Furthermore, a differential inner/outer functionalization can activate the external surface in order to facilitate the interaction with species grafted on the external side [11]. Compared to conventional form of dosage, micro- and nanomaterial-based drug delivery systems have many advantages, such as reduced release rate, minimized harmful side effects and improved therapeutic efficiency [7, 14, 15]. However, the premature release of active species from the cargo-loaded selleck compound micropillars can represent a drawback. Hence, a triggered and prolonged release

of guest molecules upon Selleckchem 4EGI-1 specific stimuli may be desired. This stimulus for the drug delivery system can be induced by physical [16], chemical [17] or biogenic signals [18]. In this context, polyelectrolyte multilayer (PEM) has been widely explored to create coatings on the surface of a number of inorganic structures for the controlled delivery of drugs [19–23]. The PEM assembly is based on the layer-by-layer (LbL) approach which involves alternative adsorption of oppositely charged polyelectrolytes to create multilayer architectures in a conformal manner [24–26]. By the incorporation

of appropriate responsive polyelectrolytes, the PEM can allow the controlled release of active agents on the basis of stimuli such as pH [27], temperature [28] or ionic strength [29]. Particularly, Tozasertib purchase pH-sensitive systems are of great interest in drug delivery due to the variations in pH that the human body exhibits. For instance, the gastrointestinal tract exhibits pH ranging from acidic in the stomach (pH 2) to basic in the intestine (pH 5 to 8). And compared to healthy tissues and the bloodstream (pH 7.4), most cancer and wound tissues constitute an acidic environment check (pH 7.2 to 5.4) [30]. pH-responsive PEM films contain ionizable

groups which exhibit volume changes in response to variations in pH and facilitate drug delivery control [31]. The polyelectrolyte pair comprising poly(allylamine hydrochloride) (PAH) and sodium poly(styrene sulfonate) (PSS) has been extensively investigated for drug delivery applications due to their remarkable sensitivity to pH and improved biocompatibility [20, 32]. The deposition of the first layer of cationic polyelectrolyte PAH on the internal sidewalls of hollow micropillars is favoured by the negative charge of the SiO2 surface above the isoelectric point (pH 2 to 3) [33]. Then, the anionic PSS is deposited onto PAH by electrostatic attraction. Furthermore, to facilitate the infiltration of the polyelectrolytes inside the pores and obtain a uniform surface coating without pore blockage, a multivalent salt such as CaCl2 can be added to the aqueous polyelectrolyte solution. The presence of multivalent salts causes a much stronger shrinking of the polyelectrolyte chain owing to a higher attraction between charged monomers along the chain [34, 35].