Evaluation of hypotonic preswelling method for encapsulation of enalaprilat in intact human erythrocytes

Red blood cells based nanotheranostics: A smart biomimetic approach for fighting against cancer

The technique of engineering drug delivery vehicles continues to develop, which bring enhancements in working more efficiently and minimizing side effects to make it more effective and safer. The intense capability of therapeutic agents to remain undamaged in a harsh extracellular environment is helpful to the success of drug development efforts. With this in mind, alterations of biopharmaceuticals with enhanced stability and decreased immunogenicity have been an increasingly active focus of such efforts. Red blood cells (RBCs), also known as erythrocytes have undergone extensive scrutiny as potential vehicles for drug delivery due to their remarkable attributes over the years of research. These include intrinsic biocompatibility, minimal immunogenicity, flexibility, and prolonged systemic circulation. Throughout the course of investigation, a diverse array of drug delivery platforms based on RBCs has emerged. These encompass genetically engineered RBCs, non-genetically modified RBCs, and RBC membrane-coated nanoparticles, each devised to cater to a range of biomedical objectives. Given their prevalence in the circulatory system, RBCs have gained significant attention for their potential to serve as biomimetic coatings for artificial nanocarriers. By virtue of their surface emulation capabilities and customizable core materials, nanocarriers mimicking these RBCs, hold considerable promise across a spectrum of applications, spanning drug delivery, imaging, phototherapy, immunomodulation, sensing, and detection. These multifaceted functionalities underscore the considerable therapeutic and diagnostic potential across various diseases. Our proposed review provides the synthesis of recent strides in the theranostic utilization of erythrocytes in the context of cancer. It also delves into the principal challenges and prospects intrinsic to this realm of research. The focal point of this review pertains to accentuating the significance of erythrocyte-based theranostic systems in combating cancer. Furthermore, it precisely records the latest and the most specific methodologies for tailoring the attributes of these biomimetic nanoscale formulations, attenuating various discoveries for the treatment and management of cancer.

Erythrocytes Nanoparticle Delivery: A Boon for Targeting Tumor

Although nanoparticles (NPs) have many advantages as drug delivery systems, their poor stability in circulation, premature drug release, and nonspecific uptake in non-target organs have prompted biomimetic approaches to camouflage nano vehicles using natural cell membranes. Among them, which are extensively studied in erythrocytes, are the most abundant circulating blood cells. They are specially used for biomimetic coating on artificial NPs due to their excellent properties of good biocompatibility, biodegradability, non-immunogenicity, and long-term blood circulation. Erythrocyte-mimicking nanoparticles (EM-NPs) are prepared by combining nanoparticle cores with naturally derived erythrocyte (red blood cell or RBC) membranes. Compared with conventional nanosystems, EM-NPs hold the preferable characteristics of prolonged blood circulation time and immune evasion. In this review, the biomimetic platform of erythrocyte membrane-coated NPs is described in various aspects, with particular focus placed on the coating mechanism, preparation methods, characterization method, and recent advances in the biomedical applications of EM-NPs concerning cancer and targeted delivery.

Drug-loaded erythrocytes: Modern approaches for advanced drug delivery for clinical use

Scientific organizations worldwide are striving to create drug delivery systems that provide a high local concentration of a drug in pathological tissue without side effects on healthy organs in the body. Important physiological properties of red blood cells (RBCs), such as frequent renewal ability, good oxygen carrying ability, unique shape and membrane flexibility, allow them to be used as natural carriers of drugs in the body. Erythrocyte carriers derived from autologous blood are even more promising drug delivery systems due to their immunogenic compatibility, safety, natural uniqueness, simple preparation, biodegradability and convenience of use in clinical practice. This review is focused on the achievements in the clinical application of targeted drug delivery systems based on osmotic methods of loading RBCs, with an emphasis on advancements in their industrial production. This article describes the basic methods used for encapsulating drugs into erythrocytes, key strategic approaches to the clinical use of drug-loaded erythrocytes obtained by hypotonic hemolysis. Moreover, clinical trials of erythrocyte carriers for the targeted delivery are discussed. This article explores the recent advancements and engineering approaches employed in the encapsulation of erythrocytes through hypotonic hemolysis methods, as well as the most promising inventions in this field. There is currently a shortage of reviews focused on the automation of drug loading into RBCs; therefore, our work fills this gap. Finally, further prospects for the development of engineering and technological solutions for the automatic production of drug-loaded RBCs were studied. Automated devices have the potential to provide the widespread production of RBC-encapsulated therapeutic drugs and optimize the process of targeted drug delivery in the body. Furthermore, they can expedite the widespread introduction of this innovative treatment method into clinical practice, thereby significantly expanding the effectiveness of treatment in both surgery and all areas of medicine.

Exploring the Microfluidic Production of Biomimetic Hybrid Nanoparticles and Their Pharmaceutical Applications

Nanomedicines have made remarkable advances in recent years, addressing the limitations of traditional therapy and treatment methods. Due to their improved drug solubility, stability, precise delivery, and ability to target specific sites, nanoparticle-based drug delivery systems have emerged as highly promising solutions. The successful interaction of nanoparticles with biological systems, on the other hand, is dependent on their intentional surface engineering. As a result, biomimetic nanoparticles have been developed as novel drug carriers. In-depth knowledge of various biomimetic nanoparticles, their applications, and the methods used for their formulation, with emphasis on the microfluidic production technique, is provided in this review. Microfluidics has emerged as one of the most promising approaches for precise control, high reproducibility, scalability, waste reduction, and faster production times in the preparation of biomimetic nanoparticles. Significant advancements in personalized medicine can be achieved by harnessing the benefits of biomimetic nanoparticles and leveraging microfluidic technology, offering enhanced functionality and biocompatibility.

Red blood cell membrane nanoparticles for tumor phototherapy

Non-invasive phototherapy includes photodynamic therapy (PDT) and photothermal therapy (PTT), and has garnered special interest in anti-tumor therapy. However, traditional photosensitizers or photothermal agents are faced with major challenges, including easy recognition by immune system, rapid clearance from blood circulation, and low accumulation in target sites. Combining the characteristics of natural cell membrane with the characteristics of photosensitizer or photothermal agent is an important technology to achieve the ideal therapeutic effect of cancer. Red cell membrane (RBMs) coated can disguise phototherapy agents as endogenous substances, thus constructing a new nano bionic therapeutic platform, resisting blood clearance and prolonging circulation time. At present, a variety of phototherapy agents based on Nano-RBMs have been isolated or designed. In this review, firstly, the basic principles of Nano-RBMs and phototherapy are expounded respectively. Then, the latest progress of Nano-RBMs for PDT, PTT and PDT/PTT applications in recent five years has been introduced respectively. Finally, the problems and challenges of Nano-RBMs in the field of phototherapy are put forward.

Nucleic Acid Delivery with Red-Blood-Cell-Based Carriers

Gene therapy has the potential to become a staple of 21st-century medicine. However, to overcome the limitations of existing gene-delivery therapies, that is, poor stability and inefficient and delivery and accumulation of nucleic acids (NAs), safe drug-delivery systems (DDSs) allowing the prolonged circulation and expression of the administered genes in vivo are needed. In this review article, the development of DDSs over the past 70 years is briefly described. Since synthetic DDSs can be recognized and eliminated as foreign substances by the immune system, new approaches must be found. Using the body's own cells as DDSs is a unique and exciting strategy and can be used in a completely new way to overcome the critical limitations of existing drug-delivery approaches. Among the different circulatory cells, red blood cells (RBCs) are the most abundant and thus can be isolated in sufficiently large quantities to decrease the complexity and cost of the treatment compared to other cell-based carriers. Therefore, in the second part, this article describes 70 years of research on the development of RBCs as DDSs, covering the most important RBC properties and loading methods. In the third part, it focuses on RBCs as the NA delivery system with advantages and drawbacks discussed to decide whether they are suitable for NA delivery in vivo.

Extracellular Vesicles from Red Blood Cells and Their Evolving Roles in Health, Coagulopathy and Therapy

Red blood cells (RBCs) release extracellular vesicles (EVs) including both endosome-derived exosomes and plasma-membrane-derived microvesicles (MVs). RBC-derived EVs (RBCEVs) are secreted during erythropoiesis, physiological cellular aging, disease conditions, and in response to environmental stressors. RBCEVs are enriched in various bioactive molecules that facilitate cell to cell communication and can act as markers of disease. RBCEVs contribute towards physiological adaptive responses to hypoxia as well as pathophysiological progression of diabetes and genetic non-malignant hematologic disease. Moreover, a considerable number of studies focus on the role of EVs from stored RBCs and have evaluated post transfusion consequences associated with their exposure. Interestingly, RBCEVs are important contributors toward coagulopathy in hematological disorders, thus representing a unique evolving area of study that can provide insights into molecular mechanisms that contribute toward dysregulated hemostasis associated with several disease conditions. Relevant work to this point provides a foundation on which to build further studies focused on unraveling the potential roles of RBCEVs in health and disease. In this review, we provide an analysis and summary of RBCEVs biogenesis, composition, and their biological function with a special emphasis on RBCEV pathophysiological contribution to coagulopathy. Further, we consider potential therapeutic applications of RBCEVs.

Autologous erythrocytes delivery of berberine hydrochloride with long-acting effect for hypolipidemia treatment

Discovery of novel pharmacological effects of berberine hydrochloride (BH) has made its clinical application valuable. However, further development and applications of BH are hampered by its short half-life and the side effects associated with its intravenous (iv) injection. To improve the hypolipidemia efficacy and reduce side effects, we encapsulated BH into biocompatible red blood cells (RBCs) to explore its sustained-release effect by hypotonic pre-swelling method. From in vitro evaluation, BH loaded RBCs (BH-RBCs) presented similar morphology and osmotic fragility to native RBCs (NRBCs). After the loading process, the BH-RBCs maintained around 69% of Na⁺/K⁺-ATPase activity of NRBCs and phosphatidylserine externalization value of BH-RBCs was about 26.1 ± 2.9%. The survival test showed that the loaded cells could circulate in plasma for over 9 d. For in vivo evaluation, a series of tests including pharmacokinetics study and hypolipidemic effect were carried out to examine the long-acting effect of BH-RBCs. The results showed that the release of BH in the loaded cells could last for about 5 d and the hypolipidemic effect can still be observed on 5 d after injection. BH-loaded autologous erythrocytes seem to be a promising sustained releasing delivery system with long hypolipidemic effect.

In vivo nano-biosensing element of red blood cell-mediated delivery

Biosensors based on nanotechnology are developing rapidly and are widely applied in many fields including biomedicine, environmental monitoring, national defense and analytical chemistry, and have achieved vital positions in these fields. Novel nano-materials are intensively developed and manufactured for potential biosensing and theranostic applications while lacking comprehensive assessment of their potential health risks. The integration of diagnostic in vivo biosensors and the DDSs for delivery of therapeutic drugs holds an enormous potential in next-generation theranostic platforms. Controllable, precise, and safe delivery of diagnostic biosensing devices and therapeutic agents to the target tissues, organs, or cells is an important determinant in developing advanced nanobiosensor-based theranostic platforms. Particularly, inspired by the comprehensive biological investigations on the red blood cells (RBCs), advanced strategies of RBC-mediated in vivo delivery have been developed rapidly and are currently in different stages of transforming from research and design to pre-clinical and clinical investigations. In this review, the RBC-mediated delivery of in vivo nanobiosensors for applications of bio-imaging at the single-cell level, advanced medical diagnostics, and analytical detection of biomolecules and cellular activities are presented. A comprehensive perspective of the technical framework of the state-of-the-art RBC-mediated delivery systems is explained in detail to inspire the design and implementation of advanced nanobiosensor-based theranostic platforms taking advantage of RBC-delivery modalities.

Novel Fast and Reliable Method for Nano-Erythrosome Production Using Shear Force

Purpose

The production of nano-erythrosomes (NEs) by extrusion, which is considered the “gold standard”, has several disadvantages such as difficult equipment assembly, long procedure time, variable pressure, and problems with sterility. An alternative approach, using ultrasound probe, has been shown to overheat the sample and have suboptimal results compared to the extrusion method. In our study, we propose, develop, and test a new method for the fabrication of NEs based on shear force and then compare it to the “gold standard” extrusion approach.

Methods

The new method consists of mechanical shear force disruption of the hemoglobin-depleted erythrocyte ghost membranes, with the aid of a rotor stator based tissue homogenizer. Using the same batches of erythrocyte ghost membranes, we compared NEs produced by shear force to NEs produced by the well-established extrusion approach. NEs were characterized for yield, size, encapsulation efficiency, morphology, and stability by flow cytometry (FC), transmission electron microscopy (TEM), and zeta potential analysis.

Results

The shear force based process was easier to set up, significantly faster, had better sterility control, and decreased variability between batches. The shear force method generated NEs with the desired size distribution (particles diameter ~125 nm), which were morphologically and functionally equivalent to the NEs produced by extrusion. NEs produced by shear force were stable in terms of counts, size, and fluorescence intensity for 3 weeks at +4°C. Moreover, they showed colloidal stability and minimal influence to centrifugal stress, turbulence shock, and hemolytic potential.

Conclusion

The newly proposed shear force method allows faster, easier, and highly reproducible NEs production when compared to the conventional extrusion approach. The new setup allows simultaneous production of sterile batches of NEs, which have homogenous size distribution, good stability, and improved shelf life storage. The ability of the shear force method to process also high concentration samples indicates a future potential development of large-scale NEs production and industrial application, which has been a challenge for the extrusion method.

Erythrocytes as Carriers: From Drug Delivery to Biosensors

Drug delivery using natural biological carriers, especially erythrocytes, is a rapidly developing field. Such erythrocytes can act as carriers that prolong the drug's action due to its gradual release from the carrier; as bioreactors with encapsulated enzymes performing the necessary reactions, while remaining inaccessible to the immune system and plasma proteases; or as a tool for targeted drug delivery to target organs, primarily to cells of the reticuloendothelial system, liver and spleen. To date, erythrocytes have been studied as carriers for a wide range of drugs, such as enzymes, antibiotics, anti-inflammatory, antiviral drugs, etc., and for diagnostic purposes (e.g. magnetic resonance imaging). The review focuses only on drugs loaded inside erythrocytes, defines the main lines of research for erythrocytes with bioactive substances, as well as the advantages and limitations of their application. Particular attention is paid to in vivo studies, opening-up the potential for the clinical use of drugs encapsulated into erythrocytes.

Design and evaluation of anti-fibrosis drug engineered resealed erythrocytes for targeted delivery

Resealed erythrocytes (RSE) are potential, site-specific carrier system for drug delivery with prolonged drug release activity. In this study, erythrocytes obtained from Wistar albino rats were loaded with ambroxol hydrochloride (AH) with the focus to convenience the lung targeting possibility of the carrier erythrocytes. AH loading in erythrocytes using preswell dilution technique with glutaraldehyde (GA) as a cross-linking agent was evaluated and validated. Drug-loaded erythrocyte was characterized in terms of in vitro drug release followed by osmotic fragility study which showed amplified drug entrapment efficiency (DEE) and hemoglobin content values as well. In vivo lung fibrosis study, rats were sensitized to egg albumin by intraperitoneal (i.p.) injection and then inhalation in a whole body inhalation chamber. A sign of inflammation, airway sub-mucosal fibrosis, hypertrophy, and hyperplasia was observed. A series of in vivo studies were carried out to describe the effect of AH-loaded RSE including measurement of cytokines in Bronchoalveolar Lavage (BAL) fluid and histopathology study. AH showed a stepwise reduced level of cytokines in BAL at a different time interval after being injected of AH-loaded RSE. Furthermore, in vivo lung distribution experiments were performed for optimized formulation, and degree of distribution of the drugs inside the targeted organ was found to be satisfactory.

Red blood cell membrane-camouflaged nanoparticles: a novel drug delivery system for antitumor application

Erythrocytes (red blood cells, RBCs) are the most abundant circulating cells in the blood and have been widely used in drug delivery systems (DDS) because of their features of biocompatibility, biodegradability, and long circulating half-life. Accordingly, a "camouflage" comprised of erythrocyte membranes renders nanoparticles as a platform that combines the advantages of native erythrocyte membranes with those of nanomaterials. Following injection into the blood of animal models, the coated nanoparticles imitate RBCs and interact with the surroundings to achieve long-term circulation. In this review, the biomimetic platform of erythrocyte membrane-coated nano-cores is described with regard to various aspects, with particular focus placed on the coating mechanism, preparation methods, verification methods, and the latest anti-tumor applications. Finally, further functional modifications of the erythrocyte membranes and attempts to fuse the surface properties of multiple cell membranes are discussed, providing a foundation to stimulate extensive research into multifunctional nano-biomimetic systems.

Recent advancements in erythrocytes, platelets, and albumin as delivery systems

In the past few years, nanomaterial-based drug delivery systems have been applied to enhance the efficacy of therapeutics and to alleviate negative effects through the controlled delivery of targeting and releasing agents. However, few drug carriers can achieve high targeting efficacy, even when targeting modalities and surface markers are introduced. Immunological problems have also limited their wide applications. Biological drug delivery systems, such as erythrocytes, platelets, and albumin, have been extensively investigated because of their unique properties. In this review, erythrocytes, platelets, and albumin are described as efficient drug delivery systems. Their properties, applications, advantages, and limitations in disease treatment are explained. This review confirms that these systems can be used to facilitate a specific, biocompatible, and smart drug delivery.

Red blood cell ghosts as promising drug carriers to target wound infections

Autologous red blood cell ghosts (RBC ghosts) can carry cytokines to the sites of inflammation. The targeting moiety of the RBC ghosts is associated with the nature of purulent inflammation, where the erythrocytes are phagocyted and encapsulated drugs are released. In the present study we have investigated the healing potential of RBC ghosts loaded with cytokine IL-1β and antibiotic. Additionally, the pharmacokinetic properties of RBC ghosts loaded with IL-1β were studied. 35 Male Wistar rats (250-300g) were used in the pharmacokinetic study and in a wound infection model where a suspension of Staphylococcus aureus was placed into a surgical cut of the skin and subcutaneous tissue in the femoral region. In order to monitor progression of the wound repair processes, wound swabs or aspiration biopsies were taken for analyses on the 1st-6th days. Wound repair dynamics assessment was based on suppression of S. aureus growth, signs of pain, time of disappearance of pus and infiltration around the wound. Visual observations, as well as microbiological and cytological analysis of wound exudates demonstrated a significant acceleration of healing processes in a group of animals treated with a local injection of IL-1β and ceftriaxone encapsulated into RBC ghosts when compared to the animals treated either with a local or IM injection of free drugs. For the pharmacokinetic study, single IV injections of either free or encapsulated IL-1β were made and the concentration of IL-1β in serum samples and tissue homogenates were determined. Encapsulation in RBC ghosts improved pharmacokinetic profiles of IL-1β by increasing the half-life, reducing its clearance, and increasing the deposition of the drug in the liver, spleen and lungs. These data suggest that RBC ghosts are effective drug carriers for targeted delivery of cytokines to the sites of inflammation, and have a potential for improving the treatment outcomes of purulent diseases.

Influence of the glycocalyx and plasma membrane composition on amphiphilic gold nanoparticle association with erythrocytes

Erythrocytes are attractive as potential cell-based drug carriers because of their abundance and long lifespan in vivo. Existing methods for loading drug cargos into erythrocytes include hypotonic treatments, electroporation, and covalent attachment onto the membrane, all of which require ex vivo manipulation. Here, we characterized the properties of amphiphilic gold nanoparticles (amph-AuNPs), comprised of a ∼2.3 nm gold core and an amphiphilic ligand shell, which are able to embed spontaneously within erythrocyte membranes and might provide a means to load drugs into red blood cells (RBCs) directly in vivo. Particle interaction with RBC membranes occurred rapidly at physiological temperature. We further show that amph-AuNP uptake by RBCs was limited by the glycocalyx and was particularly influenced by sialic acids on cell surface proteoglycans. Using a reductionist model membrane system with synthetic lipid vesicles, we confirmed the importance of membrane fluidity and the glycocalyx in regulating amph-AuNP/membrane interactions. These results thus provide evidence for the interaction of amph-AuNPs with erythrocyte membranes and identify key membrane components that govern this interaction, providing a framework for the development of amph-AuNP-carrying erythrocyte 'pharmacytes' in vivo.

Drug delivery and innovative pharmaceutical development in mimicking the red blood cell membrane

Circulation half-life has become one of the major design considerations in nanoparticle drug delivery systems. By taking cues for designing long circulating carriers from natural entities such as red blood cells (RBCs) has been explored for many years. Among all the cellular carriers including leukocytes, fibroblasts, islets, and hepatocytes, RBCs offer several distinctive features. The present review underlines a discussion on the applications of different RBC carriers (RBC mimics) which can evade the body’s reticuloendothelial system overcoming many barriers such as size, shape, accelerated blood clearance, mechanical properties, control over particle characteristics, and surface chemistry. Bilayer membrane liposomes infusing phospholipids have long been synthesized to mimic bioconcave RBC carriers using the notion of stealth liposomes. This is not a comprehensive review; some illustrative examples are given on how they are currently obtained. A special attention is devoted to the RBC mimics from polymers, red cell membrane ghosts, and the red cell membrane enclosing polymeric cores as potential drug carriers. The present research reveals the achievement of RBC surface charge to accord with the immune system as a game of hide and seek in a much promising way in the light of its pharmaceutical applications.

Erythrocytes-based synthetic delivery systems: transition from conventional to novel engineering strategies

INTRODUCTION

Erythrocytes (red blood cells [RBCs]) and artificial or synthetic delivery systems such as liposomes, nanoparticles (NPs) are the most investigated carrier systems. Herein, progress made from conventional approach of using RBC as delivery systems to novel approach of using synthetic delivery systems based on RBC properties will be reviewed.

AREAS COVERED

We aim to highlight both conventional and novel approaches of using RBCs as potential carrier system. Conventional approaches which include two main strategies are: i) directly loading therapeutic moieties in RBCs; and ii) coupling them with RBCs whereas novel approaches exploit structural, mechanical and biological properties of RBCs to design synthetic delivery systems through various engineering strategies. Initial attempts included coupling of antibodies to liposomes to specifically target RBCs. Knowledge obtained from several studies led to the development of RBC membrane derived liposomes (nanoerythrosomes), inspiring future application of RBC or its structural features in other attractive delivery systems (hydrogels, filomicelles, microcapsules, micro- and NPs) for even greater potential.

EXPERT OPINION

In conclusion, this review dwells upon comparative analysis of various conventional and novel engineering strategies in developing RBC based drug delivery systems, diversifying their applications in arena of drug delivery. Regardless of the challenges in front of us, RBC based delivery systems offer an exciting approach of exploiting biological entities in a multitude of medical applications.

Erythrocyte-inspired delivery systems

Herein recent progress in developing red blood cell (RBC)-inspired delivery systems is reviewed, with an emphasis on how our growing understanding of fundamental biological properties of natural RBCs has been applied in the design and engineering of these delivery systems. Specifically, progress achieved in developing carrier RBCs, a class of delivery vehicles engineered by directly loading natural RBCs with therapeutic agents, will be reviewed. Then alternative approaches to engineering synthetic vehicles through mimicking the mechanobiological and chemico-biological properties of natural RBCs will be considered. The synthesis and application of RBC membrane-derived vesicles, of which the natural RBC membranes are collected and directly utilized to prepare drug carriers, will then be discussed. Finally, a recent approach in engineering RBC membrane-camouflaged nanoparticle systems that combine advantages of natural RBCs and synthetic biomaterials will be highlighted. These developments indicate that RBC-inspired delivery systems will result in next-generation nanomedicine with extensive medical applications.

Preparation and in-vitro characterization of tramadol-loaded carrier erythrocytes for long-term intravenous delivery

Objectives

The hypo-osmotic dialysis method was used for preparation of tramadol-loaded human intact erythrocytes. In response to rapid drug escape from the erythrocytes, a membrane cross-linker, glutaraldehyde, was used successfully.

Methods

The resulting carrier cells were validated in terms of the accuracy and precision of the whole drug loading procedure.

Key findings

The average loaded amount, entrapment efficiency and cell recovery were 1.9041 mg, 95.98% and 85.13%, respectively. The effects of different drug concentrations on loading parameters were studied with the concentration of 10 mg/ml selected as optimal. A series of in-vitro characteristics of carrier erythrocytes, including tramadol release behaviour, haematological indices, particle size distribution, scanning electron microscopy, and osmotic/turbulence fragilities were determined compared with the sham-entrapped and unloaded cells. The results of these in-vitro tests indicated that the erythrocytes did not undergo remarkable irreversible size and shape/topology changes, but the fragility of the membranes of the processed cells were increased.

Conclusions

The collective results of this study showed that the optimized method of entrapment was suitable for the encapsulation of tramadol in erythrocytes with the final carrier cells ready to enter the in-vivo animal studies as a promising long-circulating carrier for tramadol.

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

IMPORTANCE OF THE FIELD

Vascular delivery of several classes of therapeutic agents may benefit from carriage by red blood cells (RBC), for example, drugs that require delivery into phagocytic cells and those that must act within the vascular lumen. The fact that several protocols of infusion of RBC-encapsulated drugs are now being explored in patients illustrates a high biomedical importance for the field. AREAS COVERED BY THIS REVIEW: Two strategies for RBC drug delivery are discussed: encapsulation into isolated RBC ex vivo followed by infusion in compatible recipients and coupling therapeutics to the surface of RBC. Studies of pharmacokinetics and effects in animal models and in human studies of diverse therapeutic enzymes, antibiotics and other drugs encapsulated in RBC are described and critically analyzed. Coupling to RBC surface of compounds regulating immune response and complement, affinity ligands, polyethylene glycol alleviating immune response to donor RBC and fibrinolytic plasminogen activators are described. Also described is a new, translation-prone approach for RBC drug delivery by injection of therapeutics conjugated with fragments of antibodies providing safe anchoring of cargoes to circulating RBC, without need for ex vivo modification and infusion of RBC.

WHAT THE READER WILL GAIN

Readers will gain historical perspective, current status, challenges and perspectives of medical applications of RBC for drug delivery.

TAKE HOME MESSAGE

RBC represent naturally designed carriers for intravascular drug delivery, characterized by unique longevity in the bloodstream, biocompatibility and safe physiological mechanisms for metabolism. New approaches for encapsulating drugs into RBC and coupling to RBC surface provide promising avenues for safe and widely useful improvement of drug delivery in the vascular system.

Preparation and Validation of Carrier Human Erythrocytes Loaded by Bovine Serum Albumin as a Model Antigen/Protein

Erythrocytes as the most readily available and abundant cells within the body have been studied extensively for their potential application as drug delivery carries. In this study, human erythrocytes were loaded by bovine serum albumin (BSA) as a model antigen/protein using hypotonic preswelling method for targeted delivery of this antigen-to antigen-presenting cells. The average loaded amount, efficiency of entrapment, and cell recovery upon loading procedure were 1979.25 +/- 9.4 microg, 30.06 +/- 0.20%, and 87.53 +/- 0.66%, respectively. The total BSA recovery upon loading procedure was 97.20 +/- 4.90%. The apparent mechanism of entrapment was simple concentration-based gradient in/out the cells with some minor limiting factors against protein entry into the cells. We have shown that the intra- and intersubject variations of the method were interestingly low (i.e., less than 5% in all cases).

Preparation and in vitro evaluation of carrier erythrocytes for RES-targeted delivery of interferon-alpha 2b

Carrier erythrocytes is one of the most promising systemic drug delivery systems investigated in recent decades. In this study, human erythrocytes have been loaded with interferon-alpha 2b (IFN) with the aim to benefit the reticuloendothelial system (RES) targeting potential of the carrier cells. Hypotonic preswelling method was used for drug loading in erythrocytes and the entire loading procedure was evaluated and validated. The loaded amount, entrapment efficiency and cell recovery of the loading procedure were 2906.33+/-588.35IU/0.1ml, 14.53+/-2.94%, and 83.61+/-0.49%, respectively, all being practically feasible. The carrier erythrocytes were characterized in vitro in terms of their drug release kinetics, hematological indices, particle size distribution, SEM analysis, and osmotic and turbulence fragility. IFN release from carrier cells was a relatively rapid process in comparison to the cell lysis kinetics, which is unusual considering the whole body of data published on this delivery system and other protein drugs, so far. All the tested in vitro characteristics showed significant, sometimes notable changes upon drug loading procedure, both with and without the drug.

Preparation and in vitro characterization of carrier erythrocytes for vaccine delivery

Erythrocytes as the most readily available and abundant cells within the body, have been studied extensively for their potential application as drug delivery carriers. In this study, human erythrocytes have been loaded by bovine serum albumin (BSA) as a model antigen/protein using hypotonic preswelling method for targeted delivery of this antigen to antigen-presenting cells (APCs). A series of in vitro tests have been carried out to characterize the carrier cells in vitro, including loading parameters, BSA and hemoglobin release kinetics, hematological indices, particle size distribution, SEM analysis, osmotic and turbulence fragility, and osmotic competency. BSA was loaded in erythrocytes with a loaded amount of 1.98+/-0.009mg with antigen release from carrier cells showing a zero-order kinetic consistent to that of the cell lysis. The apparent cell sizes, measured using laser scattering, were not significantly different from normal erythrocytes, but the real sizes, measured using SEM, and surface topologies were quite different between loaded and unloaded cells. The BSA-loaded cells were remarkably more fragile and less deformable compared to the normal cells. Totally, BSA-loaded erythrocytes seem to be a promising delivery system for reticuloendothelial system (RES) targeting of the antigens.

Applications of carrier erythrocytes in delivery of biopharmaceuticals

Carrier erythrocytes, resealed erythrocytes loaded by a drug or other therapeutic agents, have been exploited extensively in recent years for both temporally and spatially controlled delivery of a wide variety of drugs and other bioactive agents owing to their remarkable degree of biocompatibility, biodegradability and a series of other potential advantages. Biopharmaceuticals, therapeutically significant peptides and proteins, nucleic acid-based biologicals, antigens and vaccines, are among the recently focused pharmaceuticals for being delivered using carrier erythrocytes. In this article, the potential applications of erythrocytes in drug delivery have been reviewed with a particular stress on the studies and laboratory experiences on successful erythrocyte loading and characterization of the different classes of biopharmaceuticals.

Encapsulation and in vitro evaluation of amikacin-loaded erythrocytes

The aim of our present work was to establish the effect of the osmolality of the hypotonic buffer on the encapsulated amount and the in vitro properties of Amikacin-loaded erythrocytes. Amikacin was encapsulated in rat erythrocytes using a hypotonic dialysis method with hypotonic buffers of different osmolalities with mean values around 90 and 150 mOsm/kg. Morphological examination of the ghost erythrocytes was accomplished using scanning electron microscopy (SEM). The osmotic fragility of normal and loaded erythrocytes was tested using hypotonic solutions. Evaluation of the hematological parameters of the control and loaded erythrocytes was carried out using a hematology system analyzer. Amikacin release from loaded erythrocytes was tested in autologous plasma at 37 degrees C over a 24-h period. The quantification of Amikacin in loaded erythrocytes and in autologous plasma was performed using an HPLC technique. A higher osmotic fragility of loaded erythrocytes was observed using a low osmolality buffer. Some hematological parameters showed statistically significant differences between the loaded erythrocytes obtained using two buffers of different osmolalities with respect to untreated erythrocytes. According to our results, Amikacin carrier erythrocytes obtained by hypotonic dialysis using a low osmolality buffer (90 mOsm/kg) should afford a good encapsulation yield, appropriate morphological properties, and sustained release in vitro.

Drug, enzyme and peptide delivery using erythrocytes as carriers

Erythrocytes are potential biocompatible vectors for different bioactive substances, including drugs. These can be used successfully as biological carriers of drugs, enzymes and peptides. There are currently diverse methods that permit drug encapsulation in erythrocytes with an appropriate yield. The methods most commonly employed are based on a high-haematocrit dialysis procedure, mainly hypo-osmotic dialysis. Erythrocytes loaded with drugs and other substances allow for different release rates to be obtained. Encapsulation in erythrocytes significantly changes the pharmacokinetic properties of drugs in both animals and humans, enhancing liver and spleen uptake and targeting the reticulo-endothelial system (RES). Amongst other applications, erythrocytes have been used for drug-targeting the RES with aminoglycoside antibiotics; the selective transport to certain organs and tissues of certain antineoplastic drugs, such as methotrexate, doxorubicine, etoposide, carboplatin, etc.; the encapsulation of angiotensin-converting enzyme (ACE) inhibitors, systemic corticosteroids, the encapsulation of new prodrugs with increased duration of action, etc. Erythrocytes are also attractive systems in the sense of their potential ability to deliver proteins and therapeutic peptides. Thus, erythrocytes have been used for the transport of enzymes destined for the correction of metabolic alterations as l-asparaginase, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (AlDH) among others. Erythrocytes have been used successfully as carriers of anti-HIV peptides, such as AZT, nucleoside analogues, antisense oligonucleotides, antineoplastic peptides, erythropoietin, interleukin 3, etc. Amongst other applications, mention may be made of paramagnetic erythrocytes, encapsulation of MRI contrast agents or the study of the metabolism of the red cell. Although erythrocytes have been applied with different uses in human medicine, their deployment is still very limited due to difficulties involving storage, its exposure to contamination and the absence of a validated industrial procedure for its preparation.

Inhibition of serum angiotensin-converting enzyme in rabbits after intravenous administration of enalaprilat-loaded intact erythrocytes

Encapsulation of drugs in intact erythrocytes, because of the profound characteristics of these natural microspheres, has gained considerable attention in recent years. In this study, the inhibition time courses of serum angiotensin-converting enzyme (ACE) activity after intravenous administration of enalaprilat encapsulated in intact erythrocytes was evaluated and compared with free drug, in a rabbit model. Three groups of animals each received free drug, drug-loaded erythrocytes or sham-encapsulated erythrocytes. Serum ACE activity was determined in each case using the synthetic substrate hippuryl-histidyl-leucine and quantitation of the hippuric acid released by a developed and validated HPLC method. The serum ACE inhibition profiles in the three groups showed that the encapsulated drug inhibited the serum ACE more slowly, more efficiently, over a considerably longer time and in a more reproducible manner, than the free drug or sham-encapsulated erythrocytes. We conclude that the erythrocytes can serve as efficacious slow-release drug carriers for enalaprilat in circulation.

A simple HPLC method for quantitation of enalaprilat

A reversed-phase high performance liquid chromatography (HPLC) method with UV-detection has been developed for the determination of enalaprilat. The method produced linear response over the wide concentration range of 1-200 microg/ml, with an average accuracy of 97.35 +/- 4.93%, as well as average intra- and iter-day variations of 3.72 and 5.18%, respectively. The limits of detection and quantitation of the method were 0.125 and 0.5 microg/ml, respectively. The method was selective with respect to resolution of the peaks of enalaprilat and enalapril maleate.