Over the past 15 years, Professor Shiddiky and his team have elucidated many fundamental phenomena in the fields of electroanalytical chemistry, microfluidics, and biosensing. These phenomena have led to the development of several innovative methods and devices that enable accurate and sensitive analysis of a wide range of disease-specific molecules, cells, and pathogens for **medical, agricultural and enviromental** applications. Some of the videos of related technologies are provided below.

Videos

The nature of adsorption of unmodified DNA (e.g., without thiol-binding groups) on bare gold surfaces has long been regarded as ‘‘non-specific’’ and ‘‘difficult to control’’. However, Tarlov et al. reported that this process is finely governed by the composition of DNA bases and strictly follows the following affinity trend: adenine (A)>cytosine (C)>guanine (G)>thymine (T). Since then base dependent DNA adsorption emerged as one the most promising solutions to achieve controlled immobilization of unmodified DNA probes onto gold surfaces. Because this adsorption is highly sequence (base) dependent, it can also be used to distinguish two different DNA sequences (e.g., bisulphite treated sequences representing methylated and unmethylated DNA). We have developed a simple electrochemical method referred to as eMethylsorb for the direct detection of DNA methylation on bisulphite treated samples by simply measuring their relative adsorption levels on a gold electrode.

The video illustrates the basic principle of the eMethylsorb approach. Briefly, DNA samples extracted from cell lines were treated with bisulphite to convert unmethylated cytosines into uracils while methylated cytosines remained unchanged. These samples were then converted to ss-DNA amplicons by an asymmetric PCR step, where methylated cytosines were copied into guanines, and uracils into adenines. The resulting ss-DNA amplicons were directly adsorbed onto a gold electrode. The amount of the adsorbed DNA was quantified by differential pulse voltammetry (DPV) in the presence of the [Fe(CN)6]3-/4- system

eMethylsorb Technology for DNA Methylation Using DNA–Gold Affinity Interactions

This is the surface Plasmon Resonance version of the eMthylsorb technology.

The video illustrates the basic principle of the Methylsorb approach. Briefly, DNA samples extracted from cell lines were treated with bisulphite to convert unmethylated cytosines into uracils while methylated cytosines remained unchanged. These samples were then converted to ss-DNA amplicons by an asymmetric PCR step, where methylated cytosines were copied into guanines, and uracils into adenines. The resulting ss-DNA amplicons were directly adsorbed onto a gold chip. To quantify adsorbed DNA sequences on gold chip, we used a surface Plasmon resonance (SPR) biosensing approach that detects changes in refractive index over time (i.e., changes in the SPR spectral shift) at the sensing surface, which is directly proportional to the relative mass increase associated with target adsorption, thus enabling the real-time and label-free monitoring of targets.

Methylsorb Technology for Detecting DNA Methylation Using Gold-DNA Affinity Interaction

Nanoshearing devices for cancer cell isolation and detection. Nanoshearing is an alternating current (ac) electrohydrodynamics (ac-EHD) induced phenomenon that engenders fluid flow within a few nanometers of an electrode surface. Since the magnitude of the ac-EHD field can be tuned externally (via changing the applied frequency and amplitude of the electric field), it can be readily adjusted to preferentially select strongly (specifically) surface-bound cells over more weakly (non-specifically) surface-bound cells or other species. Using this phenomenon, we have conducted experiments relating to the capture and detection of CTCs on purpose-built microfluidic devices. Our experimental data demonstrate that we are able to selectively isolate and detect low numbers of cells from the large pool of excess non-specific cells present in the blood.