International Journal of Biological Macromolecules 102 (2017) 10–18 Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l ho me pa g e: www.elsevier.com/locate/ijbiomac Itaconic acid grafted carboxymethyl chitosan and its nanoparticles: Preparation, characterization and evaluation Yanyan Yin a,1 , Qifeng Dang a,1 , Chengsheng Liu a,∗ , Jingquan Yan b , Dongsu Cha c , Zhenzhen Yu a , Yachan Cao a , Yan Wang a , Bing Fan d a College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China b School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, PR China c The Graduate School of Biotechnology, Korea University, Seoul 136-701, South Korea d Qingdao Aorun Biotechnology Co. Ltd., Room 602, Century Mansion, 39 Donghaixi Road, Qingdao 266071, PR China a r t i c l e i n f o Article history: Received 9 December 2016 Received in revised form 21 March 2017 Accepted 2 April 2017 Available online 4 April 2017 Keywords: Itaconic acid grafted carboxymethyl chitosan Preparation Characterization Nanoparticle Cytotoxicity a b s t r a c t This work aims to synthesize a novel itaconic acid (IA) grafted carboxymethyl chitosan (PICMCS), and further fabricate its nanoparticles for potential biomedical applications. First, PICMCS was prepared via free-radical polymerization of IA monomer, in the presence of ammonium persulfate as an initiator and nitrogen as a protector. Its chemical structure was confirmed by FTIR and 1 H NMR. The IA substitu- tion degree calculated by elemental analysis data was 1.85, implying that IA was successfully grafted to carboxymethyl chitosan (CMCS). XRD and TGA patterns illustrated its well-defined crystallinity and ther- mostability. Second, PICMCS nanoparticles were fabricated by electrostatic attraction between carboxyl and amino groups in the absence of any additional agent, which were of obvious core-shell structures with an average particle size of 144 nm and a polydispersity index of 0.11. PICMCS nanoparticles exhibited excellent physical stability after storage at 25 ◦ C for 30 days, without any aggregation. PICMCS nanopar- ticles with high negative surface charge also indicated the good stability, especially in neutral or alkaline media. Additionally, the cytotoxicity experiments showed that either PICMCS or its nanoparticles had better cytocompatibility toward L929 cells than CMCS. These findings above suggested that PICMCS was a kind of promising material for preparing nanoparticles used in biomedical field. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Nanoparticles have been receiving great concern from schol- ars and experts in various research areas, because of their unique physicochemical properties. Especially in biomedical field, their excellent properties, such as large specific surface area, suitable size, uniform distribution, and regular shape [1], enable them to be widely applied in drug delivery system [2], targeted cancer therapy [3,4], and biological diagnosis [5]. And more notably, nanoparti- cles can largely improve the solubility of hydrophobic drugs, exert sustained release action [6,7], protect drugs from enzymatic degra- dation [8], enhance targeting effect to reduce the damage to normal cells and tissue [9], promote intracellular penetration, and pro- long retention time [10]. Nowadays, the growing applications in ∗ Corresponding author. E-mail address: liucsouc@126.com (C. Liu). 1 These authors contributed equally to this work. biomedicine and tissue engineering are putting forward higher requirements to the stability and biocompatibility of nanoparticles. Among large quantities of natural materials, chitosan (CS) and its derivatives have become one of the suitable candidates for preparing nanoparticles, due to their good biocompatibility, biodegradability, and antibacterial activity [11]. However, amino groups on CS skeletons, with high positive charge, are able to interact with cell membrane that carries negative charge, caus- ing damage to cells to a certain extent [12]. Compared with CS, carboxymethyl chitosan (CMCS) is a water-soluble CS deriva- tive, whose introduced carboxyl groups can partly counteract the cationic damage to cell membrane. Nevertheless, CMCS nanopar- ticles prepared by several common methods still exist somewhat drawbacks, like uncontrollable size, poor stability, and damage to red blood cells (RBCs) [12,13]. For either CS or CMCS, there are various usual ways to prepare nanoparticles, including emulsion cross-linking [14], ionic cross-linking [15], spray drying [16,17], and self-assembly by hydrophobic modification [12,18]. But each method has its own deficiencies: (1) the employment of chemical http://dx.doi.org/10.1016/j.ijbiomac.2017.04.005 0141-8130/© 2017 Elsevier B.V. All rights reserved.