Sen Gupta, A. | bioRxiv Science

bioRxiv2022

Characterization of the Interaction of Nanobubble Ultrasound Contrast Agents with Human Blood Components

Nanoscale ultrasound contrast agents, or nanobubbles, are being explored in preclinical applications ranging from vascular and cardiac imaging to targeted drug delivery in cancer. These sub-micron particles are approximately 10x smaller than clinically available microbubbles. This allows them to effectively traverse compromised physiological barriers and circulate for extended periods of time. While various aspects of nanobubble behavior have been previously examined, their behavior in human whole blood has not yet been explored. Accordingly, herein we examined, for the first time, the short and long-term effects of blood components on nanobubble acoustic response. We observed differences in the kinetics of backscatter from nanobubble suspensions in whole blood compared to bubbles in phosphate buffered saline (PBS), plasma, or red blood cell solutions (RBCs). Specifically, after introducing nanobubbles to fresh human whole blood, signal enhancement gradually increased by 22.8 {+/-} 13.1% throughout our experiment, with peak intensity reached within 145 seconds. In contrast, nanobubbles in PBS had a stable signal with negligible change in intensity (-1.7 {+/-} 3.2%) over 8 minutes. Under the same conditions, microbubbles made with the same lipid formulation showed a -56.8 {+/-} 6.1% decrease in enhancement. Subsequent confocal, fluorescent, and scanning electron microscopy analysis revealed attachment of the nanobubbles to the surface of RBCs, suggesting that direct interactions, or hitchhiking, of nanobubbles on RBCs in the presence of plasma may be a possible mechanism for the observed effects. This phenomenon could be key to extending nanobubble circulation time and has broad implications in drug delivery, where RBC interaction with nanoparticles could be exploited to improve delivery efficiency.

bioengineering↗

bioRxiv2020

Targeting Thymidine Phosphorylase with Tipiracil Hydrochloride is a Safe and Effective Antithrombotic Therapy

RationaleMost of the current anti-platelet drugs inhibit platelet function permanently and have systemic side effects, including thrombocytopenia and hemorrhage. We previously found that thymidine phosphorylase (TYMP), a platelet cytoplasmic protein, facilitates multiple agonist induced platelet activation and enhances thrombosis. A specific TYMP inhibitor, namely, tipiracil hydrochloride (TPI), has been approved by the U.S. Food and Drug Administration for clinical use as an auxiliary drug making it possible to be repositioned as an anti-platelet medicine. ObjectiveWe aimed to test the hypothesis that TPI is a novel and safe anti-platelet drug by examining its role in platelet activation and thrombosis using both in vitro and in vivo studies. Methods and ResultsBy co-expression of TYMP and Lyn or Lyn-SH3 domain tagged with glutathione S-transferase, we showed the direct evidence that TYMP binds to the SH3 domain in its partners. TYMP haplodeficiency is sufficient to inhibit thrombosis in vivo regardless of gender. TPI treatment rapidly inhibited collagen- and ADP-induced platelet aggregation, which copied the phenotype of TYMP deficient platelets. Under both normal and hyperlipidemic conditions, treating wild type (WT) mice with TPI via intraperitoneal injection, intravenous injection, or gavage feeding dramatically inhibited thrombosis without inducing significant bleeding. Even administered above the effective dose, TPI has a lower bleeding side effect compared to aspirin and clopidogrel. Most importantly, intravenously delivery of TPI alone or combined with tissue plasminogen activator dramatically inhibited the growth of developing thrombi. Dual administration of very low dose of aspirin and TPI also dramatically inhibited thrombosis without disturbing hemostasis. ConclusionThis pharmacological study demonstrated that TYMP participates in multiple signaling pathways in platelet and plays a mechanistic role in regulating platelet activation and thrombosis. TPI, a specific TYMP inhibitor, would be a novel safe anti-platelet and anti-thrombosis medicine.

cell biology↗