Integration of Multiplexed Microfluidic Electrokinetic Concentrators with a Morpholino Microarray via Reversible Surface Bonding for Enhanced DNA Hybridization (original) (raw)
Related papers
Lab-on-a-chip (LOC) devices for electrochemical analysis of DNA hybridization events offer a technology for real-time and label-free assessment of biomarkers at the point-of-care. Here, we present a microfluidic LOC, with 3 3 arrayed electrochemical sensors for the analysis of DNA hybridization events. A new dual layer microfluidic valved manipulation system is integrated providing controlled and automated capabilities for high throughput analysis. This feature improves the repeatability, accuracy, and overall sensing performance (Fig. 1). The electrochemical activity of the fabricated microfluidic device is validated and demonstrated repeatable and reversible Nernstian characteristics. System design required detailed analysis of energy storage and dissipation as our sensing modeling involves diffusion- related electrochemical impedance spectroscopy. The effect of DNA hybridization on the calculated charge transfer resistance and the diffusional resistance components is evaluated. We demonstrate a specific device with an average cross-reactivity value of 27.5%. The device yields semilogarithmic dose response and enables a theoretical detection limit of 1 nM of complementary ssDNA target. This limit is lower than our previously reported non-valved device by 74% due to on-chip valve integration providing controlled and accurate assay capabilities.
A Microfluidic-based Electrochemical Biochip for Label-free DNA Hybridization Analysis
Miniaturization of analytical benchtop procedures into the micro-scale provides significant advantages in regards to reaction time, cost, and integration of pre-processing steps. Utilizing these devices towards the analysis of DNA hybridization events is important because it offers a technology for real time assessment of biomarkers at the point-of-care for various diseases. However, when the device footprint decreases the dominance of various physical phenomena increases. These phenomena influence the fabrication precision and operation reliability of the device. Therefore, there is a great need to accurately fabricate and operate these devices in a reproducible manner in order to improve the overall performance. Here, we describe the protocols and the methods used for the fabrication and the operation of a microfluidic-based electrochemical biochip for accurate analysis of DNA hybridization events. The biochip is composed of two parts: a microfluidic chip with three parallel micro-channels made of polydimethylsiloxane (PDMS), and a 3 x 3 arrayed electrochemical micro-chip. The DNA hybridization events are detected using electrochemical impedance spectroscopy (EIS) analysis. The EIS analysis enables monitoring variations of the properties of the electrochemical system that are dominant at these length scales. With the ability to monitor changes of both charge transfer and diffusional resistance with the biosensor, we demonstrate the selectivity to complementary ssDNA targets, a calculated detection limit of 3.8 nM, and a 13% cross-reactivity with other non-complementary ssDNA following 20 min of incubation. This methodology can improve the performance of miniaturized devices by elucidating on the behavior of diffusion at the micro-scale regime and by enabling the study of DNA hybridization events.
Transverse electrodes for improved DNA hybridization in microchannels
Aiche Journal, 2007
The present study examines the modality, in which localized transverse electric fields can be successfully employed, to augment the rate of DNA hybridization at the capturing probes that are located further downstream relative to the inlet section of a rectangular microchannel. This is in accordance with an enhanced strength of convective transport that can be achieved, on account of increments in the wall zeta potential at the transverse electrode locations. In the present model, the overall convective transport, which is an implicit function of the magnitude and the location of the transverse electrical field being employed, is essentially coupled with the surface kinetics of the bare silica wall and also the kinetics that are involved in the dual mechanisms of DNA hybridization. Parameters that govern the overall transport phenomena, such as the pH of the inlet buffer, the length of the transverse electrodes, and the voltages at which these electrodes are maintained are critically examined, in an effort to obtain an optimized wall pH distribution, which in turn can ensure favorable DNA hybridization rates at the capturing probe locations. Practical constraints associated with the upper limits of the strength of the transverse electrical fields that can be employed are also critically analyzed, so as to ensure that an optimized rate of DNA hybridization can be achieved from the bio-microfluidic arrangement, without incurring any adverse effects associated with the overheating of the DNA molecules leading to their thermal denaturation. © 2007 American Institute of Chemical Engineers AIChE J, 2007
DNA hybridization detection in microfluidic devices can reduce sample volumes, processing times, and can be integrated with other measurements. However, as device footprints decrease and their complexity increase, the signal-to-noise ratio in these systems also decreases and the sensitivity is thereby compromised. Device miniaturization produces distinct properties and phenomena with greater influence at the micro-scale than at the macro-scale. Here, a diffusion-restriction model was applied to a miniaturized biochip nanovolume reactor to accurately characterize DNA hybridization events that contribute to shifts in both charge transfer resistance and diffusional resistance. These effects are shown to play a significant role in electrochemical impedance spectroscopy (EIS) analyses at these length scales. Our highly functional microfluidic biosensor enables the detection of ssDNA targets selectively, with a calculated detection limit of 3.8 nM, and cross-reactivity of 13% following 20 min incubation with the target. This new biosensing approach can be further modeled and tested elucidating diffusion behavior in miniaturized devices and improving the performance of biosensors.