Neuroprotective effect of melatonin loaded in ethylcellulose nanoparticles applied topically in a retinal degeneration model in rabbits.

We are reporting for the first time the synthesis and application of an innovative nanometric system for the controlled topic release of melatonin in the retina. The ethylcellulose nanocapsules were characterized by diverse physicochemical techniques (scanning electron microscopy, zeta potential, hydrodynamic diameters) and an in vitro release study was done. A complete ex vivo and in vivo trans-corneal permeation and an irritation study were carried out with the new formulations in albino rabbits, to which a retinal degenerative model was induced. The results obtained demonstrate that the in vitro release of melatonin (1 mg/mL and 2 mg/mL) transported by nanocapsules is slower when compared to a solution of melatonin. Greater penetration of melatonin through the cornea was demonstrated by ex vivo and in vivo tests. This can be attributable to an enhanced neuroprotective effect of melatonin on retinal ganglion cells when it is included in ethylcellulose nanocapsules compared to a solution of melatonin. These outstanding findings add promising new perspectives to current knowledge about administrations using nano-technological tools in the treatment of neurodegenerative diseases at the ocular level.

Self-Assembling Elastin-Like Hydrogels for Timolol Delivery: Development of an Ophthalmic Formulation Against Glaucoma.

This work focuses on improving the effectiveness of current therapies against glaucoma by incorporating self-assembled polymers into the ophthalmic formulation. To that end, we first studied the influence of the dispersing medium on the mechanical performance of self-assembling elastin-like (EL) and silk-elastin-like (SEL) hydrogels by conducting rheological tests. These polymers were subsequently incorporated into the antiglaucoma formulation, which contains timolol maleate (TM) as active ingredient, and in vivo tests, namely adhesion tests and intraocular pressure measurements (IOP), were performed in New Zealand rabbits. An enhanced reduction in IOP due to the presence of the polymers was observed. Moreover, differences in the effectiveness between both EL- and SEL-hydrogels, which can be explained on the basis of the different rheological properties displayed by these two systems, were also encountered. The results point to the potential of this system as a basis for the development of an ophthalmic formulation against glaucoma.

New RP-HPLC method for the simultaneous determination of process yield and percentage of encapsulation of Gallein in albumin nanoparticles.

A study was performed for the development and validation of a method of High Performance Liquid Chromatography (HPLC) for the identification and simultaneous quantification of Gallein and Human Serum Albumin (HSA). In addition, this work presents the development and physicochemical characterization of this new pharmaceutical formulation of HSA nanoparticles loaded with Gallein for potential use in the treatment of Alzheimer's disease. The method was developed with the purpose of determining the performance of the synthesis process of nanoparticles and the efficiency of encapsulation of the drug in the nanosystem. The HPLC mobile phase consisted of ACN:H2O:TEA:H3PO4 (50:49.8:0.1:0.1 v/v/v) pumped at a flow rate of 0.8 mL/min, isocratic mode, and the measurement were carried out at 220 nm. Chromatographic runs were performed on a C18 column (150 × 4.60 mm; 5 µm size particles). The HPLC-method was validated following the International Conference on Harmonisation (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human Use guidelines and was used to simultaneously quantify the two components of the nanoformulation. Thus, the values obtained through the validated method were 43 % for drug encapsulation efficiency (% EE) and the synthesis performance (% yield) was 96 %. Moreover, the nanoformulation was characterized by DLS, the results showed that the average particle size was 217 nm, with a PDI of (0.085 ± 0.005) and a potential Z of -29.7 mV. Therefore, the developed method has proven useful in providing accurate simultaneous measurements of HSA and Gallein from albumin nanoparticles. It is advantageous since it is able to reduce the time and facilitate the determination of Gallein encapsulation efficiency and yield of albumin nanoparticles.

Interaction between a cationic polymethacrylate (Eudragit E100) and anionic drugs.

The interaction between a cationic polymethacrylate (Eudragit E, EU) and a set of 7 drugs having acid groups (AH) was studied. Two series of complexes were prepared (EU-AH50 and EU-AH50Cl50), in both 50% of the basic groups of EU were neutralized with AH but in the second, the remaining groups were further neutralized with HCl. These products were stable solid ionic complexes that were characterized through infrared spectroscopy and X-ray power diffraction. All EU-AH50Cl50 at 5-10mg/ml produced clear optically isotropic aqueous dispersions. This result was in line with the increase of the apparent solubility of the low solubility AH assayed. The species distribution, as determined on the complex of diclofenac, showed a degree of counterion condensation as high as 97.9%. The reversibility of the counterion condensation, as well as the affinity between EU and AH, was evaluated through the proton withdrawing effect produced by the ionic exchange generated by titration with NaCl. Besides, drug delivery in bicompartimental Franz cells towards water as receptor medium was very slow. However, it was increased as water was replaced by NaCl solution that upon diffusion generates ionic exchange. Therefore, the EU-AH system behaves as a reservoir of drug able to deliver it in simulated biological fluid.

Novel Polymeric Nanoparticles Intended for Ophthalmic Administration of Acetazolamide.

Glaucoma is characterized by increased intraocular pressure (IOP) that results in blindness if it remains untreated. Acetazolamide (AZM) is a carbonic anhydrase inhibitor, mainly used to reduce IOP in the treatment of glaucoma. However, the potential of topical treatment is limited, due to its low permeability across the ocular epithelium. An alternative to overcome this limitation is the incorporation of AZM in nanoparticulate systems, such as polymeric nanocapsules (NCs). In this way, the aim of this work was to prepare and characterize NC formulations containing AZM, using ethylcellulose (EC) and Eudragit(®) RS100 (EUD) as encapsulating polymers. The formulations showed high encapsulation efficiency. Particle size measurements showed that NCs are in the nanometric range. Comparing both groups of formulations, the NCEC proved to be smaller than those prepared with EUD. The formulations prepared with EC showed negative zeta potentials, while NCs of EUD were positively charged. For both groups of formulations, no more than 30% of drug was released in 120 min. Ex vivo and in vivo studies evidenced that the NCEC formulations were the most efficient, because an increased amount of permeated drug was observed, along with a greater IOP decrease and longer duration of the effect in normotensive rabbits.

Improvement of acetazolamide ocular permeation using ascorbyl laurate nanostructures as drug delivery system.

PURPOSE: To evaluate the performance of 6-O-Lauryl-l-ascorbic acid nanostructures (coagels) as vehicles for acetazolamide (AZM) in ophthalmic administration by in vitro and in vivo experimental tests. METHODS: The systems of coagel + AZM were evaluated in terms of their in vitro release (dialysis membrane), permeability (isolated cornea), pharmacological effectiveness [intraocular pressure (IOP)-reduction in normotensive rabbits], and potential irritant effects. RESULTS: The results concerning AZM permeation were better when vehiculized in coagels compared with ringer solution, which was evident from the AZM steady-state flux and P(app) values (J=1.43 µg/min and P(app)=3.04 cm.s(1)). As a consequence of this increase in permeation, the coagel-AZMs were more effective in lowering the IOP, according to the results obtained from the in vivo assays. Coagels loaded with 0.4% (W/W) of AZM showed a higher hypotensive effect in rabbits compared with the commercial formulation AZOPT(®) (brinzolamide 1%), mainly due to the prolonged effect of the former. In all cases, the intensity of irritation was time dependent. The sodium lauryl sulphate solution (2%) used as a positive control produced serious injury 30 min postadministration. This effect caused irritation, which decreased slowly and even at 180 min, the discomfort was still considerable. However, in the case of coagels, a mild-to-moderate effect was observed. CONCLUSIONS: The incorporation of AZM in coagels seems to improve the ocular bioavailability of this drug. Coagel-AZM 0.4% showed a higher hypotensive effect, with a mild-to-moderate irritant effect. These systems could be administrated in human beings, although more detailed studies still need to be carried out.

Interaction between Eudragit® E100 and anionic drugs: addition of anionic polyelectrolytes and their influence on drug release performance.

In this work, we report results concerning the study of solid complexes compounded by a cationic polymethacrylate (Eudragit® E100, Eu) and mesalazine (M) (Eu-M(x) complex). The influence of an anionic polyacrylic acid polymer (carbomer, C) on dissolution behavior of M from the complex was evaluated (Eu-M(x) C(y) complex). The dissolution profiles and solvent front movements of solid matrices in different media (water, buffer pH 7.4, 0.9% NaCl) were investigated and ionic interactions among Eu, M, and C were determined through Fourier transform infrared (FT-IR) spectroscopy. For Eu-M(x) complexes, the affinity between M and Eu modulated the delivery of free M in solution, with the dissolution media affecting the delivery rate mainly due to an ionic interchange process between M and anionic electrolytes (i.e., Cl(-)). FTIR spectroscopy allowed the ionic interaction between Eu and M to be verified. The addition of C (Eu-M(x) C(y) ) influenced the dissolution behavior of these matrices. As the amount of C was increased, the release mechanism changed from diffusion (Eu-M(50) ) or anomalous (Eu-M(100)) to zero order (Eu-M(x) C(50)). This variation in rate delivery was also affected by the dissolution media, as occurred with Eu-M(x) complexes. The formation of the gel layer during the dissolution process, as consequence of Eu-M(x) C(y) matrices hydration, was influenced by C amount and dissolution media.