Fast Setting CPC-Chitosan Composite: Mechanical Properties and Dissolution Rates
Limin Sun, Hockin D. Xu, Shozo Takagi, Laurence C. Chow
Calcium phosphate cement (CPC) can self-harden in vivo to form hydroxyapatite with excellent osteoconductivity. In recent studies, CPC-chitosan composites were developed with high mechanical strength and washout resistance. The objectives of the present study were to optimize the setting time and mechanical properties of a CPC-chitosan composite by tailoring the chitosan content, and to evaluate the bioresorbability by using an in vitro dissolution model. Six chitosan mass fractions were tested: 0 %, 10 %, 15 %, 20 %, 25 % and 30 %. Specimens were immersed in solutions with pH ranging from 3.5 to 5 to simulate the acidic environments produced by osteoclasts in vivo. Dissolution was measured as the fraction of mass loss vs. immersion time from 7 d to 28 d. The CPC-chitosan composite with 20 wt% chitosan had a setting time (mean sd; n = 4) of (13.5 0.6) min, significantly less than (87.5 6.5) min for CPC control without chitosan (p 0.1). The dissolution rates (fraction of mass loss per day, wt%/d) were 1.05 for CPC control and 1.08 for CPC-chitosan. In summary, a CPC-chitosan composite was developed with fast-setting and a flexural strength three-fold of that of CPC control without chitosan. Both materials were soluble in acidic environments, indicating that adding chitosan did not compromise the bioresorbability of CPC. The strong and resorbable CPC-chitosan composite may be useful in moderate stress-bearing craniofacial and orthopedic repairs.