Antonio Leonardi

Influence of different surfactants on the technological properties and in vivo ocular tolerability of lipid nanoparticles

Addition of one or more surfactant agents is often necessary for the production of nanostructured lipid and polymeric systems. The removal of residual surfactants is a required step for technological and toxicological reasons, especially for peculiar applications, such as the ophthalmic field. This study was planned to assess the technological properties of some surfactants, commonly used for the production of lipid nanoparticles, as well as their ocular safety profile. Stable and small-size solid lipid nanoparticles were obtained using Dynasan(®) 114 as the lipid matrix and all the tested surfactants. However, from a toxicological point of view, the nanocarriers produced using Kolliphor(®) P188 were the most valuable, showing no irritant effect on the ocular surface up to the highest tested surfactant concentration (0.4%, w/v). The SLN produced using Cremophor(®) A25 and Lipoid(®) S100 were tolerated up to a surfactant concentration of 0.2% by weight, while for Tween(®) 80 and Kolliphor(®) HS 15 a maximum concentration of 0.05% can be considered totally not-irritant.

Cationic solid lipid nanoparticles enhance ocular hypotensive effect of melatonin in rabbit.

The study was aimed at evaluating whether the ocular hypotensive effect of melatonin (MEL) was enhanced by its encapsulation in cationic solid lipid nanoparticles (cSLN), as well as at determining the tolerability of these formulations on the ocular surface. MEL was loaded in cSLN that had already been shown to be suitable for ophthalmic use. The formulations were prepared using Softisan(®) 100 as the main lipid matrix, with the presence of either stearic (SA) or palmitic acid (PA) as lipid modifiers. A fixed positive charge was provided by the addition of a cationic lipid (didecyldimethylammonium bromide). The ocular hypotensive effect was evaluated by measuring the intraocular pressure (IOP) during 24h in albino rabbits. MEL elicited a significant (p<0.01) IOP reduction in rabbit eye. All the formulations tested in vivo demonstrated a good tolerability. The nanocarrier containing SA was the most effective in terms of IOP reduction (maximum IOP reduction: -7 mmHg), and its effect lasted approximately 24h. The experimental data indicate that the new formulations based on cSLN loaded with MEL represent a potent anti-glaucoma treatment with a safe profile, warranting further clinical evaluation of the proposed nanotechnological strategy.

Pharmaceutical and biomedical applications of lipid-based nanocarriers.

Increasing attention is being given to lipid nanocarriers (LNs) as drug delivery systems, due to the advantages offered of a higher biocompatibility and lower toxicity compared with polymeric nanoparticles. Many administration routes are being investigated for LNs, including topical, oral and parenteral ones. LNs are also proposed for specific applications such as cancer treatment, gene therapy, diagnosis and medical devices production. However, the high number of published research articles does not match an equal amount of patents. A recent Review of ours, published in Pharmaceutical Patent Analyst, reported the patents proposing novel methods for the production of LNs. This review work discusses recent patents, filed in 2007-2013 and dealing with the industrial applications of lipid-based nanocarriers for the vectorization of therapeutically relevant molecules, as well as biotech products such as proteins, gene material and vaccines, in the pharmaceutical, diagnostic and biomedical areas.

Lipid-based nanocarriers for drug delivery and targeting: a patent survey of methods of production and characterization

Among the colloidal vectors proposed for the controlled delivery and targeting of drugs and other biologically active compounds, lipid-based nanocarriers are acquiring an increasing role due to a number of peculiar technological and physical features. Solid lipid nanoparticles, lipid nanocapsules, nanostructured lipid carriers, and drug-lipid conjugates are all examples of how it can be possible to combine the properties of the more acknowledged liposomal systems, such as biocompatibility and biodegradability, with the stability and compositional flexibility, distinctive of polymeric nanosystems. This article introduces recent patents, filed in years 2007-2013, that deal with novel or amended methods of production of the various types of lipid-based nanocarriers. Although a significant gap still remains between basic research and patenting activity in this field, many of the proposed methods can attain an industrial value. Furthermore, the critical analysis of these patents further supports the position that a general revision of patenting systems at an international level would be necessary for nanosized pharmaceutical systems.

Antioxidant activity of idebenone-loaded neutral and cationic solid–lipid nanoparticles

Abstract Idebenone (IDE) is a lipophilic benzoquinone electron carrier synthetic analogue of coenzyme Q10, which behaves as an antioxidant and free radical scavenging molecule. Recently, the therapeutic application of IDE in Leber’s hereditary optic neuropathy has been discussed. This work was aimed at evaluating the encapsulation of IDE in solid–lipid nanoparticles (SLN). In particular, we tested the possibility of adapting the quasi-emulsion solvent diffusion technique, already proposed to produce polymeric nanoparticles, to prepare positively charged SLN with different compositions. Such a charge, due to the addition of a cationic lipid, would facilitate the interaction with the negatively charged eye surface epithelium, with a consequent longer pre-corneal residence time of the colloidal systems. In a preliminary evaluation of the produced IDE-loaded SLN, the antioxidant activity of the drug was demonstrated using an oxygen radical absorbance capacity assay. Encapsulation of the drug in the nanocarrier systems seems able to protect IDE from degradation and prolong its antioxidant potential.

Catalytic Activity of Silicon Nanowires Decorated with Gold and Copper Nanoparticles Deposited by Pulsed Laser Ablation

Silicon nanowires (SiNWs) decorated by pulsed laser ablation with gold or copper nanoparticles (labeled as AuNPs@SiNWs and CuNPs@SiNWs) were investigated for their catalytic properties. Results demonstrated high catalytic performances in the Caryl–N couplings and subsequent carbonylations for gold and copper catalysts, respectively, that have no precedents in the literature. The excellent activity, attested by the very high turn over number (TON) values, was due both to the uniform coverage along the NW length and to the absence of the chemical shell surrounding the metal nanoparticles (MeNPs). A high recyclability was also observed and can be ascribed to the strong covalent interaction at the Me–Si interface by virtue of metal “silicides” formation.

Optimization and Validation of a New Method for the Production of Lipid Nanoparticles for Ophthalmic Application

Within a wider research project aimed at the pre-industrial development of nanotechnology platforms for the treatment of eye diseases, this work exploited the possibility of obtaining solid lipid nanocarriers (SLN) using ingredients and operating conditions that could be compatible with the technological requirements of medical formulations used for ophthalmic therapies and, above all, capable of an easy industrial scale-up. In particular, we tested the possibility of adapting a production method known as Quasi-emulsion Solvent Diffusion (QESD), which already shows a number of operational advantages, such as use of low temperatures and reduced concentrations of surfactants, also to very small production volumes, compatible with expensive and/or poorly available drugs. Cationic SLN (cSLN) were produced using a commercial lipid matrix (Softisan® S100), loaded with a lipophilic probe compound. These cationic carriers could be advantageous in ensuring a prolonged retention onto the negatively charged mucous surface of the cornea. Depending on their composition, cSLN systems with a mean size around 170-250 nm, a good size distribution profile, and a net positive charge (+30/+50 mV) were produced by the QESD technique. Only highly biocompatible, ICH-class 3 solvents, such as ethanol and acetone, were used. Most nanocarriers showed a good physical stability upon storage and could be produced respecting some formulation requirements, such as pH close to neutrality and an osmolarity compatible with the eye surface.

Preparation and Microbiological Evaluation of Amphiphilic Kanamycin-Lipoamino Acid Ion-Pairs

Amphiphilic ion-pairs of kanamycin (KAN) were prepared by evaporation of a water-ethanol co-solution of KAN base and a lipoamino acid bearing a 12-carbon atoms alkyl side chain (LAA12), at different molar ratios. Infrared spectroscopy confirmed the structure of ion-pairs, while differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) studies supported the formation of new saline species with a different crystalline structure than the starting components. The solubility pattern shown in a range of both aqueous and organic solvents confirmed that the ion-pairs possess an amphiphilic character. The LAA12 counter-ion showed not to improve the antibacterial activity of KAN, suggesting that such chemical strategy is not able to favor the penetration of this drug inside the bacteria cells. Nevertheless, a slight improving, i.e., a one-fold dilution, was observed in E. coli. The present study can also serve as the basis for a further evaluation of LAA ion-pairing of antibiotics, as a means to improve the loading of hydrophilic drugs into lipid-based nanocarriers.

A Method for Efficient Loading of Ciprofloxacin Hydrochloride in Cationic Solid Lipid Nanoparticles: Formulation and Microbiological Evaluation

The aim of the study was the production of solid lipid nanoparticles (SLN) loaded with ciprofloxacin (CIP) through two different production techniques, quasi-emulsion solvent diffusion (QESD) and solvent injection (SI). In order to efficaciously entrap the commercial salt form (hydrochloride) of the antibiotic in these lipid systems, a conversion of CIP hydrochloride to the free base was realized in situ, through the addition of triethylamine. To ensure physical stability to the carriers over time and ameliorate the interaction with bacterial cell membranes, positively charged SLN were produced by addition of the cationic lipid didecyldimethylammonium bromide (DDAB). Homogeneous SLN populations with a mean particle sizes of 250–350 nm were produced by both methods; drug encapsulation was over 85% for most samples. The SLN were physically stable for up to nine months both at 4 °C and 25 °C, although the former condition appears more suitable to guarantee the maintenance of the initial particle size distribution. As expected, CIP encapsulation efficiency underwent a slight reduction after nine months of storage, although the initial high drug content values would ensure a residual concentration of the antibiotic in the SLN still appropriate to exert an acceptable antibacterial activity. Selected SLN formulations were subjected to an in vitro microbiological assay against different bacterial strains, to verify the effect of nanoencapsulation on the cell growth inhibitory activity of CIP. In general, CIP-SLN produced without DDAB showed MIC values for CIP comparable to those of the free drug. Conversely, addition of increasing percentages of the cationic lipid, reflected by a progressive increase of the positive value of the Zeta potential, showed a variety of MIC values against the various bacterial strains, but with values 2–4 order of dilution lower than free CIP. An hypothesis of the effect of the cationic lipid upon the increased antibacterial activity of CIP in the nanocarriers is also formulated.

Characterization of micellar systems produced by new amphiphilic conjugates of poly(ethylene glycol).

Abstract This study proposes polymeric micelles produced using new amphiphilic conjugates between amino- or carboxy-mPEG2000 and three different α-lipoamino acids (PEG-LAA). The characterization of these colloidal systems showed CMC values, in the order of 10−5 M, that are interesting in the view of an in vivo administration. The PEG-LAA micelles also showed a good stability at 37 °C and upon dilution in aqueous media. Using a colored probe as a model lipophilic compound, the loading efficiency and in vitro release profile were also outlined.