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Improving vascular retention of indocyanine green for in vivo two-photon microscopy using liposomal encapsulation
Alankrit Tomar1, Noah Stern2, Tyrone Porter2
1The University of Texas at Austin, Department of Electrical and Computer Engineering, Austin, Texas, United States.
Significance:
Two-photon microscopy is widely used for in vivo imaging of vasculature in rodents and requires the labeling of blood plasma with fluorescent dyes such as indocyanine green (ICG). However, a major limitation of ICG is its rapid clearance from the body, which restricts its use in extended imaging sessions. We address and overcome that limitation, enabling longer in vivo imaging sessions.
Aim:
We aim to investigate the feasibility of using liposomal nanoparticles that, when used to encapsulate ICG, significantly increase the circulation time of the vascular label in the rodent body.
Approach:
We conducted in vivo imaging experiments with unencapsulated (free) ICG and liposomal ICG (L-ICG) and compared the retention of ICG in the vascular network over a duration of 75 min.
Results:
In comparison to a retention time of around 20 min for free ICG, we find that liposomal encapsulation improves the vascular retention time of the dye to at least 75 min. The improvement in retention time using the encapsulation technique was consistent across imaging experiments conducted in five mice.
Conclusion:
The rapid clearance of ICG from the rodent body can be overcome using liposomal encapsulation, making prolonged in vivo imaging feasible.
Insights
Liposomal encapsulation extends indocyanine green (ICG) circulation time for extended in vivo imaging. This overcomes ICG
Area of Science:
- Biomedical Imaging
- Nanotechnology
- Pharmacology
Background:
- Two-photon microscopy is vital for in vivo rodent vasculature imaging.
- Indocyanine green (ICG) is a common fluorescent dye for vascular labeling.
- ICG's rapid clearance limits its use in prolonged imaging sessions.
Purpose of the Study:
- To investigate liposomal nanoparticles for encapsulating ICG.
- To enhance ICG's circulation time and vascular retention in rodents.
- To enable extended in vivo imaging sessions.
Main Methods:
- In vivo imaging experiments were performed in mice.
- Compared vascular retention of free ICG versus liposomal ICG (L-ICG).
- Evaluated retention over a 75-minute duration.
Main Results:
- Liposomal encapsulation significantly increased ICG vascular retention time.
- L-ICG retention lasted at least 75 minutes, compared to ~20 minutes for free ICG.
- Consistent retention improvement observed across multiple mice.
Conclusions:
- Liposomal encapsulation effectively overcomes rapid ICG clearance.
- This technique makes prolonged in vivo imaging feasible.
- Enhanced vascular labeling improves imaging capabilities.
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