Oligonucleotide biosensing applications of distributed feedback lasers and silver nanoparticles : using lasers and silver to find broken hearts

Student thesis: Doctoral Thesis

Abstract

Point of Care devices have helped extend the reach of medical services and improved turnaround times for many traditional laboratory tests. Their development necessitates the development and miniaturisation of novel sensing schemes for rapid monitoring of nanoscale biochemical interactions. Many pathologies such as cardiovascular disease present physical biomarkers in patient samples. By probing at the surface of a thin-film, organic semiconductor, distributed feedback laser a novel biosensing scheme utilizing oligonucleotides has been studied and is reported in this thesis. Using an optical approach, Truxene and BBEHP-PPV DFB lasers are put to the test, assessing their sensing capabilities using laser wavelength shift as the transducing method. Bulk sensitivities of 23 nm.RIU-1 (Tr) and 21 nm.RIU-1 (BBEHP_PPV) are observed. The Tr-DFB lasers demonstrated higher sensitivity in bulk superstrate and surface material adsorption tests.As an alternative to wavelength shift, silver nanopa rticle labelled oligonucleotide targets were used to influence the threshold fluence required for OS-DFB lasers to achieve laser action. Using this method, a successful immobilisation strategy for oligonucleotide probes on the surface of an OS-DFB laser, for the first time to our knowledge, was confirmed. Target AgNPs were detected by SERS with a 20x objective on a Raman microscope (Gloucestershire, UK) equipped with an excitation wavelength of 514.5 nm and comparative concentration dependant effects on OS-DFB laser threshold fluence down to 11.5 pM. The capture of 40-45 nm AgNP surface bound target oligonucleotides via hydrogen base pair bonding to corresponding probes on the OS-DFB laser surface was shown to be selective down to individual nucleotide. Such detection limits are within diagnostic significance and the protocols have scope for modification to suit a multitude of different applications.The novel demonstration of a molecular attachment strategy for oligonucleotidebiosensor probes to an OS-DFB laser surface and the detection of AgNPs bound by complementary strand hybridisation using SERS and a comparative threshold fluence detection method are of particular note. The text within explores the characteristics of these sensing regimes and compares and contrasts the biosensing technologies involved.
Date of Award8 Apr 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorNicolas Laurand (Supervisor) & Glenn Burley (Supervisor)

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