Rapid and quantitative detection of SARS-CoV-2 specific IgG for convalescent serum evaluation.

Convalescent serum with a high abundance of neutralization IgG is a promising therapeutic agent for rescuing COVID-19 patients in the critical stage. Knowing the concentration of SARS-CoV-2 S1-specific IgG is crucial in selecting appropriate convalescent serum donors. Here, we present a portable microfluidic ELISA technology for rapid (15 min), quantitative, and sensitive detection of anti-SARS-CoV-2 S1 IgG in human serum with only 8 μL sample volume.

Rapid and sensitive detection of drugs of abuse in sweat by multiplexed capillary based immuno-biosensors.

Rapid and sensitive detection of drugs of abuse plays an important role in monitoring of drug use and treatment compliance. Sweat based drug analysis shows great advantages due to its non-invasive nature. However, most of the related methods developed to date are qualitative, slow, or costly, which significantly hinders their application in field use.

Multiparameter urine analysis for quantitative bladder cancer surveillance of orthotopic xenografted mice.

The human-derived orthotopic xenograft mouse model is an effective platform for performing in vivo bladder cancer studies to examine tumor development, metastasis, and therapeutic effects of drugs. To date, the surveillance of tumor progression in real time for orthotopic bladder xenografts is highly dependent on semi-quantitative in vivo imaging technologies such as bioluminescence. While these imaging technologies can estimate tumor progression, they are burdened with requirements such as anesthetics, specialized equipment, and genetic modification of the injected cell line.

Rapid Mouse Follicle Stimulating Hormone Quantification and Estrus Cycle Analysis Using an Automated Microfluidic Chemiluminescent ELISA System.

Follicle stimulating hormone (FSH) plays a critical role in female reproductive development and homeostasis. The blood/serum concentration of FSH is an important marker for reporting multiple endocrinal functions. The standardized method for mouse FSH (mFSH) quantification based on radioimmunoassay (RIA) suffers from long assay time (∼2 days), relatively low sensitivity, larger sample volume (60 μL), and small dynamic range (2-60 ng/mL); thus, it is insufficient for monitoring fast developing events with relatively small mFSH fluctuations (e.

Glass capillary based microfluidic ELISA for rapid diagnostics.

Enzyme-linked immunosorbent assay (ELISA) is widely used in medical diagnostics and fundamental biological research due to its high specificity and reproducibility. However, the traditional 96-well-plate based ELISA still suffers from several notable drawbacks, such as long assay time (4-6 hours), burdensome procedures and large sample/reagent volumes (∼100 μl), which significantly limit traditional ELISA's applications in rapid clinical diagnosis and quasi-real-time prognosis of some fast-developing diseases. Here, we developed a user friendly glass capillary array based microfluidic ELISA device.

Sensitive sulfide ion detection by optofluidic catalytic laser using horseradish peroxidase (HRP) enzyme.

We report an optofluidic catalytic laser for sensitive sulfide ion detection. In the catalytic reaction, horseradish peroxidase (HRP) enzyme is used for catalyzing the non-fluorescent substrate, 10-Acetyl-3,7-dihydroxyphenox-azine (ADHP), to produce highly fluorescent resorufin, which was used as gain medium for lasing. Using sulfide ions as inhibitors, the catalytic reaction slows down, resulting in a delay in the lasing onset time, which is used as the sensing signal.

Optofluidic laser for dual-mode sensitive biomolecular detection with a large dynamic range.

Enzyme-linked immunosorbent assay (ELISA) is a powerful method for biomolecular analysis. The traditional ELISA employing light intensity as the sensing signal often encounters large background arising from non-specific bindings, material autofluorescence and leakage of excitation light, which deteriorates its detection limit and dynamic range. Here we develop the optofluidic laser-based ELISA, where ELISA occurs inside a laser cavity.

Adaptive two-dimensional microgas chromatography.

We proposed and investigated a novel adaptive two-dimensional (2-D) microgas chromatography system, which consists of one 1st-dimensional column, multiple parallel 2nd-dimensional columns, and a decision-making module. The decision-making module, installed between the 1st- and 2nd-dimensional columns, normally comprises an on-column nondestructive vapor detector, a flow routing system, and a computer that monitors the detection signal from the detector and sends out the trigger signal to the flow routing system. During the operation, effluents from the 1st-dimensional column are first detected by the detector and, then, depending on the signal generated by the detector, routed to one of the 2nd-dimensional columns sequentially for further separation.

Ultrasensitive vapor detection with surface-enhanced Raman scattering-active gold nanoparticle immobilized flow-through multihole capillaries.

We developed novel flow-through surface-enhanced Raman scattering (SERS) platforms using gold nanoparticle (Au-NP) immobilized multihole capillaries for rapid and sensitive vapor detection. The multihole capillaries consisting of thousands of micrometer-sized flow-through channels provide many unique characteristics for vapor detection. Most importantly, its three-dimensional SERS-active micro-/nanostructures make available multilayered assembly of Au-NPs, which greatly increase SERS-active surface area within a focal volume of excitation and collection, thus improving the detection sensitivity.

Gold nanoparticle-enhanced and size-dependent generation of reactive oxygen species from protoporphyrin IX.

Photosensitizer, protoporphyrin IX (PpIX), was conjugated with Au nanoparticles (Au NPs) of 19, 66, and 106 nm diameter to study the size-dependent enhancement of reactive oxygen species (ROS) formation enabled by Au NPs. The ROS enhancement ratio is determined to be 1:2.56:4.

Rapid, sensitive, and multiplexed on-chip optical sensors for micro-gas chromatography.

We developed and characterized a rapid, sensitive and integrated optical vapor sensor array for micro-gas chromatography (μGC) applications. The sensor is based on the Fabry-Pérot (FP) interferometer formed by a micrometre-thin vapor-sensitive polymer layer coated on a silicon wafer. The thickness and the refractive index of the polymer vary in response to the vapor analyte, resulting in a change in the reflected intensity of the laser impinged on the sensor.

Ultrasensitive optofluidic surface-enhanced Raman scattering detection with flow-through multihole capillaries.

3-Dimensional surface-enhanced Raman scattering (SERS) detection integrated with optofluidics offers many advantages over conventional SERS conducted under planar and static conditions. In this paper, we developed a novel optofluidic SERS platform based on nanoparticle-functionalized flow-through multihole capillaries for rapid, reliable, and ultrasensitive analyte detection. The unique configuration not only provides 3-dimensional geometry for significantly increased SERS-active area and inherent fluidic channels for rapid and efficient sample delivery, but also confines and transmits light along the capillary for large SERS signal accumulation.

Rapid, sensitive DNT vapor detection with UV-assisted photo-chemically synthesized gold nanoparticle SERS substrates.

We report rapid, sensitive, and direct detection of 2,4-dinitrotoluene (DNT) vapor using tailored gold nanoparticles (Au-NPs) as the SERS substrate. The Au-NPs were synthesized using the UV-assisted photo-chemical reduction method and subsequently formed a monolayer on the glass slide through polymer-mediated self-assembly. The SERS substrate such prepared has high SERS enhancement, high affinity towards DNT vapor, and rapid response to the DNT adsorption/desorption.

Robust silica-coated quantum dot-molecular beacon for highly sensitive DNA detection.

We synthesized and characterized small yet highly robust silica-coated quantum dots (QDs) and then used them to develop highly sensitive molecular beacon (MB) for DNA detection. As compared to the previously reported methods, our silica coating approach enabled simple and rapid synthesis of silica-coated QDs in large quantities and high concentrations with a well-controlled silica layer. The QDs such made were stable and had a high quantum yield in a wide range of pH values (1-14) and high salt concentrations (up to 2 M).

Highly sensitive multiplexed heavy metal detection using quantum-dot-labeled DNAzymes.

We developed highly sensitive and specific nanosensors based on quantum dots (QDs) and DNAzyme for multiplexed detection of heavy metal ions in liquid. The QDs were coated with a thin silica layer for increased stability and higher quantum yield while maintaining a relatively small size for highly efficient energy transfer. The QD-DNAzyme nanosensors were constructed by conjugating quencher-labeled DNAzymes onto the surface of carboxyl-silanized QDs.

Structure fits the purpose: photonic crystal fibers for evanescent-field surface-enhanced Raman spectroscopy.

We report numerical simulation and hyperspectral Raman imaging of three index-guiding solid-core photonic crystal fibers (PCFs) of different air-cladding microstructures to assess their respective potential for evanescent-field Raman spectroscopy, with an emphasis on achieving surface-enhanced Raman scattering (SERS) over the entire fiber length. Suspended-core PCF consisting of a silica core surrounded by three large air channels conjoined by a thin silica web is the most robust of the three SERS-active PCFs, with a demonstrated detection sensitivity of 1x10(-10) M R6G in an aqueous solution of only approximately 7.3 microL sampling volume.

Forward-propagating surface-enhanced Raman scattering and intensity distribution in photonic crystal fiber with immobilized Ag nanoparticles.

A 30 cm long solid-core photonic crystal fiber (PCF) with immobilized and discrete Ag nanoparticles was used to obtain forward-propagating surface-enhanced Raman scattering (SERS) of 2 microM Rhodamine 6G (R6G) aqueous solution filled in the cladding air channels. The intensity distributions of characteristic Raman vibrational bands of silica and R6G in PCF were mapped for the first time to our knowledge by hyperspectral Raman imaging. We show that the measured SERS intensity arises exclusively from the forward-propagating core mode as a result of evanescent-field interaction with R6G in the innermost ring of the cladding air channels.

5-aminolevulinic acid-conjugated gold nanoparticles for photodynamic therapy of cancer.

Background: Effective delivery of photosensitizer to target tumor cells that causes minimal damage to healthy cells is an important requirement in photodynamic therapy of cancer.

Aim: We aimed to use biocompatible gold nanoparticles as a vehicle to deliver 5-aminolevulinic (5-ALA) acid for selective and efficient photodynamic therapy.

Results: Protoporphyrin IX accumulated preferentially in fibrosarcoma tumor cells treated with 5-ALA-conjugated nanoparticles while yielding significantly higher reactive oxygen species compared with that with 5-ALA.