Improved Growth Control of Encapsulated Cells by Modification of Scaffold Geometry

Abstract

Abstract: : Purpose: To investigate the effects of geometry and surface area of poly(ethylene) and poly(butlylene) terepthalate (PET, PBT) scaffolding on encapsulated cell adhesion and growth. Methods: Cylindrical monofilaments of PET and PBT with diameters ranging between 100 and 200 microns were boiled in 1 N NaOH for 1 hour. The treated monofilaments were placed inside hollow fiber membrane devices and CNTF secreting cells were encapsulated within the device at varying densities. The devices were incubated in nutrient media and were analyzed at 3–days, 1–week and 1–month. CNTF release from the devices was quantified using a commercial ELISA kit. Cell proliferation was determined using a metabolic assay and histomorphologic cell counts. Cell morphology was assessed by H&E staining and scanning electron microscopy, and cellular apoptosis was investigated using TUNEL staining. Results:: In comparison to the control devices containing > 100 monofilaments of 20 micron diameter scaffolding (NT–501 devices), the effective planar surface area available for cell attachment within the large diameter scaffold devices clearly controlled cell growth and density. Unlike the 3–dimensional tissue mass that is formed within multiple strands of monofilaments in the NT–501 device, the planar geometry of the large diameter single tubing promoted monolayer attachment and controlled growth of encapsulated cells. CNTF output from the monofilament scaffold devices was decreased in comparison to the NT–501 devices and a clear relationship between surface area and CNTF dose has been established. Cell viability in all groups remained robust at 1–month. The modified scaffold structure also facilitated enzymatic dissociation of the encapsulated cells. Conclusions: The results indicate that increasing the effective surface area for monolayer attachment of the cells can improve control over encapsulated cell growth. These findings may allow for a more consistent method of cell growth regulation in an encapsulation device and create a potential option for dose control of cell–based drug delivery.

Keywords: none