Regulating the Translocation of DNA through Poly(N-isopropylacrylamide)-Decorated Switchable Nanopores by Cononsolvency Effect

Abstract

Stimulus response of polymer-decorated nanopores/nanochannels is a fascinating topic both in polymer science and modern nanotechnology; however, it is still challenging for standard analytical methods to characterize these switchable nanopores/nanochannels. In this study, based on the physics of polymer translocation we developed an analytic method and thus for the first time were able to quantitatively measure the effective thickness of the polymer layer around the rim of nanopores. As an application example of this method, we studied the translocation dynamics of fluorescence DNA through poly(N-isopropylacrylamide) decorated switchable nanopores in aqueous environments. By adding small amounts of ethanol to the aqueous buffer solution a switch-like response of the DNA-translocation can be observed. It is also observed that a pronounced switching effect can be only realized in a window of moderate grafting densities of poly(N-isopropylacrylamide) layer. These are attributed to the cononsolvency effect which causes a collapse of the polymer layer and thus a transition between "closed" and "open" states of the nanopores for DNA translocation. Our study clearly transpired that cononsolvency effect of polymers can be used as a novel trigger to change the size of nanopores, in analogy to the opening and closure of the gates of cell-membrane channels. We envisage that our study will spawn further developments for the design of switchable nano-gates and nanopores.

Membranotronics: Bioinspired Nonlinear Ion Transport with Negative Differential Resistance Based on Elastomeric Membrane System

“…Previous studies have used similar concepts to control the translocation of DNA through PNIPAM‐decorated nanopores. [ 65 ]…”

A nanofluidic system based on cylindrical polymer brushes: how to control the size of nanodroplets

“…Experimentally, brush-decorated nanopores can be prepared and have been shown to regulate the translocation of fluorescent DNA 43 . We shall make a rather rough comparison of parameters used in these experiments with the simulations shown here using a coarse-grained model: In the experiment, the channel radius was R = 25 nm, its length L ∼ 6 μm and the pressure difference Δ P ∼ 150 mbar = 1.5 × 10 4 N m −2 = 1.5 × 10 −2 pN nm −2 between both sides of the channel.…”

Cononsolvency of thermoresponsive polymers: where we are now and where we are going

“…161 While for thin films or polymer brushes grafted from planar surfaces, the swelling behavior can be derived from spectral reflectance, ellipsometry and AFM measurements, the characterization of polymer-decorated nanopores is more complicated. Very recently, Yong et al 10 presented a novel method the quantitatively evaluate the swelling state using the translocation of polymer in dilute solutions.…”

“…1. The cononsolvency effect has been employed in a wide range of applications such as sensing for detecting volatile organic compounds 6 or enantiomeric excess, 7 catalysis, 8 hydrogel actuators, 9 regulation of transport through nanopores, 10 separation processes based on selective precipitation, 11,12 and the formation of self-assembled nanostructures. 13 Additionally, the cononsolvency effect of thermoresponsive polymer brushes has been utilized for the transportation of nanoparticles, 14 and the development of surfaces with tunable friction.…”

“…Besides linear chains of homopolymers, more complex systems have been investigated regarding their cononsolvency behavior such as cross-linked gels, 29,55,114,[141][142][143][144][145][146] block copolymer systems, 13,57,58,[147][148][149] thin films, 59,150 and grafted polymer brushes. 10,14,15,17,73,151,152 Microgels are macromolecular networks swollen by the solvent they are dissolved in. The size of the microgels networks is in the range of several micrometers down to nanometers (then sometimes called ''nanogels'').…”