Deep-hole array structure for highly sensitive fluorescence imaging of cells via inverted microscopy

Area of Science:

• Plasmonics
• Nanotechnology
• Biomedical Imaging

Background:

• Inverted fluorescence microscopy is ideal for studying cell membranes at interfaces.
• Surface-plasmon-mediated fluorescence enhancement is hindered by reduced light transmittance in conventional nanostructures.
• Homogeneous fluorescence enhancement is crucial for high-sensitivity, wide-field imaging.

Purpose of the Study:

• To develop a plasmonic chip with a deep-hole array (DHA) structure for enhanced fluorescence.
• To overcome limitations of reduced light transmittance in conventional nanostructures for inverted microscopy.
• To enable highly sensitive detection of targets, including cell membrane proteins and nanoparticles.

Main Methods:

• Fabrication of a periodic plasmonic chip with a deep-hole array (DHA) structure (422 nm depth).
• Characterization of optical transmittance and fluorescence enhancement compared to conventional structures.
• Imaging of fluorescent particles (0.2 µm) and breast cancer cells labeled with APC-EpCAM antibodies.

Main Results:

• The DHA structure significantly increased optical transmittance (>50-fold) compared to conventional hole arrays.
• A ~70-fold increase in fluorescence intensity was observed for 0.2 µm fluorescent particles.
• Cell membrane proteins (EpCAMs) on breast cancer cells, previously indiscernible, were clearly detected with high sensitivity.

Conclusions:

• The DHA plasmonic chip effectively enhances fluorescence and overcomes light transmittance issues.
• This technology provides a powerful platform for highly sensitive fluorescence detection.
• Potential applications include single-nanoparticle analysis and advanced cellular bioimaging.