Biomimetic glass nanopores employing aptamer gates responsive to a small molecule

Abstract

We report the preparation of 20 and 65 nm radii glass nanopores whose surface is modified with DNA aptamers controlling the molecular transport through the nanopores in response to small molecule binding.Single synthetic nanopores are of interest as potential mimics of biological pores such as gated ion channels. Controlled transport through these synthetic pores can be achieved by integrating polymers responsive to chemical or physical stimuli. 1 Stimuli reported to date include pH, 2 ionic strength, temperature, 3 UV light as well as recognition of an ion, 4 a small molecule 5 or a protein. 6 The responsive components in the system can exhibit a single or a combination of several responses to the environmental conditions, such as changes in charge and conformation of surface-bound macromolecules. Here we significantly broaden the range of molecular effectors that can be employed to control the gating of such channels via the use of aptamers, DNA or RNA molecules selected for their ability to bind to, and fold in response to, specific aqueous targets, as the gating macromolecule. 7 As the substrate onto which our gating aptamers have been grafted we have employed a single glass nanopore electrode (Fig. 1, see ESI † for preparation details). 8 It consists of a platinum microdisk electrode embedded at the bottom of a conical nanopore made in glass, with the circular orifice of the pore having dimensions in the range 5 to 100 nm. Redoxactive molecules diffuse and migrate through the orifice connecting the bulk solution and nanopore interior. The deep cone shape of the nanopore results in an important transport characteristic: the steady-state flux of molecules into the pore is limited by the resistive restriction at the pore orifice and is independent of other geometrical parameters of the pore. Earlier, we have reported that surface modification of the glass nanopore electrodes with spiropyran moieties leads to the photochemical control of molecular transport through the pore orifice. 9 Specifically, we were able to electrostatically control the diffusion of a positively charged species by UV light-induced conversion of the neutral surface-bound spiropyran to its protonated merocyanine form, and restore the transport through the pore † Electronic supplementary information (ESI) orifice by irradiation of the electrode with visible light to reverse the spiropyran transformation. The present work introduces our proof-of-principle experiments where biomimetic glass nanopores are prepared with transport properties responsive to small molecules as a result of introducing aptamers as the sterically gating macromolecules.Critical to our investigation, aptamers can be engineered to undergo a large-scale conformational response to specific small molecules. 7a,b,10 For example, the aptamer A1 (Table 1) employed in the present work and based on a 32-base sequence reported by Stajonovic et al., binds and folds in response to cocaine. 10 Specifically, the aptamer remains partially unfolded in the absence of a targ...

Nanoporous silica colloidal films with molecular transport gated by aptamers responsive to small molecules

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Aptamer‐Based Switchable Nanovalves for Stimuli‐Responsive Drug Delivery

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Sampling a Biomarker of the Human Immunodeficiency Virus across a Synthetic Nanopore

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