Showing papers by "Scott T. Phillips published in 2012"

Measuring Markers of Liver Function Using a Micropatterned Paper Device Designed for Blood from a Fingerstick

Abstract: This paper describes a paper-based microfluidic device that measures two enzymatic markers of liver function (alkaline phosphatase, ALP, and aspartate aminotransferase, AST) and total serum protein. A device consists of four components: (i) a top plastic sheet, (ii) a filter membrane, (iii) a patterned paper chip containing the reagents necessary for analysis, and (iv) a bottom plastic sheet. The device performs both the sample preparation (separating blood plasma from erythrocytes) and the assays; it also enables both qualitative and quantitative analysis of data. The data obtained from the paper-microfluidic devices show standard deviations in calibration runs and “spiked” standards that are acceptable for routine clinical use. This device illustrates a type of test useable for a range of assays in resource-poor settings.

“Fluidic batteries” as low-cost sources of power in paper-based microfluidic devices

Abstract: This communication describes the first paper-based microfluidic device that is capable of generating its own power when a sample is added to the device. The microfluidic device contains galvanic cells (that we term “fluidic batteries”) integrated directly into the microfluidic channels, which provides a direct link between a power source and an analytical function within the device. This capability is demonstrated using an example device that simultaneously powers a surface-mount UV LED and conducts an on-chip fluorescence assay.

Quantifying Analytes in Paper‐Based Microfluidic Devices Without Using External Electronic Readers

Abstract: Point-of-care (POC) and point-of-use assays are critical for identifying and measuring the quantity of analytes in a variety of environments that lack access to laboratory infrastructure. In quantitative versions of these assays, both the duration of the assay and the output signal must be measured. Measurements of time most often are performed using a timer that is external to the platform of the assay. Such measurements are relatively simple and inexpensive, and in some cases, can be integrated into the device itself. In contrast, measurements of signal typically are accomplished using hand-held electrochemical, absorbance, reflectance, transmittance, or fluorescence readers, and as such, these measurements can be complicated, time-consuming, and expensive, particularly in the context of extremely resource-limited environments such as remote villages in the developing world. The World Health Organization has identified the use of external readers as a challenge that must be overcome when creating ideal POC diagnostic assays for use in the developing world. In fact, they have listed “equipment-free” as one of seven necessary attributes for diagnostic tests in these regions. Herein, we describe two complimentary assay strategies that address this issue. By using paper-based microfluidic devices, we show that the level of an analyte can be quantified by simply measuring time: no external electronic reader is required for the quantitative measurement (Figure 1). The methods involve either 1) tracking the time required for a sample to react with and ultimately pass through a hydrophobic detection reagent in a single conduit within a threedimensional (3D) paper-based microfluidic device (Figure 1a) (we call this a digital assay), or 2) counting the number of bars that become colored after a fixed assay period in a related paper-based microfluidic device (Figure 1b; we refer to this as an analog assay). The methods described herein require only a timer, the ability to see color, and/or the

High throughput method for prototyping three-dimensional, paper-based microfluidic devices.

Abstract: This paper describes an efficient and high throughput method for fabricating three-dimensional (3D) paper-based microfluidic devices. The method avoids tedious alignment and assembly steps and eliminates a major bottleneck that has hindered the development of these types of devices. A single researcher now can prepare hundreds of devices within 1 h.

Self-powered microscale pumps based on analyte-initiated depolymerization reactions

Abstract: 1) those that are turned on and off byinput from the user; and 2) single-use pumps that are turnedon autonomously by exposure to a specific chemical signal,and therefore do not need to be turned off. The ideal pump inthis second category would combine sensing and pumpingcapabilities,andthuswouldenablepumpingthatiscontrolledby the presence and concentration of a specific analyte.Herein we describe the first examples of this second type ofmicroscale pump. We characterize this type of pump, andestablishboththechemicalandphysical–chemicalfoundationupon which future applied efforts will be based.The pumps consist of insoluble polymer films thatdepolymerize to release soluble monomeric products whenexposed to a specific analyte (Figure 1).

Measuring Binding of Protein to Gel-Bound Ligands Using Magnetic Levitation

Abstract: This paper describes the use of magnetic levitation (MagLev) to measure the association of proteins and ligands. The method starts with diamagnetic gel beads that are functionalized covalently with small molecules (putative ligands). Binding of protein to the ligands within the bead causes a change in the density of the bead. When these beads are suspended in a paramagnetic aqueous buffer and placed between the poles of two NbFeB magnets with like poles facing, the changes in the density of the bead on binding of protein result in changes in the levitation height of the bead that can be used to quantify the amount of protein bound. This paper uses a reaction-diffusion model to examine the physical principles that determine the values of rate and equilibrium constants measured by this system, using the well-defined model system of carbonic anhydrase and aryl sulfonamides. By tuning the experimental protocol, the method is capable of quantifying either the concentration of protein in a solution, or the binding affinities of a protein to several resin-bound small molecules simultaneously. Since this method requires no electricity and only a single piece of inexpensive equipment, it may find use in situations where portability and low cost are important, such as in bioanalysis in resource-limited settings, point-of-care diagnosis, veterinary medicine, and plant pathology. It still has several practical disadvantages. Most notably, the method requires relatively long assay times and cannot be applied to large proteins (>70 kDa), including antibodies. The design and synthesis of beads with improved characteristics (e.g., larger pore size) has the potential to resolve these problems.

A small molecule sensor for fluoride based on an autoinductive, colorimetric signal amplification reaction

Abstract: This article describes a small molecule reagent that is capable of detecting fluoride down to 0.12 mM (2.3 ppm) in water. The reagent reveals this level of fluoride through a novel autoinductive signal amplification reaction that produces an unambiguous colorimetric readout.

A Self-Immolative Spacer That Enables Tunable Controlled Release of Phenols under Neutral Conditions

Abstract: A current challenge in the area of responsive materials is the design of reagents and polymers that provide controlled release of phenols in environments that are less polar than water. In these contexts, a molecular strategy that enables release of nearly any phenol with predictable and tunable rates and without complication from background hydrolysis would substantially increase the precision with which materials can be designed to respond to a particular signal. This Article addresses this problem at the fundamental level by describing the design, synthesis, and physical-organic characterization of two small molecule self-immolative spacers that are capable of releasing phenols in organic and mixed organic–aqueous solutions. The rate of release from these small molecule model systems is predictable and tunable, such that nearly any type of phenol, regardless of pKa value, can be released in neutral solutions without complications from nonspecific background release due to hydrolysis. Furthermore, the r...

Using Smell To Triage Samples in Point-of-Care Assays†

Abstract: Smell of success: Reagent 1 provides the dual readouts of odor (ethanethiol) and fluorescence (derivative of 7-hydroxycoumarin) and can be used in down-selection assays based on smell and quantitative fluorescence assays of the samples that give a positive result. An important feature of 1 is the matched sensitivity of the two outputs. This reagent is designed for use in resource-limited settings and is demonstrated in assays that detect enzymes.

Phase switching to enable highly selective activity-based assays.

Abstract: Traditional activity-based (or reaction-based) detection schemes rely on homogeneous reactions between an analyte and a substrate to provide a signal that is proportional to the concentration of the analyte. Selectivity in these assays is governed primarily by the ability of the desired analyte to react faster than other analytes with the substrate. In this Article, we describe a conceptually different approach toward activity-based detection whereby a soluble analyte is converted intentionally into a heterogeneous catalyst. This catalyst then reacts selectively with a substrate to provide the readout for the assay. This concept is particularly relevant to heavy metal detection, as demonstrated by a rapid and highly selective assay for palladium in which a soluble metal ion is converted in situ into a colloidal catalyst.

Lateral flow and flow-through bioassay devices based on patterned porous media, methods of manufacturing the same, and methods of using the same

Abstract: PROBLEM TO BE SOLVED: To provide a lateral flow and flow-through bioassay device based on patterned porous media, a method of manufacturing the devices, and a method of using the devices.SOLUTION: Under one aspect, an assay device includes: a porous hydrophilic medium; a fluid impervious barrier comprising a polymerized photoresist, the barrier substantially permeating the thickness of the porous hydrophilic medium and defining a boundary of an assay region within the porous hydrophilic medium; and an assay reagent in the assay region.

Use of Catalytic Fluoride under Neutral Conditions for Cleaving Silicon—Oxygen Bonds.

Abstract: Silyl ethers can be efficiently cleaved in the presence of catalytic or substoichiometric amounts of fluorides.