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Direct measurement of non-thermal microwave effects on bacterial growth and redox dynamics using a novel high-throughput waveguide applicator

Miles, A., Porch, A. ORCID: https://orcid.org/0000-0001-5293-8883, Choi, H. ORCID: https://orcid.org/0000-0003-1108-293X, Cripps, S. ORCID: https://orcid.org/0000-0002-2258-951X, Brown, H. and Williams, C. F. ORCID: https://orcid.org/0000-0001-8619-2581 2025. Direct measurement of non-thermal microwave effects on bacterial growth and redox dynamics using a novel high-throughput waveguide applicator. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 383 (2297) , 20240073. 10.1098/rsta.2024.0073

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Abstract

A high-throughput microwave applicator has been designed and characterized to investigate microwave interactions with biological systems. When operated in the TE10 mode, this rectangular waveguide enabled simultaneous exposure of 96 biological samples to a quantifiable electric field (E field) at 2.45 GHz. Optimized electric probe transitions efficiently couple power (up to 50 W) into and out of the waveguide, achieving a voltage transmission coefficient (S21) near unity (0 dB) and a voltage reflection coefficient (S11) below 0.01 ( less than −20 dB). The growth dynamics of Staphylococcus aureus bacteria were analysed after non-thermal, microsecond-pulsed microwave exposure at 25 W r.m.s. of microwave power for 24 h. Post-exposure, S. aureus exhibited significantly higher optical density measurements and growth rates than thermal controls. Fluorescent probes directed towards key redox indicators revealed that microwave exposure altered the cellular redox state. This study provides new insights into the non-thermal effects of pulsed 2.45 GHz microwaves on S. aureus growth dynamics and characterizes a novel high-throughput platform for further exploration of fundamental microwave effects on biological systems.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Schools > Engineering
Schools > Biosciences
Publisher: The Royal Society
ISSN: 1364-503X
Date of First Compliant Deposit: 21 January 2025
Date of Acceptance: 17 January 2025
Last Modified: 22 May 2025 10:15
URI: https://orca.cardiff.ac.uk/id/eprint/175462

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