Controlled delivery of DNA-polyethylenimine particles from collagen matrices for tissue engineering

Collagen is a triple helical protein that self assembles into strong, rope-like fibers that provide mechanical stability to tissue throughout the body. Collagen can be extracted from tissues and processed into fibers, films, gels and sponges for use in tissue engineering. In this study, collagen is used as both a scaffold for cellular in-growth and as a delivery device for DNA-polyethylenimine particles. Polyethylenimine (PEI) is an ideal vector for gene delivery. It is a charged polymer which condenses DNA into spherical particles which are readily endocytosed by cells.; This study attempts to build upon previous work in gene delivery from collagen matrices. PEI-DNA was shown here to be more effective at inducing in vitro transfections than naked DNA. This result allows for far lesser amounts of DNA to be used than in previous studies. Furthermore, interactions (presumed to be electrostatic) were observed between the collagen films and the DNA-PEI which increase the transfection efficiency. Optimal conditions were identified for soaking DNA-PEI particles into collagen films. This process is simpler and quicker than other published procedures which involve freeze drying DNA-PEI seeded scaffolds or covalently linking DNA-PEI to biomaterial surfaces.; Four simple fabrication variables involved in creating DNA-PEI soaked collagen films were studied in depth for their effects on cell proliferation and transgene expression. The variables were: (1) DNA-PEI soak volume, (2) DNA-PEI soak volume, (3) collagen film thickness, (4) UV crosslinking. The variables were examined in a multifactorial study which tested all possible variable combinations, identifying complex interactions which affected both cell number and transgene expression.; Based on the results of the multifactorial study, long term transgene expression studies and DNA loading data, a picture became somewhat clear about how the overall system is working. DNA-PEI soaked films can be fabricated to achieve high levels of early transgene expression with limited cellular in-growth, or conversely, long term transgene expression and increased cell proliferation. This work leads the way for the creation of implant coatings and tissue engineering scaffolds which can modulate transgene expression profiles tailored for specific applications.