WEB Effect of PAMAM Dendrimers on Ionic Transport Behaviour of Nanopores in Polymer Membrane
Progressive developments in nanofabrication techniques allow the preparation of synthetic nanopores with various shapes and diameters down to 1 nm for specific application via chemical modification with desired functionalities. The goal, as in living organisms, is to enable sensitive and selective ion transport through the nanopores. The basic principle of a modified nanopore is to detect specific chemical properties from the changes in the electrical signals. Such nanopores could be incorporated in a certain device as electronic components for biomedical or analytical applications. The biological nanopores are only stable in their natural environment, while synthetic nanopores are particularly interesting for many applications due to their significantly greater mechanical and chemical resistance.
In this contribution, we show how the ion transport in polyethylene terephthalate (PET) nanopores is affected by polyamidoamine dendrimers (PAMAM) in dependence of the dendrimer generation. Dendrimers are spherical, highly branched, nanoscale polymeric architectures with a very high density of surface functional groups. Due to their internal cavities capable of encapsulating guest molecules and the effective conjugation of various molecules to the surface functional groups, PAMAM dendrimers are used in many different applications, such as drug delivery, gene therapy, and chemical separations.
Here we demonstrate that modification of PET nanopores with PAMAM dendrimers leads to significant decrease in cationic transport, while an exponential increase in anionic transport depending on dendrimer generation (G0 – G3 is observed. Electrochemical current–voltage measurements are performed on conical single nanopores, while PET membranes containing cylindrical shaped nanopores (10mio pores/cm²) are used for free diffusion experiments. The permeation is analyzed with UV/vis-spectroscopy. An increase in the density of amino groups on the pore surface led to an enhanced anionic transport. Our experiments and theoretical studies showed that this exponential behavior was independent of pore shape and dendrimer generation bigger than G2, but primary related to the average charge density on the pore surface.