Shedding Light on Thermally Induced Optocapacitance at the Organic Biointerface

Abstract

Photothermal perturbation of the cell membrane is typically achieved using transducers that convert light into thermal energy, eventually heating the cell membrane. In turn, this leads to the modulation of the membrane electrical capacitance that is assigned to a geometrical modification of the membrane structure. However, the nature of such a change is not understood. In this work, we employ an all-optical spectroscopic approach, based on the use of fluorescent probes, to monitor the membrane polarity, viscosity, and order directly in living cells under thermal excitation transduced by a photoexcited polymer film. We report two major results. First, we show that rising temperature does not just change the geometry of the membrane but indeed it affects the membrane dielectric characteristics by water penetration. Second, we find an additional effect, which is peculiar for the photoexcited semiconducting polymer film, that contributes to the system perturbation and that we tentatively assigned to the photoinduced polarization of the polymer interface.

Dynamics of Two Distinct Exciton Populations in Methyl-Functionalized Germanane

“…A β-barium borate (BBO) crystal was used to obtain the second harmonic at 400 nm. Spatial resolution was achieved through the incorporation of a homemade microscope in the setup . A long pass dichroic mirror at 530 nm was used to reflect the excitation beam (400 nm) that was then coupled to a 20× objective (Nikon) to focus onto the sample with a spot size of about 6 μm.…”

“…Spatial resolution was achieved through the incorporation of a homemade microscope in the setup. 21 A long pass dichroic mirror at 530 nm was used to reflect the excitation beam (400 nm) that was then coupled to a 20× objective (Nikon) to focus onto the sample with a spot size of about 6 μm. The emission signals were collected in backscattering geometry using a 550 nm long-pass filter and analyzed by a spectrograph (Princeton Instruments Acton SP2300) coupled to a streak camera (Hamamatsu C5680, Japan) equipped with a synchro-scan voltage sweep module.…”

The light-dependent pseudo-capacitive charging of conjugated polymer nanoparticles coupled with the depolarization of the neuronal membrane

“…This phenomenon has been proved to occur in the retina of blind rats and which mediates light restoration. 1,2 The mechanism of photo-transduction that has been proposed in recent papers 1,2,[8][9][10] is here validated by a numerical model. We will show that the ''photochemical'' mechanism, associated with the generation of ROS, can be disregarded under expected retina conditions, and that the electrostatic effect caused by the accumulated charge is responsible for the perturbation of local membrane potential.…”

Optocapacitance: physical basis and its application

“…2C). This will produce a linear increase of C with T given that does not change with T. Nevertheless, it has also recently been proposed that a major contribution for the temperature dependence of the capacitance is given by water penetration in the plasma membrane, which would increase its permittivity (Bondelli et al 2021). This increase in permittivity would make the relation between capacitance and temperature even more nonlinear.…”