Oligolayer-Coated Nanoparticles: Impact of Surface Topography at the Nanobio Interface

Abstract

Layer-by-layer coating of nanoparticles with a layer number in the single-digit range has gained increasing attention in the field of nanomedicinal research. However, the impact of using various polyelectrolytes on oligolayer formation and, more importantly, their influence on the interaction with the biological system has not often been considered in the past. Hence, we investigated the polyelectrolyte deposition profiles and resulting surface topographies of up to three polyelectrolyte layers on a flat gold sensor surface using three different polycations, namely, poly(ethylene imine) (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallylammonium chloride) (PD), each in combination with poly(styrenesulfonate) (PSS). Surface plasmon resonance spectroscopy and atomic force microscopy revealed that the PEI/PSS pair in particular showed a so-called overshoot phenomenon, which is associated with partial polyelectrolyte desorption from the surface. This is also reflected by a significant increase in the surface roughness. Then, after having transferred the oligolayer assembly onto nanoparticles of ∼32 nm, we realized that quite similar surface topographies must have emerged on a curved gold surface. A major finding was that the extent of surface roughness contributes significantly to the fashion by which the oligolayer-coated nanoparticles interact with serum proteins and associate with cells. For example, for the PEI/PSS system, both the surface roughness and protein adsorption increased by a factor of ∼12 from the second to third coating layer and, at the same time, the cell association massively decreased to only one-third. Our study shows that surface roughness, along with other particle properties such as size, shape, zeta potential, and hydrophobicity, is another decisive factor for nanoparticles in a biological context, which has indeed been discussed previously but has not to date been investigated for oligolayers.

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“…Intensive property‐ and structural‐analysis for samples at the nanoscale in the fields of medicine, chemistry, and biology created the need of high resolution research tools for conductive and nonconductive, hard, and soft (organic) materials (Hahnel et al, ; Ionescu et al, ; Kodera, Yamamoto, Ishikawa, & Ando, ; Wurster et al, ). Modifications of core shell nanoparticles to create patterned hydrophilic or hydrophobic shells, need characterization of their properties in the nanometer regime (Wurster et al, ). Resolving hydrophilic and hydrophobic patterns, and the sensing of functional groups or water layer structure at the molecular scale can be realized using new developed techniques for biological samples, for example, in self‐assembled protein (s‐layer proteins) (Ladenhauf et al, ) layers in air (Wastl et al, ).…”