Red blood cells (RBCs) are described as our very own shipping system, transporting oxygen from the lungs to the body’s tissues. Biological RBCs are extremely flexible, squeezing through tiny spaces and tubes without permanent damage, and contain proteins on their surface making them invisible to the immune system when there is no pathology present.
RBCs have been widely used in drug delivery systems due to their level of abundance in the blood, their biocompatibility, biodegradability, and expanded length of time in the circulatory system.
The most commonly used method to achieve these controlled release systems consists of RBC membranes acting as a camouflage for functional nanoparticles, conferring biocompatibility. To date, however, artificial RBCs have only achieved some, not all, of the innate features belonging to organic blood cells, including flexibility, oxygen transport, and long circulation times.
Biomimetic artificial blood
Now, a study from researchers led by the University of New Mexico engineers biomimetic synthetic RBCs possessing all of their natural counterpart’s abilities, plus multiple artificial components. The team states their fabricated RBCs were each given the ability to transport cargos including hemoglobin, drugs, magnetic nanoparticles, and biosensors to enable alien functions, such as oxygen transportation, drug delivery, magnetic manipulation, and toxin detection. The study is published in the journal ACS Nano.
Previous studies show compared to standard oral therapeutics, drugs on the nanoscale level, such as nanoparticles, are characterized by low toxicity, higher drug release efficiency, great biocompatibility, and higher blood circulation times. Despite this, suitability problems arise due to the fact nanoparticles are often released early or captured by the immune system, with overdosage to compensate for bulk losses known to cause side effects.
Therefore, cloaking nanoparticles with RBC membranes is a proven strategy to impart indigenous characteristics, however, challenges remain in the quality control of large batches, with contamination and lack of designated task differentiation often cited. The current study assembles artificial RBCs with inborn properties and the capability to perform unfamiliar actions such as cargo delivery, magnetic targeting, and toxin detection.
The current study constructs synthetic RBCs using donated human blood and nanoparticles possessing varying capabilities. The human RBCs were first coated with a thin layer of silica, then layered with positively and negatively charged polymers to impart hydrophilic properties to add structural stability to the artificial cell.
Flexibility is then conferred to the replicas by etching the silica coating, which serves as a retaining bed for the final layer of natural RBC membranes. Results show the imitation cells possessed the same surface proteins whilst being similar in size, shape, and charge to natural cells, and were able to squeeze through model capillaries without any lasting malformation.
Synthetic blood with extras
The lab states the biomimetic RBCs circulated for more than 48 hours after being injected into mice and exhibited no observable toxicity. They go on to add their simulant blood cells also demonstrate the ability to carry cargoes consisting of either hemoglobin, an anticancer drug, a toxin sensor, or magnetic nanoparticles. This also led to the observation the engineered RBCs can act as decoys for a bacterial toxin.
The team surmises they successfully designed and trialed a long-circulating artificial cell possessing a broad range of potential applications. For the future, the researchers state, they now plan to evaluate the potential of their synthetic cells in treating cancer or as an in vivo diagnostic.
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