Characterization of Poly(L-Lysine)-graft-Poly (Ethylene Glycol) Assembled Monolayers on Niobium Pentoxide Substrates Using Time-of-Flight Secondary Ion Mass Spectrometry and Multivariate Analysis

Published

March 1, 2004

Author(s)

M S. Wagner, S Pasche, David G. Castner, M Textor

Abstract

Control of protein adsorption onto solid surfaces is a critical area of biomaterials and biosensors research. Application of high performance surface analysis techniques to these problems can improve the rational design and understanding of coatings that control protein adsorption. We have used static Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) to investigate several poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) adlayers adsorbed electrostatically onto negatively charged niobium pentoxide (Nb₂O₅) substrates. By varying the PEG graft ratio (i.e. the number of lysine monomers per grafted PEG chain) and the molecular weights of the PLL and PEG polymers, the amount of protein adsorption can be tailored between 1 and 300 ng/cm². Detailed multivariate analysis using Principal Component Analysis (PCA) of the positive and negative ion ToF-SIMS spectra showed changes in the outermost surface of the polymer films that related to the density and molecular weight of the PEG chains on the surface. However, no significant differences were noted due to PLL molecular weight, despite observed differences in the serum adsorption characteristics for adlayers of PLL-g-PEG polymers with different PLL molecular weights. From the PCA results, multivariate peak intensity ratios were developed that correlated with the thickness of the adlayer and the enrichment of the PEG chains and the methoxy terminus of the PEG chains at the outermost surface of the adlayer. Furthermore, Partial Least Squares Regression (PLSR) was used to correlate the ToF-SIMS spectra with the amount of protein adsorption, resulting in a predictive model for determining protein resistance based on the ToF-SIMS spectra. The accuracy of the prediction of the amount of serum adsorption depended on the molecular weight of the PLL and PEG polymers and the PEG graft ratio. The combination of multivariate analysis and static ToF-SIMS provides detailed information on the surface chemistry and insight into the mechanism for protein resistance of the coatings.

Citation

Analytical Chemistry

Volume

76

Issue

No. 5

Pub Type

Journals

Keywords

multivariate analysis, PCA, PEG, PLS, polyelectrolytes, T0F-SIMS

Citation

Wagner, M. , Pasche, S. , Castner, D. and Textor, M. (2004), Characterization of Poly(L-Lysine)-graft-Poly (Ethylene Glycol) Assembled Monolayers on Niobium Pentoxide Substrates Using Time-of-Flight Secondary Ion Mass Spectrometry and Multivariate Analysis, Analytical Chemistry (Accessed October 3, 2024)