Control of molecular translocation through nanoscale apertures is of great interest for DNA sequencing, biomolecular filters, and new platforms for single molecule analysis. However, methods for controlling the permeability of nanopores are very limited. Here, we show how nanopores functionalized with poly(ethylene glycol) brushes, which fully prevent protein translocation, can be reversibly gated to an “open” state by binding of single IgG antibodies that disrupt the macromolecular barrier. On the basis of surface plasmon resonance data we propose a two-state model describing the antibody–polymer interaction kinetics. Reversibly (weakly) bound antibodies decrease the protein exclusion height while irreversibly (strongly) bound antibodies do not. Our results are further supported by fluorescence readout from pore arrays and high-speed atomic force microscopy on single pores. This type of dynamic barrier control on the nanoscale provides new possibilities for biomolecular separation and analysis.

Molecularly imprinted polymers (MIPs) are artificial receptors which can be tailored to bind target molecules specifically. A new method, using photoinitiated atom-transfer radical polymerization (ATRP) for their synthesis as monoliths, thin films and nanoparticles is described. The synthesis takes place at room temperature and is compatible with acidic monomers, two major limitations for the use of ATRP with MIPs. The method has been validated with MIPs specific for the drugs testosterone and S-propranolol. This study considerably widens the range of functional monomers and thus molecular templates which can be used when MIPs are synthesized by ATRP, as well as the range of physical forms of these antibody mimics, in particular films and lithographic patterns, and their post-functionalization from living chain-ends.

A new and generic method for protein capture-release by polyelectrolyte brushes and pH control.

Molecularly imprinted polymers (MIPs) are artificial receptors which can be tailored to bind target molecules specifically. A new method, using photoinitiated atom-transfer radical polymerization (ATRP) for their synthesis as monoliths, thin films and nanoparticles is described. The synthesis takes place at room temperature and is compatible with acidic monomers, two major limitations for the use of ATRP with MIPs. The method has been validated with MIPs specific for the drugs testosterone and S-propranolol. This study considerably widens the range of functional monomers and thus molecular templates which can be used when MIPs are synthesized by ATRP, as well as the range of physical forms of these antibody mimics, in particular films and lithographic patterns, and their post-functionalization from living chainends.

The possibility to detect and analyze single or few biological molecules has proven very important for understanding their function and interaction mechanisms. Ideally, the molecules should be confined to a nanoscale volume so that the observation time can be extended. However, it has proven difficult to develop reliable, non-invasive trapping techniques for biomolecules under physiological conditions. Here we present a new concept for long-term and tether-free trapping of proteins without exposing them to any field gradient forces. We show that a responsive polymer brush can make solid state nanopores switch between a fully open and a fully closed state with respect to proteins, while always allowing the passage of solvent, ions and small molecules (up to ~1 kg/mol). This makes it possible to trap a very high number of proteins (500-1000) inside nanoscale chambers with a volume as small as one attoliter, reaching concentrations up to 60 g/L, which is orders of magnitude higher than for existing container-based technologies. Additionally, our method is fully compatible with parallelization by imaging arrays of nanochambers. As an application example, we show that enzymatic cascade reactions can be performed with multiple native enzymes under full nanoscale confinement and steady supply of reactants. This platform will greatly extend the possibilities of single/few molecule analysis by optical methods, and should be particularly useful for studying protein-protein interactions, such as the dynamics of oligomerization.