Erythrocyte-based drug delivery in Transfusion Medicine: Wandering questions seeking answers

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.     

Encapsulation of FITC to monitor extracellular pH: a step towards the development of red blood cells as circulating blood analyte biosensors

A need exists for a long-term, minimally-invasive system to monitor blood analytes. For certain analytes, such as glucose in the case of diabetics, a continuous system would help reduce complications. Current methods suffer significant drawbacks, such as low patient compliance for the finger stick test or short lifetime (i.e., 3-7 days) and required calibrations for continuous glucose monitors. Red blood cells (RBCs) are potential biocompatible carriers of sensing assays for long-term monitoring. We demonstrate that RBCs can be loaded with an analyte-sensitive fluorescent dye. In the current study, FITC, a pH-sensitive fluorescent dye, is encapsulated within resealed red cell ghosts. Intracellular FITC reports on extracellular pH: fluorescence intensity increases as extracellular pH increases because the RBC rapidly equilibrates to the pH of the external environment through the chloride-bicarbonate exchanger. The resealed ghost sensors exhibit an excellent ability to reversibly track pH over the physiological pH range with a resolution down to 0.014 pH unit. Dye loading efficiency varies from 30% to 80%. Although complete loading is ideal, it is not necessary, as the fluorescence signal is an integration of all resealed ghosts within the excitation volume. The resealed ghosts could serve as a long-term (>1 to 2 months), continuous, circulating biosensor for the management of diseases, such as diabetes.     

Comparison of frozen versus desiccated reference human red blood cells for hemagglutination assays

BACKGROUND: Red blood cells (RBCs) are commonly used fresh or stored in frozen format for identification of patients' antibodies and serologic specificity of such antibodies at reference laboratories. However, maintaining a large pool of fresh RBCs is impossible in a blood-banking environment and blood in frozen format poses a logistic disadvantage in terms of accessibility, maintenance cost, safety, and sample recovery. This study explores an alternative, desiccation storage method for RBCs to provide a reagent that supports greater utilization and flexibility for reference laboratories.
STUDY DESIGN AND METHODS: RBCs from five donors were used in the study. RBCs were processed and kept in either frozen or desiccated format. Study variables for either the frozen or the desiccated cells included cell recovery as quantified by cell counts, gross microscopic examination, and hemagglutination assays.
RESULTS: The mean percentage of cell recovery for thawed and washed frozen RBCs was 20% versus 50% for rehydrated and washed desiccated RBCs. Microscopic examination of thawed cells from the frozen preparation showed cells with irregular shapes, a sharp contrast when compared with rehydrated cells from the desiccated preparation, where cells are mostly intact, smooth surface, and biconcave in structure. Cells in both preparations performed well in manual agglutination tests.
CONCLUSION: Desiccation preservation of RBCs provides a somewhat better RBC recovery and cell structure stability, while maintaining the necessary antigen-antibody reactions for cell surface markers, which will allow desiccated RBCs to be archived in blood collecting and processing reference laboratories.     

Clinical consequences of red cell storage in the critically ill

Red cell (RBC) transfusions are a potentially life-saving therapy employed during the care of many critically ill patients to replace losses in hemoglobin to maintain oxygen delivery to vital organs. During storage, RBCs undergo a series of biochemical and biomechanical changes that reduce their survival and function. Additionally, accumulation of other biologic by-products of RBC preservation may be detrimental to recipients of blood transfusions. Laboratory studies and an increasing number of observational studies have raised the possibility that prolonged RBC storage adversely affects clinical outcomes. In this article, the laboratory and animal experiments evaluating changes to RBCs during prolonged storage are reviewed. Subsequently, the clinical studies that have evaluated the clinical consequences of prolonged RBC storage are reviewed. These data suggest a possible detrimental clinical effect associated with the transfusion of stored RBCs; randomized clinical trials further evaluating the clinical consequences of transfusing older stored RBCs are required.     

Immunosuppressive effects of red blood cells on monocytes are related to both storage time and storage solution

BACKGROUND: Reduced monocyte function is associated with adverse outcomes from critical illness. Red blood cells (RBCs) are thought to impair monocyte function but relationships between RBC storage solution and monocyte suppression are unknown. This study was designed to test the hypothesis that immunosuppressive effects of RBCs on monocytes are related to both storage time and preservative solution. STUDY DESIGN AND METHODS: Monocytes from healthy adult donors were co‐cultured with RBCs that had been stored in AS‐1, AS‐3, or CPD only for 7, 14, or 21 days. Cells were then stimulated with lipopolysaccharide (LPS) and their supernatants assayed for tumor necrosis factor (TNF)‐α and interleukin (IL)‐10. Transwell experiments were performed to evaluate the role of cell‐to‐cell contact. Monocyte mRNA expression was quantified by real‐time–polymerase chain reaction. RESULTS: LPS‐induced TNF‐α production capacity was reduced compared to controls for all groups, but CPD‐only RBCs suppressed monocyte function more than RBCs stored in AS‐1 (p = 0.007) and AS‐3 (p = 0.006). IL‐10 production was preserved or augmented in all groups. A longer storage time was associated with reduced TNF‐α production capacity for AS‐1 and AS‐3 groups but not CPD. Preventing cell‐to‐cell contact did not eliminate the inhibitory effect of RBCs on monocyte responsiveness. RBC exposure was associated with decreased LPS‐induced TNFA mRNA expression (p < 0.05 for all groups). CONCLUSIONS: CPD‐only RBCs suppressed monocyte function more than RBCs stored with additive solutions. TNF‐α production was reduced even in the absence of cell‐to‐cell contact and was impaired at the mRNA level. Further work is needed to understand the role of preservative solutions in this process.     

Banking of pluripotent adult stem cells as an unlimited source for red blood cell production: potential applications for alloimmunized patients and rare blood challenges

The transfusion of red blood cells (RBCs) is now considered a well-settled and essential therapy. However, some difficulties and constraints still occur, such as long-term blood product shortage, blood donor population aging, known and yet unknown transfusion-transmitted infectious agents, growing cost of the transfusion supply chain management, and the inescapable blood group polymorphism barrier. Red blood cells can be now cultured in vitro from human hematopoietic, human embryonic, or human-induced pluripotent stem cells (hiPSCs). The highly promising hiPSC technology represents a potentially unlimited source of RBCs and opens the door to the revolutionary development of a new generation of allogeneic transfusion products. Assuming that in vitro large-scale cultured RBC production efficiently operates in the near future, we draw here some futuristic but realistic scenarios regarding potential applications for alloimmunized patients and those with a rare blood group. We retrospectively studied a cohort of 16,486 consecutive alloimmunized patients (10-year period), showing 1 to 7 alloantibodies with 361 different antibody combinations. We showed that only 3 hiPSC clones would be sufficient to match more than 99% of the 16,486 patients in need of RBC transfusions. The study of the French National Registry of People with a Rare Blood Phenotype/Genotype (10-year period) shows that 15 hiPSC clones would cover 100% of the needs in patients of white ancestry. In addition, one single hiPSC clone would meet 73% of the needs in alloimmunized patients with sickle cell disease for whom rare cryopreserved RBC units were required. As a result, we consider that a very limited number of RBC clones would be able to not only provide for the need for most alloimmunized patients and those with a rare blood group but also efficiently allow for a policy for alloimmunization prevention in multiply transfused patients.     

Concanavalin A-mediated binding and sphering of human red blood cells by homologous monocytes

Human red blood cells sensitized with concanavalin A became bound to homologous peripheral blood monocytes. Binding occured at a concentration of 10(5) molecules of tetrameric Con A per red blood cell (RBC) and increased with additional Con A. RBC binding began within 5 min and was maximal at 90 min. Phagocytosis of sensitized RBCs was minimal. RBC attachment was prevented by 0.01 M alpha-methyl-D- mannopyranoside, and, once the RBC-monocyte rosette was established, bound RBCs were largely removed with this specific saccharide inhibitor of Con A. RBCs attached to monocytes became spherocytic and osmotically fragile. The recognition of concanavalin A (Con A)-coated RBCs was not mediated through the monocyte IgG-Fc receptor. These studies demonstrate that, like IgG and C3b, Con A is capable of mediating the binding of human RBCs to human monocytes. Red cells so bound are damaged at the monocyte surface.     

Expression of CD47 (integrin-associated protein) decreases on red blood cells during storage.

In light of recent studies that demonstrate that CD47 antigen is an important "self-recognition" marker involved in protecting circulating red blood cells (RBCs) from phagocytosis by macrophages, the aim of the present study was to investigate whether CD47 expression on RBCs is altered during storage. Red cell concentrates (RCCs) were prepared and stored at 4 degrees C and samples were collected on days 1, 14, 28 and 42 post donation. RBCs were labelled with anti-CD47 antibody and analysed by flow cytometry. A small but significant and progressive decrease in CD47 antigen expression was observed in non-irradiated and irradiated RBCs stored for 14 days onwards. CD47 was also detected in increasing quantities in supernatant from RCCs after 14 days of storage. It is proposed that loss of CD47 during storage, in addition to other biophysical changes, may target many transfused RBCs for clearance from the transfusion recipient's circulation.     

Encapsulated ultrasound microbubbles: therapeutic application in drug/gene delivery.

Encapsulated gas microbubbles are well known as ultrasound contrast agents for medical ultrasound imaging. Nonetheless, not only do these microbubbles help to image, but they can also be used as drug/gene carriers. The microbubbles as drug/gene carriers have an average size less than that of red blood cells, i.e. they are capable of penetrating even into the small blood capillaries and releasing drug and genes under the action of ultrasound field. The application of ultrasound and microbubbles to targeted drug and gene delivery has been the subject of intense experimental research. Under exposure of sufficiently high-amplitude ultrasound, these targeted microbubbles would rupture, spewing drugs or genes, which are contained in its encapsulating layer, to targeted cells or tissues. Recently, targeting ligands are attached to the surface of the microbubbles (i.e. targeted-microbubbles), which have been widely used in cardiovascular system and tumor diagnosis and therapy. In this paper, the characterization of novel targeted ultrasonic contrast agents or microbubbles and their potential applications in drug delivery or gene therapy are reviewed.     

Measurement of Red Cell Lifespan and Aging

Summary

The measurement of red blood cell (RBC) survival has a long history, and a wide variety of methods have been utilized for this purpose. Current methods are of 2 types. First, those that label a representative sample of RBCs of all ages from the blood and then measure their rate of disappearance upon reinfusion. This category includes the ⁵¹Cr and biotin labels. Second, those that use a metabolic precursor or product to determine the turnover of hemoglobin. Examples of these are carbon monoxide production and incorporation of labeled glycine. Recent studies with the covalent, nonradioactive biotin label show its unique suitability for both the accurate measurement of red cell survival and the determination of changes in red cell properties as they age in vivo.KeyWords: Red cell lifespan, Chromium, Biotin, Red cell senescence, Red cell aging     

Combined use of nifedipine and diltiazem for the treatment of severe hypertension

Calcium channel blockers are a heterogeneous group of drugs that have enhanced our ability to concurrently control blood pressure, treat coronary artery disease, and avoid many of the side effects of previously available antihypertensive agents. Patients with severe hypertension may require multiple agents for adequate control of blood pressure because of either poor control with one agent or side effects from high doses of a single agent. Laboratory investigations have shown a synergistic effect on receptor binding, as well as increased drug levels with the concurrent use of diltiazem and a dihydropyridine calcium channel blocker (nifedipine or nicardipine). It is as yet unknown whether these effects on receptor binding and increased drug levels translate into greater clinical efficacy in blood pressure control. We have reported what we believe to be the first case in which this interaction was used successfully to control previously poorly controlled hypertension, while minimizing side effects.     

Drug delivery in poly(lactide-co-glycolide) nanoparticles surface modified with poloxamer 407 and poloxamine 908: in vitro characterisation and in vivo evaluation

Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles of 150-nm mean size were produced by an interfacial deposition method. The polar model drug Rose Bengal was successfully loaded into the nanoparticles during production and the surface of these particles was subsequently modified with poloxamer 407 and poloxamine 908 in order to create a steric stabilising layer of PEG on the surface. Drug loading was low (<1%) which can be attributed to the polar nature of the drug and the small size of the nanoparticles. Drug release was biphasic with 50% release measured within 30 min in serum. After intravenous injection in rats, the drug loaded nanoparticles substantially avoided capture by the Kupffer cells of the liver as compared to free drug. The half-life of Rose Bengal in the blood stream when administered in the nanoparticles was greatly extended with approximately 30% remaining after 1 h as compared to only 8% of Rose Bengal left 5 min after administration in solution. These surface modified nanoparticles would have potential as carriers for drugs to specific sites within the body or for slow release of drug within the circulation.     

Targeted nanogels: a versatile platform for drug delivery to tumors

Although nanoparticle-based drug delivery formulations can improve the effectiveness and safety of certain anticancer drugs, many drugs, due to their chemical composition, are unsuitable for nanoparticle loading. Here, we describe a targeted nanogel drug delivery platform that can (i) encapsulate a wide range of drug chemotypes, including biological, small molecule, and cytotoxic agents; (ii) display targeting ligands and polymeric coatings on the surface; (iii) enhance drug retention within the nanogel core after photo-cross-linking; and (iv) retain therapeutic activity after lyophilization allowing for long-term storage. For therapeutic studies, we used integrin αvβ3-targeted lipid-coated nanogels with cross-linked human serum albumin in the core for carrying therapeutic cargoes. These particles exhibited potent activity in tumor cell viability assays with drugs of distinct chemotype, including paclitaxel, docetaxel, bortezomib, 17-AAG, sorafenib, sunitinib, bosutinib, and dasatinib. Treatment of orthotopic breast and pancreas tumors in mice with taxane-loaded nanogels produced a 15-fold improvement in antitumor activity relative to Abraxane by blocking both primary tumor growth and spontaneous metastasis. With a modifiable surface and core, the lipid-coated nanogel represents a platform technology that can be easily adapted for specific drug delivery applications to treat a wide range of malignant diseases.     

Bacterial ghosts as carrier and targeting systems

Bacterial ghosts are empty cell envelopes originating from Gram-negative bacteria. They have a natural outer surface make-up which provides them with the original targeting functions of the bacteria they are derived from and are thus able to bind to and/or are taken up by specific cells or tissues of animal, human or plant origin. The extended bacterial ghost system represents a platform technology for creating new qualities in non-living carriers which can be used for the specific targeting of drugs, DNA or other compounds to overcome toxic or non-desired obstacles. Freeze dried bacterial ghosts are stable without the requirement of a cold chain and can be effectively administered orally and aerogenically as drug carriers. The new system is an alternative to liposomes and may have an advantage due to its higher specificity for targeting specific tissues, its easy method of production and its versatility in entrapping and packaging various compounds in different compartments of the carriers.     

Red blood cell preservation by droplet freezing with polyvinylpyrrolidone or sucrose-dextrose and by bulk freezing with glycerol

BACKGROUND: Red blood cell (RBC) preservation is essential to transfusion medicine. Many blood group reference laboratories need a method to preserve rare blood samples for serologic testing at a later date. This study offers a comparison of three common cryoprotective agents and protocols used today: bulk preservation with glycerol and droplet freezing with sucrose‐dextrose (S+D) or polyvinylpyrrolidone (PVP). STUDY DESIGN AND METHODS: Human blood from 14 volunteers was collected and frozen at set intervals over 2 weeks with PVP, S+D, or glycerol. The frozen RBCs were later thawed and the percentage of surviving RBCs was determined. Detailed protocols and an instructional video are supplied. RESULTS: Over a 2‐week period, RBCs preserved with glycerol and thawed with a widely used protocol showed a recovery of 41 ± 16% (mean ± standard deviation) while those thawed with a modified glycerol protocol showed a recovery of 76 ± 8%. RBCs preserved by droplet freezing with S+D showed a recovery of 56 ± 11% while those preserved by droplet freezing with PVP showed a recovery of 85 ± 6%. Recovery values were similar with ethylenediaminetetraacetic acid or heparin anticoagulants, differing freezing rates, and varying droplet volumes. CONCLUSION: Droplet freezing with PVP offered the greatest recovery. While bulk freezing with glycerol can also be effective, droplet freezing may be a more convenient method overall. It requires less effort to thaw, needs much less storage room, and allows blood group laboratories to be frugal with thawing rare samples.     

二甲基亚砜在人红细胞冻干前负载海藻糖过程中的作用

目的研究人红细胞冻干保存前负载海藻糖过程中二甲基亚砜(DMSO)的作用,优化红细胞负载缓冲液配方。方法实验组以浓缩红细胞25份(10ml/份)负载海藻糖,负载缓冲液中添加DMSO;对照组25份负载海藻糖,负载缓冲液中未添加DMSO。37℃条件下孵育8h后,分别检测两组红细胞胞内海藻糖负载量、胞外游离血红蛋白水平、ATP含量、红细胞变形性,并利用流式细胞术检测负载后红细胞膜的完整性。结果实验组与对照组红细胞的胞内海藻糖负载量分别为(57.033±4.883)mmol/L,(49.184±4.858)mmol/L(P<0.05);胞外游离血红蛋白浓度分别为(4.131±0.473)g/L,(5.410±0.501)g/L(P<0.05);ATP浓度分别为(3.874±0.426)μmol/g Hb,(3.358±0.306)μmol/g Hb(P<0.05);红细胞变形指数分别为0.330±0.0211,0.277±0.0232(P<0.01);红细胞胞膜PS表达率分别为(5.04±0.495)%,(8.69±0.862)%(P<0.01)。结论DMSO在红细胞负载海藻糖过程中可有效增加胞内海藻糖负载量,并显著改善负载缓冲液对红细胞胞膜的高渗损伤,更好地发挥海藻糖对红细胞的保护作用。     

IMMUNOHEMATOLOGY: Storage of murine red blood cells enhances alloantibody responses to an erythroid‐specific model antigen

BACKGROUND: Red blood cell (RBC) alloimmunization can be a serious complication of blood transfusion, but factors influencing the development of alloantibodies are only partially understood. Within FDA‐approved time limits, RBCs are generally transfused without regard to length of storage. However, recent studies have raised concerns that RBCs stored for more than 14 days have altered biologic properties that may affect medical outcomes. To test the hypothesis that storage time alters RBC immunogenicity, we utilized a murine model of RBC storage and alloimmunization. STUDY DESIGN AND METHODS: Blood from transgenic HOD donor mice, which express a model antigen (hen egg lysozyme [HEL]) specifically on RBCs, was filter leukoreduced and stored for 14 days under conditions similar to those used for human RBCs. Fresh or 14‐day‐stored RBCs were transfused into wild‐type recipients. The stability of the HOD antigen and posttransfusion RBC survival were analyzed by flow cytometry. RBC alloimmunization was monitored by measuring circulating anti‐HEL immunoglobulin levels. RESULTS: Transfusion of 14‐day‐stored, leukoreduced HOD RBCs resulted in 10‐ to 100‐fold higher levels of anti‐HEL alloantibodies as detected by enzyme‐linked immunosorbent assay than transfusion of freshly collected, leukoreduced RBCs. RBC expression of the HOD antigen was stable during storage. CONCLUSIONS: These findings demonstrate that HOD murine RBCs become more immunogenic with storage and generate the rationale for clinical trials to test if the same phenomenon is observed in humans. Length of storage of RBCs may represent a previously unappreciated variable in whether or not a transfusion recipient becomes alloimmunized.     

Transfusion support for patients with sickle cell disease

Red blood cell (RBC) transfusion is an essential treatment for many patients with sickle cell disease (SCD), whose RBCs express hemoglobin S (HbS), a mutated form of hemoglobin A (HbA). Transfusion goals include increasing blood oxygen carrying capacity and decreasing the relative amount of HbS to HbA to mitigate vaso-occlusion in small blood vessels. In situations where correction of severe anemia and reduction in HbS may be achieved without removal of RBCs, simple transfusion may be utilized. Partial manual RBC exchange, which removes blood containing HbS by phlebotomy and replaces with donor blood transfusion sequentially allows for larger changes in the ratio of HbS to HbA when compared to simple transfusion. Automated RBC exchange by apheresis is useful in situations where a rapid and drastic HbS reduction is indicated. Vascular access is an important consideration for transfusion. Although peripheral access may be sufficient, central venous catheters and implantable venous access devices may be necessary for adequate access over time. Blood bank considerations include adequate RBC antigen matching to mitigate the risk of RBC alloimmunization, of which patients with SCD are at risk of developing. Transfusion may be utilized in efforts to intervene in the evolution of potentially life-threatening complications of SCD such as acute stroke, severe acute anemia and acute chest syndrome. Transfusion is also useful in several non-acute settings, such as stroke prevention, pregnancy, pre-surgery, and transfusion support for curative therapies. Individualized treatment plans are an essential component of patient care. Continuous evaluation of clinical indications and evolution of guidelines will continue to optimize care for patients with SCD.     

Prolonged circulation of large polymeric nanoparticles by non-covalent adsorption on erythrocytes.

Polymeric nanoparticles have been extensively studied for use as intravascular drug delivery vehicles; however, their applications are limited by rapid clearance from circulation by the reticuloendothelial system (RES). Previous attempts to improve vascular circulation have focused on surface modification using polymers such as poloxamines, poloxamers, and polyethylene glycol, to prevent opsononization. We report on a novel method of prolonging intravascular particle circulation by anchoring the nanoparticles to the surface of red blood cells (RBCs). We hypothesize that particles adhered to RBCs can escape RES clearance due to the ability of RBCs to do so. This method is motivated by the strategy adopted by certain bacteria, for example, hemobartonella, that adhere to RBCs and remain in circulation for several weeks. Prolonged circulation of nanoparticles as large as 450 nm was observed after adsorption on RBCs. Although particles were eventually eliminated from circulation, RBCs were not cleared. RBC-anchored nanoparticles offer a novel approach for intravascular drug delivery and blood pool imaging.     

GPCR homomers and heteromers: A better choice as targets for drug development than GPCR monomers?

G protein-coupled receptors (GPCR) are targeted by many therapeutic drugs marketed to fight against a variety of diseases. Selection of novel lead compounds are based on pharmacological parameters obtained assuming that GPCR are monomers. However, many GPCR are expressed as dimers/oligomers. Therefore, drug development may consider GPCR as homo- and hetero-oligomers. A two-state dimer receptor model is now available to understand GPCR operation and to interpret data obtained from drugs interacting with dimers, and even from mixtures of monomers and dimers. Heteromers are distinct entities and therefore a given drug is expected to have different affinities and different efficacies depending on the heteromer. All these concepts would lead to broaden the therapeutic potential of drugs targeting GPCRs, including receptor heteromer-selective drugs with a lower incidence of side effects, or to identify novel pharmacological profiles using cell models expressing receptor heteromers.