The realization of an innovative label- and PCR-free silicon nanowires (NWs) optical biosensor for direct genome detection is demonstrated. The system is based on the cooperative hybridization to selectively capture DNA and on the optical emission of quantum confined carriers in Si NWs whose quenching is used as detection mechanism. The Si NWs platform was tested with Hepatitis B virus (HBV) complete genome and it was able to reach a Limit of Detection (LoD) of 2 copies/reaction for the synthetic genome and 20 copies/reaction for the genome extracted from human blood. These results are even better than those obtained with the gold standard real-time PCR method in the genome analysis. The Si NWs sensor showed high sensitivity and specificity, easy detection method, and low manufacturing cost fully compatible with standard silicon process technology. All these points are key factors for the future development of a new class of genetic point-of-care devices that are reliable, fast, low cost, and easy to use for self-testing including in the developing countries.
Silicon
nanowires are held and manipulated in controlled optical
traps based on counter-propagating beams focused by low numerical
aperture lenses. The double-beam configuration compensates light scattering
forces enabling an in-depth investigation of the rich dynamics of
trapped nanowires that are prone to both optical and hydrodynamic
interactions. Several polarization configurations are used, allowing
the observation of optical binding with different stable structure
as well as the transfer of spin and orbital momentum of light to the
trapped silicon nanowires. Accurate modeling based on Brownian dynamics
simulations with appropriate optical and hydrodynamic coupling confirms
that this rich scenario is crucially dependent on the non-spherical
shape of the nanowires. Such an increased level of optical control
of multiparticle structure and dynamics open perspectives for nanofluidics
and multi-component light-driven nanomachines.
We demonstrate the realization of the first label-free optical biosensor based on the room temperature luminescence of silicon nanowires (NWs) tested for the selective detection of C-reactive protein in human serum. High aspect ratio Si NW arrays used as sensing interface, are synthesized by a fast, low cost and Si industrially compatible approach. Si NW optical biosensors are fast and offer a broad concentration dynamic range that can be tuned according to different applications. Moreover, the platform is endowed with a high selectivity toward the target analyte and a sensitivity down to the fM limit of detection, opening the route toward noninvasive analysis in biofluids such as saliva.
Silicon is the undisputed leader for microelectronics among all the industrial materials and Si nanostructures flourish as natural candidates for tomorrow’s technologies due to the rising of novel physical properties at the nanoscale. In particular, silicon nanowires (Si NWs) are emerging as a promising resource in different fields such as electronics, photovoltaic, photonics, and sensing. Despite the plethora of techniques available for the synthesis of Si NWs, metal-assisted chemical etching (MACE) is today a cutting-edge technology for cost-effective Si nanomaterial fabrication already adopted in several research labs. During these years, MACE demonstrates interesting results for Si NW fabrication outstanding other methods. A critical study of all the main MACE routes for Si NWs is here presented, providing the comparison among all the advantages and drawbacks for different MACE approaches. All these fabrication techniques are investigated in terms of equipment, cost, complexity of the process, repeatability, also analyzing the possibility of a commercial transfer of these technologies for microelectronics, and which one may be preferred as industrial approach.
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