Multivariate surface analysis of plasma-deposited tetraglyme for reduction of protein adsorption and monocyte adhesion

Adsorbed proteins on implanted biomedical devices mediate platelet and leukocyte adhesion. Radio frequency plasma deposited tetraglyme (CH3O(CH2CH2O)(4)CH3), which forms a PEO-like coating, has been shown to resist protein adsorption and monocyte adhesion in vitro. By using different plasma deposition powers (5-80 W), we produced a series of plasma-deposited tetraglyme surfaces that varied in surface chemistry as measured by electron spectroscopy for chemical analysis (ESCA) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Both fibrinogen and IgG adsorption were increased on surfaces made at high plasma power. Monocyte adhesion correlated linearly with the amount of adsorbed protein. To identify the surface chemical features that contributed to the nonfouling properties of plasma-deposited tetraglyme, multivariate analysis using partial least squares (PLS) regression was applied. A PLS calibration model based on deposited tetraglyme samples placed downstream in the plasma reactor successfully predicted fibrinogen adsorption to deposited tetraglyme samples placed midstream in the reactor. The model identified how each surface spectral variable from ESCA and ToF-SIMS contributed to protein adsorption. The fraction of carbon in ether carbon linkages as measured by ESCA and ToF-SIMS peaks at m/z 59 and 103 was higher on surfaces that exhibited ultralow fibrinogen adsorption (<10 ng/cm(2)). The fraction of hydrocarbon-like carbons as measured by ESCA and low-mass ToF-SIMS peaks such as m/z 29 and 31 was greater on surfaces exhibiting high fibrinogen adsorption (>200 ng/cm(2)). This study elucidated the surface chemical features of deposited tetraglyme that most affect its resistance to protein and cell uptake and provided guidelines for engineering improved nonfouling biomaterial surfaces.