Abstract

Gout is a condition that affects over 8 million Americans. This condition is characterized by severe pain, and in more advanced cases, bone erosion and joint destruction. This study explores the fabrication and characterization of an optical, enzymatic urate biosensor for gout management, and the optimization of the biosensor response through the tuning of hydrogel matrix properties. Sensors were fabricated through the co-immobilization of oxygen-quenched phosphorescent probes with an oxidoreductase within a biocompatible copolymer hydrogel matrix. Characterization of the spectral properties and hydrogel swelling was conducted, as well as evaluation of the response sensitivity and long-term stability of the urate biosensor. The findings indicate that increased acrylamide concentration improved the biosensor response by yielding an increased sensitivity and reduced lower limit of detection. However, the repeatability and stability tests highlighted some possible areas of improvement, with a consistent response drift observed during repeatability testing and a reduction in response seen after long-term storage tests. Overall, this study demonstrates the potential of an on-demand, patient-friendly gout management tool, while paving the way for a future multi-analyte biosensor based on this sensing platform.

Highlights

  • Uric acid is the end-product of purine nucleotide catabolism in humans

  • Uric acid mostly exists as its deprotonated resonance hybrid, urate, and associates with sodium ions to form monosodium urate (MSU) salts [3]

  • Some transporters involved in urate resorption include urate transporter 1 (URAT1) and GLUT9 (SLC2A9), a voltage-sensitive transporter

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Summary

Introduction

Uric acid is the end-product of purine nucleotide catabolism in humans. The compound, which is normally excreted by the kidneys or gastrointestinal tract, is produced by the liver from both exogenous and endogenous purine sources. Affecting over 8 million Americans, gout is characterized by severe pain, and in more advanced chronic cases, bone erosion and joint destruction [10,11] This inflammatory condition is triggered by MSU crystal deposits in the synovial spaces of the joints, which form when serum urate levels rise above their physiological solubility limit of 6.8 mg/dL. Portable urate test kits similar to commercially available glucose monitors could eliminate the need for expensive reagents and resources These devices require drawing blood samples and can reduce patient compliance due to the pain involved, in cases where the condition affects the joints in the hand. Through a systematic analysis of matrices comprising 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AAm) copolymers, this study focuses on investigating the practical effects of hydrogel matrix materials on these important characteristics of the urate with the goal of expanding the oxygen sensing platform for monitoring urate in chronic gout patients

Materials
Instrumentation
Hydrogel Selection
Hydrogel Fabrication
Swelling Ratio
Oxygen
Optical Measurements
Selectivity
2.10. Storage Stability
Absorbance and Emission Spectra of Urate Biosensors
Effect of Oxygen Concentration on Biosensor Response
Effect of Urate on Phosphorescence Lifetime
Storage Stability Results
Response stored in in urate solution dissolved in 10inmM
Methods

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