Frank B. Myers

A Handheld Point-of-Care Genomic Diagnostic System

The rapid detection and identification of infectious disease pathogens is a critical need for healthcare in both developed and developing countries. As we gain more insight into the genomic basis of pathogen infectivity and drug resistance, point-of-care nucleic acid testing will likely become an important tool for global health. In this paper, we present an inexpensive, handheld, battery-powered instrument designed to enable pathogen genotyping in the developing world. Our Microfluidic Biomolecular Amplification Reader (µBAR) represents the convergence of molecular biology, microfluidics, optics, and electronics technology. The µBAR is capable of carrying out isothermal nucleic acid amplification assays with real-time fluorescence readout at a fraction of the cost of conventional benchtop thermocyclers. Additionally, the µBAR features cell phone data connectivity and GPS sample geotagging which can enable epidemiological surveying and remote healthcare delivery. The µBAR controls assay temperature through an integrated resistive heater and monitors real-time fluorescence signals from 60 individual reaction chambers using LEDs and phototransistors. Assays are carried out on PDMS disposable microfluidic cartridges which require no external power for sample loading. We characterize the fluorescence detection limits, heater uniformity, and battery life of the instrument. As a proof-of-principle, we demonstrate the detection of the HIV-1 integrase gene with the µBAR using the Loop-Mediated Isothermal Amplification (LAMP) assay. Although we focus on the detection of purified DNA here, LAMP has previously been demonstrated with a range of clinical samples, and our eventual goal is to develop a microfluidic device which includes on-chip sample preparation from raw samples. The µBAR is based entirely around open source hardware and software, and in the accompanying online supplement we present a full set of schematics, bill of materials, PCB layouts, CAD drawings, and source code for the µBAR instrument with the goal of spurring further innovation toward low-cost genetic diagnostics.

Robust Pluripotent Stem Cell Expansion and Cardiomyocyte Differentiation via Geometric Patterning

Geometric factors including the size, shape, density, and spacing of pluripotent stem cell colonies play a significant role in the maintenance of pluripotency and in cell fate determination. These factors are impossible to control using standard tissue culture methods. As such, there can be substantial batch-to-batch variability in cell line maintenance and differentiation yield. Here, we demonstrate a simple, robust technique for pluripotent stem cell expansion and cardiomyocyte differentiation by patterning cell colonies with a silicone stencil. We have observed that patterning human induced pluripotent stem cell (hiPSC) colonies improves the uniformity and repeatability of their size, density, and shape. Uniformity of colony geometry leads to improved homogeneity in the expression of pluripotency markers SSEA4 and Nanog as compared with conventional clump passaging. Patterned cell colonies are capable of undergoing directed differentiation into spontaneously beating cardiomyocyte clusters with improved yield and repeatability over unpatterned cultures seeded either as cell clumps or uniform single cell suspensions. Circular patterns result in a highly repeatable 3D ring-shaped band of cardiomyocytes which electrically couple and lead to propagating contraction waves around the ring. Because of these advantages, geometrically patterning stem cells using stencils may offer greater repeatability from batch-to-batch and person-to-person, an increase in differentiation yield, a faster experimental workflow, and a simpler protocol to communicate and follow. Furthermore, the ability to control where cardiomyocytes arise across a culture well during differentiation could greatly aid the design of electrophysiological assays for drug-screening.

A point-of-care instrument for rapid multiplexed pathogen genotyping

We are leveraging recent advances in rapid nucleic acid amplification chemistries, self-powered microfluidics, and low-cost optoelectronics to develop instrumentation for pathogen genotyping in the developing world. A growing number of correlations are emerging between genetic mutations in pathogens and their infectivity, origin, and drug resistance. Particularly for diseases like tuberculosis, where multi-drug resistance is a growing concern, a rapid diagnostic which could inform prescription decisions for newly diagnosed patients would not only save lives and reduce prolonged sickness but would help slow the emergence of more virulent strains. Additionally, for pathogens such as HIV, there is a need for new assay formats which can inexpensively and quantitativly monitor pathogen load. We have developed a portable instrument which uses disposable microfluidic assay cartridges pre-loaded with lyophilized reagents for genetic amplification of multiple markers. The cartridges can be adapted for a variety of sample types (blood, sputum, saliva). The instrument controls assay temperature and quantitatively monitors real-time fluorescence signals from 96 individual reaction chambers. The platform can be tailored for different economic situations — from a quantitative electronic readout to a simple binary readout with the naked eye.

Stimulation and artifact-free extracellular electrophysiological recording of cells in suspension

We have developed instrumentation which stimulates and records electrophysiological signals from populations of suspended cells in microfluidic channels. We are employing this instrumentation in a new approach to cell sorting and flow cytometry which distinguishes cells based on their electrophysiology. This label-free approach is ideal for applications where labeling or genetic modification of cells is undesirable, such as in purifying cells for tissue replacement therapies. Electrophysiology is a powerful indicator of phenotype for electrically-excitable cells such as myocytes and neurons. However, extracellular field potential signals are notoriously weak and large stimulus artifacts can easily obscure these signals if care is not taken to suppress them. This is particularly true for suspended cells. Here, we describe a novel microelectrode configuration and the associated instrumentation for suppressing stimulus artifacts and faithfully recovering the extracellular field potential signal. We show that the device is capable of distinguishing cardiomyocytes from non-cardiomyocytes derived from the same stem cell population. Finally, we explain the relationship between extracellular field potentials and the more familiar transmembrane action potential signal, noting the physiologically important features of these signals.

A Smartphone-Based Tool for Rapid, Portable, and Automated Wide-Field Retinal Imaging

Purpose High-quality, wide-field retinal imaging is a valuable method for screening preventable, vision-threatening diseases of the retina. Smartphone-based retinal cameras hold promise for increasing access to retinal imaging, but variable image quality and restricted field of view can limit their utility. We developed and clinically tested a smartphone-based system that addresses these challenges with automation-assisted imaging. Methods The system was designed to improve smartphone retinal imaging by combining automated fixation guidance, photomontage, and multicolored illumination with optimized optics, user-tested ergonomics, and touch-screen interface. System performance was evaluated from images of ophthalmic patients taken by nonophthalmic personnel. Two masked ophthalmologists evaluated images for abnormalities and disease severity. Results The system automatically generated 100° retinal photomontages from five overlapping images in under 1 minute at full resolution (52.3 pixels per retinal degree) fully on-phone, revealing numerous retinal abnormalities. Feasibility of the system for diabetic retinopathy (DR) screening using the retinal photomontages was performed in 71 diabetics by masked graders. DR grade matched perfectly with dilated clinical examination in 55.1% of eyes and within 1 severity level for 85.2% of eyes. For referral-warranted DR, average sensitivity was 93.3% and specificity 56.8%. Conclusions Automation-assisted imaging produced high-quality, wide-field retinal images that demonstrate the potential of smartphone-based retinal cameras to be used for retinal disease screening. Translational Relevance Enhancement of smartphone-based retinal imaging through automation and software intelligence holds great promise for increasing the accessibility of retinal screening.