Gold Nanoparticles Assembly on Silicon and Gold Surfaces: Mechanism, Stability, and Efficiency in Diclofenac Biosensing

Abstract

We investigated the assembly of Gold nanoparticles (AuNPs) on Gold and Silicon sensors with two final objectives: (i) understanding the factors governing the interaction and (ii) building up a nanostructured piezoelectric immunosensor for diclofenac, a small-sized pharmaceutical pollutant. Different surface chemistries were devised to achieve AuNPs assembly on planar substrates. These surface chemistries included amines to immobilize AuNPs via electrostatic interaction, or a mixture of amines and thiols to covalently attach the AuNPs. We also generated PEG-amine terminated surfaces to benefit from the well-known non-biofouling properties of PEG-coated surfaces. The functional substrates and the resulting gold nanoparticle layers were characterized in detail by Surface IR, contact angle measurements and Scanning Electron Microscopy (SEM). The mechanism of adsorption is discussed herein considering the nature of the terminal groups and their charge at the pH of AuNPs adsorption. The coverage and the dispersion of AuNPs were strongly dependent on the anchoring points on the surfaces; the optimal were reached when the attachment layer offered multiple interaction points, in particular, for NH 2 /SH and PEG/NH 2 terminated surfaces, where the percentage of isolated particles was up to 78 %. In addition, PEG-coated surfaces led to a stable AuNPs layer resistant to ultrasounds and to further functionalization of the immobilized nanoparticles. These surfaces were used to engineer quartz crystal microbalance (QCM) biosensors for diclofenac detection. The AuNPs nanostructured substrates significantly enhanced the biosensor sensitivity as compared to planar substrates (up to 6 times higher). This enhancement presages a higher sensitivity in the competitive detection of diclofenac on these systems. More importantly, despite the biorecognition and the drastic regeneration conditions, SEM images show that gold nanoparticles layers are stable and reliable, which paves the way for their use as nanostructured platforms for multiple applications.

Gold colloid-nanostructured surfaces for enhanced piezoelectric immunosensing of staphylococcal enterotoxin A

“…The corresponding SEM images ( Regardless the method of AuNP deposition, silicon-modified surfaces adsorb a higher amount of particles than gold ones. We previously observed this behavior and attributed it to the difference of chemical groups on the two substrates: silane addition to silica chemistry offers multiple anchoring points including silanolate in addition to the amine and thiol groups, while for gold only the latter are present [49].…”

“…This strategy was used to design an immunosensor for the competitive detection of diclofenac, a small pharmaceutical pollutant [49]. Unfortunately, we could not use this strategy in the present case as all the attempts to graft proteins to these nanostructured substrates following the procedure described below were unsuccessful, most probably because of the well-known protein repulsive property of PEG films.…”

“…Regarding piezoelectric sensors, inclusion of gold nanoparticles has been shown to increase their sensitivity owing to surface [34][35][36][37][38][39][40][41][42] or mass [31,[43][44][45][46][47][48] enhancement effects. Using gold nanoparticlesnanostructured surfaces, we successfully built up a piezoelectric immunosensor for the antiinflammatory drug diclofenac with a sensitivity up to 6 times that reached with planar substrates [49]. Furthermore, thanks to the biocompatibility of AuNPs, biomolecules immobilized on such platforms are less prone to lose their bioactivity.…”

Gold nanoparticle-based localized surface plasmon immunosensor for staphylococcal enterotoxin A (SEA) detection

“…Colloidal gold nanoparticles were prepared according to the citrate / tannic acid reduction method adapted from [18] and described previously [19].…”

Modulating the Kinetics of Nanoparticle Adsorption for Simple and High‐Yield Fabrication of Plasmonic Heterostructures as SERS Substrates

“…QCMw ith dissipation monitoring (QCM-D) provides additional information about the viscoelastic character of the mass adsorptionf rom the liquid phase. [29][30][31] We used as ensor coated with at hin film of SiO 2 to resemble the appropriate chemistry for grafting the polymer chains. The sensor was chemically functionalized with PEG chains by spin-coating af ilm of the polymer followed by thermal annealing and washing as described above.…”