Fabrication of 3D Polycaprolactone Macrostructures by 3D Electrospinning.

Building 3D electrospun macrostructures and monitoring the biological activities inside them are challenging. In this study, 3D fibrous polycaprolactone (PCL) macrostructures were successfully fabricated using in-house 3D electrospinning. The main factors supporting the 3D self-assembled nanofiber fabrication are the H3PO4 additives, flow rate, and initial distance. The effects of solution concentration, solvent, H3PO4 concentration, flow rate, initial distance, voltage, and nozzle speed on the 3D macrostructures were examined. The optimal conditions of 4 mL/h flow rate, 4 cm initial nozzle-collector distance, 14 kV voltage, and 1 mm/s nozzle speed provided a rapid buildup of cylinder macrostructures with 6 cm of diameter, reaching a final height of 16.18 ± 2.58 mm and a wall thickness of 3.98 ± 1.01 mm on one perimeter with uniform diameter across different sections (1.40 ± 1.10 µm average). Oxygen plasma treatment with 30-50 W for 5 min significantly improved the hydrophilicity of the PCL macrostructures, proving a suitable scaffold for in vitro cell cultures. Additionally, 3D images obtained by synchrotron radiation X-ray tomographic microscopy (SRXTM) presented cell penetration and cell growth within the scaffolds. This breakthrough in 3D electrospinning surpasses current scaffold fabrication limitations, opening new possibilities in various fields.

Enhancing Glucose Biosensing with Graphene Oxide and Ferrocene-Modified Linear Poly(ethylenimine).

We designed and optimized a glucose biosensor system based on a screen-printed electrode modified with the NAD-GDH enzyme. To enhance the electroactive surface area and improve the electron transfer efficiency, we introduced graphene oxide (GO) and ferrocene-modified linear poly(ethylenimine) (LPEI-Fc) onto the biosensor surface. This strategic modification exploits the electrostatic interaction between graphene oxide, which possesses a negative charge, and LPEI-Fc, which is positively charged. This interaction results in increased catalytic current during glucose oxidation and helps improve the overall glucose detection sensitivity by amperometry. We integrated the developed glucose sensor into a flow injection (FI) system. This integration facilitates a swift and reproducible detection of glucose, and it also mitigates the risk of contamination during the analyses. The incorporation of an FI system improves the efficiency of the biosensor, ensuring precise and reliable results in a short time. The proposed sensor was operated at a constant applied potential of 0.35 V. After optimizing the system, a linear calibration curve was obtained for the concentration range of 1.0-40 mM (R2 = 0.986). The FI system was successfully applied to determine the glucose content of a commercial sports drink.

A facile method for generating polypyrrole microcapsules and their application in electrochemical sensing.

A facile and rapid strategy to generate polypyrrole microcapsules is reported. The strategy is compatible with a vortex mixer and with a microfluidic chip for droplet generation, allowing a > 100-fold reduction in particle size. The sub-micron particle sizes obtained can also be tuned to some extent based on the chip geometry. The capsules can be kept stably in solution and can be transferred onto electrochemical devices. As an application example, we casted the polypyrrole capsules generated onto screen-printed electrodes, leading to a significant increase in their electroactive surface area and capacitance. The electrodes were further modified with glucose dehydrogenase (GDH) to fabricate glucose biosensors. The introduction of polypyrrole microcapsules increased the dynamic range of the glucose sensor to ca. 300% compared with that of the electrode without polypyrrole microcapsules. The resulting glucose sensor is operated at a constant applied potential of 0.20 V vs. Ag/AgCl (3 M KCl) in an air-equilibrated electrolyte. At this potential, the sensor showed a linear range from 1.0 to 9.0 mM glucose with a sensitivity of 3.23 µA cm-2 mM-1 (R2 = 0.993). The limit of detection obtained was 0.09 mM, and the reproducibility was 3.6%. The method allows generating polypyrrole microcapsules without surfactants or organic solvents and may enable new opportunities in the design of biosensors, electronic devices, and molecular delivery.

An Operando X-ray Absorption Spectroscopy Study on Sensing Characteristics of Vertically Aligned ZnO Thin Film for Methane Gas Sensors.

In this work, a simple, facile growth approach for a vertically aligned ZnO thin film is fabricated and its application towards methane gas sensors is demonstrated. ZnO thin film was prepared by a combination of hydrothermal and sputtering methods. First, a ZnO seed layer was prepared on the substrate through a sputtering technique, then a ZnO nanorod was fabricated using a hydrothermal method. The surface morphology of the ZnO film was observed by scanning electron microscopy (SEM). A ZnO nanorod coated on the dense seed layer is clearly visible in the SEM image. The average size of the hexagonal-shaped ZnO rod was around 50 nm in diameter, with a thickness of about 1 mm. X-ray absorption near-edge structures (XANES) were recorded to characterize the structural properties of the prepared film. The obtained normalized Zn K-edge XANES of the film showed the characteristic features of ZnO, which agreed well with the standard ZnO sample. The measurement of Zn K-edge XANES was performed simultaneously with the sensing response. The results showed a good correlation between sensor response and ZnO structure under optimal conditions.

Development of mini-spectrophotometer for determination of plasma glucose.

This work demonstrates a novel compact spectrophotometer, "Mini-spectrophotometer", designed for plasma glucose detection. Unlike conventional spectrophotometer, a light source of the mini spectrophotometer is replaced by a light-emitting diode (LED), and a fabricated polymer-based microwell is used as a cuvette. To validate the downsizing spectrophotometer prototype, the efficiency and reliability for glucose determination are investigated. Using a certain light intensified from LED, the within-run precision of mini-spectrophotometer is found to be 3.9-8.4% while the between-run precision is 6.7-10.8%. The linearity for the quantification of glucose was up to 500 mg dL-1 and the recovery 99.1 ±â€¯3.4% is obtained. The sensitive and selective detection of glucose has been observed; with limit of detection (LOD) of 13.5 mg dL-1 and limit of quantification (LOQ) of 46.2 mg dL-1, respectively. Hemoglobin and triglyceride at high concentration slightly interferes with the proposed instrument. From comparative studies, there are no significant differences between the glucose concentration measured by mini-spectrophotometer and Shimadzu (r2 = 0.9862) or CECIL spectrophotometer (r2 = 0.9853). Using Passing-Bablok regression analysis, the results obtained from mini-spectrophotometer are in close agreement with the two conventional spectrophotometers. Furthermore, using microwell, the sample volume and reagent used in the process can be reduced. The in-house developed mini-spectrophotometer is capable of detecting plasma glucose while maintaining a compact system, demonstrating the potential of high performance, cost-effective, and portable spectrophotometer for clinical chemistry analysis in small routine, research, and teaching medical laboratory technologist.