Characterization and quantification of biological micropatterns using cluster SIMS

Micropatterning is used widely in biosensor development, tissue engineering and basic biology. Creation of biological micropatterns typically involves multiple sequential steps which may lead to cross-contamination and contribute to suboptimal performance of the surface. Therefore, there is a need to develop novel strategies for characterizing location-specific chemical composition of biological micropatterns. In this paper, C₆₀⁺ time-of-flight secondary ion mass spectrometry (ToF-SIMS) operating in the event-by-event bombardment/detection mode was used for spatially resolved chemical analysis of micropatterned indium tin oxide (ITO) surfaces. Fabrication of the micropatterns involved multiple steps including self-assembly of poly(ethylene glycol)-silane (PEG-silane), patterning of photoresist, treatment with oxygen plasma and adsorption of collagen (I). The ITO surfaces were analyzed with 26-keV C₆₀⁺ SIMS run in the event-by-event bombardment/detection mode at different steps of the modification process. We were able to evaluate the extent of cross-contamination between different steps and quantify coverage of the immobilized species. The methodology described here provides a novel means for characterizing the composition of biological micropatterns in a quantitative and spatially resolved manner.