On-chip chemiluminescent signal enhancement using nanostructured gold-modified carbon microarrays

An original method for the enhancement of chemiluminescent (CL) on-chip detection of protein and oligonucleotides is presented. This enhancement is based on the electrodeposition of a gold nanostructured layer onto a screen-printed (SP) carbon microarray prior to the immobilization of biomolecules through a well-established diazonium adduct electrodeposition. Morphological studies of the Au layer (optical and atomic force microscopy) show that the metal film is composed of nanostructured 800 nm diameter particles covering the entire graphite surface and yielding a high surface area. Using these modified SP microarrays, enhancement factors of 229 and 126 were obtained for prostate-specific antigen (PSA) and p53 oligonucleotide detection, respectively. These enhancements were associated with three different phenomena: an enhancement of the catalyzed chemiluminescent reaction by the gold surface, an increase of the specific surface area for immobilization of the probe biomolecules, and an opposite quenching effect due to the overlapping of the gold absorption and CL emission peaks. For free PSA and target oligonucleotide detection, enhanced performances were obtained, giving detection limits of 5 ng/mL and 0.1 nM, respectively.