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Engineering of multifunctional drug nanocarriers combining stability and good release properties remains a great challenge. In this work, natural polymers κ-carrageenan (κ-CAR) and chitosan (CS) were deposited onto olive oil nanoemulsion droplets (NE) via layer-by-layer (LbL) self-assembly to study the release mechanisms of the anti-inflammatory diflunisal (DF) as a lipophilic drug model. The nano-systems were characterized by dynamic light scattering (DLS), zeta potential (ζ-potential) measurements, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS) and Fourier transform infrared spectroscopy (FTIR) to confirm the NE-coating with polymer layers. In addition, kinetic release studies of DF were developed by the dialysis diffusion bag technique. Mathematical models were applied to investigate the release mechanisms. The results showed that stable and suitably sized nanocapsules (~300 nm) were formed. Also, the consecutive adsorption of polyelectrolytes by charge reversal was evidenced. More interestingly, the drug release mechanism varied depending on the number of layers deposited. The nanosized systems containing up to two layers showed anomalous transport and first order kinetics. Formulations with three and four layers exhibited Case II transport releasing diflunisal with zero order kinetics. Hence, our results suggest that these polyelectrolyte nanocapsules have great potential as a multifunctional nanocarrier for drug delivery applications.

The pharmaceutical applications of cyclodextrins (CDs), cyclic oligosaccharides capable of including hydrophobic molecules inside their cavities, have been known for decades. Besides the solubilising and encapsulating abilities of natural and modified CDs due to the formation of inclusion complexes, there is an increasing interest in organized macrostructures based on CDs as potential drug delivery devices and gene carrier systems. The present review discusses first the case of drug carriers based on monomeric modified CDs (amphiphilic and CD core-star polymers), in which self-assembly plays a major role. Polyrotaxanes, i.e., CDs threaded onto a polymer chain, are then reviewed in relation to their pharmaceutical applications. Finally, covalently linked CDs, either by grafting or crosslinking, are analyzed, including more complex structures formed by assembling CDcontaining networks or chains. We have tried along this review to cover the most recent developments on these structures for drug delivery in a "beyond the cyclodextrin" approach. The review will be helpful, both for readers who want to be introduced into the world of these remarkable structures, or for specialists who are doing research in this field.

Gels obtained by complexation of octablock star polyethylene oxide/polypropylene oxide copolymers (Tetronic 90R4) with α‐cyclodextrin (α‐CD) were evaluated as matrices for drug release. Both molecules are biocompatible so they can be potentially applied to drug delivery systems. Two different types of matrices of Tetronic 90R4 and α‐CD were evaluated: gels and tablets. These gels are capable to gelifying in situ and show sustained erosion kinetics in aqueous media. Tablets were prepared by freeze‐drying and comprising the gels. Using these two different matrices, the release of two model molecules, L‐tryptophan (Trp), and a protein, bovine serum albumin (BSA), was evaluated. The release profiles of these molecules from gels and tablets prove that they are suitable for sustained delivery. Mathematical models were applied to the release curves from tablets to elucidate the drug delivery mechanism. Good correlations were found for the fittings of the release curves to different equations. The results point that the release of Trp from different tablets is always governed by Fickian diffusion, whereas the release of BSA is governed by a combination of diffusion and tablet erosion. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:197–206, 2014