Microswimmer-driven agglutination assay

Lab-on-a-chip systems for point-of-care testing demonstrate a promising development towards more accurate diagnostic tests that are of extreme importance for the future global health. This work presents an agglutination assay performed in micrometer sized well using Janus PS/Ag/AgCl micromotors to enhance the interactions between goat anti-human IgM functionalized particles and Human IgM. The fabricated microwell chips are a suitable platform to analyze the interaction between different particles and to perform the agglutination assays. The interaction between active Janus particles and passive and functionalized particles is studied, as well as the influence of ions on the motion of the Janus particles. Agglutination assays are performed with and without the presence of Janus particles, and in different PBS concentrations. Once illuminated with blue light, passive SiO2 particles were effectively excluded from Janus particles, while SiO2 NH2 particles revealed attraction. In contrast, functionalized SiO2 NH2 Ab particles suspended in PBS did not show any interaction. It was found that the optimal working conditions for antibodies and Janus particles differed and, as a result, the Janus particles did not reveal a desirable interaction between the functionalized particles and IgM. Further experiments should be performed to find the proper conditions in which the antibodies and the Janus particles maintain their activities. It is believed that an effective interaction between the functionalized and Janus particles could be achieved by modifying the parameters that affect their interaction such as the zeta potential and the medium in which the assay is being performed. This preliminary work provides the first steps towards the development of a fully integrated lab on a chip system for point of care testing.:Abstract ........................................................................................................................ iii Acknowledgments.......................................................................................................... v Table of Contents .......................................................................................................... vi List of Tables ............................................................................................................. viii List of Figures ............................................................................................................... ix Abbreviations ................................................................................................................. x 1. Introduction ............................................................................................................ 1 1.1 In vitro diagnostic tests ........................................................................................ 1 1.1.1 Point-of-care tests ......................................................................................... 2 1.2 Agglutination assay .............................................................................................. 2 1.3 Lab-on-a-chip ....................................................................................................... 5 1.4 Self-propelled particles ........................................................................................ 6 1.4.1 Light-driven Ag/AgCl micromotors ............................................................. 6 1.5 Aim ...................................................................................................................... 9 2. Materials and Methods ......................................................................................... 11 2.1 Microwell fabrication .................................................................................... 11 2.2 Microswimmers fabrication .......................................................................... 12 2.3 Functionalization of particles ........................................................................ 12 2.4.1 Scanning electron microscope ............................................................... 14 2.4.2 UV-vis spectroscopy .............................................................................. 14 2.4.3 Zeta potential ......................................................................................... 14 2.4.4 Optical microscopy ................................................................................ 15 2.5 Motion Experiments ...................................................................................... 15 2.6 Agglutination assay ....................................................................................... 16 2.7 Effect of PBS ................................................................................................. 16 2.7.1 Janus particles ........................................................................................ 16 2.7.2 Agglutination assay ................................................................................ 17 2.7.3 Exclusion of functionalized particles ..................................................... 17 3. Results and Discussion ........................................................................................ 18 3.1 Microwell chip with integrated Janus particles ................................................. 18 3.2 Characterization of particles .............................................................................. 19 3.2.1 UV-vis spectroscopy ................................................................................... 19 3.2.2 Zeta potential .............................................................................................. 21 3.2.3 Agglutination assay in PEG-covered glass slides ....................................... 22 3.3 Motion experiments ........................................................................................... 23 3.3.1 Exclusion time ............................................................................................ 23 3.3.2 On/off light cycles....................................................................................... 26 3.4 Agglutination assay ............................................................................................ 28 3.4.1 Assay performed in wells............................................................................ 28 3.4.2 Assay performed in wells with Janus particles ........................................... 29 3.5 Effect of PBS concentration............................................................................... 30 3.5.1 Janus particles ............................................................................................. 30 3.5.2 Agglutination assay ..................................................................................... 32 3.5.3 Exclusion of functionalized particles .......................................................... 33 4. Conclusions .......................................................................................................... 35 References .................................................................................................................... 37 Declaration of Research Integrity and Good Scientific Practice ................................. 4

Microswimmer-driven agglutination assay

Lab-on-a-chip systems for point-of-care testing demonstrate a promising development towards more accurate diagnostic tests that are of extreme importance for the future global health. This work presents an agglutination assay performed in micrometer sized well using Janus PS/Ag/AgCl micromotors to enhance the interactions between goat anti-human IgM functionalized particles and Human IgM. The fabricated microwell chips are a suitable platform to analyze the interaction between different particles and to perform the agglutination assays. The interaction between active Janus particles and passive and functionalized particles is studied, as well as the influence of ions on the motion of the Janus particles. Agglutination assays are performed with and without the presence of Janus particles, and in different PBS concentrations. Once illuminated with blue light, passive SiO2 particles were effectively excluded from Janus particles, while SiO2 NH2 particles revealed attraction. In contrast, functionalized SiO2 NH2 Ab particles suspended in PBS did not show any interaction. It was found that the optimal working conditions for antibodies and Janus particles differed and, as a result, the Janus particles did not reveal a desirable interaction between the functionalized particles and IgM. Further experiments should be performed to find the proper conditions in which the antibodies and the Janus particles maintain their activities. It is believed that an effective interaction between the functionalized and Janus particles could be achieved by modifying the parameters that affect their interaction such as the zeta potential and the medium in which the assay is being performed. This preliminary work provides the first steps towards the development of a fully integrated lab on a chip system for point of care testing.:Abstract ........................................................................................................................ iii Acknowledgments.......................................................................................................... v Table of Contents .......................................................................................................... vi List of Tables ............................................................................................................. viii List of Figures ............................................................................................................... ix Abbreviations ................................................................................................................. x 1. Introduction ............................................................................................................ 1 1.1 In vitro diagnostic tests ........................................................................................ 1 1.1.1 Point-of-care tests ......................................................................................... 2 1.2 Agglutination assay .............................................................................................. 2 1.3 Lab-on-a-chip ....................................................................................................... 5 1.4 Self-propelled particles ........................................................................................ 6 1.4.1 Light-driven Ag/AgCl micromotors ............................................................. 6 1.5 Aim ...................................................................................................................... 9 2. Materials and Methods ......................................................................................... 11 2.1 Microwell fabrication .................................................................................... 11 2.2 Microswimmers fabrication .......................................................................... 12 2.3 Functionalization of particles ........................................................................ 12 2.4.1 Scanning electron microscope ............................................................... 14 2.4.2 UV-vis spectroscopy .............................................................................. 14 2.4.3 Zeta potential ......................................................................................... 14 2.4.4 Optical microscopy ................................................................................ 15 2.5 Motion Experiments ...................................................................................... 15 2.6 Agglutination assay ....................................................................................... 16 2.7 Effect of PBS ................................................................................................. 16 2.7.1 Janus particles ........................................................................................ 16 2.7.2 Agglutination assay ................................................................................ 17 2.7.3 Exclusion of functionalized particles ..................................................... 17 3. Results and Discussion ........................................................................................ 18 3.1 Microwell chip with integrated Janus particles ................................................. 18 3.2 Characterization of particles .............................................................................. 19 3.2.1 UV-vis spectroscopy ................................................................................... 19 3.2.2 Zeta potential .............................................................................................. 21 3.2.3 Agglutination assay in PEG-covered glass slides ....................................... 22 3.3 Motion experiments ........................................................................................... 23 3.3.1 Exclusion time ............................................................................................ 23 3.3.2 On/off light cycles....................................................................................... 26 3.4 Agglutination assay ............................................................................................ 28 3.4.1 Assay performed in wells............................................................................ 28 3.4.2 Assay performed in wells with Janus particles ........................................... 29 3.5 Effect of PBS concentration............................................................................... 30 3.5.1 Janus particles ............................................................................................. 30 3.5.2 Agglutination assay ..................................................................................... 32 3.5.3 Exclusion of functionalized particles .......................................................... 33 4. Conclusions .......................................................................................................... 35 References .................................................................................................................... 37 Declaration of Research Integrity and Good Scientific Practice ................................. 4

Microswimmer-driven agglutination assay

Lab-on-a-chip systems for point-of-care testing demonstrate a promising development towards more accurate diagnostic tests that are of extreme importance for the future global health. This work presents an agglutination assay performed in micrometer sized well using Janus PS/Ag/AgCl micromotors to enhance the interactions between goat anti-human IgM functionalized particles and Human IgM. The fabricated microwell chips are a suitable platform to analyze the interaction between different particles and to perform the agglutination assays. The interaction between active Janus particles and passive and functionalized particles is studied, as well as the influence of ions on the motion of the Janus particles. Agglutination assays are performed with and without the presence of Janus particles, and in different PBS concentrations. Once illuminated with blue light, passive SiO2 particles were effectively excluded from Janus particles, while SiO2 NH2 particles revealed attraction. In contrast, functionalized SiO2 NH2 Ab particles suspended in PBS did not show any interaction. It was found that the optimal working conditions for antibodies and Janus particles differed and, as a result, the Janus particles did not reveal a desirable interaction between the functionalized particles and IgM. Further experiments should be performed to find the proper conditions in which the antibodies and the Janus particles maintain their activities. It is believed that an effective interaction between the functionalized and Janus particles could be achieved by modifying the parameters that affect their interaction such as the zeta potential and the medium in which the assay is being performed. This preliminary work provides the first steps towards the development of a fully integrated lab on a chip system for point of care testing.:Abstract ........................................................................................................................ iii Acknowledgments.......................................................................................................... v Table of Contents .......................................................................................................... vi List of Tables ............................................................................................................. viii List of Figures ............................................................................................................... ix Abbreviations ................................................................................................................. x 1. Introduction ............................................................................................................ 1 1.1 In vitro diagnostic tests ........................................................................................ 1 1.1.1 Point-of-care tests ......................................................................................... 2 1.2 Agglutination assay .............................................................................................. 2 1.3 Lab-on-a-chip ....................................................................................................... 5 1.4 Self-propelled particles ........................................................................................ 6 1.4.1 Light-driven Ag/AgCl micromotors ............................................................. 6 1.5 Aim ...................................................................................................................... 9 2. Materials and Methods ......................................................................................... 11 2.1 Microwell fabrication .................................................................................... 11 2.2 Microswimmers fabrication .......................................................................... 12 2.3 Functionalization of particles ........................................................................ 12 2.4.1 Scanning electron microscope ............................................................... 14 2.4.2 UV-vis spectroscopy .............................................................................. 14 2.4.3 Zeta potential ......................................................................................... 14 2.4.4 Optical microscopy ................................................................................ 15 2.5 Motion Experiments ...................................................................................... 15 2.6 Agglutination assay ....................................................................................... 16 2.7 Effect of PBS ................................................................................................. 16 2.7.1 Janus particles ........................................................................................ 16 2.7.2 Agglutination assay ................................................................................ 17 2.7.3 Exclusion of functionalized particles ..................................................... 17 3. Results and Discussion ........................................................................................ 18 3.1 Microwell chip with integrated Janus particles ................................................. 18 3.2 Characterization of particles .............................................................................. 19 3.2.1 UV-vis spectroscopy ................................................................................... 19 3.2.2 Zeta potential .............................................................................................. 21 3.2.3 Agglutination assay in PEG-covered glass slides ....................................... 22 3.3 Motion experiments ........................................................................................... 23 3.3.1 Exclusion time ............................................................................................ 23 3.3.2 On/off light cycles....................................................................................... 26 3.4 Agglutination assay ............................................................................................ 28 3.4.1 Assay performed in wells............................................................................ 28 3.4.2 Assay performed in wells with Janus particles ........................................... 29 3.5 Effect of PBS concentration............................................................................... 30 3.5.1 Janus particles ............................................................................................. 30 3.5.2 Agglutination assay ..................................................................................... 32 3.5.3 Exclusion of functionalized particles .......................................................... 33 4. Conclusions .......................................................................................................... 35 References .................................................................................................................... 37 Declaration of Research Integrity and Good Scientific Practice ................................. 4

Data publication: Impedimetric Nanobiosensor for the Detection of SARS-CoV-2 Antigens and Antibodies

This publication includes datasets of electrical impedance spectroscopy measurements of the response of functionalized gold nanowires when interacting with antigens and antibodies related to SARS-CoV-2 in physiological conditions and in human plasma samples