This paper describes a simple strategy for DNA immobilization on chemically modified and patterned silicon surfaces. The photochemical modification of hydrogen-terminated Si(111) with undecylenic acid leads to the formation of an organic monolayer covalently attached to the surface through Si-C bonds without detectable reaction of the carboxylic acid group, providing indirect support of a free radical mechanism. Chemical activation of the acid function was achieved by a simple chemical route using N-hydroxysuccinimide (NHS) in the presence of N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride. Single strand DNA with a 5'-dodecylamine group was then coupled to the NHS-activated surface by amide bond formation. Using a previously reported chemical patterning approach, we have shown that DNA can be immobilized on silicon surfaces in spatially well-resolved domains. Methoxytetraethyleneglycolamine was used to inhibit nonspecific adsorption. The resulting DNA-modified surfaces have shown good specificity and chemical and thermal stability under hybridization conditions. The sequential reactions on the surface were monitored by ATR-FTIR, X-ray Photoelectron Spectroscopy, and fluorescence spectroscopy.

Silicone polymers (polydimethylsiloxanes, (Me 2 SiO) n , PDMSs) have been exploited in a variety of personal care [1] and medically related [2] applications. For instance, liquid silicones are used as oral defoamers in anti-acid formulations, [3] and as carriers for cosmetics and deodorants; [4] silicone elastomers are used in medical-grade tubing, transdermal drug delivery patches, and implanted prostheses (an application that has caused much controversy); [5] and silicone±polyether copolymers are used in hair-care applications.[4] The properties that make silicones particularly appropriate for these applications include hydrophobicity, low glass transition temperature T g (typically less than ±120 C [6]

Protein-on-silicone and silicone-on-protein films were made by the sequential coating of the human serum albumin (HSA) onto silicone films on glass or vice versa. The silicones used were either trimethylsilyl-terminated poly(dimethylsiloxane) (unfunctionalized PDMS) or (triethoxysilyl)propyl-terminated poly(dimethylsiloxane) (functionalized TES−PDMS). Angular-dependent X-ray photoelectron spectroscopy (AD-XPS) and contact angle measurements (CA) were used to characterize the modified surfaces. Irrespective of the order of building the films, protein-on-silicone or silicone-on-protein both showed essentially identical surface compositions, suggesting a significant degree of mixing between the protein and silicone. The TES−PDMS was found to have a greater affinity for HSA:  thicker and more homogeneous silicone films were found with TES−PDMS/HSA than with PDMS/HSA films.

In previous studies nonionic organofunctional silicones were shown to enhance the intimacy of protein−silicone interactions at solid−liquid interfaces. In the current studies the same phenomenon was shown to manifest itself, even more clearly, at liquid−liquid interfaces. Proteins or silicones by themselves were unable to impart stability to otherwise surfactant-free water-in-silicone oil emulsions. However, stable water-in-silicone oil emulsions resulted from the simultaneous adsorption of a protein and a (triethoxysilyl)propyl-functionalized silicone at the interface from the corresponding bulk phases. Similarly, combinations of proteins and functional silicones lowered the interfacial tension of water-in-silicone oil emulsions more efficiently than either of the surfactants on their own. This clearly implies effective protein−silicone synergism at the interface, possible reasons for which are discussed.