We have evaluated five bioconjugation chemistries for immobilizing DNA onto silicon substrates for microfluidic biosensing applications. Conjugation by organosilanes is compared with linkage by carbonyldiimidazole (CDI) activation of silanol groups and utilization of dendrimers. Chemistries were compared in terms of immobilization and hybridization density, stability under microfluidic flow-induced shear stress, and stability after extended storage in aqueous solutions. Conjugation by dendrimer tether provided the greatest hybridization efficiency; however, conjugation by aminosilane treated with glutaraldehyde yielded the greatest immobilization and hybridization densities, as well as enhanced stability to both shear stress and extended storage in an aqueous environment. Direct linkage by CDI activation provided sufficient immobilization and hybridization density and represents a novel DNA bioconjugation strategy. Although these chemistries were evaluated for use in microfluidic biosensors, the results provide meaningful insight to a number of nanobiotechnology applications for which microfluidic devices require surface biofunctionalization, for example vascular prostheses and implanted devices.
Fig. S1Schematic of DNA immobilization and microfluidic hybridization assays. Immobilization of DNA in spots defined by a PDMS mask is depicted in the image in the back. After immobilization of DNA, a microfluidic channel (1 mm × 2 cm × 45 μm) is aligned over the immobilized DNA, and target DNA is made to flow through the channel at 2 μl/min, as depicted in the image in the front. (PDF 1017 kb)