Effect of Scaffold Surface Chemistry on Stem Cell Response in 2-D vs. 3-D Cell Culture Niches

Sumona Sarkar, Carl G. Simon, Jr., Roberta I. Lock, and Joy P. Dunkers

 

To develop tissue engineered devices for regenerative medicine strategies, key scaffold properties for directing stem cell response must be identified.  As focus shifts from 2-D to 3-D culture systems in an attempt to better recapitulate the natural cellular environment, traditional strategies to enhance the cell culture environment may no longer have equivalent effects on cells.  The synergistic effects of the new 3-D culture environments are largely undetermined.

In the current study, to directly and independently investigate the effects of scaffold chemistry in 2-D vs. 3-D cell niches, we have systematically altered the surface chemistry of poly (ε-caprolactone) (PCL) nanofiber scaffolds (3-D niche) and spun coat PCL films (2-D niche).  In this system, scaffold structural properties are kept constant while chemistry is varied by mild hydrolysis to generate hydroxyl and carboxyl groups on the polymer surface Scaffold structure and fiber diameter were visualized using scanning electron microscopy (SEM).   

Hydrolyzed NF scaffolds and SC films both had a significant decrease in water contact angle with a corresponding increase in surface carboxyl concentration for NFs as determined by the toludine blue O assay.  In addition, XPS results indicated an increase in surface oxygen:carbon ratio on NF scaffolds.  Scaffolds were seeded with hBMSCs and investigated for morphology (1 d), proliferation (14 d) and differentiation (14 d).  Cell area was significantly lower on hydrolyzed SC vs. un-modified SC while there was no significant difference in cell shape on hydrolyzed NF vs. un-modified NF.  Proliferation was not significantly different between hydrolyzed and un-modified scaffolds while alkaline phosphatase activity was significantly increased on hydrolyzed SC films.  No significant difference was observed in alkaline phosphatase activity when comparing hydrolyzed NF versus un-modified NF. 

We have successfully developed a material system that enables the systematic investigation of the effects of scaffold structure and chemistry in 2-D vs. 3-D cultures.  The results show that PCL surface hydrolysis chemistry affects cell shape and differentiation in 2-D culture but not in 3-D culture, indicating that the surface chemistry has less effect on cell function in 3-D scaffold systems.

Acknowledgements: Christopher M. Stafford, NIST, for assistance with XPS.