Hemocompatibility Evaluation Of Polyethyleneglycol-polycaprolactone Copolymers In Vitro

Amphiphilic block copolymer methoxy polyethyleneglycol-polycaprolactone(m PEG-PCL), due to its biocompatibility and biodegradability, has promising potential in many biomedical applications such as tissue engineering scaffolds and drug/gene/protein delivery systems. In these applications, m PEG-PCL copolymers are used in different forms including micelles, vesicle, micro/nanoparticles, etc. Because foreign biomedical polymer materials introduced in vivo would inevitably interact with key blood components and human umbilical vein vascular endothelial cells(HUVECs). At present, the biocompatibility evaluation of the copolymers is limited to cytotoxicity. Therefore, an investigation of possible interactions of m PEG-PCL with key blood components and HUVECs is indispensable. In this work, we chose two amphiphilic m PEG-PCL copolymers with the same PCL molecular weight 2 k Da but different m PEG lengths 2 and 5 k Da, labeled as m PEG2k-PCL2 k and m PEG5k-PCL2 k, respectively. Here, we aimed to explore the difference in the hemocompatibility of the m PEG-PCL copolymers with different hydrophilicity/hydrophobicity property. In this work, we investigated the effects of the copolymers on human red blood cells(RBCs), plasma fibrinogen, platelet, and complement activation, improving our understanding of the interactions between m PEG-PCL copolymers and blood components, revealing the impact of m PEG-PCL copolymers on coagulation function. At the same time, the influence of m PEG-PCL copolymers on the expression changes of coagulation factors in HUVECs and the blood coagulation function was further studied.1. Evaluation of the hemocompatibility of the two m PEG-PCL copolymers(the second charpter)We studied the effects of two m PEG-PCL copolymers on blood coagulation, the morphology and lysis of human RBCs, the structure of plasma fibrinogen, complement activation, and platelet aggregation. We found that the m PEG-PCL copolymers had little impact on the morphology or lysis of human RBCs by scanning electron microscopy observation and hemolysis test. From spectroscopy results, the copolymers affected the local micro-structure of fibrinogen in a concentration-dependent way. In the presence of high concentration of m PEG-PCL, activated partial thromboplastin time(APTT) values were significantly increased and prothrombin time(PT) values were not significantly altered. We found that higher concentrations of the m PEG-PCL copolymers impaired blood clotting by thrombelastography(TEG) assay and blood rheological behavior study. At higher concentrations, the copolymers activated platelets in a concentration-dependent way and impaired platelet aggregation, which might be mediated by inhibition of arachidonic acid pathway. The copolymers significantly activated the complement system in vitro in a concentration-dependent way.2. Toxicity evaluation and effect on the function of blood coagulation on HUVECs of the two m PEG-PCL copolymers(the third charpter)We studied the effects of two m PEG-PCL copolymers on cell viability, cell cycle, apoptosis, cellular uptake, and expression of blood coagulation factor of HUVECs. In cell viability assay, the toxicity of m PEG-PCL copolymers was in a concentration-dependent way. In nitrite assay, it found that the m PEG-PCL copolymers increased the emissions of NO in a concentrationdependent way. We found that concentrations of m PEG-PCL from 0.1 to 10 mg/m L could not cause the apoptosis of HUVECs. In the cell cycle analysis, m PEG5k-PCL2 k at 10 mg/m L prevented some HUVECs in G0/G1 phase. The endocytosis ability of m PEG2k-PCL2 k and m PEG5k-PCL2 k copolymers were evaluated. It could be found that m PEG2k-PCL2 k were more easily internalized into HUVECs. Finally, m PEG-PCL at higher concentration induced low expression of t-PA and high expression of TF and v WF in HUVECs, increasing the risk of intravascular thrombosis. This conclusion has been verified by TEG assay.