Search

L-cysteine conjugated molybdenum disulphide (MoS2) nanosheets have been covalently attached to a gold coated surface plasmon resonance (SPR) optical fiber to prepare a robust and stable sensor. Owing to the multifunctionality of the deposited nanosheet conjugate, the antibodies are also covalently conjugated in the subsequent step to realize the design of a SPR optical fiber biosensor for the two important bioanalytes namely, Ferritin and Immunoglobin G (IgG). The different stages of the biosensor preparation have been characterized and verified with microscopic and spectroscopic techniques. A uniform and stable deposition of the L-cysteine/MoS2 nanosheets has allowed the biosensor to be reused for multiple times. Unlike the peeling-off of the MoS2 coatings from the gold layer reported previously in the case of physically adsorbed nanomaterial, the herein adopted strategy addresses this critical concern. It has also been possible to use the single SPR fiber for both Ferritin and IgG bioassay experiments by regenerating the sensor and immobilizing two different antibodies in separate steps. For ferritin, the biosensor has delivered a linear sensor response (SPR wavelength shifts) in the concentration range of 50–400 ng/mL, while IgG has been successfully sensed from 50 to 250 µg/mL. The limit of detection for Ferritin and IgG analysis have been estimated to be 12 ng/mL and 7.2 µg/mL, respectively. The biosensors have also been verified for their specificity for the targeted molecule only. A uniform and stable deposition of the nanomaterial conjugate, reproducibility, regeneration capacity, a good sensitivity, and the specificity can be highlighted as some of key features of the L-cysteine/MoS2 optical fiber biosensor. The system can be advocated as a useful biosensor setup for the sensitive biosensing of Ferritin and IgG. [ABSTRACT FROM AUTHOR]

Abstract The molybdenum disulfide (MoS 2) nanosheets functionalized fiber optic surface plasmon resonance (SPR) immunosensor has been reported for the sensitive detection of Escherichia coli (E. coli). The MoS 2 nanosheets were prepared by chemical exfoliation method. The synthesised nanostructures were characterized for their structural, morphological and optical properties. The E. coli monoclonal antibodies were successfully immobilized on the MoS 2 functionalized sensing platform via hydrophobic interactions. An alternative method simplifying the antibodies immobilization process by functionalization of 2D nanomaterial (MoS 2 nanosheets) for rapid (~15 mins) bacterial quantification is presented in this study. The immunosensor uses wavelength interrogation method and a strong linear relationship (R2 = 0.994) was observed between spectral response of immunosensor and different concentration of E. coli. The nonspecificity and cross-reactivity studies of the developed immunosensor were investigated with detection of Salmonella Typhimurium and Staphylococcus aureus. To demonstrate the practical application, spiked samples of water and orange juice were analysed with acceptable recovery results. The label-free immunosensor exhibits better performance, detection limit (94 CFU/mL), high sensitivity (2.9 nm/1000 CFU mL−1; 3135 nm/RIU) and profound specificity as compared to conventional fiber optic SPR sensor (detection limit: 391 CFU/mL, sensitivity: 0.6 nm/1000 CFU mL−1; 1646 nm/RIU). This sensing platform shows promising applications in regular water and food quality monitoring for various pathogenic microorganisms. Graphical abstract fx1 Highlights • A fiber optic SPR immunosensor with functionalized MoS 2 nanosheets is reported. • 2D MoS 2 nanosheets improved the SPR immunosensor sensitivity (LOD: 94 CFU/mL). • Selectivity analysis of the developed immunosensor was investigated. • The developed method offers simple bio-functionalization and rapid quantification. • For practicality, spiked samples of drinking water and orange juice were tested. [ABSTRACT FROM AUTHOR]

[Display omitted] • A functional fluorescent nanocomposite of Tb-BTC MOF with MoS 2 nanosheets is prepared. • The antibodies (Ab) are covalently conjugated to the Tb-BTC/MoS 2 composite. • Ab/Tb-BTC/MoS 2 offers highly selective and convenient detection of HepG2 cells. The photoluminescence-based detection of circulating tumor cells (CTCs) can offer the development of rapid, simple, and sensitive techniques for the screening of cancer at early stages as well the monitoring of therapy progression. The present work reports the application of a photoluminescent composite of Terbium based metal–organic framework (Tb-BTC MOF) with L-cysteine conjugated molybdenum disulphide (MoS 2) nanosheets for the highly sensitive immunosensing of HepG2 cells. The formation of the above composite facilitates the achievement of a highly fluorescent, large surface area material with abundant carboxyl functionality. This novel composite has been immobilized with the anti-EpCAM antibodies to form the desired immunosensor for HepG2 cells. After spectroscopic and morphological characterizations, the antibody immobilized Tb-BTC/MoS 2 bioprobe (Ab/Tb-BTC/MoS 2) has been investigated for the sensing of HepG2 cells (10–1000 cells). Based on the PL quenching mechanism, the above bioprobe has delivered a broad range analysis with a low limit of detection (8 cells). The Ab/Tb-BTC/MoS 2 bioprobe is also found selective toward other possible interferants, such as HEK cells, bovine serum albumin, immunoglobin G, and glucose. [ABSTRACT FROM AUTHOR]