Stanislav L. Karsten

Point-of-Care (POC) Devices by Means of Advanced MEMS

Microelectromechanical systems (MEMS) have become an invaluable technology to advance the development of point-of-care (POC) devices for diagnostics and sample analyses. MEMS can transform sophisticated methods into compact and cost-effective microdevices that offer numerous advantages at many levels. Such devices include microchannels, microsensors, etc., that have been applied to various miniaturized POC products. Here we discuss some of the recent advances made in the use of MEMS devices for POC applications.

Nano bioresearch approach by microtechnology.

To progress in basic science and drug development, convenient methodology for detecting specific biological molecules and their interaction in living organism is in high demand. After more than 20 years of increasing research efforts, micro and nanotechnologies are now mature to propose a new class of miniature devices and principles enabling compartmentalized bioassays. Among them, this review proposes various examples that include array of electro-active microwells for highly parallel single cell analysis, cost-effective nanofluidic for DNA separation, parallel enzymatic reaction in 100pL droplet and high-throughput platform for membrane proteins assays. The micro devices are presented with relevant experiments to foresee their future contribution to translational research and drug discovery.

Detection of mutations in the binding domain of tau protein by kinesin-microtubule gliding assay

Tau protein is a biomarker for neurodegeneration. The microtubule (MT)-tau binding affinity varies according to the type of tau isoform and their degree of phosphorylation. We have utilized the difference in binding affinity of tau protein to MT to be evaluated by kinesin motor protein based MT gliding system, in order to detect and differentiate tau isoforms and their mutants. Evaluation parameters are landing rate and density of MTs on a kinesin-coated surface, and their strong correlation enables us to measure only landing rate to distinguish 2N3R and 2N4R (tau isoforms) and mutants. Secondly; we designed and fabricated a microstructure to detect tau-attached MTs, which is composed of a reservoir, parallel channels and collectors. Increase of fluorescent intensity by accumulation of MTs over time was successfully detected at the collector areas. Sensitive and rapid MT-kinesin based detection of tau isoforms (3R/4R) and mutated tau proteins on a microchip format will aid in differential diagnosis and early detection of neurodegenerative condition such as Alzheimer disease (AD).

Developing a MEMS Device with Built-in Microfluidics for Biophysical Single Cell Characterization

This study combines the high-throughput capabilities of microfluidics with the sensitive measurements of microelectromechanical systems (MEMS) technology to perform biophysical characterization of circulating cells for diagnostic purposes. The proposed device includes a built-in microchannel that is probed by two opposing tips performing compression and sensing separately. Mechanical displacement of the compressing tip (up to a maximum of 14 µm) and the sensing tip (with a quality factor of 8.9) are provided by two separate comb-drive actuators, and sensing is performed with a capacitive displacement sensor. The device is designed and developed for simultaneous electrical and mechanical measurements. As the device is capable of exchanging the liquid inside the channel, different solutions were tested consecutively. The performance of the device was evaluated by introducing varying concentrations of glucose (from 0.55 mM (0.1%) to 55.5 mM (10%)) and NaCl (from 0.1 mM to 10 mM) solutions in the microchannel and by monitoring changes in the mechanical and electrical properties. Moreover, we demonstrated biological sample handling by capturing single cancer cells. These results show three important capabilities of the proposed device: mechanical measurements, electrical measurements, and biological sample handling. Combined in one device, these features allow for high-throughput multi-parameter characterization of single cells.

On-chip detection of wild 3R, 4R and mutant 4R tau through kinesin-microtubule binding

We report the successful demonstration of an on-chip tau detection system based on the difference in landing rate and binding density of microtubules (MTs) on a kinesin surface. Tau detection device comprises of a MT reservoir, channel and collector region with an overhang structure. We assayed MTs decorated with three tau types in the kinesin coated device. Since the increase in fluorescence intensity (FI) at the collector regions reflected the type of tau decorated on MTs, thus by measuring the FI we were able to distinguish wild 3R, 4R and P301L mutant tau.