High-density protein patterning through selective plasma-induced fluorocarbon deposition on Si substrates

A novel method for fabrication of protein microarrays through selective plasma-induced modification of patterned substrates is presented. Exposing Si substrates bearing SiO2 or Si3N4 patterns to a c-C4F8 plasma in a high-density plasma reactor, a fluorocarbon (FC) film was selectively deposited on Si areas, whereas the SiO2 or Si3N4 patterns were simultaneously etched. Optimizing the plasma parameters such as power, bias voltage and gas pressure, patterned substrates with highly selective protein adsorption capacities were obtained. More specifically, using fluorescently labeled protein solutions direct selective protein binding onto SiO2 or Si3N4 areas versus the Si substrate was verified. In addition, model binding assays were demonstrated through proteins immobilization on the patterned substrate and their subsequent reaction with fluorescently labeled counterpart molecules. Patterned Si/SiO2 or Si/Si3N4 surfaces not subjected to plasma treatment presented negligible protein adsorption. Following the proposed method, highly resolved protein spots with diameters down to 1 μm were created. The spots presented high intra-spot fluorescence homogeneity (coefficient variation (CV) ≤ 10%), inter-spot fluorescence repeatability (CV ≤ 5%) and excellent morphology. Thus, substrates prepared following the proposed method can be applied to the fabrication of high-density and high-quality protein microarrays.