•Inhalable hyaluronic acid microparticles with high payload of salbutamol sulphate was fabricated by spray drying technique.•The Inhalable microparticles possessed good mucoadhesive property and sustained release profiles in vitro.•The Inhalable microparticles exhibited longer lung retention and lower systemic exposure compared to plain drug powder.The aim of this study was to investigate the feasibility of using hyaluronic acid (HA), a biomucoadhesive carbohydrate polymer to prolong the pulmonary retention and reduce the systemic exposure of inhaled medicine. Salbutamol sulphate (SAS), a model bronchodilator, was co-spray dried with HA into inhalable microparticles, which were subsequently characterized as spherical shape with wrinkled surface. The fine particle fraction of the microparticles tested by using the Next Generation Impactor was over 30% without the aid of any carrier, and the in vitro release of SAS lasted for 20 h. Compared to spray-dried plain SAS powders, the SAS-loaded HA microparticles possessed enhanced biomucoadhesive property in vitro and had much longer pulmonary retention and reduced systemic exposure in vivo. By incorporation, the pulmonary retention time of SAS was prolonged from 2 h to 8 h while the maximum concentration in plasma was reduced significantly from 2267.7 ng/mL to 566.38 ng/mL. These results suggested that inhaled HA microparticles could be a promising formulation strategy to enhance the therapeutic efficacy of inhaled medicines.

Understanding the delivery dynamics of nucleic acid nanocarriers is fundamental to improve their design for therapeutic applications. We investigated the carrier structure–function relationship of lipid–polymer hybrid nanoparticles (LPNs) consisting of poly(dl-lactic-co-glycolic acid) (PLGA) nanocarriers modified with the cationic lipid dioleoyltrimethyl-ammoniumpropane (DOTAP). A library of siRNA-loaded LPNs was prepared by systematically varying the nitrogen-to-phosphate (N/P) ratio. Atomic force microscopy (AFM) and cryo-transmission electron microscopy (cryo-TEM) combined with small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM) studies suggested that the siRNA-loaded LPNs are characterized by a core–shell structure consisting of a PLGA matrix core coated with lamellar DOTAP structures with siRNA localized both in the core and in the shell. Release studies in buffer and serum-containing medium combined with in vitro gene silencing and quantification of intracellular siRNA suggested that this self-assembling core–shell structure influences the siRNA release kinetics and the delivery dynamics. A main delivery mechanism appears to be mediated via the release of transfection-competent siRNA–DOTAP lipoplexes from the LPNs. Based on these results, we suggest a model for the nanostructural characteristics of the LPNs, in which the siRNA is organized in lamellar superficial assemblies and/or as complexes entrapped in the polymeric matrix.

The purpose of this study was to develop a PLGA microspheres-based donepezil (DP) formulation which was expected to sustain release of DP for one week with high encapsulation efficiency (EE). DP derived from donepezil hydrochloride was encapsulated in PLGA microspheres by the O/W emulsion-solvent evaporation method. The optimized formulation which avoided the crushing of microspheres during the preparation process was characterized in terms of particle size, morphology, drug loading and EE, physical state of DP in the matrix and in vitro and in vivo release behavior. DP microspheres were prepared successfully with average diameter of 30 µm, drug loading of 15.92 ± 0.31% and EE up to 78.79 ± 2.56%. Scanning electron microscope image showed it has integrated spherical shape with no drug crystal and porous on its surface. Differential scanning calorimetry and X-ray diffraction results suggested DP was in amorphous state or molecularly dispersed in microspheres. The Tg of PLGA was increased with the addition of DP. The release profile in vitro was characterized with slow but continuous release that lasted for about one week and fitted well with first-order model, which suggested the diffusion governing release mechanism. After single-dose administration of DP microspheres via subcutaneous injection in rats, the plasma concentration of DP reached peak concentration at 0.50 d, and then declined gradually, but was still detectable at 15 d. A good correlation between in vitro and in vivo data was obtained. The results suggest the potential use of DP microspheres for treatment of Alzheimer's disease over long periods.