Distinguished Lecture with Eugen Gheorghiu, PhD
“Label-free high-resolution electro-optical mapping using electrically modulated light microscopy”
Eugen Gheorghiu:
International Centre of Biodynamics (ICB), 1B Intrarea Portocalelor, 060101, Bucharest, Romania; University of Bucharest, 91-95 Splaiul Independentei, 050095, Bucharest, Romania egheorghiu@biodyn.ro; www.biodyn.ro
Join us on February 9 at 12:00, where Dr. Gheorghiu will discuss such limitations and developments in EIS-microscopy, including the allowed analysis of nanopatterned surfaces (via quantitative phase and bright field reflectivity, BFR, imaging) and of magnetically tagged bacterial cells (using BFR). Additionally, the results of his new study 2 enabling in situ rapid detection, separation, sensitive quantification, and viability assessment of magnetically tagged microorganisms (bacteria and fungi) will be highlighted.
Lunch will be provided.
RSVP at the bottom of the page!
Abstract:
Electrical Impedance Spectroscopy (EIS) is frequently used for functional characterization of biosystems. It provides an overall quantitative description of the sample’s electrical and structural properties at a certain moment. Since membrane integrity is a marker of cell viability, EIS is instrumental in directly assessing the viability status of biological cells as revealed by their electrical opacity. While an entire cellular population can be addressed at once, single-cell EIS analysis cannot be attained due to the limited spatial resolution of the electrical assays, inherently linked to the electrode size.
A game changer is provided by combining EIS and optical methods e.g., by AC electrically modulated light microscopy assays. These approaches empower EIS measurements with the spatial resolution required by single-cell analysis without the limitations related to electrode size and microelectrode array dimensionality.
Adding AC electrical modulation to quantitative imaging provides label-free, high-resolution images of both optical path and electrical impedance of the sample. These maps relate to the distribution of the refractive index and conductivity, as complementary intrinsic parameters and imaging contrast elements of a (bio)sample. While previously we limited the analysis to the distribution of the phase amplitude at the frequency of the applied AC field1, we now extend the study to map the AC modulated reflectivity, as well. Moreover, we recently demonstrated that cells could be analysed both when adhered to the (transparent) sensing electrode and at any distance from the slide (encapsulated in a hydrogel), within the working distance of the objective.
This novel multimodal approach highlights new capabilities for gauging both electrical and optical hyper-structures of biological (e.g., microbial) cells and their dynamic changes per se or in response to excitation, including exposure to antimicrobial/antitumoral drugs.
Recent developments in EIS-microscopy allowing analysis of nanopatterned surfaces (via quantitative phase and bright field reflectivity, BFR, imaging) and of magnetically tagged bacterial cells (using BFR) will be described and discussed. Additionally, the results of our new study2 enabling in situ rapid detection, separation, sensitive quantification, and viability assessment of magnetically tagged microorganisms (bacteria and fungi) will be highlighted.
Keywords: electrical modulation of the refractive index, electro-optical microscopy, structural and electrical fingerprint
1. Polonschii C., et al., High resolution impedance mapping using electrically-activated quantitative phase imaging, LSA (2021) 10:20 www.nature.com/articles/s41377-020-00461-x
2. David S., et al, In situ detection and viability assessment of target microorganisms, Biosensors Bioelectronics (2023), https://doi.org/10.1016/j.bios.2023.115821