Monolayers of Poly(styrene/α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol) Microparticles Formed by Controlled Self-Assembly with Potential Application as Protein-Repelling Substrates

The kinetics of the self-assembly of poly­(styrene/α-<i>tert</i>-butoxy-ω-vinylbenzyl-polyglycidol) microparticles on poly­(allylamine hydrochloride)-derivatized silicon/silica substrate was determined by direct AFM imaging and streaming potential (SP) measurements. The kinetic runs acquired under diffusion-controlled transport were quantitatively interpreted in terms of the extended random sequential adsorption (RSA) model. This allowed confirmation of a core/shell morphology of the microparticles. The polyglycidol-rich shell of thickness equal to 25 nm exhibited a fuzzy structure that enabled penetration of particles into each other resulting in high coverage inaccessible for ordinary microparticles. The SP measurements interpreted by using the 3D electrokinetic model confirmed this microparticle structure. Additionally, the acid–base characteristics of the microparticle monolayers were determined for a broad pH range. By using the streaming potential measurements, human serum albumin (HSA) adsorption on the microparticle monolayers was investigated under in situ conditions. It was confirmed that the protein adsorption was considerably lower than for the reference case of bare silicon/silica substrate under the same physicochemical conditions. This effect was attributed to the presence of the shell diminishing the protein/microparticle physical interactions

Spheroidal Microparticle Monolayers Characterized by Streaming Potential Measurements

An efficient method was developed enabling the synthesis of spheroidal polymer microparticles. Thorough physicochemical characteristics of the particles were acquired comprising the size, shape, electrophoretic mobility, and the diffusion coefficient. The particles were monodisperse, and their shape was well-fitted by prolate spheroids having the axis ratio equal to 4.17. Knowing the diffusion coefficient, their hydrodynamic diameter of 449 nm was calculated, which matched the value derived from Brenner’s analytical expression. Particle deposition kinetics on mica and silicon/silica substrates, modified by poly­(allylamine hydrochloride) (PAH) adsorption, was studied by optical microscopy and AFM imaging. The validity of the random sequential adsorption model was confirmed. Additionally, monolayers of the particles on these substrates were thoroughly characterized <i>in situ</i> by the streaming potential measurements for different ionic strengths. These measurements confirmed that the ζ potential change with the spheroidal particle coverage is less abrupt than for spheres and agrees with theoretical predictions. Exploiting these results, a useful analytical expression was derived that allows one to calculate the spheroidal particle coverage <i>in situ</i> <i>via</i> the streaming potential measurements. This expression, especially accurate for low coverage range, can be used for a quantitative interpretation of adsorption and desorption kinetics of anisotropic macromolecules, <i>e.g.</i>, proteins on solid substrates