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1.
Anal Chem ; 94(7): 3287-3295, 2022 02 22.
Artículo en Inglés | MEDLINE | ID: mdl-35138818

RESUMEN

The diversification of analytical tools for diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is imperative for effective virus surveillance and transmission control worldwide. Development of robust methods for rapid, simple isolation of viral RNA permits more expedient pathogen detection by downstream real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR) to minimize stalled containment and enhance treatment efforts. Here, we describe an automatable rotationally driven microfluidic platform for enrichment and enzymatic extraction of SARS-CoV-2 RNA from multiple sample types. The multiplexed, enclosed microfluidic centrifugal device (µCD) is capable of preparing amplification-ready RNA from up to six samples in under 15 min, minimizing user intervention and limiting analyst exposure to pathogens. Sample enrichment leverages Nanotrap Magnetic Virus Particles to isolate intact SARS-CoV-2 virions from nasopharyngeal and/or saliva samples, enabling the removal of complex matrices that inhibit downstream RNA amplification and detection. Subsequently, viral capsids are lysed using an enzymatic lysis cocktail for release of pathogenic nucleic acids into a PCR-compatible buffer, obviating the need for downstream purification. Early in-tube assay characterization demonstrated comparable performance between our technique and a "gold-standard" commercial RNA extraction and purification kit. RNA obtained using the fully integrated µCDs permitted reliable SARS-CoV-2 detection by real-time RT-PCR. Notably, we successfully analyzed full-process controls, positive clinical nasopharyngeal swabs suspended in viral transport media, and spiked saliva samples, showcasing the method's broad applicability with multiple sample matrices commonly encountered in clinical diagnostics.


Asunto(s)
COVID-19 , SARS-CoV-2 , Humanos , Microfluídica , Nasofaringe/química , ARN Viral/análisis , ARN Viral/genética , Sensibilidad y Especificidad
2.
Electrophoresis ; 43(16-17): 1746-1754, 2022 09.
Artículo en Inglés | MEDLINE | ID: mdl-35656648

RESUMEN

The laser print, cut, and laminate (PCL) method for microfluidic device fabrication can be leveraged for rapid and inexpensive prototyping of electrophoretic microchips useful for optimizing separation conditions. The rapid prototyping capability allows the evaluation of fluidic architecture, applied fields, reagent concentrations, and sieving matrix, all within the context of using fluorescence-compatible substrates. Cyclic olefin copolymer and toner-coated polyethylene terephthalate (tPeT) were utilized with the PCL technique and bonding methods optimized to improve device durability during electrophoresis. A series of separation channel designs and centrifugation conditions that provided successful loading of sieving polymer in less than 3 min was described. Separation of a 400-base DNA sizing ladder provided calculated base resolution between 3 and 4 bases, a greater than 18-fold improvement over separations on similar substrates. Finally, the accuracy and precision capabilities of these devices were demonstrated by separating and sizing DNA fragments of 147 and 167 bases as 148.62 ± 2 and 166.48 ± 3 bases, respectively.


Asunto(s)
ADN , Dispositivos Laboratorio en un Chip , Centrifugación , ADN/análisis , Electroforesis , Polímeros
3.
Anal Chem ; 93(19): 7300-7309, 2021 05 18.
Artículo en Inglés | MEDLINE | ID: mdl-33955733

RESUMEN

This report describes the development of a centrifugally controlled microfluidic dynamic solid-phase extraction (dSPE) platform to reliably obtain amplification-ready nucleic acids (NAs) directly from buccal swab cuttings. To our knowledge, this work represents the first centrifugal microdevice for comprehensive preparation of high-purity NAs from raw buccal swab samples. Direct-from-swab cellular lysis was integrated upstream of NA extraction, and automatable laser-controlled on-board microvalving strategies provided the strict spatiotemporal fluidic control required for practical point-of-need use. Solid-phase manipulation during extraction leveraged the application of a bidirectional rotating magnetic field to promote thorough interaction with the sample (e.g., NA capture). We illustrate the broad utility of this technology by establishing downstream compatibility of extracted nucleic acids with three noteworthy assays, namely, the polymerase chain reaction (PCR), reverse transcriptase PCR (RT-qPCR), and loop-mediated isothermal amplification (LAMP). The PCR-readiness of the extracted DNA was confirmed by generating short tandem repeat (STR) profiles following multiplexed amplification. With no changes to assay workflow, viral RNA was successfully extracted from contrived (spiked) SARS-CoV-2 swab samples, confirmed by RT-qPCR. Finally, we demonstrate the compatibility of the extracted DNA with LAMP-a technique well suited for point-of-need genetic analysis due to minimal hardware requirements and compatibility with colorimetric readout. We describe an automatable, portable microfluidic platform for the nucleic acid preparation device that could permit practical, in situ use by nontechnical personnel.


Asunto(s)
COVID-19 , Microfluídica , Humanos , Técnicas de Diagnóstico Molecular , Técnicas de Amplificación de Ácido Nucleico , SARS-CoV-2
4.
Anal Chem ; 93(48): 16213-16221, 2021 12 07.
Artículo en Inglés | MEDLINE | ID: mdl-34807557

RESUMEN

Increased opioid use and misuse have imposed large analytical demands across clinical and forensic sectors. Due to the absence of affordable, accurate, and simple on-site tests (e.g., point of interdiction and bedside), analysis is primarily conducted in centralized laboratories via time-consuming, labor-intensive methods. Many healthcare facilities do not have such analytical capabilities and must send samples to commercial laboratories, increasing turnaround time and care costs, as well as delaying public health warnings regarding the emergence of specific substances. Enzyme-linked immunosorbent assays (ELISAs) are used ubiquitously, despite lengthy workflows that require substantial manual intervention. Faster, reliable analytics are desperately needed to mitigate the mortality and morbidity associated with the current substance use epidemic. We describe one such alternative─a portable centrifugal microfluidic ELISA system that supplants repetitive pipetting with rotationally controlled fluidics. Embedded cellulosic membranes act as microvalves, permitting flow only when centrifugally generated hydraulic pressure exceeds their liquid entry pressure. These features enable stepwise reagent introduction, incubation, and removal simply by tuning rotational frequency. We demonstrate the success of this platform through sensitive, specific colorimetric detection of opiates, a subclass of opioids naturally derived from the opium poppy. Objective image analysis eliminated subjectivity in human color perception and permitted reliable detection of opiates in buffer and artificial urine at the ng/µL range. Opiates were clearly differentiated from other drug classes without interference from common adulterants known to cause false positive results in current colorimetric field tests. Eight samples were simultaneously analyzed in under 1 h, a marked reduction from the traditional multiday timeline. This approach could permit rapid, automatable ELISA-based drug detection outside of traditional laboratories by nontechnical personnel.


Asunto(s)
Preparaciones Farmacéuticas , Detección de Abuso de Sustancias , Colorimetría , Ensayo de Inmunoadsorción Enzimática , Humanos , Microfluídica
5.
Anal Chem ; 92(19): 13343-13353, 2020 10 06.
Artículo en Inglés | MEDLINE | ID: mdl-32838514

RESUMEN

Loop-mediated isothermal amplification (LAMP) as a diagnostic tool is rapidly gaining recognition and maturity. Among various advantages over traditional polymerase chain reaction, the ability to visually detect amplification by the incorporation of colorimetric indicators is one of its most unique features. There is an overwhelming variety of LAMP indicators in the literature, yet a comprehensive comparative study is lacking. This study evaluates the use of hydroxynaphthol blue, phenol red, calcein, leuco crystal violet, malachite green, and a fluorescent dye for visual detection. A method for objective quantitative analysis using ImageJ is described that is readily implemented in standard and microfluidic workflows. The work here also includes the largest inter-reader variability study involving 24 participants to evaluate these indicators. We found inaccuracies in visual assessment as bias and/or individual-based perception can exist, solidifying the need for objective analysis. There was not a "universal" indicator, although considerations in sample preparation, storage, and applicability are discussed in length.


Asunto(s)
Fluoresceínas/análisis , Indicadores y Reactivos/química , Técnicas de Diagnóstico Molecular , Técnicas de Amplificación de Ácido Nucleico , Colorimetría , Fluoresceínas/química , Colorantes Fluorescentes/química , Violeta de Genciana/química , Humanos , Dispositivos Laboratorio en un Chip , Naftalenosulfonatos/química , Fenolsulfonftaleína/química , Colorantes de Rosanilina/química
6.
Anal Chem ; 91(3): 2186-2191, 2019 02 05.
Artículo en Inglés | MEDLINE | ID: mdl-30652864

RESUMEN

We report an improved separation method for the isolation of sperm cells from dilute, "large volume" samples containing female DNA using bead-assisted acoustic trapping. In an enclosed glass-PDMS-glass (GPG) resonator, we exploit a three-layer microfluidic architecture to generate "trapping nodes" in ultrasonic standing waves. We investigate the dependence of trapping efficiency on particle concentration for both sperm cells and polymeric beads. After determination of the critical concentration of polymeric beads required to seed the trapping event, sperm cells in dilute solution are trapped as a result of the enhanced secondary radiation force (SRF). Sperm-cell-containing samples with volumes up to 300 µL and cell concentrations as low as ∼10 cells/µL are amenable to effective trapping in the presence of an abundance of female DNA in solution. Complete processing of samples is accomplished with separation of the female and male fractions within 15 min. We demonstrate that the collected fractions are amenable to subsequent DNA extraction, short tandem repeat PCR, and the generation of STR profiles for the isolated sperm cells.


Asunto(s)
Acústica , Separación Celular , ADN/genética , Dimetilpolisiloxanos/química , Técnicas Analíticas Microfluídicas , Espermatozoides/citología , Separación Celular/instrumentación , Femenino , Vidrio , Humanos , Masculino , Técnicas Analíticas Microfluídicas/instrumentación
7.
Anal Chem ; 89(5): 3228-3234, 2017 03 07.
Artículo en Inglés | MEDLINE | ID: mdl-28192917

RESUMEN

Total bilirubin (T-Bil) is an important clinical diagnostic marker that is measured frequently by physicians to assist in the diagnosis, treatment, and monitoring of multiple medical conditions. The work demonstrated here utilizes the 48-year-old mechanism of phototherapy that is commonly implemented in the treatment of infants with exaggerated physiologic and pathologic jaundice but adapts it to the microfluidic level for the ultimate purpose of total bilirubin quantitation. After acquisition of a small volume of blood (<10 µL) and through subsequent separation (plasma + red blood cells), a 3 µL plasma sample was imaged by a portable scanner and analyzed through a custom algorithm for color intensity. After blue light irradiation for 10 min at 470 nm, the sample was reimaged and analyzed. The resulting intensities obtained pre- and postimaging (clearly observed through a color change from yellow to clear) were then utilized to calculate the total bilirubin concentration. A total of 34 blood samples were analyzed with microfluidic photo treatment-image analysis (µPIA) and were found to have a Deming-regression slope of 0.97 (R2 = 0.960) when compared to the total bilirubin values determined in the clinical laboratory. We demonstrate the implementation of a centrifugal microdevice fabricated through the Print, Cut, and Laminate (PCL) method that accepts eight whole blood samples and provides the capabilities to not only quantitate total bilirubin (Deming-regression slope of 0.95, R2 = 0.990) but allow future integration with excess plasma sufficient for additional downstream clinical assays. This work will highlight the inexpensive nature of the analysis (absence of caustic, viscous, or additional reagents), the simplicity (does not require any chemical reactions), speed (sample-to-answer in <15 min), insusceptibility to biofouling (no protein matrix effects, hemoglobin interferences, and minimized turbidity), low volume plasma requirement (3 µL), and the ability for future downstream integration.


Asunto(s)
Bilirrubina/sangre , Microfluídica/métodos , Algoritmos , Bilirrubina/química , Humanos , Láseres de Semiconductores , Luz , Microfluídica/instrumentación , Oxidación-Reducción
8.
Analyst ; 142(2): 366-374, 2017 01 16.
Artículo en Inglés | MEDLINE | ID: mdl-27990512

RESUMEN

Warfarin, a commonly prescribed oral anticoagulant, is burdened by a narrow therapeutic index and high inter-individual variability in response, making it the second leading cause of drug-related emergency room visits. Since genetic factors contribute significantly to warfarin sensitivity, a genotype-guided dosing strategy may reduce the occurrence of adverse events. While numerous methods have been demonstrated for warfarin genotyping, the specifications of most assays with respect to turnaround time and cost are not ideal for routine testing. Here, we present a unique method for warfarin genotyping based on multiplex PCR coupled with Hybridization-induced Aggregation (HIA), a bead-based technique for sequence-specific detection. A multiplex allele-specific PCR reaction was used to generate products corresponding to 3 genetic variants associated with warfarin sensitivity [CYP2C9 *2, CYP2C9 *3, and VKORC1 (1173C>T)] and an internal control product. The products were detected simultaneously on a poly(ethylene terephthalate) (PeT) microdevice using HIA, which provided genotyping results in approximately 15 minutes following PCR. The genotyping results of 23 patient DNA samples using this approach were in 100% concordance with the results of a validated test (WARFGENO test, ARUP laboratories). Additionally, the PCR reaction was successfully transferred to a PeT chip, which provided accurate genotyping results from patient DNA samples in under an hour. This work demonstrates a simple, rapid, and affordable approach to warfarin genotyping based on multiplex allele-specific PCR coupled with HIA detection. By demonstrating both chemistries on PeT microdevices, we show the potential for integration on a single device for sample-to-answer genotyping.


Asunto(s)
Técnicas de Genotipaje/métodos , Tereftalatos Polietilenos/química , Warfarina/administración & dosificación , Citocromo P-450 CYP2C9/genética , Sondas de ADN/genética , Genotipo , Humanos , Reacción en Cadena de la Polimerasa Multiplex/métodos , Mutación , Hibridación de Ácido Nucleico , Vitamina K Epóxido Reductasas/genética
9.
Anal Chem ; 88(5): 2652-8, 2016 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-26878418

RESUMEN

In this work, we report a novel method for the creation of superhydrophilic patterns on the surface of hydrophobically coated glass through CO2 laser cleaning. This mask-free approach requires no photolithography for the print of the features, and only a single-step surface pretreatment is needed. The laser-cleaned glass surface enables self-partitioning of liquid into droplet arrays with controllable, quantitative volumes. We further designed wall-less cell arrays for the mapping of culturing conditions and demonstrated the potential of this droplet-arraying method.

10.
Anal Chem ; 88(22): 11046-11054, 2016 11 15.
Artículo en Inglés | MEDLINE | ID: mdl-27779404

RESUMEN

We recently defined a magnetic bead-based assay that exploited an agglutination-like response for DNA and applied it to DNA-containing cell enumeration using inexpensive benchtop hardware [ J. Am. Chem. Soc. 2012 , 134 ( 12 ), 5689 - 96 ]. Although cost-efficient, the open-well format assay required numerous manual steps, and the magnetic field actuation scheme was not readily adaptable for integration. Here, we demonstrate a low-cost (<$2 in-lab), higher-throughput "pinwheel assay" platform that relies on a combination of a disposable rotation-driven microdisc (RDM), and a simple bidirectional rotating magnetic field (bi-RMF). The assay was transformed into an integrated microfluidic system using a multilayered polyester microfluidic disc created through laser print, cut and laminate fabrication, with fluid flow controlled by rotation speed without any mechanical valves. The RDM accepts four samples that undergo on-chip dilution to five different concentrations that cover the effective concentration range needed for downstream cell counting by pinwheel assay. We show that a bi-RMF is effective for the simultaneous actuation of pinwheel assays in 20 detection chambers. The optimization of the bi-RMF frequencies allows the RDM-based pinwheel assay detect human genomic DNA down to a mass of human genomic DNA (5.5 picograms) that is roughly equal to the mass in a single cell. For proof of principle, enumeration of the white blood cells in human blood samples on the RDM provided data correlating well (C.V. of 10%) with those obtained in a clinical lab. Fusing the cost-effective RDM with a simple bi-RMF provides a promising strategy for automation and multiplexing of magnetic particle-based agglutination assays.


Asunto(s)
Recuento de Células Sanguíneas/instrumentación , Recuento de Células Sanguíneas/métodos , Separación Inmunomagnética/métodos , Leucocitos/citología , Técnicas Analíticas Microfluídicas/instrumentación , Rotación , ADN/análisis , Humanos , Separación Inmunomagnética/instrumentación , Campos Magnéticos , Técnicas Analíticas Microfluídicas/métodos
12.
Anal Chem ; 88(17): 8689-97, 2016 09 06.
Artículo en Inglés | MEDLINE | ID: mdl-27525468

RESUMEN

Current colorimetric presumptive identification of illicit drugs for determining illegal possession of controlled substances by law enforcement relies solely on the subjective interpretation of color change using drug- or class-specific reactions. Here, we describe the use of inexpensive polyester-toner, rotation-driven microfluidic devices with a smartphone as a potential alternative for current presumptive colorimetric field-testing of illicit drugs, allowing for an objective and user-friendly image analysis technique for detection. The centrifugal microfluidic platform accommodates simultaneous presumptive testing of material from a single input to multiple reaction chambers, enabling rapid screening. Hue and saturation image analysis parameters are used to define threshold values for the detection of cocaine and methamphetamine as proof-of-principle with 0.25 and 0.75 mg/mL limits of detection, respectively, with nonvolatile reagents stored on-board and smartphone for detection. Reported LODs are lower than those concentrations used in the field. Additionally, the developed objective detection method addresses the testing of drugs with various common cutting agents, including those known to produce false negative and positive results. We demonstrate the effectiveness of the method by successfully identifying the composition of 30 unknown samples.


Asunto(s)
Drogas Ilícitas/análisis , Técnicas Analíticas Microfluídicas , Teléfono Inteligente , Detección de Abuso de Sustancias , Colorimetría/instrumentación , Técnicas Analíticas Microfluídicas/instrumentación , Teléfono Inteligente/instrumentación , Detección de Abuso de Sustancias/instrumentación
13.
Electrophoresis ; 37(23-24): 3046-3058, 2016 12.
Artículo en Inglés | MEDLINE | ID: mdl-27620618

RESUMEN

This work describes the development of a novel microdevice for forensic DNA processing of reference swabs. This microdevice incorporates an enzyme-based assay for DNA preparation, which allows for faster processing times and reduced sample handling. Infrared-mediated PCR (IR-PCR) is used for STR amplification using a custom reaction mixture, allowing for amplification of STR loci in 45 min while circumventing the limitations of traditional block thermocyclers. Uniquely positioned valves coupled with a simple rotational platform are used to exert fluidic control, eliminating the need for bulky external equipment. All microdevices were fabricated using laser ablation and thermal bonding of PMMA layers. Using this microdevice, the enzyme-mediated DNA liberation module produced DNA yields similar to or higher than those produced using the traditional (tube-based) protocol. Initial microdevice IR-PCR experiments to test the amplification module and reaction (using Phusion Flash/SpeedSTAR) generated near-full profiles that suffered from interlocus peak imbalance and poor adenylation (significant -A). However, subsequent attempts using KAPA 2G and Pfu Ultra polymerases generated full STR profiles with improved interlocus balance and the expected adenylated product. A fully integrated run designed to test microfluidic control successfully generated CE-ready STR amplicons in less than 2 h (<1 h of hands-on time). Using this approach, high-quality STR profiles were developed that were consistent with those produced using conventional DNA purification and STR amplification methods. This method is a smaller, more elegant solution than current microdevice methods and offers a cheaper, hands-free, closed-system alternative to traditional forensic methods.


Asunto(s)
ADN/análisis , Genética Forense/métodos , Técnicas Analíticas Microfluídicas/instrumentación , Técnicas Analíticas Microfluídicas/métodos , Repeticiones de Microsatélite/genética , Reacción en Cadena de la Polimerasa/métodos , ADN/genética , Diseño de Equipo , Humanos
14.
Analyst ; 141(3): 947-55, 2016 Feb 07.
Artículo en Inglés | MEDLINE | ID: mdl-26658961

RESUMEN

Rapid, inexpensive and simplistic nucleic acid testing (NAT) is pivotal in delivering biotechnology solutions at the point-of-care (POC). We present a poly(methylmethacrylate) (PMMA) microdevice where on-board infrared-mediated PCR amplification is seamlessly integrated with a particle-based, visual DNA detection for specific detection of bacterial targets in less than 35 minutes. Fluidic control is achieved using a capillary burst valve laser-ablated in a novel manner to confine the PCR reagents to a chamber during thermal cycling, and a manual torque-actuated pressure system to mobilize the fluid from the PCR chamber to the detection reservoir containing oligonucleotide-adducted magnetic particles. Interaction of amplified products specific to the target organism with the beads in a rotating magnetic field allows for near instantaneous (<30 s) detection based on hybridization-induced aggregation (HIA) of the particles and simple optical analysis. The integration of PCR with this rapid, sequence-specific DNA detection method on a single microdevice presents the possibility of creating POC NAT systems that are low cost, easy-to-use, and involve minimal external hardware.


Asunto(s)
Dispositivos Laboratorio en un Chip , Reacción en Cadena de la Polimerasa/instrumentación , Salmonella enterica/aislamiento & purificación , ADN Bacteriano/análisis , ADN Bacteriano/genética , Hibridación de Ácido Nucleico , Polimetil Metacrilato/química , Presión , Salmonella enterica/genética , Integración de Sistemas , Torque
15.
Analyst ; 141(19): 5637-45, 2016 Oct 07.
Artículo en Inglés | MEDLINE | ID: mdl-27460478

RESUMEN

Pathogen detection has traditionally been accomplished by utilizing methods such as cell culture, immunoassays, and nucleic acid amplification tests; however, these methods are not easily implemented in resource-limited settings because special equipment for detection and thermal cycling is often required. In this study, we present a magnetic bead aggregation assay coupled to an inexpensive microfluidic fabrication technique that allows for cell phone detection and analysis of a notable pathogen in less than one hour. Detection is achieved through the use of a custom-built system that allows for fluid flow control via centrifugal force, as well as manipulation of magnetic beads with an adjustable rotating magnetic field. Cell phone image capture and analysis is housed in a 3D-printed case with LED backlighting and a lid-mounted Android phone. A custom-written application (app.) is employed to interrogate images for the extent of aggregation present following loop-mediated isothermal amplification (LAMP) coupled to product-inhibited bead aggregation (PiBA) for detection of target sequences. Clostridium difficile is a pathogen of increasing interest due to its causative role in intestinal infections following antibiotic treatment, and was therefore chosen as the pathogen of interest in the present study to demonstrate the rapid, cost-effective, and sequence-specific detection capabilities of the microfluidic platform described herein.

16.
Analyst ; 141(15): 4667-75, 2016 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-27250903

RESUMEN

To date, the forensic community regards solid phase extraction (SPE) as the most effective methodology for the purification of DNA for use in short tandem repeat (STR) polymerase chain reaction (PCR) amplification. While a dominant methodology, SPE protocols generally necessitate the use of PCR inhibitors (guanidine, IPA) and, in addition, can demand timescales of up to 30 min due to the necessary load, wash and elution steps. The recent discovery and characterization of the EA1 protease has allowed the user to enzymatically extract (not purify) DNA, dramatically simplifying the task of producing a PCR-ready template. Despite this, this procedure has yet to make a significant impact on microfluidic technologies. Here, we describe a microfluidic device that implements the EA1 enzyme for DNA extraction by incorporating it into a hybrid microdevice comprising laminated polyester (Pe) and PMMA layers. The PMMA layer provides a macro-to-micro interface for introducing the biological sample into the microfluidic architecture, whilst also possessing the necessary dimensions to function as the swab acceptor. Pre-loaded reagents are then introduced to the swab chamber centrifugally, initiating DNA extraction at 75 °C. The extraction of DNA occurs in timescales of less than 3 min and any external hardware associated with the transportation of reagents by pneumatic pumping is eliminated. Finally, multiplexing is demonstrated with a circular device containing eight separate chambers for the simultaneous processing of eight buccal swab samples. The studies here provide DNA concentrations up to 10 ng µL(-1) with a 100% success rate in less than 3 minutes. The STR profiles generated using these extracted samples demonstrate that the DNA is of PCR forensic-quality and adequate for human identification.


Asunto(s)
ADN/aislamiento & purificación , Enzimas , Técnicas Analíticas Microfluídicas , Polimetil Metacrilato , Humanos , Poliésteres , Reacción en Cadena de la Polimerasa
17.
Anal Chem ; 87(20): 10275-82, 2015 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-26339780

RESUMEN

Using hybridization-induced aggregation (HIA), a unique bead-based DNA detection technology scalable for a microchip platform, we describe a simplistic, low-cost method for rapid mutation testing. HIA utilizes a pair of sequence-specific oligonucleotide probes bound to magnetic microbeads. Hybridization to a target DNA strand tethers the beads together, inducing bead aggregation. By simply using the extent of bead aggregation as a measure of the hybridization efficiency, we avoid the need for additional labels and sophisticated analytical equipment. Through strategic manipulation of the assay design and experimental parameters, we use HIA to facilitate, for the first time, the detection of single base mutations in a gene segment and, specifically, the detection of activating KRAS mutations. Following the development and optimization of the assay, we apply it for KRAS mutation analysis of four human cancer cell lines. Ultimately, we present a proof-of-principle method for detecting any of the common KRAS mutations in a single-step, 2 min assay, using only one set of oligonucleotide probes, for a total analysis time of less than 10 min post-PCR. The assay is performed at room temperature and uses simple, inexpensive instrumentation that permits multiplexed analysis.


Asunto(s)
Análisis Mutacional de ADN/métodos , Microesferas , Mutación/genética , Hibridación de Ácido Nucleico , Proteínas Proto-Oncogénicas p21(ras)/genética , Línea Celular Tumoral , Humanos , Fenómenos Magnéticos , Sondas de Oligonucleótidos/química , Sondas de Oligonucleótidos/genética , Reacción en Cadena de la Polimerasa , Factores de Tiempo
18.
Analyst ; 140(6): 2008-15, 2015 Mar 21.
Artículo en Inglés | MEDLINE | ID: mdl-25673152

RESUMEN

In a recent publication, we presented a label-free method for the detection of specific DNA sequences through the hybridization-induced aggregation (HIA) of a pair of oligonucleotide-adducted magnetic particles. Here we show, through the use of modified hardware, that we are able to simultaneously analyze multiple (4) samples, and detect a 26-mer ssDNA sequence at femtomolar concentrations in minutes. As such, this work represents an improvement in throughput and a 100-fold improvement in sensitivity, compared to that reported previously. Here, we also investigate the design parameters of the target sequence, in an effort to maximize the sensitivity of HIA and to use as a guide in future applications of this work. Modifications were made to the original 26-mer oligonucleotide sequence to evaluate the effects of: (1) non-complementary flanking bases, (2) target sequence length, and (3) single base mismatches on aggregation response. The aggregation response decreased as the number of the non-complementary flanking bases increased, with only a five base addition lowering the LOD by four orders of magnitude. Low sensitivity was observed with short sequences of 6 and 10 complementary bases, which were only detectable at micromolar concentrations. Target sequences with 20, 26 or 32 complementary bases provided the greatest sensitivity and were detectable at femtomolar concentrations. Additionally, HIA could effectively differentiate sequences that were fully complementary from those containing 1, 2 or 3 single base mismatches at micromolar concentrations. The robustness of the HIA system to other buffer components was explored with nine potential assay interferents that could affect hybridization (aggregation) or falsely induce aggregation. Of these, purified BSA and lysed whole blood induced a false aggregation. None of the interferents inhibited aggregation when the hybridizing target was added. Having delineated the fundamental parameters affecting HIA-target hybridization, and demonstrating that HIA had the selectivity to detect single base mismatches, this fluor-free end-point detection has the potential to become a powerful tool for microfluidic DNA detection.


Asunto(s)
ADN/genética , Hibridación de Ácido Nucleico/métodos , Disparidad de Par Base , Secuencia de Bases , Técnicas Biosensibles/métodos , ADN/análisis , ADN de Cadena Simple/análisis , ADN de Cadena Simple/genética , Diseño de Equipo , Límite de Detección , Mutación Puntual
19.
Anal Chem ; 86(16): 8192-9, 2014 Aug 19.
Artículo en Inglés | MEDLINE | ID: mdl-25091472

RESUMEN

A system that automatically performs the PCR amplification and microchip electrophoretic (ME) separation for rapid forensic short tandem repeat (STR) forensic profiling in a single disposable plastic chip is demonstrated. The microchip subassays were optimized to deliver results comparable to conventional benchtop methods. The microchip process was accomplished in sub-90 min compared with >2.5 h for the conventional approach. An infrared laser with a noncontact temperature sensing system was optimized for a 45 min PCR compared with the conventional 90 min amplification time. The separation conditions were optimized using LPA-co-dihexylacrylamide block copolymers specifically designed for microchip separations to achieve accurate DNA size calling in an effective length of 7 cm in a plastic microchip. This effective separation length is less than half of other reports for integrated STR analysis and allows a compact, inexpensive microchip design. This separation quality was maintained when integrated with microchip PCR. Thirty samples were analyzed conventionally and then compared with data generated by the microfluidic chip system. The microfluidic system allele calling was 100% concordant with the conventional process. This study also investigated allelic ladder consistency over time. The PCR-ME genetic profiles were analyzed using binning palettes generated from two sets of allelic ladders run three and six months apart. Using these binning palettes, no allele calling errors were detected in the 30 samples demonstrating that a microfluidic platform can be highly consistent over long periods of time.


Asunto(s)
ADN/análisis , Electroforesis por Microchip/instrumentación , Reacción en Cadena de la Polimerasa Multiplex/instrumentación , Diseño de Equipo , Humanos , Análisis de Secuencia por Matrices de Oligonucleótidos/instrumentación
20.
Micromachines (Basel) ; 15(2)2024 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-38398999

RESUMEN

Isothermal amplification methods have become popular in research due to the simplicity of the technology needed to run the reactions. Specifically, loop-mediated isothermal amplification (LAMP) has been widely used for various applications since first reported in 2000. LAMP reactions are commonly monitored with the use of colorimetry. Although color changes associated with positive amplification are apparent to the naked eye, this detection method is subjective due to inherent differences in visual perception from person to person. The objectivity of the colorimetric detection method may be improved by programmed image capture over time with simultaneous heating. As such, the development of a novel, one-step, automated, and integrated analysis system capable of performing these tasks in parallel is detailed herein. The device is adaptable to multiple colorimetric dyes, cost-effective, 3D-printed for single-temperature convective heating, and features an easy-to-use LabVIEW software program developed for automated image analysis. The device was optimized and subsequently validated using four messenger-RNA targets and mock forensic samples. The performance of our device was determined to be comparable to that of a conventional thermal cycler and smartphone image analysis, respectively. Moreover, the outlined system is capable of objective colorimetric analysis, with exceptional throughput of up to 96 samples at once.

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