Extending the Three-Dimensional Culture of Adipocytes Through Surface Coatings

To mimic the important features of progressing adiposity, in vitro adipose cell culture models must allow gradual intracellular fat accumulation in the three-dimensional (3D) arrangement of adipose-derived stem cells (ASCs) over a long-term culture period. Previously, elastin-like polypeptide (ELP) and polyethyleneimine (PEI) have been used to culture human adipose-derived stem cells (hASCs) as 3D spheroids and to differentiate them to adipocytes over a relatively long culture period of up to 5 weeks. In this study, to further enhance the spheroid adhesion properties, ELP was fused with Arginine-Glycine-Aspartic Acid (RGD) residues, known for their role as cell-attachment sites. This study aimed to assess whether the addition of RGD to the C-or N-terminus of ELP would impact the spheroid-forming ability of ELP-PEI coatings. ELP-RGD conjugates were produced using genetically modified <i>Escherichia coli</i> to express ELP-(RGD)₃ and (RGD)₃-ELP, followed by chemical conjugation with PEI. SDS gel electrophoresis, FTIR spectroscopy, and turbidimetry analyses revealed that ELP was conjugated with RGD without much alteration in the molecular weight, functional groups present, and transition temperature of ELP. The addition of RGD to ELP also did not affect the chemical conjugation capacity of ELP to PEI. We observed that the ELP-PEI coating formed slightly larger spheroids (61.8 ± 3.2 µm) compared to the ELP-(RGD)₃-PEI and (RGD)₃-ELP-PEI coatings (56.6 ± 3.0 and 53.4 ± 2.4 µm, respectively). Despite the size difference, ELP-(RGD)₃-PEI coatings exhibited superior spheroid retention during media changes, with minimal spheroid loss. DNA assay results confirmed a significant decrease in the DNA concentration (<i>p</i> < 0.05) after the 20 media changes for spheroids cultured on the ELP-PEI coating, indicating spheroid loss. However, there was no significant difference in DNA concentration before and after 20 media changes for spheroids cultured on the ELP-(RGD)₃-PEI and (RGD)₃-ELP-PEI coatings (<i>p</i> > 0.05). These findings suggest that RGD incorporation does not hinder the initial spheroid formation ability of the ELP-PEI coating and enhances spheroid retention under dynamic culture conditions.