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find me all the efforts to detect fluorescence of the spike protein
  • The request is to find efforts detecting fluorescence of the spike protein. I'm curious about this, as it sounds like a scientific topic.
Searching for "detect fluorescence of spike protein SARS-CoV-2"
pmc.ncbi.nlm.nih.gov
www.nature.com
www.labcorp.com
pmc.ncbi.nlm.nih.gov
www.ncbi.nlm.nih.gov
  • From the search, a paper on "Studying SARS-CoV-2 with Fluorescence Microscopy" PMC uses FRET to study spike protein interactions.
  • Another study, "Optimized production and fluorescent labeling" Nature, tags N or M proteins for fluorescent VLPs.
  • A study on "In-Vitro Fluorescence Microscopy" bioRxiv examines spike protein retention using fluorescence microscopy.
  • There's also a paper on "Fluorescence signatures" PMC providing spectral data for the spike protein and ACE2.
  • This paper on "SARS-CoV-2 spike protein detection" Springer uses optical fibers for label-free detection.
  • Another study, "Development of an Optical Assay" medRxiv, proposes a smartphone-based optical method for detecting spike protein.
  • The review "SARS-CoV-2 detection methods" might cover fluorescence techniques. I'm checking if it includes spike protein detection.
  • It aims for affordable, fast tests, which could fit fluorescence methods. Let's see what it says about optical detection.
Browsing sciencedirect.com for "fluorescence detection of spike protein"
  • RT-qPCR uses fluorescent dyes to detect genes related to the S protein, though it's indirect. I'm noting this as part of the efforts.
  • RT-LAMP fluorescence also detects S gene using dyes like SYBR green. This adds to the list of methods.
  • Optical biosensors use photoluminescence spectroscopy to detect S protein directly, with a limit of 0.0125 μg/mL for IgG Saudi Journal.
  • Nano-based sensors with quantum dots examine S protein–ACE2 binding, adding to fluorescence methods Saudi Journal.
Browsing pmc.ncbi.nlm.nih.gov for "fluorescence detection of spike protein"
  • A paper provides detailed fluorescence data for the spike protein S1 and RBD, including excitation-emission maps and lifetimes Combined Spectra, S1.
  • This focuses on intrinsic fluorescence, which is interesting but may not cover all detection efforts, especially those using labels.
Browsing pmc.ncbi.nlm.nih.gov for "methods to detect spike protein fluorescence"
  • Immunofluorescence uses antibodies with fluorophores to detect the spike protein. It's a key method for visualizing it in cells.
  • Fusion with fluorescent proteins like GFP or mCherry helps track the spike protein in real time. This approach is common in lab studies.
Browsing nature.com for "fluorescent labeling of spike protein"
  • This study produced fluorescent VLPs with the spike protein, using immuno-spotting and TIRF microscopy. They found 27 ± 12% incorporation in M(GFP)NES VLPs Nature.
  • Optical biosensors mentioned earlier seem to detect antibodies, not the spike protein directly. I'm double-checking to ensure accuracy.
Browsing link.springer.com for "fluorescence"
  • The paper mentions fluorescence-based fiber-optic probes in optical biosensors, but it's not fluorescence-based; it's multi-mode interference and refractive index changes.
  • Another paper, "Development of an Optical Assay," proposes a smartphone-based method to detect spike protein interactions with ACE2, but doesn't specify if it's fluorescence-based.
Browsing medrxiv.org for "fluorescence"
  • This paper doesn't involve fluorescence; it's likely using absorbance or reflectance. So, it's not relevant for fluorescence detection.
  • Perhaps I need to find other sources for fluorescence-based biosensors for the spike protein. There might be more studies using FRET or other techniques.
  • FRET-based platforms study spike protein cleavage by TMPRSS2, measuring disruption between green and red fluorescent proteins. This is relevant for understanding its function.
  • FlipGFP fluoresces after cleavage by 3CLpro, detecting protease activity related to SARS-CoV-2. It's indirect but involves the spike protein.
Searching for "fluorescence-based detection of SARS-CoV-2 spike protein"
pmc.ncbi.nlm.nih.gov
www.sciencedirect.com
www.nature.com
pubs.acs.org
www.nature.com
  • SR-DFC strategy uses fluorescent probes on gold arrays to capture and identify the spike protein, achieving high accuracy with super-resolution microscopy ScienceDirect.
  • Carbon nanotube-based nanosensors detect the spike protein via fluorescence changes, using ACE2-functionalized nanotubes for near-infrared detection Nano Letters.
  • The search provided new results, including a dual-signal imaging mode using fluorescence and electrochemiluminescence for spike protein detection.
  • This dual-mode platform uses a DNAzyme walker for accurate, sensitive detection, reducing false signals Analytical Chemistry.
  • There's a lot here, so let's organize these findings. I'm thinking of grouping them by technique for clarity.
  • The SR-DFC and carbon nanotube methods are new, adding to the list of fluorescence detection efforts. This should help with a comprehensive answer.
  • The SR-DFC strategy captures the spike protein with fluorescent probes on gold arrays. It uses super-resolution microscopy for high accuracy, which is promising.
  • The dual-signal imaging mode combines fluorescence and electrochemiluminescence. It employs a DNAzyme walker for sensitive detection, cutting down on false results.
Searching for "flow cytometry detection of SARS-CoV-2 spike protein"
ncbi.nlm.nih.gov
www.nature.com
pubmed.ncbi.nlm.nih.gov
www.sciencedirect.com
link.springer.com
  • Flow virometry uses flow cytometry to detect SARS-CoV-2 particles. It labels them with fluorescent antibodies against the spike protein, which fits our focus.
  • This method involves mixing samples with primary and secondary antibodies, then analyzing with a laser. It's another way to detect the spike protein using fluorescence.
  • I'm adding flow virometry to the list of efforts. This should help cover more ground for the request.
  • Intrinsic fluorescence studies detail the spike protein's natural properties. This helps understand its baseline fluorescence behavior.
  • Fluorescence microscopy techniques include immunofluorescence and fusion with proteins like GFP. These methods visualize the spike protein effectively in cells.
  • Quantum dots and fluorescent VLPs track the spike protein, offering insights into its behavior. These approaches are useful for imaging and analysis.
  • FRET-based platforms and biosensors, like carbon nanotubes, study interactions and detect the spike protein. They're innovative for research and diagnostics.
  • Super-resolution dual fluorescence co-localization uses probes for accurate detection. It leverages super-resolution microscopy, which is cutting-edge.
  • The dual-signal imaging mode combines fluorescence with electrochemiluminescence. It uses a DNAzyme walker for ultrasensitive results, which is impressive.
  • Flow virometry detects virus particles with fluorescent antibodies. It enables large-scale screening, which is great for public health efforts.
Key Points
  • Research suggests multiple methods exist to detect the fluorescence of the SARS-CoV-2 spike protein, focusing on both natural and labeled fluorescence.
  • It seems likely that techniques like immunofluorescence and biosensors are commonly used, but the evidence leans toward a variety of approaches depending on the application.
  • There is ongoing research, and some methods, like super-resolution microscopy, show high accuracy, though results can vary by study.
Overview
The SARS-CoV-2 spike protein, crucial for viral entry into cells, can be detected using fluorescence-based methods, which are vital for research and diagnostics. These methods often involve labeling the protein with fluorescent tags or studying its natural fluorescence, offering insights into viral behavior and infection mechanisms.
Methods and Applications
Several techniques are employed, including:
  • Fluorescence Microscopy: Uses tools like immunofluorescence to visualize the spike protein in cells, aiding in understanding viral distribution.
  • Biosensors: Advanced sensors, such as carbon nanotube-based ones, detect the protein by changes in fluorescence, useful for rapid diagnostics.
  • Flow Virometry: Detects virus particles with fluorescent antibodies, suitable for large-scale screening.
These methods are supported by studies showing their effectiveness, with URLs provided for further reading (Fluorescence signatures of SARS-CoV-2 spike S1 proteins, Studying SARS-CoV-2 with Fluorescence Microscopy).
Survey Note: Comprehensive Analysis of Fluorescence Detection Efforts for SARS-CoV-2 Spike Protein
The detection of fluorescence associated with the SARS-CoV-2 spike protein has been a significant area of research, particularly given its role in viral entry and its relevance to COVID-19 diagnostics and therapeutics. This note provides a detailed survey of the various efforts, categorized by technique, and includes specific findings, methodologies, and supporting evidence from recent studies. The focus is on methods that directly or indirectly leverage fluorescence to study or detect the spike protein, ensuring a comprehensive overview for researchers and professionals in the field.
Intrinsic Fluorescence Studies
One approach involves examining the intrinsic fluorescence of the spike protein, which arises from its natural fluorophores, such as tryptophan and tyrosine residues. A notable study, "Fluorescence signatures of SARS-CoV-2 spike S1 proteins and a human ACE-2"
, provides detailed spectral and temporal data. This research recorded excitation-emission maps for the spike protein S1 subunit and its receptor-binding domain (RBD), with excitations from 220 to 300 nm and emissions from 230 to 500 nm. Key findings include major emission maxima at 330 nm for S1 and human ACE2, and 325 nm for RBD at certain excitation wavelengths, with fluorescence peaks between 290 and 410 nm indicating tryptophan and tyrosine sites. Fluorescence decay times were measured using a biexponential model, with average fast and slow decay components noted, enhancing the understanding of the protein's optical properties for potential detection schemes. Data availability is supported by supplementary URLs, such as combined spectra for S1 and RBD, accessible via DOIs like Combined Spectra, S1.
Fluorescence Microscopy Techniques
Fluorescence microscopy has been extensively used to visualize and study the spike protein, often involving extrinsic labeling. A study, "Studying SARS-CoV-2 with Fluorescence Microscopy"
, highlights several methods:
  • Immunofluorescence: This technique uses fluorophore-labeled antibodies to detect the spike protein, particularly useful for studying its distribution in cells. For instance, colocalization with Golgi marker GM130 showed retention in intracellular vesicles when coexpressed with M or E proteins, as referenced in the study.
  • Fusion with Fluorescent Proteins: The spike protein is genetically fused with fluorescent proteins like GFP or mCherry for real-time visualization. An example includes S-GFP coexpression with M, N, and E in HEK293 cells to study entry via endocytic pathways, detailed in references like Generation and characterization of recombinant SARS-CoV-2 expressing reporter genes.
  • Quantum Dots (QDs): Spike protein subunits are conjugated to quantum dots for tracking, enabling monitoring via energy transfer quenching with ACE2-conjugated gold nanoparticles, as noted in the study with reference 53 (#B53-ijms-22-06558).
  • Dual Staining (IHC and ISH): Combines immunohistochemistry and in situ hybridization to detect the spike protein and viral RNA in formalin-fixed paraffin-embedded specimens, showing antigen with positive-sense RNA in the cytoplasm, referenced in 50 (#B50-ijms-22-06558).
  • Immuno-RNA-FISH: Integrates RNA-FISH with immunofluorescence for visualizing SARS-CoV-2 RNA and proteins, using hybridization chain reaction to minimize background fluorescence, as detailed in 51 (#B51-ijms-22-06558).
Another significant effort is "Optimized production and fluorescent labeling of SARS-CoV-2 virus-like particles"
, which focused on creating fluorescent Virus-Like Particles (VLPs). These VLPs, tagged with fluorescent proteins on M and N, incorporated the spike protein at 27 ± 12% in M(GFP)NES VLPs, evaluated using immuno-spotting and Total Internal Reflection Fluorescence (TIRF) Microscopy, as shown in Figure 4 (/articles/s41598-022-18681-z#Fig4)B. This method aids in imaging viral assembly and entry, with live fluorescence and super-resolution microscopies quantifying VLP sizes (110–140 nm) and concentrations (10^12 VLP/ml).
Fluorescence-Based Biosensors and Assays
Advanced biosensors and assays have been developed for direct detection, leveraging fluorescence changes. "Highly accurate detection of SARS-CoV-2 using a super-resolution fluorescence colocalization strategy"
introduces a super-resolution dual fluorescence co-localization (SR-DFC) strategy. This method uses fluorescent capture probes on periodically structured gold array substrates to capture the spike protein, followed by fluorescent recognition probes forming sandwich-like immune complexes, analyzed via single-molecule localization microscopy (SMLM) to reduce false positives.
Another innovative approach is "Rapid SARS-CoV-2 Spike Protein Detection by Carbon Nanotube-Based Near-Infrared Nanosensors"
, which uses single-walled carbon nanotubes (SWCNTs) functionalized with ACE2. The presence of the spike protein elicits a robust 2-fold fluorescence increase within 90 minutes, with stability maintained in saliva and viral transport medium. Surface-immobilized formats showed a 73% fluorescence turn-on response within 5 seconds for 35 mg/L SARS-CoV-2 virus-like particles, demonstrating rapid optical detection potential.
A dual-mode imaging platform is described in "Dual-Signal Imaging Mode Based on Fluorescence and Electrochemiluminescence for Ultrasensitive Visualization of SARS-CoV-2 Spike Protein"
. This platform uses a self-powered DNAzyme walker for simultaneous fluorescence (FL) and electrochemiluminescence (ECL) detection, achieving high sensitivity at the single-molecule level by recording reductions in fluorescence spots and appearances of ECL spots, enhancing accuracy and reducing false signals.
Flow Virometry
Flow virometry offers a method for large-scale screening, as seen in "A flow virometry process proposed for detection of SARS-CoV-2 and large-scale screening of COVID-19 cases"
. This approach uses flow cytometry to detect SARS-CoV-2 virus particles, with samples mixed with primary antibodies (specific to human anti-SARS-CoV-2 S1 or spike RBD) and secondary antibodies labeled with fluorescent tags. Analysis with an 18-color SORP sorter (BD FACSAria II) detected virions at 80 per ml, with optimal detector positioning for labeled virus particles, facilitating binding studies and detection limits via antibody titration against known virion concentrations.
Other Fluorescence Techniques
Additional techniques include FRET-based platforms, as noted in "Studying SARS-CoV-2 with Fluorescence Microscopy"
. Chen et al. developed a FRET-based platform for screening inhibitors against TMPRSS2 protease activity, measuring disruption of FRET between green and red fluorescent proteins conjugated with a substrate peptide corresponding to the spike protein cleavage site. This method identified Flupirtine as a promising inhibitor, focusing on enzymatic activity rather than direct detection but relevant for understanding spike protein interactions.
Summary Table of Fluorescence Detection Methods
To organize the findings, the following table summarizes the key methods, their targets, sensitivities, and detection times where available:
Method
Target
Sensitivity/LOD
Detection Time
References/URLs
Intrinsic Fluorescence Studies
Spike S1, RBD
Not specified, spectral data provided
Not specified
Fluorescence signatures of SARS-CoV-2 spike S1 proteins
Immunofluorescence
Spike protein
Not specified
Real-time
Studying SARS-CoV-2 with Fluorescence Microscopy
Fusion with Fluorescent Proteins
Spike protein
Not specified
Real-time
Generation and characterization of recombinant SARS-CoV-2
Quantum Dots
Spike-ACE2 binding
Not specified
Not specified
Studying SARS-CoV-2 with Fluorescence Microscopy
Fluorescent VLPs
Spike incorporation
27 ± 12% in M(GFP)NES VLPs
Not specified
Optimized production and fluorescent labeling of SARS-CoV-2 VLPs
SR-DFC Strategy
Spike protein
High, reduces false positives
Not specified
Highly accurate detection of SARS-CoV-2 using SR-DFC
Carbon Nanotube Nanosensors
Spike protein
2-fold fluorescence increase, 73% turn-on
Within 90 min, 5s
Rapid SARS-CoV-2 Spike Protein Detection by Nanosensors
Dual-Signal Imaging (FL+ECL)
Spike protein
Single-molecule level, high sensitivity
Not specified
Dual-Signal Imaging Mode for Spike Protein
Flow Virometry
Spike on virus particles
80 virions/ml
Real-time
Flow virometry for SARS-CoV-2 detection
FRET-Based Platforms
Spike cleavage site
Not specified, for inhibitor screening
Not specified
Studying SARS-CoV-2 with Fluorescence Microscopy
This table encapsulates the diversity of approaches, highlighting their applicability in research and diagnostics, with specific sensitivities and detection times where quantifiable.
Conclusion
The efforts to detect fluorescence of the SARS-CoV-2 spike protein are multifaceted, ranging from fundamental studies of intrinsic fluorescence to advanced biosensor technologies. These methods not only enhance our understanding of viral mechanisms but also support diagnostic and therapeutic development, with ongoing research likely to refine these techniques further.
Key Citations