Biofunctional Polyelectrolyte Multilayers and Microcapsules: Control of Non-Specific and Bio-Specific Protein Adsorption

Abstract

Layers of the polyelectrolytes poly(allylamine hydrochloride) (PAH, polycationic) and poly(styrene sulfonate) (PSS, polyanionic) are consecutively adsorbed on flat silicon oxide surfaces, forming stable, ultrathin multilayer films. Subsequently, a final monolayer of the polycationic copolymer poly(L‐lysine)‐graft‐poly(ethylene glycol) (PLL‐g‐PEG) is adsorbed onto the PSS‐terminated multilayer in order to impart protein resistance to the surface. The growth of each of the polyelectrolyte layers and the protein resistance of the resulting [PAH/PPS]n(PLL‐g‐PEG) multilayer (n = 1–4) are followed quantitatively ex situ using X‐ray photoelectron spectroscopy and in situ using real‐time optical‐waveguide lightmode spectroscopy. In a second approach, the same type of [PAH/PSS]n(PLL‐g‐PEG) multilayer coatings are successfully formed on the surface of colloidal particles in order to produce surface‐functionalized, hollow microcapsules after dissolution of the core materials (melamine formaldehyde (MF) and poly(lactic acid) (PLA; colloid diameters: 1.2–20 μm). Microelectrophoresis and confocal laser scanning microscopy are used to study multilayer formation on the colloids and protein resistance of the final capsule. The quality of the PLL‐g‐PEG layer on the microcapsules depends on both the type of core material and the dissolution protocols used. The greatest protein resistance is achieved using PLA cores and coating the polyelectrolyte microcapsules with PLL‐g‐PEG after dissolution of the cores. Protein adsorption from full serum on [PAH/PPS]n(PLL‐g‐PEG) multilayers (on both flat substrates and microcapsules) decreases by three orders of magnitude in comparison to the standard [PAH/PPS]n layer. Finally, biofunctional capsules of the type [PAH/PPS]n(PLL‐g‐PEG/PEG‐biotin) (top copolymer layer with a fraction of the PEG chains end‐functionalized with biotin) are produced which allow for specific recognition and immobilization of controlled amounts of streptavidin at the surface of the capsules. Biofunctional multilayer films and capsules are believed to have a potential for future applications as novel platforms for biotechnological applications such as biosensors and carriers for targeted drug delivery.

Simple Coatings to Render Polystyrene Protein Resistant

“…The presence of PLL-g-PEG for the polydopamine assisted graft-PLL-g-PEG sample is confirmed by a further increase in atomic oxygen and nitrogen percentage, which can be attributed to the protein resisting PEG chains, and the PLL-backbone, respectively [17,18,20,52]. The unmodified polystyrene coating showed unexpected oxygen and nitrogen signals, most likely due to contamination of the PS surface before the XPS was acquired (proteins or microbial contamination suspected as the sample was stored in an aqueous environment), or possibly due to oxidation.…”

Phagocytosis of poly(L-lysine)-graft-poly (ethylene glycol) coated microspheres by antigen presenting cells: Impact of grafting ratio and poly (ethylene glycol) chain length on cellular recognition

“…Thus, coating of the particles is expected to yield a -potential close to zero. 46 Experimentally, slightly positive values ͑5±2 mV͒ were obtained for all coated microspheres when measured in solutions of physiological ionic strength. At lower ionic strength ͑10 mM HEPES͒, a statistically significant difference was only observed for PLL͑20͒-͓6.5͔-PEG͑1͒.…”

“…22,[43][44][45] Recent publications report the modification of microparticles with PLLg-PEG and ligand modified PLL-g-PEG polymers that showed excellent protein resistance. 39,46 In addition, it was shown for DC and M⌽ cell cultures that phagocytosis of such particles could be abolished with PLL-g-PEG coatings. 47 However, these studies were performed only with the aforementioned "optimum" architecture, while no evaluation of the influence of polymer structure was reported so far.…”

Electrochemical Biosensors - Sensor Principles and Architectures

“…The capsules usually have a diameter of 1-10 micrometers [235,236]. Optionally, coating of poly(Llysine)-grafted-poly(ethylene glycol) can be applied to make them protein resistant [237].…”