Macromolecular Coating Enables Tunable Selectivity in a Porous PDMS Matrix

Abstract

Whether for laboratory use or clinical practice, many fields in Life Sciences require selective filtering. However, most existing filter systems lack the ability to easily tune their filtration behavior. Two key elements for efficient filtering are a high surface-to-volume ratio and the presence of suitable chemical groups which establish selectivity. In this study, an artificial PDMS-based capillary system with highly tunable selectivity properties is presented. The high surface-to-volume ratio of this filter system is generated by first embedding sugar fibers into a synthetic polymer matrix and then dissolving these fibers from the cured polymer. To functionalize this filter, the inner surface of the capillaries is coated with purified or synthetic macromolecules. Depending on the type of macromolecule used for filter functionalization, selective sieving is observed based on steric hindrance, electrostatic binding, electrostatic repulsion, or specific binding interactions. Furthermore, it is demonstrated that enzymes can be immobilized in the capillary system which allows for performing multiple cycles of enzymatic reactions with the same batch of enzymes and without the need to separate the enzymes from their reaction products. In addition to lab-scale filtration and enzyme immobilization applications demonstrated here, the functionalized porous PDMS matrix may also be used to test binding interactions between different molecules.

Repulsive Backbone–Backbone Interactions Modulate Access to Specific and Unspecific Binding Sites on Surface-Bound Mucins

“…We choose two adsorption-based assays to test dextran binding to the different mucin variants, that is, QCM-D measurements (Figure S5) and polydimethylsiloxane (PDMS)-based capillary filter systems (Figure S6). 46 In both cases, the surfaces are functionalized with mucin molecules and, in the second step, the dextrans are selectively depleted from the solution by the surface-bound mucins. Also with those two techniques, we find that the binding of positively charged dextrans to native mucin molecules is very pronounced, whereas the anionic and neutral dextrans are depleted to a much lower extent (Figures S5 and S6).…”

Mucins as multifunctional building blocks of biomaterials

“…Due to the negative charges on mucin glycans, the mucin-functionalized filters bound to positively charged particles while allowing negatively charged particles to flow through. 53 The anti-fouling effect that exists for some mucin coatings, is likely due to the specific chemical nature of the mucins and to the mucins' arrangement at the surface. On hydrophobic surfaces, it is hypothesized that mucins extend their highly glycosylated and highly hydrated domains into the aqueous solvent, while the non-glycosylated protein domains interact with the surface.…”

Agarose‐based hydrogels with tunable, charge‐selective permeability properties

“…8 Of course, for smaller objects, that is, nanoparticles and (macro)molecules, binding interactions are typically more efficient in selectively immobilizing them in biological (or artificial) matrices than trapping them according to size; and indeed, there are first examples where biopolymers have been used to develop artificial, charge-selective sieves that can filter out nanoparticles or molecules. 9,10 There are also synthetic hydrogels with chargeselective permeabilities, and those are usually generated from charged polymers that then bind oppositely charged molecules. For instance, nano-porous hydrogels comprising anionic poly-2-acrylamido-2-methyl-1-propanesulfonic acid can serve as cation-selective filters for the preconcentration of biological samples.…”