US scientists have developed synthetic red blood cells that mimic the softness, flexibility and oxygen carrying-property of natural red blood cells, and can be used to deliver drugs and diagnostic agents.
The researchers behind the development are from the University of California, Santa Barbara (UCSB) and the University of Michigan and have published a paper about it in the 22 December print issue of the Proceedings of the National Academy of Sciences.
They write in their background information that while synthetic carriers have brought many advances in drug delivery, they don’t match the sophistication of natural biological materials such as red blood cells (RBCs).
RBCs are the most prolific type of cell in human blood, and are highly specialized: they have a unique shape, size and composition and they are mechanically flexible, properties that optimize them for “extraordinary biological performance”.
The primary role of natural red blood cells is to carry oxygen, and the researchers reported that the new synthetic red blood cells (sRBCs) do that very well, retaining 90 per cent of their oxygen-binding capacity after a week.
However, the sRBCs also “deliver therapeutic drugs effectively and with controlled release”, and “carry well-distributed contrast agents for enhanced resolution in diagnostic imaging”, according to a recent press release from UCSB.
Co-author Dr Samir Mitragotri, who is professor of chemical engineering at UCSB and leader of the research group working on drug delivery synthetic materials, told the media that:
“This ability to create flexible biomimetic carriers for therapeutic and diagnostic agents really opens up a whole new realm of possibilities in drug delivery and similar applications.”
“We know that we can further engineer sRBCs to carry additional therapeutic agents, both encapsulated in the sRBC and on its surface,” he added.
For the study, Mitragotri and colleagues synthesized the particles by making polymer templates shaped like tiny doughnuts, coating them with up to nine layers of hemoglobin and other proteins, then removing the core templates, leaving particles of the same size (about 5 microns in diameter), shape and flexibility, and able to carry as much oxygen, as natural red blood cells.
However, it is their flexibility that makes these new sRBCs stand apart from “conventional” polymer-based biomaterials developed as carriers for therapeutic and diagnostic agents, said the researchers. This enhanced flexibility means the sRBCs can enter and flow through channels that are smaller than their resting diameter, stretch in response to flow, and become disc-shaped again when they exit, just like natural RBCs.
The researchers said that the techniques they use to make sRBCs could also be used to make particles that mimic the shape and function of diseased cells, such as those that occur in inherited blood disorders like sickle-cell anemia and hereditary elliptocytosis, and thus aid the understanding of these diseases.
“Red blood cell-mimicking synthetic biomaterial particles.”
Nishit Doshi, Alisar S. Zahr, Srijanani Bhaskar, Joerg Lahann, and Samir Mitragotri.
PNAS December 22, 2009 vol. 106 no. 51 21495-21499
Published online before print December 14, 2009
DOI: 10.1073/pnas.0907127106
Source: University of California Santa Barbara.
Written by: Catharine Paddock, PhD