Optimization of Hemoglobin Encapsulation within PLGA Nanoparticles and Their Investigation as Potential Oxygen Carriers

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.

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.

Cefmetazole sodium as an allosteric effector that regulates the oxygen supply efficiency of adult hemoglobin

Allosteric effectors play an important role in regulating the oxygen supply efficiency of hemoglobin for blood storage and disease treatment. However, allosteric effectors that are approved by the US FDA are limited. In this study, cefmetazole sodium (CS) was found to bind adult hemoglobin (HbA) from FDA library (1338 compounds) using surface plasmon resonance imaging high-throughput screening. Using surface plasmon resonance (SPR), the interaction between CS and HbA was verified. The oxygen dissociation curve of HbA after CS interaction showed a significant increase in P50 and theoretical oxygen-release capacity. Acid-base sensitivity (SI) exhibited a decreasing trend, although not significantly different. An oxygen dissociation assay indicated that CS accelerated HbA deoxygenation. Microfluidic modulated spectroscopy showed that CS changed the ratio of the alpha-helix to the beta-sheet of HbA. Molecular docking suggested CS bound to HbA's β-chains via hydrogen bonds, with key amino acids being N282, K225, H545, K625, K675, and V544.The results of molecular dynamics simulations (MD) revealed a stable orientation of the HbA-CS complex. CS did not significantly affect the P50 of bovine hemoglobin, possibly due to the lack of Valβ1 and Hisβ2, indicating that these were the crucial amino acids involved in HbA's oxygen affinity. Competition between the 2,3-Diphosphoglycerate (2,3-DPG) and CS in the HbA interaction was also determined by SPR, molecular docking and MD. In summary, CS could interact with HbA and regulate the oxygen supply efficiency via forming stable hydrogen bonds with the β-chains of HbA, and showed competition with 2,3-DPG.Communicated by Ramaswamy H. Sarma.

Metal-organic framework-based oxygen carriers with antioxidant activity resulting from the incorporation of gold nanozymes

Blood transfusions are a life-saving procedure since they can preserve the body's oxygen levels in patients suffering from acute trauma, undergoing surgery, receiving chemotherapy or affected by severe blood disorders. Due to the central role of hemoglobin (Hb) in oxygen transport, so-called Hb-based oxygen carriers (HBOCs) are currently being developed for situations where donor blood is not available. In this context, an important challenge that needs to be addressed is the oxidation of Hb into methemoglobin (metHb), which is unable to bind and release oxygen. While several research groups have considered the incorporation of antioxidant enzymes to create HBOCs with minimal metHb conversion, the use of biological enzymes has important limitations related to their high cost, potential immunogenicity or low stability in vivo. Thus, nanomaterials with enzyme-like properties (i.e., nanozymes (NZs)) have emerged as a promising alternative. Amongst the different NZs, gold (Au)-based metallic nanoparticles are widely used for biomedical applications due to their biocompatibility and multi-enzyme mimicking abilities. Thus, in this work, we incorporate Au-based NZs into a type of HBOC previously reported by our group (i.e., Hb-loaded metal-organic framework (MOF)-based nanocarriers (NCs)) and investigate their antioxidant properties. Specifically, we prepare MOF-NCs loaded with Au-based NZs and demonstrate their ability to catalytically deplete over multiple rounds of two prominent reactive oxygen species (ROS) that exacerbate Hb's autoxidation (i.e., hydrogen peroxide and the superoxide radical). Importantly, following loading with Hb, we show how these ROS-scavenging properties translate into a decrease in metHb content. All in all, these results highlight the potential of NZs to create novel HBOCs with antioxidant protection which may find applications as a blood substitute in the future.

Potential role of blood constituents in pain-relief associated with fibromyalgia treatment with extremely low magnetic field: Spectroscopic investigation

Magnetic field is used as an adjunct therapy for pain control and relief of musculoskeletal pain conditions as Fibromyalgia. It is regarded as more natural and less harmful alternative to analgesic compounds. The exact mechanism underlying these positive effects is still to be determined. Twenty-three patients diagnosed with Fibromyalgia condition were included in this study, and subjected to extremely low magnetic field treatment sessions. The treatment protocol based on exposing patients to gradually increased magnetic field strength that starts with 0.1 μT at the beginning, and increased gradually to 100 μT (3.33 μT/min). UV-Visible, mid-IR and fluorescence characteristics of whole blood, erythrocytes and hemoglobin were investigated; in addition to RBCs-osmotic fragility measurements. The obtained results were analyzed according to control-sham exposed patients. We observed marked changes in the blood (and/or its constituents) absorption spectra of fibromyalgia patients that indicate an enhancement in the energetic pathways and increased hemoglobin-oxygen affinity; in addition, the osmotic fragility measurements show that erythrocytes were characterized by increased elasticity and rehydration. The analyses of infrared spectra show that magnetic field treatment was associated with changes in the erythrocytes skeleton where α-helix component of protein secondary structure is dominant. This study provides scientific evidence that pain relief associated with extremely low magnetic field treatment can be directly related to its systemic effects as well as the enhancement of the cellular activities.

Research of storable and ready-to-use artificial red blood cells (hemoglobin vesicles) for emergency medicine and other clinical applications

Hemoglobin (Hb) is the most abundant protein in blood, with concentration of about 12-15 g/dl. The highly concentrated Hb solution (35 g/dl) is compartmentalized in red blood cells (RBCs). Once Hb is released from RBCs by hemolysis during blood circulation, it induces renal and cardiovascular toxicities. To date, hemoglobin-based oxygen carriers of various types have been developed as blood substitutes to mitigate the Hb toxicities. One method is Hb encapsulation in phospholipid vesicles (liposomes). Although the Hb toxicity can be shielded, it is equally important to ensure the biocompatibility of the liposomal membrane. We have developed Hb-vesicles (HbV). A new encapsulation method using a rotation-revolution mixer which enabled efficient production of HbV with a high yield has considerably facilitated R&D of HbV. Along with our academic consortium, we have studied the preclinical safety and efficacy of HbV extensively as a transfusion alternative, and finally conducted a phase I clinical trial. Moreover, carbonyl-HbV and met-HbV are developed respectively for an anti-inflammatory and anti-oxidative agent and an antidote for poisons. This review paper specifically presents past trials of liposome encapsulated Hb, biocompatible lipid bilayer membranes, and efficient HbV preparation methods, in addition to potential clinical applications of HbV based on results of our in vivo studies.

Preparation of uniform-sized GeXIVA[1,2]-loaded PLGA microspheres as long-effective release system with high encapsulation efficiency

The purpose of this study was to prepare GeXIVA[1,2] PLGA microspheres by W/O/W re-emulsification-solvent evaporation technology and to develop sustained-release formulations to meet the clinical treatment needs of chronic neuropathic pain. Through prescription optimization, the uniformity of particle size and the encapsulation efficiency is improved, so as to achieve the quality standard of the microspheres. The mechanism of trehalose improving the stability of GeXIVA[1,2] was studied and verified by molecular simulation. The results showed that when adding trehalose to W1, using the PLGA model of 75:25, PLGA concentration of 30%, PVA concentration of 1.5%, adding 1% NaCl to PVA and adding 1% NaCl to solidification water, the prepared microspheres are smooth, the particle size is about 25 μm, and the encapsulation rate reaches 90%. The results of in vitro release experiments showed that the microspheres could be released steadily for about 30 days. The microsphere samples were characterized and analyzed by molecular simulation and powder X-ray diffractometer, and the protective mechanism of trehalose on GeXIVA[1,2] was discussed. The results showed that the hydrogen bond formed between trehalose and GeXIVA[1,2] acted as a hydration film and played a certain protective role on GeXIVA[1,2]. In addition, high-viscosity trehalose can form a glass state and wrap around GeXIVA[1,2], reducing the free movement of molecules. In the microsphere system, trehalose can also avoid the influence of PLGA material on the secondary structure of GeXIVA[1,2]. In conclusion, this study is expected to provide a new therapeutic strategy for the treatment of chronic neuropathic pain.

Dietary Heme-Containing Proteins: Structures, Applications, and Challenges

Heme-containing proteins, commonly abundant in red meat and blood, are considered promising dietary sources for iron supplementation and fortification with higher bioavailability and less side effects. As the precise structures and accurate bioactivity mechanism of various heme-containing proteins (hemoglobin, myoglobin, cytochrome, etc.) are determined, many methods have been explored for iron fortification. Based on their physicochemical and biological functions, heme-containing proteins and the hydrolyzed peptides have been also widely utilized as food ingredients and antibacterial agents in recent years. In this review, we summarized the structural characterization of hemoglobin, myoglobin, and other heme proteins in detail, and highlighted recent advances in applications of naturally occurring heme-containing proteins as dietary iron sources in the field of food science and nutrition. The regulation of absorption rate, auto-oxidation process, and dietary consumption of heme-containing proteins are then discussed. Future outlooks are also highlighted with the aim to suggest a research line to follow for further studies.