easyNanofab: Large Area Fabrication for Bionanotechnology, Plasmonics and Molecular Nanoscience

Probably the most important outcome of the explosion of activity in nanoscience and technology over the past couple of decades has been the emergence of powerful new tools for studying and analyzing materials and molecules at very high sensitivity. However, many of these tools rely upon the availability of nanostructured materials - materials consisting of precisely engineered structures - that are difficult to make, and require the availability of expensive and complex instrumentation. For many applications involving molecular and biological materials, these difficulties are daunting. A good illustration is the development of nanooptical techniques for biological analysis: there are now some extraordinarily powerful methods available, that use phenomena such as the plasmonic enhancement of optical activity, and surface enhanced Raman scattering, to make biological detection possible at very high sensitivities. However, the potential for uptake of these methodologies in society (for example, in the National Health Service) is limited unless inexpensive methods can be found for the precise fabrication of miniaturized structures over large areas. The goal of this project is to make that possible, be developing a fast, inexpensive approach to the fabrication of hybrid metal-biomolecule structures. Our preliminary work shows that simple monolayer chemistries can be developed and used in conjunction with interference techniques - that require only a laser and a few lenses - to provide exquisite control over surface structure on length scales down to a few tens of nm - approaching the dimensions of single biomolecules. We aim to try to build a sensor capable of detecting small amounts of DNA that could be the basis for a cheap chip-based screening technique that might be introduced quickly an inexpensively in the NHS.

Although there are many potential applications for the proposed research, we forsee particularly good potential for impact in molecular diagnostics. There has been enormous interest in the development of chip-based methods for the diagnosis of disease, and methods for DNA detection are potentially very important. However, such methods are expensive and also have very limited sensitivity, meaning that polymerase chain reaction (PCR) methods must be used to amplify DNA prior to analysis. This is not only slow, but also problematic in a clinical context, where interfering DNA (resulting from the complex source material - blood, sputum - and the high probabilities of contamination) also becomes amplified, leading to an assay outcome that is often difficult to interpret. A method that would facilitate the analysis of clinical samples without recourse to PCR would be very attractive. Plasmonic effects can yield enormous enhancements of optical signals (fluorescence, or surface enhancement of Raman spectral signatures from dyes) - ranging from six to eight orders of magnitude for nanoparticulate gold. Such enhancements are equivalent to the amplification that is achieved biochemically using PCR. Our goal is the development of a simple chip-based assay that could be used easily with readily available equipment. This would take the form of a glass slide coated with a high density of plasmonically active structures - like the one in figure 4 but consisting of Au rather than Ti dots - each of which was functionalised with probe DNA (a single stranded oligonucleotide that would etect a specific complementary sequence if present in the test specimen). Because of the simplicity and speed inherent in the IL process, we believe that such specimens could be produced very cheaply. Because IL was originally developed as a tool for semiconductor fabrication - ie for exposure of industrial scale wafers - it is ideally suited to a manufacturing operation. Detection of optical signals from hole and dot arrays with LSPR is readily achieved using a UV-visible spectrometer. Read-out could thus be accomplished inexpensively on instrumentation that is readily available in hospital clinical medicine departments. We believe it is not unreasonable to hope that our work, if successful, offers great promise for translation into clinical analysis. The collaboration with Prof Charles is vital to the success of the science contained in the proposal and also the later exploitation of the technology; he has extensive experience of working with the health service, many years experience of the development of DNA arrays, and an enormous amount of experience of the biomedical industry. He was head of Molecular Pharmacology at the Wellcome Research Laboratories, and as an academic, was co-founder and board member of Arrow Therapeutics, a university spin-out company focussing on anti-infective drug discovery. This experience will be vital to the future exploitation of the research proposed here. If the academic work described in this proposal is successful, the most appropriate route forward would probably be to seek follow-on funding (either from EPSRC or TSB) to carry out work aimed at developing the nanofabricated diagnostic devices into a user-friendly format that would facilitate initial trial work in collaboration with clinical chemists working in the NHS (ideally, in local hospitals). We believe that the basic technology would be essentially addressed in the programme of work described here; the development stage would focus more on converting the methodology into a format that was usable in clinical diagnosis. The first stage to commercialisation may well be a small spin-out company. However, we would ultimately need to sell the technology to a larger organisation capable of taking the technology forward and developing manufacturing processes.