3.7. In vitro cytotoxicity study
The biocompatibility of agents is the most important precondition of clinical translation. To make sure that OHH NPs could be potentially translated for practical application, in vitro cytotoxicity experiments were performed with NIH-3T3 cells and HUV-EC cells. According to Fig. 7A and Fig. S5, the viability of two cell lines incubated with various concentrations of OHH NPs for 24 h remained at ∼100%, even at the concentration of 125 μg/mL, suggesting the ultra-low cytotoxic nature of OHH NPs. The in vitro biocompatibility of OHH NPs was further assessed by hemolysis assay. As can be seen in Fig. 7B, hemolytic rate after exposure to OHH NPs even at the concentration of 150 μg/mL was only 3.9%, indicating good biocompatibility of OHH NPs. In hemolysis and cytotoxicity assays (Fig. S6), it should be noted that OHH NPs showed better biocompatibility than HMPB NPs, which was likely attributed to the fact that HA coating with superior biocompatibility reduced in vitro cytotoxicity of HMPB NPs. In addition, platelet aggregation assay displayed OHH NPs hardly caused platelet aggregation, demonstrating their little risk of inducing thrombosis (Fig. S7).