Mahla Poudineh

Highly Specific Electrochemical Analysis of Cancer Cells using Multi‐Nanoparticle Labeling

Circulating tumor cells (CTCs) can be collected noninvasively and provide a wealth of information about tumor phenotype. For this reason, their specific and sensitive detection is of intense interest. Herein, we report a new, chip-based strategy for the automated analysis of cancer cells. The nanoparticle-based, multi-marker approach exploits the direct electrochemical oxidation of metal nanoparticles (MNPs) to report on the presence of specific surface markers. The electrochemical assay allows simultaneous detection of multiple different biomarkers on the surfaces of cancer cells, enabling discrimination between cancer cells and normal blood cells. Through multiplexing, it further enables differentiation among distinct cancer cell types. We showcase the technology by demonstrating the detection of cancer cells spiked into blood samples.

Tracking the dynamics of circulating tumour cell phenotypes using nanoparticle-mediated magnetic ranking

Profiling the heterogeneous phenotypes of rare circulating tumour cells (CTCs) in whole blood is critical to unravelling the complex and dynamic properties of these potential clinical markers. This task is challenging because these cells are present at parts per billion levels among normal blood cells. Here we report a new nanoparticle-enabled method for CTC characterization, called magnetic ranking cytometry, which profiles CTCs on the basis of their surface expression phenotype. We achieve this using a microfluidic chip that successfully processes whole blood samples. The approach classifies CTCs with single-cell resolution in accordance with their expression of phenotypic surface markers, which is read out using magnetic nanoparticles. We deploy this new technique to reveal the dynamic phenotypes of CTCs in unprocessed blood from mice as a function of tumour growth and aggressiveness. We also test magnetic ranking cytometry using blood samples collected from cancer patients.

Interrogating Circulating Microsomes and Exosomes Using Metal Nanoparticles.

A chip-based approach for electrochemical characterization and detection of microsomes and exosomes based on direct electro-oxidation of metal nanoparticles (MNPs) that specifically recognize surface markers of these vesicles is reported. It is found that exosomes and microsomes derived from prostate cancer cells can be identified by their surface proteins EpCAM and PSMA, suggesting the potential of exosomes and microsomes for use as diagnostic biomarkers.

Fractal circuit sensors enable rapid quantification of biomarkers for donor lung assessment for transplantation

Microchip sensors enable rapid, molecular-level profiling of donated lungs for transplant assessment. Biomarker profiling is being rapidly incorporated in many areas of modern medical practice to improve the precision of clinical decision-making. This potential improvement, however, has not been transferred to the practice of organ assessment and transplantation because previously developed gene-profiling techniques require an extended period of time to perform, making them unsuitable in the time-sensitive organ assessment process. We sought to develop a novel class of chip-based sensors that would enable rapid analysis of tissue levels of preimplantation mRNA markers that correlate with the development of primary graft dysfunction (PGD) in recipients after transplant. Using fractal circuit sensors (FraCS), three-dimensional metal structures with large surface areas, we were able to rapidly (<20 min) and reproducibly quantify small differences in the expression of interleukin-6 (IL-6), IL-10, and ATP11B mRNA in donor lung biopsies. A proof-of-concept study using 52 human donor lungs was performed to develop a model that was used to predict, with excellent sensitivity (74%) and specificity (91%), the incidence of PGD for a donor lung. Thus, the FraCS-based approach delivers a key predictive value test that could be applied to enhance transplant patient outcomes. This work provides an important step toward bringing rapid diagnostic mRNA profiling to clinical application in lung transplantation.

Profiling Functional and Biochemical Phenotypes of Circulating Tumor Cells Using a Two-Dimensional Sorting Device

During cancer progression, tumors shed circulating tumor cells (CTCs) into the bloodstream. CTCs that originate from the same primary tumor can have heterogeneous phenotypes and, while some CTCs possess benign properties, others have high metastatic potential. Deconstructing the heterogeneity of CTCs is challenging and new methods are needed that can sort small numbers of cancer cells according to their phenotypic properties. Here we describe a new microfluidic approach that profiles, along two independent phenotypic axes, the behavior of heterogeneous cell subpopulations. Cancer cells are first profiled according to expression of a surface marker using a nanoparticle-enabled approach. Along the second dimension, these subsets are further separated into subpopulations corresponding to migration profiles generated in response to a chemotactic agent. We deploy this new technique and find a strong correlation between the surface expression and migration potential of CTCs present in blood from mice with xenografted tumors. This system provides an important new means to characterize functional diversity in circulating tumor cells.

Three-dimensional, sharp-tipped electrodes concentrate applied fields to enable direct electrical release of intact biomarkers from cells

Biomarkers such as proteins and nucleic acids released from human cells, bacteria, and viruses offer a wealth of information pertinent to diagnosis and treatment ranging from cancer to infectious disease. The release of these molecules from within cells is a crucial step in biomarker analysis. Here we show that purely electric-field-driven lysis can be achieved, inline, within a microfluidic channel; that it can produce highly efficient lysis and biomarker release; and, further, that it can do so with minimal degradation of the released biomarkers. Central to this new technology is the use of three-dimensional sharp-tipped electrodes (3DSTEs) in lysis, which we prove using experiment and finite-element modeling produce the electric field concentration necessary for efficient cell wall rupture.

Effect of microelectrode structure on electrocatalysis at nucleic acid-modified sensors.

The electrochemical detection of nucleic acids using an electrocatalytic reporter system and nanostructured microelectrodes is a powerful approach to ultrasensitive biosensing. In this report we systematically study for the first time the behavior of an electrocatalytic reporter system at nucleic acid-modified electrodes with varying structures and sizes. [Ru(NH3)6](3+) is used as a primary electron acceptor that is electrostatically attracted to nucleic acid-modified electrodes, and [Fe(CN)6](3-) is introduced into the redox system as a secondary electron acceptor to regenerate Ru(3+) after electrochemical reduction. We found that the electrode structure has strong impact on mass transport and electron-transfer kinetics, with structures of specific dimensions yielding much higher electrochemical signals and catalytic efficiencies. The electrocatalytic signals obtained when gold sensors were electrodeposited in both circular and linear apertures were studied, and the smallest structures plated in linear apertures were found to exhibit the best performance with high current densities and turnover rates. This study provides important information for optimal assay performance and insights for the future design and fabrication of high performance biomolecular assays.

Profiling circulating tumour cells and other biomarkers of invasive cancers

During cancer progression, many tumours shed circulating tumour cells (CTCs) and other biomarkers into the bloodstream. The analysis of CTCs offers the prospect of collecting a liquid biopsy from a patient’s blood to predict and monitor therapeutic responses and tumour recurrence. In this Review, we discuss progress towards the isolation and recovery of bulk CTCs from whole blood samples for the identification of cells with high metastatic potential. We provide an overview of the techniques that initially pointed to the clinical significance of CTCs and describe the key requirements for clinical applications of CTC analysis. We also summarize recent advances that permit the functional and biochemical phenotypes of CTCs to be characterized, and discuss the potential roles of these CTC characteristics in the formation of metastatic lesions. Moreover, we discuss the use of circulating tumour DNA and exosomes as markers for early cancer diagnosis and for the monitoring of cancer progression. Next-generation technologies and biomarkers for invasive cancers should allow for the unequivocal determination of the metastatic potential of CTCs, and for the meaningful analysis of circulating tumour DNA and exosomes.This Review discusses technology for the isolation and phenotypic profiling of circulating tumour cells from blood for the identification of those with high metastatic potential as well as requirements for clinical applications of the cells.

Amplified Micromagnetic Field Gradients Enable High-Resolution Profiling of Rare Cell Subpopulations

Analyzing small collections of cells is challenging because of the need for extremely high levels of sensitivity. We recently reported a new approach, termed magnetic ranking cytometry (MagRC), to profile nanoparticle-labeled cells. Using antibody-functionalized magnetic nanoparticles, we label cells so that each cells magnetization is proportional to its surface expression of a selected biomarker. Using a microfluidic device that sorts the cells into 100 different zones based on magnetic labeling levels, we generate profiles that report on the level and distribution of surface expression in small collections of cells. Here, we present a new set of studies investigating in depth parameters such as flow rate and magnetic nanoparticle size that affect device performance using both experiments and modeling. We present a model that further elucidates the mechanism of cell capture and use it to optimize device performance to efficiently capture rare cells. We show that this method has excellent specificity and can be used to characterize rare cells even in the presence of whole blood.