Synthesis of Poly(ϵ-caprolactone) Microreactors from Freeze-Dried Microspheres

Poly(ϵ-caprolactone) microreactors were prepared by micro-volcanic rupture of freeze dried microspheres. Effects of three synthesis parameters viz polymer concentration, emulsifier concentration and stirring speed on size and morphology of microreactors were examined. Average diameter of microreactors showed substantial increase with increasing polymer concentration and reduced size with increasing polyvinyl alcohol (emulsifier) concentration and stirring speed, respectively. These miniaturised structures have potential applications in immunodiagnosis and drug delivery

Molybdenum disulfide quantum dot based highly sensitive impedimetric immunoassay for prostate specific antigen

This work reports on the synthesis of molybdenum disulfide quantum dots (MoS2-QDs) from pre-exfoliated MoS2 nanosheets. After a thorough characterization, the MoS2-QDs were assembled onto screen-printed carbon electrodes, followed by the physical adsorption of antibodies against the prostate-specific antigen (PSA) to form a bioelectrode. Because of the hydrophobic nature of the QDs, they are favorable for the hydrophobic interaction with the antibodies. Based on cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, the bioelectrode was employed for the detection of PSA using hexacyanoferrate as the redox probe. The electrode yielded an optimum CV response of PSA in the range of 0.1 pg·mL−1 to 10 ng·mL−1 (scan rate: 0.05 mVs−1). The performance improved significantly when EIS was applied (response range: 0.01 pg·mL−1 to 200 ng·mL−1; limit of detection: 0.01 pg·mL−1). The feasibility of the immunoassay was demonstrated by successfully analyzing PSA in serum samples based on the standard addition method. A near 100% recovery of PSA from the serum samples supports the possible practical viability of the procedure. The immunoassay highlights a number of advantageous features such as convenient attachment of antibodies over the electrode surface and broad range of PSA detection with the successful demonstration with real serum samples

Synthesis and Characterization of Silica-Coated Silver Nanoprobe for Paraoxon pesticide Detection

Metal enhanced fluorescence assay-based sensitive detection of a neurotoxic organophosphates pesticide, Paraoxon, is reported. The experimental approach involves the bio-interfacing of organophosphorus hydrolase with a high quantum yield fluorophore, pyranine (8-hydroxyl pyrene-1,3,6-trisulfonic acid trisodium salt), followed by the conjugation of the OPH-pyranine derivative with silica-coated silver nanoparticles (Ag NPs). The above bio-nanoprobe was used for the analysis of the organophosphate pesticide, wherein the induced hydrolysis of the pesticide cause the decrease in pH in the vicinity. An excitation light of 460 nm wavelength was used to monitor the changes in the resulting emission (at 510 nm) with respect to the changing pesticide concentrations (1–100 ppb). The introduction of the silica-coated AgNPs into the nanoprobe system was observed to deliver metal enhanced effect, leading to almost10-fold intensification of the fluorescence signal. The enhanced fluorescence assay format offers linear detection of Paraoxon in the concentration range of 1–100 ng mL−1 with the limit of detection 1 ng mL−1 (1 ppb)

Formation of High-Purity Indium Oxide Nanoparticles and Their Application to Sensitive Detection of Ammonia

High-purity In2O3 nanoparticles were recovered from scrap indium tin oxide substrates in a stepwise process involving acidic leaching, liquid-liquid extraction with a phosphine oxide extractant, and combustion of the organic phase. The morphological and structural parameters of the recovered nanoparticles were investigated to support the formation of the desired products. These In2O3 nanoparticles were used for sensitive sensing of ammonia gas using a four-probe electrode device. The proposed sensor offered very quick response time (around 10 s) and highly sensitive detection of ammonia (at a detection limit of 1 ppm)

Low-cost goldleaf electrode as a platform for Escherichia coli immunodetection

<p>Gold electrodes are one of most prevalent substrates in electrochemical biosensors because they can be easily and highly efficiently functionalized with thiolated biomolecules. However, conventional methods to fabricate gold electrodes are costly, time-consuming and require onerous equipment. Here, an affordable method for rapid fabrication of an electrochemical immunosensor for Escherichia coli detection is presented. The gold electrode was generated using 24-karat gold leaves and lowcost polyvinyl chloride adhesive sheets covered with an insulating PTFE layer. The goldleaf electrode (GLE) was patterned using laser ablation and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electronic microscopy, contact angle and 3D profiling. The GLEs were modified by a self-assembled mercaptopropionic monolayer, followed by surface activation to allow binding of the specific anti-E. coli antibody via carbodiimide linking. The biosensor showed a detection limit of 2 CFU/mL and a linear dynamic range of 10-10<sup>7</sup> CFU/mL for E. coli cells. No false positive signals were obtained from control bacteria. The obtained results demonstrated suitability of GLE for use in biosensors with high reliability and reproducibility. It is foreseeable that our work will inspire design of point-of-need biosensors broadly applicable in low-resource settings.</p&gt