Fully inkjet-printed glucose assay fabricated on highly porous pigment coating

Eveliina Jutila,Roger Bollström,Patrick Gane,Risto Koivunen

doi:10.1007/s10404-020-02344-4

Eveliina Jutila, Roger Bollström + Show 2 more

Open Access

https://doi.org/10.1007/s10404-020-02344-4

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Abstract

A simple paper-based microfluidic device, fabricated on a highly porous coating consisting of functionalised calcium carbonate (FCC) pigment and a microfibrillated cellulose (MFC) and/or polyvinyl alcohol (PVOH) binder, was developed for glucose detection. Both the hydrophobic patterns, consisting of alkyl ketene dimer (AKD), and the enzyme ink, consisting of glucose oxidase (GOx), horseradish peroxidase (HRP) and an indicator containing 4-aminoantipyrine (4-AAP), and sodium 3,5-dichloro-2-hydroxy-benzenesulphonic acid (DHBS) were inkjet-printed. Multiple coating formulations were tested using two indicators, potassium iodide (KI) and 4-AAP/DHBS, to find the optimal formulation with regard to detection sensitivity and assay stability. Higher binder concentrations increased the enzyme activity, especially in the case of PVOH. Two coatings, containing either solely MFC or both MFC and PVOH were ultimately chosen for the glucose assay experiments. For the assays, a 42 nl volume of buffered enzyme solution, containing a total of 5.04 mU GOx and approximately 1.01 mU HRP, in combination with 4 mM 4-AAP and 8 mM DHBS, was printed, and a 1 µl glucose solution, made up over a range of concentrations, was applied onto the samples to evaluate the response. A good linearity was achieved between detection and glucose concentration between 0.1 and 0.6 mM with both coatings. The assays remained stable for four weeks when stored at − 20 °C. The results show that the functional coated substrates offer a viable alternative to cellulose-based substrates for microfluidic applications enabling the use of small reagent and sample volumes.

Highlights

Microfluidic paper-based analytical devices are simple, convenient tools, which are based on capillary-driven flow of fluids on hydrophilic surfaces
We demonstrate that coatings comprising highly porous pigment particles can be utilised as optimisable microfluidics platforms, exemplified in the form of a glucose assay, using an inkjet printer both to pattern the coating with hydrophobic ink and to deposit both the enzymes and detection reagents, with the advantages of good linear sensitivity, while utilising smaller enzyme and glucose sample volumes than previously reported
The assay construct consists of formulated alkyl ketene dimer (AKD) ink as hydrophobising agent for microfluidic channel boundaries, and reagent components consisting of glucose oxidase (GOx), horseradish peroxidase (HRP) and a 4-AAP/dichloro-2-hydroxy-benzenesulphonic acid (DHBS) indicator

Summary

Introduction

Microfluidic paper-based analytical devices (μPADs) are simple, convenient tools, which are based on capillary-driven flow of fluids on hydrophilic surfaces. The devices provide easy-to-use solutions for POC and onsite testing, especially for resource-poor settings and developing countries. They provide a viable option to conventional instrumentation, while still offering sensitivity, reproducibility and low limits of detection (Syedmoradi and Gomez 2017). The miniaturisation of the diagnostic instruments provides affordable versions of diagnostic tools with rapid detection, and enables the use of small sample and reagent volumes further reducing the costs of testing and diagnosis

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