Bone substitute biomedical material of multi-(amino acid) copolymer: in vitro degradation and biocompatibility Hong Li • Yonggang Yan • Jie Wei • Jian Ma • Min Gong • Xiaoman Luo • Yunfei Zhang Received: 21 April 2011 / Accepted: 25 August 2011 / Published online: 6 September 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Degradable polymers with good mechanical strength as bone repair biomaterials have been paid more attention in biomedical application. In this study, a multi- (amino acid) copolymer consisting of 6-aminocaproic acid and five natural amino acids was prepared by a reaction of acid-catalyzed condensation. The results revealed that the copolymer could be slowly degradable in Tris-HCl solu- tion, and lost its initial weight of 31.9 wt% after immersion for 12 weeks, and the changes of pH value of Tris-HCl solution were in range from 6.9 to 7.4 during soaking. The compressive strength of the copolymer decreased from 107 to 68 MPa after immersion for 12 weeks. The proliferation and differentiation of MG-63 cells on the copolymer sig- nificantly increased with time, and the cells with normal phenotype extended and spread well on the copolymer surfaces. When the copolymer was implanted in muscle and bone defects of femoral cortex of dogs for 12 weeks, the histological evaluation confirmed that the copolymer exhibited excellent biocompatibility and more effective osteogenesis in vivo. When implanted into cortical bone defects of dogs, the copolymer could be combined directly with the natural bone without fibrous capsule tissue between implants and host bone. The results indicated that the multi-(amino acid) copolymer with sufficient strength, good biocompatibility and osteoconductivity had clinical potential for load-bearing bone repair or substitution. 1 Introduction Degradable polymers are a versatile class of functional materials and have been extensively investigated as bioma- terials for medical applications, which have shown great advantages when they are used as temporary substitutes, for example, bone defect fillers, bone fracture fixation, sutures, scaffolds for tissue engineering as well as controllable- released drug carrier [1–6]. Generally, biomedical polymer implants can be degradable in vivo and hence allow the host tissue growth till complete healing, while eliminate the need for the implant removal and can greatly reduce the pain for patients caused by the second operation. Ideally, the basic requirements for biodegradable polymers are biocompatible, and can be degradable at a controllable rate in accord with tissue growth. Meanwhile, the implants should not cause any excessive or chronic inflammatory response in vivo. Fur- thermore, they should provide sufficient mechanical prop- erties and decompose into non-toxic products [7–10]. Presently, degradable polymers for medical applications consist of synthetic polymers (such as polyvinyl alcohol, linearity aliphatic series polyester etc.) and natural polymers (such as collagen, chitin, and cellulose etc.). However, some synthetic polymers, for example polyesters, show poor mechanical strength in clinical applications [11, 12]. Other synthetic polymers of aliphatic series polyesters (such as PLA, PGA and PLGA) present good mechanical strength but sometimes show a collapse degradation manner after implanted in vivo, which leads to the incompatibility of H. Li  Y. Yan (&)  M. Gong  X. Luo  Y. Zhang School of Physical Science and Technology, Sichuan University, Chengdu 610064, People’s Republic of China e-mail: yan_yonggang@vip.163.com J. Wei (&) Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, People’s Republic of China e-mail: nic7505@263.net J. Ma Hospital of Stomatology, Tongji University, Shanghai 200072, People’s Republic of China 123 J Mater Sci: Mater Med (2011) 22:2555–2563 DOI 10.1007/s10856-011-4439-8