Daniela Chirio

Preparation of solid lipid nanoparticles from W/O/W emulsions: Preliminary studies on insulin encapsulation

Abstract A method to produce solid lipid nanoparticles (SLN) from W/O/W multiple emulsions was developed applying the solvent-in-water emulsion-diffusion technique. Insulin was chosen as hydrophilic peptide drug to be dissolved in the acidic inner aqueous phase of multiple emulsions and to be consequently carried in SLN. Several partially water-miscible solvents with low toxicity were screened in order to optimize emulsions and SLN composition, after assessing that insulin did not undergo any chemical modification in the presence of the different solvents and under the production process conditions. SLN of spherical shape and with mean diameters in the 600–1200 nm range were obtained by simple water dilution of the W/O/W emulsion. Best results, in terms of SLN mean diameter and encapsulation efficiencies, were obtained using glyceryl monostearate as lipid matrix, butyl lactate as a solvent, and soy lecithin and Pluronic®F68 as surfactants. Encapsulation efficiencies up to 40% of the loaded amount were obtained, owing to the actual multiplicity of the system; the use of multiple emulsion-derived SLN can be considered a useful strategy to encapsulate a hydrophilic drug in a lipid matrix.

Solid lipid nanoparticles as vehicles of drugs to the brain: current state of the art.

Central nervous system disorders are already prevalent and steadily increasing among populations worldwide. However, most of the pharmaceuticals present on world markets are ineffective in treating cerebral diseases, because they cannot effectively cross the blood brain barrier (BBB). Solid lipid nanoparticles (SLN) are nanospheres made from biocompatible solid lipids, with unique advantages among drug carriers: they can be used as vehicles to cross the BBB. This review examines the main aspects surrounding brain delivery with SLN, and illustrates the principal mechanisms used to enhance brain uptake of the delivered drug.

Formulation of curcumin-loaded solid lipid nanoparticles produced by fatty acids coacervation technique

Curcumin (CU) loaded solid lipid nanoparticles (SLNs) of fatty acids (FA) were prepared with a coacervation technique based on FA precipitation from their sodium salt micelles in the presence of polymeric non-ionic surfactants. Myristic, palmitic, stearic, and behenic acids, and different polymers with various molecular weights and hydrolysis grades were employed as lipid matrixes and stabilisers, respectively. Generally, spherical-shaped nanoparticles with mean diameters below 500u2009nm were obtained, and using only middle-high hydrolysis, grade-polymer SLNs with diameters lower than 300u2009nm were produced. CU encapsulation efficiency was in the range 28–81% and highly influenced by both FA and polymer type. Chitosan hydrochloride was added to FA SLN formulations to produce bioadhesive, positively charged nanoparticles. A CU-chitosan complex formation could be hypothesised by DSC analysis, UV–vis spectra and chitosan surface tension determination. A preliminary study on HCT-116 colon cancer cells was developed to evaluate the influence of CU-loaded FA SLNs on cell viability.

Solid Lipid Nanoparticles for Potential Doxorubicin Delivery in Glioblastoma Treatment: Preliminary In Vitro Studies

The major obstacle to glioblastoma pharmacological therapy is the overcoming of the blood-brain barrier (BBB). In literature, several strategies have been proposed to overcome the BBB: in this experimental work, solid lipid nanoparticles (SLN), prepared according to fatty acid coacervation technique, are proposed as the vehicle for doxorubicin (Dox), to enhance its permeation through an artificial model of BBB. The in vitro cytotoxicity of Dox-loaded SLN has been measured on three different commercial and patient-derived glioma cell lines. Dox was entrapped within SLN thanks to hydrophobic ion pairing with negatively charged surfactants, used as counterions. Results indicate that Dox entrapped in SLN maintains its cytotoxic activity toward glioma cell lines; moreover, its permeation through hCMEC/D3 cell monolayer, assumed as a model of the BBB, was increased when the drug was entrapped in SLN. In conclusion, SLN proved to be a promising vehicle for the delivery of Dox to the brain in glioblastoma treatment.

MCM-41 as a useful vector for rutin topical formulations: Synthesis, characterization and testing

Rutin, the glycoside of quercetin, could be used in topical preparations because of its antioxidant and radical scavenging properties, but its employ in cosmetic and pharmaceutical products is limited by poor physico-chemical stability. These issues were addressed by preparing, characterizing and testing rutin inclusion complexes with MCM-41 mesoporous silica. The effect of surface functionalization with aminopropyl groups (NH₂-MCM-41) on the molecules properties was studied. The organic/inorganic interaction was confirmed by many techniques. In particular, the high inclusion of rutin in the pores of NH₂-MCM-41 was assessed by XRD, TGA, gas-volumetric analysis (BET), while FTIR spectroscopy allowed to analyse with great detail the molecular interaction with the inorganic surface. Rutin was stabilized against UV degradation, mostly by its inclusion in NH₂-MCM-41. Ex vivo studies showed a greater accumulation in porcine skin in the case of rutin complexed with NH₂-MCM-41. Not only antioxidant properties of rutin were maintained after immobilization but, with aminopropyl silica, the metal-chelating activity increased noticeably. The immobilization of rutin in aminopropyl silica resulted in better performance in terms of activity and photostability, suggesting the importance of functionalization in stabilizing organic molecules within silica pores.

Development of O/W nanoemulsions for ophthalmic administration of timolol.

After an initial screening of ingredients and production methods, nanoemulsions for ocular administration of timolol containing the drug as maleate (TM) or as ion-pair with AOT (TM/AOT) were prepared. The physico-chemical characterization of nanoemulsions, regarding mean diameter, pH, zeta potential, osmolarity, viscosity and surface tension, underlined their feasibility to be instilled into the eyes. Single components and emulsions were tested ex vivo on rabbit corneas to evaluate corneal irritation, that was measured according to opacity test. A marked decrease in corneal opacity was observed using the drug formulated in nanoemulsions rather than in aqueous solutions. Drug permeation and accumulation studies were performed on excised rabbit corneas. An increase in drug permeation through and accumulation into the corneas were observed using TM-AOT compared to TM due to an increase of lipophilicity of the drug as ion-pair. The introduction of chitosan (a positive charged mucoadhesive polymer) into emulsions allowed to increase TM permeation probably due to the interaction of chitosan with corneal epithelial cells.

Bevacizumab loaded solid lipid nanoparticles prepared by the coacervation technique: preliminary in vitro studies.

Glioblastoma, the most common primary brain tumor in adults, has an inauspicious prognosis, given that overcoming the blood-brain barrier is the major obstacle to the pharmacological treatment of brain tumors. As neoangiogenesis plays a key role in glioblastoma growth, the US Food and Drug Administration approved bevacizumab (BVZ), an antivascular endothelial growth factor antibody for the treatment of recurrent glioblastoma in patients whose the initial therapy has failed. In this experimental work, BVZ was entrapped in solid lipid nanoparticles (SLNs) prepared by the fatty-acid coacervation technique, thanks to the formation of a hydrophobic ion pair. BVZ activity, which was evaluated by means of four different in vitro tests on HUVEC cells, increased by 100- to 200-fold when delivered in SLNs. Moreover, SLNs can enhance the permeation of fluorescently labelled BVZ through an hCMEC/D3 cell monolayer-an in vitro model of the blood brain barrier. These results are promising, even if further in vivo studies are required to evaluate the effective potential of BVZ-loaded SLNs in glioblastoma treatment.

Cisplatin-loaded SLN produced by coacervation technique

Coacervation technique, a solvent-free, feasible and versatile method, based on a phase transformation from soap micellar solution into fatty acid solid particles by acid addition, was used to prepare cisplatin loaded solid lipid nanoparticles (SLN) of stearic acid. Different polymers were tested to stabilise SLN suspensions. Solubilisation of cisplatin, a hydrophilic antitumor agent, within sodium stearate micelles was possible by the formation of a hydrophobic ion-pair with sodium dioctylsulfosuccinate. Several SLN were produced, whose particle size were in the 275–525 nm range. Cisplatin encapsulation efficiency up to 90 % was obtained, depending on both stearic acid concentration and stabilisers type and concentration. The in vitro cisplatin release showed a burst effect of about 10–20 %, corresponding to the non-encapsulated drug, and then a complete drug release was reached after 24 h.

Deformable Liposomes as Topical Formulations Containing α‐Tocopherol

Several deformable liposomes were formulated using hydrogenated soya lecithin and sodium cholate, polisorbate 80, dipotassium glycyrrhizinate, or saccharose monopalmitate. The lipid:surfactant w/w ratio necessary to obtain elastic vesicles depended on the O/W surfactant and ranged from 4∶1 to 20∶1. The liposomes obtained were able to entrap α‐tocopherol and tocopheryl acetate up to 0.17% w/w. Elastic liposomes, whose deformability was confirmed by filtration through microporous filters and differential scanning calorimetry measurements, when non‐occlusively applied on pig ear skin, determined negligible skin fluxes of α‐tocopherol, while skin deposition significantly increased compared with reference solutions or normal liposomes. Moreover, the entrapment of the vitamin either in elastic or in normal liposomes increased its photo‐stability under UVB irradiation.

Techniques for the Preparation of Solid Lipid Nano and Microparticles

General ingredients include solid lipid(s), surfactant(s) and water. The term lipid is used here in a broad sense and includes triglycerides (e.g. tristearin), partial glycerides, fatty acids (e.g. stearic acid), steroids (e.g. cholesterol) and waxes (e.g. cetyl palmitate). All classes of surfac‐ tants (with respect to charge and molecular weight) have been used to stabilize the lipid dispersion [2].