Plasma-Enabled Carbon Nanostructures for Early Diagnosis of Neurodegenerative Diseases

Analysis and detection of women's reproductive hormones using a bistable and reconfigurable 1D annular photonic crystal composed of the Ge2Sb2Te5 phase-change material

In this study, the reconfigurable biosensing capabilities of the one-dimensional annular photonic structure, (AB)5CDC(AB)5, was examined theoretically. The proposed structure was made of concentric cylindrical layers of periodically modulated refractive indices, which were restricted in one direction only. Germanium antimony telluride (GST), which belongs to the class of phase-change materials (PCMs), was used in the fabrication of the proposed biosensing design. The entire study was carried out in the near-infrared region of the electromagnetic spectrum. The suggested biosensing structure was constructed by depositing alternate periodic cylindrical layers of SiO2 and Si with a central air core. An air cavity coated on both sides by a phase-change chalcogenide material (Ge2Sb2Te5) was introduced at the centre of the 1D annular photonic crystal to realize the (AB)5CDC(AB)5 structure. The simulation results of the proposed work were obtained using the MATLAB computational tool taking into consideration the modified transfer matrix method. The primary focus of this study was to measure the change in the position and intensity of the defect mode with respect to the change in the concentration levels of analytes containing progesterone and estradiol reproductive hormones separately in the amorphous and crystalline phases of the Ge2Sb2Te5 material. Interestingly, a strong tunability in the position of the central wavelength of the defect mode inside the photonic band gap (PBG) was noticed during the phase transition of the GST material from amorphous to crystalline and back. In both the phases of the GST material, our design could identify minute refractive index variations in blood samples containing reproductive hormones at different concentrations for monitoring various gynaecological disorders in women. Besides sensitivity, other important parameters such as the limit of detection, signal-to-noise ratio, and quality factor were estimated to evaluate the biosensing capabilities of the proposed design.

Biophotonic sensor design using a 1D defective annular photonic crystal for the detection of creatinine concentration in blood serum

A new biophotonic sensor composed of a porous silicon (PSi)-based one-dimensional (1D) defective annular photonic crystal (APC) was designed and theoretically investigated using a modified transfer matrix method (TMM) in terms of cylindrical coordinates. The proposed biosensor was found to be capable of sensing very minute variations in the refractive index of blood serum samples of different creatinine concentrations. It can be considered as a useful tool for diagnosing mild to chronic kidney diseases by measuring the creatinine concentration in the blood serum samples of patients. The biosensor design [(AB)^N/2D(AB)^N/2/Si] is composed of two 1D APCs (AB)^N/2 associated with a defect layer D of a blood serum sample of thickness d_d whose creatinine concentration is to be determined. Both 1D APCs are made up of two alternate PSi layers A and B with porosity ratios of 34% and 87%, respectively. Moreover, our proposed biophotonic sensor demonstrated a high value of sensitivity (S) between 637.73 and 640.29 nm per RIU, a quality factor (Q) between 1.51 × 10⁵ and 0.74 × 10⁵, and a figure of merit (FOM) between 2.6 × 10⁴ and 1.96 × 10⁴ RIU, corresponding to a blood serum sample whose creatinine concentration varied between 80.90 to 85.28 μmol L⁻¹. The limit of detection (LOD) was of the order of 10⁻⁶ RIU. This low value LOD confirmed that our biosensor is capable of noticing any minute change in the wavelength up to an order of 10⁻⁶. Compared with previous works, the proposed biosensor design can be easily realized and offers high performance at normal incidence, which allows overcoming the complications involved while achieving a high value of sensitivity in planar PC-based biosensor designs at oblique incidence. Beside this, there is also a possibility to explore this work further for the development of various APC-based biosensing designs with the aim to study various human body fluids.

A new biophotonic sensor composed of a porous silicon (PSi)-based one-dimensional (1D) defective annular photonic crystal (APC) was designed and theoretically investigated using a modified transfer matrix method (TMM) in terms of cylindrical coordinates.

A label-free aptasensor FET based on Au nanoparticle decorated Co3O4 nanorods and a SWCNT layer for detection of cardiac troponin T protein

Acute myocardial infarction (AMI) is a serious health problem that must be identified in its early stages. Considerable progress has been made in understanding the condition of AMI through ascertaining the role of biomarkers, such as myoglobin, cardiac troponin proteins (T and I), creatine kinase-MB, and fatty acid-binding protein (FABP). A field-effect transistor (FET) is an effective platform; however, innovations are required in all layers of the FET for it to become robust and highly sensitive. For the first time, we made use of the synergistic combination of noble metal nanoparticles (AuNPs) with Co₃O₄ for the detection of cardiac troponin T (cTnT) in a FET platform. We determined the morphology of Au-decorated Co₃O₄ NRs and their electronic properties by characterizing the channel layer using electron microscopies and transient measurements. Subsequently, we performed the detection of cardiac troponin T by immobilizing its complementary biotinylated DNA aptamer on the channel surface using a drop-casting method. To understand the changes in drain current caused by this interaction, we probed our SWCNT-Co₃O₄ NR transistor with limited gate and drain bias (≤1 V), achieving a sensitivity of 0.5 μA μg^-1 mL^-1 for the Au-decorated NRs. A 250% increase in the sensitivity and a limit of detection (LOD) of 0.1 μg mL^-1 were achieved by using this device. Finally, selectivity studies proved that this synergistic combination works well in the FET configuration for the successful detection of cTnT.

Biosensors in Health Care: The Milestones Achieved in Their Development towards Lab-on-Chip-Analysis

Immense potentiality of biosensors in medical diagnostics has driven scientists in evolution of biosensor technologies and innovating newer tools in time. The cornerstone of the popularity of biosensors in sensing wide range of biomolecules in medical diagnostics is due to their simplicity in operation, higher sensitivity, ability to perform multiplex analysis, and capability to be integrated with different function by the same chip. There remains a huge challenge to meet the demands of performance and yield to its simplicity and affordability. Ultimate goal stands for providing point-of-care testing facility to the remote areas worldwide, particularly the developing countries. It entails continuous development in technology towards multiplexing ability, fabrication, and miniaturization of biosensor devices so that they can provide lab-on-chip-analysis systems to the community.