33 research outputs found
Molecular Detection of Invasive Species in Heterogeneous Mixtures Using a Microfluidic Carbon Nanotube Platform
Screening methods to prevent introductions of invasive species are critical for the protection of environmental and economic benefits provided by native species and uninvaded ecosystems. Coastal ecosystems worldwide remain vulnerable to damage from aquatic species introductions, particularly via ballast water discharge from ships. Because current ballast management practices are not completely effective, rapid and sensitive screening methods are needed for on-site testing of ships in transit. Here, we describe a detection technology based on a microfluidic chip containing DNA oligonucleotide functionalized carbon nanotubes. We demonstrate the efficacy of the chip using three ballast-transported species either established (Dreissena bugensis) or of potential threat (Eriocheir sinensis and Limnoperna fortuneii) to the Laurentian Great Lakes. With further refinement for on-board application, the technology could lead to real-time ballast water screening to improve ship-specific management and control decisions
Slowing down DNA translocation through solid-state nanopores by edge-field leakage
Solid-state nanopores can serve as single molecule sensors for DNA sequencing, but the current designs suffer from fast DNA translocation so low detectivity. Wang et al. slow down and control the translocation speed by 5 orders of magnitude using a leakage field generated at the nanopore tip
Extracellular biosynthesis of monodisperse gold nanoparticles by a novel extremophilic actinomycete, Thermomonospora sp.
This article does not have an abstract
Nano-cone optical fiber array sensors for miRNA profiling
Up/down regulation of microRNA panels has been correlated to cardiovascular diseases and cancer. Frequent miRNA profiling at home can hence allow early cancer diagnosis and home-use chronic disease monitoring, thus reducing both mortality rate and healthcare cost. However, lifetime of miRNAs is less than 1 hour without preservation and their concentrations range from pM to mM. Despite rapid progress in the last decade, modern nucleic acid analysis methods still do not allow personalized miRNA profiling - Real-time PCR and DNA micro-array both require elaborate miRNA preservation steps and expensive equipment and nano pore sensors cannot selectively quantify a large panel with a large dynamic range. We report a novel and low-cost optical fiber sensing platform, which has the potential to profile a panel of miRNA with simple LED light sources and detectors. The individual tips of an optical imaging fiber bundle (mm in diameter with 7000 fiber cores) were etched into cones with 10 nm radius of curvature and coated with Au. FRET (Forster Resonant Energy Transfer) hairpin oligo probes, with the loop complementary to a specific miRNA that can release the hairpin, were functionalized onto the conic tips. Exciting light in the optical fiber waveguide is optimally coupled to surface plasmonics on the gold surface, which then converges to the conic tips with two orders of magnitude enhancement in intensity. Unlike nanoparticle plasmonics, tip plasmonics can be excited over a large band width and hence the plasmonic enhanced fluorescence signal of the FRET reporter is also focused towards the tip - and is further enhanced with the periodic resonant grid of the fiber array which gives rise to pronounced standing wave interference patterns. Multiplexing is realized by functionalizing different probes onto one fiber bundle using a photoactivation process
Extracellular biosynthesis of bimetallic Au-Ag alloy nanoparticles
The exposure of a mixture of 1 mM HAuCl4 and 1 mM AgNO3 solutions to different amounts of fungal biomass (Fusarium oxysporum) results in the formation of highly stable Au-Ag alloy nanoparticles with dimensions of 8-14 nm depending on metal molar fraction. The amount of cofactor NADH released by the F. oxysporum fungus plays an important role in controlling the composition of the alloy nanoparticles
Charge Inversion, Water Splitting, and Vortex Suppression Due to DNA Sorption on Ion-Selective Membranes and Their Ion-Current Signatures
The physisorption of negatively charged
single-stranded DNA (ssDNA)
of different lengths onto the surface of anion-exchange membranes
is sensitively shown to alter the anion flux through the membrane.
At low surface concentrations, the physisorbed DNAs act to suppress
an electroconvection vortex instability that drives the anion flux
into the membrane and hence reduce the overlimiting current through
the membrane. Beyond a critical surface concentration, determined
by the total number of phosphate charges on the DNA, the DNA layer
becomes a cation-selective membrane, and the combined bipolar membrane
has a lower net ion flux, at low voltages, than the original membrane
as a result of ion depletion at the junction between the cation- (DNA)
and anion-selective membranes. However, beyond a critical voltage
that is dependent on the ssDNA coverage, water splitting occurs at
the junction to produce a larger overlimiting current than that of
the original membrane. These two large opposite effects of polyelectrolyte
counterion sorption onto membrane surfaces may be used to eliminate
limiting current constraints of ion-selective membranes for liquid
fuel cells, dialysis, and desalination as well as to suggest a new
low-cost membrane surface assay that can detect and quantify the number
of large biomolecules captured by probes functionalized on the membrane
surface
Charge Inversion, Water Splitting, and Vortex Suppression Due to DNA Sorption on Ion-Selective Membranes and Their Ion-Current Signatures
The physisorption of negatively charged
single-stranded DNA (ssDNA)
of different lengths onto the surface of anion-exchange membranes
is sensitively shown to alter the anion flux through the membrane.
At low surface concentrations, the physisorbed DNAs act to suppress
an electroconvection vortex instability that drives the anion flux
into the membrane and hence reduce the overlimiting current through
the membrane. Beyond a critical surface concentration, determined
by the total number of phosphate charges on the DNA, the DNA layer
becomes a cation-selective membrane, and the combined bipolar membrane
has a lower net ion flux, at low voltages, than the original membrane
as a result of ion depletion at the junction between the cation- (DNA)
and anion-selective membranes. However, beyond a critical voltage
that is dependent on the ssDNA coverage, water splitting occurs at
the junction to produce a larger overlimiting current than that of
the original membrane. These two large opposite effects of polyelectrolyte
counterion sorption onto membrane surfaces may be used to eliminate
limiting current constraints of ion-selective membranes for liquid
fuel cells, dialysis, and desalination as well as to suggest a new
low-cost membrane surface assay that can detect and quantify the number
of large biomolecules captured by probes functionalized on the membrane
surface