Sensitive and rapid immunoassay for parathyroid hormone using magnetic particle labels and magnetic actuation

A rapid method for the sensitive detection of proteins using actuated magnetic particle labels, which are measured with a giant magneto-resistive (GMR) biosensor, is described. The technique involves a 1-step sandwich immunoassay with no fluid replacement steps. The various assay binding reactions as well as the bound/free separation are entirely controlled by magnetic forces induced by electromagnets above and below the sensor chip. During the assay, particles conjugated with tracer antibodies are actuated through the sample for target capture, and rapidly brought to the sensor surface where they bind to immobilized capture antibodies. Weakly or unbound labels are removed with a magnetic force oriented away from the GMR sensor surface. For the measurement of parathyroid hormone (PTH), a detection limit in the 10 pM range is obtained with a total assay time of 15 min when 300 nm particles are used. The same sensitivity can be achieved in 5 min when 500 nm particles are used. If 500 nm particles are employed in a 15-minute assay, then 0.8 pM of PTH is detectable. The low sample volume, high analytical performance and high speed of the test coupled with the compact GMR biosensor make the system especially suitable for sensitive testing outside of laboratory environments

Sensitive and rapid immunoassay for parathyroid hormone using magnetic particle labels and magnetic actuation

A rapid method for the sensitive detection of proteins using actuated magnetic particle labels, which are measured with a giant magneto-resistive (GMR) biosensor, is described. The technique involves a 1-step sandwich immunoassay with no fluid replacement steps. The various assay binding reactions as well as the bound/free separation are entirely controlled by magnetic forces induced by electromagnets above and below the sensor chip. During the assay, particles conjugated with tracer antibodies are actuated through the sample for target capture, and rapidly brought to the sensor surface where they bind to immobilized capture antibodies. Weakly or unbound labels are removed with a magnetic force oriented away from the GMR sensor surface. For the measurement of parathyroid hormone (PTH), a detection limit in the 10 pM range is obtained with a total assay time of 15 min when 300 nm particles are used. The same sensitivity can be achieved in 5 min when 500 nm particles are used. If 500 nm particles are employed in a 15-minute assay, then 0.8 pM of PTH is detectable. The low sample volume, high analytical performance and high speed of the test coupled with the compact GMR biosensor make the system especially suitable for sensitive testing outside of laboratory environments

Packaging of silicon sensors for microfluidic bio-analytical applications

A new industrial concept is presented for packaging biosensor chips in disposable microfluidic cartridges to enable medical diagnostic applications. The inorganic electronic substrates, such as silicon or glass, are integrated in a polymer package which provides the electrical and fluidic interconnections to the world and provides mechanical strength and protection for out-of-lab use. The demonstrated prototype consists of a molded interconnection device (MID), a silicon-based giant magneto-resistive (GMR) biosensor chip, a flex and a polymer fluidic part with integrated tubing. The various processes are compatible with mass manufacturing and run at a high yield. The devices show a reliable electrical interconnection between the sensor chip and readout electronics during extended wet operation. Sandwich immunoassays were carried out in the cartridges with surface functionalized sensor chips. Biological response curves were determined for different concentrations of parathyroid hormone (PTH) on the packaged biosensor, which demonstrates the functionality and biocompatibility of the devices. The new packaging concept provides a platform for easy further integration of electrical and fluidic functions, as for instance required for integrated molecular diagnostic devices in cost-effective mass manufacturing

Packaging of silicon sensors for microfluidic bio-analytical applications

A new industrial concept is presented for packaging biosensor chips in disposable microfluidic cartridges to enable medical diagnostic applications. The inorganic electronic substrates, such as silicon or glass, are integrated in a polymer package which provides the electrical and fluidic interconnections to the world and provides mechanical strength and protection for out-of-lab use. The demonstrated prototype consists of a molded interconnection device (MID), a silicon-based giant magneto-resistive (GMR) biosensor chip, a flex and a polymer fluidic part with integrated tubing. The various processes are compatible with mass manufacturing and run at a high yield. The devices show a reliable electrical interconnection between the sensor chip and readout electronics during extended wet operation. Sandwich immunoassays were carried out in the cartridges with surface functionalized sensor chips. Biological response curves were determined for different concentrations of parathyroid hormone (PTH) on the packaged biosensor, which demonstrates the functionality and biocompatibility of the devices. The new packaging concept provides a platform for easy further integration of electrical and fluidic functions, as for instance required for integrated molecular diagnostic devices in cost-effective mass manufacturing

Rapid integrated biosensor for multiplexed immunoassays based on actuated magnetic nanoparticles

The realization of biomolecular detection assays for diagnostic purposes is technologically very challenging because such tests demand full integration for ease of use and need to deliver a high analytical performance with cost-effective use of materials. In this article an optomagnetic immunoassay technology is described based on nanoparticles that are magnetically actuated and optically detected in a stationary sample fluid. The dynamic control of nanoparticles by magnetic fields impacts the key immunoassay process steps, giving unprecedented speed, assay control and seamless integration of the total test. The optical detection yields sensitive and multiplexed assays in a low-cost disposable cartridge. We demonstrate that the optomagnetic technology enables high-sensitivity one-step assays in blood serum/plasma and whole saliva. Drugs of abuse are detected at sub-nanogram per millilitre levels in a total assay time of 1 min, and the cardiac marker troponin I is detected at sub-picomole per litre concentrations in a few minutes. The optomagnetic technology is fundamentally suited for high-performance integrated testing and is expected to open a new paradigm in biosensing

Rapid integrated biosensor for multiplexed immunoassays based on actuated magnetic nanoparticles

The realization of biomolecular detection assays for diagnostic purposes is technologically very challenging because such tests demand full integration for ease of use and need to deliver a high analytical performance with cost-effective use of materials. In this article an optomagnetic immunoassay technology is described based on nanoparticles that are magnetically actuated and optically detected in a stationary sample fluid. The dynamic control of nanoparticles by magnetic fields impacts the key immunoassay process steps, giving unprecedented speed, assay control and seamless integration of the total test. The optical detection yields sensitive and multiplexed assays in a low-cost disposable cartridge. We demonstrate that the optomagnetic technology enables high-sensitivity one-step assays in blood serum/plasma and whole saliva. Drugs of abuse are detected at sub-nanogram per millilitre levels in a total assay time of 1 min, and the cardiac marker troponin I is detected at sub-picomole per litre concentrations in a few minutes. The optomagnetic technology is fundamentally suited for high-performance integrated testing and is expected to open a new paradigm in biosensing

Frequency-tunability of a collapse-mode CMUT: from modelling to pre-clinical imaging

In intracardiac echocardiography (ICE) it might be beneficial to provide ultrasound images acquired at multiple frequencies to provide high resolution and high penetration combined in a single ICE catheter. The objective of the presented work is to investigate the feasibility of a frequency-tunable imaging with a capacitive micromachined ultrasonic transducer (CMUT) operated in a collapse mode. We have developed a semi-analytic model of collapse-mode CMUT [1]. The modelled collapse-voltage is 59 V. Simulated impulse response predicts center frequency of 12.9 MHz and 16.6 MHz at a bias voltage of 100 V and 160 V, respectively. Experimental validation with a manufactured CMUT prototype [2] shows that the dynamic response and frequency-tunability are modelled with a satisfactory accuracy as shown in Fig. 1. Further experimental studies show that the center frequency of a collapse-mode CMUT can be controlled between 8 MHz and 15 MHz, if the lower bias voltage range is extended and the driving pulse is optimized. Mechanically-scanned B-mode imaging is performed on a phantom at 8 MHz, 11 MHz, and 15 MHz as a first proof of principle of a frequency-tunable imaging with a collapse-mode CMUT [4]. A 2x2 mm2 32-element phased-array CMUT is integrated with front-end electronics in a rigid probe prototype and connected to Verasonics system (Kirkland, WA, USA) for 2-D real-time imaging and data acquisition [4]. CMUT imaging performance is quantified in terms of resolution and penetration depth at a range of bias voltages, driving pulse frequencies, and number of pulse cycles. Based on this characterization settings for high-penetration, generic, and high-resolution imaging modes are identified. The first 2-D imaging results are shown. The developed probe prototype is tested ex vivo in a passive heart platform [5]. Images of an aortic valve acquired in high penetration (6 MHz), generic (12 MHz), and high-resolution (18 MHz) mode combine satisfying image quality and penetration depth between 2.5 cm and 10 cm as shown in Fig. 2. Next, the CMUT probe prototype is further miniaturized into a 12-Fr steerable, forward-looking ICE catheter. The ICE catheter prototype is tested in vivo using a porcine animal model [5]. Images of an aortic valve are acquired in the three imaging modes with the ICE catheter placed in an ascending aorta at multiple depths. It was found that the combination of the forward-looking design and frequency tuning capability allows visualizing intracardiac structures of various sizes at different distances relative to the catheter tip, providing both wide overviews and detailed close-ups. References [1] Martin Pekař, Stephan H. M. van Nispen, Rob H. B. Fey, Sergei Shulepov, Nenad Mihajlović, Henk Nijmeijer, Sensors and Actuators A: Physical (in review). [2] Dirksen, P. and Lugt, A. van der (2009), Production of Pre-Collapsed Capacitive Micro-Machined Ultrasonic Transducers and Applications Thereof, Patent WO 2009037655 (A2), March 2009. [3] Martin Pekař, Wendy U. Dittmer, Nenad Mihajlović, Gijs van Soest, Nico de Jong, Frequency Tuning of Collapse-Mode Capacitive Micromachined Ultrasonic Transducer, Ultrasonics, vol. 74, p. 144-152, 2017. [4] Pekař, M., Mihajlović, N., Belt, H., Kolen, A. F., Rens, J. van, Budzelaar, F., Jacobs, B., Bosch, J. G., Vos, H. J., Steen, A. F. W. van der and Rem-Bronneberg, D. (2016) ‘Frequency-Agility of Collapse-Mode 1-D CMUT Array’, in Proceedings - IEEE Ultrasonics Symposium. Tours: IEEE. [5] Martin Pekař, Alexander F. Kolen, Harm Belt, Frank van Heesch, Nenad Mihajlović, Imo E. Hoefer, Tamas Szili-Török, Hendrik J. Vos, Johan G. Bosch, Gijs van Soest, Antonius F. W. van der Steen. Preclinical Testing of Frequency-Tunable Capacitive Micromachined Ultrasonic Transducer Probe Prototypes, Ultrasound in Medicine and Biology (in press)