Nano-Scaffold for Therapeutic Angiogenesis 49. Sung HJ, Meredith C, Johnson C, Galis ZS (2004) The effect of scaffold degradation rate on three-dimensional cell growth and angiogenesis. Biomate- rials 25: 5735–5742. 50. Athanasiou KA, Niederauer GG, Agrawal CM (1996) Sterilization, toxicity, biocompatibility and clinical applications of polylactic acid/polyglycolic acid copolymers. Biomaterials 17: 93–102. 51. Bostman O, Pihlajamaki H (2000) Clinical biocompatibility of biodegradable orthopaedic implants for internal fixation: a review. Biomaterials 21: 2615–2621. 52. Kadono H, Furuzono T, Masuda M, Okada M, Ueki M, et al. (2010) In vivo evaluation of hydroxyapatite nanocoating on polyester artificial vascular grafts and possibility as soft-tissue compatible material. ASAIO J 56: 61–66. 53. Hile DD, Doherty SA, Trantolo DJ (2004) Prediction of resorption rates for composite polylactide/hydroxylapatite internal fixation devices based on initial degradation profiles. J Biomed Mater Res B Appl Biomater 71: 201–205. 54. Tang YL, Zhu W, Cheng M, Chen L, Zhang J, et al. (2009) Hypoxic preconditioning enhances the benefit of cardiac progenitor cell therapy for treatment of myocardial infarction by inducing CXCR4 expression. Circ Res 104: 1209–1216. 55. Schioppa T, Uranchimeg B, Saccani A, Biswas SK, Doni A, et al. (2003) Regulation of the chemokine receptor CXCR4 by hypoxia. J Exp Med 198: 1391–1402. 56. Ceradini DJ, Kulkarni AR, Callaghan MJ, Tepper OM, Bastidas N, et al. (2004) Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1. Nat Med 10: 858–864. PLoS ONE | www.plosone.org 12 April 2012 | Volume 7 | Issue 4 | e35199