Supported Lipid Bilayer as Biosensing Platform

Abstract

Abstract Supported Lipid Bilayer as Biosensing Platform

Woosung Hwang Department of Chemistry The Graduate School Seoul National University

It is difficult to continuously observe the behaviors of nanosized materials with existing equipment and experimental methods. Using supported lipid bilayers(SLB) can solve these problems. SLB is an artificial cell membrane that retains the important biological characteristics of cell membranes, such as fluidity and affinity with cell membrane components, and is easy to assemble into a desired form. In this thesis, new methods for observing the behavior of optically stable plasmonic metal nanoparticles using a two-dimensional SLB as a platform are presented and obtaining meaningful results. SLB platform has fluidity, and a number of metal nanoparticles can be bind to its surface. The movement of metal nanoparticles bound to the surface is observed in real time. Specific behavior of surface-modified metal nanoparticles can induced by external stimuli. The plasmonic metal nanoparticles have a property that the scattering intensity is amplified when they are located at a certain distance or less. Therefore, the phenomenon that metal nanoparticles are bonded by external stimuli can be observed and tracked in real time. In this thesis, biomaterial detection methods using two dimensional support lipid bilayers and plasmonic metal nanoparticles will be presented. In addition, it has been shown that the nanoparticle behavior can be controlled by various surface modifications, and it is confirmed that the SLB is suitable as the platform of the biosensor. Research has been conducted on how to detect viruses quickly and accurately for decades. Detection methods using nanoparticles have also been proposed and studied. Various properties of nanoparticles have been used for detection. Especially, the unique nature of metal nanoparticles due to localized surface plasmons enables the detection of viruses through a variety of methods. The ability to easily modify a variety of ligands and biochemical materials also served as an advantage as a biosensing material. In Chapter 1, we detected the virus by attaching the antibody-coated nanoparticles to the surface of the supported lipid bilayer. We confirmed that the degree of near-field interaction between nanoparticles differs according to the concentration of virus through dark-field microscopy. It is experimentally demonstrated that viruses of unknown samples can be detected through this. The development of semiconductor-based computing devices has transformed modern society. Molecular computing has been proposed as a complementary technology, but its impact is still insignificant. Conventional methods rely heavily on DNA with good practicality and general applicability. Numerous nucleic acid-based calculations from logic gates to neural networks have been demonstrated. However, the practical application of DNA-based devices beyond proof-of-concept has not been driven by many limitations. In Chapter 2, we demonstrated the possibility of a new type of information processing platform by combining the chemical nature of the functional groups introduced into the nanoparticles and the fluidity of the SLB. It was confirmed that the nanoparticles on the SLB were assembled and decomposed by the metal ion and the external environment. Multiplexed real-time analysis on multiple interacting molecules and particles is needed to obtain information on binding patterns between multiple ligands and receptors, specificity of bond formations and interacting pairs in a complex medium, often found in chemical and biological systems, and difference in binding affinity and kinetics for different binding pairs in one solution. In particular, multiplexed profiling of microRNA (miRNA) in a reliable, quantitative manner is of great demand for the use of miRNA in cell biology, biosensing and clinical diagnostic applications, and accurate diagnosis of cancers with miRNA is not possible without detecting multiple miRNA sequences in a highly specific manner. In chapter 3, we report a multiplexed molecular detection strategy with optokinetically (OK) coded nanoprobes (NPs) that show high photostability, distinct optical signals and dynamic behaviors on a SLB (OK-NLB assay). Metal NPs with three distinct dark-field light scattering signals [red (R), green (G) and blue (B)] and three different target miRNA halfcomplements were tethered to two dimensionally fluid SLB with mobile (M) or immobile (I) state. In situ single-particle monitoring and normalized RGB analysis of the optokinetically combinatorial assemblies between three M-NPs and three I-NPs with dark-field microscopy (DFM) allow for differentiating and quantifying 9 different miRNA targets in one sample. The OK-NP-based assay enables simultaneous detection of multiple miRNA targets in a highly quantitative, specific manner within 1 hour, and can be potentially used for diagnosis of different cancer types. We validated the OK-NLB assay with single-base mismatched experiments and HeLa cell-extracted total RNA samples by comparing the assay results to the quantitative reverse transcription polymerase chain reaction (qRT-PCR) result.

Keywords : Supported Lipid Bilayer(SLB), Nanoparticle, Biosensor, Virus Detection, Ligand Computing, miRNA Detection Student number : 2014-22419