Development of a surface plasmon resonance sensor using an optical fiber prepared by electroless displacement gold plating and its application to immunoassay

Optical fiber surface plasmon resonance sensor using electroless-plated gold film for thrombin detection

This paper describes the simple and label-free detection of thrombin using optical fiber surface plasmon resonance (SPR) sensors based on gold films prepared by the cost-effective method of electroless plating. The plating conditions for simultaneously obtaining gold film on cylindrical core and end surfaces of an optical fiber suitable for measurement were optimized. The fabricated sensor exhibited a linear refractive index sensitivity of 2150 nm/RIU and 7.136 (a.u.)/RIU in the refractive index of 1.3329-1.3605 interrogated by resonance wavelength and amplitude methods respectively and a single wavelength monitoring method was proposed to investigate the sensing performance of this sensor. Polyadenine diblock and thiolated thrombin aptamers were immobilized on gold nanoparticles and gold films respectively to implement a sandwich optical fiber assay for thrombin. The developed optical fiber SPR sensors were successfully used in the determination of thrombin down to 0.56 nM over a wide range from 2 to 100 nM and showed good selectivity for thrombin, which indicated their potential clinical applications for biomedical samples.

A parylene-mediated plasmonic-photonic hybrid fiber-optic sensor and its instrumentation for miniaturized and self-referenced biosensing

With the development of advanced nanofabrication techniques over the past decades, different nanostructure-based plasmonic fiber-optic sensors have been developed and have presented a low limit of detection for various biomolecules. However, owing to both the dependence on complex equipment and the trade-off between the fabrication cost and sensing performance, nanostructured plasmonic fiber-optic sensors are rarely used outside laboratories. To facilitate wider application of the plasmonic fiber-optic sensors, a parylene-mediated hybrid plasmonic-photonic cavity-based sensor was developed. Compared with a similar plasmonic sensor which only works in the plasmonic mode, the proposed hybrid sensor shows a higher reproducibility (CV < 2.5%) due to its resistance to fabrication variations. Meanwhile, a self-referenced detection mechanism and a novel miniaturized system were developed to adapt to the hybrid resonance sensor. The entire system only has a weight of 263 g, and a size of 12 cm × 10 cm × 8 cm, and is especially suitable for outdoor applications in a handheld manner. In experiments, a high refractive index sensitivity of 3.148 RIU^-1 and real-time biomolecule monitoring at nanomolar concentrations were achieved by the proposed system, further confirming the potential of the miniaturized system as a candidate for point-of-care health diagnostics outside laboratories.

Properties of a Novel Salmonella Phage L66 and Its Application Based on Electrochemical Sensor-Combined AuNPs to Detect Salmonella

Salmonella is widespread in nature and poses a significant threat to human health and safety. Phage is considered as a new tool for the control of food-borne pathogens. In this study, Salmonella phage L66 (phage L66) was isolated from sewage by using Salmonella Typhimurium ATCC 14028 as the host bacterium, and its basic properties were obtained by biological and bioinformatics analysis. Phage L66 had a broad host spectrum, with an optimal infection complex of 0.1 and an optimal adsorption rate of 90.06%. It also exhibited thermal stability between 30 °C~60 °C and pH stability pH from 3 to 12, and the average lysis amount was 46 PFU/cell. The genome sequence analysis showed that the genome length of phage L66 was 157,675 bp and the average GC content was 46.13%. It was predicted to contain 209 genes, 97 of which were annotated with known functions based on the evolutionary analysis, and phage L66 was attributed to the Kuttervirus genus. Subsequently, an electrochemical sensor using phage L66 as a recognition factor was developed and the working electrode GDE-AuNPs-MPA-Phage L66 was prepared by layer-by-layer assembly for the detection of Salmonella. The slope of the impedance was 0.9985 within the scope from 20 to 2 × 10⁷ CFU/mL of bacterial concentration. The minimum detection limit of the method was 13 CFU/mL, and the average spiked recovery rate was 102.3% with a relative standard deviation of 5.16%. The specificity and stability of this sensor were excellent, and it can be applied for the rapid detection of Salmonella in various foods. It provides a phage-based electrochemical biosensor for the detection of pathogenic bacteria.