Published January 26, 2021 | Version v1
Journal article Open

Comparative study of autofluorescence in flat and tapered optical fibers towards application in depth-resolved fluorescence lifetime photometry in brain tissue

  • 1. Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti 14, 73010 Arnesano (Lecce), Italy; Dipartimento di Ingegneria dell'Innovazione, Università del Salento, Via per Monteroni, 73100 Lecce, Italy
  • 2. Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti 14, 73010 Arnesano (Lecce), Italy
  • 3. Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Via Barsanti 14, 73010 Arnesano (Lecce), Italy; Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università del Salento, Via per Monteroni, 73100 Lecce, Italy
  • 4. Howard Hughes Medical Institute, Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA

Description

Abstract: As the scientific community seeks efficient optical neural interfaces with sub-cortical structures of the mouse brain, a wide set of technologies and methods is being developed to monitor cellular events through fluorescence signals generated by genetically encoded molecules. Among these technologies, tapered optical fibers (TFs) take advantage of the modal properties of narrowing waveguides to enable both depth-resolved and wide-volume light collection from scattering tissue, with minimized invasiveness with respect to standard flat fiber stubs (FFs). However, light guided in patch cords as well as in FFs and TFs can result in autofluorescence (AF) signal, which can act as a source of time-variable noise and limit their application to probe fluorescence lifetime in vivo. In this work, we compare the AF signal of FFs and TFs, highlighting the influence of the cladding composition on AF generation. We show that the autofluorescence signal generated in TFs has a peculiar coupling pattern with guided modes, and that far-field detection can be exploited to separate functional fluorescence from AF. On these bases, we provide evidence that TFs can be employed to implement depth-resolved fluorescence lifetime photometry, potentially enabling the extraction of a new set of information from deep brain regions, as time-correlating single photon counting starts to be applied in freely-moving animals to monitor the intracellular biochemical state of neurons.

Technical info

M.B., F. Pisano, A.B., B.S., and F. Pisanello acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (#677683). M.D.V. acknowledges funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (#692943). F. Pisanello and M.D.V. acknowledge funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 828972. L.S., M.D.V and B.L.S. are funded by the US National Institutes of Health (U01NS094190). M.P., L.S., F. Pisanello, M.D.V. and B.L.S. are funded by the US National Institutes of Health (1UF1NS108177-01).

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Additional details

Funding

MODEM – Multipoint Optical DEvices for Minimally invasive neural circuits interface 677683
European Commission
BrainBIT – All-optical brain-to-brain behaviour and information transfer 692943
European Commission
NanoBRIGHT – BRInGing nano-pHoTonics into the brain 828972
European Commission