Novel molecular design and dielectrophoretic manipulation for enhancing biosensors

Single nucleotide polymorphisms (SNPs), being the most abundant type of human polymorphisms and relatively well categorised, make good markers to indicate genes that underlie diseases. Therefore there is great interest in the development of biosensors capable of SNP genotyping. A novel biosensor based on the well-studied DNA Holliday junction, designed to detect single base mutations in an unlabelled target sequence through a simple bait-and-switch mechanism has been developed, and applied to both synthetic and clinically-extracted samples. A second mode of enhancing detection sensitivity is through direct manipulation of matter by dielectrophoresis (DEP). DEP arises from the creation of a force acting on an electrically polarized particle when subjected to a non-uniform electric field. Solvated particles can respond to this force by either moving towards (positive DEP) or away (negative DEP) from the electrodes generating the electric field. The technique can be used to manipulate many biological particles, opening up new opportunities for nucleic acid based biosensing devices. I aim to develop a RNA hybridization probe functionalised on a microelectrode, capable of rapid detection and DEP based target sorting. The DEP collection and repulsion of ribosomal RNA and CdSe Quantum Dots on microfabricated interdigitated Au electrodes were observed using TIRF microscopy, and measured as a function of the strength and frequency of the applied electric field.