EFFECTS OF POLY(ETHYLENEGLYCOL)-MODIFIED HEMOGLOBIN VESICLES ON AGONIST-INDUCED PLATELET AGGREGATION AND RANTES RELEASE IN VITRO

Effects and treatment applications of polymeric nanoparticles on improving platelets' storage time: a review of the literature from 2010 to 2020

Maintaining the quality of platelet products and increasing their storage time are priorities for treatment applications. The formation of platelet storage lesions that limit the storage period and preservation temperature, which can prepare a decent environment for bacterial growth, are the most important challenges that researchers are dealing with in platelet preservation. Nanotechnology is an emerging field of science that has introduced novel solutions to resolve these problems. Here, we reviewed the reported effects of polymeric nanoparticles-including chitosan, dendrimers, polyethylene glycol (PEG), and liposome-on platelets in articles from 2010 to 2020. As a result, we concluded that the presence of dendrimer nanoparticles with a smaller size, negative charge, low molecular weight, and low concentration along with PEGylation can increase the stability and survival of platelets during storage. In addition, PEGylation of platelets can also be a promising approach to improve the quality of platelet bags during storage.

Adhesive interaction between peripheral blood mononuclear cells and activated platelets in the presence of anti-human leukocyte antigen Class I alloantibody causes production of IL-1β and IL-8

BACKGROUND

Activated platelets form heterogeneous aggregates of platelets and monocytes, which are involved in a variety of inflammatory disorders. Some anti-human leukocyte antigen (HLA) Class I antibodies have been shown to activate platelets.

MATERIALS AND METHODS

Human leukocyte antigen-A2-positive or HLA-A2-negative platelets were incubated with HLA-A2-negative peripheral blood mononuclear cells (PBMNCs) in the presence of anti-HLA-A2 serum at 37°C. The binding of platelets to monocytes was analysed by flow cytometry. The levels of IL-1 β and IL-8 in the culture supernatant were determined by ELISA.

RESULTS

Anti-HLA-A2 serum increased the formation of aggregates between monocytes and HLA-A2-positive platelets, but not HLA-A2-negative platelets, in a dose-dependent manner. Antiserum also increased the number of platelets bound to monocytes in a time-dependent manner. The addition of anti-P-selectin glycoprotein ligand (PSGL-1) mAb almost completely inhibited the formation of platelet-monocyte aggregates as well as the number of platelets bound to monocytes. When HLA-A2-positive or HLA-A2-negative platelets were incubated with HLA-A2-negative PBMNCs in the presence of anti-HLA-A2, the level of IL-1β and IL-8 in the supernatant of coculture was significantly higher in HLA-A2-positive platelets than in HLA-A2-negative platelets. The addition of anti-PSGL-1 mAb partially but significantly inhibited the production of both IL-1β and IL-8.

CONCLUSIONS

The activation of platelets with anti-HLA Class I alloantibody caused the formation of platelet-monocyte aggregates, followed by the production of IL-1β and IL-8, in a cognate antigen-antibody manner. The adhesive interaction of P-selectin and PSGL-1 at least partially contributed to these phenomena.

Interaction of Hemoglobin Vesicles, a Cellular-Type Artificial Oxygen Carrier, with Human Plasma: Effects on Coagulation, Kallikrein-Kinin, and Complement Systems

Hemoglobin vesicles (HbVs), cellular-type artificial oxygen carriers containing human hemoglobin, were assessed for their biocompatibility by mixing with human plasma in vitro. Among three kinds of HbVs (PEG-DPEA-HbV, PEG-DPPG-HbV and DPPG-HbV), PEG-DPEA-HbV did not affect the extrinsic or intrinsic coagulation activities of the plasma, while PEG-DPPG-HbV and DPPG-HbV tended to shorten the intrinsic coagulation time. The kallikrein-kinin cascade of the plasma was slightly activated by PEG-DPPG-HbV and DPPG-HbV, but not by PEG-DPEA-HbV. The complement consumption of the plasma was observed by incubation with DPPG-HbV, but not with PEG-DPEA-HbV or PEG-DPPG-HbV. These results indicate that PEG-DPEA-HbV has a higher biocompatibility with human plasma.

Effects of Hemoglobin Vesicles, a Liposomal Artificial Oxygen Carrier, on Hematological Responses, Complement and Anaphylactic Reactions in Rats

Hemoglobin vesicle (HbV), a liposomal oxygen carrier containing human hemoglobin, was intravenously infused into rats. After the infusion of saline, the HbV or empty vesicle (EV), numbers of red cells, leukocytes and platelets in peripheral blood were unchanged during the observation period of one week in addition to each time point among three groups. However, the lymphocyte ratio transiently decreased and the granulocyte ratio increased in the HbV and EV groups at 6 h after the infusion. Those changes returned to the initial value one day after the infusion and those were maintained for the subsequent observation period. No dramatic change was seen in the ratio of CD4(+)/CD8(+) T cells. A transient decrease of the complement titer was observed three days after the infusion of HbV and EV, although the consumption of complement titer was not detected in rat serum by mixing HbV or EV in vitro, indicating that the transient decrease of complement titer in vivo was not due to the consumption of complement due to the interaction with HbV or EV. Multiple infusions of HbV caused the decrease of complement titer only after the first infusion and no allergic reaction was observed. No anaphylactic shock was observed in rats administered with EV several times, while ovalbumin (OVA) sensitized rats died with symptoms of respiratory distress after the second OVA administration. These results indicate that HbV could be administered without serious clinical symptoms or adverse reactions.

Haemoglobin-vesicles as artificial oxygen carriers: present situation and future visions

During the long history of development of haemoglobin (Hb)-based O2 carriers (HBOCs), many side effects of Hb molecules have become apparent. They imply the physiological importance of the cellular structure of red blood cells. Hb-vesicles (HbV) are artificial O2 carriers that encapsulate concentrated Hb solution with a thin lipid membrane. We have overcome the intrinsic issues of the suspension of HbV as a molecular assembly, such as stability for storage and in blood circulation, blood compatibility and prompt degradation in the reticuloendothelial system. Animal tests clarified the efficacy of HbV as a transfusion alternative and the possibility for other clinical applications. The results of ongoing HbV research make us confident in advancing further development of HbV, with the expectation of its eventual realization.

Physical properties and stability mechanisms of poly(ethylene glycol) conjugated liposome encapsulated hemoglobin dispersions

Liposomes encapsulating hemoglobin (LEHs) surface-conjugated with 2000 and 550 Da poly(ethylene glycol) (PEG) were produced via extrusion through 400, 200 and 100 nm pore diameter membranes in two types of phosphate buffer with different ionic strengths. The lipid bilayers were composed of dimyristoyl-phosphatidylcholine (DMPC), cholesterol, dimyristoyl-phosphoethanolamine-PEG (DMPE-PEG), dimyristoyl-phosphatidylglycerol (DMPG), and alpha-tocopherol (in a 43:40:10:5:2 mole ratio). N-acetyl-L-cysteine was coencapsulated in order to suppress hemoglobin (Hb) oxidation. Various physical properties of PEG-LEH dispersions were determined: size distribution, encapsulation efficiency, P50 (partial pressure of O2 where half of the oxygen binding sites are saturated with O2), cooperativity coefficient, and encapsulated methemoglobin (MetHb) level. In order to study the stabilization mechanism of these dispersions, the effective bending constant (KB) and the spontaneous radius of curvature (R0) of PEG-LEHs were extracted by fitting a mathematical model describing the size distribution of a liposome dispersion to the experimentally measured size distributions. We observed that liposome dispersions extruded in phosphate buffer (PB) were more monodisperse than liposomes extruded in phosphate buffered saline (PBS), and higher molecular weight PEG promoted the formation of narrower size distributions. Moreover, extrusion in PB and lipid conjugation with higher molecular weight PEG imparted higher bilayer rigidity (high KB), and stabilized the liposome dispersions by the spontaneous curvature mechanism, whereas the other liposome dispersions were stabilized by thermal undulations (low KB). The P50 and cooperativity coefficient of PEG-LEHs extruded in PBS and PB was comparable to that of human blood, and the encapsulated MetHb levels were less than 5%. The highest encapsulation efficiencies obtained were 27%-36% (82-109 mg Hb/mL) for LEH dispersions extruded in PBS and grafted with 2000 Da PEG. These dispersions yielded KBs' ranging from 7kT to 27kT, which indicated that these dispersions were stabilized by spontaneous curvature. Whereas the same lipid combination extruded in PBS, however, instead conjugated with 550 Da PEG resulted in KBs' ranging from 2 kT to 2.7 kT, which indicated that these dispersions were stabilized by thermal undulations. Thermal undulations permitted Hb leakage through the lipid bilayers, which in turn lowered the encapsulation efficiency to 1%-10.7% (3-32 mg Hb/mL). Taken together, the experimentally measured size distributions and encapsulation efficiencies of PEG-LEH dispersions can be readily explained through analysis of the magnitude of KB, which dictates the stability mechanism of the liposome dispersion.

Circulation Kinetics and Organ Distribution of Hb-Vesicles Developed as a Red Blood Cell Substitute

Phospholipid vesicles encapsulating concentrated human hemoglobin (Hb-vesicles, HbV), also known as liposomes, have a membrane structure similar to that of red blood cells (RBCs). These vesicles circulate in the bloodstream as an oxygen carrier, and their circulatory half-life times (t(1/2)) and biodistribution are fundamental characteristics required for representation of their efficacy and safety as a RBC substitute. Herein, we report the pharmacokinetics of HbV and empty vesicles (EV) that do not contain Hb, in rats and rabbits to evaluate the potential of HbV as a RBC substitute. The samples were labeled with technetium-99m and then intravenously infused into animals at 14 ml/kg to measure the kinetics of HbV elimination from blood and distribution to the organs. The t(1/2) values were 34.8 and 62.6 h for HbV and 29.3 and 57.3 h for EV in rats and rabbits, respectively. At 48 h after infusion, the liver, bone marrow, and spleen of both rats and rabbits had significant concentrations of HbV and EV, and the percentages of the infused dose in these three organs were closely correlated to the circulatory half-life times in elimination phase (t(1/2beta)). Furthermore, the milligrams of HbV per gram of tissue correlated well between rats and rabbits, suggesting that the balance between organ weight and body weight is a fundamental factor determining the pharmacokinetics of HbV. This factor could be used to estimate the biodistribution and the circulation time of HbV in humans, which is estimated to be equal to that in rabbit.