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Published on: January 5, 2015
Bioimaging of Intravenous Polymeric Micelles Based on Discrimination of Integral Particles Using an
Haisheng He1, Jian Zhang1,2, Yunchang Xie1
1School of Pharmacy, Fudan University , Key Laboratory of Smart Drug Delivery of MOE and PLA, Shanghai 201203, China.
Abstract:
One of the biggest challenges in bioimaging of nanoparticles is how to identify integral particles from bulk signals of probes. Signals of free probes are always mistakenly counted into total signals of particles. In this study, in vivo fate of intravenous polymeric micelles (PMs, mPEG2.5k-PDLLA2.5k) was explored using a highly sensitive near-infrared environment-responsive fluorescent probe. This probe is able to emit fluorescence when embedded in nanocarriers but quench spontaneously and absolutely upon release into water, based on the aggregation-caused quenching effect, which means that the interference generated by free probes can be completely diminished. Analysis of blood-borne fluorescence reveals rapid clearance of PMs from blood following a tricompartmental pharmacokinetic model. Live imaging shows pervasive distribution of PMs throughout the body, and a tendency of accumulation to extremities with fluorescence density 3-5 times higher than the trunk. Ex vivo examination reveals that most PMs are found in vital organs following an order of lung > liver > spleen > heart > kidney in concentration, but an order of liver > lung > spleen > heart ≈ kidney in total amount. The distribution to other organs and tissues is even lower, and to brain, negligible. It is concluded that the biodistribution of PMs to vital organs and extremities warns of potential toxicity and can be translated to explain the toxicity of its commercial counterpart with similar chain lengths.
Insights
This study developed a novel fluorescent probe to accurately track polymeric micelles (PMs) in vivo. The probe
Area of Science:
- Nanomedicine
- Bioimaging
- Pharmacokinetics
Background:
- Accurate tracking of nanoparticles in vivo is crucial for understanding their fate and potential toxicity.
- Distinguishing signals from intact nanoparticles versus free probes presents a significant challenge in bioimaging.
- Polymeric micelles (PMs) are widely used nanocarriers, but their in vivo behavior requires precise elucidation.
Purpose of the Study:
- To investigate the in vivo biodistribution and fate of intravenous polymeric micelles (PMs).
- To overcome the challenge of distinguishing nanoparticle signals from free probe signals in bioimaging.
- To assess the potential toxicity implications of PMs' distribution patterns.
Main Methods:
- Development and application of a highly sensitive, environment-responsive near-infrared fluorescent probe.
- The probe exhibits aggregation-caused quenching, emitting fluorescence within nanocarriers but quenching when free.
- In vivo tracking using blood-borne fluorescence analysis, live imaging, and ex vivo organ examination.
Main Results:
- Polymeric micelles (PMs) were rapidly cleared from the blood, following a tricompartmental pharmacokinetic model.
- Live imaging revealed widespread distribution with higher accumulation in extremities compared to the trunk.
- Ex vivo analysis showed significant PMs accumulation in vital organs, with concentration varying by organ.
Conclusions:
- The developed fluorescent probe effectively eliminates interference from free probes, enabling accurate nanoparticle tracking.
- The biodistribution of PMs to vital organs and extremities suggests potential toxicity concerns.
- These findings can help explain the toxicity of similar commercial polymeric micelles.
