Collagen-coated polylactide microcarriers/chitosan hydrogel composite: Injectable scaffold for cartilage regeneration

A novel structure of injectable scaffold is designed and fabricated by combining collagen‐coated polylactide (PLA) microcarriers and crosslinkable chitosan hydrogel. The collagen‐coated PLA microcarriers were firstly mixed with the hydrogel precursor, a thickening agent of konjac glucomannan (KGM), and redox initiators of ammonium persulfate and tetramethylethylenediamine (TMEDA). The mixture was then injected into a mold and incubated at 37°C to obtain the composite scaffold. The hydrogel can deliver the collagen‐coated PLA microcarriers to the desired site and, after gelation, will prevent them from uncontrolled movement. On the other hand, the collagen‐coated PLA microcarriers can substantially enhance the mechanical properties of the composite system. It was found that the microcarriers suspended stably in 0.6% KGM/1% chitosan derivative (CML) solution at 37°C at least for 15 min. The dynamic elastic modulus (G′) of the composite scaffold increased along with the increase of the microcarrier content. G′ of the composite scaffold with 10% microcarriers was measured as 0.87–2.15 MPa at a frequency range of 0.1–100 rad/s, which was 120–90 times higher than that of its hydrogel system alone (12.1–24.4 kPa). In vitro culture of chondrocytes/composite scaffold showed that the cell metabolic activity increased rapidly before day 9, then leveled off. Cells in the hydrogel could attach and grow on the surface of the collagen‐coated PLA microcarriers to form confluent cell layers after days 9–12. These features make the composite scaffold to be injectable and applicable in either tissue engineering, or regenerative medicine, and in particular, in orthopaedics. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008