In vitro characterization of a calcium sulfate/PLLA composite for use as a bone graft material

Abstract

A study was conducted to characterize the dissolution, morphology, and chemical composition of a calcium sulfate/poly (L-lactic acid) (CS/PLLA) composite material before and after immersion in simulated body fluid (SBF). Twelve groups of experimental samples were prepared by coating CS pellets 1, 2, 3, or 4 times with one of three concentrations of a PLLA solution and wrapping them in mesh; CS pellets for use as controls were similarly prepared but not coated. The PLLA coating added from 1 to 22% to the weight of experimental pellets; scanning electron microscopy revealed that the coating thickness ranged from 2 to 50 microm depending on the concentration of the coating solution and the number of coatings. All samples were immersed in SBF for up to 97 days. After immersion, the experimental coatings thinned out, small cracks and holes formed in the coating, and the coating became roughened. Mean dissolution rates for each of the 12 CS/PLLA groups were significantly lower than those of uncoated CS pellets; among CS/PLLA groups, dissolution rates varied according to concentration of the coating solution and number of coatings. The half-life of pure CS pellets was 19 days whereas the half-life of CS/PLLA composite pellets ranged from 30 to 70 days. X-ray microprobe analysis of experimental pellets after immersion in SBF revealed that mineralization occurred in the CS portion of these pellets as well as on the coating; most of the mineral was calcium phosphate, most of which was on the coating. Further studies will be required to confirm this composite's promise as a clinically effective osteoconductive material.

Vancomycin Containing PLLA/β-TCP Controls MRSA In Vitro

“…We found pore structure, size, internal volume, and the apparent density of the composites were similar to those previously reported [31]. The VC was coated with PLLA by the dip-coating method to control vancomycin release.…”

Modulation of the resorption and osteoconductivity of α-calcium sulfate by histone deacetylase inhibitors

“…The rapid resorption of CS cement does not provide the proper condition for bone regeneration, while calcium phosphate apatites or synthetic polymers such as PLLA resorb so slowly that replacement by new tissues is delayed. Thus, CS has been combined with other materials, including bone particles, tooth ash, synthetic polymers, and calcium phosphate apatites, to overcome the shortcomings of each individual material [1,2,4,6,19,[22][23][24].…”

“…The dissolution of CS in an SBF was examined by measuring the amount of calcium released from CS disks into the SBF [6]. CS was incubated in an SBF with inorganic ion concentrations (142 mM Na þ , 1.5 mM Mg 2þ , 2.5 mM Ca 2þ , 147.8 mM Cl À , 4.2 mM HCO 3 À , 1 mM PO 4 À , 0.5 mM SO 4 2À ) nearly equal to those of human blood plasma.…”

“…Recently, CS was reported to modulate the expression of genes associated with osteoblastic phenotypes [5]. Although these characteristics favor the use of CS as a bone regenerative biomaterial, CS unfortunately also has poor mechanical properties and a resorption rate that is too fast for some applications [1,2,6].…”

Calcium sulfate

“…A timed-release composite pellet, of the same size range, comprising 4% PLLA and 96% CS had a half-life of 68 days under the same conditions. While we have tested several formulations that degrade at very different rates (Mamidwar et al, 2006b) we have extensively tested the above noted nanocomposite form and found it to have a half-life of about 2 months and a full degradation time of about 4 months in vivo (Mamidwar et al, 2006a). We feel that this formulation may be appropriate for craniofacial defects where dental implants are to be placed, such as extraction sockets and sinus augmentation sites.…”