A Label-Free Cell-Based Biosensor Method for Ethanol Quantification Using Temperature-Induced Spontaneous Cell Detachment

Biosensors, vol. 16, pp. 355

Abstract

Rapid, low-cost ethanol quantification is vital for beverage quality control, biofuel production, and pharmaceutical applications, yet current approaches are costly, reagent- or label-dependent, or rely on spectroscopy with substantial sample preparation. We introduce a purely cell-based, label-free biosensor that exploits temperature-gradient-induced spontaneous detachment of Saccharomyces cerevisiae from a chip surface. The readout is the detachment half-time, td50, derived from time-resolved changes in interfacial thermal resistance, Rth, at the solid–liquid interface. Cells were pre-exposed to ethanol (0–70% v/v) and the detachment kinetics monitored using the heat transfer method (HTM). Under these conditions, cells display a pronounced non-monotonic td50 response with a peak around 20% v/v ethanol. Overall, the td50 rises from ~45 min (0% ethanol) to ≳10 h (20%) and then decreases, with no detachment at 60% and beyond. Critically, cell quality gates the detachment window. Fresh yeast responds up to ~50%, whereas aged yeast ceases to detach above ~8%, demonstrating a dual-function assay. Complementary measurements show that ethanol decreases surface tension monotonically, as expected, while optical/SEM imaging reveals aggregation above the detachment window. Requiring only a heater and a temperature probe, this platform offers a compact and low-cost strategy for ethanol sensing. Its applicability in a complex matrix is further demonstrated using whiskey diluted to selected alcohol concentrations, which produced responses consistent with the ethanol calibration trend. Potentially, it also offers a thermal assay for real-time monitoring of microbial cell quality across biotechnology and bioengineering applications. Considering ethanol as a proxy for drugs, the strategy may also support label-free drug screening on cells. At a fundamental level, the non-monotonic effect of ethanol, and especially the sharp maximum at 20%, remains unresolved and invites further studies.

Authors 7

1. Derick Yongabi corresponding

   KU Leuven

   Affiliation as printed

   Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium

2. Alex Krane

   KU Leuven

   Affiliation as printed

   Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium

3. Sofia Xavier Bustia

   Universidade de São Paulo

   Affiliation as printed

   Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Prof. Lineu Prestes, 580, São Paulo CEP 05508-000, SP, Brazil

4. Jonas Gruber

   Universidade de São Paulo

   Affiliation as printed

   Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo CEP 05508-000, SP, Brazil

5. Michael Josef Schöning Aachen Institute of Nano- and Biotechnologies (INB)

   FH Aachen

   Affiliation as printed

   Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Heinrich-Mußmann-Straße1, D-52428 Jülich, Germany

6. Frank Delvigne

   University of Liège · Gembloux Agro-Bio Tech

   Affiliation as printed

   Microbial Processes and Interactions (MiPI), Terra Research and Teaching Centre, Gembloux Agro-Bio Tech, University of Liège, Av. De la Faculté D’Agronomie 41/13, 5030 Gembloux, Belgium

7. Patrick Hermann Wagner

   KU Leuven

   Affiliation as printed

   Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium