Metal-Enhanced Fluorescence for Alpha-Fetoprotein Detection and for SERS Using Hybrid Nanoparticles of Magnetic Cluster Core—Plasmonic Shell Composite

We demonstrated that the hybrid core–shell nanostructure of Fe3O4 (core) and gold (shell) could be a good substrate candidate both for metal-enhanced fluorescence (MEF) and surface-enhanced Raman spectroscopy (SERS). The magnetic properties of the core material could provide functionalities such as the magnetically induced aggregation/distribution of nanostructures to increase the hot-spot density, while the nano-thickness gold shell allows for the plasmonic enhancement of both fluorescence and SERS. The gold-capped magnetic (Fe3O4) nanoparticles (GMPs) were facilely synthesized using a newly developed chemical method. The relative molar ratio of the constituent materials of the core–shell composite was optimized for tuning the plasmonic resonance wavelengths for MEF and SERS. We employed GMP-based MEF to detect alpha-fetoprotein (AFP), with concentrations ranging from 0.05 to 1000 ng/mL, and obtained a limit of detection (LOD) as low as 3.8 × 10−4 ng/mL. The signal enhancement factor (EF) in the GMP-based MEF was 1.5 at maximum. In addition, the GMPs were used in SERS to detect rhodamine B (RhB). Its LOD was 3.5 × 10−12 M, and the EF was estimated to be about 2 × 108. The hybrid core–shell nanoparticles could find potential applications in diagnostic assays based on MEF and SERS in various fields such as food verification, environmental testing/monitoring, and disease diagnosis

Portable and non-invasive blood glucose monitoring over a prolonged period using whispering gallery modes at 2.4 GHz

Invasive measurement of blood glucose is not appropriate for everyone, particularly the patients with leukemia. Here, we demonstrate how the blood glucose can be non-invasively monitored over a prolonged period in the absence of any expensive equipment. Method: A portable and non-invasive glucose sensor capable of monitoring blood glucose at real-time has been successfully constructed and tested in the absence of any vector network analyzer. Using vacuum suction, the sensor head of the proposed non-invasive glucose sensor forms a whispering gallery resonator out of a skin tissue on an arm during the measurement process. The architecture of the proposed glucose sensor is equipped with standard components, including a WiFi transmitter, an RSSI sensor and a microcontroller based computer display. Results: Using the proposed glucose sensor, a healthy volunteer has been his blood glucose levels monitored over 72 minutes after consuming a loaf of bread and a cup of cow milk. The measured blood glucose rose shortly after the meal until it peaked at 40 minutes and finally fell to the initial value at around 72 minutes. Conclusion: The overall results were in general consistent with the expected results. The proposed glucose sensor is expected to be instrumental for the individuals who dislike the traditional lancets