Time-of-flight secondary ion mass spectrometry three-dimensional imaging of surface modifications in...

Scaffolds composed of synthetic polymers such as poly(caprolactone) (PCL) are widely used for the support and repair of tissues in biomedicine. Pores are common features in scaffolds as they facilitate cell penetration. Various surface modifications can be performed to promote key biological responses to these scaffolds. However, verifying the chemistry of these materials post surface modification is problematic due to the combination of three-dimensional (3D) topography and surface sensitivity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is commonly used to correlate surface chemistry with cell response. In this study, 3D imaging mass spectrometry analysis of surface modified synthetic polymer scaffolds is demonstrated using PCL porous scaffold, a pore filling polymer sample preparation, and 3D imaging ToF-SIMS. We apply a simple sample preparation procedure, filling the scaffold pores with a poly(vinyl alcohol)/glycerol mixture to remove topographic influence on image quality. This filling method allows the scaffold (PCL) and filler secondary ions to be reconstructed into a 3D chemical image of the pore. Furthermore, we show that surface modifications in the pores of synthetic polymer scaffolds can be mapped in 3D. Imaging of "dry" and "wet" surface modifications is demonstrated as well as a comparison of surface modifications with relatively strong ToF-SIMS peaks (fluorocarbon films [FC]) and to more biologically relevant surface modification of a protein (bovine serum albumin [BSA]). We demonstrate that surface modifications can be imaged in 3D showing that characteristic secondary ions associated with FC and BSA are associated with C₃ F₈ plasma treatment and BSA, respectively within the pore.