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A lab-on-a-chip utilizing microwaves for bacterial spore disruption and detection
Umeå University, Faculty of Science and Technology, Department of Physics. Faculty of Electrical Engineering, K. N. Toosi University of Technology, Tehran, Iran.ORCID iD: 0000-0002-4843-5164
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-1303-0327
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0000-0002-0168-0197
Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Ås, Norway.ORCID iD: 0000-0001-5373-0590
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2023 (English)In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 231, article id 115284Article in journal (Refereed) Published
Abstract [en]

Bacterial spores are problematic in agriculture, the food industry, and healthcare, with the fallout costs from spore-related contamination being very high. Spores are difficult to detect since they are resistant to many of the bacterial disruption techniques used to bring out the biomarkers necessary for detection. Because of this, effective and practical spore disruption methods are desirable. In this study, we demonstrate the efficiency of a compact microfluidic lab-on-chip built around a coplanar waveguide (CPW) operating at 2.45 GHz. We show that the CPW generates an electric field hotspot of ∼10 kV/m, comparable to that of a commercial microwave oven, while using only 1.2 W of input power and thus resulting in negligible sample heating. Spores passing through the microfluidic channel are disrupted by the electric field and release calcium dipicolic acid (CaDPA), a biomarker molecule present alongside DNA in the spore core. We show that it is possible to detect this disruption in a bulk spore suspension using fluorescence spectroscopy. We then use laser tweezers Raman spectroscopy (LTRS) to show the loss of CaDPA on an individual spore level and that the loss increases with irradiation power. Only 22% of the spores contain CaDPA after exposure to 1.2 W input power, compared to 71% of the untreated control spores. Additionally, spores exposed to microwaves appear visibly disrupted when imaged using scanning electron microscopy (SEM). Overall, this study shows the advantages of using a CPW for disrupting spores for biomarker release and detection.

Place, publisher, year, edition, pages
Elsevier, 2023. Vol. 231, article id 115284
Keywords [en]
Raman spectroscopy, Fluorescence sep CaDPA, Waveguide, Biomarker, Bacillus
National Category
Other Physics Topics Other Electrical Engineering, Electronic Engineering, Information Engineering Biophysics
Identifiers
URN: urn:nbn:se:umu:diva-206257DOI: 10.1016/j.bios.2023.115284ISI: 000980707400001PubMedID: 37031508Scopus ID: 2-s2.0-85151660389OAI: oai:DiVA.org:umu-206257DiVA, id: diva2:1748097
Part of project
Biophysical and Physicochemical Fingerprinting of Single Bacterial Spores, Swedish Research Council
Funder
Swedish Research Council, 2019-04016Swedish Foundation for Strategic ResearchThe Kempe Foundations, JCK-1916.2Swedish Armed Forces, 470-A400821Available from: 2023-04-01 Created: 2023-04-01 Last updated: 2025-09-30Bibliographically approved
In thesis
1. Spotlight the killer: detecting harmful chemical and biological agents using optical spectroscopy
Open this publication in new window or tab >>Spotlight the killer: detecting harmful chemical and biological agents using optical spectroscopy
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Lyset på mördaren : detektion av skadliga kemiska och biologiska ämnen med hjälp av optisk spektroskopi
Abstract [en]

Harmful chemical and biological agents are a significant threat to health and prosperity worldwide. Recent years have seen an increase in wars and conflicts around the globe, raising concerns about the potential deployment of chemical and biological warfare agents. On a less speculative level, harmful chemicals such as narcotic substances cause immense humanitarian and economic damage through overdoses and associated healthcare costs, while microbes such as pathogenic bacteria and parasites cause hospital-acquired infections and food spoilage at a cost of approximately 1 trillion euros every year. To combat the threat of these harmful agents, we must thus develop rapid and effective detection and diagnostic methods for harmful agents, allowing us to effectively deploy specific treatments and preventative measures.

Classically, while there exist numerous methods for the detection of both harmful chemical and biological agents, they often come with limitations that inhibit their effectiveness. These inhibitions often take the form of bulky equipment that is difficult to apply in the field or time-consuming preparation and measurement processes.

In this thesis we will explore an alternative category of assays for detecting and characterizing harmful materials – optical spectroscopy. Optical spectroscopy is a category of material characterization methods that use light to probe a material. While probing the material, we receive a signal characteristic of the molecules, chemical, and biological structure of our material. These optical spectroscopic methods, such as Raman spectroscopy and fluorescence spectroscopy, can be used to characterize a material within the span of minutes or even seconds, making them ideal for detection applications. Furthermore, they can often be made portable or even handheld, making them a great tool for initial field indication of harmful materials, ahead of thorough lab analysis.

I sincerely hope the studies presented herein can serve as a stepping stone to future technologies and detection assays, capable of saving both money and lives. 

Place, publisher, year, edition, pages
Umeå: Umeå University, 2025. p. 72
Keywords
Sensing, Raman spectroscopy, SERS, Fluorescence spectroscopy, CWA, nerve agents, bacterial spores, Cryptosporidium
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-244830 (URN)978-91-8070-780-0 (ISBN)978-91-8070-779-4 (ISBN)
Public defence
2025-10-24, Aula Anatomica, Biologihuset, 907 36, Umeå, Umeå, 13:00 (English)
Opponent
Supervisors
Note

This work was done in collaboration with, and with support from, the Swedish Defece Research Agency (FOI).

Available from: 2025-10-03 Created: 2025-09-30 Last updated: 2025-10-22Bibliographically approved

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Valijam, ShayanNilsson, DanielÖberg, RasmusAndersson, MagnusMalyshev, Dmitry

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Valijam, ShayanNilsson, DanielÖberg, RasmusAlbertsdóttir Jonsmoen, Unni LisePorch, AdrianAndersson, MagnusMalyshev, Dmitry
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