Biomolecular Interaction Analysis of Gestrinone-anti-Gestrinone Using Arrays of High Aspect Ratio SU-8 Nanopillars

Engineering vertically interrogated interferometric sensors for optical label-free biosensing

In this work, we review the technology of vertically interrogated optical biosensors from the point of view of engineering. Vertical sensors present several advantages in the fabrication processes and in the light coupling systems, compared with other interferometric sensors. Four different interrelated aspects of the design are identified and described: sensing cell design, optical techniques used in the interrogation, fabrication processes, fluidics, and biofunctionalization of the sensing surface. The designer of a vertical sensor should decide carefully which solution to adopt on each aspect prior to finally integrating all the components in a single platform. Complexity, cost, and reliability of this platform will be determined by the decisions taken on each of the design process. We focus on the research and experience acquired by our group during last years in the field of optical biosensors.

Tunable high aspect ratio polymer nanostructures for cell interfaces

Nanoscale topographies and chemical patterns can be used as synthetic cell interfaces with a range of applications including the study and control of cellular processes. Herein, we describe the fabrication of high aspect ratio nanostructures using electron beam lithography in the epoxy-based polymer SU-8. We show how nanostructure geometry, position and fluorescence properties can be tuned, allowing flexible device design. Further, thiol-epoxide reactions were developed to give effective and specific modification of SU-8 surface chemistry. SU-8 nanostructures were made directly on glass cover slips, enabling the use of high resolution optical techniques such as live-cell confocal, total internal reflection and 3D structured illumination microscopy to investigate cell interactions with the nanostructures. Details of cell adherence and spreading, plasma membrane conformation and actin organization in response to high aspect ratio nanopillars and nanolines were investigated. The versatile structural and chemical properties combined with the high resolution cell imaging capabilities of this system are an important step towards the better understanding and control of cell interactions with nanomaterials.

Local pH-responsive diazoketo-functionalized photoresist for multicomponent protein patterning

Selective surface immobilization of multiple biomolecule components, under mild conditions where they do not denature, is attractive for applications in biosensors and biotechnology. Here, we report on a biocompatible and pH-responsive photoresist containing diazoketo-functionalized methacrylate, methacrylic acid, and poly(ethylene glycol) methacrylate monomers, where the photolithographic process may be carried out in a local pH range to minimize biomolecular denaturation. The polymer is insoluble or sparsely soluble in pH 6.4 or more acidic solution or deionized water, but soluble in a basic solution, pH 7.9 or more. After UV exposure, however, carboxylic acid groups are generated by Wolff rearrangement and photodissociation of the diazoketo groups in the polymer chain, leading to dissolution of UV-exposed polymer at pH 6.4. Using the property of the pH-solubility switching, we demonstrate dual streptavidin patterning using only biological buffers, pH 6.4 and 7.9 solutions, and double exposure patterning to confirm the sustainability of the diazoketo groups in unexposed regions despite carrying out several wet processes.