biostudies-literatureZgierski-Johnston CMEuropean Research CouncilDeutsche ForschungsgemeinschaftEuropean Commission51-61https://www.ebi.ac.uk/biostudies/studies/S-EPMC7322525biostudies-literatureUnknown154Optogenetics enables cell-type specific monitoring and actuation via light-activated proteins. In cardiac research, expressing light-activated depolarising ion channels in cardiomyocytes allows optical pacing and defibrillation. Previous studies largely relied on epicardial illumination. Light penetration through the myocardium is however problematic when moving to larger animals and humans. To overcome this limitation, we assessed the utility of an implantable multi light-emitting diode (LED) optical probe (IMLOP) for intramural pacing of mouse hearts expressing cardiac-specific channelrhodopsin-2 (ChR2). Here we demonstrated that IMLOP insertion needs approximately 20 mN of force, limiting possible damage from excessive loads applied during implantation. Histological sections confirmed tProgress in biophysics and molecular biologyCardiac pacing using transmural multi-LED probes in channelrhodopsin-expressing mouse hearts.PMC7322525323099Fernandez MCKohl PRuther PRog-Zielinska EABarz FAyub SPaul OZgierski-Johnston CMfalseCardiac pacing using transmural multi-LED probes in channelrhodopsin-expressing mouse hearts.Optogenetics enables cell-type specific monitoring and actuation via light-activated proteins. In cardiac research, expressing light-activated depolarising ion channels in cardiomyocytes allows optical pacing and defibrillation. Previous studies largely relied on epicardial illumination. Light penetration through the myocardium is however problematic when moving to larger animals and humans. To overcome this limitation, we assessed the utility of an implantable multi light-emitting diode (LED) optical probe (IMLOP) for intramural pacing of mouse hearts expressing cardiac-specific channelrhodopsin-2 (ChR2). Here we demonstrated that IMLOP insertion needs approximately 20 mN of force, limiting possible damage from excessive loads applied during implantation. Histological sections confirmed t2020-01-01T00:00:00Z2020 Aug2025-04-19T00:59:56.639Z2025-04-07T11:56:30.643ZS-EPMC73225253173897910.1016/j.pbiomolbio.2019.11.004