Polymeric cryogels are biocompatible, and their biodegradation is independent of oxidative radicals Akhilesh Kumar Shakya, 1,2 Rikard Holmdahl, 2 Kutty Selva Nandakumar, 2,3 Ashok Kumar 1 * 1 Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India 2 Department of Biochemistry and Biophysics, Medical Inflammation Research, Karolinska Institute, Stockholm 17177, Sweden 3 Adjunct Faculty of University of Arkansas for Medical Sciences, Little Rock, Arkansas Received 28 August 2013; revised 10 October 2013; accepted 15 October 2013 Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.35013 Abstract: Biocompatibility and in vivo degradation are two important characteristics of cell scaffolds. We evaluated these properties for four different polymeric macroporous cryogels, polyvinylcaprolactam, polyvinyl alcohol-alginate-bioactive glass composite, polyhydroxyethylmethacrylate–gelatin (pHEMA–gel- atin), and chitosan–agarose–gelatin in mice. All the cryogels were synthesized at subzero temperature and were implanted subcutaneously in C57Bl/10.Q inbred mice. Both local and sys- temic toxicities were negligible as determined by serum tumor necrosis factor a analysis and histology of surrounding tissues nearby the implants. Complete integration of cryogels into the surrounding tissues with neovascular formation was evident in all the mice. At the implantation site, massive infiltration of macrophages and few dendritic cells were observed but neutro- phils and mast cells were clearly absent. Macrophage infiltra- tions were observed even inside the pores of cryogel implants. To ascertain whether oxidative radicals are involved in the cryo- gel degradation, we implanted these gels in mice deficient for reactive oxygen species (ROS) production. Rapid gel degrada- tion was observed in the absence of ROS, and there was no sig- nificant difference in the biodegradation of these cryogels between ROS sufficient and deficient mice thereby excluding any major role for ROS in this process. Thus, we demonstrate the biocompatibility and ROS-independent biodegradable prop- erties of cryogels that could be useful for tissue-specific tissue engineering applications. V C 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A:000–000, 2013. Key Words: cryogel, biocompatibility, degradation, toxicity, host tissue response How to cite this article: Shakya AK, Holmdahl R, Nandakumar KS, Kumar A. 2013. Polymeric cryogels are biocompatible, and their biodegradation is independent of oxidative radicals. J Biomed Mater Res Part A 2013:00A:000–000. INTRODUCTION Damage and destruction to mammalian organs or tissues may be restored by transplantation of organs from one indi- vidual to another or performing surgical reconstruction by transferring tissue from one site to other within the host. Although these therapies are efficient, they are associated with major limitations like shortage of organ donors, graft rejection, and severe side effects due to transplantation. 1,2 To overcome these limitations, tissue engineering offers via- ble solutions for restoration of damaged tissues without any need for organ transplantation by developing biological sub- stitutes. 3 Mainly, it involves in vitro culture of mammalian cells over a scaffold for attachment, proliferation, migration, and differentiation of cells in a three-dimensional (3D) milieu and reimplanted into the recipients. Therefore, for proper growth and maintenance of cells, a 3D scaffold is needed and the selection of an appropriate scaffold is a pri- mary requirement in tissue engineering. The cell scaffolds should be mechanically stable, biodegradable, biocompatible, and porous with good interconnectivity for proper growth and maintenance of these cells. Thus, several factors are important while designing scaffold materials for their use in biomedicine. Biodegradable implantable polymers have the advantage of avoiding a permanent and chronic immune response, as well as removal surgery complications. 4 Hence, in vivo eval- uation of biocompatibility of biomaterials is an important aspect in tissue engineering research. Early in vivo assess- ment procedures are used for the determination of general biocompatibility of newly developed materials including general tissue responses against implants to gain initial knowledge before developing a final product. 5 Various bio- materials such as ceramics, composite, and polymers were assessed earlier for the development of 3D scaffolds, 6 which were mainly synthesized by solvent-casting particulate leaching, 7 gas foaming, 8 fiber meshes/fiber bonding, 9 phase Correspondence to: K. S. Nandakumar; e-mail: nandakumar.kutty-selva@ki.se and Ashok Kumar; e-mail: ashokkum@iitk.ac.in Contract grant sponsor: Swedish research council grant; contract grant number: Dnr. 348–2008-6007, KA Wallenberg foundation and the European Community’s Framework programs under grant agreements Neurinox (Health-F2-2011-278611) and the IMI program BeTheCure. Contract grant sponsor: Department of Biotechnology (DBT), and Department of Science and Technology (DST), Ministry of Science & Technol- ogy, Government of India (to AK) V C 2013 WILEY PERIODICALS, INC. 1