. The average molecular weight, critical micelle concentration of the crosslinker was systematically characterized by gel permeation chromatography, fluorescence method and the crosslinker was shown to be readily cleaved by collagenase. HepG2 cells spheroids formation was observed when the cell crosslinker was added. The number of cells kept increasing over the culture period in the presence of cell crosslinker, suggesting its improved cytocompatibility. With the addition of cell crosslinker, the liver-specific functions of HepG2, such as ammonia elimination, albumin secretion, was enhanced by 1.9 times and 3.0 times on 7th day culture, respectively. Fluorescence microscopy showed more distinct and intense albumin staining in spheroids with cell crosslinker than that without crosslinker. This novel kind of cell crosslinker will be a promising material for tissue engineering and regenerative medicine.