Charge-driven selective localization of fluorescent nanoparticles in live cells

Area of Science:

• Nanotechnology
• Cell Biology
• Biophysics

Background:

• Fluorescent nanoparticles (SiC NPs) possess surface carboxylic acid functionalities.
• Surface charge is a critical factor influencing nanoparticle-cell interactions.
• Understanding nanoparticle localization is key for targeted drug delivery and imaging.

Purpose of the Study:

• To functionalize SiC NPs to control their surface charge.
• To investigate the effect of SiC NP surface charge on cellular uptake and localization in 3T3-L1 fibroblast cells.
• To explore the potential of charge-tuned SiC NPs as long-term cell imaging agents.

Main Methods:

• Covalent grafting of amino groups onto SiC NPs to modify surface charge from negative to positive.
• Incubation of 3T3-L1 fibroblast cells with differently charged SiC NPs.
• Fluorescence microscopy to observe nanoparticle localization within cells (cytoplasm and nucleus).

Main Results:

• Surface charge modification successfully tuned SiC NPs from negative to highly positive.
• Negatively charged SiC NPs localized within the cell nuclei.
• Neutrally charged SiC NPs were found in both cytoplasm and nuclei.
• Positively charged SiC NPs were confined to the cytoplasm, unable to penetrate the nuclei.
• Interaction with the nuclear pore complex was identified as crucial for nuclear entry.

Conclusions:

• SiC NP surface charge critically determines their intracellular localization.
• Charge-tuned SiC NPs offer a novel tool for selective cell imaging.
• This approach allows for long-term visualization of specific cellular compartments (cytosol or nucleus).
• The nuclear pore complex plays a vital role in regulating nanoparticle nuclear penetration.