Quantification of intracellular payload release from polymersome nanoparticles

Area of Science:

• Biotechnology
• Nanomedicine
• Cell Biology

Background:

• Polymersome nanoparticles (PMs) show promise for controlled drug delivery.
• Limited data exists on the intracellular release kinetics of molecules from membranous nanocarriers like PMs.
• Understanding intracellular release is vital for optimizing nanomedicine efficacy.

Purpose of the Study:

• To develop and validate a quantitative assay for measuring intracellular release from PMs.
• To investigate the real-time cytosolic release of encapsulated molecules at a single-cell level.
• To assess the heterogeneity of nanoparticle uptake and payload delivery in cells.

Main Methods:

• Encapsulation of the hydrophilic dye fluorescein within 85 nm polymersome nanoparticles.
• Development of a quantitative assay combining absorbance measurements and flow cytometry.
• Incubation of L929 cells with fluorescein-loaded PMs and real-time fluorescence monitoring.

Main Results:

• Fluorescein was stably encapsulated in PMs with minimal leakage.
• Intracellular fluorescence increased over time post-incubation, confirming PM disruption and fluorescein release.
• Quantified an average of 173 ± 38 polymersomes releasing payload per cell.
• Observed significant heterogeneity in cellular uptake and payload release, even in synchronized cell cycles.

Conclusions:

• A novel, quantitative assay for measuring intracellular release from PMs was successfully developed.
• The study highlights the stochastic nature of nanoparticle uptake and drug release at the single-cell level.
• Findings provide fundamental insights into nanoparticle-cell interactions, essential for clinical translation of nanomedicine.