www.advmatinterfaces.de FULL PAPER 1800621 (1 of 8) © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Cell Alignment on Graphene–Amyloid Composites Subhadeep Das, Mukesh K. Kumawat, Srivastav Ranganathan, Rakesh Kumar, Jozef Adamcik, Pradeep Kadu, Ranjith Padinhateeri, Rohit Srivastava, Raffaele Mezzenga, and Samir K. Maji* DOI: 10.1002/admi.201800621 and biosensors. [4a,5] Amyloids are another class of nanomaterial formed by highly ordered self-assembled protein/peptide. [6] The amyloid nanofibril structure is highly stable against various harsh physical and chemical conditions due to its unique cross-β-rich packing. Although implicated in various diseases, recent research dem- onstrates that not all amyloids are toxic entities. [7] Recently, we and other groups have shown that amyloids are excel- lent cell adhesive materials and they can mimic the nanotopography of natural extracellular matrices. [8] Further, amyloid- based matrices can be used for stem cell differentiation, which finds applications in tissue engineering. [9] The unique material properties of the amyloid fibrils provide a distinctive platform for the development of excellent nanocom- posites with other materials including carbon-based materials for various applications. [4d,10] From a materials science per- spective, the hybridization of the amyloids and graphene can generate novel materials with unique properties combining the excellent properties of the two pristine compounds. For example, graphene and β-lactoglobulin amyloid fibrils have been used as biodegradable nanocomposites in enzyme bio- sensing applications [4d] and additionally exhibit humidity- dependent shape memory features. It has also been reported that amyloid fibrils display unique symmetrical self-assembly upon interacting with graphene surface. [11] In this study, relying on the established interaction capacity of graphene and amyloids, we have developed a unique graphene– amyloid composite, based on a designed amyloidogenic pep- tide, which is previously known to form nontoxic amyloids. [9b] This graphene–amyloid composite generates ordered micro- structures of troughs and crests of regular periodicity upon drying for developing a film. Interestingly, when we cultured neuroblastoma cells SH-SY5Y on this film substrate, the cells were aligned and ordered, demonstrating a perfect templating effect of this film (Scheme 1). 2. Results and Discussions The graphene–amyloid composite (p1-rGO) is prepared by mixing the graphene oxide (GO) suspension in water with pep- tide p1 (Fmoc-VIA) suspension in 20 × 10 -3 M phosphate buffer, pH 7.4. The mixture was subsequently heated in presence of hydrazine hydrate for reduction, which yielded reduced Graphene-based hybrid nanomaterials have been shown to have great potential in various biotechnology applications including enzyme sensing and bone tissue engineering. Harnessing the unique properties of graphene and material strength of amyloids, a graphene–amyloid composite film is developed that can self-organize into periodic troughs and crests without the need of lithographic techniques or etching. The topographies generated by the film provide powerful modulators of contact and guidance to neural pre- cursor cells, enabling efficient cellular polarization and differentiation. Using molecular dynamic simulations and high-resolution atomic force microscopy, the amyloidogenicity and handedness of matured amyloid nanofibrils to the micropatterns generated on the dried film are also correlated. These insights provide principles for peptide designing for generation of micropatterned, cell adhesive conductive substrates for optimal cell alignment and differentiation. Dr. S. Das IITB-Monash Research Academy Indian Institute of Technology Bombay Mumbai, Maharashtra 400076, India Dr. S. Das, M. K. Kumawat, Dr. S. Ranganathan, R. Kumar, P. Kadu, Prof. R. Padinhateeri, Prof. R. Srivastava, Prof. S. K. Maji Department of Biosciences and Bioengineering Indian Institute of Technology Bombay Mumbai, Maharashtra 400076, India E-mail: samirmaji@iitb.ac.in Dr. J. Adamcik, Prof. R. Mezzenga ETH Zurich Department of Health Sciences & Technology Schmelzbergstrasse 9, LFO, E23, 8092 Zürich, Switzerland The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admi.201800621. Amyloid-Graphene Nanocomposites 1. Introduction Designing biomimetic composites based on graphene and various biopolymers such as protein [1] and DNA [2] shows promising applications in nanotechnology and biotechnology. Especially, inspired by nature, it has been demonstrated that a suitable combination of hard materials such as graphene and relatively soft self-assembled materials such as collagen and silk, can lead to biocomposite materials with superior quality and desired functionalities. [3] Graphene has extraordinary electronic, mechanical, and surface properties, which are har- nessed in diverse applications from biomedical engineering to optoelectronics. [4] Different groups have earlier demonstrated the application of graphene in drug delivery, cell detection, Adv. Mater. Interfaces 2018, 1800621