Methodologies based on light scattering measurements continue to dominate particle size instrumentation. With this review, we report the introduction of a new dynamic light scattering technique ― diffusion wave spectroscopy ― which holds great promise for determining particle size measurements in concentrated or optically opaque systems (see Photon Correlation Spectroscopy). The use of acoustic spectroscopy also appears to be a promising approach, although relatively few reports have appeared thus far (see Other Techniques)

Particle size analysis

Charge transport processes in nonconjugated redox-active polymers with electrolytes were studied using a diffusion-cooperative model. For the first time, we quantitatively rationalized that the limited Brownian motion of the redox centers bound to the polymers resulted in the 103–4-fold decline of the bimolecular and heterogeneous charge transfer rate constants, which had been unexplained for half a century. As a next-generation design, a redox-active supramolecular system with high physical mobility was proposed to achieve the rate constant as high as in free solution system (>107 M–1 s–1) and populated site density (>1 mol/L).

Diffusion-Cooperative Model for Charge Transport by Redox-Active Nonconjugated Polymers

Nonfouling surfaces capable of reducing protein adsorption are highly desirable in a wide range of applications. Coating of surfaces with poly(ethylene oxide) (PEO), a water-soluble, nontoxic, and nonimmunogenic polymer, is most frequently used to reduce nonspecific protein adsorption. Here we show how to prepare dense PEO brushes on virtually any substrate by tethering PEO to polydopamine (PDA)-modified surfaces. The chain lengths of hetero-bifunctional PEOs were varied in the range of 45–500 oxyethylene units (Mn = 2000–20 000). End-tethering of PEO chains was performed through amine and thiol headgroups from reactive polymer melts to minimize excluded volume effects. Surface plasmon resonance (SPR) was applied to investigate the adsorption of model protein solutions and complex biologic medium (human blood plasma) to the densely packed PEO brushes. The level of protein adsorption of human serum albumin and fibrinogen solutions was below the detection limit of the SPR measurements for all PEO chains end...

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Nonfouling poly(ethylene oxide) layers end-tethered to polydopamine

Solid lipid nanoparticles for hydrophilic biotech drugs: optimization and cell viability studies (Caco-2 & HEPG-2 cell lines).

Polystyrene-block-poly(methacrylic acid) micelles were chemically attached to an activated silicon nitride surface using a 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide methiodide coupling reaction. It has been found that this attachment method is very efficient from mixed 1,4-dioxane−water solvents and less efficient in purely aqueous media. The modified surfaces were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental conditions for surface attachment have been found such that no changes in micellar size or polydispersity occur. The SEM and AFM images allow an additional method for the evaluation of size distributions of micelles. A comparison with the quasi-elastic light scattering data from solutions shows that the distribution functions based on the SEM and AFM data for dried micelles fixed on the surface correlate reasonably well with the light scattering data on micelles in solutions.

Č. Koňák

Papers

Quasielastic light scattering from polymers, colloids and gels