Molecular Recognition Using Nanotube-Adsorbed Polymer Interfaces

Molecular recognition is central to the design of therapeutics, chemical catalysis and sensor platforms, with the most common mechanisms involving biological structures such as antibodies and aptamers.  The key to this molecular recognition is a folded and constrained heteropolymer pinned, via intra-molecular forces, into a unique three-dimensional orientation that creates a binding pocket or interface to recognize a specific molecule.  In this work, we focus on the recognition of small molecules using nanotube-adsorbed polymer interface. Once a heteropolymer is adsorbed onto a cylindrical nanotube surface, intra-molecular forces of the functional groups of the polymer constrain the distance and orientation of the adsorption sites of the polymer on the nanotube, creating two-dimensional recognition sites on the SWCNT for molecules of interest. The molecular recognition potential of these structured, nanotube-assisted complexes has been unexplored.  In this work, we demonstrate three distinct examples, in which synthetic polymers can present unique and highly selective molecular recognition sites on the SWCNT surface.  The phenomenon is shown to be generic, with new recognition complexes demonstrated for riboflavin, l-thyroxine, and estradiol.  The dissociation constants are continuously tunable by perturbing the chemical structure of the heteropolymer.  The complexes can be used as new types of sensors based on modulation of SWCNT photoemission, as demonstrated using a complex for real time spatio-temporal detection of riboflavin in murine.