# A Nanoparticle-Based Immunoassay on Facemasks for Evaluating Neutrophilic Airway Inflammation in COPD Patients

## TL;DR

A new non-invasive method uses facemasks and nanoparticles to detect lung inflammation in COPD patients, avoiding the need for sputum analysis.

## Contribution

A novel immunoassay on facemasks enables quantification of exhaled myeloperoxidase (MPO) for diagnosing neutrophilic airway inflammation in COPD.

## Key findings

- The method successfully differentiated COPD exacerbation patients from stable ones with 100% sensitivity and specificity.
- Healthy individuals had significantly lower MPO levels compared to COPD patients.
- The dynamic range of MPO detection reached up to 3 · 101 µg·mL−1.

## Abstract

Patients with chronic obstructive pulmonary disease (COPD) often experience acute exacerbations characterized by elevated neutrophilic inflammation in the lungs. Currently, this condition is diagnosed through visual inspection of sputum color and volume, a method prone to personal bias and unsuitable for patients who are unable to expectorate spontaneously. In this manuscript, we present a novel approach for measuring and monitoring exhaled myeloperoxidase (MPO), a biomarker of neutrophilic airway inflammation, without the need for sputum analysis. The method involves analyzing an unmodified surgical facemask worn by the patient for 30 min using biosensing decals that transfer antibody-coated nanoparticles. These colloids specifically interact with MPO trapped by the facemask in a dose-dependent manner, enabling the quantification of MPO levels, with a dynamic range up to 3 · 101 µg·mL−1. The proposed diagnostic approach successfully differentiated patients with acute exacerbations from stable patients with 100% sensitivity and specificity. Healthy individuals also showed significantly lower MPO levels compared to COPD patients. Our results suggest that facemask analysis could be a non-invasive diagnostic tool for airway diseases, particularly in patients unable to expectorate.