# Engineered Nanofiber-Hydrogel Systems for Colorimetric Lactate Sensing from Breath

## TL;DR

A new nanofiber-hydrogel system detects lactate in breath for noninvasive monitoring of airway inflammation.

## Contribution

A colorimetric lactate sensing platform using engineered nanofibers and enzyme-entrapping hydrogels for breath analysis.

## Key findings

- Nanofibers efficiently capture lactate through electrostatic interactions.
- The system achieves a detection limit of 5 μmol·L–1 in solution and 20 μmol·L–1 in the hydrogel-based system.
- The platform outperforms other materials in analyte capture and breathability.

## Abstract

Current methods for detecting chronic airway inflammation,
such
as asthma, rely on complex procedures and specialized clinicians.
Taking advantage of inherent nanomaterial properties and their chemical
design flexibility, nanofibers were designed and integrated with enzyme
entrapping hydrogels. This composition offers noninvasive sample collection
followed by simple colorimetric detection. Specifically, nanofibers
were made from positively charged nylon-poly­(allylamine hydrochloride).
They were optimized with respect to mat thickness, additive content,
and lactate capture efficiency. The nanofibers could efficiently bind
lactate through electrostatic interaction, correlating the resulting
amount on the nanofiber mat to the concentration in breath aerosols.
Detection was subsequently accomplished through a standard lactate
oxidase, horseradish peroxidase assay with 3,3′,5,5′-tetramethylbenzidine
colorimetric detection. The optimized nanofibers outperformed other
polymeric nanofibers, face mask material, and filter paper regarding
analyte capture and breathability due to the surface chemistry chosen
and the high surface area afforded through the nanofiber mats. For
lactate quantification directly on the mask, lactate oxidase was immobilized
on the nanofiber mat via a hydrogel, ensuring long-term storage stability.
Simple visual detection was achieved providing limits of detection
of 5 μmol·L–1 (in solution) and 20 μmol·L–1 (hydrogel-based system) and a dynamic range that
covers lactate concentrations found in breath, i.e., 5 to 150 μmol·L–1. This platform technology offers a promising solution
for point-of-care diagnostics, contributing to remote healthcare,
telemedicine, and simplified diagnostics in airway inflammation management.