Enhanced Immunoassay Using a Rotating Paper Platform for Quantitative Determination of Low Abundance Protein Biomarkers

Abstract

The changing concentrations of circulating protein biomarkers have been correlated with a variety of diseases. Quantitative bioassays capable of sensitive and specific determination of protein biomarkers at low levels can be essential for therapeutic treatments that can improve outcomes for patients. Herein, we describe the investigation of a rotating paper device (RPD) for quantitative determination of targeted proteins at the fM concentration level. The RPD consists of two circular papers each separately supported with a plastic disc. Protein detection is conducted via enhanced immunoassay using amplification in a sequential workflow, which includes a sandwich immunoassay in the upper paper and a signal amplification reaction in the lower paper. The sandwich immunoassay is conducted using biobarcode nanoparticles (BNPs) and results in the release of reporter oligonucleotides from BNPs. These oligonucleotides are transferred to the bottom paper, where they engage in a target recycling methodology that leads to the production of a colorimetric signal. The assay was evaluated for quantitation of interleukin-6 (IL-6), a cytokine biomarker in serum. A limit of detection of 63 fM and a dynamic range of 200 fM–8 pM was observed for the assay. The specificity of the assay was successfully verified against several common protein biomarkers.

Multifunctional Droplet Microfluidic Platform for Rapid Immobilization of Oligonucleotides on Semiconductor Quantum Dots

“…The platform is used for conjugating not only oligonucleotide−QD but also possibly for conjugating oligonucleotide to other nanoparticles such as gold nanoparticles. 56 Furthermore, it could also be applied to other biochemical assays requiring two-step reactions. The idea of "plug and collect" is clearly demonstrated through this work, allowing oligonucleotide−QD conjugates to be produced without environmental effects and tedious manual processes.…”

“…One of the benefits of this droplet microfluidic platform is the integration of multiple functions enabled by the continuous flow nature. The platform is used for conjugating not only oligonucleotide–QD but also possibly for conjugating oligonucleotide to other nanoparticles such as gold nanoparticles . Furthermore, it could also be applied to other biochemical assays requiring two-step reactions.…”

Combined Paper Centrifugal Chromatographic Separation and SERS Detection for Multicomponent Substances

“…Inspired by the operating mode of a centrifuge, in 2017, the Prakash group reported an inexpensive paper centrifuge that could rapidly separate blood samples and successfully diagnose malaria . Following this discovery, several related studies were carried out, and paper centrifuge systems were successfully applied in the fields of clinical diagnosis, biology, and food monitoring. − However, to date, the reported paper centrifuges do not have chromatographic separation capabilities and cannot be used directly for the separation of mixtures or for qualitative analysis. Therefore, the development of a method that can be employed for multicomponent chromatographic separation and qualitative analysis based on paper centrifugation would undoubtedly be beneficial for the advancement of “frugal science”.…”