Lifetime of biomolecules in polymer-based hybrid nanodevices

Prolonging the lifetime of biomolecules in their functional states is critical for many applications where biomolecules are integrated into synthetic materials or devices. A simplified molecular shuttle system, which consists of fluorescently labelled microtubules propelled by kinesin motor proteins bound to the surface of a flowcell, served here as a model system to probe the lifetime of a hybrid device. In this system, the functional decay can easily be assayed by utilizing optical microscopy to detect motility and disintegration of microtubules. We found that the lifetimes of these hybrid systems were mainly limited by the stability of microtubules (MTs), rather than of kinesin. To determine the biocompatibility of polymers widely used in microfabrication, we assembled flowcells with glass bottom surfaces and covers fabricated from glass, poly(urethane) (PU), poly(methyl-methacrylate) (PMMA), poly (dimethyl siloxane) (PDMS) and ethylene-vinyl alcohol copolymer (EVOH). Without illumination, only PU had a substantial negative impact on MT stability, while PMMA, PDMS and EVOH showed stabilities comparable to glass. Under the influence of light, however, the MTs degraded rapidly in the presence of PDMS or PMMA, even in the presence of oxygen scavengers. A similar effect was observed on glass if oxygen scavengers were not added to the medium. Strong bleaching of the fluorophores was again only found on the polymer substrates and photobleaching coincided with an accelerated depolymerization of the MTs.