Controlling Interfacial Adhesion of Self-Assembled Polypeptide Fibrils for Novel Nanoelectromechanical System (NEMS) Applications

Narender Rana,Alain E Kaloyeros,Christopher Kossow,Eric T Eisenbraun,Robert E Geer

doi:10.3390/mi2010001

Narender Rana, Alain E Kaloyeros + Show 3 more

Open Access

https://doi.org/10.3390/mi2010001

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Abstract

The relative adhesion of two genetically engineered polypeptides termed as H6-(YEHK)x21-H6 and C6-(YEHK)X21-H6 has been investigated following growth and self-assembly on highly oriented pyrolytic graphite (HOPG), SiO2, Ni, and Au substrates to study covalent surface attachment via histidine (H) and cysteine (C) groups incorporated in the polypeptides. Both polypeptides formed predominantly bilayer fibrils upon deposition, in agreement with previous studies. The relative adhesion of polypeptide fibrils to the substrate, as well as intra-fibril cohesion, was examined via a forced-scanning method employing contact mode atomic force microscopy (AFM). H6-(YEHK)x21-H6 polypeptide fibrils were observed to detach from Ni, Au, SiO2, and HOPG substrates at normal tip forces of 106 ± 10 nN, 21 ± 3 nN, 22 ± 3 nN, and 3 ± 1 nN, respectively. C6-(YEHK)x21-H6 polypeptide fibrils were seen to detach from Au substrates at a normal spring force of 90 ± 10 nN. It is concluded that the H6-(YEHK)x21-H6 and C6-(YEHK)x21-H6 polypeptide fibrils are covalently attached to, respectively, Ni and Au substrates, which has important implications for the use of these materials for NEMS fabrication. The structural stability of deposited polypeptide fibrils was also evaluated by using normal tip forces less than those required for fibril detachment. H6-(YEHK)x21-H6 polypeptide fibrils on Ni substrates were the most structurally stable compared to C6-(YEHK)x21-H6 polypeptide fibrils on Au substrates. Controlled delayering of bilayer fibrils was also detected for sub-detachment normal forces.

Highlights

Biologically-inspired materials offer great potential for use in a range of nano-electromechanical systems (NEMS), including invasive biodevices such as biosensors and nano-syringes, as well as for structural applications that take advantage of the unique mechanical and electrical properties of such materials
Due to tip contact and convolution effects, the lateral dimensions measured via contact-mode atomic force microscopy (AFM)—as applied for adhesion measurements—are generally larger than their AFM tapping mode counterparts
H6-(YEHK)x21-H6 bilayer fibrils on a highly oriented pyrolytic graphite (HOPG) substrate (2 μm × 2 μm scan size) acquired using a cantilever with a spring constant of 0.08 N/m

Summary

Introduction

Biologically-inspired materials offer great potential for use in a range of nano-electromechanical systems (NEMS), including invasive biodevices such as biosensors and nano-syringes, as well as for structural applications that take advantage of the unique mechanical and electrical properties of such materials. These materials can be fabricated inexpensively in large quantities using well-controlled genetic engineering techniques, allowing atomic scale control over the size and form factor of the structure [1,2]. These polypeptides have the propensity to form linear and predominantly bilayer fibrils [5], with the resulting nanostructures being able to potentially serve as mechanical supports, nanoprobes, nanowires, and/or templates for nanowires [6,7]

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