Nanotech enhancement: Gold rush

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  • Published: Aug 1, 2013
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Nanotech enhancement: Gold rush

Nicely tuned

Our final goal is to benefit of such approach to built up, in controlled fashion, composite nanostructures made up of different type of nanoparticles for diagnostic and biomedical  applications Credit: Causa et al

It is possible to tune gold nanoparticles with peptides for surface-enhanced Raman spectroscopy (SERS) in such a way as to side step the problematic stages inherent to other approaches to nanoplasmonic structures for analyte detection, according to Italian researchers.

Anastasios Manikas, Raffaella Della Moglie and Paolo Antonio Netti of the Istituto Italiano di Tecnologia (IIT), Filippo Causa of the University ''Federico II'',  Naples, Italy, explain how the functionalisation of surfaces and taking control of nanostructured interfaces is an important part of nano-biotechnology. Writing aptly in the American Chemical Society journal Advanced Materials & Interfaces, they add that generating nanoscopic plasmonic structures for analyte detection usually requires complex fabrication techniques as well as the production of bio-activated nanostructures that take several steps to conjugate the required components using chemical ligation. They suggest that there is an alternative approach.

Specific suspension

The team explains that the adsorption of specific biomolecules can be used to decorate nanoparticles by exploiting the principles of molecular self-assembly at the solid-liquid interface of the nanoparticle in suspension. This approach would allow the nanoparticle to be functionalized for a particular application without itself modifying anything but the surface of the particle thus maintaining its desirable physical properties but adding a layer of chemical functionality. They suggest that the inherent nanoparticle chemistry, pH of the solution or salt concentration can all be kept the same but the functionalisation process can be robust and reversible.

As such, the team reports on how they have used peptides to directly and reversibly functionalise 20-nanometre gold nanoparticles so that they can tune the interfacial properties by simply adjusting the ratio between the numbers of peptide molecules to the number of gold nanoparticles in the mix. "This easy, direct and reversible assembly of gold nanoparticles mediated by the specific peptide - A-phi3 peptide - makes this platform ideal for small-volume samples and low concentrations detection using SERS as well as for the capture or separation of biomolecules in complex mixtures," the team says.

Potential experiments

The team used various experimental techniques, including, Z-potential measurements and fluorescence micro spectroscopy, UV-Vis absorption spectroscopy and transmission electron microscopy (TEM) to characterize in detail the resulting structures as well as the self-assembly processes involved in their formation and aggregation and subsequent disassembly. They demonstrated proof of principle for the use of these materials in SERS as well as in the separation of a specific protein, streptavidin, from a protein bath.

The reversibility of the self-assembly process and the fact that this can be controlled by selecting the ratio of added peptide to nanoparticles means that the spectrum of applications is much broader than it would otherwise be, the team adds. They point out that it also allows them to apply real-time regulation in experimental conditions. "Our final goal is to use the benefits of such an approach to build up, in a controlled fashion, composite nanostructures made up of different type of nanoparticles for diagnostic and biomedical  applications," Cause told SpectroscopNOW.

Related Links

Appl Mater Interfac, 2013, online: "Tuning Gold Nanoparticles Interfaces by Specific Peptide Interaction for Surface Enhanced Raman Spectroscopy (SERS) and Separation Applications"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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