Portable paper sensors for the detection of heavy metals based on light transmission-improved quantification of colorimetric assays.

An accurate quantification method with a wide linearity range is paramount for the development of low-cost, portable and point-of-care sensors. This work reports a new approach to analyze the colorimetric assays on paper-based sensors using the quantification from a light transmission method. Compared to the commonly-developed color intensity measurement on scanned digital images, a portable transmission densitometer is capable of directly quantifying the optical density of colorimetric results.

Visualization and Quantification of IgG Antibody Adsorbed at the Cellulose-Liquid Interface.

Quantification of adsorbed biomolecules (enzymes, proteins) at the cellulose interface is a major challenge in developing eco-friendly biodiagnostics. Here, a novel methodology is developed to visualize and quantify the adsorption of antibody from solution to the cellulose-liquid interface. The concept is to deuterate cellulose by replacing all nonexchangeable hydrogens from the glucose rings with deuterium in order to enhance the scattering contrast between the cellulose film surface and adsorbed antibody molecules.

Smooth deuterated cellulose films for the visualisation of adsorbed bio-macromolecules.

Novel thin and smooth deuterated cellulose films were synthesised to visualize adsorbed bio-macromolecules using contrast variation neutron reflectivity (NR) measurements. Incorporation of varying degrees of deuteration into cellulose was achieved by growing Gluconacetobacter xylinus in deuterated glycerol as carbon source dissolved in growth media containing DO. The derivative of deuterated cellulose was prepared by trimethylsilylation(TMS) in ionic liquid(1-butyl-3-methylimidazolium chloride).

Adsorption of cationic polyacrylamide at the cellulose-liquid interface: a neutron reflectometry study.

The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose-water interface was quantified by neutron reflectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13 MD) but different charge densities, adsorbed with or without NaCl (10(-3) M), was studied. Thin cellulose films (40±7 Å) of roughness <10 Å were produced by spin coating a cellulose acetate-acetone solution and regenerating by alkaline hydrolysis.