Fabrication and characterization of porous hyaluronic acid-collagen composite scaffolds

Hyaluronic acid (HA) plays a vital role in many tissues, influencing water content and mechanical function, and has been shown to have positive biological effects on cell behavior in vitro. To begin to determine whether these benefits can be accessed if HA is incorporated into collagen-based scaffolds for tissue engineering, HA-collagen composite matrices were prepared and selected properties evaluated. HA-collagen scaffolds were cross-linked with carbodiimide and loss rates of HA in culture medium assessed. Scaffold pore structures were evaluated by light and electron microscopy. Adult canine chondrocytes were grown in selected HA-collagen scaffolds to assess the effects of HA on cell behavior. Homogenous HA-collagen slurries were achieved when polyionic complexes were suppressed. HA was uniformly distributed through the scaffolds, which demonstrated honeycomb-like pores with interconnectivity among pores increasing as HA content increased. Virtually all of the HA added to the collagen slurry was incorporated into the composite scaffolds that underwent a 7-day cross-linking protocol. After 5 days in culture medium, the HA content in the scaffolds was 5-7% regardless of initial HA loading. After only 2 weeks in culture cartilaginous tissue was found in the chondrocyte-seeded HA-collagen scaffolds. This study contributes to the understanding of the effects of HA content, pH, and cross-link treatment on pore characteristics and degradation behavior essential for the design of HA-collagen scaffolds. The demonstration that these scaffolds can be populated by chondrocytes and support in vitro formation of cartilaginous tissue warrants further investigation of this material system for tissue engineering.