Graduation Year

2025

Document Type

Thesis

Degree

M.S.M.E.

Degree Name

MS in Mechanical Engineering (M.S.M.E.)

Degree Granting Department

Mechanical Engineering

Major Professor

Ali Ashraf, Ph.D.

Co-Major Professor

Ashok Kumar, Ph.D.

Committee Member

Wilfrido Moreno, Ph.D.

Committee Member

Piyush Koria, Ph.D.

Keywords

Biomarker Detection, Electrochemical Analysis, Nanomaterials, Point-of-Care Diagnostics, Polyaniline Modification

Abstract

Monitoring wound healing is critical for improving patient outcomes, especially for chronic wounds, which often have complications like delayed healing and infections. Current methods for monitoring wound healing are invasive and costly. Also, these methods have a limited ability to provide real-time, continuous data. This study seeks to explore a graphene screen-printed electrode (SPE) electrochemical biosensor that is non-invasive and efficient to constantly monitor wound healing in real time. This research study focuses specifically on the electrochemical detection of the Human Neutrophil Elastase (HNE) and Secretory Leukocyte Protease Inhibitor (SLPI), which is one of the most abundant neutral proteinases in chronic wounds. Studies have found that Human Neutrophil Elastase (HNE) activity is elevated in chronic wounds, while diminished in healing wounds. Investigating the electrochemical responses of Human Neutrophil Elastase (HNE) and Secretory Leukocyte Protease Inhibitor (SLPI) could lead to a possible marker regarding severe wound inflammation or infection.In this study, two different conductive polymer-based graphene inks were prepared: PEDOT:PSS and polyaniline (PANI). Cyclic voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) testing showed that the PANI-based ink was more conductive than the PEDOT:PSS. Thus, graphene PANI ink is a preferred choice regarding further sensor development. An optimized volume of PANI-graphene ink was established to achieve surface stability and ensure good conductivity. The electrode surface was functionalized using EDC/NHS chemistry to enable biomolecule immobilization. The sensors were tested at different HNE and SLPI antigen concentrations to determine the sensors' sensitivity, selectivity, and dynamic range of detection. The results have shown that the impedance response increased with HNE and SLPI concentration, confirming antigen binding and verifying the sensor’s good sensitivity with a wide detection range. LOD were calculated at 0.76 ng/mL for HNE detection and 0.37 ng/mL for SLPI detection. The reproducibility results yielded an RSD of approximately 3.3% across three sensors. This work seeks to develop an electrochemical platform that is reliable and reproducible for detecting HNE and SLPI as a wound biomarker. PANI-graphene ink offers a combination of both conductivity and stability. This combination shows its potential for point-of-care wound monitoring applications.

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