In vitro release kinetics of proteins from bioactive foams.

This study describes an approach to obtaining 3-D scaffolds for tissue engineering that allows the incorporation and release of biologically active proteins to stimulate cell function. Laminin was adsorbed on the textured surfaces of binary 70S30C (70 mol % SiO(2), 30 mol % CaO) and ternary 58S (60 mol % SiO(2), 36 mol % CaO, 4 mol % P(2)O(5)) foams. The covalent bonds between the binding sites of the proteins and the ligands on the scaffolds' surfaces did not denaturate the proteins. In vitro studies show that the foams modified with chemical groups and coated with laminin were bioactive, as demonstrated by the formation of a crystalline hydroxy carbonate apatite (HCA) layer formed on the surfaces of the foams upon exposure to simulated body fluid (SBF). The release of proteins from the foams also was investigated. Sustained and controlled release from the scaffolds over a 30-day period was achieved. Laminin release from the bioactive foams followed the dissolution rate of the material network. These results suggest that bioactive foams have the potential to act as scaffolds for soft-tissue engineering with a controlled release of proteins that can induce tissue formation or regeneration.

Surface-modified 3D scaffolds for tissue engineering.

The aim of this work was to use sol-gel processing to develop bioactive materials to serve as scaffolds for tissue engineering that will allow the incorporation and release of proteins to stimulate cell function and tissue growth. We obtained organofunctionalized silica with large content of amine and mercaptan groups (up to 25%). The developed method can allow the incorporation and delivery of proteins at a controlled rate. We also produced bioactive foams with binary SiO(2)-CaO and ternary SiO(2)-CaO-P(2)O(5) compositions. In order to enhance peptide-material surface properties, the bioactive foams were modified with amine and mercaptan groups. These materials exhibit a highly interconnected macroporous network and high surface area. These textural features together with the incorporation of organic functionally groups may enable them to be used as scaffolds for the engineering of soft tissue.

Novel sol-gel bioactive fibers.

Bioactive fibers were produced using a sol-gel method. The rheological properties of two different sol compositions prepared from a mixture of TEOS, phosphorous alkoxide and calcium nitrate, or calcium chloride in a water-ethanol solution, are reported. The sols were extruded through a spinneret to produce continuous 10 microm-diameter fibers. Discontinuous fibers and fibrous mats were prepared by air-spraying the multicomponent sols. The sol-gel fibers were converted to the bioactive fibers by three different thermal treatments at either 600 degrees, 700 degrees, or 900 degrees C for 3 h. SEM, BET, EDX, and FTIR were used to characterize the morphology and structure of the fibers. The BET measured surface area of the fibers sintered at 900 degrees C was 0 m(2)/gm compared to a value of 200 m(2)/gm for a typical sol-gel-derived particle of similar composition. Both the continuous and discontinuous fibers exhibited in vitro bioactivity in a simulated body fluid.

Effect of crystallization on apatite-layer formation of bioactive glass 45S5.

The bioactive glass 45S5 was crystallized to 8-100 vol % of crystals by thermal treatments from 550-680 degrees C. The micro-structure of the glass-ceramics had a very uniform crystal size, ranging from 8 to 20 microns. Fourier-transform infrared (FTIR) spectroscopy was used to determine the rate of hydroxycarbonate apatite (HCA) formation that occurs on bioactive glass and glass-ceramic implants when exposed to simulated body fluid (SBF) solutions. Crystallization did not inhibit development of a crystalline HCA layer, but the onset time of crystallization increased from 10 h for the parent glass to 22 h for 100% crystallized glass-ceramic. The rate of surface reactions was slower when the percentage of crystallization was > or = 60%.