Molecular Recognition Using Nanotube-Adsorbed Polymer Complexes

Molecular recognition is central to the design of therapeutics, chemical catalysis and sensor platforms, with the most common mechanisms involving biological structures such as antibodies¹ and aptamers^2,3.  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.  An alternate approach to constraining a polymer in three-dimensional space involves adsorbing it onto a cylindrical nanotube surface^4-7.  To date, however, the molecular recognition potential of these structured, nanotube-associated complexes has been unexplored.  In this work, we demonstrate three distinct examples in which synthetic polymers enable unique and highly selective molecular recognition once adsorbed onto a single-walled carbon nanotube (SWCNT) surface.  The phenomenon is shown to be generic, with new recognition complexes demonstrated for riboflavin, l-thyroxine, and estradiol, predicted using a 2D thermodynamic model of surface interactions.  The dissociation constants are continuously tunable by perturbing the chemical structure of the heteropolymer. The sensing mechanism is confirmed by simultaneous dual-channel single-molecule imaging of the SWCNT and 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 macrophages. 

References

 

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