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Scanning and transmission electron microscopy of biodegradable microspheres (DSM) in blood vessels
Abstract:
A type of biodegradable microsphere (DSM), approximately 45 microns in diameter, made of polymerized potato starch (Pharmacia, Sweden) was intravenously injected into rats to observe the state of DSM in small blood vessels in the kidney and liver at the electron microscopic level. Prior to their digestion with amylase, individual DSM changed their round shape to an irregularly folded one to occupy almost the whole area of the lumen. At the transmission electron microscopic level, DSM were impregnated with colloidal iron and were easily identified. Interaction of the iron labelled DSM with the surface of endothelial cells was unexpectedly loose and no adherence or fusion of this surface was observed. The starch substance was not visible in the pinocytotic vesicles of the endothelium. These findings suggest the independent profile of DSM in situ.
Insights
Biodegradable microspheres (DSM) made of potato starch were injected into rats. These starch microspheres maintained an independent profile within the kidney and liver
Area of Science:
- Biomaterials Science
- Pharmacology
- Microscopy
Background:
- Biodegradable microspheres (DSM) are utilized in various biomedical applications.
- Understanding the in vivo behavior of DSM is crucial for optimizing their therapeutic efficacy and safety.
- Potato starch-based DSM present a novel biomaterial for drug delivery and imaging.
Purpose of the Study:
- To investigate the behavior and interaction of biodegradable microspheres (DSM) within the microvasculature of rat kidneys and livers.
- To characterize the morphological changes and endothelial interactions of starch-based DSM at the electron microscopic level.
Main Methods:
- Intravenous injection of approximately 45-micron diameter polymerized potato starch microspheres (DSM) into rats.
- Transmission electron microscopy was employed to examine DSM within the kidney and liver vasculature.
- Colloidal iron was used for impregnation to enhance DSM identification.
Main Results:
- In situ, DSM deformed from a spherical to an irregularly folded shape, obstructing the vascular lumen.
- Iron-labeled DSM exhibited loose interactions with endothelial cells, with no observed adherence or fusion.
- No evidence of starch substance was found within endothelial pinocytotic vesicles.
Conclusions:
- Biodegradable microspheres (DSM) demonstrate an independent profile within the renal and hepatic microvasculature.
- The observed loose interaction suggests minimal direct cellular uptake or integration of starch-based DSM by endothelial cells.
- These findings provide critical insights into the in vivo behavior of starch-based DSM, informing future biomaterial design.