Fluorescein Loading of PAA Nanoparticles for TME Release Studies

Authors

• Alexia T. Apablaza, Belmont UniversityFollow
• Rachel Rigsby, Belmont UniversityFollow

Publication Date

2026

College

College of Sciences & Mathematics

Department

Chemistry and Physics, Department of

SURS Faculty Advisor

Dr. Rachel Rigsby

Presentation Type

Poster Presentation

Abstract

pH-responsive nanoparticles are designed to release drugs in the mildly acidic environment of tumors (pH ≈ 6.5) while remaining stable in normal tissue (pH 7.4). In this research, this property will be explored beyond just buffers and will eventually test how upregulated protein and extracellular matrix components found in tumors may impact how these particles perform. The first stage of the project focused on validating a fluorescence-based assay and loading fluorescein into the particles. Fluorescein standard curves were prepared in PBS (pH 7.4) and MES (pH 6.5). Both of the standards (MES and PBS) were highly linear (R² ≥ 0.9988), but fluorescein was only 49% as bright at pH 6.5, which means that each pH condition requires its own standardization. Nanoparticles were formed by combining PAA with fluorescein and sonicating the mixture. Then the particles were isolated by dialysis alongside a free-fluorescein control. The dye that was retained was measured by fluorescence, and particle formation was assessed by light scattering using the fluorometer. After dialysis, only about 0.9% of the fluorescein remained associated with PAA, which was smaller than anticipated. Contrastingly, the free dye in the control was almost completely gone. The retained signal in the nanoparticle sample had the same emission spectrum as fluorescein, confirming that it was fluorescein dye rather than background noise. This low loading is likely due to electrostatic repulsion, since both PAA and fluorescein are negatively charged at pH 7.4. Light scattering increased slightly after dialysis, suggesting some particle formation. These results establish a successful method for nanoparticle formation, but show that loading must be improved before release can be measured. Future work will form particles at lower pH or with calcium crosslinking, then compare release with and without BSA, hyaluronan, and collagen.

Recommended Citation

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