Capabilities of Double-Resonance LPG and SPR Methods for Hypersensitive Detection of SARS-CoV-2 Structural Proteins: A Comparative Study.

The danger of the emergence of new viral diseases and their rapid spread demands apparatuses for continuous rapid monitoring in real time. This requires the creation of new bioanalytical methods that overcome the shortcomings of existing ones and are applicable for point-of-care diagnostics. For this purpose, a variety of biosensors have been developed and tested in proof-of-concept studies, but none of them have been introduced for commercial use so far. Given the importance of the problem, in this study, long-period grating (LPG) and surface plasmon resonance (SPR) biosensors, based on antibody detection, were examined, and their capabilities for SARS-CoV-2 structural proteins detection were established. Supersensitive detections of structural proteins in the order of several femtomoles were achieved by the LPG method, while the SPR method demonstrated a sensitivity of about one hundred femtomoles. The studied biosensors are compatible in sensitivity with ELISA and rapid antigen tests but, in contrast, they are quantitative, which makes them applicable for acute SARS-CoV-2 infection detection, especially during the early stages of viral replication.

Proposal for optical fiber designs with ultrahigh effective area and small bending loss applicable to long haul communications.

A proposal for the multiclad MII optical fiber structure with ultralarge effective area and small bending loss is presented. For the proposed structure small dispersion and dispersion slope are obtained thanks to what we believe to be a novel design method. The suggested design method is based on a weighted fitness function, which is applied to the genetic algorithm optimization technique. In the meantime, the foregoing structure introduces a special fiber whose mode field diameter is small and approximately insensitive to the variation of the effective area. Compared to the work reported previously, our method can precisely set the zero dispersion wavelength. The designed dispersion-shifted single-mode fibers have effective area, mode field diameter, and quality factor respectively within [150-194.79] microm(2), [6.82-7.95] microm, and [3.04-3.85] at lambda(0)=1.55 microm. An analytical method is used for the calculation of the dispersion and its slope. These calculations give dispersion and dispersion slope of [(-2.57 x 10(-4))-(-0.085)] ps/km/nm and approximately 0.064 ps/km x nm(2), respectively.