Quantitative analysis of SAMs using TOF-SIMS and cell array on indium tin oxide

Abstract

Part I. Three types self-assembled monolayers (SAMs) of disulfide molecules such as $(S(CH_2)_{11}(EG)_3OCH_2O-acetylene)_2$, $(S(CH_2)_{11}(EG)_3OCH_2O-propene)_2$ and $acetylene-OCH_2O(EG)_3(CH_2)_{11}S-S(CH_2)_{11}(EG)_3OCH_2O-propene$ was measured by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). $Au-S(CH_2)_{11}(EG)_3OCH_2O-acetylene$ and $Au-S(CH_2)_{11}(EG)_3OCH_2O-propene$ negative ions were detected with a very high signal to noise rate in the mass range from 570 to 574. The spectrum of mixed SAMs made by $acetylene-OCH_2O(EG)_3(CH_2)_{11}S-S(CH_2)_{11}(EG)_3OCH_2O-propene$ shows that $Au-S(CH_2)_{11}(EG)_3OCH_2O-acetylene$ and $Au-S(CH_2)_{11}(EG)_3OCH_2O-propene$ is not equal. However, the inequality is caused not by the difference of affinity but by the difference of SIMS yield. Therefore, the ratio of $Au-S(CH_2)_{11}(EG)_3OCH_2O-acetylene$ to Au-$Au-S(CH_2)_{11}(EG)_3OCH_2O-propene$can be measured. Part II. Poly(dimethylsiloxane) (PDMS) stamps which have 10 µm width line mesh with 50 µm circle node and 50 µm circle array with 100 µm spacing were prepared to generate patterns on the transparent indium tin oxide (ITO) glass and Au-coated silicon oxide wafers. On ITO glass, OEGMA was polymerized as nonbiofouling surface and poly-L-lysine (PLL) patterns introduced by micro-contact printing (μCP). On Au surface, thiol initiator was patterned by μCP to polymerize OEGMA. Then, NIH/3T3 fibroblast cells were cultured on the PLL patterns on the ITO and pOEGMA patterns on the Au surface.