| Implementation of biological selectivity into electronic and optoelectronic devices plays an important role in the progress of biosensing technology. Enzymes as well as antibodies are used for molecular recognition in biosensing. Most biosensing devices implement these protein molecules on solid surfaces and rely on their ability to sense changes in physiochemical properties after the corresponding biomoleculer recognition. Full understanding of the technology to create such biosensing devices has not been yet accomplished. Several issues, such as the development of better materials and simpler processes for this technology, still pose a challenge. Also, preparations of biosensing surfaces that prevents non-specific interactions of biomolecules with the surface (or allows only the desired interactions) and that could be easily regenerated are highly desirable for biosensors and still need to be investigated.; In this work, a detailed investigation of the preparation of stable ligand functionalized gold nanoparticles and their effect on the emission of fluorescence for biosensing applications are presented. A simple stabilization technique involving the use of non ionic surfactant is employed to sustain the stability of the gold nanoparticles during the functionalization procedure. The ligand functionalized gold nanoparticles are used in a fluorescence-based biosensing scheme, where the specific biomolecular interactions between the selected ligand and fluorophore-labeled protein pair (biotin and Alexa™ 488-labeled anti-biotin) in solution were detected by means of optical absorption spectroscopy and fluorescence spectroscopy. A dramatic reduction in the emission of fluorescence from the fluorophores is observed when the anti-biotin molecules interacted with the biotin groups on the gold nanoparticles. Concomitantly, a “red-shift” in surface plasmon peak and broadening of the absorption spectrum of the gold nanoparticles are also observed. Later, when soluble biotin (with concentration larger than that of immobilized on the nanoparticles) is introduced into the solution, the anti-biotin molecules dissociated from the surface of the nanoparticles due to the competition for the binding sites of the protein resulting in the reversal of the signals observed previously. Kinetic parameters are obtained from the experimental data using appropriate models describing each process. |
