Papers by Keyword: Biosensing

Abstract: The rapid progress of nanotechnology has created new avenues for the development of innovation in medical and biological devices. Transition metal dichalcogenides (TMDs) nanostructures such as tungsten disulfide nanodiscs (WS₂-NDs) decorated with metallic nanoparticles, provide promising novel materials for surface Enhanced Raman Spectroscopy (SERS). This work focuses on the design and fabrication of a new SERS substrate based on AuNPs/WS₂-NDs hybrid system, which exhibits a strong localized surface plasmonic resonance (LSPR) and achieves up to an order of magnitude enhancement in Raman spectra intensity compared to WS₂-NDs only. This superior performance is attributed to the improved electromagnetic mechanism (EM) on the metallic gold nanoparticles and on the nonmetallic TMDs nanostructures. The chemical mechanism (CM), which facilitates charge transfer between analyte molecules and WS₂-NDs, allows for further improvement of Raman spectra on SERS on tungsten disulfide nanodiscs.

Abstract: The demand for flexible and wearable electrochemical sensors has surged due to their low cost and portability. This study produces and characterizes low-cost and environmentally friendly flexible laser engraved graphene/Cu nanoparticles composite materials as a potential electrode for electronic applications. The electrode is fabricated by directly engraving Polyimide substrate using a CO₂ laser machine to produce Laser Engraved Graphene (LEG). The electrode is then modified with copper nanoparticles via a one-step pulse electrodeposition technique to be characterized structurally, mechanically, and electrochemically using SEM, XRD, bending test, electrochemical impedance spectroscopy, and cyclic voltammetry to assess their stability and electrocatalytic activity. The laser irradiation of PI results in 3D porous graphene structure formation that increases electron transfer rate and the electrochemically active surface area. Copper deposition improves the sensitivity of LEG by its high conductivity.

Abstract: Aggregation-Induced Emission (AIE) has gone through a rapid development since it’s discovery back in 2001. It is a famous research topic as it shows many advantages compared with traditional fluorescent material struggling with the issue of Aggregation-caused quenching (ACQ), since it only emits fluorescence when gathered. AIE material can provide better sensitivity, better photobleaching resistance and SNR compared with traditional material. AIE material can be applied in the fields of biosensing and bioimaging to replace traditional material with a better performance. This article describes the concept and structure of AIE material, shows types of the material with examples, also introduces the application of AIE material in photodynamic therapy, this article talks about the concept, usage, advantages and drawbacks of applying material with AIE characteristics in photodynamic therapy.

Abstract: In this work, we use photolithography in order to fabricate micro-grating structures on silicon. The first step of device was coated by 3.5 μm thick silicon dioxide (SiO₂) film on top side, whereas the bottom side was coated with 4.5 μm. Next, we deposited silicon nitride (Si₃N₄) film of 2 μm by plasma-enhanced chemical vapor deposition, and used photolithography to prepare the gratings. We compared micro-grating period sizes of 1 μm, 0.8 μm and 0.5 μm, and found the 0.5 μm gave the best sensitivity. These devices can be applied with detection in biosensing in the future.

Abstract: In order to fabricate biosensors with high sensitivity, the diatom Coscinodiscus excentricus was cultured on a microfluidic chip made with polydimethylsiloxane (PDMS), then the organic matter of diatom cells was removed and only diatom frustules were left, after which the cleaned frustules were bonded onto the bottom of the PDMS micro chamber by ultraviolet irradiation. The overview and the detailed morphology of the frustules in the chamber were analyzed by SEM, and the ultraviolet irradiation bonding mechanism of diatom with PDMS was discussed. Finally, the diatom based microfluidic chip was tested with the fluorescein-labeled protein; and the result showed that the fluorescence intensity of the diatom is 4 times stronger compared with that of the blank regions.

Abstract: Nanopore and nanopore based biosensing and DNA sequencing have attracted more and more interests in the past ten years. In this paper, a simplified model is addressed to depict biomolecules passing through ultrafiltration membrane (containing nanopores). Based on this model, the passing velocity of biomolecules will not increase continuously but first increase, then decrease and stabilize with the IgG concentration increasing. Due to the physical place-holding effects and the simulation results, it can be predicted that, with biomolecules concentration increasing, the ionic current will first decrease, then increase and finnally stabilize. These predictions based on the simulation match our experimental results well.

Abstract: Localized surface plasmon resonance (LSPR) based sensors are a well established technology utilized for label-free biochemical sensing in immunoassay, medical diagnostics and environmental monitoring. The understanding of asymmetric metal nanoparticles, new object for complex, coupled plasmon systems providing localized significantly enhanced E-field, is central to a wide range of novel applications and processes in science of higher sensitive sensing systems. However, few methods are available for actual characterization of such nanostructures at the single particle level. Here we propose a precise and large sized scale fabrication technique for asymmetric nanoshells array with nanogaps of several tens of nanometers for LSPR sensor through atmospheric pressure plasma etching processes. A nanoshell was simply constructed by laminating thin Au films on periodic isolated polymer nanoparticles template. This nanoshells array was expected to exhibit specific near-infrared plasmonic properties. When measuring the sensitivity, nanoshells array exhibited a high sensitivity to changes of surrounding refractive index and showed a higher sensor figure of merit than the alternative structures. This indicated that the enhanced plasmon E-field in the asymmetric nanostructures improved sensor performance. Our fabrication technique and the optical properties of the arrays will provide useful information for developing new plasmonic applications.

Abstract: We observed the glucose concentration of solutions using a near-field microwave microprobe (NFMM). Instead of the usual invasive technique, we take the advantage of the noncontact and noninvasive evaluation capabilities of an NFMM. The NFMM with a high Q dielectric resonator allows observation of small variations of the permittivity due to changes in the glucose concentration. By measuring the reflection coefficient we could observe the concentration of glucose with a detectable resolution to 0.5 mg/ml (0.05 %). The glucose biosensor using a NFMM provides an unique approach for glucose monitoring for diabetes.

Abstract: Using ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were formed in the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). Efficient electroluminescence was obtained for the wavelength range from UV to infrared with a transparent top electrode made of indium-tin oxide. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies distinctly above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Finally, application aspects to the field of biosensing will be shown.

Abstract: Here, a two-dimensional microarray of ten thousand (100x100) hepatocyte hetero-spheroids, underlaid with endothelial cells, was successfully constructed with a 100 µm spacing in an active area of 20x20 mm on micro-fabricated glass substrates coated with poly(ethylene glycol) (PEG) brushes (Fig. 1). Co-cultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver-specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100 µm, functioning as a miniaturized liver to secret albumin for at least three weeks. The spheroid array constructed here is highly useful as a platform of TBB and CBB to detect a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.