© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com 1 COMMUNICATION Surface Charge Regulation of Osteogenic Differentiation of Mesenchymal Stem Cell on Polarized Ferroelectric Crystal Substrate Jianhua Li, Xiaoning Mou, Jichuan Qiu, Shu Wang, Dongzhou Wang, Dehui Sun, Weibo Guo, Deshuai Li, Anil Kumar, Xuebin Yang, Aixue Li,* and Hong Liu* J. H. Li, Dr. X. N. Mou, S. Wang, W. B. Guo, D. S. Li, Dr. A. Kumar, Prof. A. X. Li, Prof. H. Liu Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083, China E-mail: liaixue@binn.cas.cn; hliu@binn.cas.cn, hongliu@sdu.edu.cn J. H. Li, J. C. Qiu, D. Z. Wang, D. H. Sun, Prof. H. Liu State Key Lab of Crystal Materials Shandong University 27 Shandanan Road, Jinan 250100, China Prof. X. B. Yang Biomaterials and Tissue Engineering Group School of Dentistry University of Leeds Leeds, LS2 9LU, UK DOI: 10.1002/adhm.201500032 small charged monomers to study the effects of fixed electrical charge on chondrocyte behavior. [6c] Bodhak et al. [6d] investigated the influence of surface charge and polarity on in vitro bone cell adhesion, proliferation, and differentiation on electrically polar- ized hydroxyapatite-coated Ti. There are also a few reports, which focus on investigating the cellular response to charged functional groups (i.e., –COOH, negatively chargeable; –CH 2 OH,–CONH 2 , –CH 2 –CH 3 , neutral; –CH 2 NH 2 , positively chargeable) with modi- fied surfaces post-polymerization. [6e,f ] These studies shed light on the importance of the surface charging state for designing and constructing a biomaterial culture system. However, in the above cases, the surface charge was not the only variable, which means that the other properties such as surface chemistry and roughness of the substrate may be altered alongside the sur- face charging state of the substrate. Besides, up to now, little attention has been paid to the response of stem cells to surface charge characteristics, particularly the differentiation of stem cells. Therefore, there is a need to develop a simplified model for single-factor study in order to solely investigate the effect of the surface charge on stem cell behavior. In this study, a ferroelectric crystal platform has been devel- oped to provide oppositely charged surfaces, and this novel material has been used as a 2D culture substrate for enhancing the osteogenesis of rat bone marrow mesenchymal stem cells (rBMMSCs). It is well known that LiNbO 3 (LN) is a typical ferro- electric crystal, which has a range of applications in many fields because of its multifunctional characteristics. Normally, LN single crystal can be grown by the Czochralski technique from a congruent melt. The as-grown LN crystal is a multidomain structure with 180° ferroelectric domains by using a polariza- tion technique, the multidomained LN can become a single domain. The poled LN crystal possesses a unified internal potential along the Z-axis with opposite charges absorbed on the two surfaces to balance the internal potential. Therefore, for Z-cut poled LN wafers, the Z+ surface is positively charged and absorbs negative charges, while the Z-surface is negatively charged and absorbs positive charges. For X- and Y-cut wafers, both of the surfaces of a wafer are neutral, i.e., uncharged. The density of surface charge in response to the application of an external stress to the ferroelectrics is called piezoelectricity. A change in the spontaneous polarization of a material in response to a change in temperature is called pyroelectricity. Both of piezoelectric and epyroelectric properties are based on the change of surface charge and have had great application in many fields, such as hydroacoustic transducer, piezolighter, pyroelectric imaging instrument, etc. However, there is no With their ability to self-renew and differentiation into multiple cell types, stem cells (embryonic stem cells, induced pluripo- tent stem cells, and adult stem cells) are the stalwarts of regen- erative medicine. [1] However, the in vitro regulation of stem cell fate, to ultimately drive the cells to create a therapeutically rel- evant tissue, remains challenging due to the difficulties associ- ated with mimicking the complex in vivo tissue-specific niches of stem cells. In recent years, biomaterials have been rapidly developed to meet such a challenge through the manipula- tion of interfaces between the cell and the extracellular matrix; within which materials can provide cells with chemical, mechanical, and structural guidance. [2] To identify and assess the effects of individual niche components on stem cell fate, 2D biomaterial culture systems are often used as a simplified approach to reconstruct the niche. A number of studies have shown that 2D surface factors, such as chemistry, [3] topography, [3a] elasticity, [2c,4] and molecular chirality, [5] have been demonstrated to individually or syner- gistically affect cell behavior with recent interest surrounding their involvement in the regulation of stem cell differentiation. Similarly, biomaterial surface charge became another important factor with a high impact on cellular behavior. [6] To date, many substrates with differently charged surfaces, fabricated by various methods, have been reported. For example, Iwai et al. [6a] reported precisely charged culture surfaces, prepared by mixing positively and negatively charged monomers at various charge ratios, which can lead to drastic morphological changes of adipose-derived vas- cular progenitor cells. In another study, electrical charges were incorporated into a derivative of poly(ethylene glycol) using Adv. Healthcare Mater. 2015, DOI: 10.1002/adhm.201500032 www.advhealthmat.de www.MaterialsViews.com