Contributing Editor, MEMS Investor Journal
Conventional immunoassay technologies such as enzyme-linked immunosorbent assay (ELISA) and western blot for life sciences and diagnostic applications are time consuming, requiring multiple manual steps in order to achieve assay results. To address this, BioScale, Inc. (Cambridge, Mass.) has integrated sample preparation and microparticle techniques with non-optical MEMS based detection and quantification technology.
Based on the company’s acoustic membrane microparticle platform, only a few basic steps are needed for lab technicians to run an assay, and multiple assays can be run at the same time. BioScale is marketing its products in bioanalytic and bioprocess markets – both areas that the company says require better analytical tools that work well in complex samples.
“A key element of the technology is an 8-sensor MEMS chip with a biological capture surface integrated into a disposable cartridge,” says Mark Lundstrom, BioScale’s CEO. “A biological assay is performed by adding antibody-coated magnetic microparticles to a sample and then flowing the mixture over the sensors. A magnet is used to draw the microparticles to the sensor surface to allow binding to occur.” Eight sensors and fluidic paths are used because they match with 96-well (8 rows x 12 columns) microtiter plates common in life science research.
Explains Mike Miller, Vice President of Product Development, “The eight sensors are identical and during analysis simultaneously process eight individual samples loaded from the microtiter plate. An entire 96-well plate is processed by sequentially analyzing the 12 columns. The sensors’ surface chemistry supports investigating one or multiple analytes in the same experiment. Sensors are regenerated between samples and in some applications more than one plate can be analyzed by a single cartridge.” He adds that there is a finite cycle for reuse, after which the chip cartridge is discarded.
The five steps in the BioScale platform for picogram-level detection of analytes. Changes in the MEMS sensor resonate frequency are detected and monitored when analytes of interest remain. The universal surface of the sensors provides an open platform for the use of acoustic membrane microparticle technology.
During device operation, assay reagents including magnetic beads are combined with samples being analyzed in the microtiter plate and allowed to incubate. In this step, the magnetic beads coated with one antibody, and a second, tagged antibody bind the sample’s analyte of interest.
Samples are delivered to anti-tag coated MEMS biosensors, each of which serves as a piezoelectric-activated vibrating membrane oscillating at 20 million times a second. Each sensor has a magnet that serves to capture the beads holding the analyte of interest. The magnetic field is then turned off and only the biologically bound microparticles containing the analyte of interest remain on the sensor.
“During this process the vibrating frequency of the MEMS based membrane changes and is detected and monitored by our interface electronics and software,” says Miller. “The software includes algorithms to determine a signal value for each sample analyzed based on the frequency change. As with other biological assay methods, calibrators or standards are included in the microtiter plate to relate the measured signal levels to the amount of analyte in the samples.”
“Sensitivity and reproducibility of this analytical device provides researchers with the option of fast sensitive results, ultra sensitive results or both -- using the same assay,” says Lundstrom. “We show low picogram level detection in a standard assay format and fast ELISA-like results in 20 minutes or less versus hours that typically would be required using ELISA methods in a similar analysis.” He notes that the system shows a dramatic increase in sensitivity and reproducibility with the ability to measure low-concentration of analytes that were not previously detectable.
Copyright 2010 MEMS Investor Journal
Comments