Capillary action: enrichment of retention and habitation of cells via micro-channeled scaffolds for massive bone defect regeneration Min-Ho Hong • Yoon Hyuk Kim • Danaa Ganbat • Do-Gyoon Kim • Chun-Sik Bae • Daniel S. Oh Received: 9 January 2014 / Accepted: 21 April 2014 Ó Springer Science+Business Media New York 2014 Abstract The development of a biomaterial substitute that can promote bone regeneration in massive defects has remained as a significant clinical challenge even using bone marrow cells or growth factors. Without an active, thriving cell population present throughout and stable anchored to the construct, exceptional bone regeneration does not occur. An engineered micro-channel structures scaffold within each trabecular has been designed to overcome some current limitations involving the cultiva- tion and habitation of cells in large, volumetric scaffolds to repair massive skeletal defect. We created a scaffold with a superior fluid retention capacity that also may absorb bone marrow cells and provide growth factor-containing body fluids such as blood clots and/or serum under physiological conditions. The scaffold is composed of 3 basic structures (1) porous trabecular network (300–400 lm) similar to that of human trabecular bones, (2) micro-size channels (25–70 lm) within each trabecular septum which mimic intra-osseous channels such as Haversian canals and Volkmann’s canals with body fluid access, diffusion, nutritional supply and gas exchange, and (3) nano-size pores (100–400 nm) on the surface of each septum that allow immobilized cells to anchor. Combinatorial effects of these internal structures result in a host-adapting con- struct that enhances cell retention and habitation through- out the 3 cm-height and 4 cm-length bridge-shaped scaffold. 1 Introduction The absence of a functional microenvironment in most synthetic constructs has hampered the potential for clinical applications and the success of bone tissue engineering [1– 3]. To this day, successful incorporation of new bone for- mation has been dependent on the loading of pre-expanded mesenchymal stem cells (MSCs) and/or large amounts of growth factors, requiring elaborate laboratory techniques and excessive costs [4–6]. For this reason, inducing bone formation using natural micro-environmental cues has become a major focus in tissue-engineering research. During the past decade, scientists have employed a vast number of techniques to mimic natural bone characteristics such as pore size, porosity, interconnectivity of the pores, and permeability through synthetic grafts [7–11]. These factors collectively play a role in cell attachment, prolif- eration, and differentiation as well as in nutrient flow and cell communication, all of which are crucial for proper bone healing [12, 13]. The primary problems with large synthetic grafts are a lack of (i) appropriate architecture, which allows bone cell infiltration and distribution in a three-dimensional envi- ronment necessary for successful bone regeneration, and Min-Ho Hong and Yoon Hyuk Kim are equally contributed for this work. M.-H. Hong  D. S. Oh (&) Department of Orthopaedic Surgery, Center for Orthopaedic Research, Columbia University, New York, NY, USA e-mail: dso2113@columbia.edu M.-H. Hong  Y. H. Kim  D. Ganbat Mechanical Engineering, Kyung Hee University, Yongin, Korea D.-G. Kim Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH, USA C.-S. Bae College of Veterinary Medicine, Chonnam National University, Gwangju, Korea 123 J Mater Sci: Mater Med DOI 10.1007/s10856-014-5225-1