title: Combinatorial Design of Hydrolytically Degradable, Bone-like Biocomposites Based on PHEMA and Hydroxyapatite.
abstract: With advantages such as design flexibility in modifying degradation, surface chemistry, and topography, synthetic bone-graft substitutes are increasingly demanded in orthopedic tissue engineering to meet various requirements in the growing numbers of cases of skeletal impairment worldwide. Using a combinatorial approach, we developed a series of biocompatible, hydrolytically degradable, elastomeric, bone-like biocomposites, comprising 60 wt% poly(2-hydroxyethyl methacrylate-co-methacrylic acid), poly(HEMA-co-MA), and 40 wt% bioceramic hydroxyapatite (HA). Hydrolytic degradation of the biocomposites is rendered by a degradable macromer/crosslinker, dimethacrylated poly(lactide-b-ethylene glycol-b-lactide), which first degrades to break up 3-D hydrogel networks, followed by dissolution of linear pHEMA macromolecules and bioceramic particles. Swelling and degradation were examined at Hank's balanced salt solution at 37 °C in a 12-week period of time. The degradation is strongly modulated by altering the concentration of the co-monomer of methacrylic acid and of the macromer, and chain length/molecular weight of the macromer. 95% weight loss in mass is achieved after degradation for 12 weeks in a composition consisting of HEMA/MA/Macromer = 0/60/40, while 90% weight loss is seen after degradation only for 4 weeks in a composition composed of HEMA/MA/Macromer = 27/13/60 using a longer chain macromer. For compositions without a co-monomer, only about 14% is achieved in weight loss after 12-week degradation. These novel biomaterials offer numerous possibilities as drug delivery carriers and bone grafts particularly for low and medium load-bearing applications.
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States ; College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Jijun
authors.initials: J
authors.lastname: Huang
authors.forename: Dacheng
authors.initials: D
authors.lastname: Zhao
authors.forename: Smit J
authors.initials: SJ
authors.lastname: Dangaria
authors.forename: Xianghong
authors.initials: X
authors.lastname: Luan
authors.forename: Thomas G H
authors.initials: TG
authors.lastname: Diekwisch
authors.forename: Guoqing
authors.initials: G
authors.lastname: Jiang
authors.forename: Eduardo
authors.initials: E
authors.lastname: Saiz
authors.forename: Gao
authors.initials: G
authors.lastname: Liu
authors.forename: Antoni P
authors.initials: AP
authors.lastname: Tomsia
keywords: hydrolytic degradation; macromer; pHEMA