TY  - JOUR
AB  - Understanding the functional connectivity and behavior of 3D cell cultures and organoids requires monitoring electrical activity across multiple planes. However, traditional planar microelectrode arrays (MEAs) are limited to surface recordings and struggle to capture signals from deeper layers. Additionally, current fabrication methods face challenges such as prolonged production times and limited design flexibility, which hinder the development of high-precision 3D electrode arrays and affect the quality of cell-electrode coupling. To overcome these obstacles, we introduce a new approach that integrates inkjet printing with focused ion beam (FIB) milling and electrodeposition, resulting in highly customizable 3D MEAs. The FIB milling enables the creation of precise electrode openings at predetermined locations, which is essential for selective recordings within the tissue. The MEAs, fabricated on glass substrates, incorporate high-aspect-ratio (up to 44:1) electrode structures with heights up to 1 mm, a pitch of 500 μm, and electrode openings of 3 and 6 μm, providing the necessary resolution for targeted measurements. Impedance and noise characteristics (down to a root-mean-square of (RMS) noise of 0.2 pA) for amperometric measurements were assessed in dependence on the electrode size. We demonstrate the effectiveness of these 3D MEAs by recording electrophysiological activity from hiPSC-derived cortical organoids (age: 24 month) both in situ and after 10 days of cultivation of the organoid directly on the MEA. This approach facilitates in vitro studies of neural activity in organoids and holds promise for high-throughput, selective amperometric analyses in normal and pathologically altered conditions.
AU  - Kopic, I.*
AU  - Peng, H.*
AU  - Schmidt, S.
AU  - Berezin, O.*
AU  - Wang, S.*
AU  - Westmeyer, G.G.
AU  - Wolfrum, B.*
C1  - 75382
C2  - 58365
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 6426–6435
TI  - Inkjet-printed 3D sensor arrays with FIB-induced electrode refinement for low-noise amperometric recordings in hiPSC-derived brain organoids.
JO  - ACS sens.
VL  - 10
IS  - 9
PB  - Amer Chemical Soc
PY  - 2025
SN  - 2379-3694
ER  - 

TY  - JOUR
AB  - The interaction of small molecules or proteins with RNA or DNA often involves changes in the nucleic acid (NA) folding and structure. A biophysical characterization of these processes helps us to understand the underlying molecular mechanisms. Here, we propose kinFRET (kinetics Förster resonance energy transfer), a real-time ensemble FRET methodology to measure binding and folding kinetics. With kinFRET, the kinetics of conformational changes of NAs (DNA or RNA) upon analyte binding can be directly followed via a FRET signal using a chip-based biosensor. We demonstrate the utility of this approach with two representative examples. First, we monitored the conformational changes of different formats of an aptamer (MN19) upon interaction with small-molecule analytes. Second, we characterized the binding kinetics of RNA recognition by tandem K homology (KH) domains of the human insulin-like growth factor II mRNA-binding protein 3 (IMP3), which reveals distinct kinetic contributions of the two KH domains. Our data demonstrate that kinFRET is well suited to study the kinetics and conformational changes of NA-analyte interactions.
AU  - Higuera-Rodriguez, R.A.*
AU  - De Pascali, M.C.*
AU  - Aziz, M.
AU  - Sattler, M.
AU  - Rant, U.*
AU  - Kaiser, W.J.*
C1  - 68939
C2  - 53781
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 4597-4606
TI  - Kinetic FRET assay to measure binding-induced conformational changes of nucleic acids.
JO  - ACS sens.
VL  - 8
IS  - 12
PB  - Amer Chemical Soc
PY  - 2023
SN  - 2379-3694
ER  - 

TY  - JOUR
AB  - Photoacoustic (optoacoustic) imaging can extract molecular information with deeper tissue penetration than possible by fluorescence microscopy techniques. However, there is currently still a lack of robust genetically controlled contrast agents and molecular sensors that can dynamically detect biological analytes of interest with photoacoustics. In a biomimetic approach, we took inspiration from cuttlefish who can change their color by relocalizing pigment-filled organelles in so-called chromatophore cells under neurohumoral control. Analogously, we tested the use of melanophore cells from Xenopus laevis, containing compartments (melanosomes) filled with strongly absorbing melanin, as whole-cell sensors for optoacoustic imaging. Our results show that pigment relocalization in these cells, which is dependent on binding of a ligand of interest to a specific G protein-coupled receptor (GPCR), can be monitored in vitro and in vivo using photoacoustic mesoscopy. In addition to changes in the photoacoustic signal amplitudes, we could furthermore detect the melanosome aggregation process by a change in the frequency content of the photoacoustic signals. Using bioinspired engineering, we thus introduce a photoacoustic pigment relocalization sensor (PaPiReS) for molecular photoacoustic imaging of GPCR-mediated signaling molecules.
AU  - Lauri, A.
AU  - Soliman, D.
AU  - Omar, M.
AU  - Stelzl, A.
AU  - Ntziachristos, V.
AU  - Westmeyer, G.G.
C1  - 55304
C2  - 46256
CY  - 1155 16th St, Nw, Washington, Dc 20036 Usa
SP  - 603-612
TI  - Whole-cell photoacoustic sensor based on pigment relocalization.
JO  - ACS sens.
VL  - 4
IS  - 3
PB  - Amer Chemical Soc
PY  - 2019
SN  - 2379-3694
ER  -