Optimising the controlled release of dexamethasone from a new generation of PLGA-based microspheres intended for intravitreal administration

Successful therapy for chronic diseases affecting the posterior segment of the eye requires sustained drug concentrations at the site of action for extended periods of time. To achieve this, it is necessary to use high systemic doses or frequent intraocular injections, both associated with serious adverse effects. In order to avoid these complications and improve patient`s quality of life, an experimental study has been conducted on the preparation of a new generation of biodegradable poly D-L(lactide-co-glycolide (50:50) (PLGA) polymer microspheres (MSs) loaded with Dxm, vitamin E and/or human serum albumin (HSA). Particles were prepared according to a S/O/W encapsulation method and the 20-40μm fraction was selected. This narrow size distribution is suitable for minimally invasive intravitreal injection by small calibre needles. Characterisation of the MSs showed high Dxm loading and encapsulation efficiency (> 90%) without a strong interaction with the polymer matrix, as revealed by DSC analysis. MSs drug release studies indicated a small burst effect (lower than 5%) during the first five hours and subsequently, drug release was sustained for at least 30 days, led by diffusion and erosion mechanisms. Dxm release rate was modulated when solid state HSA was incorporated into MSs formulation. SDS-PAGE analysis showed that the protein maintained its integrity during the encapsulation process, as well as for the release study. MSs presented good tolerance and lack of cytotoxicity in macrophages and HeLa cultured cells. After 12 months of storage under standard refrigerated conditions (41ºC), MSs retained appropriate physical and chemical properties and analogous drug release kinetics. Therefore, we conclude that these microspheres are promising pharmaceutical systems for intraocular administration, allowing controlled release of the drug

The Use of Mucoadhesive Polymers to Enhance the Hypotensive Effect of a Melatonin Analogue, 5-MCA-NAT, in Rabbit Eyes

Purpose.: 5-Methoxy-carbonylamino-N-acetyltryptamine (5-MCA-NAT, a melatonin receptor agonist) produces a clear intraocular pressure (IOP) reduction in New Zealand White rabbits and glaucomatous monkeys. The goal of this study was to evaluate whether the hypotensive effect of 5-MCA-NAT was enhanced by the presence of cellulose derivatives, some of them with bioadhesive properties, as well as to determine whether these formulations were well tolerated by the ocular surface. Methods.: Formulations were prepared with propylene glycol (0.275%), carboxymethyl cellulose (CMC, 0.5% and 1.0%) of low and medium viscosity and hydroxypropylmethyl cellulose (0.3%). Quantification of 5-MCA-NAT (100 μM) was assessed by HPLC. In vitro tolerance was evaluated by the MTT method in human corneal-limbal epithelial cells and normal human conjunctival cells. In vivo tolerance was analyzed by biomicroscopy and specular microscopy in rabbit eyes. The ocular hypotensive effect was evaluated measuring IOP for 8 hours in rabbit eyes. Results.: All the formulations demonstrated good in vitro and in vivo tolerance. 5-MCA-NAT in CMC medium viscosity 0.5% was the most effective at reducing IOP (maximum IOP reduction, 30.27%), and its effect lasted approximately 7 hours. Conclusions.: The hypotensive effect of 5-MCA-NAT was increased by using bioadhesive polymers in formulations that are suitable for the ocular surface and also protective of the eye in long-term therapies. The use of 5-MCA-NAT combined with bioadhesive polymers is a good strategy in the treatment of ocular hypertension and glaucoma

The potential of using biodegradable microspheres in retinal diseases and other intraocular pathologies

Pathologies affecting the posterior segment are one of the major causes of blindness in developed countries and are becoming more prevalent due to the increase in society longevity. Sucessful therapy of diseases affecting the back of the eye requires effective concentrations of the active substance mantained during a long period of time in the intraocular target site. Treatment of vitreoretinal diseases often include repeated intravitreous injections that are associated with adverse effects. Local administration of biodegradable microspheres offers an excellent alternative to multiple administrations, as they are able to deliver the therapeutic molecule in a controlled fashion. Furthermore, injection of microparticles is performed without the need for surgical procedures. As most of the retinal diseases are multifactorial, microspheres result especially promising because they can be loaded with more than one active substance and complemented with the inclusion of additives with pharmacological properties. Personalized therapy can be easily achieved by changing the amount of administered microspheres. Contrary to non-biodegradable devices, biodegradable PLA and PLGA microspheres disappear from the site of administration after delivering the drug. Furthermore, microspheres prepared from these mentioned biomaterials are well tolerated after periocular and intravitreal injections in animals and humans. After injection, PLA and PLGA microspheres suffer aggregation behaving like an implant. Biodegradable microspheres are potential tools in regenerative medicine for retinal repair. According to the reported results, presumably a variety of microparticulate formulations for different ophthalmic therapeutic uses will be available in the clinical practice in the near future

Evaluación ergonómica mediante el método ROSA en docentes con teletrabajo de la UTEQ, 2020

This research project was carried out with the objective of making an ergonomic evaluation of the inappropriate postures adopted by the teachers of the Universidad Técnica Estatal de Quevedo in the telework modality, and then manage the results in a technical way. In the study, the sample was evaluated with two tools, the ROSA method, and the ergonomic survey, the results showed that teachers are affected by ergonomic risks, due to the current unfavorable conditions to carry out their daily telework activities from their homes; Likewise, it was identified that the affected parts of the teachers' bodies are the neck, upper and lower back, which is due to ignorance regarding the ergonomics they should have. After carrying out the respective evaluation through the software Ergoniza and analyzing the data, an action plan is proposed to train teachers, both in the use of physical work equipment and in the adaptation of the work environment; which allows mitigating and correcting risks to a certain degree. This will lead to generating the necessary controls to guarantee and protect the safety and health of workers.Este proyecto de investigación se realizó con el objetivo de realizar una evaluación ergonómica de las posturas inadecuadas adoptadas por los docentes de la Universidad Técnica Estatal de Quevedo en la modalidad de teletrabajo, y luego gestionar los resultados de manera técnica. En el estudio se evaluó la muestra con dos herramientas, el método ROSA, y la encuesta ergonómica, los resultados mostraron que los docentes se encuentran afectados por riesgos ergonómicos, debido a las condiciones actuales poco favorables para realizar sus actividades diarias de teletrabajo desde sus hogares; así mismo se identificó que las partes afectadas del cuerpo de los docentes son el cuello, la espalda alta y baja lo cual se debe al desconocimiento en cuanto la ergonomía que deben tener al realizar sus actividades. Luego de realizar la evaluación respectiva a través del software Ergoniza y analizados los datos, se propone un plan de acción para capacitar, instruir y fomentar cultura en los docentes, tanto en el uso de equipos físicos de trabajo como en la adecuación del entorno de trabajo; lo cual permita mitigar y corregir los riesgos en un cierto grado. Esto conllevará a generar los controles necesarios para garantizar y precautelar la seguridad y salud de los trabajadores

Gelatin Nanoparticles-HPMC Hybrid System for Effective Ocular Topical Administration of Antihypertensive Agents

The increment in ocular drug bioavailability after topical administration is one of the main challenges in pharmaceutical technology. For several years, different strategies based on nanotechnology, hydrogels or implants have been evaluated. Nowadays, the tolerance of ophthalmic preparations has become a critical issue and it is essential to the use of well tolerated excipients. In the present work, we have explored the potential of gelatin nanoparticles (GNPs) loaded with timolol maleate (TM), a beta-adrenergic blocker widely used in the clinic for glaucoma treatment and a hybrid system of TM-GNPs included in a hydroxypropyl methylcellulose (HPMC) viscous solution. The TM- loaded nanoparticles (mean particle size of 193 ± 20 nm and drug loading of 0.291 ± 0.019 mg TM/mg GNPs) were well tolerated both in vitro (human corneal cells) and in vivo. The in vivo efficacy studies performed in normotensive rabbits demonstrated that these gelatin nanoparticles were able to achieve the same hypotensive effect as a marketed formulation (0.5% TM) containing a 5-fold lower concentration of the drug. When comparing commercial and TM GNPs formulations with the same TM dose, nanoparticles generated an increased efficacy with a significant (p < 0.05) reduction of intraocular pressure (IOP) (from 21% to 30%) and an augmentation of 1.7-fold in the area under the curve (AUC)(0–12h). On the other hand, the combination of timolol-loaded nanoparticles (TM 0.1%) and the viscous polymer HPMC 0.3%, statistically improved the IOP reduction up to 30% (4.65 mmHg) accompanied by a faster time of maximum effect (tmax = 1 h). Furthermore, the hypotensive effect was extended for four additional hours, reaching a pharmacological activity that lasted 12 h after a single instillation of this combination, and leading to an AUC(0 12h) 2.5-fold higher than the one observed for the marketed formulation. According to the data presented in this work, the use of hybrid systems that combine well tolerated gelatin nanoparticles and a viscous agent could be a promising alternative in the management of high intraocular pressure in glaucoma

Nano and microtechnologies for ophthalmic administration. An overview

Ocular drug delivery is one of the most challenging fields of pharmaceutical research. They are generally employed to overcome the static (different layers of cornea, sclera, and retina including blood aqueous and blood-retinal barriers) and dynamic barriers (choroidal and conjunctival blood flow, lymphatic clearance, and tear dilution) of the eye. Ophthalmic formulations must be sterile, and the biomaterials used in the preparation of pharmaceutical systems completely compatible and extremely well tolerated by ocular tissues. The location of the target tissue in the eye will determine the route of administration. Ophthalmic administration systems are intended for topical, intraocular and periocular administration. In this review we describe the main pharmaceutical nano- and microsystems currently under study to administrate drugs in the eye, covering microparticles, nanoparticles, liposomes, microemulsions, niosomes and dendrimers. We have performed the corresponding revision of the published scientific literature always emphasizing the technological aspects. The review discusses also the biomaterials used in the preparation of the nano and microsystems of ophthalmic drug delivery, fabrication techniques, therapeutic significances, and future possibilities in the field

Thermo-Responsive PLGA-PEG-PLGA Hydrogels as Novel Injectable Platforms for Neuroprotective Combined Therapies in the Treatment of Retinal Degenerative Diseases

The present study aims to develop a thermo-responsive-injectable hydrogel (HyG) based on PLGA-PEG-PLGA (PLGA = poly-(DL-lactic acid co-glycolic acid); PEG = polyethylene glycol) to deliver neuroprotective agents to the retina over time. Two PLGA-PEG PLGA copolymers with different PEG:LA:GA ratios (1:1.54:23.1 and 1:2.25:22.5) for HyG-1 and HyG-2 development respectively were synthetized and characterized by different techniques (gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), critical micelle concentration (CMC), gelation and rheological behaviour). According to the physicochemical characterization, HyG-1 was selected for further studies and loaded with anti-inflammatory drugs: dexamethasone (0.2%), and ketorolac (0.5%), alone or in combination with the antioxidants idebenone (1 µM) and D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) (0.002%). In vitro drug release and cytotoxicity studies were performed for the active substances and hydrogels (loaded and drug-free). A cellular model based on oxidative stress was optimized for anti-inflammatory and antioxidant screening of the formulations by using retinal-pigmented epithelial cell line hTERT (RPE-1). The copolymer 1, used to prepare thermo-responsive HyG-1, showed low polydispersity (PDI = 1.22) and a strong gel behaviour at 25% (w/v) in an isotonic buffer solution close to the vitreous temperature (31–34 °C). Sustained release of dexamethasone and ketorolac was achieved between 47 and 62 days, depending on the composition. HyG-1 was well tolerated (84.5 ± 3.2%) in retinal cells, with values near 100% when the anti-inflammatory and antioxidant agents were included. The combination of idebenone and dexamethasone promoted high oxidative protection in the cells exposed to H2O2, with viability values of 86.2 ± 14.7%. Ketorolac and dexamethasone-based formulations ameliorated the production of TNF-α, showing significant results (p ≤ 0.0001). The hydrogels developed in the present study entail a novel biodegradable tool to treat neurodegenerative processes of the retina overtim

Novel liposome-based and in situ gelling artificial tear formulation for dry eye disease treatment

Purpose. Artificial tears are widely used in the treatment of dry eye disease, although current formulations do not closely resemble natural tears. The purpose of this study was the design and characterization of a novel in situ gelling artificial tear formulation, containing both lipid and aqueous components, in order to resemble natural tears and replenish the tear film. Methods. Liposomes, containing phosphatidylcholine, cholesterol, vitamins A and E, were prepared by the thin-film hydration method. The aqueous phase of the formulation was comprised of gellan gum, hydroxypropyl methylcellulose, levocarnitine, electrolytes (sodium chloride and potassium chloride), trehalose, and borates. The artificial tear was characterized in terms of liposome size, pH, surface tension, and viscosity. In vitro tolerance studies were performed in a human epithelial carcinoma cell line (HeLa) and a murine macrophage cell line (J774). In vivo tolerance was assessed in rabbits. Results. Liposomes presented a unimodal distribution with a mean size of 200.1 ± 4.4 nm. The resulting surface tension was 53.4 ± 1.1 mN/m (at 33°C) and the pH was 7.6 ± 0.1. The viscosity of the formulation presented a mean value of 4.0 ± 0.1 mPa.s within the shear rate interval of 200-1000 s-1 at 33°C. Cell viability remained higher than 90% in both cell lines. No discomfort or clinical signs were observed in rabbits. Conclusions. The liposome-based and in situ gelling artificial tear formulation presented good tolerance and suitable properties for topical ophthalmic administration. It may be beneficial in the treatment of dry eye disease

Dexamethasone PLGA Microspheres for Sub-Tenon Administration: Influence of Sterilization and Tolerance Studies

Many diseases affecting the posterior segment of the eye require repeated intravitreal injections with corticosteroids in chronic treatments. The periocular administration is a less invasive route attracting considerable attention for long-term therapies. In the present work, dexamethasone-loaded poly(lactic-co-glycolic) acid (PLGA) microspheres (Dx-MS) were prepared using the oil-in-water (O/W) emulsion solvent evaporation technique. MS were characterized in terms of mean particle size and particle size distribution, external morphology, polymer integrity, drug content, and in vitro release profiles. MS were sterilized by gamma irradiation (25 kGy), and dexamethasone release profiles from sterilized and non-sterilized microspheres were compared by means of the similarity factor (f2). The mechanism of drug release before and after irradiation exposure of Dx-MS was identified using appropriate mathematical models. Dexamethasone release was sustained in vitro for 9 weeks. The evaluation of the in vivo tolerance was carried out in rabbit eyes, which received a sub-Tenon injection of 5 mg of sterilized Dx-MS (20–53 µm size containing 165.6 ± 3.6 µg Dx/mg MS) equivalent to 828 µg of Dx. No detectable increase in intraocular pressure was reported, and clinical and histological analysis of the ocular tissues showed no adverse events up to 6 weeks after the administration. According to the data presented in this work, the sub-Tenon administration of Dx-MS could be a promising alternative to successive intravitreal injections for the treatment of chronic diseases of the back of the eye

Six month delivery of GDNF from PLGA/vitamin E biodegradable microspheres after intravitreal injection in rabbits

Local long-term delivery of glial cell line derived neurotrophic factor (GDNF) from vitamin E/poly-lactic-co-glycolic acid microspheres (MSs) protects retinal ganglion cells in an animal model of glaucoma for up to 11 weeks. However, the pharmacokinetics of GDNF after intravitreal injection of MSs is not known. We evaluated the GDNF levels after a single intravitreal injection of GDNF/VitE MSs. Biodegradable MSs were prepared by the solid-oil-in-water emulsion-solvent evaporation technique and characterized. Rabbits received a single intravitreal injection (50 μL) of GDNF/VitE MSs (4%w/v; 24 right eyes; 74.85 ng GDNF), blank MSs (4%w/v; 24 left eyes), and balanced salt solution (4 eyes). Two controls eyes received no injections. At 24 hours, 1, 4, 6, 8, 12, 18, and 24 weeks after injection, the eyes were enucleated, and the intravitreal GDNF levels were quantified. Pharmacokinetic data were analysed according to non-compartmental model. Intraocular GDNF levels of 717.1 ± 145.1 pg/mL were observed at 24 hours for GDNF-loaded MSs, followed by a plateau (745.3 ± 25.5 pg/mL) until day 28. After that, a second plateau (17.4 ± 3.7 pg/mL) occurred from 8 to 24 weeks postinjection, significantly higher than the basal levels. Eyes injected with GDNF/vitE and Blank-MSs did not show any abnormalities during the six-months follow up after administration. The single injection of GDNF/VitE MSs provided a sustained controlled release of the neurotrophic factor in a controlled fashion for up to six months