Future generations of red blood cell substitutes

Microfluidic dual picoinjection based encapsulation of hemoglobin in alginate microcapsules reinforced by a poly(L-lysine)-g-poly(ethylene glycol)

Hemoglobin (Hb) encapsulation inside polysaccharide hydrogels has been considered a possible red blood cell (RBC) surrogate in transfusiology. Here we report on the microfluidic dual picoinjection assisted synthesis of Hb encapsulated alginate-poly(L-lysine)-g-poly(ethylene glycol) beads. This process is realized by the on-chip injections of blended Hb alginate solutions in emulsified aqueous calcium chloride (CaCl₂) droplets followed by a subsequent injection of an aqueous PLL-g-PEG into each emulsified aqueous droplet. The proposed fabrication approach was realized using a flow-focusing and two picoinjection sites in a single PDMS device. Aqueous CaCl₂ solution was emulsified and infused with Hb-alginate solution as the squeezed droplet passed through the first picoinjection site. The injection of PLL-g-PEG to reinforce the microgel and minimize the protein leaching was realized in the second picoinjection site located downstream from the first in the same microfluidic channel. In this process, monodisperse Hb-alginate-PLL-g-PEG particles with a diameter around the size of RBCs (9 μm) were obtained with around 80% of the 7.5 mg ml^-1 Hb included in the injected aqueous alginate retaining in the obtained microparticles. Microparticles with Hb loading (32.8 pg per bead) and retention (28.8 pg per bead) over a week of storage at 4 °C are in accordance with the average amount of Hb per RBC. The Hb-alginate-PLL-g-PEG microbeads fabricated in the size range of RBCs are significant for further exploration.

Rationale utilization of phospholipid excipients: a distinctive tool for progressing state of the art in research of emerging drug carriers

Phospholipids have a high degree of biocompatibility and are deemed ideal pharmaceutical excipients in the development of lipid-based drug delivery systems, because of their unique features (permeation, solubility enhancer, emulsion stabilizer, micelle forming agent, and the key excipients in solid dispersions) they can be used in a variety of pharmaceutical drug delivery systems, such as liposomes, phytosomes, solid lipid nanoparticles, etc. The primary usage of phospholipids in a colloidal pharmaceutical formulation is to enhance the drug's bioavailability with low aqueous solubility [i.e. Biopharmaceutical Classification System (BCS) Class II drugs], Membrane penetration (i.e. BCS Class III drugs), drug uptake and release enhancement or modification, protection of sensitive active pharmaceutical ingredients (APIs) from gastrointestinal degradation, a decrease of gastrointestinal adverse effects, and even masking of the bitter taste of orally delivered drugs are other uses. Phospholipid-based colloidal drug products can be tailored to address a wide variety of product requirements, including administration methods, cost, product stability, toxicity, and efficacy. Such formulations that are also a cost-effective method for developing medications for topical, oral, pulmonary, or parenteral administration. The originality of this review work is that we comprehensively evaluated the unique properties and special aspects of phospholipids and summarized how the individual phospholipids can be utilized in various types of lipid-based drug delivery systems, as well as listing newly marketed lipid-based products, patents, and continuing clinical trials of phospholipid-based therapeutic products. This review would be helpful for researchers responsible for formulation development and research into novel colloidal phospholipid-based drug delivery systems.

Künstliche Sauerstofftransporter können mehr als Sauerstoff liefern

Zum gegenwärtigen Zeitpunkt ist in der EU und den USA kein artifizieller Sauerstofftransporter zugelassen. Hämoglobin-basierte Sauerstoff-Carrier (HBOC) sind bereits seit Jahrzehnten Gegenstand wissenschaftlicher Untersuchungen. Ein wesentliches Hindernis bei der Zulassung war bisher der Anspruch der Entwickler, einen universell einsetzbaren Blutersatz zu produzieren. Die Beschränkung auf eine Indikation scheint erfolgversprechender zu sein. Der Ansatz, nicht nur Sauerstoff von der Lunge zum Gewebe, sondern auch der Abtransport von Kohlendioxid vom Gewebe zur Lunge zu transportieren, der effektiver als mit Erythrozyten durchgeführt werden kann, erscheint besonders attraktiv. Aufgrund vielversprechender präklinischer sowie klinischer Untersuchungen besteht die Hoffnung, dass in absehbarer Zeit auch in der EU künstliche Sauerstofftransporter für therapeutische Zwecke zur Verfügung stehen werden.

Hemoglobin-based Oxygen Carriers: Current State-of-the-art and Novel Molecules

In blood, the primary role of red blood cells (RBCs) is to transport oxygen via highly regulated mechanisms involving hemoglobin (Hb). Hb is a tetrameric porphyrin protein comprising of two α- and two β-polypeptide chains, each containing an iron-containing heme group capable of binding one oxygen molecule. In military as well as civilian traumatic exsanguinating hemorrhage, rapid loss of RBCs can lead to suboptimal tissue oxygenation and subsequent morbidity and mortality. In such cases, transfusion of whole blood or RBCs can significantly improve survival. However, blood products including RBCs present issues of limited availability and portability, need for type matching, pathogenic contamination risks, and short shelf-life, causing substantial logistical barriers to their prehospital use in austere battlefield and remote civilian conditions. While robust research is being directed to resolve these issues, parallel research efforts have emerged toward bioengineering of semisynthetic and synthetic surrogates of RBCs, using various cross-linked, polymeric, and encapsulated forms of Hb. These Hb-based oxygen carriers (HBOCs) can potentially provide therapeutic oxygenation when blood or RBCs are not available. Several of these HBOCs have undergone rigorous preclinical and clinical evaluation, but have not yet received clinical approval in the USA for human use. While these designs are being optimized for clinical translations, several new HBOC designs and molecules have been reported in recent years, with unique properties. The current article will provide a comprehensive review of such HBOC designs, including current state-of-the-art and novel molecules in development, along with a critical discussion of successes and challenges in this field.

Artificial Blood: The History and Current Perspectives of Blood Substitutes

Blood transfusions are one of the most common procedures performed in hospitalized patients. Yet, despite all of the measures taken to ensure the safety of the blood supply, there are known risks associated with transfusions, including infectious and noninfectious complications. Meanwhile, issues with blood product availability, the need for compatibility testing, and the storage and transport requirements of blood products, have presented challenges for the administration of blood transfusions. Additionally, there are individuals who do not accept blood transfusions (e.g., Jehovah's Witnesses). Therefore, there is a need to develop alternative agents that can reliably and safely replace blood. However, although there have been many attempts to develop blood substitutes over the years, there are currently no such products available that have been approved by the United States Food and Drug Administration (FDA). However, a more-recently developed hemoglobin-based oxygen carrier has shown promise in early clinical trials and has achieved the status of "Orphan Drug" under the FDA.

Bio-inspired nanomedicine strategies for artificial blood components

Blood is a fluid connective tissue where living cells are suspended in noncellular liquid matrix. The cellular components of blood render gas exchange (RBCs), immune surveillance (WBCs) and hemostatic responses (platelets), and the noncellular components (salts, proteins, etc.) provide nutrition to various tissues in the body. Dysfunction and deficiencies in these blood components can lead to significant tissue morbidity and mortality. Consequently, transfusion of whole blood or its components is a clinical mainstay in the management of trauma, surgery, myelosuppression, and congenital blood disorders. However, donor-derived blood products suffer from issues of shortage in supply, need for type matching, high risks of pathogenic contamination, limited portability and shelf-life, and a variety of side-effects. While robust research is being directed to resolve these issues, a parallel clinical interest has developed toward bioengineering of synthetic blood substitutes that can provide blood's functions while circumventing the above problems. Nanotechnology has provided exciting approaches to achieve this, using materials engineering strategies to create synthetic and semi-synthetic RBC substitutes for enabling oxygen transport, platelet substitutes for enabling hemostasis, and WBC substitutes for enabling cell-specific immune response. Some of these approaches have further extended the application of blood cell-inspired synthetic and semi-synthetic constructs for targeted drug delivery and nanomedicine. The current study provides a comprehensive review of the various nanotechnology approaches to design synthetic blood cells, along with a critical discussion of successes and challenges of the current state-of-art in this field. WIREs Nanomed Nanobiotechnol 2017, 9:e1464. doi: 10.1002/wnan.1464 For further resources related to this article, please visit the WIREs website.

Application of HBOCs electrophoretic method to detect a new blood substitute derived from the giant extracellular haemoglobin of lugworm

Manipulation of blood and blood components is prohibited in sports by the World Anti-Doping Agency (WADA). This includes the use of blood substitutes to increase oxygen transport, like haemoglobin-based oxygen carriers (HBOCs), which are compounds derived from haemoglobin. Despite their medical interest, the first generation of HBOCs had serious adverse effects and was abandoned. However, new studies are now exploiting the properties of marine worm haemoglobins, which circulate as giant extracellular complexes with high oxygen-binding capacities. HEMOXYCarrier® (HC), developed by Hemarina, is one of the most advanced and promising HBOCs, and HC may become a tempting doping tool for athletes in the future. Here, HC detection in plasma/serum was evaluated with the method used to detect the first HBOCs, based on electrophoresis and heme peroxidase properties. An HC-derived product was identified in human plasma up to 72 h after in vitro incubation at 37 °C. HC degradation also induced methemalbumin formation. After injecting HC at the effective dose of 200 mg/kg into mice, the HC-derived product was detected only for a few hours and no accumulation of methemalbumin was observed. Due to this limited detection window in vivo, measuring specific worm globin degradation products by mass spectrometry might be an alternative for future anti-doping analyses. Copyright © 2016 John Wiley & Sons, Ltd.

Perfluorodecalin-soluble fluorescent dyes for the monitoring of circulating nanocapsules with intravital fluorescence microscopy

Perfluorodecalin (PFD) is an established artificial oxygen carrier due to its physical capability to solve the respiratory gases oxygen and carbon dioxide. PFD-filled poly(n-butyl-cyanoacrylate) (PACA) nanocapsules are already discussed as effective artificial oxygen carriers, and their principal suitability for intravenous administration had been shown. To further elucidate their action in vivo, it is imperative to characterise their preclinical safety and particularly their biodistribution. For these purposes, intravital fluorescence microscopy would display an attractive technique in order to monitor the PACA nanocapsules in vivo, but unfortunately, it is impossible to stain the PACA nanocapsules with a fluorescent dye fulfilling special criteria required for in vivo microscopy. In order to develop such a dye, a long-chained fluorinated thiol was used to modify a BODIPY derivative that is a highly fluorescent organic compound belonging to the difluoro-boraindacene family, as well as to functionalise mesoscopic systems, such as CdSe/ZnS-quantum dots and gold nanoparticles. Furthermore, a functionalisation of porphyrin derivatives was investigated by placing divalent ions in the centre of these systems. Due to the high solubility of all synthesised dyes in PFD, it should be possible to stain PFD-filled particles in general. However, only the functionalised BODIPY derivative was suitable for in vivo monitoring of the PFD-filled PACA nanocapsules.

Development of recombinant hemoglobin-based oxygen carriers

SIGNIFICANCE

The worldwide blood shortage has generated a significant demand for alternatives to whole blood and packed red blood cells for use in transfusion therapy. One such alternative involves the use of acellular recombinant hemoglobin (Hb) as an oxygen carrier.

RECENT ADVANCES

Large amounts of recombinant human Hb can be expressed and purified from transgenic Escherichia coli. The physiological suitability of this material can be enhanced using protein-engineering strategies to address specific efficacy and toxicity issues. Mutagenesis of Hb can (i) adjust dioxygen affinity over a 100-fold range, (ii) reduce nitric oxide (NO) scavenging over 30-fold without compromising dioxygen binding, (iii) slow the rate of autooxidation, (iv) slow the rate of hemin loss, (v) impede subunit dissociation, and (vi) diminish irreversible subunit denaturation. Recombinant Hb production is potentially unlimited and readily subjected to current good manufacturing practices, but may be restricted by cost. Acellular Hb-based O(2) carriers have superior shelf-life compared to red blood cells, are universally compatible, and provide an alternative for patients for whom no other alternative blood products are available or acceptable.

CRITICAL ISSUES

Remaining objectives include increasing Hb stability, mitigating iron-catalyzed and iron-centered oxidative reactivity, lowering the rate of hemin loss, and lowering the costs of expression and purification. Although many mutations and chemical modifications have been proposed to address these issues, the precise ensemble of mutations has not yet been identified.

FUTURE DIRECTIONS

Future studies are aimed at selecting various combinations of mutations that can reduce NO scavenging, autooxidation, oxidative degradation, and denaturation without compromising O(2) delivery, and then investigating their suitability and safety in vivo.

Modulation of oxidative stability of haemoglobin inside liposome-encapsulated haemoglobin

The major hurdle in the formulation of liposome-encapsulated haemoglobin (LEH) is the oxidation of haemoglobin (Hb) into methaemoglobin during storage and after administration. In order to reduce this oxidative degradation, we tested various reducing conditions in the presence of catalase. We found that at 37°C more than 50% of Hb oxidized to methaemoglobin within 24 h, whereas in presence of catalase, the oxidation was significantly reduced. The effect of catalase was further enhanced by a reduction mixture containing β-NAD, d-glucose, adenine, inosine, MgCl2, KCl, KH2PO4 and Na2HPO4; only 14% methaemoglobin was generated in the presence of catalase and reduction mixture. Contrary to the expectation, glutathione, deferoxamine and homocysteine enhanced Hb oxidation. The presence of CRM inside liposomes (250 nm) significantly decreased Hb oxidation. The results suggest that catalase and a well-defined mixture of co-factors may help control Hb oxidation for improvement in the functional life of LEH.

Pathological conditions involving extracellular hemoglobin: molecular mechanisms, clinical significance, and novel therapeutic opportunities for α(1)-microglobulin

Hemoglobin (Hb) is the major oxygen (O(2))-carrying system of the blood but has many potentially dangerous side effects due to oxidation and reduction reactions of the heme-bound iron and O(2). Extracellular Hb, resulting from hemolysis or exogenous infusion, is shown to be an important pathogenic factor in a growing number of diseases. This review briefly outlines the oxidative/reductive toxic reactions of Hb and its metabolites. It also describes physiological protection mechanisms that have evolved against extracellular Hb, with a focus on the most recently discovered: the heme- and radical-binding protein α(1)-microglobulin (A1M). This protein is found in all vertebrates, including man, and operates by rapidly clearing cytosols and extravascular fluids of heme groups and free radicals released from Hb. Five groups of pathological conditions with high concentrations of extracellular Hb are described: hemolytic anemias and transfusion reactions, the pregnancy complication pre-eclampsia, cerebral intraventricular hemorrhage of premature infants, chronic inflammatory leg ulcers, and infusion of Hb-based O(2) carriers as blood substitutes. Finally, possible treatments of these conditions are discussed, giving a special attention to the described protective effects of A1M.

Highly loaded hemoglobin spheres as promising artificial oxygen carriers

Seeking safe and effective artificial blood substitutes based on hemoglobin (Hb) as oxygen carriers is an important topic. A significant challenge is to enhance the loading content of Hb in a well-defined structure. Here we report a facile and controllable avenue to fabricate Hb spheres with a high loading content by templating decomposable porous CaCO(3) particles in collaboration with covalent layer-by-layer assembly technique. The surface of the Hb spheres was further chemically modified by biocompatible polyethylene glycol to protect and stabilize the system. Multiple characterization techniques were employed to reveal the loading and density of Hb in an individual CaCO(3) particle. The results demonstrate that the strategy developed in this work is effective and flexible for construction of the highly loaded Hb spheres. More importantly, such Hb spheres retain their carrying-releasing oxygen function. It may thus have great potential to develop Hb spheres with highly loaded content as realistic artificial blood substitutes in the future.

Hemoglobin vesicle improves recovery of cardiac function after ischemia-reperfusion by attenuating oxidative stress in isolated rat hearts

Hemoglobin vesicle (HbV) could be a useful blood substitute in emergency medicine. The aim of this study was to clarify the effects of HbV on cardiac function after ischemia-reperfusion (I/R) ex vivo. Isolated rat hearts were perfused according to the Langendorff method. An ischemia-reperfusion group (n = 6) was subjected to 25 minutes of global ischemia and 30 minutes of reperfusion. HbV (hemoglobin, 0.33 g/dL) was perfused before ischemia-reperfusion for 10 minutes (HbV group, n = 6). Hemodynamics were monitored, and tissue glutathione contents were measured. The redox state of reactive thiols in cardiac tissues was assessed by the biotinylated iodoacetamide labeling method. Left ventricular developed pressure was significantly recovered in the HbV group after 30 minutes of reperfusion (56.3 ± 2.8 mm Hg vs. ischemia-reperfusion group 27.0 ± 8.0 mm Hg, P < 0.05). Hemodynamic changes induced by HbV were similar to those observed when N-nitro-L-arginine methyl ester was perfused for 10 minutes before ischemia-reperfusion (L-NAME group). The oxidized glutathione contents of cardiac tissues significantly decreased, and biotinylated iodoacetamide labeling of thiols was maintained in both the HbV and the L-NAME groups. HbV improved the recovery of cardiac function after ischemia-reperfusion in isolated rat hearts. This mechanism is dependent on functional protection against thiol oxidation.

Polymer/hemoglobin assemblies: biodegradable oxygen carriers for artificial red blood cells

In routine clinical procedures, blood transfusion is now suffering from the defects of the blood products, like cross-matching, short storage time and virus infection. Various blood substitutes have been designed by researchers through continual efforts. With recent progress in nanotechnology, new types of artificial red blood cells with cellular structure are available. This article aims to describe some artificial red blood cells which encapsulate or conjugate hemoglobin molecules through various approaches, especially the nanoscale self-assembly technique, to mitigate the adverse effects of free hemoglobin molecules. These types of artificial red blood cell systems, which make use of biodegradable polymers as matrix materials, show advantages over the traditional types.

Genomics and Blood Substitutes for 21st Century Europe (“EuroBloodSubstitutes”)

Blood transfusion is a medical intervention practised throughout the world. Blood is a biologically active material that can transmit diseases (e.g., HIV/AIDS and, perhaps, vCJD). People are becoming increasingly concerned about blood safety, despite improved screening and processing. Consequently, they are reluctant to donate blood or receive transfusions. Such problems can be solved by the development and incorporation into transfusion practices of so-called "blood substitutes" to replace some blood uses. The EuroBloodSubstitutes Project is funded by the European Union Framework 6 Programme to develop a technological platform for producing novel haem proteins and blood substitute components using micro-organisms (bacteria, fungi, yeast) as "cell factories." The Project will focus on bacteria (Escherichia coli), yeast (Pichia pastoris) and, longer-term, filamentous fungi (Aspergillus niger), all organisms used to synthesize commercially important products. The multi-centre Consortium consists of the Universities of (1) Nottingham (UK), (2) Essex (UK), (3) Denmark Technical (Denmark), (4) Lund (Sweden), (5) Milan (Italy), (6) Nancy (France), (7) Parma (Italy), (8) Rome "La Sapienza" (Italy), (9) Semmelweis (Hungary), together with (10) Alligator Bioscience, AB (Sweden), (11) LCC Engineering & Trading GmbH (Switzerland), (12) Scottish National Blood Transfusion Service (UK), and (13) Sanquin Bloodbank (The Netherlands). The EuroBloodSubstitutes Project will be informed by lay and professional stakeholders (e.g., clinicians, blood donors, patient groups, prescribers and policy makers). Outcomes of the Project are (1) the production of an information pack, decision aids and physician training aids, giving balanced overviews of the benefits and risks of transfusion of blood or potential substitutes, and (2) an interactive web site (http//:www.eurobloodsubstitutes.com) for information dissemination. This will improve knowledge and address misunderstandings about transfusion issues in a climate of changing patient expectations on blood safety and benefits of blood substitutes.

Perceptions in Transfusion Medicine: A Pilot Field Study on Risk and Ethics for Blood and Blood Substitutes

A pilot study was undertaken in the UK in February 2005 to identify the perceptions of risk, effectiveness and ethicality of different hypothetical transfusion options, including blood substitutes derived from different sources, among young adults. Forty-nine men and 92 women completed the questionnaire, aging between 18 and 25 years old (mean +/- standard deviation = 19.7 +/- 1.2 years). Twenty-three percent of respondents had donated blood, an average of 3.1 times. The study assessed the perceptions of donor blood versus 3 different types of potential "artificial blood" [i.e. "chemical" (synthetic), "grown from bacteria" (recombinant hemoglobin), or "based on cow blood" (bovine hemoglobin)] on three dimensions, namely risk, effectiveness, and ethicality, each scored on a 1 (least) to 7 (most) Likert-type scale. Donor blood was rated as significantly (P < 0.05) less risky, more effective and more ethical than any of the blood substitutes. The chemical-based blood substitute was rated second least risky, second most effective and second most ethical followed by bacteria grown substitute. The bovine-based blood substitute was rated as significantly riskier, least effective and least ethical. All the blood products differed significantly for perceived ethicality, with donor blood considered as most ethical and a blood substitute derived from bovine blood as least ethical. Judgments of risk correlated negatively with effectiveness (all transfusion options) and ethicality (all the blood substitutes). Overall, these results indicate that donor blood is currently preferred over blood substitutes in the UK and that judgments of risk about different hypothetical transfusion options are related to perceptions of effectiveness and ethicality.

Polyhemoglobin–Tyrosinase, an Oxygen Carrier with Murine B16F10 Melanoma Suppression Properties: A Preliminary Report

Melanoma now represents the fifth most common cancer in North America and it has increased dramatically in the past decade. One of the approaches shows that lowering of tyrosine level can inhibit the growth of melanoma in cell culture and in mice bearing B16BL6 melanoma. However, human cannot tolerate the tyrosine restricted diets for lowering tyrosine due to nausea, vomiting, and severe body weight loss. We therefore prepare a novel soluble polyhemoglobin-tyrosinase complex. Our studies show that this preparation can lower systemic tyrosine level in normal animals. This preparation also prevents the native tyrosinase from having adverse effects and from rapid removal after injection. In cell culture study, we find that this preparation inhibits the growth of murine B16F10 melanoma culture. Furthermore, in animal studies we observe that daily intravenous injection of this polyhemoglobin-tyrosinase preparation significantly delays the growth of B16F10 melanoma in mice, without causing adverse effects or changes in the growth of the treated animals.

A noninvasive method for measuring the oxygen binding-releasing capacity of hemoglobin-loaded polymeric nanoparticles as oxygen carrier

Based on the strong penetration capacity of near infrared lights (NIRs) and different absorption of oxyhemoglobin and deoxyhemoglobin in NIRs region, a novel noninvasive method, with the aid of an airproof-equilibrium apparatus, was developed to determine the oxygen binding-releasing capacity, including oxygen dissociation curve (ODC) and P(50), of the hemoglobin-loaded polymeric nanoparticles (HbP) in this study. The measured ODC of the PLA-PEG HbP was very close to that of the native hemoglobin, and the corresponding P(50) (26.1 mmHg) was also near to the native precursor protein (27.3 mmHg), indicative of the validity of the method proposed. To further verify the method proposed, the oxygen binding-releasing capacity of the HbPs prepared by PCL, PCL-PEG, PLA were also investigated with human blood as control. These results indicated that the method developed here enabled accurate and noninvasive determination of the oxygen binding-releasing capacity of the biodegradable polymeric oxygen carriers.

A novel dynamic heterogeneous phase polymerization reaction for poly-hemoglobin with narrow molecular weight distribution

A dynamic heterogeneous phase polymerization reaction is found to be efficient for controllable cross-link of hemoglobin with glutaraldehyde. The selective absorption of the immobile phase and asymmetry of protein concentration leads to narrowness of the molecular weight distribution and lowness of the average molecular weight. Using this method, 53% of hemoglobin obtained is intermolecular cross-linked with 12 molecular equivalents of glutaraldehyde. The majority of poly-hemoglobins is in the range of 128 kD to 258 kD.

Key parameters affecting the initial leaky effect of hemoglobin-loaded nanoparticles as blood substitutes

In order to realize long-term carrying/delivering oxygen and minimize the adverse effects of free hemoglobin (Hb) in vivo, Hb is desired to be confined in Hb-loaded nanoparticles (HbP), a novel blood substitute with potential clinical applications, and thus functions as the native red blood cells (RBCs). However, the initial burst release of Hb ("leaky effect") greatly underscores the significance of this work. The study described here wants to disclose the key preparative parameters, including polymer, excipients in the inner aqueous phase and solvent profile, affecting the Hb release behavior (the initial 24 h) from HbP fabricated by commonly used solvent diffusion/evaporation double emulsion technique. The results demonstrate that PEGlytated polymers, regardless of two- or tri-block copolymers show slower release compared with the corresponding non-PEGlytated ones. The higher polymer concentration yields lower initial release. PEG200, added as excipient facilitates Hb burst effect to about 38.4%, almost 17% increase compared to the control ( approximately 21%), whereas, PVA and Poloxamer188, due to amphiphilic nature, can effectively attenuate this leakage to about 13.0 and 5.1%, respectively. The diffusion/extraction rate from oil phase and the subsequent evaporation rate from the aqueous continuous phase of solvents impose different influences on Hb release. To reduce the burst effect, the initial diffusion/extraction rate should be slow, whereas, the concomitant evaporation rate should be as fast as possible. The results obtained here will be guidance's for the future tailored design of more desirable polymersome nanoparticle blood substitutes.

Numerical Study on Flows of Red Blood Cells With Liposome-Encapsulated Hemoglobin at Microvascular Bifurcation

Flow analysis at microvascular bifurcation after partial replacement of red blood cell (RBC) with liposome-encapsulated hemoglobin (LEH) was performed using the lattice Boltzmann method. A two-dimensional symmetric Y bifurcation model with a parent vessel diameter of 20μm and daughter branch diameters of 20μm was considered, and the distributions of the RBC, LEH, and oxygen fluxes were calculated. When only RBCs flow into the daughter branches with unevenly distributed flows, plasma separation occurred and the RBC flow to the lower-flow branch was disproportionately decreased. On the other hand, when half of RBC are replaced by LEH, the biasing of RBC flow was enhanced whereas LEH flowed favorably into the lower-flow branch, because many LEH within the parent vessel are suspended in the plasma layer, where no RBCs exist. Consequently, the branched oxygen fluxes became nearly proportional to flows. These results indicate that LEH facilitates oxygen supply to branches that are inaccessible to RBCs.

Stroma-free hemoglobin from bovine blood

Isolation and purification of bovine hemoglobin (HbBv) was carried out after reaction of whole blood with carbon monoxide. Washing/centrifugation steps were used to eliminate leukocytes, platelets, and plasma proteins. Hypotonic media and ultrasound radiation were used to lyse red blood cells. Lyse by ultrasound was shown to lead to solutions at the highest concentrations in HbBv, and the least concentrations in major phospholipids contaminants. Additional purification procedures were performed to remove membrane proteins and phospholipids. In the first case, proteins were denatured by thermal treatment, and filtered. To eliminate phospholipids, liquid chromatography was used with strong anion exchangers. Purity of HbBv was evaluated by normal phase high performance liquid chromatography (HPLC), electrophoresis, and size-exclusion HPLC.

Pharmacological and physicochemical factors in the pressor effects of conjugated haemoglobin-based oxygen carriers in vivo

BACKGROUND

The hypertension induced by haemoglobin-based oxygen carriers could be a result of different pharmacological and physicochemical factors.

OBJECTIVE

To investigate whether production of superoxide anion (O2*-) and release of endothelin could be the factors responsible.

METHODS

We studied the variation in mean arterial pressure (MAP) in guinea pigs by carrying out a 50% isovolaemic exchange transfusion with conjugated oxyhaemoglobin (non-oxidized form) or conjugated methaemoglobin (fully oxidized form) in the presence or absence of BQ-788 (5 nmol/l), an endothelin receptor type B (ETR-B) antagonist. At key timepoints of variation in MAP, the plasma concentrations of O2*- were measured. The presence of conjugated oxyhaemoglobin and increases in ETR-B concentrations inside the vascular wall were investigated in different vessels, using western blotting.

RESULTS

We found that the administration of conjugated oxyhaemoglobin induced a significant increase in MAP, whereas conjugated methaemoglobin had no significant haemodynamic effect. Pretreatment with BQ-788 attenuated the increase in MAP induced by conjugated oxyhaemoglobin. This haemoglobin induced the production of high concentrations of O2*- that declined towards control values after 120 min and decreased in the presence of BQ-788. Western blot analysis showed that the presence of conjugated oxyhaemoglobin inside the vascular wall was time-dependent and correlated with increased ETR-B.

CONCLUSION

These results show that the release of O2*- during auto-oxidation of conjugated oxyhaemoglobin is associated with the observed increase in MAP, which may be a result of the vasoconstriction caused by an increase in activation of ETR-B. This activation may be caused by the massive release of endothelin induced by the production of O2*-.

Polypeptide multilayer nanofilm artificial red blood cells

Reliable encapsulation of hemoglobin (Hb) within polypeptide multilayer nanofilms has been achieved by a template-based approach, and protein functionality has been demonstrated postencapsulation. The method is general in scope and could be useful for many other encapsulants. Met-Hb was adsorbed onto 5 microm-diameter CaCO3 microparticles, and the Hb-coated particles were encapsulated within a multilayer nanofilm of poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) by layer-by-layer assembly. The CaCO3 templates were then dissolved within the PLGA/PLL nanofilms by addition of ethylenediaminetetraacetic acid. Encapsulation of Hb was proved by fluorescence microscopy, the pH-dependence of retention of Hb was determined by visible wavelength absorbance, and conversion of the encapsulated met-Hb to deoxy-Hb and oxy-Hb was demonstrated by spectroscopic analysis of the Soret absorption peak under various conditions. It thus has been shown that control of Hb oxygenation within polypeptide multilayer nanofilm artificial cells is possible, and that Hb thus encapsulated can bind, release, and subsequently rebind molecular oxygen. This work therefore represents an advance in the development of polypeptide multilayer film artificial red blood cells.

Effects of isovolemic resuscitation with hemoglobin-based oxygen carrier Hemoglobin glutamer-200 (bovine) on systemic and mesenteric perfusion and oxygenation in a canine model of hemorrhagic shock: a comparison with 6% hetastarch solution and shed blood

OBJECTIVE

To study Hemoglobin glutamer-200 bovine (Hb-200), 6% hetastarch (HES) and shed whole blood (WB) resuscitation in canine hemorrhagic shock.

STUDY DESIGN

Prospective laboratory investigation. Animals Twelve adult dogs [29 +/- 1 kg (mean +/- SD)].

METHODS

Anesthetized dogs were instrumented for recording systemic and mesenteric hemodynamic parameters and withdrawal of arterial, mixed and mesenteric venous blood, in which hematological, oxygenation, blood gas and acid-bases variables were determined. Recordings were made before [baseline (BL)], after 1 hour of hypovolemia and immediately and 3 hours post-resuscitation with 30 mL kg(-1) of either Hb-200, HES, or WB.

RESULTS

Blood withdrawal (average 34 +/- 2 mL kg(-1)) caused significant hemodynamic changes, metabolic acidosis and hyperlactatemia characteristic for hemorrhagic shock. Only WB transfusion restored all variables. Hemoglobin glutamer-200 bovine infusion returned most hemodynamic parameters including cardiac output and mesenteric arterial blood flow to BL but increased mean arterial pressure above BL (p < 0.05). However, Hb-200 failed to restore total Hb and arterial oxygen content (CaO2), leaving systemic (DO2I) and mesenteric O2 delivery (DO2Im) below BL (p < 0.05). Nevertheless, acid-base variables recovered completely after Hb-200 resuscitation, and met-hemoglobin (Met-Hb) levels increased (p < 0.05). Hetastarch resuscitation returned hemodynamic variables to or above BL but further decreased total Hb and CaO2, preventing recovery of sDO2I and mDO2I (p < 0.05). Thus, systemic and mesenteric O2 extraction stayed above BL (p < 0.05) while acid-base variables recovered to BL, although slower than in Hb-200 and WB groups (p < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Resuscitation with Hb-200 seemed to resolve metabolic acidosis and lactatemia more rapidly than HES, but not WB; yet it is not superior to HES in improving DO2I and DO2Im. The hyperoncotic property of solutions like Hb-200 that results in rapid volume expansion with more homogenous microvascular perfusion and the ability to facilitate diffusive O2 transfer accelerating metabolic recovery may be the key mechanisms underlying their beneficial effects as resuscitants.

Blood substitutes based on nanobiotechnology

Stimulated by concerns of potential infective agents in donated blood, commercial enterprises have attempted to develop blood substitutes since the 1900s. After several years of development, a few of the many leads are showing promise. In this article, nanobiotechnological approaches that are now in phase III clinical trials are reviewed, followed by a discussion of how important basic knowledge gained is being used to develop new generations of blood substitutes based on nanobiotechnology.

Polyhemoglobin with different percentage of tetrameric hemoglobin and effects on vasoactivity and electrocardiogram

There has been considerable discussions on why some types of haemoglobin-based blood substitutes increase vasoactivity whereas a very few others do not. In this study, we prepare four different types of PolyHb each containing different percentage of tetrameric hemoglobin using glutaraldehyde crosslinking and characterized to ensure that they all have the same oxygen affinity. Thus the preparations are prepared from the same chemical method and have the same oxygen affinity. We infused these in the form of 1/6 volume toploading into anesthetized rats to simulate the use of blood substitutes in surgery. Mean arterial pressure (MAP) increased immediately after injection of PolyHb containing 38% or 78% of tetrameric hemoglobin. However, there was no significant increase in blood pressure with the injection of PolyHb containing 16% or 0.4% tetrameric hemoglobin. In electrocardiogram (ECG) study, we observe that high percentage (78%) of tetrameric hemoglobin causes marked changes in ECG immediately after infusion. Injection of PolyHb containing 16% or 38% of tetrameric hemoglobin resulted in minimal elevation of the ST segment. Infusion of PolyHb containing 0.4% of tetrameric hemoglobin did not result in any changes.

FLUID RESUSCITATION WITH HEMOGLOBIN VESICLES IN A RABBIT MODEL OF ACUTE HEMORRHAGIC SHOCK

Several hemoglobin (Hb)-based oxygen carriers are available for use in clinical situations, but their use risks inducing cardiovascular dysfunction as a result of Hb interacting with nitric oxide. Hb vesicles (HbV) are liposome-encapsulated purified human Hb with polyethylene glycol chains at the surface. This study evaluated the effects of HbV on hemodynamics, tissue and systemic oxygenation, and osmotic pressure after fluid resuscitation in an acute hemorrhagic shock model. Hemorrhagic shock was induced in 24 anesthetized mechanically ventilated male rabbits by withdrawing blood to a mean arterial blood pressure (MAP) of 30 to 35 mmHg over 15 min and maintaining this state for 30 min. The animals were resuscitated by replacing the blood with equal volumes of HbV in recombinant human albumin solution (HbV/rHSA), rHSA alone, or Ringer lactated solution (RL), or with three times the withdrawn volume of RL and observed for 2 h. Fluid resuscitation restored MAP, central venous pressure, and cardiac index values, but these fell again within 2 h in rabbits treated with RL. Fluid resuscitation using HbV/rHSA immediately increased MAP and cardiac index but not systemic vascular resistance, maintained a high level of oxygen consumption, and reduced the blood glucose level, which increased after hemorrhage. Fluid resuscitation using HbV/rHSA did not disturb microoxygenation in the brain, kidneys, liver, or muscle; allowed an immediate recovery of tissue oxygenation without decreasing cardiac output or increasing systemic vascular resistance, and increased the oxygen consumption. HbV solution offers the advantages of systemic oxygenation without impairing microcirculation in the treatment of hemorrhagic shock.

A Biophysical Investigation of Recombinant Hemoglobins with Aromatic B10 Mutations in the Distal Heme Pockets,

This study examines the structural and functional effects of amino acid substitutions in the distal side of both the alpha- and beta-chain heme pockets of human normal adult hemoglobin (Hb A). Using our Escherichia coli expression system, we have constructed four recombinant hemoglobins: rHb(alphaL29F), rHb(alphaL29W), rHb(betaL28F), and rHb(betaL28W). The alpha29 and beta28 residues are located in the B10 helix of the alpha- and beta-chains of Hb A, respectively. The B10 helix is significant because of its proximity to the ligand-binding site. Previous work showed the ability of the L29F mutation to inhibit oxidation. rHb(alphaL29W), rHb(betaL28F), and rHb(betaL28W) exhibit very low oxygen affinity and reduced cooperativity compared to those of Hb A, while the previously studied rHb(alphaL29F) exhibits high oxygen affinity. Proton nuclear magnetic resonance spectroscopy indicates that these mutations in the B10 helix do not significantly perturb the alpha(1)beta(1) and alpha(1)beta(2) subunit interfaces, while as expected, the tertiary structures near the heme pockets are affected. Experiments in which visible spectrophotometry was utilized reveal that rHb(alphaL29F) has equivalent or slower rates of autoxidation and azide-induced oxidation than does Hb A, while rHb(alphaL29W), rHb(betaL28F), and rHb(betaL28W) have increased rates. Bimolecular rate constants for NO-induced oxidation have been determined using a stopped-flow apparatus. These findings indicate that amino acid residues in the B10 helix of the alpha- and beta-chains can play different roles in regulating the functional properties and stability of the hemoglobin molecule. These results may provide new insights for designing a new generation of hemoglobin-based oxygen carriers.

Therapeutic applications of polymeric artificial cells

Polymeric artificial cells have the potential to be used for a wide variety of therapeutic applications, such as the encapsulation of transplanted islet cells to treat diabetic patients. Recent advances in biotechnology, molecular biology, nanotechnology and polymer chemistry are now opening up further exciting possibilities in this field. However, it is also recognized that there are several key obstacles to overcome in bringing such approaches into routine clinical use. This review describes the historical development and principles behind polymeric artificial cells, the present state of the art in their therapeutic application, and the promises and challenges for the future.

Regional myocardial perfusion under exchange transfusion with liposomal hemoglobin: in vivo and in vitro studies using rat hearts

The purpose of this study was to test the hypothesis that exchange transfusion with liposomal hemoglobin (LH) reduces the microheterogeneity of regional myocardial flows while sustaining cardiac function. Neo Red Cell mixed with albumin was used as the LH solution, in which the LH volume fraction was 17∼18% and hemoglobin density was nearly two-thirds smaller than in rat blood. Regional myocardial flows in left ventricular free walls were measured by tracer digitalradiography (100-μm resolution) in anesthetized rats with or without 50% blood-LH exchange transfusion. Within-layer flow distributions showed lower heterogeneity with ( n = 8) than without ( n = 8) LH transfusion. No extravasation of hemoglobin was confirmed by 3,3-diaminobenzidin staining ( n = 2). Carotid flow increased by 68% due to LH transfusion, whereas arterial pressure and heart rate remained unchanged. On the other hand, cross-circulated rat hearts ( n = 7) were used to evaluate the effects of 50% blood-LH exchange on coronary flow and tone preservation under 300-beats/min pacing and 100-mmHg perfusion pressure. Blood-LH exchange caused a 71% increase of coronary flow and 10% decrease of percent flow increase during hyperemia after 30-s flow interruption. Myocardial O2 supply and consumption increased by 9% and 10%, respectively, whereas myocardial O2 extraction remained unchanged. The large increases of in vivo carotid flow and coronary flow in cross-circulated hearts due to LH coperfusion could be explained by the reduction of apparent flow viscosity. These results suggest that under LH coperfusion, the microheterogeneity of myocardial flows decreases with increased coronary flow while fairly preserving coronary tone and cardiac function.

Evidence that rehydrated, lyophilized red blood cells are sufficiently deformable for normal microcirculation transit

A method was developed for the preparation of rehydratable lyophilized red blood cells (RL RBCs) that hold promise as cell-based oxygen carriers for transfusion medicine. The maintenance of normal cellular deformability is essential for the successful development of cell-based oxygen delivery systems. Improper deformability of RBCs can lead to hemolysis if too fragile or microvascular occlusion if too rigid. We developed an aldehyde stabilization method that is based on the use of paraformaldehyde polymers that complement the function of spectrin as a structural unit with conformational flexibility. Three types of in vitro deformability studies (filter transit, pipette aspiration, and atomic force microscopy) and in vivo intravital microscopy were performed to characterize the deformability of RL RBCs. When considered with safety data from previously reported studies in dogs, the results of these studies indicate that paraformaldehyde-modified RL RBCs have visco-elastic deformability properties that are in the nonpathological range.

In vitro and in vivo effects of polyhaemoglobin-tyrosinase on murine B16F10 melanoma

Melanoma is an increasingly common fatal skin cancer. Many groups are carrying out research on potential treatments for melanoma. One of these approaches has shown that lowering tyrosine can inhibit the growth of melanoma in cell cultures and of B16BL6 melanoma in mice. However, humans cannot tolerate tyrosine-restricted diets for lowering tyrosine because of nausea, vomiting and weight loss. We report here our preparation and characterization of a novel soluble polyhaemoglobin-tyrosinase complex. This preparation prevents native tyrosinase from having adverse effects and from rapid removal after injection. The preparation inhibited murine B16F10 melanoma cell growth in culture and delayed its growth in a mice model. Intravenous injection of the preparation lowers the systemic tyrosine level without causing adverse effects such as vomiting and weight loss in mice. It is therefore possible that this complex could be useful in the treatment of human melanoma.

Kinetics of liposome-encapsulated hemoglobin after 25% hypovolemic exchange transfusion

Liposome-encapsulated hemoglobin (LEH) is being developed as an oxygen therapeutic. In this work, we evaluated a neutral formulation of PEGylated LEH for its circulation and distribution properties in rodent models of 25% hypovolemic exchange transfusion. About 25% of blood in rats and rabbits was exchanged with LEH that had been previously labeled with 99mTc radionuclide. The distribution of 99mTc-LEH was followed by gamma camera imaging and intermittent blood sampling during 48 h, and counting the tissue-associated radioactivity after necropsy at 48 h. On the basis of circulation kinetics, the half-life of 99mTc-LEH in blood was 30 and 39.8 h in rats and rabbits, respectively. Apart from blood, major organs of accumulation of LEH after 48 h included liver (rats, 10.3% and rabbits, 5.4% of injected dose) and spleen (rats, 2.4% and rabbits, 0.8% of injected dose). The results demonstrate that LEH circulates for a prolonged time after administration and that the animals tolerate at least 25% of blood exchange without any distress. Subsequent to the enhanced uptake in the RES, the rats clear LEH from the circulation faster than the rabbits.

Allogenic Blood Transfusion in the First 24 Hours after Trauma Is Associated with Increased Systemic Inflammatory Response Syndrome (SIRS) and Death

BACKGROUND

Previous studies have documented that blood transfusion incites a substantial inflammatory response with the systemic release of cytokines. Furthermore, blood transfusion is a significant independent predictor of multiple organ failure in trauma. The objective of this study was to assess the risk of systemic inflammatory response syndrome (SIRS) and intensive care unit (ICU) admission, length of stay (LOS), and mortality in trauma patients who require blood transfusion.

METHODS

Prospective data were collected on 9,539 trauma patients admitted to the R. Adams Cowley Shock Trauma Center over a 30-month period from January, 1997 to July, 1999. Complete SIRS data were available on 7,602 patients. Patients were stratified by age, gender, race, Glasgow coma scale (GCS), and injury severity score (ISS). A systemic inflammatory response to a wide variety of severe clinical insults (SIRS) was defined as a SIRS score of > or =2, as calculated on admission. Blood transfusion was assessed as an independent predictor of SIRS, ICU admission and length of stay, and mortality.

RESULTS

The mean age of the study cohort was 37 +/- 17 years; the mean ISS was 9 +/- 9 points. Seventy-one percent of the patients were male, and 85% sustained blunt trauma. Blood transfusion within the first 24 h was administered to 954 patients, comprising 10% of the study cohort. Transfused patients were significantly older (43 +/- 20 vs. 36 +/- 16 years, p < 0.00001), had higher ISS (22 +/- 12 vs. 8 +/- 7 points, p < 0.00001), and lower GCS (12 +/- 4 vs. 14 +/- 2 points, p < 0.00001) than non-transfused patients. Blood transfusion and increased total volume of blood transfusion was associated with SIRS. Blood transfusion was also a significant independent predictor of SIRS, ICU admission, and mortality in trauma patients by multinomial logistic regression analysis. Trauma patients who received blood transfusion had a two- to nearly sixfold increase in SIRS (p < 0.0001) and more than a fourfold increase in ICU admission (OR 4.62, 95% CI 3.84-5.55, p < 0.0001) and mortality (OR 4.23, 95% CI 3.07-5.84, p < 0.0001) compared to those that were not transfused. Linear regression analysis revealed that transfusion was an independent predictor of ICU LOS (Coef. 5.20, SE 0.43, p < 0.0001). Transfused patients had significantly longer ICU LOS (16.8 +/- 14.9 vs. 9.9 +/- 10.6 days, p < 0.00001) and hospital LOS (14.5 +/- 15.5 vs. 2.5 +/- 5.3 days, p < 0.00001) compared to non-transfused patients.

CONCLUSIONS

Blood transfusion within the first 24 h was an independent predictor of mortality, SIRS, ICU admission, and ICU LOS in trauma patients. The use of blood substitutes and alternative agents to increase serum hemoglobin concentration in the post-injury period warrants further investigation.