Development of mucoadhesive and thermosensitive eyedrops to improve the ophthalmic bioavailability of ibuprofen

Prolonged Release Niosomes For Ocular Delivery of Loteprednol: Ocular Distribution Assessment on Dry Eye Disease Induced Rabbit Model

Loteprednol etabonate (LE) is a topical corticosteroid for the symptomatic management of ocular conditions, encompassing both allergic and infectious etiologies. Owing to the dynamic and static barriers of the eye, LE exhibits significantly low bioavailability, necessitating an increase in the frequency of drug administration. The objective of this study is to overcome the limitations by developing niosomal systems loaded with LE. Design of Experiments (DoE) approach was used for the development of optimal niosome formulation. The optimal formulation was characterized using DLS, FT-IR, and DSC analysis. In vitro and ex vivo release studies were performed to demonstrate drug release patterns. After that HET-CAM evaluation was conducted to determine safety profile. Then, in vivo studies were carried out to determine therapeutic activity of niosomes. Zeta potential (ZP), particle size, polydispersity index (PI), and encapsulation efficacy (EE) were -33.8 mV, 89.22 nm, 0.192, and 89.6%, respectively. Medicated niosomes had a broad distribution within rabbit eye tissues and was absorbed by the aqueous humor of the bovine eye for up to 6 h after treatment. Cumulative permeated drug in the bovine eye and rabbit eye were recorded 52.45% and 54.8%, respectively. No irritation or hemorrhagic situation was observed according to the results of HET-CAM study. Thus, novel LE-loaded niosomal formulations could be considered as a promising treatment option for the dry-eye-disease (DED) due to enhanced bioavailability and decreased side effects.

Rheological and Injectability Evaluation of Sterilized Poloxamer-407-Based Hydrogels Containing Docetaxel-Loaded Lipid Nanoparticles

Nanostructured lipid carriers (NLCs) have the potential to increase the bioavailability and reduce the side effects of docetaxel (DTX). However, only a small fraction of nanoparticles given intravenously can reach a solid tumor. In situ-forming gels combined with nanoparticles facilitate local administration and promote drug retention at the tumor site. Injectable hydrogels based on poloxamer 407 are excellent candidates for this hybrid nanoparticle-hydrogel system because of their thermoresponsive behavior and biocompatibility. Therefore, this work aimed to develop injectable poloxamer hydrogels containing NLCs for intratumoral delivery of DTX. To ensure sterility, the obtained hydrogels were autoclaved (121 °C for 15 min) after preparation. Then, the incorporation of NLCs into the poloxamer hydrogels and the impact of steam sterilization on the nanocomposite hydrogels were evaluated concerning sol-gel transition, injectability, and physicochemical stability. All formulations were extruded through the tested syringe-needle systems with acceptable force (2.2-13.4 N) and work (49.5-317.7 N·mm) of injection. Following steam sterilization, injection became easier in most cases, and the physicochemical properties of all hydrogels remained practically unchanged according to the spectroscopical and thermal analysis. The rheological evaluation revealed that the nanocomposite hydrogels were liquid at 25 °C and underwent rapid gelation at 37 °C. However, their sterilized counterparts gelled at 1-2 °C above body temperature, suggesting that the autoclaving conditions employed had rendered these nanocomposite hydrogels unsuitable for local drug delivery.

Mucoadhesive Hybrid System of Silk Fibroin Nanoparticles and Thermosensitive In Situ Hydrogel for Amphotericin B Delivery: A Potential Option for Fungal Keratitis Treatment

The purpose of this work was to investigate the feasibility of a novel ophthalmic formulation of amphotericin B-encapsulated silk fibroin nanoparticles incorporated in situ hydrogel (AmB-FNPs ISG) for fungal keratitis (FK) treatment. AmB-FNPs ISG composites were successfully developed and have shown optimized physicochemical properties for ocular drug delivery. Antifungal effects against Candida albicans and in vitro ocular irritation using corneal epithelial cells were performed to evaluate the efficacy and safety of the composite formulations. The combined system of AmB-FNPs-ISG exhibited effective antifungal activity and showed significantly less toxicity to HCE cells than commercial AmB. In vitro and ex vivo mucoadhesive tests demonstrated that the combination of silk fibroin nanoparticles with in situ hydrogels could enhance the adhesion ability of the particles on the ocular surface for more than 6 h, which would increase the ocular retention time of AmB and reduce the frequency of administration during the treatment. In addition, AmB-FNP-PEG ISG showed good physical and chemical stability under storage condition for 90 days. These findings indicate that AmB-FNP-PEG ISG has a great potential and be used in mucoadhesive AmB eye drops for FK treatment.

Targeting posterior eye infections with colloidal carriers: The case of Ganciclovir

The ocular system, unlike any other human body organ, is a system in which foreign bodies appear quite defenceless in front of the eye. Several infections of the ocular system occur due to various opportunistic conditions. Cytomegalovirus (CMV) is one of the opportunivores that causes several posterior eye infections. Ganciclovir (GCV),9-(2-hydroxy-1-(hydroxymethyl) ethoxymethyl), is aguanine-antiviral agent primarily used to treat CMV diseases. However, the major challenge is of lower bioavailability. Hence, GCV must be dosed repeatedly to enhance drug absorption. but this causes side effects like neutropenia and bone marrow suppression. So, formulators have used alternative formulation strategies such as prodrug formulation and colloidal drug delivery systems. In the prodrug strategy, they attempted to bind various compounds into the parent drug to increase the permeability and bioavailability of GCV. In colloidal drug delivery systems, mucoadhesive microspheres, nanoparticles, Niosome and liposome were employed to extend the drug residence time at the application site. This paper discusses several colloidal carriers combined with GCV to treat opportunistic CMV infection in the posterior ocular system. It reviews the limitations of conventional ocular therapy and explores various novel formulation approaches to improve the ocular bioavailability of GCV in the posterior chamber of the eye.

Chitosan-Coated SLN: A Potential System for Ocular Delivery of Metronidazole

Ophthalmic drops for ocular delivery exhibit inadequate residence time, which often requires multiple daily dosing that may result in patient non-adherence. In this study, the development of a once-daily-dosed chitosan-coated metronidazole (MTZ)-loaded solid lipid nanoparticles (SLNs) for ocular delivery was undertaken. Melt emulsification and ultrasonication were used to manufacture MTZ-loaded SLN, which were subsequently coated with chitosan (CS) by mechanical stirring using a 0.1% w/v solution. Gelucire^® 48/16 and Transcutol^® HP were used as the solid lipid and synthetic solvent, respectively, with Tween^® 20 included as a stabilizing agent. The critical quality attributes (CQA) of the optimized CS-coated SLN that was monitored included particle size, polydispersity index, Zeta potential, % entrapment efficiency, % MTZ loading, pH, and osmolarity. The optimized coated nanocarriers were evaluated using laser Doppler anemometry (LDA) and were determined to be stable, with particle sizes in the nanometre range. In vitro mucoadhesion, MTZ release and short-term stability, in addition to the determination of the shape of the optimized CS-coated SLN, were undertaken. The mucoadhesive properties of the optimized CS-coated MTZ-loaded SLN demonstrated increased ocular availability, which may allow dose reduction or longer intervals between doses by improving precorneal retention and ocular availability. Overall, our findings suggest that CS-coated MTZ-loaded SLNs have the potential for clinical application, to enhance ocular delivery through the release of MTZ.

Effects of Steam Sterilization on the Properties of Stimuli-Responsive Polymer-Based Hydrogels

Hydrogels based on stimuli-responsive polymers can change their characteristics in response to small variations in environmental conditions, such as temperature, pH, and ionic strength, among others. In the case of some routes of administration, such as ophthalmic and parenteral, the formulations must meet specific requirements, namely sterility. Therefore, it is essential to study the effect of the sterilization method on the integrity of smart gel systems. Thus, this work aimed to study the effect of steam sterilization (121 °C, 15 min) on the properties of hydrogels based on the following stimuli-responsive polymers: Carbopol® 940, Pluronic® F-127, and sodium alginate. The properties of the prepared hydrogels-pH, texture, rheological behavior, and sol-gel phase transition-were evaluated to compare and identify the differences between sterilized and non-sterilized hydrogels. The influence of steam sterilization on physicochemical stability was also investigated by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The results of this study showed that the Carbopol® 940 hydrogel was the one that suffered fewer changes in the studied properties after sterilization. By contrast, sterilization was found to cause slight changes in the Pluronic® F-127 hydrogel regarding gelation temperature/time, as well as a considerable decrease in the viscosity of the sodium alginate hydrogel. There were no considerable differences in the chemical and physical characteristics of the hydrogels after steam sterilization. It is possible to conclude that steam sterilization is suitable for Carbopol® 940 hydrogels. Contrarily, this technique does not seem adequate for the sterilization of alginate or Pluronic® F-127 hydrogels, as it could considerably alter their properties.

Thermoresponsive mucoadhesive hybrid gels in advanced drug delivery systems

Thermoresponsive polymers have seen extensive use in the development of stimuli-responsive drug formulations for oral, buccal, nasal, ocular, topical, rectal, parenteral, and vaginal routes of administration. Despite their great potential, their use has been limited by various obstacles, such as undesirable high polymer concentration, wide gelation temperature, low gel strength, poor mucoadhesiveness, and short retention. Mucoadhesive polymers have been suggested to improve the mucoadhesive features of thermoresponsive gels, leading to increased drug bioavailability and efficacy. This article highlights the use of in-situ thermoresponsive mucoadhesive hydrogel blends or hybrids that have been developed and assessed in various routes of administration.

Multiple Roles of Chitosan in Mucosal Drug Delivery: An Updated Review

Chitosan (CS) is a linear polysaccharide obtained by the deacetylation of chitin, which, after cellulose, is the second biopolymer most abundant in nature, being the primary component of the exoskeleton of crustaceans and insects. Since joining the pharmaceutical field, in the early 1990s, CS attracted great interest, which has constantly increased over the years, due to its several beneficial and favorable features, including large availability, biocompatibility, biodegradability, non-toxicity, simplicity of chemical modifications, mucoadhesion and permeation enhancer power, joined to its capability of forming films, hydrogels and micro- and nanoparticles. Moreover, its cationic character, which renders it unique among biodegradable polymers, is responsible for the ability of CS to strongly interact with different types of molecules and for its intrinsic antimicrobial, anti-inflammatory and hemostatic activities. However, its pH-dependent solubility and susceptibility to ions presence may represent serious drawbacks and require suitable strategies to be overcome. Presently, CS and its derivatives are widely investigated for a great variety of pharmaceutical applications, particularly in drug delivery. Among the alternative routes to overcome the problems related to the classic oral drug administration, the mucosal route is becoming the favorite non-invasive delivery pathway. This review aims to provide an updated overview of the applications of CS and its derivatives in novel formulations intended for different methods of mucosal drug delivery.

Colloidal nanosystems with mucoadhesive properties designed for ocular topical delivery

Over the last years, the scientific interest about topical ocular delivery targeting the posterior segment of the eye has been increasing. This is probably due to the fact that this is a non-invasive administration route, well tolerated by patients and with fewer local and systemic side effects. However, it is a challenging task due to the external ocular barriers, tear film clearance, blood flow in the conjunctiva and choriocapillaris and due to the blood-retinal barriers, amongst other features. An enhanced intraocular bioavailability of drugs can be achieved by either improving corneal permeability or by improving precorneal retention time. Regarding this last option, increasing residence time in the precorneal area can be achieved using mucoadhesive polymers such as xyloglucan, poly(acrylate), hyaluronic acid, chitosan, and carbomers. On the other hand, colloidal particles can interact with the ocular mucosa and enhance corneal and conjunctival permeability. These nanosystems are able to deliver a wide range of drugs, including macromolecules, providing stability and improving ocular bioavailability. New pharmaceutical approaches based on nanotechnology associated to bioadhesive compounds have emerged as strategies for a more efficient treatment of ocular diseases. Bearing this in mind, this review provides an overview of the current mucoadhesive colloidal nanosystems developed for ocular topical administration, focusing on their advantages and limitations.

Nanostructured Lipid Carriers Engineered as Topical Delivery of Etodolac: Optimization and Cytotoxicity Studies

Etodolac (ETD), a nonsteroidal anti-inflammatory drug, exhibits antinflammatory, analgesic, and antipyretic activity. The main type of ETD administration is oral route, which is associated with significant systemic side effects. Nanostructured lipid carriers (NLC), a modern lipid formulation, are non-toxic, biocompatible, can improve the solubility and stability of drugs. Nanostructured lipid carriers (NLC) containing etodolac were prepared by a melt-emulsification and ultrasonication technique. Full factorial design (FFD) was applied to optimize the composition of NLC and their properties such as zeta potential, polidyspersity index, and entrapment efficiency. Formulations consisting of Capryol 90, glicerol monostearate, and Tween 20 displayed particle size below 300 nm, encapsulated drug with efficiency of approximately 87% and prolonged drug release up to 24 h. Stable formulations displayed moderately negative surface charge suggesting their limited ability to interact with skin surface but simultaneously presenting their lower risk to cause cell-membrane disruption. In fact, cytotoxicity assessment using human dermal fibroblasts and human epidermal keratinocytes revealed that etodolac-loaded NLC had no important impact on skin cells viability evaluated in vitro, which might evidence that NLC formulations are safe for dermal delivery. The studies developed were relatively fast and simple, requiring no specialized equipment method to prepare NLC as ETD carriers ensuring better solubility and prolonged drug release.

Recent advances in thermo-sensitive hydrogels for drug delivery

Thermo-sensitive hydrogels based on different polymers have been broadly used in the pharmaceutical fields. In this review, the state-of-the-art thermo-sensitive hydrogels for drug delivery are elaborated

Chitosan and its Derivatives for Ocular Delivery Formulations: Recent Advances and Developments

Chitosan (CS) is a hemi-synthetic cationic linear polysaccharide produced by the deacetylation of chitin. CS is non-toxic, highly biocompatible, and biodegradable, and it has a low immunogenicity. Additionally, CS has inherent antibacterial properties and a mucoadhesive character and can disrupt epithelial tight junctions, thus acting as a permeability enhancer. As such, CS and its derivatives are well-suited for the challenging field of ocular drug delivery. In the present review article, we will discuss the properties of CS that contribute to its successful application in ocular delivery before reviewing the latest advances in the use of CS for the development of novel ophthalmic delivery systems. Colloidal nanocarriers (nanoparticles, micelles, liposomes) will be presented, followed by CS gels and lenses and ocular inserts. Finally, instances of CS coatings, aiming at conferring mucoadhesiveness to other matrixes, will be presented.

Recent developments in regenerative ophthalmology

Regenerative medicine (RM) is one of the most promising disciplines for advancements in modern medicine, and regenerative ophthalmology (RO) is one of the most active fields of regenerative medicine. This review aims to provide an overview of regenerative ophthalmology, including the range of tools and materials being used, and to describe its application in ophthalmologic subspecialties, with the exception of surgical implantation of artificial tissues or organs (e.g., contact lens, artificial cornea, intraocular lens, artificial retina, and bionic eyes) due to space limitations. In addition, current challenges and limitations of regenerative ophthalmology are discussed and future directions are highlighted.

In Vitro and Ex Vivo Evaluation of Nepafenac-Based Cyclodextrin Microparticles for Treatment of Eye Inflammation

The aim of this study was to design and evaluate novel cyclodextrin (CD)-based aggregate formulations to efficiently deliver nepafenac topically to the eye structure, to treat inflammation and increase nepafenac levels in the posterior segment, thus attenuating the response of inflammatory mediators. The physicochemical properties of nine aggregate formulations containing nepafenac/γ-CD/hydroxypropyl-β (HPβ)-CD complexes as well as their rheological properties, mucoadhesion, ocular irritancy, corneal and scleral permeability, and anti-inflammatory activity were investigated in detail. The results were compared with a commercially available nepafenac suspension, Nevanac^® 3 mg/mL. All formulations showed microparticles, neutral pH, and negative zeta potential (–6 to –27 mV). They were non-irritating and nontoxic and showed high permeation through bovine sclera. Formulations containing carboxymethyl cellulose (CMC) showed greater anti-inflammatory activity, even higher than the commercial formulation, Nevanac^® 0.3%. The optimized formulations represent an opportunity for topical instillation of drugs to the posterior segment of the eye.

Design of Silk-Elastin-Like Protein Nanoparticle Systems with Mucoadhesive Properties

Transmucosal drug delivery is a promising avenue to improve therapeutic efficacy through localized therapeutic administration. Drug delivery systems that increase retention in the mucosal layer are needed to improve efficiency of such transmucosal platforms. However, the applicability of such systems is often limited by the range of chemistries and properties that can be achieved. Here we present the design and implementation of silk-elastin-like proteins (SELPs) with mucoadhesive properties. SELP-based micellar-like nanoparticles provide a system to tailor chemical and physical properties through genetic engineering of the SELP sequence, which enables the fabrication of nanoparticles with specific chemical and physical features. Analysis of the adhesion of four different SELP-based nanoparticle systems in an artificial mucus system, as well as in in vitro cellular assays indicates that addition of mucoadhesive chemical features on the SELP systems increases retention of the particles in mucosal environments. The results indicated that SELP-based nanoparticles provide a useful approach to study and develop transmucosal protein drug delivery system with unique mucoadhesive properties. Future studies will serve to further expand the range of achievable properties, as well as the utilization of SELPs to fabricate mucoadhesive materials for in vivo testing.

Lipid Nanoparticles and Their Hydrogel Composites for Drug Delivery: A Review

Several drug delivery systems already exist for the encapsulation and subsequent release of lipophilic drugs that are well described in the scientific literature. Among these, lipid nanoparticles (LNP) have specifically come up for dermal, transdermal, mucosal, intramuscular and ocular drug administration routes in the last twenty years. However, for some of them (especially dermal, transdermal, mucosal), the LNP aqueous dispersions display unsuitable rheological properties. They therefore need to be processed as semi-solid formulations such as LNP-hydrogel composites to turn into versatile drug delivery systems able to provide precise spatial and temporal control of active ingredient release. In the present review, recent developments in the formulation of lipid nanoparticle-hydrogel composites are highlighted, including examples of successful encapsulation and release of lipophilic drugs through the skin, the eyes and by intramuscular injections. In relation to lipid nanoparticles, a specific emphasis has been put on the LNP key properties and how they influence their inclusion in the hydrogel. Polymer matrices include synthetic polymers such as poly(acrylic acid)-based materials, environment responsive (especially thermo-sensitive) polymers, and innovative polysaccharide-based hydrogels. The composite materials constitute smart, tunable drug delivery systems with a wide range of features, suitable for dermal, transdermal, and intramuscular controlled drug release.

A potential nanoparticle-loaded in situ gel for enhanced and sustained ophthalmic delivery of dexamethasone

Increasing the permeability of drugs across the cornea is key to improving drug absorption by the eye. This study presents a newly developed in situ gel loaded with nanoparticles, which could achieve controlled drug release and high ocular drug bioavailability by avoiding rapid precorneal clearance. The physicochemical parameters of the formulation were investigated and showed uniform size, physical stability, and favorable rheological and gelling properties. Ex vivo permeation studies revealed significantly higher drug release from the in situ gel loaded with nanoparticles compared to the conventional poloxamer in situ gel and the drug solution. When compared with a marketed formulation, the in situ gel loaded with nanoparticles provided slower controlled release and higher ocular bioavailability of dexamethasone. In conclusion, the developed nanoparticle-loaded in situ gel can successfully increase drug ocular bioavailability by enhancing contact time with the ocular surface and permeation through the cornea.

A hybrid genipin-crosslinked dual-sensitive hydrogel/nanostructured lipid carrier ocular drug delivery platform

The objective of this study was to develop a novel hybrid genipin-crosslinked dual-sensitive hydrogel/nanostructured lipid carrier (NLC) drug delivery platform. An ophthalmic anti-inflammatory drug, baicalin (BN) was chosen as the model drug. BN-NLC was prepared using melt-emulsification combined with ultra-sonication technique. Additionally, a dual pH- and thermo-sensitive hydrogel composed of carboxymethyl chitosan (CMCS) and poloxamer 407 (F127) was fabricated by a cross-linking reaction with a nontoxic crosslinker genipin (GP). GP-CMCS/F127 hydrogel was characterized by FTIR, NMR, XRD and SEM. The swelling studies showed GP-CMCS/F127 hydrogel was both pH- and thermo-sensitive. The results of in vitro release suggested BN-NLC gel can prolong the release of baicalin comparing with BN eye drops and BN-NLC. Ex vivo cornea permeation study was evaluated using Franz diffusion cells. The apparent permeability coefficient (P_app ) of BN-NLC gel was much higher (4.46-fold) than that of BN eye drops. Through the determination of corneal hydration levels, BN-NLC gel was confirmed that had no significant irritation to cornea. Ex vivo precorneal retention experiments were carried out by a flow-through approach. The results indicated that the NLC-based hydrogel can prolong precorneal residence time. In conclusion, the hybrid NLC-based hydrogel has a promising potential for application in ocular drug delivery.

Development and characterization of mucoadhesive buccal gels containing lipid nanoparticles of ibuprofen

The lipid nanoparticles, namely Nanostructured Lipid Carriers (NLC), as drug delivery systems have been investigated for several years. One of the delivery routes for which these carriers can be applied is buccal administration. However, the liquid dispersions of lipid nanoparticles can be rapidly removed from oral cavity by saliva. Thus, the development of a system that allows increased retention time on the mucosa is necessary. For this reason, the development of mucoadhesive preparations for buccal administration of lipid nanoparticles becomes important. Hydrogels prepared with mucoadhesive polymers (Carbopol^® 980 and polycarbophil) constitute a promising option. The aim of this work was to develop mucoadhesive buccal hydrogels with NLC, using ibuprofen as a model drug. The obtained results showed that the developed NLC dispersions presented particles in the nanometric size range, with low polydispersity index values and efficient ability for the entrapment of the model drug. Moreover, the incorporation of NLC in hydrogels of mucoadhesive polymers resulted in preparations with desirable rheological features as well as texture (firmness and adhesiveness) and mucoadhesive properties, which could benefit the therapeutic efficacy, by increasing the residence time and easiness for topical application in the buccal mucosa. Additionally, the developed preparations exhibited sustained drug release as intended for these systems.

Nanostructured lipid carrier (NLC)-based novel hydrogels as potential carriers for nepafenac applied after cataract surgery for the treatment of inflammation: design, characterization and in vitro cellular inhibition and uptake studies

Schematic illustration of the novel formulation (nanostructured lipid carriers-based novel hydrogels) instills into the surface of eyes and the results of cytotoxicity and cell uptake for optimal formulation.