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

Abstract

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 (q m ) evaluated by the Langmuir model, at 25 C, was 41 mg IDM g À1 of Daisogel//[(PEI-PM)/PNIPAAm] 8.5 and 40 mg PSS g À1 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.

Sorption/release of diclofenac sodium in/from free‐standing poly(acrylic acid)/poly(ethyleneimine) multilayer films

“…Similar studies regarding the sorption mechanism of bioactive compounds by multilayer films have been previously performed, but in all cases the films were not detached from the underlying substrate . To the best of our knowledge, this is the first study which investigated the sorption mechanism of bioactive compounds by free‐standing multilayer films.…”

“…52 Similar studies regarding the sorption mechanism of bioactive compounds by multilayer films have been previously performed, but in all cases the films were not detached from the underlying substrate. 33,34 To the best of our knowledge, this is the first study which investigated the sorption mechanism of bioactive compounds by free-standing multilayer films. However, the shape of the isotherm and the best isotherm models which fit the experimental data for the free-standing PAA/PEI film are in agreement with the results obtained for other types of multilayer films undetached from the substrate.…”

“…[12][13][14][15][16] Also, the properties of multilayer films are influenced by the assembly conditions, such as the concentration, pH, ionic strength and temperature of deposition solutions. [17][18][19][20][21][22][23][24] All these parameters allowed the design of a large variety of multilayer films, which have found applications as separation membranes, 25,26 anticorrosion, and flame-retardant coatings, 27,28 antimicrobial membranes, 29,30 drug delivery systems, [31][32][33][34][35] etc.…”

“…41,42 Multilayer films have been intensively investigated as potential drug delivery systems for a large variety of low and high molar mass bioactive compounds. [31][32][33][34][35] However, in many studies the films were directly attached to the underlying substrate, this being a disadvantage for large scale applications, either because the substrate is nondegradable in living organisms, or because its degradation products are often toxic. The free-standing multilayer films could overcome these drawbacks and also might lead to the development of new drug delivery systems, such as transdermal patches.…”