1320 The Polymer Society of Korea www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673 Macromolecular Research, Vol. 22, No. 12, pp 1320-1329 (2014) Dual Growth Factor-Loaded Core-Shell Polymer Microcapsules Can Promote Osteogenesis and Angiogenesis Ramesh Subbiah 1,2 , Ping Du 1,2 , Mintai Peter Hwang 2 , In Gul Kim 2 , Se Young Van 1,2 , Yong Kwan Noh 2,3 , Hansoo Park 4 , and Kwideok Park* ,1,2 1 Department of Biomedical Engineering, Korea University of Science and Technology (UST), Daejon 305-350, Korea 2 Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 136-130, Korea 3 Department of Biomedical Engineering, School of Medicine, Kyunghee University, Seoul 130-701, Korea 4 School of Integrative Engineering, Chung-Ang University, Seoul 156-071, Korea Received July 4, 2014; Revised August 5, 2014; Accepted August 26, 2014 Abstract: Growth factors (GFs) are very critical in stem cell differentiation and tissue regeneration. Therefore GF delivery carriers have been a major subject in tissue engineering research. In this study, we prepare and optimize core-shell microcapsules (C-S MCs) for dual GF delivery. The C-S MCs, composed of an alginate shell and poly(lactic-co-glycolic) acid (PLGA) core, are fabricated using an electrodropping method via custom-made coaxial needles. They are 198±38 µm in diameter with an average core size of 90±13 µm, and they are fabricated using an alginate concentration of 1% (w/v), an electrical voltage of 11 kV, and an inner syringe flow rate of 50 µL/min. Using this platform, dual GFs, bone morphogenetic protein (BMP-2) and vascular endothelial growth factor (VEGF) are encapsulated in the alginate shell and PLGA core, respectively. In vitro release tests of dual GF-loaded C-S MCs reveal early release of BMP-2, followed by VEGF on a temporal release profile of 28 days. In vitro study of the dual GF-loaded MCs demonstrates their osteogenic activity with preosteoblasts; osteogenic markers (osteocalcin and type I collagen) are upregulated and both calcium content and alkaline phosphatase (ALP) activity also increased. In addition, C-S MCs combined with collagen and preosteoblasts were subcutaneously transplanted to the dorsal region of nude mice for 3 weeks. Analysis of the retrieved constructs exhibits that both osteogenesis and angiogen- esis were more active in the group containing dual GF-loaded MCs, along with deep penetration of blood vessels inside the construct, compared to blank MCs or single GF (BMP-2)-loaded MCs. This study proposes a dual GF delivery carrier using C-S MCs and demonstrates the feasibility of C-S MCs in the induction of osteogenesis and angiogenesis. Keywords: core-shell microcapsules, dual growth factor delivery, electrodropping, osteogenesis, angiogenesis . Introduction Eliciting the differentiation of stem cells into a particular lineage is a crucial prerequisite for tissue repair and regener- ation. 1-3 Multiple signaling cues have been implicated, includ- ing those of biochemical (growth factors; GFs), biophysical (topography), and biomechanical (elastic modulus) ones. 2,4 While biophysical and biomechanical factors are contact- mediated and generally derived from the environmental niche and its attributes, 2 biochemical cues impart signals in a different manner; non-contact-mediated paracrine signaling and surface-bound (contact-mediated) signaling. Thus, both appropriate selection of GFs and their time-dependent con- trolled delivery of such GFs to target sites are a major interest in the study of stem cells and tissue regeneration. The con- ventional use of single GF bolus delivery has been partially successful in tissue regeneration, due mostly to uncontrolled release of GFs. 5 Consequently, many carrier systems for the localized and controlled delivery of a single GF have been explored and expanded further to the use of multiple GFs. 6-9 Several groups have proven the importance of dual GF delivery in the regeneration of complex tissues. 5,10-13 In particular, the temporally controlled delivery of dual GFs for stem cells differentiation has been extensively investigated. Since Richard- son et al. demonstrated the use of a dual growth factor, such as vascular endothelial growth factor (VEGF) and platelet- derived growth factor (PDGF) in a polymer scaffold-based delivery system for angiogenesis, 5 others have adopted the concept of sequential dual GF delivery for a wide variety of tis- sue engineering applications including angiogenesis, 11 neuro- genesis, 10 osteogenesis, 13,14 myogenesis, 15 and chondrogenesis. 16 In this study, we propose a core-shell microcapsule (C-S MC) DOI 10.1007/s13233-014-2183-x *Corresponding Author. E-mail: kpark@kist.re.kr