Purification of bovine hemoglobin via fast performance liquid chromatography

Self-polymerization silica nanoparticles based molecularly imprinted polymers for selective recognition of protein

Molecularly imprinted polymers (MIPs) are promising for precise protein separation and purification. However, challenges persist due to their large size, variable configuration, and instability during preparation. Here, a simple silicon self-assembly program was designed to synthesize MIPs without any organic reagents and acid-base catalysis, avoiding the structural damage of protein under severe conditions. In this method, employing hemoglobin (Hb) as a model protein, with tween-20 in emulsification, and tetraethyl orthosilicate (TEOS) as the cross-linking agent, along with co-functional monomers 3-aminopropyltriethoxysilane (APTES) and benzyl(triethoxy)silane (BnTES), enhanced binding efficacy was achieved. Successful imprinting was evidenced through surface morphology observation and physical/chemical property evaluations of the synthesized MIPs. A series of adsorption experiments were performed to investigate the recognition performance of Hb-MIPs. The Hb-MIPs not only exhibited large adsorption capacity (400 μg/mg) and good imprinting factor (6.09) toward template protein, but also showed satisfactory selectivity for reference proteins. Five cycles of adsorption proved that the Hb-MIPs had good reusability. In addition, the successful isolation of HB from bovine blood indicated that Hb-MIPs were an excellent separation and purification material. The mild preparation conditions and good adsorption capacity demonstrated the potential value of this method in separation and purification research.

An intelligent intestinal bleeding diagnosis and treatment capsule system based on color recognition

To our best knowledge, there are no non-invasive and painless means for the diagnosis and treatment of intestinal bleeding as of now, especially the segment of intestine that cannot be reached by endoscopy. We proposed an intelligent intestinal bleeding diagnosis and treatment capsule (IBDTC) system for the first time to diagnose and treat intestinal bleeding with low power consumption, estimated to be about 2.16mW. A hue-saturation-light (HSL) color space method was applied to diagnose bleeding according to H (hue) values of the film dyed by blood. A MEMS-based micro-igniter works as the critical component of the micro-thruster that houses the propellant (74.6% potassium nitrate, 11.9% sulfur, 13.5% charcoal) and the detonating agent (dinitrodiazophenol), to help release drug. Bleeding detection and ignition tests were performed to justify its feasibility and reliability. Results demonstrated that the bleeding diagnosis module of the IBDTC can effectively detect bleeding and the micro-igniter can successfully ignite the propellant. Owing to its simplicity and intelligence, the IBDTC system will pave a way for future accurate treatment of small intestinal bleeding with no injury, no pain, no complicated supporting equipment, no need for in vitro operation and positioning.

Red Blood Cell Substitutes: Liposome Encapsulated Hemoglobin and Magnetite Nanoparticle Conjugates as Oxygen Carriers

The established blood donation and transfusion system has contributed a lot to human health and welfare, but for this system to function properly, it requires a sufficient number of healthy donors, which is not always possible. Pakistan was a country hit hardest by COVID-19 which additionally reduced the blood donation rates. In order to address such challenges, the present study focused on the development of RBC substitutes that can be transfused to all blood types. This paper reports the development and characterization of RBC substitutes by combining the strategies of conjugated and encapsulated hemoglobin where magnetite nanoparticles would act as the carrier of hemoglobin, and liposomes would separate internal and external environments. The interactions of hemoglobin variants with bare magnetite nanoparticles were studied through molecular docking studies. Moreover, nanoparticles were synthesized, and hemoglobin was purified from blood. These components were then used to make conjugates, and it was observed that only the hemoglobin HbA1 variant was making protein corona. These conjugates were then encapsulated in liposomes to make negatively charged RBC substitutes with a size range of 1-2 μm. Results suggest that these RBC substitutes work potentially in a similar way as natural RBCs work and can be used in the time of emergency.

A model to visualize the fate of iron after intracranial hemorrhage using isotopic tracers and elemental bioimaging

Hemoglobin-iron is a red-blood-cell toxin contributing to secondary brain injury after intracranial bleeding. We present a model to visualize an intracerebral hematoma and secondary hemoglobin-iron distribution by detecting 58Fe-labeled hemoglobin (Hb) with laser ablation-inductively coupled plasma-mass spectrometry on mouse brain cryosections after stereotactic whole blood injection for different time periods. The generation of 58Fe-enriched blood and decisive steps in the acute hemorrhage formation and evolution was evaluated. The model allows to visualize and quantify 58Fe with high spatial resolution and striking signal-to-noise ratio. Script-based evaluation of the delocalization-depth revealed ongoing 58Fe delocalization in the brain even six days after hematoma induction. Collectively, the model can quantify the distribution of Hb-derived iron post-bleeding, providing a methodological framework to study the pathophysiological basis of cell-free Hb toxicity in hemorrhagic stroke.

Purification of Lumbricus terrestris erythrocruorin (LtEc) with anion exchange chromatography

The naturally extracellular hemoglobin (erythrocruorin) of the Canadian nightcrawler, Lumbricus terrestris (LtEc), is a unique oxygen transport protein that may be an effective substitute for donated human blood. Indeed, this ultra-high molecular weight (~3.6 MDa) hemoglobin has already been shown to avoid the side effects associated with previous hemoglobin-based oxygen carriers and its high thermal stability (T_m = 56°C) and resistance to heme oxidation (k_ox = 0.04 hr^-1 × 10³ at 20°C) allow it to be stored for long periods of time without refrigeration. However, before it can be tested in human clinical trials, an effective and scalable purification process for LtEc must be developed. We have previously purified LtEc for animal studies with tangential flow filtration (TFF), which allows rapid and scalable purification of LtEc based on its relatively large size, but that type of size-based purification may not be able to specifically remove some impurities and high MW (>500 kDa) contaminants like endotoxin (MW = ~1-4 MDa). Anion exchange (AEX) and immobilized metal affinity chromatography (IMAC) are two purification methods that have been previously used to purify mammalian hemoglobins, but they have not yet been used to purify large invertebrate hemoglobins like LtEc. Therefore, the goal of this study was to determine if AEX and IMAC resins could successfully purify LtEc from crude earthworm homogenate, while also preserving its macromolecular structure and function. Both processes were able to produce purified LtEc with low levels of endotoxin, but IMAC purification induced significantly higher levels of heme oxidation and subunit dissociation than AEX. In addition, the IMAC process required an additional desalting step to enable LtEc binding. In contrast, AEX produced highly pure LtEc that was not dissociated. LtEc purified by AEX also exhibits similar oxygen binding characteristics (P₅₀ = 27.33 ± 1.82 mm Hg, n = 1.58 ± 0.17) to TFF-purified LtEc (P₅₀ = 28.84 ± 0.40 mm Hg, n = 1.93 ± 0.02). Therefore, AEX appears to be the optimal method for LtEc purification.

A Smart Capsule System for Automated Detection of Intestinal Bleeding Using HSL Color Recognition

There are no ideal means for the diagnosis of intestinal bleeding diseases as of now, particularly in the small intestine. This study investigated an intelligent intestinal bleeding detection capsule system based on color recognition. After the capsule is swallowed, the bleeding detection module (containing a color-sensitive adsorptive film that changes color when absorbing intestinal juice,) is used to identify intestinal bleeding features. A hue-saturation-light color space method can be applied to detect bleeding according to the range of H and S values of the film color. Once bleeding features are recognized, a wireless transmission module is activated immediately to send an alarm signal to the outside; an in vitro module receives the signal and sends an alarm. The average power consumption of the entire capsule system is estimated to be about 2.1mW. Owing to its simplicity, reliability, and effectiveness, this system represents a new approach to the clinical diagnosis of intestinal bleeding diseases.

Polychelated cryogels: hemoglobin adsorption from human blood

The separation and purification methods are extremely important for the hemoglobin (Hb) which is a crucial biomolecule. The adsorption technique is popular among these methods and the cryogels have been used quite much due to their macropores and interconnected flow channels. In this study, the Hb adsorption onto the Cu(II) immobilized poly(2-hydroxyethyl methacrylate-glycidyl methacrylate), poly(HEMA-GMA)-Cu(II), cryogels was investigated under different conditions (pH, interaction time, initial Hb concentration, temperature and ionic strength) to optimize adsorption conditions. The swelling test, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), surface area (BET), elemental and ICP-OES analysis were performed for the characterization of cryogels. Polyethyleneimine (PEI) molecule was used as a Cu(II)-chelating ligand. The Hb adsorption capacity of cryogels was determined as 193.8 mg Hb/g cryogel. The isolation of Hb from human blood was also studied under optimum adsorption conditions determined and the Hb (124.5 mg/g cryogel) was isolated. The adsorption model was investigated in the light of Langmuir and Freundlich adsorption isotherm models and it was determined to be more appropriate to the Langmuir adsorption isotherm model.

Progressive Saturation Improves the Encapsulation of Functional Proteins in Nanoscale Polymer Vesicles

PURPOSE

To develop a technique that maximizes the encapsulation of functional proteins within neutrally charged, fully PEGylated and nanoscale polymer vesicles (i.e., polymersomes).

METHODS

Three conventional vesicle formation methods were utilized for encapsulation of myoglobin (Mb) in polymersomes of varying size, PEG length, and membrane thickness. Mb concentrations were monitored by UV-Vis spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES) and by the bicinchoninic acid (BCA) assay. Suspensions were subject to protease treatment to differentiate the amounts of surface-associated vs. encapsulated Mb. Polymersome sizes and morphologies were monitored by dynamic light scattering (DLS) and by cryogenic transmission electron microscopy (cryo-TEM), respectively. Binding and release of oxygen were measured using a Hemeox analyzer.

RESULTS

Using the established "thin-film rehydration" and "direct hydration" methods, Mb was found to be largely surface-associated with negligible aqueous encapsulation within polymersome suspensions. Through iterative optimization, a novel "progressive saturation" technique was developed that greatly increased the final concentrations of Mb (from < 0.5 to > 2.0 mg/mL in solution), the final weight ratio of Mb-to-polymer that could be reproducibly obtained (from < 1 to > 4 w/w% Mb/polymer), as well as the overall efficiency of Mb encapsulation (from < 5 to > 90%). Stable vesicle morphologies were verified by cryo-TEM; the suspensions also displayed no signs of aggregate formation for > 2 weeks as assessed by DLS. "Progressive saturation" was further utilized for the encapsulation of a variety of other proteins, ranging in size from 17 to 450 kDa.

CONCLUSIONS

Compared to established vesicle formation methods, "progressive saturation" increases the quantities of functional proteins that may be encapsulated in nanoscale polymersomes.

Characterization of a 12 kDa thermal-stable antigenic protein in bovine blood

We have previously developed an immunoassay based on monoclonal antibody (MAb) Bb1H9 for quantitative detection of ruminant blood in processed food and feedstuffs. The purpose of this study was to characterize the unknown 12 kDa thermal-stable ruminant-specific antigenic protein recognized by MAb Bb1H9 in order to better define the application scope of the developed assay. Extracts obtained from raw and heat-treated bovine blood-derived products were analyzed with indirect ELISA and Western blot. Target proteins resolved by 2D electrophoresis were subjected to N-terminal sequencing. Results indicated that the 12 kDa protein is a monomer of the tetrameric hemoglobin molecule (64.5 kDa) and that the heme group is not required for its binding with MAb Bb1H9. This MAb can be utilized as a probe for red blood cell derived products of ruminant origin in raw or processed food and feedstuffs to enforce labeling regulations and to address consumer concerns.

PRACTICAL APPLICATION

MAb Bb1H9 represents the first antibody with the capacity to recognize bovine hemoglobin both in the absence and presence of the heme group, regardless of the heat treatment. MAb Bb1H9 can therefore be utilized in immunoassays by manufacturers and regulators to detect any ingredients containing hemoglobin or globin (hemoglobin without the heme group) in both raw and processed food and feed materials for product quality control and labeling law enforcement.

The quaternary structure of tetrameric hemoglobin regulates the oxygen affinity of polymerized hemoglobin

This study focuses on the effect of the initial quaternary structure of bovine hemoglobin (Hb) on the physical properties of glutaraldehyde polymerized Hb (PolyHb) solutions. Tense (T) state PolyHb was synthesized by maintaining the pO(2) of Hb before and after polymerization at 0 mm Hg. In contrast, relaxed (R) state PolyHb was generated by maintaining the pO(2) of Hb before and after polymerization to >749 mm Hg. PolyHb solutions were characterized by measuring the pO(2), methemoglobin (metHb) level, molecular weight distribution, O(2) affinity and cooperativity coefficient. The metHb level of all PolyHb solutions was low (<2%). Analysis of the molecular weight distribution of PolyHb solutions indicates that in general, the molecular weight of PolyHb solutions increased with increasing cross-link density. T-state PolyHb solutions exhibited lower O(2) affinity compared to unmodified Hb, whereas R-state PolyHb solutions exhibited higher O(2) affinity compared to unmodified Hb. In addition, the polymerization reaction resulted in a significant decrease in cooperativity that was more pronounced at higher cross-link densities. All of these results were explained in terms of the quaternary structure of Hb. Taken together, our results yield more insight into the importance Hb's quaternary structure plays in defining the physical properties of glutaraldehyde PolyHb solutions. This information will be useful in designing optimized glutaraldehyde PolyHb oxygen carriers for various applications in transfusion medicine.

Purification of hemoglobin by tangential flow filtration with diafiltration

A recent study by Palmer, Sun, and Harris (Biotechnol. Prog., 25:189-199, 2009) demonstrated that tangential flow filtration (TFF) can be used to produce HPLC-grade bovine and human hemoglobin (Hb). In this current study, we assessed the quality of bovine Hb (bHb) purified by introducing a 10 L batch-mode diafiltration step to the previously mentioned TFF Hb purification process. The bHb was purified from bovine red blood cells (RBCs) by filtering clarified RBC lysate through 50 nm (stage I) and 500 kDa (stage II) hollow fiber (HF) membranes. The filtrate was then passed through a 100 kDa (stage III) HF membrane with or without an additional 10 L diafiltration step to potentially remove additional small molecular weight impurities. Protein assays, SDS-PAGE, and LC-MS of the purified bHb (stage III retentate) reveal that addition of a diafiltration step has no effect on bHb purity or yield; however, it does increase the methemoglobin level and oxygen affinity of purified bHb. Therefore, we conclude that no additional benefit is gained from diafiltration at stage III and a three stage TFF process is sufficient to produce HPLC-grade bHb.

Tangential flow filtration of hemoglobin

Bovine and human hemoglobin (bHb and hHb, respectively) was purified from bovine and human red blood cells via tangential flow filtration (TFF) in four successive stages. TFF is a fast and simple method to purify Hb from RBCs using filtration through hollow fiber (HF) membranes. Most of the Hb was retained in stage III (100 kDa HF membrane) and displayed methemoglobin levels less than 1%, yielding final concentrations of 318 and 300 mg/mL for bHb and hHb, respectively. Purified Hb exhibited much lower endotoxin levels than their respective RBCs. The purity of Hb was initially assessed via SDS-PAGE, and showed tiny impurity bands for the stage III retentate. The oxygen affinity (P(50)) and cooperativity coefficient (n) were regressed from the measured oxygen-RBC/Hb equilibrium curves of RBCs and purified Hb. These results suggest that TFF yielded oxygen affinities of bHb and hHb that are comparable to values in the literature. LC-MS was used to measure the molecular weight of the alpha (alpha) and beta (beta) globin chains of purified Hb. No impurity peaks were present in the HPLC chromatograms of purified Hb. The mass of the molecular ions corresponding to the alpha and beta globin chains agreed well with the calculated theoretical mass of the alpha- and beta- globin chains. Taken together, our results demonstrate that HPLC-grade Hb can be generated via TFF. In general, this method can be more broadly applied to purify Hb from any source of RBCs. This work is significant, since it outlines a simple method for generating Hb for synthesis and/or formulation of Hb-based oxygen carriers.

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.

Preparation of ultrapure bovine and human hemoglobin by anion exchange chromatography

Bovine and human hemoglobin (Hb) form the basis for many different types of Hb-based O(2) carriers (HBOCs) ranging from chemically modified Hbs to particle encapsulated Hbs. Hence, the development of a facile purification method for preparing ultrapure Hb is essential for the reliable synthesis and formulation of HBOCs. In this work, we describe a simple process for purifying ultrapure solutions of bovine and human Hb. Bovine and human red blood cells (RBCs) were lyzed, and Hb was purified from the cell lysate by anion exchange chromatography. The initial purity of Hb fractions was analyzed by SDS-PAGE. Pure Hb fractions (corresponding to a single band on the SDS-PAGE gel) were pooled together and the overall purity and identity assessed by LC-MS. LC-MS analysis yielded two peaks corresponding to the calculated theoretical molecular weight of the alpha and beta chains of Hb. The activity of HPLC pure Hb was assessed by measuring its oxygen affinity, cooperativity and methemoglobin level. These measures of activity were comparable to values in the literature. Taken together, our results demonstrate that ultrapure Hb (electrophoresis and HPLC pure) can be easily prepared via anion exchange chromatography. In general, this method can be more broadly applied to purify hemoglobin from any source of RBC. This work is significant, since it outlines a simple method for generating ultrapure Hb for synthesis and/or formulation of HBOCs.