Oxygen therapeutics: pursuit of an alternative to the donor red blood cell

Doping Control Analysis of Perfluorocarbons in Equine Plasma by Headspace Gas Chromatography-Tandem Mass Spectrometry

In order to control the potential misuse of perfluorocarbons as an oxygen carrier in equine sports, a simple and sensitive method for detecting perfluorocarbons in equine plasma by gas chromatography/tandem mass spectrometry using negative chemical ionization with methane as reagent gas has been developed and fully validated. The method covers seven perfluorocarbons, which are the active components in blood substitute products, and shows good sensitivity and robustness. Limits of detection as low as 0.01 ng/mL could be achieved by the method. To the best of our knowledge, this is the first report of a detection method for the screening of perfluorocarbons in equine biological samples.

Synergistic chemotherapy and phototherapy based on red blood cell biomimetic nanomaterials

Novel drug delivery systems (DDSs) have become the mainstay of research in targeted cancer therapy. By combining different therapeutic strategies, potential DDSs and synergistic treatment approaches are needed to effectively deal with evolving drug resistance and the adverse effects of cancer. Nowadays, developing and optimizing human cell-based DDSs has become a new research strategy. Among them, red blood cells can be used as DDSs as they significantly enhance the pharmacokinetics of the transported drug cargo. Phototherapy, as a novel adjuvant in cancer treatment, can be divided into photodynamic therapy and photothermal therapy. Phototherapy using erythropoietic nanocarriers to mimic the unique properties of erythrocytes and overcome the limitations of existing DDSs shows excellent prospects in clinical settings. This review provides an overview of the development of photosensitizers and research on bio-nano-delivery systems based on erythrocytes and erythrocyte membranes that are used in achieving synergistic outcomes during phototherapy/chemotherapy.

Critical Considerations for Regeneration of Vascularized Composite Tissues

Effective vascularization is vital for survival and functionality of complex tissue-engineered organs. The formation of the microvasculature, composed of endothelial cells (ECs) alone, has been mostly used to restore the vascular networks in organs. However, recent heterocellular studies demonstrate that co-culturing is a more effective approach in revascularization of engineered organs. This review presents key considerations for manufacturing of artificial vascularized composite tissues. We summarize the importance of co-cultures and the multicellular interactions with ECs, as well as design and use of bioreactors, as critical considerations for tissue vascularization. In addition, as an emerging scaffolding technique, this review also highlights the current caveats and hurdles associated with three-dimensional bioprinting and discusses recent developments in bioprinting strategies such as four-dimensional bioprinting and its future outlook for manufacturing of vascularized tissue constructs. Finally, the review concludes with addressing the critical challenges in the regulatory pathway and clinical translation of artificial composite tissue grafts. Impact statement Regeneration of composite tissues is critical as biophysical and biochemical characteristics differ between various types of tissues. Engineering a vascularized composite tissue has remained unresolved and requires additional evaluations along with optimization of methodologies and standard operating procedures. To this end, the main hurdle is creating a viable vascular endothelium that remains functional for a longer duration postimplantation, and can be manufactured using clinically appropriate source of cell lines that are scalable in vitro for the fabrication of human-scale organs. This review presents key considerations for regeneration and manufacturing of vascularized composite tissues as the field advances.

Chromatographic separation of hemoglobin variants using robust molecularly imprinted polymers

Devising a robust, efficient and cost effective hemoglobin (Hb) purification strategy is one of the key challenges in the development of Hb-based blood substitutes. The aim of this study was to use molecularly imprinted polymers (MIPs) as a novel and efficient chromatographic resin to selectively recognize and purify different Hb variants. The results showed that the Hb-MIP material developed here could selectively recognize and purify various Hb directly from either crude E. coli extracts or human body fluids, such as blood plasma and cerebrospinal fluid (CSF), in one-step. The dynamic binding capacity at 10% breakthrough was around 7.4 mg mL^-1resin for adult Hb (HbA) and fetal Hb (HbF). This chromatographic material also allowed identification of changes related to amino acid substitutions on the Hb protein surface. For instance, when an additional lysine residue was introduced, the HbA αY42K mutant eluted later in an Hb-MIP column than wildtype HbA. Additional negative charges on the protein surface, such as aspartate, mitigated the interaction between the protein and imprinted polymers, and therefore an αA19D-αA12D HbF mutant eluted earlier, at -2.7 column volumes compared to wildtype HbF.

Current Challenges of Bioprinted Tissues Toward Clinical Translation

IMPACT STATEMENT

This review has a broad overview of the current challenges of bioprinted tissues towards clinical translations and future directions to overcome those challenges. The development of this field has a huge impact on the situation of an insufficient number of organ donors for life-saving organ transplantations.

Applications of particulate oxygen-generating substances (POGS) in the bioartificial pancreas

Type-1 Diabetes (T1D) is a devastating autoimmune disorder which results in the destruction of beta cells within the pancreas. A promising treatment strategy for T1D is the replacement of the lost beta cell mass through implantation of immune-isolated microencapsulated islets referred to as the bioartificial pancreas. The goal of this approach is to restore blood glucose regulation and prevent the long-term comorbidities of T1D without the need for immunosuppressants. A major requirement in the quest to achieve this goal is to address the oxygen needs of islet cells. Islets are highly metabolically active and require a significant amount of oxygen for normal function. During the process of isolation, microencapsulation, and processing prior to transplantation, the islets' oxygen supply is disrupted, and a large amount of islet cells are therefore lost due to extended hypoxia, thus creating a major barrier to clinical success with this treatment. In this work, we have investigated the oxygen generating compounds, sodium percarbonate (SPO) and calcium peroxide (CPO) as potential supplemental oxygen sources for islets during isolation and encapsulation before and immediately after transplantation. First, SPO particles were used as an oxygen source for islets during isolation. Secondly, silicone films containing SPO were used to provide supplemental oxygen to islets for up to 4 days in culture. Finally, CPO was used as an oxygen source for encapsulated cells by co-encapsulating CPO particles with islets in permselective alginate microspheres. These studies provide an important proof of concept for the utilization of these oxygen generating materials to prevent beta cell death caused by hypoxia.

Biologically active polymer nanosystems

The methods of synthesis of biologically active nanostructured systems based on functional and natural polymers are reviewed. The formation of nanosystems in the process of interaction between synthetic water-soluble polyelectrolytes and amphiphilic ionic surfactants is discussed. The influence of structure and stability of these systems on their biological activity is considered. The complexation between DNA and polycations with the formation of compacted DNA molecules, and the transport of resulting complexes into the cells are discussed. The data on nanostructuring of hemoglobin using polyfunctional crosslinkers and the data on the use of the obtained nanoparticles as oxygen-transporting blood substitutes are summarized. Using nanodisperse silver stabilized with poly(vinylpyrrolidone) as an example it was demonstrated, that transferring silver into nanodisperse state results in widening its bioactivity.

Exploring Oxidative Reactions in Hemoglobin Variants Using Mass Spectrometry: Lessons for Engineering Oxidatively Stable Oxygen Therapeutics

SIGNIFICANCE

Worldwide demand has driven the development of hemoglobin (Hb)-based oxygen carriers (HBOCs) as potential acellular oxygen therapeutics. HBOCs have the potential to provide an oxygen bridge to patients and minimize current problems associated with supply and storage of donated blood. However, to date, safety and efficacy issues have hampered the approval of viable HBOCs in the United States. These previous efforts have underscored the need for a better molecular understanding of toxicity to design safe and oxidatively stable HBOCs. Recent Advances: High-resolution accurate mass (HRAM) mass spectrometry (MS) has recently become a versatile tool in characterizing oxidative post-translational modifications that occur in Hb. When integrated with other analytical techniques, HRAM data have been invaluable in providing mechanistic insight into the extent of oxidative modification by quantifying oxidation in amino acids near the reactive heme or at specific "oxidative hotspots."

CRITICAL ISSUES

In addition to providing a deeper understanding of Hb oxidative toxicity, HRAM MS studies are currently being used toward developing suitable HBOCs using a "two-prong" strategy that involves (i) understanding the mechanism of Hb toxicity by evaluating mutant Hbs identified in patients with hemoglobinopathies and (ii) utilizing this information toward designing against (or for) these reactions in acellular oxygen therapeutics that will result in oxidatively stable protein.

FUTURE DIRECTIONS

Future HRAM studies are aimed at fully characterizing engineered candidate HBOCs to determine the most oxidatively stable protein while retaining oxygen carrying function in vivo. Antioxid. Redox Signal. 26, 777-793.

"Inside-Out" PEGylation of Bovine β-Cross-Linked Hemoglobin

The development of a blood substitute is urgent due to blood shortages and potential communicable diseases. A novel method, inside-out PEGylation, has been used here to conjugate a multiarm maleimide-PEG (Mal-PEG) to β-cross-linked (βXL-Hb) hemoglobin (Hb) tetramers through the Cys β93 residues. This method produces a polymer with a single PEG backbone that is surrounded by multiple proteins, rather than coating a single protein with multiple PEG chains. Electrophoresis under denaturing conditions showed a large molecular weight species. Gel filtration chromatography and analytical ultracentrifugation determined the most prevalent species had three βXL-Hb to one Mal-PEG. Thermal denaturation studies showed that the cross-linked and PEGylated species were more stable than native Hb. Cross-linking under oxy-conditions produced a high oxygen affinity Hb species (P₅₀  = 9.18 Torr), but the oxygen affinity was not significantly altered by PEGylation (P₅₀  = 9.67 Torr). Inside-out PEGylation can be used to produce a hemoglobin-based oxygen carrier and potentially for other multiprotein complexes.

Downregulation of metabolic activity increases cell survival under hypoxic conditions: potential applications for tissue engineering

A major challenge to the success of cell-based implants for tissue regeneration is an insufficient supply of oxygen before host vasculature is integrated into the implants, resulting in premature cell death and dysfunction. Whereas increasing oxygenation to the implants has been a major focus in the field, our strategy is aimed at lowering oxygen consumption by downregulating cellular metabolism of cell-based implants. Adenosine, which is a purine nucleoside that functions as an energy transferring molecule, has been reported to increase under hypoxia, resulting in reducing the adenosine triphosphate (ATP) demands of the Na(+)/K(+) ATPase. In the present study, we investigated whether adenosine could be used to downregulate cellular metabolism to achieve prolonged survival under hypoxic conditions. Murine myoblasts (C2C12) lacking a self-survival mechanism were treated with adenosine under 0.1% hypoxic stress. The cells, cultured in the presence of 5 mM adenosine, maintained their viability under hypoxia, and regained their normal growth and function of forming myotubes when transferred to normoxic conditions at day 11 without further supply of adenosine, whereas nontreated cells failed to survive. An increase in adenosine concentrations shortened the onset of reproliferation after transfer to normoxic conditions. This increase correlated with an increase in metabolic downregulation during the early phase of hypoxia. A higher intracellular ATP level was observed in adenosine-treated cells throughout the duration of hypoxia. This strategy of increasing cell survival under hypoxic conditions through downregulating cellular metabolism may be utilized for cell-based tissue regeneration applications as well as protecting tissues against hypoxic injuries.

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.

Frozen Red Blood Cells in Transfusion

Red blood cells (RBCs) can be cryopreserved with shelf life of 10 years. However, shelf life of deglycerolized RBCs in conventional open system is just 24 hours, resulting in sporadic use of Frozen RBC (FS-RBC). Recently Naval Blood Research Laboratory (NBRL) method using ACP 215 (ACP(™) 215 Haemonetics Cell Processing System) has been introduced, where shelf life of deglycerolized RBC is 14 days. FS-RBC unit is prepared from single blood donation, which needs to be glycerolized and deglycerolized. NBRL method using ACP 215 in FS-RBC is described. Deglycerolized unit weighed between 325-350 gm with haemoglobin of 15-18 gm/dl and freeze- thaw- wash RBC recovery of 87%. Transfusion of deglycerolized RBC offered advantages such as elimination of need of crossmatching in emergent situations and reduction of transfusion reactions. FS-RBC by NBRL method using ACP 215 has advantages such as long shelf life, meeting unexpected high blood demand in mass casualties situations or availability of rare blood group requirement of individual patient. FS-RBC can be a potential candidate for Indian Armed Forces Blood programme for uninterrupted blood supply during peace and war.

Perfluorocarbon-based oxygen carriers: review of products and trials

A viable blood substitute is still of great necessity throughout the world. Perfluorocarbon-based oxygen carriers (PFCOCs) are emulsions that take advantage of the high solubility of respiratory gases in perfluorocarbons (PFCs). Despite attractive characteristics, no PFCOC is currently approved for clinical uses. Some PFCOCs have failed due to secondary effects of the surfactants employed, like Fluosol DA, whereas others to adverse cerebrovascular effects on cardiopulmonary bypass, such as Oxygent. Further in-depth, rigorous work is needed to overcome the annotated failures and to obtain a safe PFCOC approved for human use. The aim of this study is to review in detail the most-used PFCOCs, their formulation, and preclinical and clinical trials, and to reflect upon causes of failure and strategies to overcome such failures.

Comparison of Hemoglobin-based oxygen carriers to stored human red blood cells

Since the inception of allogeneic blood transfusion, the search for an alternative to the use of stored packed red blood cells has been underway. Over the last 10 years, modified hemoglobin solutions in the form of hemoglobin-based oxygen carriers (HBOCs) have made significant strides toward becoming clinically available and useful. Although HBOCs are not yet ready for regular use in the clinical arena, this may change in the near future as HBOC products continue to improve and as the elucidation of the mechanisms of any adverse effects becomes clearer. In the mean time, we must further the development of alternative strategies for the "hemoglobin bridge" so desperately needed by many critically ill patients.

Interference in clinical chemistry assays by the hemoglobin-based oxygen carrier, Hemospan

OBJECTIVE

To evaluate interference by the hemoglobin-based oxygen carrier Hemospan on clinical laboratory assays.

DESIGN AND METHODS

Interfering Hemospan concentrations were determined for general chemistry and cardiac marker analytes in pooled serum and the corresponding hemolysis index was calculated.

RESULTS

Hemospan did not interfere with 20 of 35 analytes. Hemospan produced a negative interference in serum creatinine, amylase, alkaline phosphatase, uric acid, and GGT assays and a positive interference in serum phosphate, LDH, iron, triglycerides, total protein, AST, cholesterol, magnesium, and albumin assays, and appeared to positively bias the serum cardiac troponin I (cTnI) assay only when cTnI is present in the sample.

CONCLUSIONS

We present a report of assays affected by Hemospan and the threshold concentrations for interference. This study highlights the importance of interference studies in understanding the effects of hemoglobin-based oxygen carriers on results reported by the clinical laboratory.

Scientific aspects of supplying blood to distant military theaters

PURPOSE OF REVIEW

Reduction in combat zone morbidity and mortality requires rapid delivery of safe blood products as an integral element of advanced trauma surgical care. This review of the current literature presents scientific aspects of supplying blood for rapid delivery to enhance survival and patient outcome in the combat zone.

RECENT FINDINGS

Most deaths due to hemorrhage can be averted by transfusion during the first hour from injury; therefore, maintaining a dependable inventory of blood products in combat support hospitals is essential. Current casualty care in distant geographic locations involves rapid air evacuation to combat support hospitals or fleet hospitals, where massive transfusions may be required. Resuscitation by forward surgical teams utilizing red blood cells before air evacuation or in-flight has also been reported. To improve survival, these massive transfusions should be composed of not only red blood cells but also other blood components and plasma factors.

SUMMARY

Rapid on-site combat casualty transfusion support requires specialized blood transport containers and transfusion practices not observed in noncombat settings, such as the mobile walking blood bank and a frozen blood program. Additionally, technology for improved transport containers, cell-free hemoglobin-based oxygen carriers, freeze-dried blood, and recombinant activated coagulation factor has attracted focused interest.