Introduction

The delivery of nucleic acids is a powerful technique to regulate cellular processes that has profound implications for regenerative medicine. Nucleic acid delivery is most widely thought of as delivery of a gene to induce expression of a specific factor. This approach is highly versatile, insofar as it can readily target secreted factors (e.g. growth factors), membranous proteins (e.g. receptors), or intracellular proteins (e.g. transcription factors). Expression can potentially be modulated through the promoter, with control provided by soluble, inductive factors, or be restricted to specific cell populations. The alternative to delivering nucleic acids to induce expression of target genes is to reduce or block expression. The discovery of RNA interference (RNAi) has identified a powerful mechanism for nucleic acid delivery to catalyze the degradation of target mRNA. Similarly, oligonucleotides can bind to a complementary strand of mRNA (antisense) to terminate translation or act as decoys that bind to transcription factors and limit their ability to influence transcription. The delivery of nucleic acids has the potential to either promote or inhibit virtually any cell process; however, a major challenge to capitalizing on this potential lies in the need for effective delivery systems.