Controlled Surface Silanization for Actin-Myosin Based Nanodevices and Biocompatibility of New Polymer Resists

Abstract

Molecular motor-based nanodevices require organized cytoskeletal filament guiding along motility-promoting tracks, confined by motility-inhibiting walls. One way to enhance motility quality on the tracks, particularly in terms of filament velocity but also the fraction of motile filaments, is to optimize the surface hydrophobicity. We have investigated the potential to achieve this for the actin-myosin II motor system on trimethylchlorosilane (TMCS)-derivatized SiO surfaces to be used as channel floors in nanodevices. We have also investigated the ability to supress motility on two new polymer resists, TU7 (for nanoimprint lithography) and CSAR 62 (for electron beam and deep UV lithography), to be used as channel walls. We developed a chemical-vapor deposition tool for silanizing SiO surfaces in a controlled environment to achieve different surface hydrophobicities (measured by water contact angle). In contrast to previous work, we were able to fabricate a wide range of contact angles by varying the silanization time and chamber pressure using only one type of silane. This resulted in a significant improvement of the silanization procedure, producing a predictable contact angle on the surface and thereby predictable quality of the heavy meromyosin (HMM)-driven actin motility with regard to velocity. We observed a high degree of correlation between the filament sliding velocity and contact angle in the range 10-86°, expanding the previously studied range. We found that the sliding velocity on TU7 surfaces was superior to that on CSAR 62 surfaces despite similar contact angles. In addition, we were able to suppress the motility on both TU7 and CSAR 62 by plasma oxygen treatment before silanization. These results are discussed in relation to previously proposed surface adsorption mechanisms of HMM and their relationship to the water contact angle. Additionally, the results are considered for the development of actin-myosin based nanodevices with superior performance with respect to actin-myosin functionality.

Comparative analysis of widely used methods to remove nonfunctional myosin heads for the in vitro motility assay

“…Instead we attribute the velocity reduction to braking interactions between the C-terminal tail region and actin. This idea is consistent with a reduction in actin sliding velocity on surfaces of reduced contact angle (Albet-Torres et al 2007 ; Persson et al 2010 ; Månsson 2012 ; Lindberg et al 2018 ) where the effect has been attributed to an increased fraction of HMM molecules with the tail regions extending away from the surface towards the actin filaments. The effect may also be related to the finding (Guo and Guilford 2004 ) that the presence of the coiled-coil light meromyosin fragment of myosin in an in vitro motility assay reduces sliding velocity.…”

“…We and others (Albet-Torres et al 2007 ; Nicolau et al 2007 ; Lindberg et al 2018 ) have previously found that varied surface hydrophobicities, reflected in varied surface contact angle in the range 0–85°, alter the actin sliding velocity, in a graded fashion, from zero at the lowest contact angles to a maximum at contact angles > 70° (as on the TMCS derivatized surfaces used here). This effect has been attributed to gradual variation in the distribution between different surface adsorption configurations of HMM with varying contact angle (Albet-Torres et al 2007 ; Persson et al 2010 ; Månsson 2012 ; van Zalinge et al 2012 ; Lindberg et al 2018 ). It therefore seems likely that small differences in the HMM conformation e.g.…”

“…We consider our results in relation to a model based on experimental data for HMM adsorption with close to saturating HMM densities on TMCS derivatized surfaces (Sundberg et al 2006 ; Albet-Torres et al 2007 ; Månsson et al 2008 ; Persson et al 2010 ; Månsson 2012 ; Lindberg et al 2018 ). According to this model, HMM at high solution concentration (> 100 µg/ml) adsorbs to the surface either via the actin-binding region or the C-terminal chymotrypsin cleavage site of S2 (Fig.…”

“…Green circles indicate most likely sites for adsorption to a TMCS surface. The experimental and theoretical basis for the model with high probability of adsorption via the C-terminal tail (chymotrypsin cleavage site; large circle) and lower probability via the actin-binding region (small circle) is given in detail previously (Albet-Torres et al 2007 ; Månsson et al 2008 ; Persson et al 2010 ; Månsson 2012 ; Lindberg et al 2018 ). Question marks indicate the possibility of further interaction sites between surfaces and HMM.…”

Positional Isomers of a Non-Nucleoside Substrate Differentially Affect Myosin Function

“…Thus, gaining control over molecular motors represents a promising area for novel therapeutic approaches to treat many prevalent conditions. Gaining control over molecular motors is also a focus of nanotechnology efforts that aim to build synthetic controllable molecular motor-based nanomachines (9)(10)(11)(12)(13). Indeed, biological motors have even been used, in this context, to perform parallel computing tasks (14), where precise control over the motors is critical to proper function of the nanodevice.…”