Surface plasmon resonance has established itself as an immensely acclaimed and influential optical sensing tool with quintessential applications in life sciences, environmental monitoring, clinical diagnostics, pharmaceutical developments and ensuring food safety. The implementation of sensing principle of surface plasmon resonance employing an optical fiber as a substrate has concomitantly resulted in the evolution of fiber optic surface plasmon resonance as an exceptionally lucrative scaffold for chemical and biosensing applications. This perspective article outlines the contemporary studies on fiber optic sensors founded on the sensing architecture of propagating as well as localized surface plasmon resonance. An in-depth review of the prevalent analytical and surface chemical tactics involved in configuring the sensing layer over an optical fiber for the detection of various chemical and biological entities is presented. The involvement of nanomaterials as a strategic approach to enhance the sensor sensitivity is furnished concurrently providing an insight into the diverse geometrical blueprints for designing fiber optic sensing probes. Representative examples from the literature are discussed to appreciate the latest advancements in this potentially valuable research avenue. The article concludes by identifying some of the key challenges and exploring the opportunities for expanding the scope and impact of surface plasmon resonance based fiber optic sensors.

[INVITED] Recent advances in surface plasmon resonance based fiber optic chemical and biosensors utilizing bulk and nanostructures

Glyco-gold nanoparticles combine in a single entity the peculiar properties of gold nanoparticles with the biological activity of carbohydrates The result is an exciting nanosystem, able to mimic the natural multivalent presentation of saccharide moieties and to exploit the peculiar optical properties of the metallic core In this review, we present recent advances on glyco-gold nanoparticle applications in different biological fields, highlighting the key parameters which inspire the glyco nanoparticle design

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-13-100.pdf

Glyco-gold nanoparticles: synthesis and applications.

We demonstrate the transfer of arrays of nanofabricated noble metal and alloy nanostructures obtained by high-temperature annealing on a flat parent support onto optical fibers, to create a hysteresis-free fiber optic nanoplasmonic hydrogen sensor. This work enables the integration of complex nanofabricated structures and their arrangements in tailored arrays with fiber optics to realize optical sensors, which will find application in a wide range of disciplines.

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A fiber-optic nanoplasmonic hydrogen sensor via pattern-transfer of nanofabricated PdAu alloy nanostructures.

Label-free and in situ detection of N-glycan expression on surface of cells is vital for understanding the progression of cancer. Herein, cytosensing based on U-shaped fiber optic local surface plasmon resonance (LSPR) was developed for cancer cell detection and N-glycan evaluation on cell surface. The U-shaped fiber optic LSPR has high refractive index sensitivity (RIS). Therefore, U-shaped fiber optic LSPR cytosensing afforded ultrasensitivity for cancer cell detection with the limit of detection (LOD) of 30 cells/mL and good linearity in a wide range of 1×102-1×106 cells/mL under the optimal conditions of modified AuNPs size and Con A concentration. The U-shaped fiber optic LSPR cytosensing shows more than 29 times lower limit of detection than the straight ones. More importantly, the prepared U-shaped cytosensing was applied to evaluate the N-glycan expression level on the surface of cancer cells under different concentration external stimuli of inhibitor tunicamycin (TM). Noticeably, U-shaped fiber optic LSPR cytosensing showed an acceptable reproducibility, satisfactory anti-interference and good selectivity, and was also applied in the assessment of N-glycan expression on surface of six kinds of cell lines. Therefore, the U-shaped fiber optic LSPR offers a feasible tool in biophysical research and clinical diagnosis for cancer.

Ultrasensitive U-shaped fiber optic LSPR cytosensing for label-free and in situ evaluation of cell surface N-glycan expression

Abstract The concentration of light to deep-subwavelength dimensions plays a key role in nanophotonics and has the potential to bring major breakthroughs in fields demanding to understand and initiate interaction on nanoscale dimensions, including molecular disease diagnostics, DNA sequencing, single nanoparticle manipulation and characterization, and semiconductor inspection. Although planar metallic nanostructures provide a pathway to nanoconcentration of electromagnetic fields, the delivery/collection of light to/from such plasmonic nanostructures is often inefficient, narrow-band, and requires complicated excitations schemes, limiting widespread applications. Moreover, planar photonic devices reveal a reduced flexibility in terms of bringing the probe light to the sample. An ideal photonic-plasmonic device should combine (i) a high spatial resolution at the nanometre level beyond to what is state-of-the-art in near-field microscopy with (ii) flexible optical fibers to promote a straightforward integration into current near-field scanning microscopes. Here, we review the recent development and main achievements of nanoconcentrators interfacing optical fibers at their end-faces that reach entirely monolithic designs, including campanile probes, gold-coated fiber-taper nanotips, and fiber-integrated gold nanowires.

/pdf/interfacing-optical-fibers-with-plasmonic-nanoconcentrators-2i8k9tp3g3.pdf

Interfacing optical fibers with plasmonic nanoconcentrators

The COVID-19 pandemic has created urgent demand for rapid detection of the SARS-CoV-2 coronavirus. Herein, we report highly sensitive detection of SARS-CoV-2 nucleocapsid protein (N protein) using nanoparticle-enhanced surface plasmon resonance (SPR) techniques. A crucial plasmonic role in significantly enhancing the limit of detection (LOD) is revealed for exceptionally large gold nanoparticles (AuNPs) with diameters of hundreds of nm. SPR enhanced by these large nanoparticles lowered the LOD of SARS-CoV-2 N protein to 85 fM, resulting in the highest SPR detection sensitivity ever obtained for SARS-CoV-2 N protein. 

/pdf/ultrasensitive-detection-of-sars-cov-2-nucleocapsid-protein-2bcgkwf0.pdf

Ultrasensitive detection of SARS-CoV-2 nucleocapsid protein using large gold nanoparticle-enhanced surface plasmon resonance

/pdf/ultrasensitive-detection-of-sars-cov-2-nucleocapsid-protein-2kek5fy1.pdf

Optical fiber-type Sugar Chips were developed using localized surface plasmon resonance (LSPR) of gold (Au) nanoparticles. The endface of an optical fiber was first aminosilylated and then condensed with α-lipoic acid containing a dithiol group. Second, gold nanoparticles were immobilized onto the endface via an Au–S covalent bond. Finally, sugar moieties were attached to the gold nanoparticle using our original sugar chain–ligand conjugates to obtain fiber-type Sugar Chips, by which the sugar moiety–protein interaction was analyzed. The specificity, sensitivity, and quantitative binding potency against carbohydrate-binding protein were found to be identical to that of a conventional SPR sensor. In this analysis, only a small sample volume (approximately 10 μL) was required compared with 100 μL for the conventional SPR sensor, suggesting that the fiber-type Sugar Chip and LSPR are applicable for nonpure small masses of proteins.

Optical Fiber-Type Sugar Chip Using Localized Surface Plasmon Resonance.

Background: Preeclampsia is a major cause of maternal and perinatal morbidity and mortality worldwide. Identifying women with high risk of developing preeclampsia in early pregnancy remains challenging. Extracellular vesicles released from the placenta offer an attractive biomarker but have been elusive to quantify. Methods: Here, we tested ExoCounter, a novel device that immunophenotypes size-selected small extracellular vesicles <160 nm, for its ability to perform qualitative and quantitative placental small extracellular vesicles (psEV) analysis. To investigate disease-specific and gestational age-specific changes, we analyzed psEV counts in maternal plasma samples taken at each of the 3 trimesters from women who had (1) normal pregnancy (n=3); (2) women who developed early-onset preeclampsia (EOPE; n=3); and (3) women who developed late-onset preeclampsia (n=4) using 3 antibody pairs, CD10-placental alkaline phosphatase (PLAP), CD10-CD63, and CD63-PLAP. We further validated the findings in first-trimester serum samples among normal pregnancy (n=9), women who developed EOPE (n=7), and women who developed late-onset preeclampsia (n=8). Results: We confirmed that CD63 was the major tetraspanin molecule coexpressed with PLAP—a known placental extracellular vesicles marker on psEV. Higher psEV counts for all 3 antibody pairs were detected in the plasma of women who developed EOPE than the other 2 groups in the first trimester, which persisted through the second and third trimesters. Significantly higher CD10-PLAP (P<0.01) and CD63-PLAP (P<0.01) psEV counts were validated in the serum of the first trimester of women who developed EOPE compared with normal pregnancy. Conclusions: Application of the ExoCounter assay developed here could identify patients at risk of developing EOPE in the first trimester, thereby providing a window of opportunity for early intervention.

ExoCounter Assays Identify Women Who May Develop Early-Onset Preeclampsia From 12.5 μL First-Trimester Serum by Characterizing Placental Small Extracellular Vesicles

Atsushi Saito

Papers

Ultrasensitive detection of SARS-CoV-2 nucleocapsid protein using large gold nanoparticle-enhanced surface plasmon resonance

Ultrasensitive detection of SARS-CoV-2 nucleocapsid protein using large gold nanoparticle-enhanced surface plasmon resonance

Optical Fiber-Type Sugar Chip Using Localized Surface Plasmon Resonance.

ExoCounter Assays Identify Women Who May Develop Early-Onset Preeclampsia From 12.5 μL First-Trimester Serum by Characterizing Placental Small Extracellular Vesicles