Hemoglobin-based oxygen carrier microparticles: synthesis, properties, and in vitro and in vivo investigations

Controllable synthesis of barium carbonate nano- and microparticles for SPECT and CT imaging

The design and synthesis of nano- and microcarriers for preclinical and clinical imaging are highly attractive due to their unique features, for example, multimodal properties. However, broad translation of these carriers into clinical practice is postponed due to the unknown biological reactivity of the new components used for their synthesis. Here, we have developed microcarriers (∼2-3 μm) and  nanocarriers (<200 nm) made of barium carbonate (BaCO3) for multiple imaging applications in vivo. In general, barium in the developed carriers can be used for X-ray computed tomography, and the introduction of a diagnostic isotope (99mTc) into the BaCO3 structure enables in vivo visualization using single-photon emission computed tomography. The bioimaging has shown that the radiolabeled BaCO3 nano- and microcarriers had different biodistribution profiles and tumor accumulation efficiencies after intratumoral and intravenous injections. In particular, in the case of intratumoral injection, all the types of used carriers mostly remained in the tumors (>97%). For intravenous injection, BaCO3 microcarriers were mainly localized in the lung tissues. However, BaCO3 NPs were mainly accumulated in the liver. These results were supported by ex vivo fluorescence imaging, direct radiometry, and histological analysis. The BaCO3-based micro- and nanocarriers showed negligible in vivo toxicity towards major organs such as the heart, lungs, liver, kidneys, and spleen. This study provides a simple strategy for the design and fabrication of the BaCO3-based carriers for the development of dual bioimaging.

Development of novel polymer haemoglobin based particles as an antioxidant, antibacterial and an oxygen carrier agents

This innovative work aims to develop highly biocompatible and degradable nanoparticles by encapsulating haemoglobin (Hb) within poly-ε-caprolactone for novel biomedical applications. We used a modified double emulsion solvent evaporation method to fabricate the particles. A Scanning electron microscope (SEM) characterized them for surface morphology. Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-visible spectroscopies (UV-visible) elucidated preserved chemical and biological structure of encapsulated haemoglobin. The airproof equilibrium apparatus obtained the oxygen-carrying capacity and P50 values. The DPPH assay assessed free radical scavenging potential. The antibacterial properties were observed using four different bacterial strains by disk diffusion method. The MTT assay investigates the cytotoxic effects on mouse fibroblast cultured cell lines (L-929). The MTT assay showed that nanoparticles have no toxicity over large concentrations. The well-preserved structure of Hb within particles, no toxicity, high oxygen affinity, P50 value, and IC50 values open the area of new research, which may be used as artificial oxygen carriers, antioxidant, and antibacterial agents, potential therapeutic agents as well as drug carrier particles to treat the cancerous cells. The novelty of this work is the antioxidant and antibacterial properties of developed nanoparticles are not been reported yet. Results showed that the prepared particles have strong antioxidant and antibacterial potential.

Curcumin-loaded albumin submicron particles with potential as a cancer therapy: an in vitro study

Curcumin (CUR), a polyphenolic compound, shows promising biological properties, particularly antioxidant activity. However, its medical applications are limited due to its low water solubility, bioavailability, and pH-instability. CUR-loaded albumin microparticles (CUR-HSA-MPs) of submicron size in the range of 800 to 900 nm and a zeta potential of -15 mV were prepared. The CUR loading efficiency was up to 65%. A maximum release of 37% of the encapsulated CUR was observed within 6 h when the CUR-HSA-MPs were dispersed in 50% ethanol in PBS at pH 7, while in RPMI 1640 medium the release was 7%. This demonstrates a sustainable release. The in vitro cytotoxicity of CUR-HSA-MPs showed promising anticancer potential against human hepatocellular carcinoma (Huh-7) and human breast adenocarcinoma (MCF-7) cell lines, although this effect was less pronounced in human dermal fibroblasts (HDFB) and human cholangiocyte (MMN) cell lines. Confocal microscopy was used to confirm the uptake of CUR-HSA-MPs by cancer cells. Our studies revealed that HSA-MPs are potentially promising vehicles for increasing the solubility and bioavailability of CUR.

Recognition mechanisms of hemoglobin particles by monocytes - CD163 may just be one

Hemoglobin-based oxygen carriers (HBOCs) as blood substitutes are one of the great hopes of modern transfusion and emergency medicine. After the major safety-relevant challenges of the last decades seem to be largely overcome, current developments have in common that they are affected by degradation and excretion at an early stage in test organisms. Several possible mechanisms that may be responsible for this are discussed in the literature. One of them is CD163, the receptor of the complex of haptoglobin (Hp) and hemoglobin (Hb). The receptor has been shown in various studies to have a direct affinity for Hb in the absence of Hp. Thus, it seems reasonable that CD163 could possibly also bind Hb within HBOCs and cause phagocytosis of the particles. In this work we investigated the role of CD163 in the uptake of our hemoglobin sub-micron particles (HbMPs) in monocytes and additionally screened for alternative ways of particle recognition by monocytes. In our experiments, blockade of CD163 by specific monoclonal antibodies proved to partly inhibit HbMP uptake by monocytes. It appears, however, that several other phagocytosis pathways for HbMPs might exist, independent of CD163 and also Hb.

Structural optimization and prospect of constructing hemoglobin oxygen carriers based on hemoglobin

The current global shortage of organ resources, the imbalance in donor-recipient demand and the increasing number of high-risk donors make organ preservation a necessity to consider appropriate storage options. The current method of use often has risks such as blood group mismatch, short shelf life, and susceptibility. HBOCs have positive effects such as anti-apoptotic, anti-inflammatory, antioxidant and anti-proliferative, which have significant advantages in organ storage. Therefore, it is the common pursuit of researchers to design and synthesize HBOCs with safety, ideal oxygen-carrying capacity, easy storage, etc. that are widely applicable and optimal for different organs. There has been a recent advancement in understanding HBOCs mechanisms, which is discussed in this review.

Recent advances in micro-sized oxygen carriers inspired by red blood cells

Supplementing sufficient oxygen to cells is always challenging in biomedical engineering fields such as tissue engineering. Originating from the concept of a 'blood substitute', nano-sized artificial oxygen carriers (AOCs) have been studied for a long time for the optimization of the oxygen supplementation and improvement of hypoxia environments in vitro and in vivo. When circulating in our bodies, micro-sized human red blood cells (hRBCs) feature a high oxygen capacity, a unique biconcave shape, biomechanical and rheological properties, and low frictional surfaces, making them efficient natural oxygen carriers. Inspired by hRBCs, recent studies have focused on evolving different AOCs into microparticles more feasibly able to achieve desired architectures and morphologies and to obtain the corresponding advantages. Recent micro-sized AOCs have been developed into additional categories based on their principal oxygen-carrying or oxygen-releasing materials. Various biomaterials such as lipids, proteins, and polymers have also been used to prepare oxygen carriers owing to their rapid oxygen transfer, high oxygen capacity, excellent colloidal stability, biocompatibility, suitable biodegradability, and long storage. In this review, we concentrated on the fabrication techniques, applied biomaterials, and design considerations of micro-sized AOCs to illustrate the advances in their performances. We also compared certain recent micro-sized AOCs with hRBCs where applicable and appropriate. Furthermore, we discussed existing and potential applications of different types of micro-sized AOCs.

Functionalized protein microparticles targeting hACE2 as a novel preventive strategy for SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2), resulting in a serious burden on public health and social economy worldwide. SARS-CoV-2 infection is mainly initialized in the nasopharyngeal cavity through the binding of viral spike (S) protein to human angiotensin-converting enzyme 2 (hACE2) receptors which are widely expressed in many human cells. Thus, blockade of the interaction between viral S protein and hACE2 receptor in the primary entry site is a promising prevention strategy for the management of COVID-19. Here we showed protein microparticles (PMPs) decorated with hACE2 could bind and neutralize SARS-CoV-2 S protein-expressing pseudovirus (PSV) and protect host cells from infection in vitro. In the hACE2 transgenic mouse model, administration of intranasal spray with hACE2-decorated PMPs markedly decreased the viral load of SARS-CoV-2 in the lungs though the inflammation was not attenuated significantly. Our results provided evidence for developing functionalized PMPs as a potential strategy for preventing emerging air-borne infectious pathogens, such as SARS-CoV-2 infection.

Tumor Cell Capture Using Platelet-Based and Platelet-Mimicking Modified Human Serum Albumin Submicron Particles

The co-localization of platelets and tumor cells in hematogenous metastases has long been recognized. Interactions between platelets and circulating tumor cells (CTCs) contribute to tumor cell survival and migration via the vasculature into other tissues. Taking advantage of the interactions between platelets and tumor cells, two schemes, direct and indirect, were proposed to target the modified human serum albumin submicron particles (HSA-MPs) towards tumor cells. HSA-MPs were constructed by the Co-precipitation-Crosslinking-Dissolution (CCD) method. The anti-CD41 antibody or CD62P protein was linked to the HSA-MPs separately via 1-ethyl-3-(-3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) EDC/NHS chemistry. The size of modified HSA-MPs was measured at approximately 1 µm, and the zeta potential was around -24 mV. Anti-CD41-HSA-MPs adhered to platelets as shown by flowcytometry and confocal laser scanning microscopy. In vitro, we confirmed the adhesion of platelets to tumor lung carcinoma cells A549 under shearing conditions. Higher cellular uptake of anti-CD41-HSA-MPs in A549 cells was found in the presence of activated platelets, suggesting that activated platelets can mediate the uptake of these particles. RNA-seq data in the Cancer Cell Lineage Encyclopedia (CCLE) and The Cancer Genome Atlas (TCGA) database showed the expression of CD62P ligands in different types of cancers. Compared to the non-targeted system, CD62P-HSA-MPs were found to have higher cellular uptake in A549 cells. Our results suggest that the platelet-based and platelet-mimicking modified HSA-MPs could be promising options for tracking metastatic cancer.

Calcium carbonate carriers for combined chemo- and radionuclide therapy of metastatic lung cancer

Considering the clinical limitations of individual approaches against metastatic lung cancer, the use of combined therapy can potentially improve the therapeutic effect of treatment. However, determination of the appropriate strategy of combined treatment can be challenging. In this study, combined chemo- and radionuclide therapy has been realized using radionuclide carriers (¹⁷⁷Lu-labeled core-shell particles, ¹⁷⁷Lu-MPs) and chemotherapeutic drug (cisplatin, CDDP) for treatment of lung metastatic cancer. The developed core-shell particles can be effectively loaded with ¹⁷⁷Lu therapeutic radionuclide and exhibit good radiochemical stability for a prolonged period of time. In vivo biodistribution experiments have demonstrated the accumulation of the developed carriers predominantly in lungs. Direct radiometry analysis did not reveal an increased absorbance of radiation by healthy organs. It has been shown that the radionuclide therapy with ¹⁷⁷Lu-MPs in mono-regime is able to inhibit the number of metastatic nodules (untreated mice = 120 ± 12 versus¹⁷⁷Lu-MPs = 50 ± 7). The combination of chemo- and radionuclide therapy when using ¹⁷⁷Lu-MPs and CDDP further enhanced the therapeutic efficiency of tumor treatment compared to the single therapy (¹⁷⁷Lu-MPs = 50 ± 7 and CDDP = 65 ± 10 versus¹⁷⁷Lu-MPs + CDDP = 37 ± 5). Thus, this work is a systematic research on the applicability of the combination of chemo- and radionuclide therapy to treat metastatic lung cancer.

Bacterial safety study of the production process of hemoglobin-based oxygen carriers

Hemoglobin microparticles (HbMP) produced with a three-step procedure, including coprecipitation of hemoglobin with manganese carbonate, protein cross-linking, and dissolution of the carbonate template were shown to be suitable for application as artificial oxygen carriers. First preclinical safety investigations delivered promising results. Bacterial safety plays a decisive role during the production of HbMP. Therefore, the bioburden and endotoxin content of the starting materials (especially hemoglobin) and the final particle suspension are intensively tested. However, some bacteria may not be detected by standard tests due to low concentration. The aim of this study was to investigate how these bacteria would behave in the fabrication process. Biocidal effects are known for glutaraldehyde and for ethylenediaminetetraacetic acid, chemicals that are used in the fabrication process of HbMP. It was shown that both chemicals prevent bacterial growth at the concentrations used during HbMP fabrication. In addition, the particle production was carried out with hemoglobin solutions spiked with Escherichia coli or Staphylococcus epidermidis. No living bacteria could be detected in the final particle suspensions. Therefore, we conclude that the HbMP fabrication procedure is safe in respect of bacterial contamination.

Oxygenation therapies for improved wound healing: Current trends and technologies

Degree of oxygenation is one of the important parameters governing various processes, including cell proliferation, angiogenesis, extracellular matrix production, and even combating the microbial burden at the wound site, all...

Modulation of Functional Characteristics of Mesenchymal Stromal Cells by Acellular Preparation of Porcine Hemoglobin

Exploring the potential usage of the acellular preparation of porcine hemoglobin (PHb) isolated from slaughterhouse blood as a cell culture media component, we have tested its effects on the functional characteristics of stromal cells of mesodermal origin. Human peripheral blood mesenchymal stromal cells (PB-MSCs) were used in this study as a primary cell model system, along with three mouse cell lines (ATDC5, MC3T3-E1, and 3T3-L1), which represent more uniform model systems. We investigated the effect of PHb at concentrations of 0.1, 1, and 10 μM on these cells’ proliferation, cycle, and clonogenic and migratory potential, and found that PHb’s effect depended on both the cell type and its concentration. At the lowest concentration used (0.1 μM), PHb showed the least evident impact on the cell growth and migration; hence, we analyzed its effect on mesenchymal cell multilineage differentiation capacity at this concentration. Even under conditions that induce a specific type of MSC differentiation (cultivation in particular differentiation media), PHb modulated chondrogenic, osteogenic, and adipogenic differentiation, making it a potential candidate for a supplement of MSC culture. Through a model of porcine hemoglobin, these findings also contribute to improving the knowledge of extracellular hemoglobin’s influence on MSCs >in vivo.

Synthesis and characterization of enzymatically active micrometer protein-capsules

This work describes a general method for the encapsulation of enzymes with albumin as wall material and the enzyme catalase as prime example. Care was taken for the preparation of biochemically active sub-micrometer particles in order to prevent oxygen toxicity induced by artificial oxygen carriers of any type. In cell culture experiments, capsules containing catalase did not exhibit any harmful activities in the absence of peroxides. In the presence of hydrogen peroxide application of low and medium dosed capsules below 0.05 vol% (final concentration 0.001 vol%) even increased the cell damaging process. However, a higher dosage of capsules (>0.05 vol%) prevented completely cellular disruption induced by 5 mM hydrogen peroxide and decreased up to 90% of cellular damage at higher peroxide concentrations. These results demonstrated that encapsulated catalase was enzymatically active and the over-all activity of prepared catalase capsules was determined to be >1900 U mL-1 vol%-1.

Hemoglobin-Inorganic Hybrid Nanoflowers with Different Metal Ions as Potential Oxygen Carrying Systems

Protein-inorganic hybrid nanoflowers have tremendous potential in bionanotechnology due to their simple method of preparation, high stability and superior properties. Considering these features, the present study was designed to investigate the artificial blood substitution potentials of hemoglobin-inorganic hybrid nanoflowers. In this context, hemoglobin-inorganic hybrid nanoflowers (Cu-NF, Co-NF and Zn-NF) were synthesized using with different metal ions (copper, cobalt and zinc), then their oxygen carrying capacity, the hemolytic studies, in vitro oxidant/antioxidant capacity levels and oxidative stress index were reported for the first time. The present findings have revealed that Zn-NF had significant oxygen content and artificial oxygen carriers (AOC), as well as a significantly low percent hemolysis rate and a safe standard value. Also, hemolysis rate decreased along with the increases in hemoglobin content coupled with increments in nanoflower concentrations. The percentage hemolysis rate was lower than all nanoflowers at low free hemoglobin concentration, but hemolysis rates also increased with increments in concentration. The results showed that in general, Zn-NF stands out with its high total antioxidant capacity and low total oxidant capacity and oxidative stress index. The obtained results showed that Cu-NF and Co-NF, especially Zn-NF might be considered as a potential superior artificial oxygen carrier. Therefore, this nanoflower system might be act as an efficient material as a blood substitute in the near future.

Synthesis of Nanoparticles Fully Made of Hemoglobin with Antioxidant Properties: A Step toward the Creation of Successful Oxygen Carriers

Transfusion of donor red blood cells (RBCs) is a crucial and widely employed clinical procedure. However, important constraints of blood transfusions include the limited availability of blood, the need for typing and cross-matching due to the RBC membrane antigens, the limited storage lifetime, or the risk for disease transmission. Hence, a lot of effort has been devoted to develop RBC substitutes, which are free from the limitations of donor blood. Despite the potential, the creation of hemoglobin (Hb)-based oxygen carriers is still facing important challenges. To allow for proper tissue oxygenation, it is essential to develop carriers with high Hb loading since Hb comprises about 96% of the RBCs' dry weight. In this work, nanoparticles (NPs) fully made of Hb are prepared by the desolvation precipitation method. Several parameters are screened (i.e., Hb concentration, desolvation ratio, time, and sonication intensity) to finally obtain Hb-NPs with a diameter of ∼568 nm and a polydispersity index (PDI) of 0.2. A polydopamine (PDA) coating is adsorbed to prevent the disintegration of the resulting Hb/PDA-NPs. Due to the antioxidant character of PDA, the Hb/PDA-NPs are able to deplete two harmful reactive oxygen species, namely, the superoxide radical anion and hydrogen peroxide. Such antioxidant protection also translates into minimizing the oxidation of the entrapped Hb to nonfunctional methemoglobin (metHb). This is a crucial aspect since metHb conversion also results in inflammatory reactions and dysregulated vascular tone. Finally, yet importantly, the reported Hb/PDA-NPs are also both hemo- and biocompatible and preserve the reversible oxygen-binding and releasing properties of Hb.

Biopolymer-Based Multilayer Capsules and Beads Made via Templating: Advantages, Hurdles and Perspectives

One of the undeniable trends in modern bioengineering and nanotechnology is the use of various biomolecules, primarily of a polymeric nature, for the design and formulation of novel functional materials for controlled and targeted drug delivery, bioimaging and theranostics, tissue engineering, and other bioapplications. Biocompatibility, biodegradability, the possibility of replicating natural cellular microenvironments, and the minimal toxicity typical of biogenic polymers are features that have secured a growing interest in them as the building blocks for biomaterials of the fourth generation. Many recent studies showed the promise of the hard-templating approach for the fabrication of nano- and microparticles utilizing biopolymers. This review covers these studies, bringing together up-to-date knowledge on biopolymer-based multilayer capsules and beads, critically assessing the progress made in this field of research, and outlining the current challenges and perspectives of these architectures. According to the classification of the templates, the review sequentially considers biopolymer structures templated on non-porous particles, porous particles, and crystal drugs. Opportunities for the functionalization of biopolymer-based capsules to tailor them toward specific bioapplications is highlighted in a separate section.

Preparation of Artificial Red Blood Cells (Hemoglobin Vesicles) Using the Rotation-Revolution Mixer for High Encapsulation Efficiency

Hemoglobin vesicles (Hb-V) are artificial red blood cells encapsulating highly concentrated hemoglobin (Hb) in liposomes comprising phospholipids, cholesterol, negatively charged lipids, and polyethylene glycol (PEG)-conjugated phospholipids. Safety and efficacy of Hb-V as a transfusion alternative have been extensively studied. For this study, we prepared Hb-V using the kneading method with a rotation-revolution mixer as an alternative to the conventional extrusion method. We optimized the kneading operation parameters to obtain Hb-V with a high yield. Results show that the Hb encapsulation efficiency was increased dramatically up to 74.2%, which is higher than that of the extrusion method (20%) because the kneading method enabled mixing of a highly concentrated carbonylhemoglobin (HbCO) solution (40 g/dL) and a considerably large amount of powdered lipids in only 10 min. The high viscosity of the Hb-lipid mixture paste (ca. 10³-10⁵ cP) favorably induces frictional heat by kneading and increases the paste temperature (ca. 60 °C), which facilitates lipid dispersion and liposome formation. During the kneading operation using a thermostable HbCO solution, Hb denaturation was prevented. Hb-V prepared using this method showed no marked changes in particle sizes, Hb denaturation, or Hb leakage from liposomes during two years of long-term storage-stability tests. Collectively, these results demonstrate that the kneading method using a rotation-revolution mixer shows good potential as a new method to produce Hb-V.

Entropy-Driven Supramolecular Ring-Opening Polymerization of a Cyclic Hemoglobin Monomer for Constructing a Hemoglobin-PEG Alternating Polymer with Structural Regularity

Our earlier report described that a cyclic hemoglobin (Hb) monomer with two β subunits of a Hb molecule (α₂β₂) bound through a flexible polyethylene glycol (PEG) chain undergoes reversible supramolecular ring-opening polymerization (S-ROP) to produce a supramolecular Hb polymer with a Hb-PEG alternating structure. In this work, we polymerized cyclic Hb monomers with different ring sizes (2, 5, 10, or 20 kDa PEG) to evaluate the thermodynamics of S-ROP equilibrium. Quantification of the produced supramolecular Hb polymers and the remaining cyclic Hb monomers in the equilibrium state revealed a negligibly small enthalpy change in S-ROP (ΔH_p ≤ 1 kJ·mol^-1) and a markedly positive entropy change increasing with the ring size (ΔS_p = 26.8-33.2 J·mol^-1·K^-1). The results suggest an entropy-driven mechanism in S-ROP: a cyclic Hb monomer with the larger ring size prefers to form a supramolecular Hb polymer. The S-ROP used for this study has the potential to construct submicrometer-sized Hb-PEG alternating polymers having structural regularity.

Function of Hemoglobin-Based Oxygen Carriers: Determination of Methemoglobin Content by Spectral Extinction Measurements

Suspensions of hemoglobin microparticles (HbMPs) are promising tools as oxygen therapeutics. For the approval of clinical studies extensive characterization of these HbMPs with a size of about 750 nm is required regarding physical properties, function, pharmaco-kinetics and toxicology. The standard absorbance measurements in blood gas analyzers require dissolution of red blood cells which does not work for HbMP. Therefore, we have developed a robust and rapid optical method for the quality and functionality control of HbMPs. It allows simultaneous determination of the portion of the two states of hemoglobin oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) as well as the content of methemoglobin (metHb). Based on the measurement of collimated transmission spectra between 300 nm and 800 nm, the average extinction cross section of HbMPs is derived. A numerical method is applied to determine the composition of the HbMPs based on their wavelength-dependent refractive index (RI), which is a superposition of the three different states of Hb. Thus, light-scattering properties, including extinction cross sections can be simulated for different compositions and sizes. By comparison to measured spectra, the relative concentrations of oxyHb, deoxyHb, metHb are accessible. For validation of the optically determined composition of the HbMPs, we used X-ray fluorescence spectrometry for the ratio of Fe(II) (oxyHb/deoxyHb) and Fe(III) (metHb). High accuracy density measurements served to access heme-free proteins, size was determined by dynamic light scattering and analytical centrifugation and the shape of the HbMPs was visualized by electron and atomic force microscopy.

Oxygen releasing materials: Towards addressing the hypoxia-related issues in tissue engineering

Manufacturing macroscale cell-laden architectures is one of the biggest challenges faced nowadays in the domain of tissue engineering. Such living constructs, in fact, pose strict requirements for nutrients and oxygen supply that can hardly be addressed through simple diffusion in vitro or without a functional vasculature in vivo. In this context, in the last two decades, a substantial amount of work has been carried out to develop smart materials that could actively provide oxygen-release to contrast local hypoxia in large-size constructs. This review provides an overview of the currently available oxygen-releasing materials and their synthesis and mechanism of action, highlighting their capacities under in vitro tissue cultures and in vivo contexts. Additionally, we also showcase an emerging concept, herein termed as "living materials as releasing systems", which relies on the combination of biomaterials with photosynthetic microorganisms, namely algae, in an "unconventional" attempt to supply the damaged or re-growing tissue with the necessary supply of oxygen. We envision that future advances focusing on tissue microenvironment regulated oxygen-supplying materials would unlock an untapped potential for generating a repertoire of anatomic scale, living constructs with improved cell survival, guided differentiation, and tissue-specific biofunctionality.

Fabrication and Characterization of Human Serum Albumin Particles Loaded with Non-Sericin Extract Obtained from Silk Cocoon as a Carrier System for Hydrophobic Substances

Non-sericin (NS) extract was produced from the ethanolic extract of Bombyx mori silk cocoons. This extract is composed of both carotenoids and flavonoids. Many of these compounds are composed of substances of poor aqueous solubility. Thus, this study focused on the development of a carrier system created from biocompatible and biodegradable materials to improve the biological activity of NS extracts. Accordingly, NS was incorporated into human serum albumin template particles with MnCO₃ (NS-HSA MPs) by loading NS into the preformed HAS-MnCO₃ microparticles using the coprecipitation crosslinking dissolution technique (CCD-technique). After crosslinking and template dissolution steps, the NS loaded HSA particles are negatively charged, have a size ranging from 0.8 to 0.9 µm, and are peanut shaped. The degree of encapsulation efficiency ranged from 7% to 57% depending on the initial NS concentration and the steps of adsorption. In addition, NS-HSA MPs were taken up by human lung adenocarcinoma (A549 cell) for 24 h. The promotion of cellular uptake was evaluated by flow cytometry and the results produced 99% fluorescent stained cells. Moreover, the results from CLSM and 3D fluorescence imaging confirmed particle localization in the cells. Interestingly, NS-HSA MPs could not induce inflammation through nitric oxide production from macrophage RAW264.7 cells. This is the first study involving the loading of non-sericin extracts into HSA MPs by CCD technique to enhance the bioavailability and biological effects of NS. Therefore, HSA MPs could be utilized as a carrier system for hydrophobic substances targeting cells with albumin receptors.

Dynamic blood flow phantom for in vivo liquid biopsy standardization

In vivo liquid biopsy, especially using the photoacoustic (PA) method, demonstrated high clinical potential for early diagnosis of deadly diseases such as cancer, infections, and cardiovascular disorders through the detection of rare circulating tumor cells (CTCs), bacteria, and clots in the blood background. However, little progress has been made in terms of standardization of these techniques, which is crucial to validate their high sensitivity, accuracy, and reproducibility. In the present study, we addressed this important demand by introducing a dynamic blood vessel phantom with flowing mimic normal and abnormal cells. The light transparent silica microspheres were used as white blood cells and platelets phantoms, while hollow polymeric capsules, filled with hemoglobin and melanin, reproduced red blood cells and melanoma CTCs, respectively. These phantoms were successfully used for calibration of the PA flow cytometry platform with high-speed signal processing. The results suggest that these dynamic cell flow phantoms with appropriate biochemical, optical, thermal, and acoustic properties can be promising for the establishment of standardization tool for calibration of PA, fluorescent, Raman, and other detection methods of in vivo flow cytometry and liquid biopsy.

Cooling-Triggered Release from Mesoporous Poly(N-isopropylacrylamide) Microgels at Physiological Conditions

Poly(N-isopropylacrylamide) (pNIPAM) hydrogels have broad potential applications as drug delivery vehicles because of their thermoresponsive behavior. pNIPAM loading/release performances are directly affected by the gel network structure. Therefore, there is a need with the approaches for accurate design of 3D pNIPAM assemblies with the structure ordered at the nanoscale. This study demonstrates size-selective spontaneous loading of macromolecules (dextrans 10-500 kDa) into pNIPAM microgels by microgel heating from 22 to 35 °C (microgels collapse and trap dextrans) followed by the dextran release upon further cooling down to 22 °C (microgels swell back) . This temperature-mediated behavior is fully reversible. The structure of pNIPAM microgels was tailored via hard templating and cross-linking of the hydrogel using sacrificial mesoporous cores of vaterite CaCO3 microcrystals. In addition, the fabrication of hollow thermoresponsive pNIPAM microshells has been demonstrated, utilizing vaterite microcrystals that had narrower pores. The proposed approach for heating-triggered encapsulation and cooling-triggered release into/from pNIPAM microgels may pave the ways for applications of pNIPAM hydrogels for skin and transdermal cooling-responsive drug delivery in the future.

Determination of Methemoglobin in Hemoglobin Submicron Particles Using NMR Relaxometry

Methemoglobin (MetHb) is a hemoglobin (Hb) derivative with the heme iron in ferric state (Fe³⁺), unable to deliver oxygen. Quantification of methemoglobin is a very important diagnostic parameter in hypoxia. Recently, novel hemoglobin microparticles (Hb-MP) with a narrow size distribution around 700 nm, consisting of cross-linked Hb were proposed as artificial oxygen carriers. The cross-linking of Hb by glutaraldehyde (GA) generates a certain amount of MetHb. Due to the strong light scattering, quantitative determination of MetHb in Hb-MP suspensions by common spectrophotometry is not possible. Here, we demonstrate that ¹H₂O NMR relaxometry is a perfect tool for direct measurement of total Hb and MetHb concentrations in Hb-MP samples. The longitudinal relaxation rate 1/T₁ shows a linear increase with increasing MetHb concentration, whereas the transverse relaxation rate 1/T₂ linearly increases with the total Hb concentration. In both linear regressions the determination coefficient (R²) is higher than 0.99. The method does not require time-consuming pretreatment or digestion of the particles and is not impaired by light scattering. Therefore, it can be established as the method of choice for the quality control of Hb-MP and similar hemoglobin-based oxygen carriers in the future.

Künstliche Sauerstofftransporter können mehr als Sauerstoff liefern

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

Development of novel oxygen carriers by coupling hemoglobin to functionalized multiwall carbon nanotubes

Preparation of stable and effective artificial oxygen carriers (AOCs) is a promising strategy to temporarily replace transfused blood and solve tissue hypoxia. Developing hemoglobin (Hb) loaded particles is one of the main ways to prepare suitable AOCs. Particles with a hierarchical micro/nanostructure can be loaded with plenty of proteins and have attracted great attention. Therefore, multiwall carbon nanotubes (MWCNTs) were chosen to fabricate AOCs. To improve the Hb-loading capacity of MWCNTs, functionalized MWCNTs, including carboxyl-functionalized MWCNTs (MWCNT-COOH), amino-functionalized MWCNTs (MWCNT-NH2), and heparin-conjugated MWCNTs (MWCNT-Hep), were prepared. Then, in this study, Hb was coupled to the functionalized MWCNTs to fabricate the AOCs. The functionalized MWCNTs and the AOCs were characterized by FTIR, SEM, TEM, and zeta potential analysis. The oxygen/Hb-loading capacity of the AOCs was also measured. The adverse effects of the AOCs on human umbilical vein endothelial cells (HUVECs) and human red blood cells (RBCs) were evaluated. The results showed that (1) the functional groups were grafted on the surface of the MWCNTs, and Hb was bound to the functionalized MWCNTs, thus the AOCs were successfully prepared; (2) MWCNT-Hep-Hb had the most stable dispersibility (i.e., the most negative zeta potential) in 0.9 wt% NaCl solution (MWCNT-Hep-Hb < MWCNT-COOH-Hb < MWCNT-Hb < MWCNT-NH2-Hb < 0); (3) MWCNT-Hep had the best Hb-loading capability, which was three times that of purified MWCNTs; (4) with concentrations increased up to 400 μg mL-1, MWCNT-Hep-Hb still had the highest cell viability (97.63% > 80%, ISO 10993-5:2009) and excellent blood biocompatibility. Therefore, MWCNT-Hep-Hb might be a satisfactory candidate as a blood substitute.

Polydopamine-based surface modification of hemoglobin particles for stability enhancement of oxygen carriers

Templated assembly techniques have been extensively used to develop various types of hemoglobin (Hb) loaded particles with improved performance. However, several instability issues must still be solved, including Hb exposure, enhanced Hb auto-oxidation, and the relatively weak binding of Hb to cross-linkers. Herein, to meet the stability requirements for novel hemoglobin-based oxygen carriers (HBOCs), hemoglobin-polydopamine particles (Hb-PDA) were fabricated using a mild process that combines the co-precipitation of Hb and an inorganic template with the spontaneous adhesion of PDA. The Hb-PDA showed uniform size distribution, chemical integrity of both Hb and PDA, high biocompatibility, and robust oxygen delivery. Our results demonstrated that the use of polydopamine as a biocompatible coating material reduced Hb leakage from the particles under both static and flow conditions, thus mitigating the toxicity associated with free Hb and strengthening the stability of Hb particles. In addition, Hb-PDA reduced HUVEC (Human Umbilical Vein Cells) oxidative injury and scavenged 85% of the available hydroxyl radicals, exhibiting its potential to act as an antioxidant for encapsulated Hb. Hb-PDA therefore shows significant promise as a cell-like structurally and functionally stable HBOCs.

Doxorubicin-Loaded Human Serum Albumin Submicron Particles: Preparation, Characterization and In Vitro Cellular Uptake

Doxorubicin (DOX) is an effective anthracycline antibiotic drug which is commonly used in a broad range cancer therapy. However, due to dose depending side effects and toxicity to non-cancerous tissues, its clinical applications are restricted. To overcome these limitations, human serum albumin (HSA) has been investigated as a biocompatible drug delivery vehicle. In this study, human serum albumin submicron particles (HSA-MPs) were fabricated by using the Co-precipitation–Crosslinking–Dissolution technique (CCD technique) and DOX was loaded into the protein particles by absorption. DOX-HSA-MPs showed uniform peanut-like shape, submicron size and negative zeta-potential (−13 mV). The DOX entrapment efficiency was 25% of the initial amount. The in vitro release in phosphate buffered saline pH 7.4 was less than 1% within 5 h. In contrast, up to 40% of the entrapped DOX was released in presence of a protein digesting enzyme mixture (Pronase^®) within the same time. In addition, in vitro cytotoxicity and cellular uptake of DOX-HSA-MPs were evaluated using the lung carcinoma cell line A549. The results demonstrated that DOX-HSA-MPs reduced the cell metabolic activities after 72 h. Interestingly, DOX-HSA-MPs were taken up by A549 cells up to 98% and localized in the cell lysosomal compartment. This study suggests that DOX-HSA-MPs which was fabricated by CCD technique is seen as a promising biopolymer particle as well as a viable alternative for drug delivery application to use for cancer therapy.

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).

Controlled Polymerization and Ultrafiltration Increase the Consistency of Polymerized Hemoglobin for Use as an Oxygen Carrier

Polymerized human hemoglobins (PolyhHbs) are a promising class of red blood cell substitute for use in transfusion medicine. Unfortunately, the application of the commonly used glutaraldehyde cross-linking chemistry to synthesize these materials results in a complex mixture of PolyhHb molecules with highly varied batch-to-batch consistency. We implemented a controlled method of gas exchange and reagent addition that results in a homogeneous PolyhHb product. A fully coupled tangential flow filtration system was used to purify and concentrate the synthesized PolyhHb molecules. This improved method of PolyhHb production could be used to more precisely control the size and reduce the polydispersity of PolyhHb molecules, with minimal effects on the resulting oxygen-carrying capability. In addition to these factors, we assessed how the hemoglobin scavenging protein haptoglobin (Hp) would interact with PolyhHb molecules of varying sizes and quarternary states. Our results indicated that T-state PolyhHbs may be more efficiently detoxified by Hp compared with R-state PolyhHb and unmodified Hb.

Red Blood Cell-Mimicking Micromotor for Active Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a promising cancer therapeutic strategy, which typically kills cancer cells through converting nontoxic oxygen into reactive oxygen species using photosensitizers (PSs). However, the existing PDTs are still limited by the tumor hypoxia and poor targeted accumulation of PSs. To address these challenges, we here report an acoustically powered and magnetically navigated red blood cell-mimicking (RBCM) micromotor capable of actively transporting oxygen and PS for enhanced PDT. The RBCM micromotors consist of biconcave RBC-shaped magnetic hemoglobin cores encapsulating PSs and natural RBC membrane shells. Upon exposure to an acoustic field, they are able to move in biological media at a speed of up to 56.5 μm s^-1 (28.2 body lengths s^-1). The direction of these RBCM micromotors can be navigated using an external magnetic field. Moreover, RBCM micromotors can not only avoid the serum fouling during the movement toward the targeted cancer cells but also possess considerable oxygen- and PS-carrying capacity. Such fuel-free RBCM micromotors provide a new approach for efficient and rapid active delivery of oxygen and PSs in a biofriendly manner for future PDT.

In-vitro haemocompatibility of dextran-protein submicron particles

Blood compatibility is a key requirement to fulfil for intravenous administration of drug and oxygen carrier system. Recently, we published the fabrication of oxidised-dextran (Odex)-crosslinked protein particles by one-pot formulation. In the current study we investigate the haemocompatibility of these Odex - particles including albumin particles (Odex-APs) and haemoglobin particles (Odex-HbMPs). Odex-APs and Odex-HbMPs have a submicron size ranged 800-1000 nm with peanut-like shape and a negative surface charge. In vitro haemocompatibility assays included haemolysis test, indirect phagocytosis test and platelet activation test in human blood. Odex-APs and Odex-HbMPs did not provoke any undesirable effects on the blood cells. Firstly, the ratio of haemolysis after contacted with Odex-crosslinked protein particles were less than 5% and therefore the particles may be considered non-haemolytic. Secondly, the incubation of leukocyte with Odex-APs/HbMPs did not influence the phagocytosis of leukocyte. We conclude that our particles are not recognized by monocytes or granulocytes. Finally, exposure of Odex-APs/HbMPs to platelets did not cause an activation of platelets. Additionally, Odex-HbMP/AP did not enhance or attenuate agonist-induced platelet activation. We conclude that Odex-crosslinked protein particles exhibit a very good haemocompatibility and represent highly promising carriers for drugs or oxygen.

Albumin Submicron Particles with Entrapped Riboflavin-Fabrication and Characterization

Although riboflavin (RF) belongs to the water-soluble vitamins of group B, its solubility is low. Therefore, the application of micro-formulations may help to overcome this limiting factor for the delivery of RF. In this study we immobilized RF in newly developed albumin submicron particles prepared using the Co-precipitation Crosslinking Dissolution technique (CCD-technique) of manganese chloride and sodium carbonate in the presence of human serum albumin (HSA) and RF. The resulting RF containing HSA particles (RF-HSA-MPs) showed a narrow size distribution in the range of 0.9 to 1 μm, uniform peanut-like morphology, and a zeta-potential of -15 mV. In vitro release studies represented biphasic release profiles of RF in a phosphate buffered saline (PBS) pH 7.4 and a cell culture medium (RPMI) 1640 medium over a prolonged period. Hemolysis, platelet activation, and phagocytosis assays revealed a good hemocompatibility of RF-HSA-MPs.

Antioxidative protection of haemoglobin microparticles (HbMPs) by PolyDopamine

Clinically applicable haemoglobin-based oxygen carriers (HBOCs) should neither induce immunological nor toxic reactions. Additionally, Hb should be protected against oxidation. In the absence of protective enzymes (superoxide dismutase (SOD) and catalase (CAT)) Hb is oxidized to MetHb and thus losing its function of oxygen delivery. Alternatively, polydopamine (PD), a scavenger of free radicals, could be used for Hb protection against oxidation Therefore, we synthetized HbMPs modified with PD. The content of functional haemoglobin in these PD-HbMPs was twice higher than that in the control HbMPs due to the protective antioxidant effect of PD. In addition, the PD-HbMPs exhibited a high scavenging activity of free radicals including H₂O₂ and excellent biocompatibility. In contrast to monomeric dopamine, which has been shown to produce toxic effects on neurons due to formation of H₂O₂, hydroxyl radicals and superoxide during the process of auto-oxidation, PD-HbMPs are not neurotoxic. Consequently, the results presented here suggest a great potential of PD-HbMPs as HBOCs.

Fabrication and evaluation of hemoglobin-based polydopamine microcapsules as oxygen carriers

Polydopamine-hemoglobin (PDA-Hb) microcapsules possess a high oxygen affinity and could bind and release oxygen reversibly as demonstrated by electrochemical methods.

Structure and properties of hybrid biopolymer particles fabricated by co-precipitation cross-linking dissolution procedure

The Co-precipitation Crosslinking Dissolution technique (CCD-technique) allows a few-steps fabrication of particles composed of different biopolymers and bioactive agents under mild conditions. Morphology and properties of the fabricated biopolymer particles depend on the fabrication conditions, the nature of the biopolymers and additives, but also on the choice of the inorganic templates for co-precipitation. Here, we investigate the influence of an acidic biopolymer, hyaluronic acid (HA), on the formation of particles from bovine hemoglobin and bovine serum albumin applying co-precipitation with CaCO₃ and MnCO₃. CaCO₃ templated biopolymer particles are almost spherical with particle size from 2 to 20 µm and protein entrapment efficiency from 13 to 77%. Presence of HA causes significant structural changes of the particles and decreasing protein entrapment efficiency. In contrast, MnCO₃ templated particles exhibit uniform peanut shape and submicron size with remarkably high protein entrapment efficiency of nearly 100%. Addition of HA has no influence on the protein entrapment efficiency or on morphology and size of the particles. These effects can be attributed to the strong interaction of Mn²⁺ with proteins and much weaker interaction with HA. Therefore, entrapment efficiency, size and structure of biopolymer particles can be optimized by varying the mineral templates and additives.

Bioinspired Polydopamine-Coated Hemoglobin as Potential Oxygen Carrier with Antioxidant Properties

Oxidative side reaction is one of the major factors hindering the development of hemoglobin-based oxygen carriers (HBOCs). To avoid the oxidative toxicity, we designed and synthesized polydopamine-coated hemoglobin (Hb-PDA) nanoparticles via simple one-step assemblage without any toxic reagent. Hb-PDA nanoparticles showed oxidative protection of Hb by inhibiting the generation of methemoglobin (MetHb) and ferryl (Fe IV) Hb, as well as excellent antioxidant properties by scavenging free radicals and reactive oxygen species (ROS). Interestingly, the scavenging rate of Hb-PDA nanoparticles for ABTS⁺ radical is at most 89%, while for DPPH radical it reaches 49%. In addition, Hb-PDA efficiently reduced the intracellular H₂O₂-induced ROS generation. Moreover, Hb-PDA nanoparticles exhibited high oxygen affinity, low effect on blood constituents, and low cytotoxicity. The results indicate that polydopamine-coated hemoglobin might be a promising approach for constructing novel oxygen carriers with the capacity to reduce oxidative side reaction.

"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.

Hemoglobin-Conjugated Gelatin Microsphere as a Smart Oxygen Releasing Biomaterial

In this study, a novel micrometric biomaterial acting as a cyclic oxygen releasing system is designed. Human hemoglobin (Hb) is conjugated to the surface of gelatin microspheres (GM) to produce gelatin hemoglobin oxygen depot (G-HbOD). G-HbOD is obtained by means of two different conjugation strategies. The degree of conjugation of GM surfaces in terms of free amino groups by using HPLC is first evaluated. By following the strategy A (G-HbOD_A), Hb is conjugated to GM by means of the formation of a polyurethane linker. In the strategy B (G-HbOD_B) the conjugation occurs via amide bound formation. Physical and morphological differences between G-HbOD_A and G-HbOD_B are investigated by means of Fourier Transform Infrared Spectroscopy (FTIR), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Differences in oxygen uptake/release kinetics are found depending on the conjugation strategy and it is proved that G-HbOD works under repeated cycles in microfluidic chip. Moreover, G-HbOD is also able to work as oxygen depot in the early stages of 3D cell cultures.