A Conductive Hydrogel-Based Microneedle Platform for Real-Time pH Measurement in Live Animals

Sarah Odinotski, Karan Dhingra, Amin GhavamiNejad, Hanjia Zheng, Peyman GhavamiNejad, Hager Gaouda, Dorsa Mohammadrezaei, Mahla Poudineh*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Conventional microneedles (MNs) have been extensively reported and applied toward a variety of biosensing and drug delivery applications. Hydrogel forming MNs with the added ability to electrically track health conditions in real-time is an area yet to be explored. The first conductive hydrogel microneedle (HMN) electrode that is capable of on-needle pH detection with no postprocessing required is presented here. The HMN array is fabricated using a swellable dopamine (DA) conjugated hyaluronic acid (HA) hydrogel, and is embedded with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to increase conductivity. The catechol-quinone chemistry intrinsic to DA is used to measure pH in interstitial fluid (ISF). The effect of PEDOT:PSS on the characteristics of the HMN array such as swelling capability and mechanical strength is fully studied. The HMN's capability for pH measurement is first demonstrated using porcine skin equilibrated with different pH solutions ranging from 3.5 to 9. Furthermore, the HMN-pH meter is capable of in vivo measurements with a 93% accuracy compared to a conventional pH probe meter. This HMN technology bridges the gap between traditional metallic electrochemical biosensors and the direct extraction of ISF, and introduces a platform for the development of polymeric wearable sensors capable of on-needle detection.

Original languageEnglish (US)
Article number2200201
Issue number45
StatePublished - Nov 10 2022


  • catechol-quinone chemistry
  • conductive hydrogel microneedles
  • interstitial fluid
  • on-needle sensing
  • pH-sensing
  • real-time measurements

ASJC Scopus subject areas

  • General Chemistry
  • Biotechnology
  • General Materials Science
  • Biomaterials


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