Development of label-free plasmonic Au-TiO2 thin film immunosensor devices

• Published in: Materials Science & Engineering C Vol. 100; pp. 424 - 432
• Main Authors: Barbosa, Ana I., Borges, Joel, Meira, Diana I., Costa, Diogo, Rodrigues, Marco S., Rebelo, Rita, Correlo, Vitor M., Vaz, Filipe, Reis, Rui L.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.07.2019; Elsevier BV
• Subjects: Antibodies; Antibody immobilization; Etching; Exposure; Gold; Immobilization; Immunoassay; Immunoglobulin G; Immunosensor; Immunosensors; Localized surface plasmon resonance; Magnetron sputtering; Materials science; Monolayers; Nanoparticles; Nanoplasmonic Au-TiO2 thin films; Plasma etching; Plasma treatment; Red shift; Sensitivity enhancement; Thin films; Titanium dioxide; Antibody immobilization; Plasma treatment; Localized surface plasmon resonance; Immunosensor; Nanoplasmonic Au-TiO2 thin films
• ISSN: 0928-4931; 1873-0191
• DOI: 10.1016/j.msec.2019.03.029

This work reports on the development of a label-free immunosensor technology, based on nanoplasmonic Au-TiO2 thin films. The Au-TiO2 thin films were prepared by cost-effective reactive DC magnetron sputtering, followed by a thermal annealing procedure. The latter promoted the growth of the Au nanoparticles throughout the TiO2 matrix and induced some morphological changes, which are the base for the immunosensor device functionality. A posterior plasma etching treatment was required to partially expose the nanoparticles to the biological environment. It gave rise to a 6-fold increase of the total area of gold exposed, allowing further possibilities for the sensor sensitivity enhancement. Experimental results demonstrated the successful functionalization of the films' surface with antibodies, with the immobilization occurring preferentially in the exposed nanoparticles and negligibly on the TiO2 matrix. Antibody adsorption surface coverage studies revealed antibody low affinity to the film's surface. Nevertheless, immunoassay development experiments showed a strong and active immobilized antibody monolayer at an optimized antibody concentration. This allowed a 236 signal-to-noise-ratio in a confocal microscope, using mouse IgG and 100 ng/ml of Fab-specific anti-mouse IgG-FITC conjugated. Label-free detection of the optimized antibody monolayer on Au-TiO2 thin films was also tested, revealing an expected redshift in the LSPR band, which demonstrates the suitability for the development of cost-effective, label-free LSPR based immunosensor devices. [Display omitted] •Au-TiO2 thin films were prepared by sputtering plus thermal annealing.•Plasma etching treatment exposes the Au nanoparticles to environment.•Uncovered Au nanoparticles were functionalized with antibodies.•Label-free plasmonic based immunosensor device was developed.