Preparation of monomodal polyelectrolyte complex nanoparticles of PDADMAC/poly(maleic acid-alt-alpha-methylstyrene) by consecutive centrifugation

We report on the refinement of anionic and cationic nanoparticles of nonstoichometric polyelectrolyte complexes (PEC) by consecutive centrifugation, which was studied by dynamic light scattering (DLS), atomic force microscopy (AFM), colloid titration and infrared spectroscopy (IR). PEC dispersions were prepared by mixing poly(diallyldimethylammonium chloride) (PDADMAC) and sodium poly(maleic acid-alt-alpha-methylstyrene) (PMA-MS) at the monomolar mixing ratio of n-/n+ = 1.50 (anionic PEC) and 0.66 (cationic PEC), respectively, and the polymer concentration of c(POL) = 0.002 M. The particle size (Rh), titrable charge amount, and IR spectra were determined for both dispersions in the original state, after the first centrifugation and after the second centrifugation. Freshly prepared PEC dispersions contained two different particle sizes: around 10-25 nm (small particles) and around 100 nm (large particles). Consecutive centrifugation of freshly prepared PEC dispersions resulted in the separation of highly charged excess polyelectrolyte (PEL) and small PEC particles from a low charged coacervate phase of the desired larger PEC particles. After the second centrifugation, the coacervate phase of both dispersions PEC-1.50 and PEC-0.66 consisted of monomodal particles sizing around 100 nm. These results were supported by AFM measurements on the respective dispersions deposited on glass plates. PEC-1.50 particles tended to adopt slightly smaller sizes ( approximately 90 nm) in comparison to PEC-0.66 ones (approximately 110 nm). No significant influence of the PDADMAC molecular weight on the particle size was found. IR spectroscopy showed changes in the environment of the carboxylate groups of PMA-MS by consecutive centrifugation. The centrifuged PEC-1.50 dispersions showed remarkable long-term stability over more than a year. The high macroscopic stability of the studied PEC dispersions is presumably due to repulsive electrostatic interparticle interactions and attractive hydrophobic intraparticle interaction. The introduced monomodal PEC particles might be projected as latex analogues or as nanocarriers for drugs and proteins.     

Reversible switching of protein uptake and release at polyelectrolyte multilayers detected by ATR-FTIR spectroscopy

The reversible switching of uptake and release of the proteins lysozyme (LYZ, IEP = 11.1) and human serum albumin (HSA, IEP = 4.8) at the surface attached polyelectrolyte multilayer (PEM) consisting of poly(ethylene-imine) (PEI) and poly(acrylic acid) (PAC) is shown. Protein adsorption could be switched by pH setting due to electrostatic interaction. Adsorption of positively charged LYZ at PEM-6 took place at pH = 7.3, where the outermost PAC layer was negatively charged. Complete desorption was obtained at pH = 4, where the outermost PAC layer was neutral. Additionally the charge state of the last adsorbed PAC layer in dependence of the pH of the medium could be determined in the ATR-FTIR difference spectra by the ν(COO⁻) and ν(C=O) band due to carboxylate and carboxylic acid groups. Adsorption of negatively charged HSA at PEM-7 was achieved at pH = 7.3, where the outermost PEI layer was positively charged. Part desorption was obtained at pH = 10, where the outermost PEI layer was neutral. PEM of PEI/PAC may be used for the development of bioactive and bionert materials and protein sensors.     

Encapsulation of RNA by negatively charged human serum albumin via physical interactions

Human serum albumin (HSA) is the most abundant plasma protein and has an inherent ability to target tumor cells. It is an excellent candidate for drug delivery. However, HSA cannot form complex with DNA or RNA, because it is negatively charged under physiological conditions. In this work, we reported a simple method to prepare HSA/RNA nanoparticles mainly by physical interaction. Firstly, the solution pH is adjusted to 4.0, under which condition HSA is positively charged. It forms complex with RNA via electrostatic interaction. The solution is then heated at 75 oC for 15 min to stabilize the structure and the size of the formed complex. The HSA/RNA nanoparticle prepared by this method has a diameter about 110 nm and a narrow distribution. It is also stable for days under physiological conditions. Cellular essays demonstrate that these particles exhibit a high cellular uptake efficiency and non-toxicity to HeLa cells.     

Effect of water chemistry and aging on iron-mica interaction forces: implications for iron particle transport

The transport of particles through groundwater systems is governed by a complex interplay of mechanical and chemical forces that are ultimately responsible for binding to geological substrates. To understand these forces in the context of zero valent iron particles used in the remediation of groundwater, atomic force microscopy (AFM)-based force spectroscopy was employed to characterize the interactions between AFM tips modified with either carbonyl iron particles (CIP) or electrodeposited Fe as a function of counterion valency, temperature, particle morphology, and age. The measured interaction forces were always attractive for both fresh and aged CIP and electrodeposited iron, except in 100 mM NaCl, as a consequence of electrostatic attraction between the negatively charged mica and positively charged iron. In 100 mM NaCl, repulsive hydration forces appeared to dominate. Good agreement was found between the experimental data and predictions based on the extended DLVO (XDLVO) theory. The effect of aging on iron particle composition and morphology was assessed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) revealing that the aged particles comprising a zero valent iron core passivated by a mixture of iron oxides and hydroxides. Force spectroscopy showed that aging caused variations in the adhesive force due to the changes in particle morphology and contact area.     

On the behavior of electrokinetic streaming potential during protein filtration with fully and partially retentive nanopores

An experimental investigation of the electrokinetic streaming potentials of both fully and partially retentive nanopores as compared with the filtration progress of dilute globular protein solution under different surface charge conditions was performed using hollow fibers. The streaming potential is generated by the electrokinetic flow effect within the electric double layer of the charged surface. Depending on the solution pH, both the protein and the pore wall can be either repulsive or attractive due to the long-range electrostatic interaction. The repulsive electrostatic interaction allows the protein particles to stay in a suspended state above the outer surface of hollow fibers instead of being deposited. The apparent streaming potential value at partially retentive pores is larger than that at fully retentive pores for the oppositely charged case; however, the opposite behavior is shown for the same-charged case. The axial-position-dependent streaming potential was also observed in order to explore the development of a concentration polarization layer during the cross-flow filtration. The time evolution of the streaming potential during the filtration of protein particles is related to the filtrate flux, from which it can be found to provide useful real-time information on particle deposition onto the outer surfaces of hollow fibers.     

AFM study of the behavior of polystyrene and glass particles during the electrodeposition of copper

In this paper, the behavior of polystyrene and glass particles on a copper electrode during the electrodeposition of copper was studied using an atomic force microscope (AFM). Polystyrene or glass particles glued to the tip of the AFM cantilever were kept in contact with the surface of the electrode. The surface forces between the polystyrene or glass particle and the copper electrode were measured before, during, and after electrodeposition. These experiments revealed that glass particles do not make contact with the electrode, probably due to the repulsive hydration force. Polystyrene particles, on the other hand, make contact with the electrode, due to the attractive hydrophobic force. The AFM experiments were correlated with sedimentation co-deposition experiments of polystyrene and glass particles with copper. It was found that 80% of the polystyrene particles added to the plating solution incorporated with copper, while only 0.25% of the glass particles co-deposited under the same conditions.     

Needlelike and spherical polyelectrolyte complex nanoparticles of poly(l-lysine) and copolymers of maleic acid

We report on the bulk and surface properties of dispersions consisting of nonstoichiometric polyelectrolyte complex (PEC) nanoparticles. PEC nanoparticles were prepared by mixing poly(l-lysine) (PLL) or poly(diallyldimethylammonium chloride) (PDADMAC) with poly(maleic acid-co-alpha-methylstyrene) (PMA-MS) or poly(maleic acid-co-propylene) (PMA-P). The monomolar mixing ratio was n-/n+ = 0.6, and the concentration ranged from 1 to 6 mmol/L. Subsequent centrifugation enabled the separation of the excess polycation, resulting in a stable coacervate phase further used in the experiments. The bulk phase parameters turbidity and hydrodynamic radius (R(h)) of the PEC nanoparticles showed a linear dependence on the total polymer content independently of the mixed polyelectrolytes. This can be interpreted by the increased collision probability of the polyelectrolyte chains when the overlap concentration is approached or exceeded. Different morphologies of the cationic PEC nanoparticles, which were solution-cast onto Si supports, were obtained by atomic force microscopy (AFM). The combinations of PLL/PMA-MS and PDADMAC/PMA-MS revealed more or less hemispherical particle shapes, whereas that of PLL/PMA-P revealed an elongated needlelike particle shape. Circular dichroism and attenuated total reflection Fourier transform infrared (ATR-FTIR) measurements proved the alpha-helical conformation for the PEC PLL/PMA-P and the random coil conformation for the PEC PLL/PMA-MS. We conclude that stiff alpha-helical PLL induces anisotropic elongated PEC nanoparticles, whereas randomly coiled PLL forms isotropic spherical PEC nanoparticles.     

Interpolyelectrolyte complexes: a single-molecule insight

Polyelectrolyte (PE) complexes (PECs) between long polycation poly(methacryloyloxyethyl dimethylbenzylammonium chloride) and short polyanion polystyrene sulfonic acid adsorbed onto mica were studied by atomic force microscopy. If one component is taken in excess, then a rapid coupling of the oppositely charged polyions first leads to the formation of nonequilibrium structures when collapsed PEC particles coexist with unreacted PEs molecules. The equilibrium PEC particles possess micelle-like core-shell morphology if the short polyion is taken in excess. When long PE is given in excess, equilibrium PECs are stabilized by wrapping the long polyion around hydrophobic segments of the PEC. We propose that transformations of initially formed nonequilibrium aggregates proceed through slow reactions (addition or/and substitution) of primary complexes with unreacted PEs chains, which finally leads to equilibrium PECs with optimized morphology. As expected, the mixing of oppositely charged PEs in a near-stoichiometric ratio leads to highly aggregated water-insoluble PECs.     

Direct measurement of hydrophobic particle–bubble interactions in aqueous solutions by atomic force microscopy: Effect of particle hydrophobicity

Direct measurements of the interaction forces between a spherical silica particle and a small air bubble have been conducted in aqueous electrolyte solutions by using an atomic force microscope (AFM). The silica particle was hydrophobized with a silanating reagent, and the interaction forces were measured by using several particles with different surface hydrophobicities. In the measured force curves, a repulsive force was observed at large separation distances as the particle moved towards the bubble. The origin of the repulsive force was attributed to an electrostatic double-layer force because both the particle and bubble were negatively charged. After the repulsive force, an extremely long-range attractive force acted between the surfaces. These results indicate that the intervening thin water film between the particle and bubble rapidly collapsed, resulting in the particle penetrating the bubble.

The instability of the thin water film between the surfaces suggests the existence of an additional attractive force. By comparing the repulsive forces of the obtained force curves with the DLVO theory, the rupture thickness was estimated. The hydrophobicity of the particle did not significantly change the rupture thickness, whereas the pH of the solution is considered to be a critical factor.     

Atomic force microscopy of human serum albumin (HSA) on poly(styrene/acrolein) microspheres

Atomic Force Microscopy (AFM) in the tapping mode was used for the observation of bare poly (styrene/acrolein) P(SA) microspheres and microspheres with attached HSA. Prior to the AFM observations the P(SA) microspheres were immobilized covalently on the surface of quartz slides modified with -aminopropyltriethoxysilane. Atomic Force Microscopy pictures were registered for the dry samples. The partial coalescence of the P(SA) microspheres connected to the quartz surface with amino groups has been observed. The AFM pictures of the single P(SA) microspheres revealed that the surface of these particles is smooth and that any irregularities, if present, do not exceed 1 nm. The surface of microspheres with attached HSA has very clearly different morphology with regular pattern of HSA macromolecules. Cracks on the surfaces of some microspheres with HSA revealed that protein macromolecules are attached to these particles in several layers. In the case of some other microspheres the defects in protein attachment allowed the observation of the border between the bare surface of the P(SA) microspheres and the surface covered with protein macromolecules. Comparison of the thickness of the HSA layers on the P(SA) microspheres with the dimensions of HSA macromolecules, determined earlier from the x-ray studies, suggests that the first layer, 3.0±0.2 nm thick, is formed of the HSA macromolecules arranged flatly on the surface whereas protein macromolecules in the subsequent layers, each 8.6±1 nm thick, are adsorbed protruding from the surface.     

Change of zeta potential of biocompatible colloidal oxide particles upon adsorption of bovine serum albumin and lysozyme

The amounts of negatively charged bovine serum albumin and positively charged lysozyme adsorbed on alumina, silica, titania, and zirconia particles (diameters 73 to 271 nm) in aqueous suspensions are measured. The adsorbed proteins change the zeta potentials and the isoelectric points (IEP) of the oxide particles. The added to adsorbed protein ratios at pH 7.5 are compared with the protein treated particle zeta potentials. It is found that the amounts of adsorbed proteins on the alumina, silica, and titania (but not on the zirconia) particle surfaces are highly correlated with the zeta potential. For the slightly less hydrophilic zirconia particles high amounts of protein adsorption are observed even under repulsive electrostatic conditions. One reason could be that the hydrophobic effect plays a more important role for zirconia than electrostatic interaction.     

Protein-protein interactions in complex cosolvent solutions.

The effects of various kosmotropic and chaotropic cosolvents and salts on the intermolecular interaction potential of positively charged lysozyme is evaluated at varying protein concentrations by using synchrotron small-angle X-ray scattering in combination with liquid-state theoretical approaches. The experimentally derived static structure factors S(Q) obtained without and with added cosolvents and salts are analysed with a statistical mechanical model based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential, which accounts for repulsive and attractive interactions between the protein molecules. Different cosolvents and salts influence the interactions between protein molecules differently as a result of changes in the hydration level or solvation, in charge screening, specific adsorption of the additives at the protein surface, or increased hydrophobic interactions. Intermolecular interaction effects are significant above protein concentrations of 1 wt %, and with increasing protein concentration, the repulsive nature of the intermolecular pair potential V(r) increases markedly. Kosmotropic cosolvents like glycerol and sucrose exhibit strong concentration-dependent effects on the interaction potential, leading to an increase of repulsive forces between the protein molecules at low to medium high osmolyte concentrations. Addition of trifluoroethanol exhibits a multiphasic effect on V(r) when changing its concentration. Salts like sodium chloride and potassium sulfate exhibit strong concentration-dependent changes of the interaction potential due to charge screening of the positively charged protein molecules. Guanidinium chloride (GdmCl) at low concentrations exhibits a similar charge-screening effect, resulting in increased attractive interactions between the protein molecules. At higher GdmCl concentrations, V(r) becomes more repulsive in nature due to the presence of high concentrations of Gdm(+) ions binding to the protein molecules. Our findings also imply that in calculations of thermodynamic properties of proteins in solution and cosolvent mixtures, activity coefficients may not generally be neglected in the concentration range above 1 wt % protein.     

Hydrophobic attraction as revealed by AFM force measurements and molecular dynamics simulation

Spherical calcium dioleate particles ( approximately 10 mum in diameter) were used as AFM (atomic force microscope) probes to measure interaction forces of the collector colloid with calcite and fluorite surfaces. The attractive AFM force between the calcium dioleate sphere and the fluorite surface is strong and has a longer range than the DLVO (Derjaguin-Landau-Verwey-Overbeek) prediction. The AFM force between the calcium dioleate sphere and the mineral surfaces does not agree with the DLVO prediction. Consideration of non-DLVO forces, including the attractive hydrophobic force and the repulsive hydration force, was necessary to explain the experimental results. The non-DLVO interactions considered were justified by the different interfacial water structures at calcite- and fluorite-water interfaces as revealed by the numerical computation experiments with molecular dynamics simulation.     

Changes in the interaction characteristics of polyelectrolyte complex covered silica surfaces

The adsorption of polyelectrolyte complexes, PEC, made from the cationic poly (diallyldimethylammonium) chloride (PDADMAC) and the anionic maleic acid-co-propene copolymer (MA-P) on a Si-wafer surface has been studied. The application of highly diluted colloidally dispersed PEC solutions led to the deposition of single PEC particles onto the surface of the Si-wafer. The interaction forces of the heterogeneously covered surface were monitored by direct force measurements with an atomic force microscope (AFM) in the force volume mode. On the surface of a single PEC particle drastic changes in the interaction forces were found in comparison with the unmodified Si-wafer: in all force vs. distance curves a strong increase of the adhesion was measured that can be attributed to the formation of electrostatic bonds between the negatively charged Si₃N₄-tip and the cationic excess charge of the PEC. Additionally, the behavior during approach of both surfaces has been distinct: at pH 6.1 we see a long range electrostatic attraction between the tip and the PEC particle. The attraction becomes even stronger at pH 4.1, because of an increased positive net charge. Generally, a heterogeneous surface with a wide variety of interaction features can be created by the adsorption of PEC particles.     

Lysozyme binding to poly(4-vinyl-N-alkylpyridinium bromide)

The adsorption behavior of polycations at ionic strengths (I) ranging from 0.001 to 0.1 onto silicon wafers was studied by means of ellipsometry, contact angle measurements and atomic force microscopy (AFM). Polycations chosen were bromide salts of poly(4-vinylpyridine) N-alkyl quaternized with linear aliphatic chains of 2 and 5 carbon atoms, QPVP-C2 and QPVP-C5, respectively. Under I=0.001 the reduction of screening effects led to low adsorbed amounts of QPVP-C2 or QPVP-C5 (1.0±0.1 mg/m²), arising from the adsorption of extended chains. Upon increasing I to 0.1, screening effects led to conformational changes of polyelectrolyte chains in solution and to higher adsorbed amount values (1.9±0.2 mg/m²). Advancing contact angle θ_a measurements performed with water drops onto QPVP-C2 and QPVP-C5 adsorbed layers varied from (45±2)° to (50±5)°, evidencing the exposure of both hydrophobic alkyl groups and charged moieties. The adsorption of lysozyme (LYZ) molecules to QPVP-C5 layers was more pronounced than to QPVP-C2 films. Antimicrobial effect of LYZ bound to QPVP-C2 or QPVP-C5 layers or to Si wafers was evaluated with enzymatic assays using Micrococcus luteus as substrates. The adsorption behavior of QPVP-C2 and QPVP-C5 at the water–air interface was studied by means of surface tension measurements. Only QPVP-C5 was able to reduce water surface tension. Mixtures of LYZ and QPVP-C5 were more efficient in reducing surface tension than pure LYZ solution, evidencing co-adsorption at liquid–air interface. Moreover, antimicrobial action observed for mixtures of LYZ and QPVP-C5 was more pronounced than that measured for pure LYZ. Hydrophobic interaction between LYZ and QPVP-C5 in solution seems to drive the binding and to preserve LYZ secondary structure.     

Toward the description of electrostatic interactions between globular proteins: potential of mean force in the primitive model

Monte Carlo simulations are used to calculate the exact potential of mean force between charged globular proteins in aqueous solution. The aim of the present paper is to study the influence of the ions of the added salt on the effective interaction between these nanoparticles. The charges of the model proteins, either identical or opposite, are either central or distributed on a discrete pattern. Contrarily to Poisson-Boltzmann predictions, attractive, and repulsive direct forces between proteins are not screened similarly. Moreover, it has been shown that the relative orientations of the charge patterns strongly influence salt-mediated interactions. More precisely, for short distances between the proteins, ions enhance the difference of the effective forces between (i) like-charged and oppositely charged proteins, (ii) attractive and repulsive relative orientations of the proteins, which may affect the selectivity of protein/protein recognition. Finally, such results observed with the simplest models are applied to a more elaborate one to demonstrate their generality.     

Solute distribution and stability in emulsion-based delivery systems: an EPR study

Adsorption and desorption of human serum albumin (HSA) from aqueous solutions on mica were studied using AFM and in situ streaming potential measurements. A quantitative interpretation of these experiments was achieved in terms of the theoretical model postulating a 3D adsorption of HSA molecules as discrete particles. These measurements, performed for various ionic strength, allowed one to determine the coverage of HSA as a function of the zeta potential of mica. This allowed one to determine the amount of irreversibly bound HSA as a function of the ionic strength. It was found that the coverage of irreversibly adsorbed HSA increased from 0.52 mg m(-2) for I=1.3×10(-3) M to 1.6 mg m(-2) for I=0.15M (pH=3.5). The significant role of ionic strength was attributed to the lateral electrostatic repulsion among adsorbed HSA molecules, positively charged at this pH value. This was quantitatively interpreted in terms of the effective hard particle concept previously used for colloid particles. The experimental results confirmed that monolayers of irreversibly bound HSA of a well-controlled coverage can be produced by adjusting the ionic strength of the suspension.     

Relationship between interfacial forces measured by colloid-probe atomic force microscopy and protein resistance of poly(ethylene glycol)-grafted poly(L-lysine) adlayers on niobia surfaces

Adsorbed layers of "comb-type" copolymers consisting of PEG chains grafted onto a poly(l-lysine) (PLL) backbone on niobium oxide substrates were studied by colloid-probe AFM in order to characterize the interfacial forces associated with coatings of varying architectures (PEG/PLL ratios and PEG chain lengths) and their relevance to protein resistance. The steric and electrostatic forces measured varied substantially with the architecture of the PLL-g-PEG copolymers. Varying the ionic strength of the buffer solutions enabled discrimination between electrostatic and steric-entropic contributions to the net interfacial force. For high PEG grafting densities the steric component was most prominent, but at low ionic strengths and high grafting densities, a repulsive electrostatic surface force was also observed; its origin was assigned to the niobia charges beneath the copolymer, as insufficient protonated amine groups in the PLL backbone were available for compensation of the oxide surface charges. For lower grafting densities and lower ionic strengths there was a substantial attractive electrostatic contribution arising from interaction of the electrical double layer arising from the protonated amine groups, with that of the silica probe surface (as under low ionic strength conditions, the electrical double layer was thicker than the PEG layer). For these PLL-g-PEG coatings the net interfacial force can thus be a markedly varying superposition of electrostatic and steric-entropic contributions, depending on various factors. The force curves correlate with protein adsorption data, demonstrating the utility of AFM colloid-probe force measurements for quantitative analysis of surface forces and how they determine interfacial interactions with proteins. Such characterization of the net interfacial forces is essential to elucidate the multiple types of interfacial forces relevant to the interactions between PLL-g-PEG coatings and proteins and to advance interpretation of protein adsorption or repellence beyond the oversimplified steric barrier model; in particular, our data demonstrate the importance of an ionic-strength-dependent minimum PEG layer thickness to screen the electrostatic interactions of charged interfaces.     

The shape of protein–polymer conjugates in dilute solution

Protein–polymer conjugation can significantly affect many different aspects of protein behavior, ranging from their solution properties to their ability to form solution and bulk nanostructured materials. An underlying fundamental question is how the molecular design affects the shape of the conjugate and, consequently, its properties. This work measures the molecular configuration of model protein–polymer conjugates in dilute solution using small-angle neutron scattering (SANS) and uses quantitative model fitting to understand the shape of the molecules. Form factor measurements of four model bioconjugates of the red fluorescent protein mCherry and the polymers poly(N-isopropylacrylamide), poly(hydroxypropyl acrylate), poly(oligoethylene glycol acrylate), and poly(ethylene glycol) show that these protein–polymer conjugates are well described by a recently developed scattering function for colloid–polymer conjugates that explicitly incorporates excluded volume interactions in the polymer configuration. In the regime where the protein does not exhibit strong interactions with the polymer, modeling the protein–polymer interactions using a purely repulsive Weeks–Chandler–Andersen potential also leads to a coarse-grained depiction of the conjugate that agrees well with its scattering behavior. The coarse-grained model can additionally be used for systems with varying protein–polymer interactions, ranging from purely repulsive to strongly attractive, which may be useful for conjugates with strong electrostatic or hydrophobic attractive interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 292–302     

Preparation and adsorption of refined polyelectrolyte complex nanoparticles

We report on bulk and surface properties of centrifuged nonstoichiometric polyelectrolyte complex (PEC) dispersions. PECs were prepared by mixing poly(diallyldimethylammonium chloride) (PDADMAC) and sodium poly(maleic acid-co-alpha-methylstyrene) (PMA-MS) at the monomolar mixing ratio of 0.6 and polymer concentration >/=1 mmol/l. Centrifugation of initial PEC dispersions revealed three phases: supernatant (SUP), coacervate (COAC), and an insoluble precipitate. Mass, turbidity, particle hydrodynamic radii (R(h)), and the titratable charge amount were determined for those phases. The turbid COAC phase consisted of 200-nm nanoparticles and carried 60% of the polymer mass and 20% of the titratable charge amount of the initial PEC dispersion. The SUP phase showed no turbidity and no such nanoparticles, but carried 80% of the initial titratable charge amount, presumably caused by excess polycations. Furthermore, linear dependences of turbidity and R(h) on COAC concentration was observed. COAC adsorption was studied at polyelectrolyte multilayer (PEM) modified silicon surfaces in dependence on both adsorption time and concentration using attenuated total-reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The adsorption data were fitted by the simple Langmuir model. Comparison of COAC particles and polystyrene latices revealed similar adsorption features. SEM and AFM measurements resulted in hemispherically shaped adsorbed COAC particles with coverages >/=25%, whose calculated volumes correlated well with those in dispersion obtained by PCS.