Biomimetic Apatite Formation on Chemically Modified Cellulose Templates

Abstract

Biomimetic precipitation of calcium phosphate phases (Ca-P) from simulated body fluid (1.5 SBF) on the biopolymer cellulose was studied. The basic crystallization behavior was investigated using highly oriented Langmuir-Blodgett films of cellulose activated in Ca(OH) 2 solution. Using transmission electron microscopy it was shown that the activated cellulose triggered the formation of nano-cyrstalline Ca-P phases, whereas spherical nano-aggregates were found on pure cellulose films. The formation of two different Ca-P phases, i.e. octa calcium phosphate (OCP) and hydroxy carbonated apatite (HCA) was found after 7 days in 1.5 SBF. Ca(OH) 2 pretreated 3D cellulose fabrics (Lyocell ® ) were homogeneously covered with a 30 µm thick HCA layer after soaking in 1.5 SBF for 21 days. Thus, chemically pretreated cellulose fabrics with adjustable porosity are considered to be capable to build up novel scaffold architectures for tissue engineering.

Synthesis and Characterization of Ionic Block Copolymer Templated Calcium Phosphate Nanocomposites

“…By changing the ionic character of copolymer micelles in solution, we can vary the formation and composition of the inorganic phase on copolymer micelles in aqueous solutions. Appropriate copolymer design and synthesis and the use of gel-forming self-assembling copolymers, makes possible the formation of macro-sized ordered networks of spherical nanocomposites for a bottom-up approach to materials design, while most previous work has focused on mineralizing the surface of bulk polymers [4][5][6] or forming sub-micron aggregates of organic-inorganic nanocomposites. 7,15 The nanocomposites formed were characterized by electron microscopy, X-ray scattering, and advanced solid-state NMR.…”

“…Precipitation of calcium phosphate into the copolymer gel matrix was achieved using aqueous solutions of ammonium dihydrogen phosphate (NH 4 In order to analyze the growth of the ceramic coatings on the micelles, a less-concentrated 0.5 wt% polymer solution (below the critical gel concentration) was also tested. To prepare this sample, 10 mL of the pH 3.0 calcium phosphate solution was mixed with an equal amount of 1.0 wt% pentablock copolymer solution yielding a solution of 0.5 wt% pentablock copolymer, and half of the saturated calcium phosphate ion concentration.…”

“…For reference, the spectrum of pure Ca(H 2 PO 4 ) 2 is shown in Fig. 7e, f; it exhibits two signals due to chemically inequivalent H 2 PO 4 2 ions in the crystal structure. The Pluronic 1 F127-phosphate has a broader line shape as compared to the pentablock-phosphate, which suggests that the former exists in a more disordered environment.…”

“…4 After treating highly oriented trimethylsilylethercellulose (TMS-cellulose) fibers with a supersaturated Ca(OH) 2 solution and exposing it to simulated body fluid, Muller et al observed directed calcium phosphate precipitation on the surfaces of the cellulose fibers. Starting with an initial cellulose fiber diameter of about 20 mm, these coated fibers reached a final diameter of over 90 mm.…”

Photoluminescence of annealed biomimetic apatites

“…It was shown that the formation of a bonelike HCA surface layer and the resultant bonebonding ability of an implant can be evaluated by testing the material in an acellular simulated body fluid (SBF) with ion concentrations nearly equal to those of the inorganic part of human blood plasma [3,4]. Since SBF is supersaturated with respect to HCA at 37°C, the solution has been widely used for precipitation of nano-scale calcium phosphate powders and for biomimetic coating of implant surfaces under mild conditions [5][6][7][8].…”