Optimizing the lyophilization of Lumbricus terrestris erythrocruorin.

Haemorrhagic shock is a leading cause of death worldwide. Blood transfusions can be used to treat patients suffering severe blood loss but donated red blood cells (RBCs) have several limitations that limit their availability and use. To solve the problems associated with donated RBCs, several acellular haemoglobin-based oxygen carriers (HBOCs) have been developed to restore the most important function of blood: oxygen transport. One promising HBOC is the naturally extracellular haemoglobin (i.e. erythrocruorin) of Lumbricus terrestris (LtEc). The goal of this study was to maximise the portability of LtEc by lyophilising it and then testing its stability at elevated temperatures. To prevent oxidation, several cryoprotectants were screened to determine the optimum formulation for lyophilisation that could minimise oxidation of the haem iron and maximise recovery. Furthermore, samples were also deoxygenated prior to storage to decrease auto-oxidation, while resuspension in a solution containing ascorbic acid was shown to partially reduce LtEc that had oxidised during storage (e.g. from 42% Fe3+ to 11% Fe3+). Analysis of the oxygen equilibria and size of the resuspended LtEc showed that the lyophilisation, storage, and resuspension processes did not affect the oxygen transport properties or the structure of the LtEc, even after 6 months of storage at 40 °C. Altogether, these efforts have yielded a shelf-stable LtEc powder that can be stored for long periods at high temperatures, but future animal studies will be necessary to prove that the resuspended product is a safe and effective oxygen transporter in vivo.

Toxic side-effects of diaspirin cross-linked human hemoglobin are attenuated by the apohemoglobin-haptoglobin complex.

Alpha-alpha diaspirin-crosslinked human hemoglobin (DCLHb or ααHb) was a promising early generation red blood cell (RBC) substitute. The DCLHb was developed through a collaborative effort between the United States Army and Baxter Healthcare. The core design feature underlying its development was chemical stabilization of the tetrameric structure of hemoglobin (Hb) to prevent Hb intravascular dimerization and extravasation. DCLHb was developed to resuscitate warfighters on the battlefield, who suffered from life-threatening blood loss. However, extensive research revealed toxic side effects associated with the use of DCLHb that contributed to high mortality rates in clinical trials. This study explores whether scavenging Hb and heme via the apohemoglobin-haptoglobin (apoHb-Hp) complex can reduce DCLHb associated toxicity. Awake Golden Syrian hamsters were equipped with a window chamber model to characterize the microcirculation. Each group was first infused with either Lactated Ringer's or apoHb-Hp followed by a hypovolemic infusion of 10% of the animal's blood volume of DCLHb. Our results indicated that animals pretreated with apoHb-Hb exhibited improved microhemodynamics vs the group pretreated with Lactated Ringer's. While systemic acute inflammation was observed regardless of the treatment group, apoHb-Hp pretreatment lessened those effects with a marked reduction in IL-6 levels in the heart and kidneys compared to the control group. Taken together, this study demonstrated that utilizing a Hb and heme scavenger protein complex significantly reduces the microvasculature effects of ααHb, paving the way for improved HBOC formulations. Future apoHb-Hp dose optimization studies may identify a dose that can completely neutralize DCLHb toxicity.

Synthesis of bioactive hemoglobin-based oxygen carrier nanoparticles via metal-phenolic complexation.

The transfusion of donor red blood cells (RBCs) is seriously hampered by important drawbacks that include limited availability and portability, the requirement of being stored in refrigerated conditions, a short shelf life or the need for RBC group typing and crossmatching. Thus, hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) which make use of the main component of RBCs and the responsible protein for O2 transport, hold a lot of promise in modern transfusion and emergency medicine. Despite the great progress achieved, it is still difficult to create HBOCs with a high Hb content to attain the high O2 demands of our body. Herein a metal-phenolic self-assembly approach that can be conducted in water and in one step to prepare nanoparticles (NPs) fully made of Hb (Hb-NPs) is presented. In particular, by combining Hb with polyethylene glycol, tannic acid (TA) and manganese ions, spherical Hb-NPs with a uniform size around 350-525 nm are obtained. The functionality of the Hb-NPs is preserved as shown by their ability to bind and release O2 over multiple rounds. The binding mechanism of TA and Hb is thoroughly investigated by UV-vis absorption and fluorescence spectroscopy. The binding site number, apparent binding constant at two different temperatures and the corresponding thermodynamic parameters are identified. The results demonstrate that the TA-Hb interaction takes place through a static mechanism in a spontaneous process as shown by the decrease in Gibbs free energy. The associated increase in entropy suggests that the TA-Hb binding is dominated by hydrophobic interactions.

Perfluorocarbons in Research and Clinical Practice: A Narrative Review.

Perfluorocarbons (PFCs) are organic liquids derived from hydrocarbons in which some of the hydrogen atoms have been replaced by fluorine atoms. They are chemically and biologically inert substances with a good safety profile. They are stable at room temperature, easy to store, and immiscible in water. Perfluorocarbons have been studied in biomedical research since 1960 for their unique properties as oxygen carriers. In particular, PFCs have been used for liquid ventilation in unusual environments such as deep-sea diving and simulations of zero gravity, and more recently for drug delivery and diagnostic imaging. Additionally, when delivered as emulsions, PFCs have been used as red blood cell substitutes. This narrative review will discuss the multifaceted utilization of PFCs in therapeutics, diagnostics, and research. We will specifically emphasize the potential role of PFCs as red blood cell substitutes, as airway mechanotransducers during artificial placenta procedures, as a means to improve donor organ perfusion during the ex vivo assessment, and as an adjunct in cancer therapies because of their ability to reduce local tissue hypoxia.

Poly(2-ethyl-2-oxazoline)-Conjugated Hemoglobins as a Red Blood Cell Substitute.

Hemoglobin wrapped covalently with poly(2-ethyl-2-oxazoline)s (POx-Hb) is characterized physicochemically and physiologically as an artificial O2 carrier for use as a red blood cell (RBC) substitute. The POx-Hb is generated by linkage of porcine Hb surface-lysines to a sulfhydryl terminus of the POx derivative, with the average binding number of the polymers ascertained as 6. The POx-Hb shows moderately higher colloid osmotic activity and O2 affinity than the naked Hb. Human adult HbA conjugated with POx also possesses equivalent features and O2 binding properties. The POx-Hb solution exhibits good hemocompatibility, with no influence on the functions of platelets, granulocytes, and monocytes. Its circulation half-life in rats is 14 times longer than that of naked Hb. Hemorrhagic shock in rats is relieved sufficiently by infusion of the POx-Hb solution, as revealed by improvements of circulatory parameters. Serum biochemistry tests and histopathological observations indicate no acute toxicity or abnormality in the related organs. All results indicate that POx-Hb represents an attractive alternative for RBCs and a useful O2 therapeutic reagent in transfusion medicine.

The artificial oxygen carrier erythrocruorin-characteristics and potential significance in medicine.

The diminishing supply and increasing costs of donated blood have motivated research into novel hemoglobin-based oxygen carriers (HBOCs) that can serve as red blood cell (RBC) substitutes. HBOCs are versatile agents that can be used in the treatment of hemorrhagic shock. However, many of the RBC substitutes that are based on mammalian hemoglobins have presented key limitations such as instability and toxicity. In contrast, erythrocruorins (Ecs) are other types of HBOCs that may not suffer these disadvantages. Ecs are giant metalloproteins found in annelids, crustaceans, and some other invertebrates. Thus far, the Ecs of Lumbricus terrestris (LtEc) and Arenicola marina (AmEc) are the most thoroughly studied. Based on data from preclinical transfusion studies, it was found that these compounds not only efficiently transport oxygen and have anti-inflammatory properties, but also can be modified to further increase their effectiveness. This literature review focuses on the structure, properties, and application of Ecs, as well as their advantages over other HBOCs. Development of methods for both the stabilization and purification of erythrocruorin could confer to enhanced access to artificial blood resources.

ZIF-8 metal organic framework nanoparticle loaded with tense quaternary state polymerized bovine hemoglobin: potential red blood cell substitute with antioxidant properties.

Due to several limitations associated with blood transfusion, such as the relatively short shelf life of stored blood, low risk of developing acute immune hemolytic reactions and graft-versus-host disease, many strategies have been developed to synthesize hemoglobin-based oxygen carriers (HBOCs) as universal red blood cell (RBC) substitutes. Recently, zeolite imidazole framework-8 (ZIF-8), a metal-organic framework, has attracted considerable attention as a protective scaffold for encapsulation of hemoglobin (Hb). Despite the exceptional thermal and chemical stability of ZIF-8, the major impediments to implementing ZIF-8 for Hb encapsulation are the structural distortions associated with loading large quantities of Hb in the scaffold as the Hb molecule has a larger hydrodynamic diameter than the pore size of ZIF-8. Therefore to reduce the structural distortion caused by Hb encapsulation, we established and optimized a continuous-injection method to synthesize nanoparticle (NP) encapsulated polymerized bovine Hb (PolybHb) using ZIF-8 precursors (ZIF-8P-PolybHb NPs). The synthesis method was further modified by adding EDTA as a chelating agent, which reduced the ZIF-8P-PolybHb NP size to <300 nm. ZIF-8P-PolybHb NPs exhibited lower oxygen affinity (36.4 ± 3.2 mm Hg) compared to unmodified bovine Hb, but was similar in magnitude to unencapsulated PolybHb. The use of the chemical cross-linker glutaraldehyde to polymerize bovine Hb resulted in the low Hill coefficient of PolybHb, indicating loss of Hb's oxygen binding cooperativity, which could be a limitation when using PolybHb as an oxygen carrier for encapsulation inside the ZIF-8 matrix. ZIF-8P-PolybHb NPs exhibited slower oxygen offloading kinetics compared to unencapsulated PolybHb, demonstrating successful encapsulation of PolybHb. ZIF-8P-PolybHb NPs also exhibited favorable antioxidant properties when exposed to H2O2. Incorporation of PolybHb into the ZIF-8 scaffold resulted in reduced cytotoxicity towards human umbilical vein endothelial cells compared to unloaded ZIF-8 NPs and ZIF-8 NPs loaded with bovine Hb. We envisage that such a monodisperse and biocompatible HBOC with low oxygen affinity and antioxidant properties may broaden its use as an RBC substitute.

Photocatalytic Synthesis of a Polydopamine-Coated Acellular Mega-Hemoglobin as a Potential Oxygen Therapeutic with Antioxidant Properties.

Hemoglobin-based oxygen carriers (HBOCs) are being developed to overcome limitations associated with transfusion of donated red blood cells (RBCs) such as potential transmission of blood-borne pathogens and limited ex vivo storage shelf-life. Annelid erythrocruorin (Ec) derived from the worm Lumbricus terrestris (Lt) is an acellular mega-hemoglobin that has shown promise as a potential HBOC due to the large size of its oligomeric structure, thus overcoming limitations of unmodified circulating cell-free hemoglobin (Hb). With a large molecular weight of 3.6 MDa compared to 64.5 kDa for human Hb (hHb) and 144 oxygen-binding globin subunits compared to the 4 globin subunits of hHb, LtEc does not extravasate from the circulation to the same extent as hHb. LtEc is stable in the circulation without RBC membrane encapsulation and has a lower rate of auto-oxidation compared to acellular hHb, which allows the protein to remain functional for longer periods of time in the circulation compared to HBOCs derived from mammalian Hbs. Surface coatings, such as poly(ethylene glycol) (PEG) and oxidized dextran (Odex), have been investigated to potentially reduce the immune response and improve the circulation time of LtEc in vivo. Polydopamine (PDA) is a hydrophilic, biocompatible, bioinspired polymer coating used for biomedical nanoparticle assemblies and coatings and has previously been investigated for the surface coating of hHb. PDA is typically synthesized via the self-polymerization of dopamine (DA) under alkaline (pH > 8.0) conditions. However, at pH > 8.0, the oligomeric structure of LtEc begins to dissociate. Therefore, in this study, we investigated a photocatalytic method of PDA polymerization on the surface of LtEc using 9-mesityl-10-methylacridinium tetrafluoroborate (Acr-Mes) to drive PDA polymerization under physiological conditions (pH 7.4, 25 °C) over 2, 5, and 16 h in order to preserve the size and structure of LtEc. The resulting structural, biophysical, and antioxidant properties of PDA surface-coated LtEc (PDA-LtEc) was characterized using various techniques. PDA-LtEc showed an increase in measured particle size, molecular weight, and surface ζ-potential with increasing reaction time from t = 2 to 16 h compared to unmodified LtEc. PDA-LtEc reacted for 16 h was found to have reduced oxygen-binding cooperativity and slower deoxygenation kinetics compared to PDA-LtEc with lower levels of polymerization (t = 2 h), but there was no statistically significant difference in oxygen affinity. The thickness of the PDA coating can be controlled and in turn the biophysical properties can be tuned by changing various reaction conditions. PDA-LtEc was shown to demonstrate an increased level of antioxidant capacity (ferric iron reduction and free-radical scavenging) when synthesized at a reaction time of t = 16 h compared to LtEc. These antioxidant properties may prove beneficial for oxidative protection of PDA-LtEc during its time in the circulation. Hence, we believe that PDA-LtEc is a promising oxygen therapeutic for potential use in transfusion medicine applications.

Selective Attachment of Polyethylene Glycol to Hemerythrin for Potential Use in Blood Substitutes.

Due to its ability to reversibly bind O2, alongside a relatively low redox reactivity and a limited cytotoxicity, the oxygen-carrying protein hemerythrin has been considered as an alternative to hemoglobin in preparing blood substitutes. In order to increase the hydrodynamic volume and lower antigenicity, two site-directed variants, H82C and K92C, were engineered that contained a single cysteine residue on the surface of each hemerythrin octamer for the specific attachment of polyethylene glycol (PEG). A sulfhydryl-reactive PEGylation reagent with a 51.9 Å spacer arm was used for selective cysteine derivatization. The mutants were characterized by UV-vis spectroscopy, size-exclusion chromatography, oxygen affinity, and autooxidation rate measurements. The H82C variant showed altered oligomeric behavior compared to the wild-type and was unstable in the met form. The PEGylated K92C variant is reasonably stable, displays an oxygen affinity similar to that of the wild-type, and shows an increased rate of autoxidation; the latter disadvantage may be counteracted by further chemical modifications.

Core-Shell Structured Hemoglobin Nanoparticles as Artificial O2 Carriers.

This paper describes the synthesis and O2 binding properties of core-shell structured hemoglobin (Hb) nanoparticles (NPs), artificial O2 carriers of five types, as designed for use as red blood cell (RBC) substitutes. Human adult Hbs were polymerized using α-succinimidyl-ω-maleimide and dithiothreitol in spheroidal shapes to create parent particles. Subsequent covalent wrapping of the sphere with human serum albumin (HSA) yielded 100 nm-diameter Hb nanoparticles (HbNPs). The HbNP showed higher O2 affinity than that of RBC, but NPs prepared under a N2 atmosphere exhibited low O2 affinity. Entirely synthetic particles comprising recombinant human adult Hb and recombinant HSA were also fabricated. Using a recombinant Hb (rHb) variant in which Leu-ß28 of the heme pocket had been replaced with Phe, we found somewhat low O2 affinity of rHb(ßL28F)NP. Particles made of stroma-free Hb (SFHb) containing natural antioxidant enzyme catalase (SFHbNP) formed a very stable O2 complex, even in aqueous H2O2 solution. The SFHbNP showed good blood compatibility and did not affect the blood cell component functionality. The circulation half-life of SFHbNP in rats was considerably longer than that of naked Hb. All results indicate these Hb-based NPs as useful alternative materials for RBC and as a useful O2 therapeutic reagent in diverse medical scenarios.

Hemoglobin-based oxygen carriers camouflaged with membranes extracted from red blood cells: Optimization and assessment of functionality.

Despite being an indispensable clinical procedure, the transfusion of donor blood has important limitations including a short shelf-life, limited availability and specific storage requirements. Therefore, a lot of effort has been devoted to developing hemoglobin (Hb)-based oxygen carriers (HBOCs) that are able to replace or complement standard blood transfusions, especially in extreme life-threatening situations. Herein, we employed a Hb-loaded poly(lactide-co-glycolide) core which was subsequently coated with nanozymes to protect the encapsulated Hb from oxidation by reactive oxygen species. To render HBOCs with long circulation in the vasculature, which is a crucial requirement to achieve the high oxygen demands of our organism, the carrier was coated with a red blood cell-derived membrane. Three coating methods were explored and evaluated by their ability to repel the deposition of proteins and minimize their uptake by an endothelial cell line. Preservation of the oxygen carrying capacity of the membrane-coated carrier was demonstrated by an oxygen-binding and releasing assay and, the functionality resulting from the entrapped nanozymes, was shown by means of superoxide radical anion and hydrogen peroxide depletion assays. All in all, we have demonstrated the potential of the membrane-coated nanocarriers as novel oxygen carrying systems with both antioxidant and stealth properties.

Tangential flow filtration facilitated fractionation and PEGylation of low and high-molecular weight polymerized hemoglobins and their biophysical properties.

Various types of hemoglobin (Hb)-based oxygen carriers (HBOCs) have been developed as red blood cell substitutes for treating blood loss when blood is not available. Among those HBOCs, glutaraldehyde polymerized Hbs have attracted significant attention due to their facile synthetic route, and ability to expand the blood volume and deliver oxygen. Hemopure®, Oxyglobin®, and PolyHeme® are the most well-known commercially developed glutaraldehyde polymerized Hbs. Unfortunately, only Oxyglobin® was approved by the FDA for veterinary use in the United States, while Hemopure® and PolyHeme® failed phase III clinical trials due to their ability to extravasate from the blood volume into the tissue space which facilitated nitric oxide scavenging and tissue deposition of iron, which elicited vasoconstriction, hypertension and oxidative tissue injury. Fortunately, conjugation of poly (ethylene glycol) (PEG) on the surface of Hb is capable of reducing the vasoactivity of Hb by creating a hydration layer surrounding the Hb molecule, which increases its hydrodynamic diameter and reduces tissue extravasation. Several commercial PEGylated Hbs (MP4®, Sanguinate®, Euro-PEG-Hb) have been developed for clinical use with a longer circulatory half-life and improved safety compared to Hb. However, all of these commercial products exhibited relatively high oxygen affinity compared to Hb, which limited their clinical use. To dually address the limitations of prior generations of polymerized and PEGylated Hbs, this current study describes the PEGylation of polymerized bovine Hb (PEG-PolybHb) in both the tense (T) and relaxed (R) quaternary state via thiol-maleimide chemistry to produce an HBOC with low or high oxygen affinity. The biophysical properties of PEG-PolybHb were measured and compared with those of commercial polymerized and PEGylated HBOCs. T-state PEG-PolybHb possessed higher hydrodynamic volume and P50 than previous generations of commercial PEGylated Hbs. Both T- and R-state PEG-PolybHb exhibited significantly lower haptoglobin binding rates than the precursor PolybHb, indicating potentially reduced clearance by CD163 + monocytes and macrophages. Thus, T-state PEG-PolybHb is expected to function as a promising HBOC due to its low oxygen affinity and enhanced stealth properties afforded by the PEG hydration shell.

From hemoglobin allostery to hemoglobin-based oxygen carriers.

Hemoglobin (Hb) plays its vital role through structural and functional properties evolutionarily optimized to work within red blood cells, i.e., the tetrameric assembly, well-defined oxygen affinity, positive cooperativity, and heterotropic allosteric regulation by protons, chloride and 2,3-diphosphoglycerate. Outside red blood cells, the Hb tetramer dissociates into dimers, which exhibit high oxygen affinity and neither cooperativity nor allosteric regulation. They are prone to extravasate, thus scavenging endothelial NO and causing hypertension, and cause nephrotoxicity. In addition, they are more prone to autoxidation, generating radicals. The need to overcome the adverse effects associated with cell-free Hb has always been a major hurdle in the development of substitutes of allogeneic blood transfusions for all clinical situations where blood is unavailable or cannot be used due to, for example, religious objections. This class of therapeutics, indicated as hemoglobin-based oxygen carriers (HBOCs), is formed by genetically and/or chemically modified Hbs. Many efforts were devoted to the exploitation of the wealth of biochemical and biophysical information available on Hb structure, function, and dynamics to design safe HBOCs, overcoming the negative effects of free plasma Hb. Unfortunately, so far, no HBOC has been approved by FDA and EMA, except for compassionate use. However, the unmet clinical needs that triggered intensive investigations more than fifty years ago are still awaiting an answer. Recently, HBOCs "repositioning" has led to their successful application in organ perfusion fluids.

Ferrous hemoglobin and hemoglobin-based oxygen carriers acting as a peroxidase can inhibit oxidative damage to endothelial cells caused by hydrogen peroxide.

Oxidative damage caused by the ferryl hemoglobin is one of the major clinical adverse reactions of hemoglobin-based oxygen carriers (HBOCs), while the production of reactive oxygen species in a pathological state can oxidize hemoglobin (HbFe2+ ) to ferryl Hb, which can then enter the pseudoperoxidase cycle, making hemoglobin highly toxic. In this study, we found that ferrous hemoglobin and polymerized porcine hemoglobin (one of the HBOCs) have the peroxidase activity different from the pseudoperoxidase activity of ferric hemoglobin. Ferrous hemoglobin can catalyze the reaction of tyrosine (Tyr) with hydrogen peroxide. In addition, the results also indicated that ferrous hemoglobin and pPolyHb have a strong inhibitory effect on the pseudoperoxidase activity of ferric hemoglobin. Therefore, hydrogen peroxide was consumed in a large amount, which greatly prevented hemoglobin from becoming oxidized and entering the pseudoperoxidase cycle, thus inhibiting ferryl Hb toxicity. We further cultured human umbilical vein endothelial cells and monitored cell morphology, viability, cell cycle, apoptosis, lactate dehydrogenase (LDH) release, and malondialdehydes (MDAs) formation when incubated with H2 O2 , Tyr, and HbFe2+ . HbFe2+ and pPolyHb reduced cell cycle arrest, apoptosis, LDH release, and MDA formation. These results showed that reducing oxidative damage induced by H2 O2 and converted hemoglobin from a molecule that is toxic to one that inhibits oxidative damage, suggesting a new strategy for development of a safer HBOCs.

Hemoglobin coated oxygen storage metal-organic framework as a promising artificial oxygen carrier.

Hemoglobin-functionalized HKUST-1 as an artificial oxygen carrier has been developed. The new oxygen carrier has excellent oxygen loading capacity and good chemical durability. The sustained electrochemical responses toward H2O2 and O2 make this new material an ideal candidate as a promising artificial blood substitute.

Capsules from synthetic diblock-peptides as potential artificial oxygen carriers.

The design of an encapsulation system consisting of a synthetic peptide which is fully biodegradable into non-toxic constituents. This system should be capable of encapsulating perfluorinated hydrocarbons and should be a promising basis for oxygen carriers to be used as artificial blood replacement. A diblock-peptide is synthesised following a phosgene-free method and characterised by 1H-NMR. Subsequently, this diblock-peptide is self-assembled with perfluorodecalin (PFD) to form PFD-filled capsules as potential artificial oxygen carriers allowing for rapid oxygen uptake and release. The diblock-peptide Bu-PAsp10-PPhe10 is successfully synthesised and used to encapsulate PFD. The capsules have a spherical shape with an average diameter of 360 nm in stable aqueous dispersion. NMR measurements prove their physical capability for reversible uptake and release of oxygen. The resulting capsules are expected to be fully biodegradable and possibly could act as oxygen carriers for artificial blood replacement.

Blood Substitutes and Oxygen Therapeutics: A Review.

Despite the exhaustive search for an acceptable substitute to erythrocyte transfusion, neither chemical-based products such as perfluorocarbons nor hemoglobin-based oxygen carriers have succeeded in providing a reasonable alternative to allogeneic blood transfusion. However, there remain scenarios in which blood transfusion is not an option, due to patient's religious beliefs, inability to find adequately cross-matched erythrocytes, or in remote locations. In these situations, artificial oxygen carriers may provide a mortality benefit for patients with severe, life-threatening anemia. This article provides an up-to-date review of the history and development, clinical trials, new technology, and current standing of artificial oxygen carriers as an alternative to transfusion when blood is not an option.

Immunosensor incorporating half-antibody fragment for electrochemical monitoring of amyloid-ß fibrils in artificial blood plasma.

In this report, an electrochemical immunosensor for the selective and sensitive monitoring of Aß1-42 fibrils is presented. The sensing platform was prepared by the formation of a 4,4'-thiobisbenzenethiol (TBBT) self-assembled monolayer on a clean gold surface followed by the covalent entrapment of gold nanoparticles (AuNPs). The half-antibody fragments of the Anti-Amyloid Fibrils antibody were immobilized on AuNPs via S-Au covalent bonds. Each step of immunosensor fabrication was characterized with cyclic voltammetry and electrochemical impedance spectroscopy. The biosensor was successfully used for the sensing of Aß1-42 fibrils in both phosphate saline buffer (PBS) and artificial blood plasma (ABP). The immunosensor sensitivity estimated based on calibration slopes was better in the presence of APP in the comparison to PBS. The LOD values obtained for both measuring media were of 0.6 pM level. The moderate response towards Aß1-42 oligomers demonstrated the immunosensor selectivity.

Pullulan in biomedical research and development - A review.

Pullulan is an imperative microbial exo-polymer commercially produced by yeast like fungus Aureobasidium pullulans. Its structure contains maltosyl repeating units which comprises two α-(1 â†’ 4) linked glucopyranose rings attached to one glucopyranose ring through α-(1 â†’ 6) glycosidic bond. The co-existence of α-(1 â†’ 6) and α-(1 â†’ 4) glycosidic linkages endows distinctive physico-chemical properties to pullulan. It is highly biocompatible, non-toxic and non-carcinogenic in nature. It is extremely resistant to any mutagenicity or immunogenicity. The unique properties of pullulan make it a potent candidate for biomedical applications viz. drug delivery, gene delivery, tissue engineering, molecular chaperon, plasma expander, vaccination, etc. This review highlights the potential of pullulan in biomedical research and development.

Perfluorocarbon-based oxygen carriers: from physics to physiology.

Developing biocompatible, synthetic oxygen carriers is a consistently challenging task that researchers have been pursuing for decades. Perfluorocarbons (PFC) are fascinating compounds with a huge capacity to dissolve gases, where the respiratory gases are of special interest for current investigations. Although largely chemically and biologically inert, pure PFCs are not suitable for injection into the vascular system. Extensive research created stable PFC nano-emulsions that avoid (i) fast clearance from the blood and (ii) long organ retention time, which leads to undesired transient side effects. PFC-based oxygen carriers (PFOCs) show a variety of application fields, which are worthwhile to investigate. To understand the difficulties that challenge researchers in creating formulations for clinical applications, this review provides the physical background of PFCs' properties and then illuminates the reasons for instabilities of PFC emulsions. By linking the unique properties of PFCs and PFOCs to physiology, it elaborates on the response, processing and dysregulation, which the body experiences through intravascular PFOCs. Thereby the reader will receive a scientific and easily comprehensible overview why PFOCs are precious tools for so many diverse application areas from cancer therapeutics to blood substitutes up to organ preservation and diving disease.