A versatile evaporation-assisted methodology based on the coffee-drop effect is described to deposit nanoparticles on surfaces, obtaining for the first time patterned gradients of protein nanoparticles (pNPs) by using a simple custom-made device.
Cells accommodate to their external environment and therefore to various stimuli such as ramps of soluble biomolecules and gradients of topography or stiffness by moving to their preferred conditions. Reproducing these gradients in vitro is one of the most popular and effective approaches to study cell motility. There is no straightforward technique that allows obtaining surface-bound protein particle gradients from their colloidal suspensions. One way to tackle this shortcoming is the emerging field of evaporation-assisted deposition methods, based on the widely known “coffee-drop effect”.
Protein Nanoparticles (pNPs) are nontoxic and mechanically stable particles with sizes ranging from ca. 50 to 500−600 nm. They have functional amyloid structure and are under exploration as drug delivery systems and as biochemical and topographical modifiers of surfaces at nanoscales and microscales for cell-guiding studies. We have previously used these materials for surface decoration with geometrical patterns at constant pNP concentrations for cell guidance. [1−4] Nevertheless, to the best of our knowledge, they have not been used to produce surface-bound gradients of pNPs.
In this work, a versatile evaporation-assisted methodology based on the coffee-drop effect is described to deposit nanoparticles on surfaces, obtaining for the first time patterned gradients of protein nanoparticles (pNPs) by using a simple custom-made device. In this way, fully controllable patterns with specific periodicities consisting of stripes with different widths and distinct nanoparticle concentration as well as gradients can be produced over large areas (∼10 cm2) in a fast (up to 10 mm2 /min), reproducible, and cost-effective manner using an operational protocol optimized by an evolutionary algorithm. This method can be readily applied to a flat surface, that is, it does not require masks, stamps, replicas, surface functionalizations, or any other type of labelling. The developed method opens the possibility to decorate surfaces “a-la-carte” with pNPs enabling different categories of high-throughput studies on cell motility.
Witold I. Tatkiewicz,1,2 Joaquin Seras-Franzoso,2,3 Elena Garcia-Fruitós, 2,3 Esther Vazquez, 2,3 Adriana R. Kyvik,1,2 Judith Guasch,1,2,4 Antonio Villaverde,2,3 Jaaume Veciana,1,2 Imma Ratera1,2,4
1Institut de Ciència de Materials de Barcelona (CSIC), Spain
2Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Spain
3Institut de Biotecnologia i de Biomedicina (IBB) and Departament de Genètica i de Microbiologia, UAB, Spain
4Dynamic Biomaterials for Cancer Immunotherapy, Max Planck Partner Group, ICMAB-CSIC, Spain
Surface-Bound Gradient Deposition of Protein Nanoparticles for Cell Motility Studies
ACS Applied Materials & Interfaces 10, 25779−25786 (2018)
Top. Left: Schematic view of the custom-made device designed for evaporation-assisted pattern deposition of pNPs. Right: Substrate functionalized with pNP of the Green Fluorescent Protein (GFP) at different concentrations and gradients used for high-throughput cell motility studies.
Bottom. Scheme of an operational protocol consisting of three consecutive steps (i = 1, 2, 3) with deposition input parameters (Vi) and output characteristics (CDi, Ii, or Hi), presented on separate plots, resulting in the deposition of three stripes.
 Seras-Franzoso, J.; et. al. Integrating Mechanical and Biological Control of Cell Proliferation through Bioinspired Multieffector Materials. Nanomedicine 2015, 10, 873−891.
 Tatkiewicz, W. I.; et. al. Two-Dimensional Microscale Engineering of Protein- Based Nanoparticles for Cell Guidance. ACS Nano 2013, 7, 4774− 4784.
 O. Cano-Garrido, et al. Functional protein-based nanomaterial produced in microorganisms recognized as safe: A new platform for biotechnology, Acta Biomaterialia 2016, 43, 230–239
 O. Cano-Garrido, et. al. Supramolecular organization of protein-releasing functional amyloids solved in bacterial inclusion bodies, Acta Biomaterialia, 2013, 9, 6134–6142