Red blood cells (RBCs) represent the most commonly used and best-studied natural carriers in the history of drug delivery. Their abundance and long circulation half-life, their great immune-biocompatibility and biodegradability profiles, along with the availability of well established protocols for their safe collection, ex vivo processing and quality control make them advantageous as drug delivery systems (DDS). As a result, several drug-loading techniques (including encapsulation and surface conjugation) have been developed in order to construct RBC-based or RBC-inspired drug delivery vehicles for the effective treatment of infections, cancer, chronic and autoimmune diseases in both pre-clinical protocols and clinical trials. Despite the fact that the collected laboratory (in vitro and in vivo) and clinical data exhibit variable potential for translation into transfusion-associated prototypes and feasible protocols with significant clinical impact, little is known and done in the direction of drug delivery through RBC transfusion. Accordingly, several wandering questions for the application and utility of RBC-based drug delivery in transfusion medicine seek answers. By focusing on the most prominent of them, namely, "why not the stored/transfused RBCs", this review quotes some thoughtful considerations based on the current applications of RBCs as DDS, and on the potential application of RBC-based DDS in transfusion therapy.
Keywords: Drug delivery systems; Extracellular vesicles; Red blood cell-based drug delivery; Red cell storage lesion; Transfusion.
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