Two-photon excitation of FluoVolt allows improved interrogation of transmural electrophysiological function in the intact mouse heart

Salerno, S., Solvang-Garten, K., Smith, G. L. , Stølen, T. and Kelly, A. (2020) Two-photon excitation of FluoVolt allows improved interrogation of transmural electrophysiological function in the intact mouse heart. Progress in Biophysics and Molecular Biology, 154, pp. 11-20. (doi: 10.1016/j.pbiomolbio.2019.08.007) (PMID:31492464) (PMCID:PMC7322535)

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Background and aims: Two-photon excitation of voltage sensitive dyes (VSDs) can measure rapidly changing electrophysiological signals deep within intact cardiac tissue with improved three-dimensional resolution along with reduced photobleaching and photo-toxicity compared to conventional confocal microscopy. Recently, a category of VSDs has emerged which records membrane potentials by photo-induced electron transfer. FluoVolt is a novel VSD in this category which promises fast response and a 25% fractional change in fluorescence per 100 mV, making it an attractive optical probe for action potential (AP) recordings within intact cardiac tissue. The purpose of this study was to characterize the fluorescent properties of FluoVolt as well as its utility for deep tissue imaging. Methods: Discrete tissue layers throughout the left ventricular wall of isolated perfused murine hearts loaded with FluoVolt or di-4-ANEPPS were sequentially excited with two-photon microscopy. Results: FluoVolt loaded hearts suffered significantly fewer episodes of atrio-ventricular block compared to di-4-ANEPPS loaded hearts, indicating comparatively low toxicity of FluoVolt in the intact heart. APs recorded with FluoVolt were characterized by a lower signal-to-noise ratio and a higher dynamic range compared to APs recorded with di-4-ANEPPS. Although both depolarization and repolarization parameters were similar in APs recorded with either dye, FluoVolt allowed deeper tissue excitation with improved three-dimensional resolution due to reduced out-of-focus fluorescence generation under two-photon excitation. Conclusion: Our results demonstrate several advantages of two-photon excitation of FluoVolt in functional studies in intact heart preparations, including reduced toxicity and improved fluorescent properties.

Item Type:Articles
Additional Information:This work was funded by research grants from the Nasjonal Forskning på Hjerte og Karsykdommer (UNIKARD) and the Norwegian Council for Cardiac Research (NFF). SS was funded by an NFF grant, and AK is funded by a British Heart Foundation project grant (grant number PG/14/66/30927).
Glasgow Author(s) Enlighten ID:Smith, Professor Godfrey and Kelly, Dr Allen
Authors: Salerno, S., Solvang-Garten, K., Smith, G. L., Stølen, T., and Kelly, A.
College/School:College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
Journal Name:Progress in Biophysics and Molecular Biology
ISSN (Online):1873-1732
Published Online:03 September 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Progress in Biophysics and Molecular Biology 154: 11-20
Publisher Policy:Reproduced under a Creative Commons license

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
171442Investigating the mechanisms of low-voltage defibrillation and its application to the human ventricle to facilitate its translation into the clinicGodfrey SmithBritish Heart Foundation (BHF)MRETAZRInstitute of Cardiovascular & Medical Sciences