Nanoporous Gold Disks Functionalized with Stabilized G-Quadruplex Moieties for Sensing Small Molecules

Abstract

We report label-free small molecule sensing on nanoporous gold disks functionalized with stabilized Guanine-quadruplex (G4) moieties using surface-enhanced Raman spectroscopy (SERS). By utilizing the unique G4 topological structure, target molecules can be selectively captured onto nanoporous gold (NPG) disk surfaces via π-π stacking and electrostatic attractions. Together with high-density plasmonic "hot spots" of NPG disks, the captured molecules produce a remarkable SERS signal. Our strategy represents the first example of the detection of foreign molecules conjugated to nondouble helical DNA nanostructures using SERS while providing a new technique for studying the formation and evolution of G4 moieties. The molecular specificity of G4 is known to be controlled by its unit sequence. Without losing generality, we have selected d(GGT)GG sequence for the sensing of malachite green (MG), a known carcinogen frequently abused illegally in aquaculture. The newly developed technique achieved a lowest detectable concentration at an impressive 50 pM, two orders of magnitude lower than the European Union (EU) regulatory requirement, with high specificity against potential interferents. To demonstrate the translational potential of this technology, we achieved a lowest detectable concentration of 5.0 nM, meeting the EU regulatory requirement, using a portable probe based detection system.

Ultrasensitive and reproducible SERS platform of coupled Ag grating with multibranched Au nanoparticles

“…[5][6][7][8][9][10] Taking into account the basic requirements for the analysis of these compounds, an analytical approach must satisfy several requirements: (i) be fast and straightforward, (ii) achieve the detection limits that are as low as possible, and (iii) give reproducible and reliable results. SERS satisfies two of these three requirements: recent progress in this field allows taking measurements using the portable spectrophotometers, 11,12 and with up to one-molecule-level sensitivity, which was implemented in the last millennium. 13,14 However, the last requirement of reproducibility remains one of the biggest challenges in the SERS field.…”

Directed assembly and concentrating of micro/nanoparticles, cells, and vesicles via low-power near-infrared laser generated plasmonic microbubbles

“…As shown in SEM and LSPR peak mapping, the cluster altered the extinction spectra through plasmonic coupling between AuNP-AuNP and AuNP-NPGD with 50 to 100 nm red shifts compared to the bare NPGD substrate, and 200 nm red shifts compared to non-aggregated, colloidal AuNP. The clusters showed a high SERS active region with intensity amplification 5 times that of bare NPGD which was shown to have a SERS enhancement factor exceeding 10 8 [31]. We have also demonstrated the feasibility of using this platform to collect and concentrate biological organisms such as microscale E. coli.…”

“…The map shows AuNP clusters with approximately 5 times the SERS intensity of bare NPGD (Fig. 7c), which has been shown to have a SERS enhancement factor exceeding 10 8 [31]. The outer region of AuNP clusters appear to have a thin layer of AuNP attached to the NPGD that shows higher SERS signal compared to bare NPGD (Fig.…”

“…The semirandom porous network has a characteristic length of 5-15 nm and has been shown to provide significant plasmonic field localization. NPGD array has been demonstrated to be highly effective in surface-enhanced Raman spectroscopy [31], surface-enhanced fluorescence [32], surface-enhanced near infrared absorption [13], plasmon-enhanced heterogeneous catalysis [33], and photothermal heating [10,34,35]. Thanks to the highly tunable LSPR of the NPGD array, microbubble of controlled size can be generated by near-infrared (NIR) light.…”

3D Plasmonic Nanoarchitecture As an Emerging Biosensing Platform

“…NPG arrays have been demonstrated in various plasmonic sensing mechanisms such as refractive index sensing via extinction spectroscopy, as well as spectroscopic fingerprinting by enhanced fluorescence, NIR absorption, and Raman spectroscopy [8][9][10][11]14]. A number of label-free biosensing applications have been developed in the past 4 years for nucleic acids, proteins, enzymes, metabolites, neurotransmitters, polycyclic aromatic hydrocarbons, carcinogenic environmental and food contaminants, and etc [11,[19][20][21][22][23].…”