Biology Reference
In-Depth Information
aschemicalcross-linking,electronbeam,orUVlightirradiation,and
electro-deposition [4]. Electrostatic adsorption is straight forward
and the particle size can be strictly controlled from the previous
chemical synthesis of the nanoparticle. These surfaces, however,
are unstable and prone to particle desorption. Covalently cross-
linking nanoparticles to a surface can be quite versatile due to
the large range of functional groups available for cross-linking, but
first requires the modification of the surface which can hinder
electrochemical signals to the electrode. Nanoparticle synthesis
from electron beam and UV light irradiation does not suffer from
the insulating effects of covalent cross-linking; however, these
methods can be expensive and time consuming. Electrochemical
deposition of nanoparticles on the other hand, is a simple and
facile method to create nanoparticle-modified surfaces while the
final nanoparticle size and surface density can be controlled by
varying the deposition time, potential, and metal ion concentration
in solution. The following sections will focus on nanoparticle-DNA
immobilization methods in which electrochemistry was used to
modify surfaces with nanoparticles, or in which electrochemical
detectionwascombinedwithaDNA-nanoparticle-modifiedsurface.
14.2.2
Gold Nanoparticle Supports
The chemisorption of thiol moieties onto gold makes the use of
gold nanoparticles a convenient support to immobilize sulfhydryl-
modified oligonucleotides for the construction of electrochemical
biosensors [5]. For instance, DNA hybridization was combined
withenzymaticelectrochemicaldetectionontogoldnanostructured
screen-printed carbon electrodes from the
in situ
generation of gold
nanoparticles using an applied constant current after which a 30-
mer oligonucleotide included in the SARS (severe acute respiratory
syndrome)-associated coronavirus genome was immobilized [6].
An alkaline phosphatase-modified detection probe was used to
monitor DNA hybridization events using a 3-indoxyl phosphate
substrate that produces a compound which was able to reduce
silver ions in solution into a metallic deposit. The deposited silver
was then electrochemically stripped into solution and measured by
anodic stripping voltammetry. Electrochemical deposition can also
