Reversible Electrostatic Adsorption of Polyelectrolytes and Bovine Serum Albumin onto Polyzwitterion-Coated Magnetic Multicore Nanoparticles: Implications for Sensing and Drug Delivery

Abstract

We herein present the reversible formation of hybrid nanoparticles featuring a magnetic core and two consecutive polyzwitterion/polyelectrolyte (or protein) layers. Starting from multicore iron oxide nanoparticles, a first coating with zwitterionic poly­(dehydroalanine) is realized, and the resulting PDha@MCNP [PDha = poly­(dehydroalanine) and MCNP = multicore nanoparticle] shows pH-dependent (invertible) surface charge and dispersion stability. In a second step, this can be used as a versatile platform to adsorb either polycations {[poly­(N,N-dimethylamino)­ethyl methacrylate] (PDMAEMA) or poly­(aminomethyl acrylate)}, a polyanion [poly­(styrenesulfonic acid) (PSS)], or a model protein in a quasi layer-by-layer approach. The size, surface charge, and aggregation behavior of the resulting double-layer-coated particles are investigated via dynamic light scattering, transmission electron microscopy, ζ-potential, and turbidity measurements. In contrast to typical layer-by-layer coatings, the use of polyzwitterionic PDha as the first layer allows the pH-dependent release of the second polyelectrolyte shell (PDMAEMA and PSS) upon charge inversion. This turns such reversible multilayer coatings into interesting candidates for applications where controlled swelling or release is in focus and where it is important to control which part of a segmented or nanostructured system responds to changes in the surrounding medium.

Reversible Adsorption of Methylene Blue as Cationic Model Cargo onto Polyzwitterionic Magnetic Nanoparticles

“…Transmission electron microscopy images clearly reveal the appearance of an organic shell around the particles after the coating process (Figure S3, Supporting Information). We have already described the pH‐dependent stability of the PDha shell as well as the pH dependent zeta potential of PDha@MCNP . Briefly, the particles exhibit a zeta potential of +14.9 mV at pH = 2, +13.6 mV at pH = 4, and −22.2 mV at pH = 7.…”

“…Polymeric surfactants are widely used to functionalize the surface of MNP in order to improve dispersion stability and introduce additional functional groups or even targeting moieties . In this context, polyzwitterions as a subclass of polyelectrolytes are of interest as coating materials since they are capable to increase dispersion stability while at the same time reduce unspecific protein adsorption, or exhibit pH‐dependent surface charge . In many application fields, the ability to host small guest molecules is desirable, e.g., in heavy metal removal from aqueous media, drug delivery, or catalysis.…”

“…We recently reported on the successful coating of multicore magnetic iron oxide nanoparticles (MCNP) using polydehydroalanine (PDha), a polyzwitterionic material . Further, it could be demonstrated that the observed charge reversibility of the resulting PDha@MCNP can be exploited for reversible electrostatic adsorption of both polyanions and polycations.…”

Synthesis, Characterization, and Applications of Magnetic Nanoparticles Featuring Polyzwitterionic Coatings

“…The protective groups were cleaved off afterwards to generate a polyzwitterion and the carboxyl groups were used for immobilization at the surface of sub 10 nm MNPs [132] and multicore nanoparticles with 80 nm in diameter. The PDha@MC particles were further used for the adsorption and selective desorption of both polyanions and polycations [171]. Zhu et al used O-carboxymethylchitosan as a naturally occurring polysaccharide and modified the material by functionalization with carboxylic acid groups, followed by immobilization at the surface of MNPs.…”

Double Hydrophilic Poly(ethylene oxide)‐block‐Poly(dehydroalanine) Block Copolymers: Comparison of Two Different Synthetic Routes

“…To date, PDha has been used as a coating material for magnetic nanoparticles, and pH-dependent charge inversion could be used to reversibly adsorb polyelectrolytes, proteins, and dyes onto such hybrid materials. [17][18][19][20][21][22][23] PDha is typically synthesized from poly(tert-butoxycarbonylaminomethylacrylate) (PtBAMA), which is accessed via free or controlled radical polymerization techniques such as atom transfer radical polymerization (ATRP). Hence, block copolymers have also been realized.…”