Peptide nucleic acid (PNA) hybridization part I application to nanoscale sensors part II self-assembly

Peptide nucleic acid (PNA) assemblies are interesting scaffolds for the fabrication of nanomaterials relevant to the diagnosis and treatment of disease. PNA is a synthetic DNA analog that contains the nucleic acid bases adenine, cytosine, guanine, and thymine on a neutral peptide-like backbone. Due to its uncharged structure, a PNA strand can hybridize to a complementary DNA or LNA (locked nucleic acid) strand with higher affinity than an analogous DNA sequence. LNA is a synthetic DNA analog in which the 2\u27-oxygen is linked to the 4\u27-carbon via a methylene unit, rendering the monomer more conformationally stable than that of DNA and with extremely high hybridization affinity. The PNA/LNA duplex is particularly stable in that a short sequence of only six base pairs has a sharp melting curve well above room temperature. This robust PNA/LNA duplex is being employed in the temperature-controlled selective functionalization of arrayed nanoplates and nanowires. The ultimate goal of this technology is for the detection of microRNAs (miRNAs), short strands of RNA that combine with and inhibit complimentary messenger RNA. MicroRNAs are involved in the regulation of many cellular processes, and miRNA expression has been linked to certain disease states in various types of cancers. The goal is to rapidly detect the presence of many different miRNA sequences simultaneously, in order to investigate the roles of specific miRNAs in disease states and to diagnose early cancerous disease states in a clinical setting. Another interesting property of PNA is its ability to hybridize to other PNA strands in a parallel (as well as antiparallel) fashion. We have designed a PNA sequence that exploits this parallel hybridization by self-assembling into nanoparticles. The potential application of these assemblies as multivalent carriers of therapeutic peptides is being explored. This work describes the successful cell uptake and endosomal release of a peptide-PNA sequence based on its ability to assemble into particles that display multiple copies of an endocytosis/release-mediating peptide. This work also describes the successful formation of nanorings with the substitution of a longer peptide-PEG linker sequence, thereby increasing the versatility of the nanoring scaffold for ligand presentation