Grating-incoupled waveguide-enhanced Raman sensor.

We report a waveguide-enhanced Raman spectroscopy (WERS) platform with alignment-tolerant under-chip grating input coupling. The demonstration is based on a 100-nm thick planar (slab) tantalum pentoxide (Ta2O5) waveguide and the use of benzyl alcohol (BnOH) and its deuterated form (d7- BnOH) as reference analytes. The use of grating couplers simplifies the WERS system by providing improved translational alignment tolerance, important for disposable chips, as well as contributing to improved Raman conversion efficiency.

Au Nanoparticle-Based Amplified DNA Detection on Poly-l-lysine Monolayer-Functionalized Electrodes.

Affinity sensing of nucleic acids is among the most investigated areas in biosensing due to the growing importance of DNA diagnostics in healthcare research and clinical applications. Here, we report a simple electrochemical DNA detection layer, based on poly-l-lysine (PLL), in combination with gold nanoparticles (AuNPs) as a signal amplifier. The layer shows excellent reduction of non-specific binding and thereby high contrast between amplified and non-amplified signals with functionalized AuNPs; the relative change in current was 10-fold compared to the non-amplified signal.

Waveguide Enhanced Raman Spectroscopy for Biosensing: A Review.

Waveguide enhanced Raman spectroscopy (WERS) utilizes simple, robust, high-index contrast dielectric waveguides to generate a strong evanescent field, through which laser light interacts with analytes residing on the surface of the waveguide. It offers a powerful tool for the direct identification and reproducible quantification of biochemical species and an alternative to surface enhanced Raman spectroscopy (SERS) without reliance on fragile noble metal nanostructures. The advent of low-cost laser diodes, compact spectrometers, and recent progress in material engineering, nanofabrication techniques, and software modeling tools have made realizing portable and cheap WERS Raman systems with high sensitivity a realistic possibility.

Detection of Tumor DNA in Human Plasma with a Functional PLL-Based Surface Layer and Plasmonic Biosensing.

Standard protocols for the analysis of circulating tumor DNA (ctDNA) include the isolation of DNA from the patient's plasma and its amplification and analysis in buffered solutions. The application of such protocols is hampered by several factors, including the complexity and time-constrained preanalytical procedures, risks for sample contamination, extended analysis time, and assay costs. A recently introduced nanoparticle-enhanced surface plasmon resonance imaging-based assay has been shown to simplify procedures for the direct detection of tumor DNA in the patient's plasma, greatly simplifying the cumbersome preanalytical phase.

Clickable poly-l-lysine for the formation of biorecognition surfaces.

Biomolecules are immobilized onto surfaces employing the fast and stable adsorption of poly-l-lysine (PLL) polymers and the versatile copper-free click chemistry reactions. This method provides the combined advantages of versatile surface adsorption with density control using polyelectrolytes and of the covalent and orthogonal immobilization of biomolecules with higher reaction rates and improved yields of click chemistry. Using DNA attachment as a proof of concept, control over the DNA probe density and applicability in electrochemical detection are presented.

Low-fouling, mixed-charge poly-l-lysine polymers with anionic oligopeptide side-chains.

Biosensors and biomedical devices require antifouling surfaces to prevent the non-specific adhesion of proteins or cells, for example, when aiming to detect circulating cancer biomarkers in complex natural media (e.g., in blood plasma or serum).

Selective colorimetric NO(g) detection based on the use of modified gold nanoparticles using click chemistry.

A new colorimetric system for NO(g) detection is described. The detection method is based on the aggregation of modified AuNPs through a Cu(I) catalyzed click reaction promoted by the in situ reduction of Cu(II) by NO.