Quantitative cell bioimaging using gold-nanoshell conjugates and phage antibodies.

Area of Science:

• Nanotechnology
• Biomedical Imaging
• Cell Biology

Background:

• Plasmon-resonant nanoparticles offer unique optical properties for bioimaging.
• Dark-field microscopy is a sensitive technique for visualizing unstained samples.
• Quantitative assessment of nanoparticle-cell binding is crucial for diagnostic applications.

Purpose of the Study:

• To quantitatively evaluate the efficacy of cell labeling using plasmon-resonant nanoparticles as contrast agents.
• To introduce and validate a novel metric, the labeling-efficacy factor (LEF), for quantifying nanoparticle binding.
• To differentiate between biospecifically and nonspecifically labeled cells using this method.

Main Methods:

• Utilized pig embryo kidney (SPEV) cells for experimental modeling.
• Employed biospecific labeling with primary phage antibodies and secondary antibody-nanoparticle conjugates.
• Developed an imaging-analysis algorithm in ImageJ to calculate the labeling-efficacy factor (LEF).
• Visualized labeled cells using dark-field microscopy with silica/gold nanoshells.

Main Results:

• Introduced the labeling-efficacy factor (LEF) as the ratio of bound-particle pixels per cell to total cell pixels.
• Demonstrated a distinct difference in LEF values between intact, nonspecifically labeled, and biospecifically labeled cells.
• Validated the quantitative assessment of nanoparticle binding efficacy.

Conclusions:

• The developed LEF metric accurately quantifies cell labeling efficiency with nanoparticles.
• Biospecific labeling provides a clear, quantifiable signal distinct from non-specific binding.
• This method enhances the reliability of nanoparticle-based contrast agents in dark-field microscopy for cell analysis.