Enhanced multicolor resonant-optical-assay with direct text output.

The effectiveness of a novel multicolor biochip boosted by reducing cluster repulsion and in-situ silver enhancement has been demonstrated by using anti-serum albumine antibodies conjugated to gold nanoparticles on a vacuum metalized plastic film coated with nano-resonance driving ceramic multilayers. A dense and smooth vacuum deposited SiO approximately 1.6 top layer (50 to 300 nm thick) on a flexible thermoplastic polymer poly-ethylene-terephthalate-chip functionalized via poly-ethylenimine monolayer coating and chemical cross-linking was employed to immobilize capture antibodies. Following capturing of the human serum albumin antigen from analyte solution, the multicolor chip reacts with anti HSA-gold nanoparticles binding them in a nanometric distance to the resonant mirror of the device-visible to the eye as faint coloring of the chip surface. Following silver enhancement, a strong metallic angle-dependent color via Resonance Enhanced Absorption is observed. In this study, silver staining has been used for the first time to boost and shift the color of nano-resonance enhanced optical bioassays. The use of silver staining increases and significantly modifies the intensity of the resonance color and was done in less than 5 minutes directly on the chip. This novel methodology will find broad application in Point-of-Care diagnostic devices via a color signal output designed as a written text with high contrast to replace standard lateral flow devices just showing lines or dots.

From lateral flow devices to a novel nano-color microfluidic assay.

Improving the performance of traditional diagnostic lateral flow assays combined with new manufacturing technologies is a primary goal in the research and development plans of diagnostic companies. Taking into consideration the components of lateral flow diagnostic test kits; innovation can include modification of labels, materials and device design. In recent years, Resonance-Enhanced Absorption (REA) of metal nano-particles has shown excellent applicability in bio-sensing for the detection of a variety of bio-molecular binding interactions. In a novel approach, we have now integrated REA-assays in a diagnostic microfluidic setup thus resolving the bottleneck of long incubation times inherent in previously existing REA-assays and simultaneously integrated automated fabrication techniques for diagnostics manufacture. Due to the roller-coating based technology and chemical resistance, we used PET-co-polyester as a substrate and a CO(2) laser ablation system as a fast, highly precise and contactless alternative to classical micro-milling. It was possible to detect biological binding within three minutes - visible to the eye as colored text readout within the REA-fluidic device. A two-minute in-situ silver enhancement was able to enhance the resonant color additionally, if required.

Structural behavior of nanometric carbohydrate films transduced by a resonant technique.

New optical nanoresonance effects enabled us to study the effect of ions on nanometric carbohydrate thin layers on chips. Immobilization was done via spin coating of the derivatized carbohydrate polymer at a metallized chip surface forming ultrathin films (about 50-300 nm thick) followed by photochemical cross-linking. Deposition of metal-nanoclusters, synthesized by chemical means and sputter coating on top of the polymer, induced an optical resonance effect, which transduced changes of polymer structure quantitatively into an optical signal that can be observed directly as resonance shift of a narrow optical peak. The response of the sensor chip even visible to the eye was quantified spectroscopically in the visible and ir range of the spectrum. The lifetime of thin film was good, and thus application as a sensor was limited only by the mechanical stability of the reactive matrix, but not by photobleaching or molecular leakage. Due to the inherent hydrophilic nature of the alginate polymer, the response time of this new sensor is governed by simple aqueous diffusion of the ionic calcium for up to 300 nm completed within less than one second. Monitoring of calcium fluctuations in a high background of magnesium and even serum was demonstrated with a dynamic range optimal for physiological measurements and a linear response up to 5 mM. Surface and alignment of polymer chain were influenced by the nanostructure of the supporting metal film-contrary to alginic acid, chitosan was deposited well aligned to the nanocrystals of the support.