Bioelectronics (IBI-3)

Various microorganisms have developed light sensitive protein channels and pumps in order to respond to their environment. Among these channelrhodopsins are Channelrhodopsin 2 (ChR2), from C. reinhardtii, and GtACR1 from G. theta. ChR2 opens in response to blue light and conducts cations, while GtACR1 responds to green light and conducts anions, thereby suppressing cell activity. We are using a mutated version of channelrhodopsin (ChR2opt) to stimulate cardiomyocyte-like cells and neurons with light.

Photo-responsive ion channels can be selectively expressed in cortical neurons using recombinant adeno-associated virus particles to deliver genetic material. Cell activity can then be measured using our chip based technology for days without harming the cell while the activity of the network is manipulated with light. Alternatively, activity can be recorded by concurrent calcium imaging using red fluorescent indicators. We've further shown the advantages in terms of spatial resolution of optogenetic stimulation over extracellular electrical stimulation. We can elicit action potentials with 3 micrometer diameter targeted light pulses. This light based stimulation compliments the high temporal accuracy of extracellular recordings, making optogenetics and on-chip recordings complimentary techniques.

Diverse genetically engineered ‘optogenetic tools’ are used to activate or inactivate neurons by light stimulation of encoded proteins. Our three laser-illuminating system allows precise targeting of cultured neurons in both temporal and spatial scales. We are using our system to directly compare opening of optogenetic channels with visible light to opening channels with infrared light that has been converted to visible light by in-house produced upconversion nanoparticles (UCNPs). Since infrared light penetrates deep into tissues, UCNPs injected into the body, patterned in a cell culture, or incorporated into implants will allow optogenetic stimulation without implanted light sources.

To investigate information processing in neural circuits, which are represented by changes of network firing patterns, we presented preliminary tests of manipulating network dynamics by optical stimulation of neurons genetically modified with ChR2opt, and network changes persisting for 10 minutes after a single mechanical stimulation of the soma.

PUBLICATIONS:

Wang, J. (First author) ; Platz-Baudin, E. ; Noetzel-Reiss, E. ; Offenhäusser, A. ; Maybeck, V. (Corresponding author)
Expressing Optogenetic Actuators Fused to N-terminal Mucin Motifs Delivers Targets to Specific Subcellular Compartments in Polarized Cells
Advanced biology 8(3), 2300428 (2024) [10.1002/adbi.202300428]

Kempmann, A., Gensch, T., Offenhäusser, A., Tihaa, I., Maybeck, V., Balfanz, S., & Baumann, A. (2022). The Functional Characterization of GCaMP3.0 Variants Specifically Targeted to Subcellular Domains. International Journal of Molecular Sciences, 23(12). https://doi.org/10.3390/ijms23126593 https://pubmed.ncbi.nlm.nih.gov/35743038/

An evaluation of extracellular MEA versus optogenetic stimulation of cortical neurons
Maybeck et al., Biomed. Phys. Eng. Express, 2016, 2, 055017.

High-efficiency transduction and specific expression of ChR2opt for optogenetic manipulation of primary cortical neurons mediated by recombinant adeno-associated viruses
Jin et al., J. Biotechnol., 2016, 233, 171–180.

Optogenetic Control of Neuronal Network Activity on MEA
Li et al., Front. Neurosci. Conference Abstract: MEA Meeting 2016 | 10th International Meeting on Substrate-Integrated Electrode Arrays.

Recombinant Adeno-associated virus (rAAV)-mediated transduction and optogenetic manipulation of cortical neurons in vitro
Lange et al., Proc. SPIE 8928, Optical Techniques in Neurosurgery, Neurophotonics, and Optogenetics, 89282S, vol. 8928, p. 89282S.

Light induced stimulation and delay of cardiac activity
Hofmann et al., Lab Chip, 2010, 10, 2588–96.