Temperature-Swing Adsorption of Proteins in Water Using Cationic Copolymer-Grafted Silica Particles

Abstract

We have prepared silica particles grafted with poly(N-isopropylacrylamide) (PNIPA) copolymers as adsorbent for the temperature-swing adsorption of bovine serum albumin (BSA) in water, where vinylbenzyl trimethylammonium chloride (VBTA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), or N,N-dimethylacrylamide (DMAA) was employed as a comonomer. The surface potentials of PNIPA-grafted and P(NIPA-co-DMAA)-grafted silica particles in water at 298 and 313 K were negative, while those of P(NIPA-co-VBTA)-grafted silica particle were positive, because VBTA is a quaternary ammonium salt and positively charged in aqueous solutions. As for the P(NIPA-co-DMAEMA)-grafted silica particle, the surface potential changed from positive to near zero with increasing temperature from 298 K to 313 K. This may be because the coil-to-globule transition of grafted copolymers leads to the dehydration and deprotonation of DMAEMA group, which is a tertiary amine and can be positively charged only in the aqueous phase. Although PNIPA-grafted and P(NIPA-co-DMAA)-grafted silica particles failed to adsorb BSA, P(NIPAco-VBTA)-grafted and P(NIPA-co-DMAEMA)-grafted silica particles adsorbed BSA, indicating that BSA is adsorbed by the electrostatic attraction between the negatively charged BSA and the positively charged copolymers on the silica surface. Moreover, P(NIPA-co-VBTA)-grafted and P(NIPA-co-DMAEMA)-grafted silica particles repeatedly adsorbed BSA at 298 K and desorbed some of the preadsorbed BSA at 313 K via the temperature-swing operation. This BSA desorption may result from the decrease in the number of the positively charged groups accessible to BSA due to the coil-to-globule transition of the grafted copolymers with increasing temperature.

Dual-Stimuli-Sensitive Microgels as a Tool for Stimulated Spongelike Adsorption of Biomaterials for Biosensor Applications

“…Despite the numerous published data on the interaction of proteins and enzymes with dispersed and adsorbed microgels − and on biosensors prepared with microgels, ,− there were to the best of our knowledge no any data on such stimulated adsorption of microgels onto hydrophobic interfaces published so far. This would be highly required for modification of initially hydrophobic substrates, particularly, for graphite-based substrates/nanomaterials that are now in the forefront of scientific interest.…”

Engineering Systems with Spatially Separated Enzymes via Dual-Stimuli-Sensitive Properties of Microgels

“…The applications of stimuli-sensitive systems loaded with guest molecules include drug delivery systems, − cell culture, cell harvesting, functional biomaterials, biosensors, , etc. Published data can be found on the interaction of proteins and enzymes with dispersed and adsorbed microgels. ,,− Thermally regulated loading of nanogels with small molecules like doxorubicin, polypeptide insulin, or “breathing in” loading of siRNA via imbibing by freeze-dried PNIPAM nanogels was described. Reversible alteration of specific enzymatic activity with temperature has also been demonstrated for thermosensitive gels/microgels comprising immobilized enzymes. − Most of the data described the interaction of (micro)­gels with guest (bio)­molecules of only one type.…”

Fabrication of non-close-packed colloidal monolayers by convective self-assembly using cationic polyelectrolyte-grafted silica particles

“…In the present study, we have prepared cationic polyelectrolyte-grafted silica particles and then applied their water suspensions to the CSA processes to obtain the colloidal layers. As a grafted polyelectrolyte, poly((3-acrylamidopropyl)trimethylammonium chloride) (PAPTAC) and poly(vinylbenzyl trimethylammonium chloride) (PVBTA) have been employed, because we had succeeded in preparing the polymer-grafted silica particles using these cationic monomers in our previous study [30]. Due to the polyelectrolyte brush on the silica particle surface, it can be expected that both the steric and the electrostatic repulsions act between the particles in water.…”