Biosensing & Printed Electronics

Printed Carbon Electrochemical Aptasensors for tRNA-Derived Fragments

A graduate thesis and follow-on journal work developing low-cost printed electrochemical biosensors for detecting tRNA-derived fragments, reaching a 0.4 nM limit of detection on a screen-printed carbon platform.

By Musa Ibne Mannan · Erik Jonsson School of Engineering and Computer Science, The University of Texas at Dallas

The target

tRNA-derived fragments (tRFs) were long dismissed as degradation debris. They are now understood to be regulatory molecules in their own right, and their expression patterns carry diagnostic signal — which makes detecting them at low concentration clinically interesting. The barrier is not whether detection is possible but what it costs. Established nucleic acid detection methods require laboratory infrastructure, trained operators and time. A printed electrochemical sensor changes that calculus: if the electrode can be printed and the readout is a current measurement, the platform becomes cheap enough to deploy at the point of care.

This line of work ran across two projects, moving from an inkjet-printed graphene platform to a screen-printed carbon one, with the second achieving substantially better analytical performance.

Inkjet-printed graphene aptasensor

My master's thesis at Texas State University presented an early-stage graphene-based biosensing platform for in-vitro RNA detection. The work centred on two problems that dominate printed bioelectronics.

The first was electrode quality. Inkjet-printed graphene electrodes have to be optimized for the competing demands of conductivity, surface area and print consistency — ink formulation, deposition parameters and post-print treatment all shift the electrochemically active surface. The second was signal quantification: converting an electrochemical response into a defensible concentration measurement requires establishing that the signal tracks target binding rather than nonspecific adsorption or electrode drift.

The thesis established the platform as viable and identified where its performance was limited, which directly informed the change of approach in the follow-on work.

Multifunctionalized screen-printed carbon

The subsequent study, co-developed with colleagues and submitted to Surfaces and Interfaces, moved to a screen-printed carbon electrode with a deliberately engineered surface chemistry. Rather than relying on the printed carbon surface as deposited, the electrode was activated by oxygen plasma treatment and then functionalized using EDC/NHS coupling chemistry.

That two-step approach does something specific: oxygen plasma generates carboxyl functionality on the carbon surface, and EDC/NHS converts those groups into amine-reactive esters that covalently anchor the recognition element. Covalent attachment gives a more stable, more densely packed and better-oriented recognition layer than physical adsorption, and that translates directly into sensitivity.

The resulting sensor detected tRNA-derived fragments with a 0.4 nM limit of detection, achieved on a platform whose materials cost is low enough to be consistent with disposable point-of-care use.

Why the approach matters

The interesting engineering here sits at the interface rather than in the electronics. Both projects came down to controlling surface chemistry precisely enough that an electrochemical signal means what you claim it means. That is a materials characterization problem as much as a biosensing one, and the same surface analysis methods I use in thin-film work — establishing what functional groups are present, in what density, and whether a treatment actually modified the surface — are what make the biosensor result credible.

Related publications

• W. Shadman, Musa Mannan, et al. “Electrochemical detection of tRNA-derived fragments (tRFs) based on multi-functionalized carbon surface.” Surfaces and Interfaces (under review).
• M. I. Mannan. “In-Vitro Detection of tRNA Fragments (tRFs) Using an Inkjet-Printed Graphene Electrochemical Aptasensor.” M.S. Thesis, Texas State University, 2023.