Target-sensitive immunoerythrocytes: interaction of biotinylated red blood cells with immobilized avidin induces their lysis by complement

Abstract

Red blood cells (RBC) coated with antibody (immunoerythrocytes) may be useful for drug targeting. Previously we have developed a methodology for avidin (streptavidin)-mediated attachment of biotinylated antibodies (b-Ab) to biotinylated RBC (B-RBC). We have observed that binding of avidin to B-RBC in suspension leads to their complement-mediated lysis by autologous serum. In the present work we have studied the interaction of B-RBC, which are not complement susceptible, with immobilized avidin and their consequent susceptibility to lysis by complement. B-RBC adhered tightly to avidin-coated surfaces and were rendered susceptible to lysis by autologous serum. A long biotin ester provided more effective binding of the B-RBC to immobilized avidin and greater lysis by complement, than a short biotin ester. Based on these results, we have hypothesized that targeting of serum-stable drug-loaded B-RBC attained by step-wise administration of b-Ab and streptavidin may provide target-sensitive lysis of B-RBC. To confirm this hypothesis, we have studied b-Ab and streptavidin mediated targeting of B-RBC to immobilized antigen. Step-wise addition of biotinylated antibody, avidin or streptavidin and b-RBC caused specific binding of B-RBC to immobilized antigen and their subsequent lysis by autologous serum. Therefore, our results obtained in an in vitro model demonstrate that B-RBC might be used for targeting and local release of drug.

Drug delivery by red blood cells: vascular carriers designed by mother nature

“…Methods of electrical insertion and hypotonic RBC loading followed by resealing provided encapsulation of diverse agents including antibiotics, steroids, anti-microbial agents, proteins and genetic materials into RBC with loading efficacy ranging from reasonable to fair and to excellent (10% to 30% and to 70%, respectively) of drugs retaining their functional activity22–24. In vitro studies showed that encapsulated agents can be released from RBC either slowly (e.g., via diffusion through RBC plasma membrane25 and/or its eventual degradation)13,26, or rapidly (e.g., via lysis of carrier RBC by plasma complement)27,28. Early studies also showed that RBC carriers facilitated intracellular delivery of encapsulated agents including proteins and DNA into cells in culture21.…”

“…On the other hand, surface coupling strategies avoid damaging encapsulation procedures and therefore offer theoretical advantages of drug loading without compromising RBC biocompatibility. In addition, coupling of drugs to RBC surface circumvents issues related to drug release (approaches to trigger drug release by using controlled lysis by complement have been suggested, yet practically useful controlled release from carrier RBC remains an elusive goal)28. Of note, coupling to RBC surface resolves diffusional limitations: even enzymes that react with small, membrane permeable substrate are more active when bound to the RBC surface than when incorporated within the cell145.…”

Delivery of Drugs Bound to erythrocytes: New Avenues for an Old Intravascular Carrier

“…Coupling drugs to the RBC surface may allow for bypass of damage related to drug encapsulation, minimize RBC elimination and provide other potential advantages. Putting a drug on the RBC surface mitigates issues related to the need for release of drugs encapsulated within RBCs, which is difficult to control [101]. With this approach, the RBC membrane is no longer a barrier for the surface-bound enzymes and other agents.…”

Drug delivery by erythrocytes: “Primum non nocere”

“…Although controlled drug release from mRBC is a very challenging and fascinating goal, these scenarios are more complicated. The concept was introduced decades ago wherein anchoring of affinity-directed carrier RBCs on the target surface caused deformation of the carrier RBCs and enhanced susceptibility to lysis (and resultant release on mRBC content) via activation of the alternative pathway of complement [26]).…”