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Updated: Jan 28, 2026

Evaluation of the Storage Stability of Extracellular Vesicles
Published on: May 22, 2019
Novel Approach for Assessment of Dermal Absorption of Extracellular Vesicle Products Using Immunoaffinity Fluorescent
Meng-Chien Willie Hsieh1,2, Yung-Shun Su3, Liang-Yu Chen4
1Division of Plastic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
Introduction:
This study investigates the transdermal permeation efficiency and traceability of fluorescent nanodiamond-conjugated small extracellular vesicles (FND-sEVs) derived from umbilical cord mesenchymal stem cells.
Methods:
First, the sEVs were isolated and characterized using transmission electron microscopy (TEM) and nanoparticle tracking analysis, confirming their typical cup-shaped morphology and size distribution (62.5-141.1 nm) consistent with canonical sEV properties. Subsequently, FNDs were conjugated to sEVs, forming FND-sEVs, whose composite structure - featuring a high-electron-density FND core surrounded by a vesicular sEV membrane - was verified by TEM. Conjugation efficiency was then validated via confocal microscopy, showing complete colocalization between FND fluorescence and Alexa Fluor 488-labeled wheat germ agglutinin-tagged sEVs. Transdermal assessment was conducted using a skin tissue model, with magnetically modulated fluorescence (MMF) spectroscopy applied for background-free quantification.
Results:
Leveraging the unique nitrogen-vacancy centers in FNDs (fluorescence lifetime ∼20 ns), MMF eliminated interference from skin autofluorescence (∼3 ns) and enabled direct quantification in tissue digests without pre-separation. FND-sEVs were discovered to remain predominantly in the supernatant, with a measurable fraction permeating skin tissue layers, while their presence in the filtrate was negligible, thereby indicating limited transdermal passage.
Conclusion:
Collectively, these findings establish FND-sEVs as a traceable platform for transdermal studies and highlight MMF as a robust tool for quantifying nanoscale vesicle distributions in complex biological matrices.
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