Interaction between erythrocytes and a perfluorochemical blood substitute

Cytosolic perfluorocarbon delivery to platelets via albumin for antithrombotic therapy

Thrombosis is a major contributor to global disease burden. Antiplatelet therapy is the critical approach to prevent thrombosis by reducing platelet reactivity. However, classical antiplatelet strategies generally interfere with platelet integrin α_IIbβ₃-mediated platelet activation, thereby facing severe bleeding risk. To break the limitation, we described an integrin α_IIbβ₃-independent antiplatelet method by cytosolic delivery of nanoscale perfluorocarbon (PFC) to platelets via albumin carrier. Denatured albumin was found to build high affinity with platelets to mediate cytosolic PFC delivery. While, cytosolic PFC impaired cytoskeleton reorganization during platelet activation to inhibit relevant platelet functions, but avoided to interfere with integrin α_IIbβ₃. We proved that this α_IIbβ₃-indenpendent antiplatelet pattern showed potential antiplatelet effect with low bleeding risk to prevent thrombosis in various thrombosis models. Together, cytosolic PFC delivery via albumin is a promising antiplatelet approach, and will provide an alternative regimen for current antithrombotic therapy.

Perfluorocarbon nanoparticle-mediated platelet inhibition promotes intratumoral infiltration of T cells and boosts immunotherapy

Cancer immunotherapy can stimulate and enhance the ability of the immune system to recognize, arrest, and eliminate tumor cells. Immune checkpoint therapies (e.g., PD-1/PD-L1) have shown an unprecedented and durable clinical response rate in patients among various cancer types. However, a large fraction of patients still does not respond to these checkpoint inhibitors. The main cause of this phenomenon is the limited T-cell infiltration in tumors. Therefore, additional strategies to enhance T-cell trafficking into tumors are urgently needed to improve patients' immune responses. In this study, we screened an array of perfluorocarbon compounds, reporting that albumin-based perfluorotributylamine nanoparticles (PFTBA@Alb) can effectively increase the permeability of tumor blood vessels, and no distinct side effects were found on normal blood vessels. After i.v. administration of PFTBA@Alb, the number of tumor-infiltrating CD8⁺ and CD4⁺ T cells showed an obvious rising trend. More important, a striking tumor inhibition rate, reaching nearly 90%, was observed when combining PFTBA@Alb with anti-PD-L1 antibody. These findings suggest that PFTBA@Alb can be regarded as an enhancer for anti-PD-L1 immunotherapy.

Two-stage oxygen delivery for enhanced radiotherapy by perfluorocarbon nanoparticles

Tumors are usually hypoxic, which limits the efficacy of current tumor therapies, especially radiotherapy in which oxygen is essential to promote radiation-induced cell damage. Herein, by taking advantage of the ability of perfluorocarbon (PFC) to promote red blood cell penetration, we developed a simple but effective two-stage oxygen delivery strategy to modulate the hypoxic tumor microenvironment using PFC nanoparticles. Methods: We first examined the two-stage oxygen delivery ability of PFC nanoparticles on relieving tumor hypoxia through platelet inhibition. To evaluate the effect of PFC nanoparticles on radiation sensitization, CT26 tumor and SUM49PT tumor model were used. Results: In this study, PFC was encapsulated into albumin and intravenously injected into tumor-bearing mice without hyperoxic breathing. After accumulation in the tumor, PFC nanoparticles rapidly released the oxygen that was physically dissolved in PFC as the first-stage of oxygen delivery. Then, PFC subsequently promoted red blood cell infiltration, which further released O2 as the second-stage of oxygen delivery. Conclusion: The hypoxic tumor microenvironment was rapidly relieved via two-stage oxygen delivery, effectively increasing radiotherapy efficacy. The safety of all substances used in this study has been clinically demonstrated, ensuring that this simple strategy could be rapidly and easily translated into clinical applications to solve the clinical problems associated with tumor hypoxia.

Alteration of mitochondrial bioenergetics due to intravenous injection of a perfluorocarbon emulsion

Wistar albino rats were intravenously injected with 1 ml of an oxyphoretic emulsion of perfluorobutyl-furane and killed 3, 7 or 30 days later. Mitochondria isolated from the liver and kidneys of treated rats showed a small decrease in the transmembrane electrical potential and a substantial depression of the rates of both ATP synthesis and ADP-stimulated respiration. These alterations in mitochondrial oxidative phosphorylation appear to be induced by perfluorocarbon and/or tensioactive molecules interacting with hydrophobic cell structures.

Biochemical and morphological observations on rat liver and kidneys six months after intravenous injection of a perfluorocompound emulsion

The histological appearance of liver and kidneys and the energy metabolism of isolated liver and kidney mitochondria were evaluated in rats 6 months after intravenous administration of 1 ml of a perfluorocompound emulsion. Both liver and kidney specimens showed neither significant histological alteration nor the presence of intracytoplasmic perfluorocompound particles. A substantial depression of the rate of ATP synthesis was observed both in liver and kidney isolated mitochondria (with respect to control mitochondria) although the magnitude of the transmembrane electrical potential was unaltered. The depression of ATP synthesis in mitochondria isolated from perfluorocompound-treated rats appeared then unrelated to the presence of perfluorocompound micelles within the cells, and might result from the interaction of either the perfluorocompound or the emulsifying agent with the mitochondrial ATP synthetase.

Potential clinical applications for blood substitutes

In the coming decade, it is likely that oxygen-carrying alternatives to red blood cells will become available for clinical use. The driving force behind their development is the risk of transfusion of homologous blood, which includes transmission of viral disease (HIV and hepatitis) and transfusion reactions as well as the expense of collecting and storing human blood. A number of clinical applications for these products can be anticipated now, but when available, it is likely that the list will grow. How widely these products will be used depends on their safety. In addition to these clinical applications, blood substitutes will be useful in furthering our understanding of basic oxygen transport physiology.

Synthetic oxygen transport fluids based on perfluorochemicals: applications in medicine and biology

Recent advances in the development and assessment of synthetic oxygen transport fluids based on perfluorochemicals (PFCs) are reviewed. The basic properties of PFCs are outlined, together with the selection criteria for biomedical applications. PFCs must be emulsified for intravascular use and attention is focussed on the formulation and biocompatibility testing of both first- and second-generation emulsions and their components in man and other species. The multidisciplinary applications for PFCs in medicine and basic biomedical research are described, including the clinical use of Fluosol-DA 20% as an oxygen-carrying perfusate in percutaneous transluminal coronary angioplasty.