The incorporation of porous silicon (PSi) biosensors into lab-on-a-chip devices present great promise for sensitive and real-time detection of biological targets, offering signiﬁcant advantages in terms of high throughput, small sample volumes, and rapid operation time.
We design novel microfluidic devices and assays that integrate PSi optical biosensor with electrokinetic techniques (in collaboration with Prof. Moran Bercovici, Technion) for highly sensitive label-free detection.
Recently, we demonstrated a highly-sensitive lab-on-a-chip device for DNA and protein detection. The DNA/protein target molecules are focused using an electric ﬁeld within a ﬁnite and conﬁned zone, and this highly concentrated analyte is delivered to an on-chip PSi Fabry–Pérot optical transducer, pre-functionalized with capture probes. Using reﬂective interferometric Fourier transform spectroscopy real-time monitoring, a 1000-fold improvement in the limit of detection (LoD) is demonstrated compared to a standard assay, using the same biosensor.
A measured limit of detection of 1 × 10 −9 M and 7.5 nM is achieved without compromising speciﬁcity for DNA and protein target respectively. To the best of our knowledge, this is the lowest LoD measured to date by any PSi biosensor for DNA.
This is the first time that electrokinetic isotachophoresis (ITP) technique has been applied for DNA and protein focusing on PSi biosensors, as well as the utilization of immobilized aptamers as capture probes in an ITP assay.
In addition, the assay is successfully performed in complex media, such as bacteria lysate samples, while the selectivity of the biosensor is retained.
Schematic illustration of lab-on-a-chip device for optical DNA detection using electrokinetic focusing.
Left: Relative optical signal changes vs time of the aptamer-based biosensor during a typical ITP experiment with E. coli lysate suspension spiked or nonspiked with the target protein.
Right: Averaged relative optical signal changes for ITP biosensing experiments of neat target protein, E. coli lysate spiked with the target protein, and neat E. coli lysate (no target protein), demonstrating great performance and selectivity of the assay in a highly complex media.
The concepts presented herein can be readily applied to other ionic targets, paving way for the development of other highly sensitive chemical and biochemical assays.
- Arshavsky-Graham S., Massad-Ivanir N., Paratore F., Scheper T., Bercovici M., Segal E., On Chip Protein Pre-Concentration for Enhancing the Sensitivity of Porous Silicon Biosensors, ACS Sensors (2017) in press
- Vilenski R., Bercovici M., Segal E., Oxidized Porous Silicon Nanostructures enabling Electrokinetic Transport for Enhanced DNA Detection, Adv. Funct. Mater., 25, 6725–6732 (2015). Featured on the cover page of Advanced Functional Materials – Vol. 25, No. 43
Researchers: Dr. Naama Massad-Ivanir and Sofi Arshavski