Polyelectrolyte Complex Surfaces Research Articles

Application of a polyelectrolyte complex based on biocompatible polysaccharides for colorectal cancer inhibition

Strategies for incorporating water-insoluble photosensitisers (PS) in drug delivery systems have been extensively studied. In this work, we evaluate the formation, characterisation, drug sorption studies, and cytotoxicity of chitosan (CHT)/chondroitin sulphate (CS) polyelectrolyte complexes (PECs) coated with polystyrene-block-poly(acrylic acid) (PS-b-PAA) nanoparticles (NPs) loaded with chloroaluminum phthalocyanine (AlClPc). The PECs were characterised by infrared spectroscopy (FTIR), differential scanning calorimetric (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PS-b-PAA NPs on the PEC surface was confirmed by scanning electron microscopy (SEM). Additionally, optical images distinguished the PEC structures containing PS-b-PAA or PS-b-PAA/AlClPc from the unloaded PEC. Kinetic and equilibrium studies investigate the sorption capacity of the PEC/PS-b-PAA toward AlClPc. The encapsulation efficiency reached 95% at 190 μg mL−1 AlClPc after only 15 min. The Brunauer-Emmett-Teller (BET) isotherm and pseudo-second-order kinetic fitted well to the experimental data. The PS-b-PAA NPs on the PEC surfaces increase the AlClPc bioavailability and the PEC structure stabilizes the PS-b-PAA/AlClPc nanostructures. The materials were cytocompatible upon healthy VERO (kidney epithelial cells), and cytotoxic against colorectal cancerous cells (HT-29 cells). For the first time, we associate PS-b-PAA/AlClPc with a hydrophilic and cytocompatible polysaccharide matrix. We suggest the use of these materials in strategies to treat cancer by using photodynamic therapy.

Functionalizing a Polyelectrolyte Complex with Chitosan Derivatives to Tailor Membrane Surface Properties

Polyelectrolyte complex (PEC) materials show promise in the development of tunable membranes for aqueous and organic solvent separations, as well as in the creation of surface layers for fouling control. In this study, we developed a polyelectrolyte complex (PEC) functionalized by negatively charged carboxymethyl chitosan (CMC-) and positively charged quaternized chitosan (QC+) to tailor its surface properties and antibacterial efficacy. CMC- and QC+ were prepared and characterized using FT-IR and 1H NMR, which confirmed the presence of the carboxymethyl group and trimethylammonium group in CMC- and QC+ with 65.6% and 83.9% substitution, respectively. The CMC- functionalized PEC (CMC-/PEC) and QC+ functionalized PEC materials (QC+/PEC) were evaluated for their stability in water, resistance to organic and inorganic adsorption, and antibacterial action against a model microorganism, Pseudomonas putida. The results showed no release of chitosan derivatives after adsorption, and CMC-/PEC and QC+/PEC exhibited charge-based, selective repulsion of model organic and inorganic substances. Moreover, the functionalized PEC surfaces displayed lower bacterial attachment due to their smoother surfaces as compared to the bare ceramic membrane and their antimicrobial properties. Among the PEC samples, CMC-/PEC had the lowest cell attachment, while QC+/PEC showed the highest attachment due to electrostatic attraction. The ceramic and bare PEC surfaces were negligibly bactericidal, while cell viability decreased to 34.4 ± 10.2% and 30.6 ± 8.2% with the CMC-/PEC and QC+/PEC surfaces, respectively. In the filtration experiments, the unmodified PEC and CMC-/PEC showed lower rates of flux decline due to organic fouling than did the bare ceramic or QC+/PEC due to electrostatic repulsion. Furthermore, PECs as protective layers promoted much higher flux recoveries than simply backwashing the uncoated membranes. This surface tunability, then, enhances the potential of PECs either as fouling resistant materials or as a method to create a sacrificial, protective layer on surfaces that once fouled can be dissolved and re-established.

Properties of insulin–chitosan complexes obtained by an alkylation reaction on chitosan

ABSTRACTIn this study, we investigated the influence of hydrophobized chitosan on the formation and thermodynamic and surface tension properties of insulin–chitosan (I–Ch) polyelectrolyte complexes (PECs). We used an alkylation procedure to insert 12 carbon chains along the chitosan macromolecule with final substitution degrees of 5, 10, and 50%. NMR and IR spectroscopy were used to evaluate the success and extent of the hydrophobization procedure. Isothermal titration calorimetry (ITC) was used to determine the type and extent of the existing intermolecular interactions between the different constituting components of the insulin–hydrophobized chitosan PECs. Through the surface tension and diffusion coefficients at the air–water interface and ITC experiments with different I–Ch proportions, we demonstrated that around 34, 24, 25, and 60–80 insulin molecules saturated 0, 5, 10, and 50% hydrophobized chitosans, respectively. Surface tension experiments at the air–water interface demonstrated that the interaction of insulin molecules on the unmodified chitosan increased the hydrophobicity; this was mainly due to electrostatic interaction. On the contrary, insulin–hydrophobized chitosan interaction lowered the PEC hydrophobicity because of insulin alkyl chain interaction, and therefore, the hydrophilic insulin groups at the PEC surface contributed to a higher surface tension. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci.,2014,131, 39999.

Adsorption of Bovine Serum Albumin on Template-Polymerized Chitosan/Poly(methacrylic acid) Complexes

Particulate systems composed of polyelectrolyte complexes (PEC) based on chitosan and poly(methacrylic acid) were obtained via template polymerization. The resultant particles were characterized as having regions with different charge densities: chitosan predominating in the core and poly(methacrylic acid) at the surface, the particles being negatively charged, as a consequence. Albumin was adsorbed on these particles (after cross-linking with glutardialdehyde), and pH was controlled to obtain two conditions: (i) adsorption of positively charged albumin and (ii) adsorption of albumin at its isoelectric point. Adsorption isotherms and zeta-potential measurements showed that albumin adsorption was controlled by hydrogen bonding/van der Waals interactions and that brush-like structures may enhance the adsorption of albumin on these particles. It was also found that shearing can induce desorption of albumin from the PEC surface, depending on the continuous phase albumin concentration.

Investigation of the stability of surface modification by polyelectrolyte complexes — Influence of polyelectrolyte complex components and of substrates and media

Silicate surfaces were modified by adsorption of polyelectrolyte complexes (PEC) and parameters that influence the permanence of this kind of surface modification were investigated; for example, different polyelectrolyte (PEL) components, substrate surface charge density and interacting media (pH, salt). The PEL tested were poly(ethyleneimine)s differing in the molar mass, poly(diallyldimethylammonium chloride) and a copolymer of maleic acid and propene. For sensitive detection of the polyanion concentration the poly(maleic acid-co-propene) was labelled with a fluorescent dye. To obtain more comprehensive information about the performance of the surface charge modification the results of PEL titration, electrophoretic mobility investigations, scanning force microscopy (SFM) and fluorescence measurements have been compared. Non-stoichiometric PECs were able to recharge the negatively charged powders and to generate cationic surface charges. However, the stability of the modification layer has been influenced by rinsing the PEC-modified substrate (MS-P/Polymin P) with 10 −2 mole/l NaOH that led to an increase in the surface charge density and the zeta potential due to desorption of the polyanion from the surface of the polymer layer. The adsorbed amounts were found to be dependent on the NaOH concentration. The addition of 10 −2 mole/l HCl partly causes the release of the PEC and a negative surface charge density has been observed, whereas the rinsing with NaOH has always been more effective than rinsing with HCl. Substituting the weak Polymin P by PDADMAC leads to decreasing desorbed amounts. The decrease of the substrate's surface charge density and the addition of low molecular weight salts strongly reduce the stability of the PEC surface layer.

Interaction of fibrinogen with solid surfaces of varying charge and hydrophobic—hydrophilic balance: II. Dynamic exchange between surface and solution molecules

In the present work, dynamic aspects of the interaction between fibrinogen and three model polyelectrolyte-complex (PEC) surfaces (one negatively charged, one neutral, and one positively charged) were investigated, the static aspect having been studied previously [Schmitt et al. J. Colloid Interface Sci. 92, 25 (1983)]. The method consists of carrying out preliminary adsorption with radiolabeled fibrinogen and subsequently exposing the surface to a solution of nonlabeled fibrinogen. The radioactivity of the surface is followed continuously as a function of time and, in this way, a precise time dependence of the solution—surface exchange process is obtained. It was shown that in the pseudoplateau region of the isotherm, exchange between solution and interface takes place at two significantly different rates, so that three populations of adsorbed fibrinogen have to be considered: nonexchanging, rapidly exchanging, and slowly exchanging. Lower on the isotherm a single rate of exchange was observed for the negatively charged and neutral surfaces. This rate was similar to that of the slow exchange process occurring at higher concentration. For the positively charged surface, two distinct exchange processes were observed at low as well as at high concentration. No obvious correlation could be found between exchange behavior and the varying characteristics of the different PEC surfaces, namely, charge and hydrophobicity. Taking the present results together with those published previously [Brash et al. Trans. Amer. Soc. Artif. Int. Organs 20, 69 (1974); Brash and Samak, J. Colloid Interface Sci. 65, 495 (1978)] it is possible to claim as a general rule that the “equilibrium” between an adsorbed protein layer and its solution is only partly reversible, since we find that part of the surface layer is exchangeable and part is not. It is worth noting that this conclusion emerges from experiments conducted over a wide range of time intervals: hours (this work with fibrinogen) versus days [Brash and Samak, J. Colloid Interface Sci. 65, 495 (1978) with albumin].