Polyelectrolyte multilayer coating of 3D scaffolds enhances tissue growth and gene delivery: non-invasive and label-free assessment.

Layer-by-layer (LbL) deposition is a versatile technique which is beginning to be be explored for inductive tissue engineering applications. Here, it is demonstrated that a polyelectrolyte multilayer film system composed of glycol-chitosan (Glyc-CHI) and hyaluronic acid (HA) can be used to coat 3D micro-fabricated polymeric tissue engineering scaffolds. In order to overcome many of the limitations associated with conventional techniques for assessing cell growth and viability within 3D scaffolds, two novel, real-time, label-free techniques are introduced: impedance monitoring and optical coherence phase microscopy. Using these methods, it is shown that LbL-coated scaffolds support in vitro cell growth and viability for a period of at least two weeks at levels higher than uncoated controls. These polyelectrolyte multilayer coatings are then further adapted for non-viral gene delivery applications via incorporation of DNA carrier lipoplexes. Scaffold-based delivery of the enhanced green fluorescent protein (EGFP) marker gene from these coatings is successfully demonstrated in vitro, achieving a two-fold increase in transfection efficiency compared with control scaffolds. These results show the great potential of Glyc-CHI/HA polyelectrolyte multilayer films for a variety of gene delivery and inductive tissue engineering applications.