Ophthalmic administration of a 10-fold-lower dose of conventional nanoliposome formulations caused levels of intraocular pressure similar to those induced by marketed eye drops.

The purpose of this study was to compare the in vivo efficacy of several timolol (TM)-loaded liposomal formulations with current TM antiglaucoma treatment (aqueous 0.5% w/v eye drops). In this study, conventional liposomes (CL) and deformable liposomes, without (DL1) and with ethanol (DL2) were prepared and characterized. In addition, in vitro release and permeation studies, as well as in vivo lowering intraocular pressure (IOP) and biocompatibility studies were performed. It was found that the quali and quantitative lipid bilayer composition played a significant role in modifying the physical properties of vesicles. The deformability study and electronic microscopy images revealed that membrane elasticity of DL1 and DL2 was much higher than CL. However, in vitro permeation results showed that the flux and permeability coefficient were significantly higher in CL compared to DL. The IOP study revealed that TM-loaded CL showed the best pharmacological activity, in comparison to deformable vesicles. Compared to the eye drops, CL formulation could equally reduce the IOP but using a concentration 10-fold lower, whereas the effective time was significantly longer. In addition, the formulations showed no irritant effects after instillation on the ocular surface.

Deformability properties of timolol-loaded transfersomes based on the extrusion mechanism. Statistical optimization of the process.

The purpose of this work was to analyze the deformability properties of different timolol maleate (TM)-loaded transfersomes by extrusion. This was performed because elastic liposomes may contribute to the elevation of amount and rate of drug permeation through the corneal membrane. This paper describes the optimization of a transfersome formulation by use of Taguchi orthogonal experimental design and two different statistical analysis approaches were utilized. The amount of cholesterol (F1), the amount of edge-activator (F2), the distribution of the drug into the vesicle (F3), the addition of stearylamine (F4) and the type of edge-activator (F5) were selected as causal factors. The deformability index, the phosphorous recovery, the vesicle size, the polydispersity index, the zeta potential and percentage of drug entrapped were fixed as the dependent variables and these responses were evaluated for each formulation. Two different statistical analysis approaches were applied. The better statistical approach was determined by comparing their prediction errors, where regression analysis provided better optimized responses than marginal means. From the study, an optimized formulation of TM-loaded transfersomes was prepared and obtained for the proposed ophthalmic delivery for the treatment of open angle glaucoma. It was found that the lipid to surfactant ratio and type of surfactant are the main key factors for determining the flexibility of the bilayer of transfersomes. From in vitro permeation studies, we can conclude that TM-loaded transfersomes may enhance the corneal transmittance and improve the bioavailability of conventional TM delivery.

Surface functionalizing of a lipid nanosystem to promote brain targeting: step-by-step design and physico-chemical characterization.

The use of lipid nanosystems as drug delivery to the central nervous system may be advantageous over the current strategies. The aim of this study was to develop and characterize functionalized liposomes for treatment of brain diseases. The covalent method of coupling IgG to liposomes via the derivatized lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-[4-(p-maleimidophenyl)butyramide](MPB-PE) was investigated. Optimized coupling conditions are shown to result in the efficient conjugation of IgG to liposomes containing low concentrations of MPB-PE (3/1 SH:IgG). The qualitative analysis has shown that after the extrusion process, more homogeneous populations of vesicles have been obtained with a nanometric size suitable to be effective to further anchor the protein. Negative values of zeta potential demonstrate that they are stable systems. Lyophilization was used to maintain the stability of the formulation. These very interesting results encourage further investigations to formulate peptide- and protein-loaded immunoliposomes, making targeting of liposomes as an attractive approach for brain drug delivery.

Development and validation of a high performance chromatographic method for determining sumatriptan in niosomes.

In this paper, a novel, precise, specific, accurate and rapid reversed-phase high performance liquid chromatographic method was developed, optimized and validated for determining sumatriptan succinate in niosomes with the best chromatographic peak resolution, reduced run time and low cost of analysis. The formulation has been previously optimized in terms of composition and preparation technique to obtain a high drug encapsulation efficiency and adequate vesicle size distribution. This method showed the best resolution by using Spherisorb OSD2 C18 column (250 mm × 4.6 mm, 5 µm) using phosphate buffer (0.05 M):acetonitrile (80:20, v/v; pH adjusted to 6.0) as a mobile phase at a flow rate of 1 mL/min and wavelength of 214 nm. The main objective of this research was to demonstrate the robustness of the reversed-phase HPLC method development by applying the Taguchi robust methodology. The signal-to-noise ratio (S/N) was employed as a quality measurement. This tool permits to establish the influence of some selected factors (acetonitrile:phosphate ratio, pH buffer, oven temperature and flow rate) on two responses (peak areas and retention time). On the basis of the results obtained, we can conclude that this analytical method was robust for all the factors studies, as exception of the flow rate, where the higher quality was obtained for the fewer values (0.8 mL/min). Therefore, this parameter must be carefully controlled when this method was employed, to avoid any modification in the peak areas overall.

Insulin-loaded PLGA microparticles: flow focusing versus double emulsion/solvent evaporation.

CONTEXT: Oral administration of insulin is severely limited by very low bioavailability. Biocompatible polymeric nanocarriers have been investigated to overcome this problem. Flow focusing (FF) has revolutionized current engineering of poly(D,L-lactide-co-glycolide) (PLGA) based micromedicines. This technique has never been used to formulate insulin-loaded PLGA microparticles. OBJECTIVE: Investigation of the benefits rising from the synthesis of insulin-loaded PLGA microplatforms by FF, compared to double emulsion/solvent evaporation method. MATERIALS AND METHODS: Both synthesis methodologies were compared in terms of geometry, surface physicochemical properties and insulin vehiculization capabilities. The stability of the peptide during the formulation procedure was further analysed. RESULTS: FF permitted the preparation of insulin-loaded microcarriers with better geometry and physicochemical properties for the oral route, along with greater insulin loading capabilities and sustained insulin release kinetics. DISCUSSION AND CONCLUSION: Results have lead to the identification of the best formulation conditions for the engineering of insulin-loaded PLGA microparticles against diabetes.

Protein-loaded PLGA microparticles engineered by flow focusing: physicochemical characterization and protein detection by reversed-phase HPLC.

In the present study, a novel synthesis technique based on the flow focusing (FF) technology is investigated for the preparation of green fluorescent protein (GFP)-loaded poly(D,L-lactide-co-glycolide) (PLGA) microparticles. To our knowledge, this novel technique has never been applied to the formulation of proteins in polymeric systems. A simple, specific and rapid reversed-phase HPLC (RP-HPLC) method was validated for the determination of GFP in PLGA microparticles with the best chromatographic peak resolution, reduced run time and low cost of analysis. In order to achieve the finest GFP-loaded polymeric particles, experimental parameters mainly associated to the FF device were studied (liquid flow rate and pressure of the focusing air). Very high GFP encapsulation values (>90%) were obtained by this technique, and the electrokinetic characterization of these systems suggested that this protein was incorporated into the polymeric matrix. This study is intended to offer information on which to base the development of high molecular weight protein-loaded polymeric delivery systems prepared by FF.