title: Enhancement of Colorimetric Response of Enzymatic Reactions by Thermally Evaporated Plasmonic Thin Films: Application to Glial Fibrillary Acidic Protein.
abstract: We report the enhancement of the colorimetric response of horseradish peroxidase (HRP) and alkaline phosphatase (AP) in bioassays by thermally evaporated silver, gold, copper and nickel thin films. In this regard, a model bioassay based on biotin-avidin interactions was employed. Biotin groups and enzymes were introduced to all surfaces using a biotinylated linker molecule and avidin, respectively. The colorimetric response of HRP in the model bioassay carried out on the plasmonic thin films were up to 4.4-fold larger as compared to control samples (i.e., no plasmonic thin films), where the largest enhancement of colorimetric response was observed on silver thin films. The colorimetric response of AP on plasmonic thin films was found to be similar to those observed on control samples, which was attributed to the loss of enzymes from the surface during the bioassay steps. The extent of enzymes immobilized on to plasmonic thin films was found to affect the colorimetric response of the model bioassay. These findings allowed us to demonstrate the use of silver thin films for the detection of glial fibrillary acidic protein (GFAP), where the colorimetric response of the standard bioassays for GFAP was enhanced up to 67% as compared to bioassays on glass slides.
authors: Morgan State University, Department of Chemistry, 1700 East Cold Spring Lane, Baltimore, MD 21251 USA.
authors: Biebele
authors: B
authors: Abel
authors: Morgan State University, Department of Chemistry, 1700 East Cold Spring Lane, Baltimore, MD 21251 USA.
authors: Tabassum S
authors: TS
authors: Kabir
authors: Morgan State University, Department of Chemistry, 1700 East Cold Spring Lane, Baltimore, MD 21251 USA.
authors: Babatunde
authors: B
authors: Odukoya
authors: Morgan State University, Department of Chemistry, 1700 East Cold Spring Lane, Baltimore, MD 21251 USA.
authors: Muzaffer
authors: M
authors: Mohammed
authors: Morgan State University, Department of Chemistry, 1700 East Cold Spring Lane, Baltimore, MD 21251 USA.
authors: Kadir
authors: K
authors: Aslan
keywords: Plasmonic thin films; alkaline phosphatase; amplification of colorimetric response; biotin-poly(ethylene-glycol)amine; copper thin films; glial fibrillary acidic protein; gold thin films; horse radish peroxidase; nickel thin films; silver thin films