Effect of protective colloids on the induction of polymorphic changes in indomethacin agglomerates after solvent evaporation from o/w emulsions

Busulfan loading into poly(alkyl cyanoacrylate) nanoparticles: Physico-chemistry and molecular modeling

The busulfan is an alkylating agent widely used for the treatment of haematological malignancies and nonmalignant disorders. For a long time, it has been available only in an oral form. This treatment leads to a wide variability in bioavailability and side effects such as the veino-occlusive disease. Thus, an intravenous formulation of busulfan-loaded nanoparticles may be considered as a major progress. This study deals with busulfan entrapment by nanoprecipitation into five different types of poly(alkyl cyanoacrylate) polymers. The polymers leading to the highest busulfan loading efficiencies were poly(isobutyl cyanoacrylate) (PIBCA) and poly(ethyl cyanoacrylate). Molecular modeling along with energy minimization process was employed to identify the nature of the interactions occurring between busulfan and PIBCA. Further, optimization studies enabled to obtain PIBCA nanoparticles displaying busulfan loading ratios equal to 5.9% (w/w) together with nanoparticle yields of 71% (w/w). Since busulfan is a highly reactive molecule, we performed (1)H-NMR spectroscopy experiments showing that chemical integrity of the drug was preserved after loading into nanoparticles. The in vitro release studies under sink conditions, in water, or in rat plasma showed a fast release in the first 10 min followed by a slower one over 6 h. This phenomenon could be explained by the semi-polar characteristics of busulfan.

Albumin-protamine-oligonucleotide nanoparticles as a new antisense delivery system. Part 1: physicochemical characterization

In this paper, a ternary system of albumin-protamine-oligonucleotide nanoparticles (AlPrO-NP) recently developed by Vogel et al. [V. Vogel, D. Lochmann, J. Weyermann, G. Mayer, C. Tziatzios, J.A. van den Broek, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which could serve as a potential drug delivery system for antisense oligonucleotides. Former studies of binary protamine-oligonucleotide nanoparticles showed two main disadvantages: (i) aggregation of the particles within a few minutes in the presence of salt; (ii) low intracellular dissociation between protamine and oligonucleotide, especially phosphorothioates. To overcome these problems, human serum albumin (HSA) as a non-toxic, biodegradable macromolecule was introduced as protective colloid. The assembly process of AlPrO-NP was investigated by small angle X-ray scattering (SAXS), fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS) measurements and scanning electron microscopy (SEM). 'Initial complexes' of HSA and protamine sulphate with a mean hydrodynamic diameter (dh) of about 10-14 nm were found. After adding oligonucleotides (unmodified, phosphorothioate DNA and small interfering RNA), nanoparticles (NPs) were assembled in water and in isotonic media with a dh in a range of 230-320 nm for most preparations. The chemical composition of the particles was investigated by high performance liquid chromatography and fluorescence spectrometry. The whole amount of oligonucleotides (30 microg) was entrapped into the particles at a 1:2 mass ratio (oligonucleotide/protamine). Approximately 7-10% (w/w) of the HSA was bound to the particles. The surface charge of the particles ranged from about +12 to -60 mV depending on the protamine concentration and the ionic conditions. The size and the molecular weight of the components, initial complexes and two model NP preparations were calculated from FCS data. These data verified the PCS, SEM and SAXS measurements.

In vitro degradation and dissolution behaviours of microspheres prepared by three low molecular weight polyesters

Three low-molecular weight polyesters, poly(L-lactic acid) (PLA), copoly(lactic acid/glycolic acid) (PLGA) and poly(delta-valerolactone) (PV), were used to prepare water-soluble sodium diclofenac-loaded microspheres by using the oil-in-oil (o/o) emulsification-solvent evaporation method. Their micromeritic and physicochemical properties, and degradation and dissolution behaviours were determined in vitro. The results indicate that high encapsulation efficiency and better monodispersity might be achieved by the o/o emulsification-solvent evaporation method, depending on the amount of drug loading used. The slower evaporation of organic solvent from the system during microencapsulation seemed to modify the crystallinity of drug and polyester in the microspheres, determined by powder x-ray diffractometry and differential scanning calorimetry. The in vitro degradation rate of all the microspheres in pH7.4 phosphate buffer solution showed first-order kinetics and ranked in the order of PLGA > PLA > PV microspheres. Furthermore, the first-order release rate was also found in all the microspheres after an initial drug burst and ranked in the order of PLGA> PLA > PV microspheres, too. The relationship between degradation and dissolution behaviours of these microspheres is discussed.