Blood substitutes based on nanobiotechnology

Steps Toward Recapitulating Endothelium: A Perspective on the Next Generation of Hemocompatible Coatings

Endothelium, the lining in this blood vessel, orchestrates three main critical functions such as protecting blood components, modulating of hemostasis by secreting various inhibitors, and directing clot digestion (fibrinolysis) by activating tissue plasminogen activator. No other surface can perform these tasks; thus, the contact of blood and blood-contacting medical devices inevitably leads to the activation of coagulation, often causing device failure, and thromboembolic complications. This perspective, first, discusses the biological mechanisms of activation of coagulation and highlights the efforts of advanced coatings to recapitulate one characteristic of endothelium, hereafter single functions of endothelium and noting necessity of the synergistic integration of its three main functions. Subsequently, it is emphasized that to overcome the challenges of blood compatibility an endothelium-mimicking system is needed, proposing a synergy of bottom-up synthetic biology, particularly synthetic cells, with passive- and bioactive surface coatings. Such integration holds promise for developing advanced biomaterials capable of recapitulating endothelial functions, thereby enhancing the hemocompatibility and performance of blood-contacting medical devices.

Stability of Liposomal Membrane of Hemoglobin-Vesicles (Artificial Red Cells) for Over Years of Storage Evaluated Using Liquid Chromatography-Mass Spectrometry

Hemoglobin-Vesicles (Hb-V) are artificial oxygen carriers encapsulating a purified and concentrated Hb solution in liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), cholesterol, 1,5-O-dihexadecyl-N-succinyl-l-glutamate (DHSG), and 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-poly(ethylene glycol) (PEG5000) (DSPE-PEG). The safety and efficacy of Hb-V have been studied extensively by both preclinical and clinical test methods. Deoxygenation of Hb-V prevents autoxidation of Hb and can extend its shelf life to 2 years at room temperature. However, the lipid components raise concerns about hydrolysis because Hb-V is dispersed in saline. For this study, we attempted to estimate the lipid degradation of long-term stored Hb-V using liquid chromatography-mass spectrometry. Analyses of lipid components extracted from the stored Hb-V showed that the degradation increased depending on the storage temperature. The calculated % remaining of intact lipids of Hb-V were 98.1% after 4 years and 90.4% after 7.2 years at 4 °C, 95.8% after 1 year and 86.7% after 2 years at 25 °C, and 85.6% after 6 months at 40 °C. The main degradation products were lyso-PC and palmitic acid which are hydrolyzed at the ester bond of DPPC. A few hydrolyzed products of DHSG and DSPE-PEG were also detected in Hb-V, but almost no degradation or oxidation products derived from cholesterol could be identified. A shear test of Hb-V at 1500 s-1 showed no significant increase in Hb leakage after storage of 2 years at 25 °C and 6 months at 40 °C. Lipid degradation products including free fatty acids would decrease the pH of the Hb-V dispersion and synergistically facilitate degradation, but it maintained pH 6.5 during 6 years at 4 °C, 2 years at 25 °C, and 3 months at 40 °C because of its high buffering capacity. These results indicate that the storage conditions for Hb-V are appropriate to minimize lipid degradation in the long term.

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.

Biomaterials for human space exploration: A review of their untapped potential

As biomaterial advances make headway into lightweight radiation protection, wound healing dressings, and microbe resistant surfaces, a relevance to human space exploration manifests itself. To address the needs of the human in space, a knowledge of the space environment becomes necessary. Both an understanding of the environment itself and an understanding of the physiological adaptations to that environment must inform design parameters. The space environment permits the fabrication of novel biomaterials that cannot be produced on Earth, but benefit Earth. Similarly, designing a biomaterial to address a space-based challenge may lead to novel biomaterials that will ultimately benefit Earth. This review describes several persistent challenges to human space exploration, a variety of biomaterials that might mitigate those challenges, and considers a special category of space biomaterial. STATEMENT OF SIGNIFICANCE: This work is a review of the major human and environmental challenges facing human spaceflight, and where biomaterials may mitigate some of those challenges. The work is significant because a broad range of biomaterials are applicable to the human space program, but the overlap is not widely known amongst biomaterials researchers who are unfamiliar with the challenges to human spaceflight. Additionaly, there are adaptations to microgravity that mimic the pathology of certain disease states ("terrestrial analogs") where treatments that help the overwhelmingly healthy astronauts can be applied to help those with the desease. Advances in space technology have furthered the technology in that field on Earth. By outlining ways that biomaterials can promote human space exploration, space-driven advances in biomaterials will further biomaterials technology.

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.

Synthesis and characterisation of aqueous haemoglobin-based microcapsules coated by genipin-cross-linked albumin

Bovine serum albumin (BSA)-coated haemoglobin (Hb)-microcapsules prepared by co-precipitation of Hb and MnCO₃ may present an alternative type of artificial blood substitute. Prepared microcapsules were analysed by Scanning electron microscopy (SEM) and Respirometry, cytotoxicity was evaluated by addition of microcapsules to murine fibroblast-derived cell line L929 (American Type Culture Collection, NCTC clone 929 of strain L). The capsules come along with a mean diameter of approximately 0.6 μm and a mean volume of 1.13 × 10^-19 L, thus an average human red blood cell with a volume of 9 × 10^-14 L is about 800,000 times bigger. Hb-microcapsules are fully regenerable by ascorbic acid and maintain oxygen affinity because oxygen is able to pass the BSA wall of the capsules and thereby binding to the ferrous iron of the haemoglobin entity. Therefore, these microcapsules present a suitable type of potential artificial haemoglobin-based oxygen carrier (HbOC).

Recent and prominent examples of nano- and microarchitectures as hemoglobin-based oxygen carriers

Blood transfusions, which usually consist in the administration of isolated red blood cells (RBCs), are crucial in traumatic injuries, pre-surgical conditions and anemias. Although RBCs transfusion from donors is a safe procedure, donor RBCs can only be stored for a maximum of 42 days under refrigerated conditions and, therefore, stockpiles of RBCs for use in acute disasters do not exist. With a worldwide shortage of donor blood that is expected to increase over time, the creation of oxygen-carriers with long storage life and compatibility without typing and cross-matching, persists as one of the foremost important challenges in biomedicine. However, research has so far failed to produce FDA approved RBCs substitutes (RBCSs) for human usage. As such, due to unacceptable toxicities, the first generation of oxygen-carriers has been withdrawn from the market. Being hemoglobin (Hb) the main component of RBCs, a lot of effort is being devoted in assembling semi-synthetic RBCS utilizing Hb as the oxygen-carrier component, the so-called Hb-based oxygen carriers (HBOCs). However, a native RBC also contains a multi-enzyme system to prevent the conversion of Hb into non-functional methemoglobin (metHb). Thus, the challenge for the fabrication of next-generation HBOCs relies in creating a system that takes advantage of the excellent oxygen-carrying capabilities of Hb, while preserving the redox environment of native RBCs that prevents or reverts the conversion of Hb into metHb. In this review, we feature the most recent advances in the assembly of the new generation of HBOCs with emphasis in two main approaches: the chemical modification of Hb either by cross-linking strategies or by conjugation to other polymers, and the Hb encapsulation strategies, usually in the form of lipidic or polymeric capsules. The applications of the aforementioned HBOCs as blood substitutes or for oxygen-delivery in tissue engineering are highlighted, followed by a discussion of successes, challenges and future trends in this field.

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.

Synthesis of a hemoglobin-conjugated triblock copolymer for oxygen carrying and specific recognition of cancer cells

Considering that hypoxia causes resistance to anti-cancer therapeutics, we synthesized a hemoglobin-based nanocarrier for oxygen carrying and recognition of cancer cells.

Artificial Blood Substitutes: First Steps on the Long Route to Clinical Utility

The 21st century is challenging for human beings. Increased population growth, population aging, generation of new infectious agents, and natural disasters are some threatening factors for the current state of blood transfusion. However, it seems that science and technology not only could overcome these challenges but also would turn many human dreams to reality in this regard. Scientists believe that one of the future evolutionary innovations could be artificial blood substitutes that might pave the way to a new era in transfusion medicine. In this review, recent status and progresses in artificial blood substitutes, focusing on red blood cells substitutes, are summarized. In addition, steps taken toward the development of artificial blood technology and some of their promises and hurdles will be highlighted. However, it must be noted that artificial blood is still at the preliminary stages of development, and to fulfill this dream, ie, to routinely transfuse artificial blood into human vessels, we still have to strengthen our knowledge and be patient.

Polymerization of modified diaspirin cross-linked hemoglobin (DCLHb) with 1,6-bismaleimic-hexane

Increasing the size of hemoglobin (Hb) by polymerization offers the benefits of reduced renal clearance and increased duration in the vascular circulation. With this goal, diaspirin cross-linked hemoglobin (DCLHb) was modified in order to keep one thiol group on the surface and then polymerized with 1,6-bismaleimic-hexane (1,6-BMH) to increase the molecular weight. The HPLC results indicated that approximate 20% dimers to tetramers of DCLHb desired were achieved after the polymerization. It was also demonstrated that the oxygen-carrying capacity of the products was similar to natural heme. The present study is expected to improve the efficacy of the DCLHb as an oxygen therapeutic agent.

Preparation and characterization of PEG-modified PCL nanoparticles for oxygen carrier: a new application of Fourier transform infrared spectroscopy for quantitative analysis of the hemoglobin in nanoparticles

The influence of polyethylene glycol (PEG) molar ratio on the nanoparticles (NPs) properties is described herein. Especially, a facile and nondestructive determination route has been raised to quantify the hemoglobin (Hb) amounts in NPs via an internal standard FTIR method. The subsequent results indicated that, briefly, the PEG molar ratio did negligible influence on the size distribution of NPs, however, it did have great effect on the NPs zeta potential and hydrophilicity as well as the Hb loading amount. These findings highlight that the PEG density on the surface is a key parameter affecting the NPs properties.

Nonvasoconstrictive hemoglobin particles as oxygen carriers

Artificial oxygen carriers, favorably hemoglobin-based oxygen carriers (HBOCs), are being investigated intensively during the last 30 years with the aim to develop a universal blood substitute. However, serious side effects mainly caused by vasoconstriction triggered by nitric oxide (NO) scavenging due to penetration of nanosized HBOCs through the endothelial gaps of the capillary walls and/or oxygen oversupply in the precapillary arterioles due to their low oxygen affinity led to failure of clinical trials and FDA disapproval. To avoid these effects, HBOCs with a size between 100 and 1000 nm and high oxygen affinity are needed. Here we present for the first time unique hemoglobin particles (HbPs) of around 700 nm with high oxygen affinity and low immunogenicity using a novel, highly effective, and simple technique. The fabrication procedure provides particles with a narrow size distribution and nearly uniform morphology. The content of hemoglobin (Hb) in the particles corresponded to 80% of the Hb content in native erythrocytes. Furthermore, we demonstrate a successful perfusion of isolated mouse glomeruli with concentrated HbP suspensions in vitro. A normal, nonvasoconstrictive behavior of the afferent arterioles is observed, suggesting no oxygen oversupply and limited NO scavenging by these particles, making them a highly promising blood substitute.

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.

Low modulus biomimetic microgel particles with high loading of hemoglobin

We synthesized extremely deformable red blood cell-like microgel particles and loaded them with bovine hemoglobin (Hb) to potentiate oxygen transport. With similar shape and size as red blood cells (RBCs), the particles were fabricated using the PRINT (particle replication in nonwetting templates) technique. Low cross-linking of the hydrogel resulted in very low mesh density for these particles, allowing passive diffusion of hemoglobin throughout the particles. Hb was secured in the particles through covalent conjugation of the lysine groups of Hb to carboxyl groups in the particles via EDC/NHS coupling. Confocal microscopy of particles bound to fluorescent dye-labeled Hb confirmed the uniform distribution of Hb throughout the particle interior, as opposed to the surface conjugation only. High loading ratios, up to 5 times the amount of Hb to polymer by weight, were obtained without a significant effect on particle stability and shape, though particle diameter decreased slightly with Hb conjugation. Analysis of the protein by circular dichroism (CD) spectroscopy showed that the secondary structure of Hb was unperturbed by conjugation to the particles. Methemoglobin in the particles could be maintained at a low level and the loaded Hb could still bind oxygen, as studied by UV-vis spectroscopy. Hb-loaded particles with moderate loading ratios demonstrated excellent deformability in microfluidic devices, easily deforming to pass through restricted pores half as wide as the diameter of the particles. The suspension of concentrated particles with a Hb concentration of 5.2 g/dL showed comparable viscosity to that of mouse blood, and the particles remained intact even after being sheared at a constant high rate (1000 1/s) for 10 min. Armed with the ability to control size, shape, deformability, and loading of Hb into RBC mimics, we will discuss the implications for artificial blood.

Cationic amylose-encapsulated bovine hemoglobin as a nanosized oxygen carrier

Nanosized hemoglobin-based oxygen carriers are one of the most promising blood substitutes. In the present study, a comprehensive strategy for the preparation of nanosized cationic amylose-encapsulated hemoglobins (NCAHbs) was developed. First, cationic amylase (CA) was synthesized from amylose and quaternary ammonium salt by an etherification reaction. The structure of CA was characterized using Fourier transform infrared spectrophotometry (FTIR) and proton nuclear magnetic resonance spectrophotometry ((1)H NMR). The degree of substitution and the zeta potential were also measured. Then, the NCAHbs were prepared by electrostatic adhesion, reverse micelles and cross-linking. The UV-visible spectrophotometer was used to measure the entrapment efficiency (EE%) and drug loading efficiency (DL%) of the NCAHbs. Transmission electron microscopy and Malvern Nano-zs 90 analyzer were used to observe the size distribution and morphology of particles. Chemical structure was determined from the FTIR spectrum. A Hemox analyzer was used to measure the P(50) and Hill coefficients. A lethal hemorrhagic shock model in rats was used to evaluate the therapeutic effect of the NCAHbs. The results showed that the combined methods improved the size, stability, EE%, DL%, and oxygen-carrying capacity of the NCAHbs. The average diameter of the NCAHbs was 92.53 ± 3.64 nm, with a narrow polydispersity index of 0.027. The EE% was 80.05% ± 1.56% and DL% was 61.55% ± 1.41%. The P(50) and Hill coefficient were equal to 28.96 ± 1.33 mmHg and 2.55 ± 0.22, respectively. The size of NCAHbs remained below 200 nm for six days in PBS solution. The NCAHbs could effectively prevent lung injury from progressing to lethal hemorrhagic shock because they acted as both a volume expander and an oxygen carrier.

Development of a method to produce hemoglobin in a bioreactor culture of Escherichia coli BL21(DE3) transformed with a plasmid containing Plesiomonas shigelloides heme transport genes and modified human hemoglobin genes

We describe a method for production of recombinant human hemoglobin by Escherichia coli grown in a bioreactor. E. coli BL21(DE3) transformed with a plasmid containing hemoglobin genes and Plesiomonas shigelloides heme transport genes reached a cell dry weight of 83.64 g/liter and produced 11.92 g/liter of hemoglobin in clarified lysates.

The immunological properties of stroma-free polyhemolysate containing catalase and superoxide dismutase activities prepared by polymerized bovine stroma-free hemolysate

Crosslinking of ultrapure hemoglobin, crystalline catalase, and superoxide dismutase resulted in a soluble nanodimensional complex of polyhemoglobin-catalase-superoxide dismutase. A less expensive and more convenient way is to crosslink bovine stroma-free hemolysate (stroma-free hemolysate) that already contains hemoglobin, catalase, and superoxide dismutase into polyhemoglobin with catalase and superoxide dismutase activities (stroma-free polyhemolysate) [21]. The objective of the present study is to evaluate the immunological properties of this stroma-free polyhemolysate. Each of three groups of rats received weekly subcutaneous injections of one of the stroma-free polyhemolysate, stroma-free hemolysate, and saline for four weeks. One week after the four cycles of weekly immunization, serum and plasma were collected for C3a complement activation tests and Ouchterlony antibody-antigen precipitation tests, respectively. Results show that stroma-free polyhemolysate retained significant antioxidant enzyme activity. The C3a complement activation test and Ouchterlony test show that four weekly subcutaneous injections of bovine stroma-free polyhemolysate did not result in any immunological reaction in rats when tested this way.

Quantitative analysis of hemoglobin content in polymeric nanoparticles as blood substitutes using Fourier transform infrared spectroscopy

Based on the penetrability of IR within the polymeric nanoparticles, a novel Fourier transform infrared spectroscopy (FTIR) method, with polyacrylonitrile (PAN) as the internal reference standard, was developed to quantify the hemoglobin (Hb) content in Hb-based polymeric nanoparticles (HbPN). The HbPN was fabricated by double emulsion method from poly(ethylene glycol)-poly(lactic acid)-poly(ethylene glycol) triblock copolymers. Depending on the characteristic un-overlapped IR absorbances at 1540 cm(-1) of Hb (amide II) and at 2241 cm(-1) of PAN(-C[triple bond]N), calibration equations, presenting the peak height ratio of Hb and PAN as a function of the weight ratio of Hb and PAN, were established. This new quantification method is validated and used to the determination Hb content in HbPN. Due to the good results of this calibration strategy, the proposed simple FTIR approach with minimal sample-needed and solvent-free makes it useful for routine analysis of protein content and could be also applied to any other drug/protein encapsulated particles.

Oxygen carrier based on hemoglobin/poly(L-lysine)-block-poly(L-phenylalanine) vesicles

An oxygen carrier was prepared by encapsulating carbonylated hemoglobin (CO-Hb) molecules into polypeptide vesicles made from poly(L-lysine)-block-poly(L-phenylalanine) (PLL-b-PPA) diblock copolymers in aqueous medium at pH 5.8. The encapsulation was confirmed by confocal laser scanning microscopy (CLSM). The morphology and size of the vesicles were studied by field-emission scanning electron microscopy (ESEM). They had a spherical shape with a mean diameter of about 4 to 5 microm. The encapsulation efficiency of hemoglobin was 40 wt %, and the hemoglobin content in the vesicles was 32 wt %. The CO-Hb encapsulated in the PLL-b-PPA vesicles was more stable than free CO-Hb under ambient conditions. In the presence of a O(2) atmosphere, the CO-Hb in the vesicle could be converted into oxygen-binding hemoglobin (O(2)-Hb) under irradiation of visible light for 2 h. Therefore, the CO-Hb/PLL-b-PPA vesicles are expected to be used as red blood cell substitutes.

Long-circulation of hemoglobin-loaded polymeric nanoparticles as oxygen carriers with modulated surface charges

The aim of this study was to investigate the effects of the surface charges on the in vitro macrophage cellular uptake and in vivo blood clearance and biodistribution of the hemoglobin-loaded polymeric nanoparticles (HbPNPs). The surface charges of the HbPNPs fabricated from mPEG-PLA-mPEG were modulated with cationized cetyltrimethylammonium bromide (CTAB) and anionized sodium dodecyl sulphate (SDS), respectively. In vitro macrophage cellular uptake and in vivo biodistribution of the coumarin 6-labeled HbPNPs with different electric charges were investigated, and the half-lives in the circulation were pharmacokinetically analyzed. The particle sizes of the HbPNPs were all below 200 nm with a narrow size distribution and high encapsulation efficiency (>84%). And the zeta-potentials of the untreated, cationized and anionized HbPNPs in phosphate buffered sodium chloride solution (PBS) were -12.3, +3.28 and -25.4 mV, respectively. The HbPNPs did not occur significant aggregation or sedimentation, even after 5 days. Compared with the untreated HbPNPs, 1-fold decrease/increase of the uptake percentage associated with the cationized/anionized HbPNPs was observed. In vivo experiment demonstrated that the calculated half-life of the cationized HbPNPs was 10.991 h, 8-fold longer than that of the untreated HbPNPs (1.198 h). But the anionized HbPNPs displayed opposite effect. Furthermore, the cationized HbPNPs mainly accumulated in the liver, lung and spleen after 48 h injection. MTT results showed that the HbPNPs with different surface charges all exhibited slight toxicity. These results demonstrated that the CTAB-modulated HbPNPs with low positive charge and suitable size have a promising potential as a long-circulating oxygen carrier system with desirable biocompatibility and biofunctionality.

Site-selective glycosylation of hemoglobin on Cys beta93

In this work, we describe the synthesis and characterization of a novel glycosylated hemoglobin (Hb) with high oxygen affinity as a potential Hb-based oxygen carrier. Site-selective glycosylation of bovine Hb was achieved by conjugating a lactose derivative to Cys 93 on the beta subunit of Hb. LC-MS analysis indicates that the reaction was quantitative, with no unmodified Hb present in the reaction product. The glycosylation site was identified by chymotrypsin digestion of the glycosylated bovine Hb followed with LC-MS/MS and from the X-ray crystal structure of the glycosylated Hb. The chemical conjugation of the lactose derivative at Cys beta93 yields an oxygen carrier with a high oxygen affinity (P(50) of 4.94 mmHg) and low cooperativity coefficient (n) of 1.20. Asymmetric flow field-flow fractionation (AFFFF) coupled with multiangle static light scattering (MASLS) was used to measure the absolute molecular weight of the glycosylated Hb. AFFFF-MASLS analysis indicates that glycosylation of Hb significantly altered the alpha(2)beta(2)-alphabeta equilibrium compared to native Hb. Subsequent X-ray analysis of the glycosylated Hb crystal showed that the covalently linked lactose derivative is sandwiched between the beta(1) and alpha(2) (and hence by symmetry the beta(2) and alpha(1)) subunits of the tetramer, and the interaction between the saccharide and amino acid residues located at the interface is apparently stabilized by hydrogen bonding interactions. The resultant structural analysis of the glycosylated Hb helps to explain the shift in the alpha(2)beta(2)-alphabeta equilibrium in terms of the hydrogen bonding interactions at the beta(1)alpha(2)/beta(2)alpha(1) interface. Taken together, all of these results indicate that it is feasible to site-specifically glycosylate Hb. This work has great potential in developing an oxygen carrier with defined chemistry that can target oxygen delivery to low pO(2) tissues and organs.

Influence of PEG-conjugated hemoglobin on tumor oxygenation and response to chemotherapy

Hypoxic tumors are significantly more malignant, metastatic, radio- and chemoresistant. The use of artificial oxygen carriers represents a new approach to the problem of hypoxia. In the present study, female athymic BALB/c nude mice bearing the cervical carcinoma were untreated or treated with cisplatin to determine whether administration of artificial oxygen carrier (PEG-conjugated Hemoglobin, PEG-Hb) could improve the tumor oxygenation and enhance the anti-tumor efficacy of cisplatin. Pimonidazole staining was employed to detect tumor tissue oxygenation status. We found that the application of a higher dose (0.6 g/kg) PEG-Hb could significantly ameliorate the hypoxic condition in cervical carcinoma xenograft models. Co-administration of PEG-Hb (0.6 g/kg) with cisplatin produced significant tumor growth inhibition and pro-apoptotic and anti-proliferative effects as compared to cisplatin alone. These suggest the evaluated PEG-Hb in this experiment has positive effects on cisplatin or cisplatin-based chemotherapy, and further work to optimize its application is warranted.

Model analysis of local oxygen delivery with liposome-encapsulated hemoglobin

Liposome-encapsulated hemoglobins (LHs) are comparable to red blood cells (RBCs) in terms of oxygen (O(2))-carrying capacity. The smaller particle size of LHs than of platelets allows their homogeneous dispersion in circulating plasma. In this study, we evaluated the effect of LH transfusion on arterial O(2) delivery through vascular trees by simulation. A mathematical model was established on the basis of the coronary arterial anatomy, the conservation of flow and RBC flux, and Poiseuille's law. The Fåhraeus-Lindqvist, Fåhraeus, and phase separation effects were considered in the model. By assuming steady perfusion, the arterial flow and O(2) delivery were calculated for five model trees undergoing the isovolumic replacement of RBCs (0.3 mg hemoglobin (Hb)/mL) with LHs (0.2 mg Hb/mL) or a plasma volume expander (PVE). The RBC-LH exchange increased both the total flow and the total O(2) flux but had almost no effect on the relative distribution of O(2) flux. In contrast, the RBC-PVE exchange decreased the total O(2) flux and increased the proportion of regions receiving a relatively low O(2) supply. Thus, LH transfusion may compensate for an enhanced bias in RBC-associated O(2) flux under hemodilution and is expected to be beneficial for both total and local O(2) delivery.

Enhancement of recombinant hemoglobin production in Escherichia coli BL21(DE3) containing the Plesiomonas shigelloides heme transport system

To produce recombinant hemoglobin in Escherichia coli, sufficient intracellular heme must be present, or the protein folds improperly and is degraded. In this study, coexpression of human hemoglobin genes and Plesiomonas shigelloides heme transport genes enhanced recombinant hemoglobin production in E. coli BL21(DE3) grown in medium containing heme.

In vitro clinical-grade generation of red blood cells from human umbilical cord blood CD34+ cells

BACKGROUND

There is no appropriate alternative source of red blood cells (RBCs) to relieve the worsening shortage of blood available for transfusion. Therefore, in vitro generation of clinically available RBCs from hematopoietic stem cells could be a promising new source to supplement the blood supply. However, there have been few studies about the generation of clinical-grade RBCs by coculture on human mesenchymal stem cells (MSCs) and various cytokine supplements, even though the production of pure RBCs requires coculture on stromal cells and proper cytokine supplements.

STUDY DESIGN AND METHODS

Umbilical cord blood (CB) CD34+ cells were cultured in serum-free medium supplemented with two cytokine sets of stem cell factor (SCF) plus interleukin-3 (IL-3) plus erythropoietin (EPO) and SCF plus IL-3 plus EPO plus thrombopoietin (TPO) plus Flt-3 for 1 week, followed by coculture upon MSCs derived from bone marrow (BM) or CB for 2 weeks.

RESULTS

Almost pure clinical-grade RBCs could be generated by coculturing with CB-MSCs but not BM-MSCs. Expansion fold and enucleation rate were significantly higher in coculture with CB-MSCs than BM-MSCs. Despite a 2.5-fold expansion of erythroblasts in the presence of TPO and Flt-3 for 8 days, the final RBC count was higher without TPO and Flt-3.

CONCLUSIONS

This study is the first report on generating clinical-grade RBCs by in vitro culture with human MSCs and compared effectiveness of several cytokines for RBC production. This provides a useful basis for future production of clinically available RBCs and a model of erythropoiesis that is analogous to the in vivo system.

Oxygen carriers and cancer chemo- and radiotherapy sensitization: bench to bedside and back

After over a century of preclinical and clinical development, a number of artificial oxygen carriers based either on perfluorochemicals or hemoglobins are currently in advanced clinical trials for their ability to replace red blood cells and to ensure adequate tissue oxygenation in case of acute anemia or infarction. On the other hand, intravenous administration of perflourocarbone emulsions or hemoglobin solutions were effective in increasing the oxygenation throughout experimental tumors, and fueled by exciting new developments in the field, some products are experimentally and clinically investigated as cancer chemo- and radiosensitizing agents. This review is to provide a first overview of the current status of artificial oxygen carriers as a oxygen therapeutics in cancer chemo- and radiotherapy sensitization.