Heterodimer-loaded erythrocytes as bioreactors for slow delivery of the antiviral drug azidothymidine and the antimycobacterial drug ethambutol

Development of Cell-Derived Plasma Membrane Vesicles as a Nanoparticle Encapsulation and Delivery System

Background

Developing non-invasive delivery platforms with a high level of structural and/or functional similarity to biological membranes is highly desirable to reduce toxicity and improve targeting capacity of nanoparticles. Numerous studies have investigated the impacts of physicochemical properties of engineered biomimetic nanoparticles on their interaction with cells, yet technical difficulties have led to the search for better biomimetics, including vesicles isolated directly from live cells. Cell-derived giant plasma membrane vesicles (GPMVs), in particular, offer a close approximation of the intact cell plasma membrane by maintaining the latter's compositional complexity, protein positioning in a fluid-mosaic pattern, and physical and mechanical properties. Thus, to overcome technical barriers of prior nanoparticle delivery approaches, we aimed to develop a novel method using GPMVs to encapsulate a variety of engineered nanoparticles, then use these core-shell, nanoparticle-GPMV vesicle structures to deliver cargo to other cells.

Results

The GPMV system in this study was generated by chemically inducing vesiculation in A549 cells, a model human alveolar epithelial line. These cell-derived GPMVs retained encapsulated silica nanoparticles (50 nm diameter) for at least 48 hours at 37 °C. GPMVs showed nearly identical lipid and protein membrane profiles as the parental cell plasma membrane, with or without encapsulation of nanoparticles. Notably, GPMVs were readily endocytosed in the parental A549 cell line as well as the human monocytic THP-1 cell line. Higher cellular uptake levels were observed for GPMV-encapsulated nanoparticles compared to control groups, including free nanoparticles. Further, GPMVs delivered a variety of nanoparticles to parental cells with reduced cytotoxicity compared to free nanoparticles at concentrations that were otherwise significantly toxic.

Conclusions

We have introduced a novel technique to load nanoparticles within the cell plasma membrane during the GPMV vesiculation process. These GPMVs are capable of (a) encapsulating different types of nanoparticles (including larger and not highly-positively charged bodies that have been technically challenging cargoes) using a parental cell uptake technique, and (b) improving delivery of nanoparticles to cells without significant cytotoxicity. Ultimately, endogenous surface membrane proteins and lipids can optimize the physicochemical properties of cell membrane-derived vesicles, which could lead to highly effective cell membrane-based nanoparticle/drug delivery systems.

Blood cell-based drug delivery systems: a biomimetic platform for antibacterial therapy

With the rapid increase in multidrug-resistance against antibiotics, higher doses of antibiotics or more effective antibiotics are needed to treat diseases, which ultimately leads to a decrease in the body's immunity and seriously threatens human health worldwide. The efficiency of antibiotics has been a large challenge for years. To overcome this problem, many carriers are utilized for anti-bacteria, attempting to optimize the delivery of such drugs and transport them safely and directly to the site of disease. Blood cell-based drug delivery systems present several advantages as compared to polymeric delivery system. These blood cells including red blood cells (RBCs), leukocytes, platelets. The blood cells and their membranes can both be used as drug carriers to deliver antibacterial drugs. In addition, blood cells can overcome many physiological/pathological obstacles faced by nanoparticles in vivo and effectively deliver drugs to the site of the disease. In this paper, we review studies on blood cell-based delivery systems used in antibacterial therapy, and analyze different roles in antibacterial therapy, which provide basis for further study in this field.

Cell-based drug delivery systems and their in vivo fate

Cell-based drug delivery systems (DDSs) have received attention recently because of their unique biological properties and self-powered functions, such as excellent biocompatibility, low immunogenicity, long circulation time, tissue-homingcharacteristics, and ability to cross biological barriers. A variety of cells, including erythrocytes, stem cells, and lymphocytes, have been explored as functional vectors for the loading and delivery of various therapeutic payloads (e.g., small-molecule and nucleic acid drugs) for subsequent disease treatment. These cell-based DDSs have their own unique in vivo fates, which are attributed to various factors, including their biological properties and functions, the loaded drugs and loading process, physiological and pathological circumstances, and the body's response to these carrier cells, which result in differences in drug delivery efficiency and therapeutic effect. In this review, we summarize the main cell-based DDSs and their biological properties and functions, applications in drug delivery and disease treatment, and in vivo fate and influencing factors. We envision that the unique biological properties, combined with continuing research, will enable development of cell-based DDSs as friendly drug vectors for the safe, effective, and even personalized treatment of diseases.

Dual Affinity to RBCs and Target Cells (DART) Enhances Both Organ- and Cell Type-Targeting of Intravascular Nanocarriers

A long-standing goal of nanomedicine is to improve a drug's benefit by loading it into a nanocarrier that homes solely to a specific target cell and organ. Unfortunately, nanocarriers usually end up with only a small percentage of the injected dose (% ID) in the target organ, due largely to clearance by the liver and spleen. Further, cell-type-specific targeting is rarely achieved without reducing target organ accumulation. To solve these problems, we introduce DART (dual affinity to RBCs and target cells), in which nanocarriers are conjugated to two affinity ligands, one binding red blood cells and one binding a target cell (here, pulmonary endothelial cells). DART nanocarriers first bind red blood cells and then transfer to the target organ's endothelial cells as the bound red blood cells squeeze through capillaries. We show that within minutes after intravascular injection in mice nearly 70% ID of DART nanocarriers accumulate in the target organ (lungs), more than doubling the % ID ceiling achieved by a multitude of prior technologies, finally achieving a majority % ID in a target organ. Humanized DART nanocarriers in ex vivo perfused human lungs recapitulate this phenomenon. Furthermore, DART enhances the selectivity of delivery to target endothelial cells over local phagocytes within the target organ by 6-fold. DART's marked improvement in both organ- and cell-type targeting may thus be helpful in localizing drugs for a multitude of medical applications.

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.

Cellular Cyborgs: On the Precipice of a Drug Delivery Revolution

Cell-based drug delivery systems offer the prospect of biocompatibility, large-loading capacity, long in vivo lifespan, and active targeting of diseased sites. However, these opportunities are offset by an array of challenges, including safeguarding the integrity of the drug cargo and the cellular host, as well as ensuring that drug release occurs at the appropriate time and place. Emerging strategies that address these, and related, issues, are described herein.

Non-genetic engineering of cells for drug delivery and cell-based therapy

Cell-based therapy is a promising modality to address many unmet medical needs. In addition to genetic engineering, material-based, biochemical, and physical science-based approaches have emerged as novel approaches to modify cells. Non-genetic engineering of cells has been applied in delivering therapeutics to tissues, homing of cells to the bone marrow or inflammatory tissues, cancer imaging, immunotherapy, and remotely controlling cellular functions. This new strategy has unique advantages in disease therapy and is complementary to existing gene-based cell engineering approaches. A better understanding of cellular systems and different engineering methods will allow us to better exploit engineered cells in biomedicine. Here, we review non-genetic cell engineering techniques and applications of engineered cells, discuss the pros and cons of different methods, and provide our perspectives on future research directions.

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.

Delivery of drugs bound to erythrocytes: new avenues for an old intravascular carrier

For several decades, researchers have used erythrocytes for drug delivery of a wide variety of therapeutics in order to improve their pharmacokinetics, biodistribution, controlled release and pharmacodynamics. Approaches include encapsulation of drugs within erythrocytes, as well as coupling of drugs onto the red cell surface. This review focuses on the latter approach, and examines the delivery of red blood cell (RBC)-surface-bound anti-inflammatory, anti-thrombotic and anti-microbial agents, as well as RBC carriage of nanoparticles. Herein, we discuss the progress that has been made in surface loading approaches, and address in depth the issues relevant to surface loading of RBC, including intrinsic features of erythrocyte membranes, immune considerations, potential surface targets and techniques for the production of affinity ligands.

Carrier erythrocytes: recent advances, present status, current trends and future horizons

INTRODUCTION

Carrier erythrocytes, thanks to their main advantages, including biocompatibility, biodegradability, immunocompatibility, simple and well-known structure and physiology, availability for sampling and versatility in loading and use, have been studied as cellular carriers for delivery of drugs and other bioactive agents for more than three decades. Based on this body of knowledge and recent advances in this field, and with the help of novel multidisciplinary sciences and technologies, it seems that this field is becoming renowned and experiencing an outstanding turning point in its developmental history.

AREAS COVERED

In this trendy and timely review, following a short historical review of the story of erythrocytes from oxygen delivery to drug delivery and evaluation of the present status of these biocarriers, recent advances and current experimental, technological and clinical trends, as well as future horizons, and, in particular, translation-prone strategies, are going to be discussed in detail.

EXPERT OPINION

Despite the challenging developmental history of carrier erythrocytes, they now stand closer to clinical use and market entrance due to their unique advantages in drug delivery, proven by recently reported success stories in late-stage clinical trials and progresses made in biotechnology, nanotechnology and biomaterials fields. Translation-prone approaches, like in vivo loading of circulating erythrocytes or semiautomatic loading of erythrocytes, and more realistic study designs by focusing on clinical needs that have not been responded to or erythrocyte biology/fate-inspired study design are among the main trends being focused on by pioneer research groups active in this field of drug delivery.

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.

Selective killing of Mycobacterium avium-infected macrophages by inhibition of phosphorylated signal transducer and activator of transcription type 1

Mycobacterium avium infects mononuclear phagocytes, which thereby become reservoirs for this pathogen. Currently recommended therapy does not ensure the eradication of intracellular bacteria. Here, we report that M. avium infection in macrophages activates the signal transducer and activator of transcription type 1 (STAT-1) signaling pathway. Fludarabine, an antileukemic drug active against cells that express STAT-1, selectively kills M. avium-infected macrophages. These findings suggest that phosphorylated STAT-1 can enhance the survival of macrophages, promoting their role as persistent reservoirs of M. avium. This work invites research on new combination therapeutic approaches that consist of fludarabine, to kill the macrophage reservoir, and antibacterial agents, to eliminate mycobacteria released from the dead cells.

Prolonged islet allograft survival in diabetic mice upon macrophage depletion by clodronate-loaded erythrocytes

Early impairment of islet function and graft loss strongly limit the success of allogenic islet transplantation in insulin-dependent diabetes. Macrophages play a key role in this process thus the depletion of these cells may strongly affect islet survival. In this study, we have evaluated the effect of the depletion of macrophages in mouse allograft rejection using a new approach based on a single infusion of red blood cells loaded with the synthetic analogue of pyrophosphate clodronate. Graft survival was 19.4+/-0.89 and 20+/-2 days in the two control groups treated with physiological solution and unloaded erythrocytes, respectively; 25+/-1.9 days in the group treated with free-clodronate and 35+/-6 days in the erythrocytes-loaded group. Our results indicate clodronate selectively targeted to the macrophagic cells by a single administration of engineered erythrocytes can significantly prolong islet graft survival and open new therapeutic strategies in islet transplantation.

Cell-based drug delivery

Drug delivery has been greatly improved over the years by means of chemical and physical agents that increase bioavailability, improve pharmacokinetic and reduce toxicities. At the same time, cell based delivery systems have also been developed. These possesses a number of advantages including prolonged delivery times, targeting of drugs to specialized cell compartments and biocompatibility. Here we'll focus on erythrocyte-based drug delivery. These systems are especially efficient in releasing drugs in circulations for weeks, have a large capacity, can be easily processed and could accommodate traditional and biologic drugs. These carriers have also been used for delivering antigens and/or contrasting agents. Carrier erythrocytes have been evaluated in thousands of drug administration in humans proving safety and efficacy of the treatments. Erythrocyte-based delivery of new and conventional drugs is thus experiencing increasing interests in drug delivery and in managing complex pathologies especially when side effects could become serious issues.

High throughput HPLC-ESI-MS method for the quantitation of dexamethasone in blood plasma

Dexamethasone is a synthetic glucocorticoid with potent anti-inflammatory properties. However, its administration causes significant side effects, specially in long-term therapy. A new approach for limiting adverse effects consists in the slow and constant deliver of this drug, using dexamethasone-21-phosphate-loaded erythrocytes (RBC) as circulating bioreactors converting the non-diffusible dexamethasone-21-phosphate into the diffusible dexamethasone. In order to evaluate the real possibility to use this new method of administration, a simple, cheap and rapid assay was set to manage a large number of samples originating from clinical studies. Due to the sample complexity and analite polarity, electrospray mass spectrometry (MS) is the most powerful technique to achieve qualitative and quantitative data. In order to overcome the complex, time-consuming and expensive LC-MS/MS methods reported in the literature in the present work a standard fluxes HPLC-ESI-MS method was set up for quantitative evaluation of dexamethasone. Thanks to the extraction ion chromatogram (XIC) feature of the software, it was possible to obtain sharp profiles for dexamethasone (DXM) and for the employed internal standard (IS) flumethasone (FM), in spite of the extremely complicated chromatogram obtained after HPLC separation of acetonitrile extracted plasma sample, thus avoiding the use of the expensive deuterated internal standard. This enabled us to obtain a linear response curve, allowing the quantification of DXM from blood samples at the picomoles level.

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.

Erythrocyte-based drug delivery

The use of a physiological carrier to deliver therapeutics throughout the body to both improve their efficacy while minimising inevitable adverse side effects, is an extremely fascinating perspective. The behaviour of erythrocytes as a delivery system for several classes of molecules (i.e., proteins, including enzymes and peptides, therapeutic agents in the form of nucleotide analogues, glucocorticoid analogues) has been studied extensively as they possess several properties, which make them unique and useful carriers. Furthermore, the possibility of using carrier erythrocytes for selective drug targeting to differentiated macrophages increases the opportunities to treat intracellular pathogens and to develop new drugs. Finally, the availability of an apparatus that permits the encapsulation of drugs into autologous erythrocytes has made this technology available in many clinical settings and competitive with other drug delivery systems.

Macrophage depletion induced by clodronate-loaded erythrocytes

Given the important role of macrophages in various disorders, the transient and organ specific suppression of their functions may benefit some patients. Until now, liposome-encapsulated bisphosphonate clodronate has been extensively proposed to this end. In this paper, we demonstrate that erythrocytes loaded with clodronate can also be effective in macrophage depletion. Here, clodronate was encapsulated in erythrocytes through hypotonic dialysis, isotonic resealing and reannealing to final concentrations of 4.1 +/- 0.4 and 10.1 +/- 0.8 micromol/ml of human and murine erythrocytes, respectively. The ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in vitro and in vivo. In vitro studies on human macrophages showed that a single administration of engineered erythrocytes was able to reduce cell adherence capacity in a time-dependent manner, reaching 50 +/- 4% reduction, 13 days post treatment. The administration of loaded erythrocytes to cultures of murine peritoneal macrophages was able to reduce macrophage adhesion 67 +/- 3%, 48 h post treatment. In vivo, the ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in Swiss and C57BL/6 mice. Swiss mice received 125 microg of clodronate through erythrocytes and 6 days post treatment 69 +/- 7% reduction in the number of adherent peritoneal macrophages and 75 +/- 5% reduction in number of spleen macrophages were observed. C57BL/6 mice received 220 microg clodronate by RBC and 3 and 8 days post treatment 65 +/- 7% reduction in the number of spleen macrophages and the complete depletion of liver macrophages were obtained. In summary, our results indicate that clodronate selectively targeted to the phagocytic cells by a single administration of engineered erythrocytes is able to deplete macrophages, even if not completely. The transient suppression of macrophage functions through clodronate-loaded erythrocytes can be used in many biomedical phenomena and research applications.

Low doses of dexamethasone constantly delivered by autologous erythrocytes slow the progression of lung disease in cystic fibrosis patients

OBJECTIVE

To evaluate the safety and efficacy of the administration of low doses of glucocorticoids in patients with cystic fibrosis (CF) by using autologous erythrocytes loaded with dexamethasone 21-phosphate.

STUDY DESIGN

Nine consecutive CF patients (patients nos. 1-9) received autologous erythrocytes loaded with increasing amounts of dexamethasone 21-phosphate to obtain a slow delivery of dexamethasone in circulation. The appearance of possible adverse effects, the reproducibility of the procedure, and the dexamethasone pharmacokinetics were evaluated. Subsequently, patient no. 9 and eight additional patients (patient nos. 10-17) received dexamethasone 21-phosphate-loaded erythrocytes at 1-month intervals to evaluate the efficacy of continuous release in circulation of low doses of dexamethasone.

RESULTS

Erythrocytes from CF patients can be processed to be loaded with increasing dexamethasone 21-P concentrations. Once reinfused in respective donors, a slow and prolonged delivery of dexamethasone in the blood stream was measured up to 28 days. Repeated administrations of drug-loaded erythrocytes at 4-week intervals for 15 months showed that very low doses of glucocorticoids provide significant improvement in FEV1 values and significant reduction of infective relapses due to Pseudomonas aeruginosa without adverse effects.

CONCLUSIONS

The administration of very low doses of glucocorticoids using autologous erythrocytes is possible, with benefits for patients and without side effects. This method is likely to be extended to other chronic diseases.

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.