*4.11. Statistical Analysis*

Statistical analysis for in vitro was performed using Excel. A two-tailed Student's unpaired *t*-test was performed to compare the untreated control group with the treated groups. The results were considered significant when *p* < 0.05 (\*, *p* < 0.05; \*\*, *p* < 0.01). Independent experiments were conducted with a minimum of two biological replicates per condition to allow statistical comparison. Error bars represent the standard error of the mean, and the *p* values are indicated. All experiments were repeated at least three times.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1660-3397/17/5/257/s1, Table S1: Analysis of the affinity between PSS and VEGF165, Figure S1: The effect of PSS on the migration of HUVEC cells, Figure S2: The electrostatic potential surface of FGF2 and VEGF165.

**Author Contributions:** H.M., P.Q., X.X., M.X., and H.X. performed the experiments. P.Q. designed the experiments. J.Y. and C. L. analyzed data. H.M. and P.Q. wrote the manuscript. J.Y., C.L., and Y.C. revised the manuscript. All the authors approved the final manuscript. All authors discussed the drafts and approved the final manuscript for publication.

**Funding:** This work was supported by The National Natural Science Fund (Grant No. 31701221), The Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology (Qingdao) (No.2018SDKJ0404-4), and the Shandong Science and Technology Project (Grant No. 2014GGH215001). Qingdao Leading Talents Program (Grant No. 16-8-3-11-zhc), "Ao Shan Talents" Program Supported by Qingdao National Laboratory for Marine Science and Technology (Grant No. 2017ASTCP-OS11).

**Conflicts of Interest:** The authors declare that they have no competing financial interests to disclose.
