Low-oxygen-affinity red cells produced in a large-volume, continuous-flow electroporation system

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.

A Flow-Through Cell Electroporation Device for Rapidly and Efficiently Transfecting Massive Amounts of Cells in vitro and ex vivo

Continuous cell electroporation is an appealing non-viral approach for genetically transfecting a large number of cells. Yet the traditional macro-scale devices suffer from the unsatisfactory transfection efficiency and/or cell viability due to their high voltage, while the emerging microfluidic electroporation devices is still limited by their low cell processing speed. Here we present a flow-through cell electroporation device integrating large-sized flow tube and small-spaced distributed needle electrode array. Relatively large flow tube enables high flow rate, simple flow characterization and low shear force, while well-organized needle array electrodes produce an even-distributed electric field with low voltage. Thus the difficulties for seeking the fine balance between high flow rate and low electroporation voltage were steered clear. Efficient in vitro electrotransfection of plasmid DNA was demonstrated in several hard-to-transfect cell lines. Furthermore, we also explored ex vivo electroporated mouse erythrocyte as the carrier of RNA. The strong ability of RNA loading and short exposure time of freshly isolated cells jointly ensured a high yield of valid carrier erythrocytes, which further successfully delivered RNA into targeted tissue. Both in vitro and ex vivo electrotransfection could be accomplished at high cell processing speed (20 million cells per minute) which remarkably outperforms previous devices.

Drug-loaded erythrocytes: on the road toward marketing approval

Erythrocyte drug encapsulation is one of the most promising therapeutic alternative approaches for the administration of toxic or rapidly cleared drugs. Drug-loaded erythrocytes can operate through one of the three main mechanisms of action: extension of circulation half-life (bioreactor), slow drug release, or specific organ targeting. Although the clinical development of erythrocyte carriers is confronted with regulatory and development process challenges, industrial development is expanding. The manufacture of this type of product can be either centralized or bedside based, and different procedures are employed for the encapsulation of therapeutic agents. The major challenges for successful industrialization include production scalability, process validation, and quality control of the released therapeutic agents. Advantages and drawbacks of the different manufacturing processes as well as success key points of clinical development are discussed. Several entrapment technologies based on osmotic methods have been industrialized. Companies have already achieved many of the critical clinical stages, thus providing the opportunity in the future to cover a wide range of diseases for which effective therapies are not currently available.

Localized increase of tissue oxygen tension by magnetic targeted drug delivery

Hypoxia is the major hindrance to successful radiation therapy of tumors. Attempts to increase the oxygen (O2) tension (PO2) of tissue by delivering more O2 have been clinically disappointing, largely due to the way O2 is transported and released by the hemoglobin (Hb) within the red blood cells (RBCs). Systemic manipulation of O2 transport increases vascular resistance due to metabolic autoregulation of blood flow to prevent over oxygenation. This study investigates a new technology to increase O2 delivery to a target tissue by decreasing the Hb-O2 affinity of the blood circulating within the targeted tissue. As the Hb-O2 affinity decreases, the tissue PO2 to satisfy tissue O2 metabolic needs increases without increasing O2 delivery or extraction. Paramagnetic nanoparticles (PMNPs), synthetized using gadolinium oxide, were coated with the cell permeable Hb allosteric effector L35 (3,5-trichlorophenylureido-phenoxy-methylpropionic acid). L35 decreases Hb affinity for O2 and favors the release of O2. The L35-coated PMNPs (L35-PMNPs) were intravenously infused (10 mg kg(-1)) to hamsters instrumented with the dorsal window chamber model. A magnetic field of 3 mT was applied to localize the effects of the L35-PMNPs to the window chamber. Systemic O2 transport characteristics and microvascular tissue oxygenation were measured after administration of L35-PMNPs with and without magnetic field. The tissue PO2 in untreated control animals was 25.2 mmHg. L35-PMNPs without magnetic field decreased tissue PO2 to 23.4 mmHg, increased blood pressure, and reduced blood flow, largely due to systemic modification of Hb-O2 affinity. L35-PMNPs with magnetic field increased tissue PO2 to 27.9 mmHg, without systemic or microhemodynamic changes. These results indicate that localized modification of Hb-O2 affinity can increase PO2 of target tissue without affecting systemic O2 delivery or triggering O2 autoregulation mechanisms. This technology can be used to treat local hypoxia and to increase O2 in tumors, enhancing the efficacy of radiation therapies.

Detection of myo-inositol tris pyrophosphate (ITPP) in equine following an administration of ITPP

Myo-Inositol tris pyrophosphate (ITPP) is a powerful allosteric modulator of haemoglobin that increases oxygen-releasing capacity of red blood cells. It is capable of crossing the red blood cell membrane unlike its open polyphosphate analog myo-inositol hexakisphosphate (IHP). Systemic administration of ITPP enhanced the exercise capacity in mice. There have been rumours of its abuse in the horse racing industry to enhance the performance of racing horses. In this paper, the detection of ITPP in equine plasma and urine after an administration of ITPP is reported. A Standardbred mare was administered 200 mg of ITPP intravenously. Urine and plasma samples were collected up to 120 h post administration and analyzed for ITPP by liquid chromatography-tandem mass spectrometry. ITPP was detected in post administration plasma samples up to 6 hours. The peak concentration was detected at 5 min post administration. In urine, ITPP was detected up to 24 h post administration. The peak concentration was detected at 1.5 h post administration.

Inositol hexaphosphate-loaded red blood cells prevent in vitro sickling

BACKGROUND

Hypoxia is a major cause of painful vaso-occlusive crisis in sickle cell disease (SCD). Simple transfusion and red blood cell (RBC) exchange are commonly used as preventive therapies whose aim is to dilute hemoglobin (Hb)S-containing RBCs (SS-RBCs) with normal RBCs (AA-RBCs) to prevent sickling. We hypothesized that the effectiveness of transfusion could be improved by the encapsulation of inositol hexaphosphate (IHP), an allosteric Hb effector, in transfused AA-RBCs. Indeed, apart from their diluting effect on SS-RBCs, IHP-loaded RBCs (IHP-RBCs) with increased oxygen release capacity could palliate in vivo oxygen deprivation and reduce sickling.

STUDY DESIGN AND METHODS

The study was designed to investigate the therapeutic effect of IHP-RBCs transfusion on in vitro sickling of SS-RBCs collected from 20 SCD patients. Patients' RBCs were diluted with various proportions of IHP-RBCs or AA-RBCs (processed or stored RBCs as controls). Resulting suspensions were subjected to deoxygenation followed by partial reoxygenation at 5% oxygen. Sickling was evaluated by microscopy.

RESULTS

Stored RBCs (50% dose) used to mimic simple transfusion exhibited a poor antisickling effect (5.6%) and a low response rate (65%). In contrast, IHP-RBCs treatment was seven times more effective resulting in 35% of sickling reduction and a 94% response rate. Sickling was inhibited in a dose-dependent manner: 9.9, 25.1, and 35.0% for IHP-RBCs in percentages of 10, 30, and 50%, respectively.

CONCLUSION

Our results indicate that IHP-RBCs prevent in vitro sickling and suggest that it could improve conventional transfusion therapy in terms of transfused volume, frequency, and efficacy.

Enhanced exercise capacity in mice with severe heart failure treated with an allosteric effector of hemoglobin, myo-inositol trispyrophosphate

A major determinant of maximal exercise capacity is the delivery of oxygen to exercising muscles. myo-Inositol trispyrophosphate (ITPP) is a recently identified membrane-permeant molecule that causes allosteric regulation of Hb oxygen binding affinity. In normal mice, i.p. administration of ITPP (0.5-3 g/kg) caused a dose-related increase in the oxygen tension at which Hb is 50% saturated (p50), with a maximal increase of 31%. In parallel experiments, ITPP caused a dose-related increase in maximal exercise capacity, with a maximal increase of 57 +/- 13% (P = 0.002). In transgenic mice with severe heart failure caused by cardiac-specific overexpression of G alpha q, i.p. ITPP increased exercise capacity, with a maximal increase of 63 +/- 7% (P = 0.005). Oral administration of ITPP in drinking water increased Hb p50 and maximal exercise capacity (+34 +/- 10%; P < 0.002) in normal and failing mice. Consistent with increased tissue oxygen availability, ITPP decreased hypoxia inducible factor-1alpha mRNA expression in myocardium. It had no effect on myocardial contractility in isolated mouse cardiac myocytes and did not affect arterial blood pressure in vivo in mice. Thus, ITPP decreases the oxygen binding affinity of Hb, increases tissue oxygen delivery, and increases maximal exercise capacity in normal mice and mice with severe heart failure. ITPP is thus an attractive candidate for the therapy of patients with reduced exercise capacity caused by heart failure.

Optimization of a gene electrotransfer method for mesenchymal stem cell transfection

Gene electrotransfer is an efficient and reproducible nonviral gene transfer technique useful for the nonpermanent expression of therapeutic transgenes. The present study established optimal conditions for the electrotransfer of reporter genes into mesenchymal stem cells (MSCs) isolated from rat bone marrow by their selective adherence to tissue-culture plasticware. The electrotransfer of the lacZ reporter gene was optimized by adjusting the pulse electric field intensity, electric pulse type, electropulsation buffer conductivity and electroporation temperature. LacZ electrotransfection into MSCs was optimal at 1500 V cm(-1) with pre-incubation in Spinner's minimum essential medium buffer at 22 degrees C. Under these conditions beta-galactosidase expression was achieved in 29+/-3% of adherent cells 48 h post transfection. The kinetics of beta-galactosidase activity revealed maintenance of beta-galactosidase production for at least 10 days. Moreover, electroporation did not affect the MSC potential for multidifferentiation; electroporated MSCs differentiated into osteoblastic, adipogenic and chondrogenic lineages to the same extent as cells that were not exposed to electric pulses. Thus, this study demonstrates the feasibility of efficient transgene electrotransfer into MSCs while preserving cell viability and multipotency.

Modulation of perfusion and oxygenation by red blood cell oxygen affinity during acute anemia

Responses to exchange transfusion using red blood cells (RBCs) with modified hemoglobin (Hb) oxygen (O(2)) affinity were studied in the hamster window chamber model during acute anemia to determine its role on microvascular perfusion and tissue oxygenation. Allosteric effectors were introduced in the RBCs by electroporation. Inositol hexaphosphate (IHP) and 5-hydroxymethyl-2-furfural (5HMF) were used to decrease and increase Hb-O(2) affinity. In vitro P50s (partial pressure of O(2) at 50% Hb saturation) were modified to 10, 25, 45, and 50 mm Hg (normal P50 is 32 mm Hg). Allosteric effectors also decreased the Hill coefficient. Anemic condition was induced by isovolemic hemodilution exchanges using 6% dextran 70 kD to 18% hematocrit (Hct). Modified RBCs (at 18% Hct in 5% albumin solution) were infused by exchange transfusion of 35% of blood volume. Systemic parameters, microvascular perfusion, capillary perfusion (functional capillary density, FCD), and microvascular Po(2) levels were measured. RBcs with P50 of 45 mm Hg increased tissue Po(2) and decreased O(2) delivery (Do(2)) and extraction (Vo(2)) and RBCs with P50 of 60 mmHg reduced FCD, microvascular flow, tissue Po(2), Do(2) and Vo(2). Erythrocytes with increased Hb-O(2) affinity maintained hemodynamic conditions, Do(2) and decreased tissue Po(2). This study shows that in an anemic condition, maximal tissue Po(2) does not correspond to maximal Do(2) and Vo(2).

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.

Simulations of nanopore formation and phosphatidylserine externalization in lipid membranes subjected to a high-intensity, ultrashort electric pulse

A combined MD simulator and time dependent Laplace solver are used to analyze the electrically driven phosphatidylserine externalization process in cells. Time dependent details of nanopore formation at cell membranes in response to a high-intensity (100 kV/cm), ultrashort (10 ns) electric pulse are also probed. Our results show that nanosized pores could typically be formed within about 5 ns. These predictions are in very good agreement with recent experimental data. It is also demonstrated that defect formation and PS externalization in membranes should begin on the anode side. Finally, the simulations confirm that PS externalization is a nanopore facilitated event, rather than the result of molecular translocation across the trans-membrane energy barrier.

Inositol tripyrophosphate: a new membrane permeant allosteric effector of haemoglobin

Nine inositol tripyrophosphate (ITPP) salts have been synthesized. Their ability to act as allosteric effectors of haemoglobin (Hb) has been measured in vitro with free Hb and whole blood. All the synthesized compounds bound to free Hb and were also able to cross, to a certain extent, the plasma membrane of the red blood cells (RBCs) in whole blood samples, lowering the affinity of Hb for oxygen. The oxy-haemoglobin dissociation curves were significantly shifted towards higher values of oxygen partial pressures, both for free Hb and for intracellular Hb in whole blood.

Energy-landscape-model analysis for irreversibility and its pulse-width dependence in cells subjected to a high-intensity ultrashort electric pulse

We provide a simple, but physical analysis for cell irreversibility and apoptosis in response to an ultrashort (nanosecond), high-intensity electric pulse. Our approach is based on an energy landscape model for determining the temporal evolution of the configurational probability function p(q). The primary focus is on obtaining qualitative predictions of a pulse width dependence to apoptotic cell irreversibility that has been observed experimentally. The analysis couples a distributed electrical model for current flow with the Smoluchowski equation to provide self-consistent, time-dependent transmembrane voltages. The model captures the essence of the experimentally observed pulse-width dependence, and provides a possible physical picture that depends only on the electrical trigger. A number of interesting features are predicted.

Highly efficient, large volume flow electroporation

Electroporation is widely used to transfect and load cells with various molecules. Traditional electroporation using a static mode is typically restricted to volumes less than 1 mL, which limits its use in clinical and industrial bioprocessing applications. Here we report efficient, large volume transfection results by using a scalable-volume electroporation system. Suspended (Jurkat) and adherent cells (10T1/2 and Huh-7) were tested. A large macromolecule, FITC-conjugated dextran (MW=500 kD) was used to measure cell uptake, while a plasmid carrying the gene coding for enhanced green fluorescence protein (eGFP) was used to quantitate the flow electrotransfection efficiency as determined by flow cytometry. The flow electroloading efficiency of FITC-dextran was >90%, while the cell viability was highly maintained (>90%). High flow electrotransfection efficiency (up to 75%) and cell viability (up to 90%) were obtained with processing volumes ranging from 1.5 to 50 mL. No significant difference of electrotransfection efficiency was observed between flow and static electrotransfection. When 50 mL of cell volume was processed and samples collected at different time points during electroporation, the transgene expression and cell viability results were identical. We also demonstrated that DNA plasmid containing EBNA1-OriP elements from Epstein-Barr virus were more efficient in transgene expression than standard plasmid without the elements (at least 500 too 1000-fold increase in expression level). Finally, to examine the feasibility of utilizing flow electrotransfected cells as a gene delivery vehicle, 10T1/2 cells were transfected with a DNA plasmid containing the gene coding for mIL12. mIL12 transfected cells were injected subcutaneously into mice, and produced functional mIL12, as demonstrated by anti-angiogenic activity. This is the first demonstration of efficient, large volume, flow electroporation and the in vivo efficacy of flow electrotransfected cells. This technology may be useful for clinical gene therapy and large-scale bioprocesses.

Transport of the highly charged myo-inositol hexakisphosphate molecule across the red blood cell membrane: a phase transfer and biological study

To address the problem of delivering highly charged small molecules, such as phytic acid (InsP(6) or IHP), across biological membranes, we investigated an approach based on a non-covalent interaction between transport molecule(s) and IHP. Thus, we synthesized a collection of compounds containing IHP ionically bound to lipophilic (but non-lipidic) ammonium or poly-ammonium cations. First, we assessed the ability of these water-soluble salts to cross a biological membrane by measuring the partition coefficients between human serum and 1-octanol. In view of the ability of IHP to act as potent effector for oxygen release, the O(2)-hemoglobin dissociation curves were then measured for the most efficient salts on whole blood. From both the biological and the physical properties of IHP-ammonium salts we determined that cycloalkylamines (or poly-amines) were the best transport molecules, especially cycloheptyl- and cyclooctylamine. Indeed, the octanol/serum partition coefficient of IHP undecacyclooctylammonium salt, is superior to 1, which is very favorable for potential uptake into the red blood cell membrane. A qualitative correlation was found between the partitioning experiments and the biological evaluations performed on whole blood.

Elimination of free-living amoebae in fresh water with pulsed electric fields

This study investigates the effects of pulsed electric fields on the inactivation of trophozoite form of Naegleria lovaniensis Ar9M-1 in batch and flow processes, systematically examining the lethal effect of field strength, pulse duration, number of pulses, and pulse frequency. Our results show that amoebae eradication is modulated by pulse parameters, composition of the pulsing medium, and physiological state of the cells. Cell survival is not related to the energy delivered to the cell suspension during the electrical treatment. For a given energy a strong field applied for a short cumulative pulse duration affects viability more than a weak field with a long cumulative pulsation. We also determine the optimal electrical conditions to obtain an inactivation rate higher than 95% while using the least energy. Flow processes allow to treat large-scale volumes. Our results show that the most efficient flow process for amoeba eradication requires a field parallel to the flow. Pulsed electric fields are a new and attractive method for inactivating amoebae in large volumes of fresh water.

Low-O(2) affinity erythrocytes improve performance of ischemic myocardium

O(2) transport and O(2) diffusion interact in providing O(2) to tissue, but the extent to which diffusion may be critical in the heart is unclear. If O(2) diffusion limits mitochondrial oxygenation, a change in blood O(2) affinity at constant total O(2) transport should alter cardiac O(2) consumption (VO(2)) and function. To test this hypothesis, we perfused isolated isovolumically working rabbit hearts with erythrocytes at physiological blood-gas values and P(50) (PO(2) required to half-saturate hemoglobin) values at pH of 7.4 of 17 +/- 1 Torr (2,3-bisphosphoglycerate depletion) and 33 +/- 5 Torr (inositol hexaphosphate incorporation). When perfused at 40 and 20% of normal coronary flow, mean VO(2) decreased from the control value by 37 and 46% (P < 0.001), and function, expressed as cardiac work, decreased by 38 and 52%, respectively (P < 0.001). Perfusion at higher P(50) during low-flow ischemia improved VO(2) by 20% (P < 0.001) and function by 36% (P < 0.02). There was also modest improvement at basal flow (P < 0.02 and P < 0.002, respectively). The improvement in VO(2) and function due to the P(50) increase demonstrates the importance of O(2) diffusion in this cardiac ischemia model.

Prediction and optimization of gene transfection and drug delivery by electroporation

Although electroporation is widely used for laboratory gene transfection and gaining increased importance for nonviral gene therapy, it is generally employed using trial-and-error optimization schemes for lack of methods to predict electroporation's effects on cells. Therefore, we used a statistical approach to quantitatively predict molecular uptake and cell viability following electroporation and show that it predicts both in vitro and in vivo results for a wide range of molecules, including DNA, in 60 different cell types. Mechanistically, this broad predictive ability suggests that electroporation is mediated primarily by lipid bilayer structure and only secondarily by cell-specific characteristics. For gene therapy applications, this approach should facilitate rational design of electroporation protocols.

In vitro study of alcohol dehydrogenase and acetaldehyde dehydrogenase encapsulated into human erythrocytes by an electroporation procedure

The optimal conditions for electroporated/resealed loading of alcohol dehydrogenase (ADH) and/or acetaldehyde dehydrogenase (ALDH) into human erythrocytes were established prior to the study, with the following characteristics: 300 V, 1 ms pulse time, eight pulses every 15 min and 1 h resealing at 37 degreesC. High encapsulation yield and carrier cell recoveries were achieved. Cell volumes increase while hemoglobin contents decrease; in consequence a decrease in cell hemoglobin concentration was observed. A lower hypotonic resistance of loading erythrocytes (throughout osmotic fragility curves) and unaltered oxygen transport capability (as given by oxygen equilibrium curves) were observed. The stability against time (up to 168 h-7 days) of encapsulated individual enzymes, either ADH- or ALDH-red blood cells (RBCs), was studied at 4 degreesC and 37 degreesC, in comparison with that of free enzyme solutions. Both enzymes were released from carrier RBCs to the incubation medium. The stability of carrier RBCs was studied under similar conditions. Non-significant variations in hematological parameters were observed. However, the hemoglobin derivative forms showed modifications. The continuous degradation of ethanol by ADH-RBCs and coencapsulated ADH- and ALDH-RBCs, as a function of time (up to 70 h) suggests the use of these carrier RBCs as agents for complete metabolization of ethanol. The mentioned properties bare the possibility of using ADH and ALDH as carrier systems in in vivo situations.