Welcome to Landers Group !

 News and Recent Events

March 23, 2012Congratulations ! Yiwen and Kerui are winners (2nd and 3rd places in the physical science and mathemathics) in the poster competition of the 2012 Huskey research exhibition.

March 16, 2012 - Article in Press: "New detection modality for label-free qauntification of DNA in biological samples via superparamagnetic bead aggregation" - Jingyi Li and Dan Leslie - Journal of American Chemical Society (JACS) - DOI: 10.1021/ja300839n.

March 11-15, 2012 - Brian gave his talk entitled "Disposable Microfluidic Devices for Rapid Processing of Sexual Assault Samples", Qian gave her talk entitled "A Novel CD4+ T Cell Counter for HIV/AIDS Patients", and Yiwen presented her poster entitled "Design and Fabbrication fo a CD-like Disposable Microfluidic Platform for Serial Dilutions" at 2012 PITTCON conference in Orlando, FL. 



                       
February 20-25, 2012 - Jenny presented her posters entitled "Towards a Multi-Chamber Plastic Microdevice for Simultaneous Amplification of Multiple DNA Samples" and Briony presented her posters entitled "Volume Reduction Solid Phase Extraction of Forensic Samples on a Plastic Microfluidic Device" at the 64th American Academy of Forensic Sciences Annual Scientific Meeting in Atlanta, GA.





February 14, 2012
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Congrats to Dan and Qian for successfully passing their candidacy exams!

February 7, 2012 - Brian's article entitled "Warfarin genotyping in a single PCR reaction for microchip electrophoresis" is published in this month's issue of Clinical Chemistry.
                       

  Abstract: "Warfarin is the most commonly prescribed oral anticoagulant medication but also is the second leading cause of emergency room visits for adverse drug reactions. Genetic testing for warfarin sensitivity may reduce hospitalization rates, but prospective genotyping is impeded in part by the turnaround time and costs of genotyping. Microfluidics-based assays can reduce reagent consumption and analysis time; however, no current assay has integrated multiplexed allele-specific PCR for warfarin genotyping with electrophoretic microfluidics hardware. Ideally, such an assay would use a single PCR reaction and, without further processing, a single microchip electrophoresis (ME) run to determine the 3 single-nucleotide polymorphisms (SNPs) affecting warfarin sensitivity"



January 1, 2012 - Dan's article entitled "Platinum nanoparticle-facilitated reflective surfaces for non-contact temperature control in microfluidic devices for PCR amplification" is published in this week's issue of Lab on a Chip.

  Abstract: "The polymerase chain reaction (PCR) is critical for amplification of target sequences of DNA or RNA that have clinical, biological or forensic relevance. While extrinsic Fabry-Perot interferometry (EFPI) has been shown to be adequate for non-contact temperature sensing, the difficulty in defining a reflective surface that is semi-reflective, non-reactive for PCR compatibility and adherent for thermal bonding has limited its exploitation. Through the incorporation of a reflective surface fabricated using a thermally driven self-assembly of a platinum nanoparticle monolayer on the surface of the microfluidic chamber, an enhanced EFPI signal results, allowing for non-contact microfluidic temperature control instrumentation that uses infrared-mediated heating, convective forced-air cooling, and interferometic temperature sensing. The interferometer is originally calibrated with a miniature copper-constantan thermocouple in the PCR chamber resulting in temperature sensitivities of −22.0 to −32.8 nm/degree, depending on the chamber depth. This universal calibration enables accurate temperature control in any device with arbitrary dimensions, thereby allowing versatility in various applications. Uniquely, this non-contact temperature control for PCR thermocycling is applied to the amplification of STR loci for human genetic profiling, where nine STR loci are successfully amplified for human identification using the EFPI-based non-contact thermocycling."

January 2012
- Happy New Year!

December 2011
- Welcome to Kimberly Jackson and Hillary Sloane, our newest lab members!

November 14, 2011 - 
Congratulations ! Jingyi and Yiwen (Helio Biotech) are the College of Arts and Sciences winners of UVa Entrpreneurship Cup Competition.

October 27, 2011 - Article in Press: "Platinum nanoparticle-facilitated reflective surfaces for non-contact temperature control in microfluidic devices for PCR amplification" - Dan Leslie - Lab on a Chip  -doi10.1039/C1LC20779B
                       
October 2-6, 2011 - Jenny presented her poster entitled "A Multi-chamber PMMA Microdevice for Simultaneous Amplification of Up To Seven Individual Samples Using Infrared-Mediated PCR", Jingyi presented his posters entitled "Multiplex Pinwheel Assay: Micro-sale Optical and Label-free Quantitation of DNA with High-throughput and Low Cost" and "Pinwheel Assay Via a 'Pipet, Aggregate and Blot (PAB)", Kyudam presented his posters entitled "Microwave-Assisted PCR in Disposable Microdevices" and "Droplet-Based PCR using Infrared-Mediated Heating System", Briony gave a talk entitled "Specific DNA Sequence Detection Through Hybridization Induced Aggregation (HIA)" and presented her poster entitled "Label-Free Detection and Quantization of Nulceic Acids with 1uM Superparamagnetic Particles", Kerui presented his poster entitled "Fluidic Capacitor-Based, Self-Contained and Self-Powered Microfluidic Chip", Yiwen presented her poster entitled "Development of Disposable Multichambered Microchip for PCR Via Non-Contact IR Mediated Thermal Control",  and Dan presented his poster entitled "Towards the Development of a Microfluidics Device for the Separation and Isolation of Circulation Tumor Cells from Whole Blood Using Acuostophoresis" at the 15th International Micro Total Analysis Systems (uTAS) conference (Chairman, Dr. Landers) in Seattle, WA. 

July 1, 2011 - Gabriela's article entitled "Dynamic solid phase DNA extraction and PCR amplification in polyester-toner based microchip" is published in this week's issue of Analytical Chemistry.
                       
  Abstract: "
A variety of substrates have been used for fabrication of microchips for DNA extraction, PCR amplification, and DNA fragment separation, including the more conventional glass and silicon as well as alternative polymer-based materials. Polyester represents one such polymer, and the laser-printing of toner onto polyester films has been shown to be effective for generating polyester-toner (PeT) microfluidic devices with channel depths on the order of tens of micrometers. Here, we describe a novel and simple process that allows for the production of multilayer, high aspect-ratio PeT microdevices with substantially larger channel depths. This innovative process utilizes a CO(2) laser to create the microchannel in polyester sheets containing a uniform layer of printed toner, and multilayer devices can easily be constructed by sandwiching the channel layer between uncoated cover sheets of polyester containing precut access holes. The process allows the fabrication of deep channels, with ∼270 μm, and we demonstrate the effectiveness of multilayer PeT microchips for dynamic solid phase extraction (dSPE) and PCR amplification. With the former, we found that (i) more than 65% of DNA from 0.6 μL of blood was recovered, (ii) the resultant DNA was concentrated to greater than 3 ng/μL (which was better than other chip-based extraction methods), and (iii) the DNA recovered was compatible with downstream microchip-based PCR amplification. Illustrative of the compatibility of PeT microchips with the PCR process, the successful amplification of a 520 bp fragment of λ-phage DNA in a conventional thermocycler is shown. The ability to handle the diverse chemistries associated with DNA purification and extraction is a testimony to the potential utility of PeT microchips beyond separations and presents a promising new disposable platform for genetic analysis that is low cost and easy to fabricate."

May 7, 2011
- Congratulations ! Carmen's article is featured on the cover of Lab on a Chip and this article entitled "Solid phase extraction of DNA from biological samples in a post-based, high surface area poly(methyl methacrylate) (PMMA) microdevice" is published in this week's issue of Lab on a Chip.
 
Abstract: "This work describes the performance of poly(methyl methacrylate) (PMMA) microfluidic DNA purification devices with embedded microfabricated posts, functionalized with chitosan. PMMA is attractive as a substrate for creating high surface area (SA) posts for DNA capture because X-ray lithography can be exploited for extremely reproducible fabrication of high SA structures. However, this advantage is offset by the delicate nature of the posts when attempting bonding to create a closed system, and by the challenge of functionalizing the PMMA surface with a group that invokes DNA binding. Methods are described for covalent functionalization of the post surfaces with chitosan that binds DNA in a pH-dependent manner, as well as for bonding methods that avoid damaging the underlying post structure. A number of geometric posts designs are explored, with the goal of identifying post structures that provide the requisite surface area without a concurrent rise in fluidic resistance that promotes device failure. Initial proof-of-principle is shown by recovery of prepurified human genomic DNA (hgDNA), with real-world utility illustrated by purifying hgDNA from whole blood and demonstrating it to be PCR-amplifiable."

April 14, 2011 - Congratulations ! Jingyi is a winner in the poster competition of the 8th presidential inauguration event.


March 21, 2011 - Kristin's article entitled "A valveless microfluidic device for integrated solid phase extraction and polymerase chain reaction for short tandem repeat (STR) anaylsis" is published in this week's issue of Analyst.                        
  Abstract: "A valveless microdevice has been developed for the integration of solid phase extraction (SPE) and polymerase chain reaction (PCR) on a single chip for the short tandem repeat (STR) analysis of DNA from a biological sample. The device consists of two domains--a SPE domain filled with silica beads as a solid phase and a PCR domain with an ~500 nL reaction chamber. DNA from buccal swabs was purified and amplified using the integrated device and a full STR profile (16 loci) resulted. The 16 loci Identifiler® multiplex amplification was performed using a non-contact infrared (IR)-mediated PCR system built in-house, after syringe-driven SPE, providing an ~80-fold and 2.2-fold reduction in sample and reagent volumes consumed, respectively, as well as an ~5-fold reduction in the overall analysis time in comparison to conventional analysis. Results indicate that the SPE-PCR system can be used for many applications requiring genetic analysis, and the future addition of microchip electrophoresis (ME) to the system would allow for the complete processing of biological samples for forensic STR analysis on a single microdevice."

March 13-18, 2011
- Jenny presented her posters entitled "Amplification of short tandem repeat (STR) regions of the genome for forensic DNA analysis in a plastic microfluidic device" and "The use of polyimide filters for improving infrared-based PCR amplification in microfluidic devices", Jingyi presented his poster entitled "A microscale method for visual and label-free quantitation of DNA, bacterial detection, nucleated cell counting, and more", Yiwen presented her posters entitled "Multiplexed DNA extraction and infrared temperature controlled polymerase chain reaction in disposable polyester-toner chip", and Brian gave a talk entitled "Integrated acoustic cell trapping and polymerase chain reaction: a novel method to detect food-born pathogens" repectively at the PITTCON 2011 in Atlanta, GA.

March 7, 2011
- Kristin's article entitled "An integrated, valveless system for microfluidic purification and reverse transcription-PCR amplification of RNA for detection of infectious agents" is published in this week's issue of Lab on a Chip.
  Abstract: "We describe the first miniaturized device capable of the front-end sample preparation essential for detecting RNA-based infectious agents. The microfluidic device integrates sample purification and reverse transcription PCR (RT-PCR) amplification for the identification and detection of influenza A. The device incorporates a chitosan-based RNA binding phase for the completely aqueous isolation of nucleic acids, avoiding the PCR inhibitory effects of guanidine and isopropanol used in silica-based extraction methods. The purified nucleic acids and the reagents needed for single-step RT-PCR amplification are fluidically mobilized simultaneously to a PCR chamber. Utilizing infrared (IR)-mediated heating allowed for a > 5-fold decrease in RT-PCR analysis time compared to a standard thermal cycling protocol used in a conventional thermal cycler. Influenza A virus [A/PR/8/34 (H1N1)] was used as a simulant in this study for virus-based infectious and biowarfare agents with RNA genomes, and was successfully detected in a mock nasal swab sample at clinically relevant concentrations. Following on-chip purification, a fragment specific to the influenza A nucleoprotein gene was first amplified via RT-PCR amplification using IR-mediated heating to achieve more rapid heating and cooling rates. This was initially accomplished on a two-chip system to optimize the SPE and RT-PCR, and then translated to an integrated SPE-RT-PCR device.
"

March 4, 2011 - Article in Press: "Solid phase extraction of DNA from biological samples in a post-based, high surface area poly(methyl methacrylate) (PMMA) microdevice" - Carmen - Lab on a Chip - doi: 10.1039/C0LC00597E

February 23-26, 2010 - Jenny presented her posters entitled "Expedited enzyme-based preparation of PCR-ready DNA from forensic biological samples on glass and PMMA microdevices" and gave 2 talks "Enzyme-based preparation of PCR-ready DNA from neat semen and semen stains" and "Towards a plastic microdevice for integrated enzyme-based DNA preparation and PCR focusedon forensic STR analysis" at the 63nd American Academy of Forensic Sciences Annual Scientific Meeting in Chicago, IL.




Feb 22, 2011 - Carmen's article entitled "A modular microfluidic system for deoxyribonucleic acid identification by short tandem repeat analysis" is published in this week's issue of Analytica Chimica Acta.

  Abstract: "Microfluidic technology has been utilized in the development of a modular system for DNA identification through STR (short tandem repeat) analysis, reducing the total analysis time from the ∼6 h required with conventional approaches to less than 3h. Results demonstrate the utilization of microfluidic devices for the purification, amplification, separation and detection of 9 loci associated with a commercially-available miniSTR amplification kit commonly used in the forensic community. First, DNA from buccal swabs purified in a microdevice was proven amplifiable for the 9 miniSTR loci via infrared (IR)-mediated PCR (polymerase chain reaction) on a microdevice. Microchip electrophoresis (ME) was then demonstrated as an effective method for the separation and detection of the chip-purified and chip-amplified DNA with results equivalent to those obtained using conventional separation methods on an ABI 310 Genetic Analyzer. The 3-chip system presented here demonstrates development of a modular, microfluidic system for STR analysis, allowing for user-discretion as to how to proceed after each process during the analysis of forensic casework samples."

February 14, 2011
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Congrats to Kerui, Briony, and Yiwen for successfully passing their candidacy exams!

January 2011
- Happy New Year!

December 16, 2010
- Article in Press: "A modular microfluidic system for deoxyrbonucleic acid identification by short tandem repeat analysis" - Carmen and Kristin - Analytica Chimica Acta:doi:10.1016/j.aca.2010.12.016

December 8, 2010
- Advance Article: "An integrated, valveless system for microfluidic purification and reverse transcription-PCR amplification of RNA for detection of infectious agents" - Kristin - Lab on a Chip - doi:10.1039/c0lc00136h.

December 2010
- Welcome to Qian Liu, Dan Nelson and Kyudam Oh, our newest lab members!

November 19, 2010
- Dr. Utz and Dr. Landers have an article entitled "Magnetic Resonance
and Microfluidics" published in the "Perspectives" section in this week's issue of Science.

  Introduction: "Magnetic resonance imaging (MRI) is a well-established clinical tool that is routinely used to locate cartilage or ligament damage, cancerous lesions, and blood vessel occlusions; when combined with magnetic resonance spectroscopy (MRS), it can even map brain function. The image contrast in MRI instruments comes from the change in orientation of the rotational axis (precession) of atomic nuclei in a magnetic field, and can be adjusted to selectively image tissues on the basis of oxygen content, diffusivity, flow velocity, and other properties. Microfluidic “lab-on-a-chip” (LOC) devices represent an emerging technology with potential applications in medical diagnostics. These devices flow samples (which often consist of suspensions of cells) and reagents through miniaturized chemical reactors, and are typically fabricated via lithographic methods similar to those used in microelectronics. Although in principle, MRI should be the ideal tool for monitoring reactions on LOC devices, in practice this turns out to be notoriously difficult because of limitations in sensitivity and resolution. On page 1078 of this issue, Bajaj et al. (1) present an ingenious method that allows sensitive MRI measurements on an LOC device by recording magnetic resonance signals from the spent fluid that exits the device."

October 26, 2010 - Carmen Reedy sucessfully defended her Ph.D. - Dissertation title "DNA Purification on Microfluidic Devices with a Focus on Large Volume, Forensic Biological Samples" Congrats Dr. Reedy!

October 11-13, 2010
- Jenny had her posters entitled "Towards an Integrated, Valveless, Plastic Microdevice for Enzyme-Based DNA Preparation and PCR for Forensic STR Analysis" and "Preparation of High Quality, PCR-Ready DNA from Semen Using an Enzymatic Preparation Method" presented at  the 21st International Symposium on Human Identification in San Antonio, TX.

October 3-7, 2010
- Brian presented his poster entitled "Developments Towards Integrated Acoustic Cell Trapping and PCR", and Carmen and Jenny had their posters entitled "Microfluidic Volume Reduction Solid Phase Extraction of Compromsed and Low DNA Template Forensic Samples" and "Towards an Integrated Microdevice for Enzyme-Based DNA Preparation and PCR Applicable to Forensic DNA Analysis", repectively, presented at the 14th International Micro Total Analysis Systems (uTAS) conference in Groningen, Netherlands.



July 20, 2010
- Kristin Hagan sucessfully defended her Ph.D. - Dissertation titile: "Microfluidic Systems for Sample Preparation with a Focus on RNA Analysis" Congrats Dr. Hagan!

July 15, 2010
- Dan's article entitled "A simple method for the evaluation of microfluidic architecture using flow quantitation via a multiplexed fluidic resisitance measurement" is published in this week's issue of Lab on a Chip.

  Abstract: "Quality control of microdevices adds significant costs, in time and money, to any fabrication process. A simple, rapid quantitative method for the post-fabrication characterization of microchannel architecture using the measurement of flow with volumes relevant to microfluidics is presented. By measuring the mass of a dye solution passed through the device, it circumvents traditional gravimetric and interface-tracking methods that suffer from variable evaporation rates and the increased error associated with smaller volumes. The multiplexed fluidic resistance (MFR) measurement method measures flow via stable visible-wavelength dyes, a standard spectrophotometer and common laboratory glassware. Individual dyes are used as molecular markers of flow for individual channels, and in channel architectures where multiple channels terminate at a common reservoir, spectral deconvolution reveals the individual flow contributions. On-chip, this method was found to maintain accurate flow measurement at lower flow rates than the gravimetric approach. Multiple dyes are shown to allow for independent measurement of multiple flows on the same device simultaneously. We demonstrate that this technique is applicable for measuring the fluidic resistance, which is dependent on channel dimensions, in four fluidically connected channels simultaneously, ultimately determining that one chip was partially collapsed and, therefore, unusable for its intended purpose. This method is thus shown to be widely useful in troubleshooting microfluidic flow characteristics."

July 1, 2010
- Carmen's article entitled "Dual Domain Microchip-Based Process for Volume Reduction Solid Phase Extraction of Nucleic Acids from Dilute, Large Volume Biological Samples" is published in this week's issue of Analytical Chemstry.

  Abstract: "A microfluidic device was developed to carry out integrated volume reduction and purification of nucleic acids from dilute, large volume biological samples commonly encountered in forensic genetic analysis. The dual-phase device seamlessly integrates two orthogonal solid-phase extraction (SPE) processes, a silica solid phase using chaotrope-driven binding and an ion exchange phase using totally aqueous chemistry (chitosan phase), providing the unique capability of removing polymerase chain reaction (PCR) inhibitors used in silica-based extractions (guanidine and isopropanol). Nucleic acids from a large volume sample are shown to undergo a substantial volume reduction on the silica phase, followed by a more stringent extraction on the chitosan phase. The key to interfacing the two steps is mixing of the eluted nucleic acids from the first phase with loading buffer which is facilitated by flow-mediated mixing over a herringbone mixing region in the device. The complete aqueous chemistry associated with the second purification step yields a highly concentrated PCR-ready eluate of nucleic acids devoid of PCR inhibitors that are reagent-based (isopropanol) and sample-based (indigo dye), both of which are shown to be successfully removed using the dual-phase device but not by the traditional microfluidic SPE (μSPE). The utility of the device for purifying DNA was demonstrated with dilute whole blood, dilute semen, a semen stain, and a blood sample inhibited with indigo dye, with the resultant DNA from all shown to be PCR amplifiable. The same samples purified using μSPE were not all PCR amplifiable due to a smaller concentration of the DNA and the lack of PCR-compatible aqueous chemistry in the extraction method. The utility of the device for the purification of RNA was also demonstrated, by the extraction of RNA from a dilute semen sample, with the resulting RNA amplified using reverse transcription (RT)-PCR. The vrSPE-SPE device reliably yields a volume reduction for DNA and RNA purification on the order of 50- and 14-fold, respectively, both compatible with downstream PCR analysis. In addition, purification of all samples consumed less reagents (2.6-fold) than traditional purification methods, with the added advantage of being a “closed system” that eliminates sample transfer steps, thereby reducing the possible entrance points for contaminants."

July 1, 2010
- Ling's article entitled "Molecular Interactions in Surface-Assembled Monolayers of Short Double-Stranded DNA" is published in this week's issue of Langmuir.
 
 Abstract: "We present an experimental study of the energetics of repulsion between end-grafted fragments of double-stranded DNA. The absorption isotherm of thiolated DNA fragments has been measured as a function of DNA chain length as well as the salinity of the surrounding solution. The results are consistent with a simple excluded-volume model of the interaction between neighboring DNA strands."