Sorption and release of drugs in/from cross-linked poly(ethyleneimine) multilayer films deposited onto silica microparticles

Polyelectrolyte Multilayers: An Overview on Fabrication, Properties, and Biomedical and Environmental Applications

Polyelectrolyte multilayers are versatile materials that are used in a large number of domains, including biomedical and environmental applications. The fabrication of polyelectrolyte multilayers using the layer-by-layer technique is one of the simplest methods to obtain composite functional materials. The properties of the final material can be easily tuned by changing the deposition conditions and the used building blocks. This review presents the main characteristics of polyelectrolyte multilayers, the fabrication methods currently used, and the factors influencing the layer-by-layer assembly of polyelectrolytes. The last section of this paper presents some of the most important applications of polyelectrolyte multilayers, with a special focus on biomedical and environmental applications.

Hydrogels Based on Imino-Chitosan Amphiphiles as a Matrix for Drug Delivery Systems

This paper reports new formulations based on chitosan, citral, and diclofenac sodium salt (DCF). The central idea was to encapsulate an anionic drug into a polycationic hydrogel matrix in order to increase the intermolecular forces between them and thus to ensure slower drug release, while citral was used as a penetration enhancer to assure efficient delivery of the drug. Hydrogels without drug were also synthesized and used as a reference. The structure, morphology, and supramolecular architecture of the drug delivery systems were evaluated by FTIR spectroscopy, scanning electron microscopy, polarized optical microscopy, and wide-angle X-ray diffraction. The drug release kinetics was monitored in vitro by UV-VIS spectroscopy, in physiological conditions, while the enzymatic and hydrolytic degradability of the hydrogels were evaluated in the presence of lysozyme and phosphate buffer saline (PBS), at 37 °C. All of the data revealed that the anionic DCF was strongly anchored into the polycationic matrix and the drug was slowly released over 7 days. Moreover, the release rate can be controlled by simple variation of the molar ratio between the polycationic chitosan and lipophilic citral.

Spectacular Selectivity in the Capture of Methyl Orange by Composite Anion Exchangers with the Organic Part Hosted by DAISOGEL Microspheres

There is a paramount need in finding sorbents endowed with selectivity in sorption of certain dyes from their mixture with other dyes from the same family. In this context, novel composite anion exchangers (CANEXs) were fabricated here by an innovative approach using silica DAISOGEL as the host for an anion exchanger (ANEX) bearing vinylbenzyl N, N-diethyl 2-hydroxyethyl ammonium moieties. Information about the outer surface versus in-pore generation of ANEX as a function of silica morphology was acquired by scanning electron microscopy. It was demonstrated that the CANEX microspheres were able to selectively capture methyl orange (MO) in binary mixtures with either methylene blue (MB) as the cationic dye or Chicago Sky Blue 6B (CSB) as the competing azo dye. The adsorption kinetics of MO and CSB were well-fitted by a pseudo-second-order model, indicating that chemisorption controlled the sorption process. Isotherms of "H" type characterized the sorption of MO, whereas "L" type isotherms described the sorption of CSB. Langmuir and Sips isotherms were the most suitable models to describe the sorption process at equilibrium. Even if only about 10 wt % of the CANEX sorbents was involved in the sorption process, the maximum sorption capacity was 180.25 mg MO/g composite and 153.86 mg CSB/g sorbent. Moreover, the CANEX sorbents exhibited a spectacular preference for MO molecules in competition with CSB at pH 5.5. Selectivity coefficient for MO in the mixture with either MB or CSB was 370 and 38.4, respectively. Removal efficiency of MO remained up to 100% after 10 consecutive sorption/desorption cycles.

Poly(N,N-dimethylamino)ethyl methacrylate/sodium alginate multilayers and their interaction with proteins/enzymes

The aim of the present work is to construct and investigate the properties of novel polyelectrolyte multilayers consisting of poly(N,N-dimethylamino)ethyl methacrylate (PDMAEMA) and sodium alginate (SA). The influence of PDMAEMA's pH dependent ionization degree on the charge balance, thickness and roughness of the multilayer films was assessed by potentiometric titrations, dye sorption and atomic force microscopy. Moreover, the cross-linking of PDMAEMA/SA films with a dihalogenated aromatic derivative with high reactivity (α,α'-dichloro-p-xylene) by means of Menshutkin reaction and the stability of the multilayer architecture to repeated treatments with NaOH are demonstrated. Also, the interaction of the obtained films with various proteins/enzymes (pepsin, bovine serum albumin, haemoglobin and lysozyme) is investigated. It was found that biomolecules with the isoelectric point in the acidic region of pH were adsorbed in a higher amount than the biomolecules with the isoelectric point in the basic region of pH.

Engineered non-toxic cationic nanocarriers with photo-triggered slow-release properties

A simple and versatile strategy using cationic amphiphilic diblock copolymers synthesized by a combination of ATRP and post-polymerization quaternization to prepare photo-responsive nanocarriers showing slow-release properties and low cytotoxicity was reported.

Sorption/release of bioactive species in/from cross-linked poly(ethyleneimine)/poly(N-isopropylacrylamide) films constructed onto solid surfaces

Multilayer thin films are useful materials in the fabrication of controlled drug delivery systems and in controlling drug release processes. Herein, we report the step-by-step deposition of polymer multilayers based on poly(ethyleneimine) (PEI) and poly( N-isopropylacrylamide) (PNIPAAm) mediated by pyromellitic dianhydride (PM), as cross-linker of PEI chains, onto Daisogel silica microparticles. The sorption/release properties of the resulting composite microparticles for indomethacin (IDM), diclofenac sodium salt (DS), and Ponceau SS (PSS) were followed as a function of PM concentration. The sorption properties of the [(PEI-PM)/PNIPAAm] n multilayer films for all anionic species (IDM, DS, and PSS) were influenced by the number of polymer layers and the weight ratio between cross-linker and Daisogel microparticles during the cross-linking steps. It was found that the sorbed amount of anionic compounds increased with the number of polymer layers and with the decrease of PM concentration. The Langmuir and Sips model isotherms fitted well the sorption equilibrium data. The maximum equilibrium sorption capacity ( qm) evaluated by the Langmuir model, at 25°C, was 41 mg IDM g−1 of Daisogel//[(PEI-PM)/PNIPAAm]8.5 and 40 mg PSS g−1 of Daisogel//[(PEI-PM)/PNIPAAm]8.5, for a weight percentage of PM/silica of 0.1% w/w. Cumulative release of IDM was faster and higher than PSS in the first 5 h, while PSS was desorbed with a constant rate for 30 h, supporting a sustained release from Daisogel//[(PEI-PM)/PNIPAAm] n composite microparticles.