Visualizing Dose-Dependent Spike Protein Uptake with Quantum Dot Conjugates

Begin with a multi-well plate containing a culture of adherent mammalian cells.

These cells are engineered to express the human angiotensin-converting enzyme 2 receptor, tagged with green fluorescent protein (ACE2-GFP).

Remove the culture medium.

Wash the cells with an imaging medium to eliminate residual culture medium.

Prepare serial dilutions of quantum dot-spike (QD-Spike), in the imaging medium supplemented with a blocking agent to minimize nonspecific binding.

QD-Spike mimics a pseudovirus composed of fluorescent quantum dots conjugated to coronavirus spike proteins.

Add each dilution to a separate well and incubate.

The spike proteins bind specifically to the ACE2-GFP receptors on the host cell membrane.

This interaction triggers receptor-mediated endocytosis, leading to QD-Spike internalization.

After incubation, use confocal imaging to capture intracellular fluorescence signals.

Higher concentrations of QD-Spike produce stronger intracellular fluorescence, confirming concentration-dependent spike binding.

Further, co-localization of QD-Spike with ACE2-GFP confirms receptor-mediated uptake.

To prepare 0.1% BSA, add 130 microliters of 7.5% BSA to 10 milliliters of imaging media in mix.