Monitoring cellulose oxidation for protein immobilization in paper-based low-cost biosensors
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ORIGINAL PAPER
Monitoring cellulose oxidation for protein immobilization in paper-based low-cost biosensors Amanda Hikari Imamura 1,2 & Thiago Pinotti Segato 1,2 Frank Nelson Crespilho 1 & Emanuel Carrilho 1,2
& Letícia Jordão Marques de Oliveira
1,2
& Ayaz Hassan
1
&
Received: 4 September 2019 / Accepted: 30 March 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The oxidation of paper by periodate was investigated and systematically characterized by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy, X-ray diffraction, goniometry, and dynamic mechanical analysis. For the first time, in situ FTIR microscopy analysis was performed, yielding chemical images of carbonyl groups on the cellulose fibers. The enhancement of protein immobilization on oxidized paper was quantified by a colorimetric assay with Ponceau dye, demonstrating that 0.5-h oxidation suffices to functionalize the paper-based devices. The oxidized paper was applied as a sensor for protein quantification in urine, a test able to detect levels of proteinuria and even microalbuminuria. The quantification was based on the capture of proteins through covalent bonds formed with the carbonyl groups on the oxidized paper followed by the staining of the region with Ponceau dye. There is a linear dependency between human serum albumin (HSA) concentration and the length of the stained blot from 0.1 to 3 mg mL−1. This method correlated linearly with a reference method showing a higher sensitivity (0.866 cm mL mg−1) than the latter. The limit of quantification was 0.1 mg mL−1, three times lower than that of the commercial strip. Keywords Paper-based analytical devices . Periodate . Protein immobilization . Proteinuria . Microalbuminuria . Colorimetric assay
Introduction The use of paper as a substrate for analytical purposes has been reported since the 1850s with the creation of urine test strips [1]. In the early 1900s, paper began to be widely used for chromatography and electrophoresis [2], and a few years later, the pH paper test was introduced and commercialized [3]. However, 10 years ago, Whitesides and co-works reintroduced paper as a low-cost substrate for inexpensive, low-volume, portable, and multiple assay microfluidic devices
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04250-6) contains supplementary material, which is available to authorized users. * Emanuel Carrilho [email protected] 1
Instituto de Química de São Carlos, Universidade de São Paulo, Av. Trabalhador São-Carlense, 400, São Carlos, SP 13566-590, Brazil
2
Instituto Nacional de Ciência e Tecnologia em Bioanalítica – INCTBio, Campinas, SP 13083-970, Brazil
[4]. Since then, several studies centered on the use of paper as a substrate for point-of-care (POC) testing have been published, and the field of paper microfluidics has emerged. The popularity of the microfluidic paper-based analytical devices (μPADs) is mainly due to its capacity of explore the capillarity of t
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