Abstract
PURPOSE: Nanotechnology-based drug delivery systems (nano-DDS) have been developed to be a promising strategy to improve the efficacy, safety, physicochemical and pharmacokinetic/pharmacodynamics properties of drugs. It is very necessary to elucidate the delivery process in vivo or in cells for the rational design and accurate preparation of nano-DDS. The aim of this study was to construct a nano-DDS to visualize and quantify the intracellular behavior of the loaded cargo and carrier in such a system. METHODS: A carboxyl-terminal end of poly(lactic-co-glycolic acid) polymer was fluorescently labeled with rhodamine B by conjugation of ethylenediamine. Dual-fluorescent nanoparticles (DFPs) were prepared from this fluorescently labeled polymer to encapsulate a fluorescent cargo, coumarin 6. The carrier and cargo of DFPs were monitored by confocal fluorescence microscopy during cellular uptake. Furthermore, the transcellular transportation of DFPs was evaluated quantitatively by measuring the fluorescence intensity. RESULTS: The obtained fluorescent polymer showed stable and quantifiable characteristics. DFPs could be customized in terms of coumarin 6 content (97.7±1.0%), size (367.3±1.7 nm) and dual-emission fluorescence (green cargo and red carrier). DFPs did not significantly affect cell viability, the integrity of cell monolayers and the microscopic morphology at concentrations below 0.7 mg/mL within 3 h of co-incubation with Caco-2 cells. Multichannel fluorescence monitoring revealed that the fluorescence intensity of the carrier and cargo increased with time, but not synchronously. By calculating the residual, intracellular, and transport amounts of DFPs, the material balance between the total amount of cellular transport and the dose administered was obtained. CONCLUSION: Based on the advantages of dual fluorescent labeling, the differential behavior of cell trafficking can be visualized and quantitatively analyzed for the cargo and carrier of DFPs. These results provide insights into the cellular transport process of holistic nanoparticles and complement our understanding of the biological behaviors of nano-DDS.