Rita Cortesi

Production of lipospheres as carriers for bioactive compounds

Aim of the present paper was to investigate the influence of preparation parameters on the production of lipospheres (LS) for drug delivery. LS composed of triglycerides and monoglycerides were alternatively produced by melt dispersion technique, solvent evaporation or w/o/w double emulsion method. The influence of preparation parameters, such as (a) type and amount of lipids, (b) presence and concentration of surfactants, (c) stirring speed and (d) type of stirrer was studied. In the case of LS prepared by melt dispersion, the use of a lipid composition of cetyl alcohol/cholesterol (2:1, w/w), a 5% (w/w) gelatin solution (50 bloom grades) and 1000 rpm stirring speed resulted in the production of spherical particles, with high percentage of recovery (82%, w/w) a mean diameter of 80 microm and a narrow size distribution. In the case of LS prepared by solvent evaporation, the best results in terms of LS morphology, recovery and size distribution were obtained by the use of a lipid composition of tristearin/monostearate (66:34, w/w), a 1% (w/w) PVA solution, a 750 rpm stirring speed and a 55 mm three-blade turbine rotor. The solvent evaporation method resulted in the production of LS characterised by a smaller size (20 microm mean diameter) but poor mechanical properties with respect to particles with the same composition obtained by the melt dispersion technique (170 microm mean diameter). The use of a combination of lipids and a methacrylic polymer (Eudragit RS 100) overcame this problem, resulting in the production of spherical particles, with a narrower size distribution and good mechanical properties. Two lipophilic drugs, such as retinyl acetate and progesterone, and one hydrophilic drug, sodium cromoglycate (SCG), were encapsulated in LS as model compounds. Lypophilic drugs displayed satisfactory encapsulation efficiencies (over 70% w/w), while SCG was very scarcely encapsulated (about 2% w/w). To solve this drawback, the use of a w/o/w double emulsion strategy was proposed, enabling to increase the encapsulation of SCG up to 50% w/w. Finally, in vitro drug release studies were performed, showing that all drugs were released in a control manner. In particular. the retinyl acetate release efficacy within the first 8 h was 27% of the total amount of the drug, while in the same period, the amount of progesterone released was 63%. With regard to SCG containing LS, the release of the drug was largely influenced by the type of stabiliser of the primary emulsion, in any case the SCG release reached the 100% of the total amount of drug after 5 h from the beginning of the experiment.

Gelatin microspheres: influence of preparation parameters and thermal treatment on chemico-physical and biopharmaceutical properties

The aim of this paper was to investigate the influence of preparation parameters on gelatin microspheres production, chemico-physical characteristics and drug encapsulation. In particular, we focussed our attention on the manufacturing parameters such as amount of polymer, stirring speed, presence and concentration of surfactants. As model drugs, TAPP-Br, clonidine hydrochloride and bromocriptine mesylate were chosen in order to compare their encapsulation and release characteristics with microspheres. In the second part of this work, a study of the influence of thermal treatment on the microspheres is reported, performed with the aim to possibly modify gelatin dissolution and drug release. In particular, the effect of this treatment was evaluated on microsphere characteristics such as swelling, porosity and dissolution, and finally on the release profiles of the encapsulated drugs.

Formulation study for the antitumor drug camptothecin: liposomes, micellar solutions and a microemulsion

In the present paper we describe the production and characterization of specialized delivery systems for camptothecin, namely liposomes, micellar solutions and microemulsion. For instance, liposomes were prepared by reverse phase evaporation technique followed by extrusion through polycarbonate filters. Liposomes were characterized in term of dimensions, morphology and encapsulation efficacy. All the formulations were designed firstly to increase the solubility of camptothecin in aqueous environment and secondly to reduce the toxicity problems related to the administration of this drug. The analysis of their in vitro antiproliferative activity on cultured human leukemic K562 cells demonstrated that liposomes, micellar solutions and microemulsion containing camptothecin exert similar or slightly enhanced effect as compared to that shown by the free drug. Based on these results, the specialized delivery systems here proposed typify an interesting starting point for a future use in experimental therapy.

Effect of cationic liposome composition on in vitro cytotoxicity and protective effect on carried DNA

Positively charged liposomes were prepared by using three different cationic surfactants, namely cetyl-trimethyl-ammonium bromide (CTAB), didodecyl-dimethyl-ammonium bromide (DDAB12) and dioctadecyl-dimethyl-ammonium bromide (DDAB18). A study of the parameters influencing the in vitro toxicity of cationic liposomes on cultured cell lines was performed, demonstrating the lower cytotoxicity of DDAB18-containing liposomes. In addition, the stability of λDNA complexed to cationic liposomes after exposure to serum exo- and endonucleases was evaluated. Our results indicated that DDAB12 and DDAB18 liposomes are able to efficiently protect DNA from degradation, thus representing a potential approach to deliver nucleic acid in vivo.

Lipid-based supramolecular systems for topical application: A preformulatory study

This article describes the production and characterization of monoglyceride-based supramolecular systems by a simple processing technique, avoiding time-consuming procedures, high energy input, and the use of organic solvents. A preformulatory study was performed to study the influence of the experimental parameters on the production of monoglyceride-based disperse systems. In particular the effects of (1) stirring speed, (2) type and concentration of monoglyceride mixture, and (3) type and concentration of surfactant were investigated on the recovery, fraction of larger particles, mean diameter, and shape of smaller particles (so called nanosomes). Dispersions were first characterized by optical microscopy and freeze-fracture electron microscopy. The mean diameter of standard nanosomes, analyzed by photon correlation spectroscopy (PCS) after elimination of larger particles by filtration, was 193.5 nm. Cryotransmission electron microscopy studies, conducted in order to investigate the structure of dispersions, showed the coexistence of vesicles and particles characterized by a cubic organization. X-ray diffraction data revealed the coexistence of 2 different cubic phases, the first being a bicontinuous cubic phase of spatial symmetry Im3m (Q229) and the second belonging to the Pn3m spatial symmetry. A study on the stability of monoglyceride-based dispersions based on macroscopical analysis of organoleptic properties and dimensional analysis by time was performed after elimination of larger particles by filtration. Organoleptic and morphological features do not change by time, appearing free from phase-separation phenomena for almost 1 year from production. PCS studies showed that nanosomes undergo an initial increase in mean diameter within the first month following production; afterwards they generally maintain their dimensions for the next 4 months.

Production of Eudragit Microparticles by Spray-Drying Technique: Influence of Experimental Parameters on Morphological and Dimensional Characteristics

The aim of this study was to evaluate the influence of operating parameters on the characteristics of methacrylate microparticles prepared by spray-drying technique. Eudragit microparticles were prepared by a spray-drying method. The influence of different experimental parameters (i.e., solvent, feed rate, air flow rate, air-drying temperature, and aspiration flow rate) on microparticle morphology, size distribution, and recovery was studied. In addition, different Eudragit types and Eudragit RS concentrations were employed. Optical and electron microscopy were employed to analyze microparticle morphology and dimensional distribution. Finally, prednisolone as model drug was encapsulated in Eudragit RS microparticles. Low feed rate values yielded the best results in terms of microparticle morphology. Changes in nebulizing air flow did not result in a corresponding effect on microparticle characteristics. An increase of air-drying temperature resulted in a reduction of microparticle dimension and recovery. A low flow of drying air was preferable because this resulted in microparticles with an optimal morphology. The polymer concentration affected both morphology and dimensions of microparticles. The encapsulation of prednisolone led to good incorporation efficiencies without altering percentage of recovery, morphology, and mean dimension of the microparticles. The selection of appropriate parameters yielded spray-dried Eudragit RS microparticles characterized by good morphology and narrow dimensional distribution.

Effects of phospholipid based formulations on in vitro and in vivo percutaneous absorption of methyl nicotinate

In this paper we evaluate the influence of phospholipid based formulations (PBFs) on skin absorption. In particular we describe the production and characterization of different PBFs, namely liposomes and w/o microemulsion gels, and their influence on in vitro and in vivo absorption of methyl nicotinate (MN) used as model compound. In order to compare the influence of various vehicles on skin absorption, Franz cell and MN induced erythema were used as in vitro and in vivo experimental models respectively. The formulations tested were: (a) unilamellar liposomes consisting of soybean lecithin/ cholesterol (9:1 w/w) suspended in water or incorporated into hydrophilic gels (Carbomer and carboxymethyl cellulose based gels) and (b) soybean lecithin based gels. The results indicate that vehicles containing phospholipids in liposomal form provided enhanced in vivo MN skin permeation compared to the corresponding vehicles without phospholipids. Lecithin gel showed a different behaviour characterized by a short and intense persistence of MN induced erythema.

Dextran cross-linked gelatin microspheres as a drug delivery system

This paper describes the use of oxidized dextran as a cross-linker for the preparation of gelatin microspheres. Microspheres were obtained by a thermal gelation method and their dissolution kinetic was examined. In order to find evidence of sugar mediated cross-linking, swelling tests and gelatin microspheres dissolution experiments were performed. The obtained results indicated that oxidized dextran can form a cross-linked gelatin network which can reduce the dissolution of gelatin. More interestingly, gelatin microspheres treated by both native and oxidized dextran slow down, even if to a different extent, the release of the antitumor drug TAPP-Br used as a model compound. Taken together, our results suggest that oxidized dextran could be an interesting means to cross-link gelatin microspheres allowing the use of this delivery formulation for controlled release of drugs.

Preparation and characterization of starch/cyclodextrin bioadhesive microspheres as platform for nasal administration of Gabexate Mesylate (Foy®) in allergic rhinitis treatment

Bioadhesive and biodegradable microspheres were obtained by chemical cross-linking with epichlorohydrin of an alkaline solution of a mixture of starch and alpha-, beta-, or gamma-cyclodextrin (CyD). Microspheres were characterized by scanning electron microscopy, swelling degree, and water retention. The percentage of the effective CyD in microspheres was estimated by measuring the amount of iodine and typical organic compounds (TOCs) retained in the hydrophobic cavity of CyD. Gabexate Mesylate (trade name Foy); GM), an antiallergic drug, was included in microspheres by soaking in an aqueous solution containing the drug, followed by solvent evaporation or lyophilization. UV, IR, and DSC data indicated that despite the fact that GM is a hydrophilic drug, its hydrophobic moiety close to the benzene ring is able to penetrate the CyD cavity and to form stable inclusion complexes. Values of the association equilibrium constant for GM binding to CyD, obtained by UV differential spectroscopy, indicated that the affinity of the drug for alpha- and gamma-CyD is higher than that for beta-CyD. In vitro, GM was gradually released during 1h. Even if the release rate of the drug is relatively fast, the microspheres might actually provide the best platform since the material adheres to the nasal mucosa which was proved by adhesion tests. The GM integrity was checked by comparing its anti-trypsin activity before and after release.

Liposomes as carriers for DNA–PNA hybrids

Peptide nucleic acids (PNAs) are DNA mimics composed of N-(2-aminoethyl)glycine units. This structure gives to PNAs (a) resistance to DNases and proteinases, (b) capacity to hybridize with high affinity to complementary sequences of single-stranded RNA and DNA, and (c) capacity to form highly stable (PNA)(2)-RNA triplexes with RNA targets. Furthermore, DNA-PNA hybrid molecules are capable to reversibly interact with DNA-binding proteins, being therefore of interest for studies on regulation of gene expression by the decoy approach. The major conclusion of this paper is that cationic liposomes are able to efficiently complexate DNA-PNA hybrid molecules and mediate their binding to target cells. Our results are of some interest, since, unlike commonly used nucleic acids analogs, PNA oligomers are not taken up spontaneously into the cells. In addition, they are not suitable for an efficient delivery with commonly used liposomal formulations. Transfection of PNA-DNA hybrid molecules to in vitro cultured cells could be of great interest to determine the applications of these new reagents to experimental alteration of gene expression.