A 3D Microfluidic ELISA for the Detection of Severe Dengue: Sensitivity Improvement and Vroman Effect Amelioration by EDC–NHS Surface Modification

Serum is commonly used as a specimen in immunoassays but the presence of heterophilic antibodies can potentially interfere with the test results. Previously, we have developed a microfluidic device called: 3D Stack for enzyme-linked immunosorbent assay (ELISA). However, its evaluation was limited to detection from a single protein solution. Here, we investigated the sensitivity of the 3D Stack in detecting a severe dengue biomarker—soluble CD163 (sCD163)—within the serum matrix. To determine potential interactions with serum matrix, a spike-and-recovery assay was performed, using 3D Stacks with and without surface modification by an EDC–NHS (N-ethyl-N′-(3-(dimethylamino)propyl)carbodiimide/N-hydroxysuccinimide) coupling. Without surface modification, a reduced analyte recovery in proportion to serum concentration was observed because of the Vroman effect, which resulted in competitive displacement of coated capture antibodies by serum proteins with stronger binding affinities. However, EDC–NHS coupling prevented antibody desorption and improved the sensitivity. Subsequent comparison of sCD163 detection using a 3D Stack with EDC–NHS coupling and conventional ELISA in dengue patients’ sera revealed a high correlation (R = 0.9298, p < 0.0001) between the two detection platforms. Bland–Altman analysis further revealed insignificant systematic error between the mean differences of the two methods. These data suggest the potentials of the 3D Stack for further development as a detection platform.

FLAUT: A mutual sensitivity improvement through matched pipe, cavity and thin plate resonance

Electrostatic transducers promises a great potential in alternative to piezoelectric transducer based on certain advantages such as inherently wide bandwidth and good acoustic matching to air due to the membrane’s low acoustics impedance. There are two basic designs that are popular among electrostatic ultrasonic transducer developer – rigid backplate and micromachine backplate. This paper presents a methodology for improving the sensitivity of an air-coupled ultrasonic transducer by coupling the resonating thin plate, cavity and pipe in a single cell. The proposed device is termed Fluidically Amplified Ultrasonic Transducer (FLAUT) for an air-coupled application. Investigation of the concept of matched thin plate, cavity and pipe, of which the individual geometry is expected to mutually enhance one another. Analytical modelling is utilized to the matched thin plate, cavity and pipe. The analytical modelling identifies the required geometry for the FLAUT based on the matched operating resonant frequency of 25 kHz. At the end of the paper the prototype of FLAUT is presented where the device was fabricated using additive manufacturing process (3-D printing) which consist of a 50 µm Kapton thin film over a micro stereolithography designed backplate. Here aluminum is coated as the electrode utilizing the thermal evaporation process for both the Kapton film and the backplate. A laser interferometer is utilized to measure FLAUT thin plate displacement which indicates the device is running at 25 kHz fundamental mode. A 30 dB difference is also observed between the deformation velocity of the cavity active region and its surrounding.

Theoretical Analysis of Tuning and Sensitivity Improvement of Surface Plasmon Resonance Biosensor employing Heterostructures of Titanium Disilicide and Graphene

In this work, a surface plasmons resonance-based biosensor is theoretically and mathematically investigated. The proposed sensor is a multilayered structure of the titanium disilicide and graphene along with Ag metal. These layers are stacked over the BK7 prism. The metal, titanium disilicide, and graphene layer thickness are taken as 45 nm, 2 nm, and 1.7 nm, respectively. The titanium disilicide is an air-stable 2-D material. The performance of the biosensor is analyzed using the attenuated total reflection (ATR) method. The proposed configuration has a maximum sensitivity of 183.4°/RIU, 47.45 % higher than the conventional sensor. The designed sensor has wide applications in chemical, medical, and biological analyte sensing.

Metformin Increases Protein Phosphatase 2A Activity in Primary Human Skeletal Muscle Cells Derived from Lean Healthy Participants

Context. Skeletal muscle insulin resistance is one of the primary contributors of type 2 diabetes (T2D). Metformin is the first-line drug for the treatment of T2D. The primary effects of metformin include decreasing glucose production in the liver and decreasing insulin resistance in the skeletal muscle. However, the molecular mechanism of metformin’s action in skeletal muscle is not well understood. Protein phosphatase 2A (PP2A), a major serine/threonine protein phosphatase, plays a pivotal role in cellular processes, such as signal transduction, cell proliferation, and apoptosis, and acts through dephosphorylating key signaling molecules such as AKT and AMPK. However, whether PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells remains to be elucidated. Objective. To investigate if PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells. Participants. Eight lean insulin-sensitive nondiabetic participants (4 females and 4 males; age: 21.0 ± 1.0 years; BMI: 22.0 ± 0.7 kg / m 2 ; 2-hour OGTT: 97.0 ± 6.0 mg / dl ; HbA1c: 5.3 ± 0.1 % ; fasting plasma glucose: 87.0 ± 2.0 mg / dl ; M value; 11.0 ± 1.0 mg / kgBW / min ). Design. A hyperinsulinemic-euglycemic clamp was performed to assess insulin sensitivity in human subjects, and skeletal muscle biopsy samples were obtained. Primary human skeletal muscle cells (shown to retain metabolic characteristics of donors) were cultured from these muscle biopsies that included 8 lean insulin-sensitive participants. Cultured cells were expanded, differentiated into myotubes, and treated with 50 μM metformin for 24 hours before harvesting. PP2Ac activity was measured by a phosphatase activity assay kit (Millipore) according to the manufacturer’s protocol. Results. The results indicated that metformin significantly increased the activity of PP2A in the myotubes for all 8 lean insulin-sensitive nondiabetic participants, and the average fold increase is 1.54 ± 0.11 ( P < 0.001 ). Conclusions. These results provided the first evidence that metformin can activate PP2A in human skeletal muscle cells derived from lean healthy insulin-sensitive participants and may help to understand metformin’s action in skeletal muscle in humans.

Tuning and Sensitivity Improvement of Bi-metallic Structure-based Surface Plasmon Resonance Biosensor with 2-D ξ-Tin Selenide nanosheets

This manuscript aims to visualize the effect of tin selenide (SnSe) on the sensing application of the SPR biosensors. Tin selenide is the 2-Dimensional material transition metal dichalcogenide family element. By utilizing the extraordinary properties of the SnSe, high sensitivity and high performance of the biosensor is analyzed by utilizing the extraordinary properties of the SnSe. A unique two-dimensional substantial heterostructure, \({\epsilon }\)-tin selenide (SnSe) /graphene layer has been deposited over the metal surface to improve the sensitivity; moreover, the sensitivity is limited to a certain extent. The \({\epsilon }-\text{S}\text{n}\text{S}\text{e}\) nanosheet is placed in between two layers of gold (Au) in the Kretschmann arrangement. The proposed configuration has a maximum sensitivity of 214°/RIU, which is 93.81% higher than the conventional sensor. The performance parameters like FWHM, detection accuracy and quality factor have been analysed. The \({\epsilon }-\text{S}\text{n}\text{S}\text{e}\) material is an air-stable 2-D nanosheet and has application in chemical, medical, and biological sensors.

Pressure Sensitivity Improvement of Fiber Bragg Grating Sensor Using Cytop Fiber

Recent demand for using FBG as a pressure sensor in a different industrial application makes several types of research to be conducted to enhance the pressure sensitivity. This paper demonstrates a combination method to enhance pressure sensitivity. Firstly, in this work FBG with polymer fiber named perfluorinated monomer (CYTOP) was used with specific parameters. Secondly, this FBG was covered by a patch of thin polymer material. However, the strain, temperature, and pressure sensitivity were recorded and compared with bare silica FBG. The temperature effect was reduced by using the cascade FBG technique. By applying force on the grating and changing of refractive index; the Bragg wavelength was shifting, making the CYTOP FBG responds more efficiently than silica FBG. This responsivity was leading to an improvement in pressure sensitivity. Experimental results illustrate that the enhanced CYTOP FBG based pressure sensor achieves pressure sensitivity up to 93.5 pm/KPs with a resolution of 0.005 KPa, which was 1500 times higher than bare FBG. The advanced CYTOP FBG based pressure sensor can be functionalized in a technical application for instance, structural health monitoring, pressure of oil wells application, explosion wave, and prevention of erosion.