# Fluorescent Polymeric Nanofibers as Ratiometric Multiplexed Skin Sensors of pH and Oxygen

## TL;DR

This paper introduces fluorescent nanofibers that can simultaneously monitor pH and oxygen levels in wounds, enabling remote tracking of healing progress.

## Contribution

The development of dual FRET-based nanofibers for ratiometric and multiplexed sensing of pH and oxygen in biomedical contexts.

## Key findings

- Nanofibers use dual FRET to amplify signals for pH and oxygen detection.
- A multiplexing device was created to sense both parameters in a wound model.
- The materials are compatible with smartphone-based detection for practical biomedical use.

## Abstract

Monitoring wound healing requires the development of multiplexed sensors with remote readout. Here, we report fluorescent polymeric nanofibers and nanorods as ratiometric sensors of two important physiological parameters: pH and oxygen. These nanofibers operate by dual Forster resonance energy transfer (FRET) between large number of energy donor dyes (reference) and limited number of two distinct energy acceptors sensitive to these two analytes. This configuration ensures signal amplification of analyte‐sensitive energy acceptor by light‐harvesting principle. The oxygen sensor is based on encapsulation of cationic donor dyes (cyanine or rhodamine derivatives) with bulky hydrophobic counterions as FRET donors and Pt‐porphyrins as energy acceptors inside the nanofibers. In the pH sensor, nanofibers loaded with donor dyes are functionalized at the surface with the rhodamine‐derived energy acceptor, which ensures sensitivity to pH. The developed nanosensors show ratiometric response to the analytes by changing the intensity ratio of the analyte‐sensitive acceptor vs the reference donor dye. Finally, a multiplexing device combining oxygen‐ and pH‐sensing modalities is developed, which enable sensing both pH and oxygen in a wound model by recording its emission in the red, green, and blue channels. The obtained materials will find numerous biomedical applications, including monitoring wound healing, compatible with simple smartphone‐based detection.

Fluorescent polymeric nanofibers and nanorods are produced as ratiometric sensors of two important physiological parameters: pH and oxygen. They operate by dual Forster resonance energy transfer from large number of energy donor dyes to limited number of two distinct energy acceptors, enabling simultaneous sensing of pH and oxygen. These materials could find numerous biomedical applications, including monitoring wound healing.