In vitro and in vivo ocular safety and eye surface permanence determination by direct and Magnetic Resonance Imaging of ion-sensitive hydrogels based on gellan gum and kappa-carrageenan

Preparation of dried nanoemulsion formulation by electrospinning

Dry eye disease is a multifactorial condition characterized by a loss of homeostasis of the tear film. Among the various treatment approaches, the application of ophthalmic oil-in-water nanoemulsions with incorporated anti-inflammatory drugs represents one of the most advanced approaches. However, the liquid nature of nanoemulsions limits their retention time at the ocular surface. Transforming the nanoemulsions into a dry form that would disperse rapidly in the tear fluid would improve the retention of the drug at the ocular surface. The aim of this study was to investigate electrospinning as a method for the preparation of a solid eye preparation based on nanoemulsion loaded with the anti-inflammatory drug loteprednol etabonate. Four nanoemulsions differing in oil-to-surfactant ratios were incorporated in hydrophilic nanofibers based on polyethylene oxide, poloxamer 188, and Soluplus®. The dried nanoemulsions in the form of nanofibers dispersed readily on contact with aqueous medium, resulting in a dispersion of nanometre-sized droplets with average size comparable to the average droplet size of the initial nanoemulsions. A rheological study revealed the predominant elastic behavior of the dispersed nanofibers, which indicates the formation of a weak gel after the dispersion of the dried nanoemulsion in tear fluid at the ocular surface. The biocompatibility of the dried nanoemulsions in the form of nanofibers after a single and multiple-dose application was confirmed using the 3D HCE-T model of the stratified epithelium of the human cornea, suggesting that this innovative solid eye preparation could represent a new approach to the treatment of dry eye disease.

Revolutionizing Ophthalmic Care: A Review of Ocular Hydrogels from Pathologies to Therapeutic Applications

PURPOSE

This comprehensive review is designed to elucidate the transformative role and multifaceted applications of ocular hydrogels in contemporary ophthalmic therapeutic strategies, with a particular emphasis on their capability to revolutionize drug delivery mechanisms and optimize patient outcomes.

METHODS

A systematic and structured methodology is employed, initiating with a succinct exploration of prevalent ocular pathologies and delineating the corresponding therapeutic agents. This serves as a precursor for an extensive examination of the diverse methodologies and fabrication techniques integral to the design, development, and application of hydrogels specifically tailored for ophthalmic pharmaceutical delivery. The review further scrutinizes the pivotal manufacturing processes that significantly influence hydrogel efficacy and delves into an analysis of the current spectrum of hydrogel-centric ocular formulations.

RESULTS

The review yields illuminating insights into the escalating prominence of ocular hydrogels within the medical community, substantiated by a plethora of ongoing clinical investigations. It reveals the dynamic and perpetually evolving nature of hydrogel research and underscores the extensive applicability and intricate progression of transposing biologics-loaded hydrogels from theoretical frameworks to practical clinical applications.

CONCLUSIONS

This review accentuates the immense potential and promising future of ocular hydrogels in the realm of ophthalmic care. It not only serves as a comprehensive guide but also as a catalyst for recognizing the transformative potential of hydrogels in augmenting drug delivery mechanisms and enhancing patient outcomes. Furthermore, it draws attention to the inherent challenges and considerations that necessitate careful navigation by researchers and clinicians in this progressive field.

Gellan gum-based in-situ gel formulations for ocular drug delivery: A practical approach

Ophthalmic disorders significantly impact global health, affecting millions worldwide. Conventional treatments often face challenges related to poor bioavailability and short residence times on the ocular surface. In recent years, in-situ gels prepared using different natural gums including gellan gum has been investigated as a viable means of improving ocular medication delivery. Gellan gum undergoes ionotropic-gelation in the presence of multivalent cations, making it suitable for ocular formulations. The synthesis and purification of gellan gum involve microbial fermentation processes. Incorporating gellan gum into ophthalmic formulations offers several advantages, including prolonged residence time, enhanced drug retention, and improved bioavailability. Characterisation techniques such as gelling capacity determination, FTIR spectroscopy, TEM, viscosity and rheological studies and ex-vivo or in-vitro release studies are crucial for assessing the structural and functional properties of gellan gum-based in-situ gels. Numerous investigations have exhibited gellan gum's potential in different drug loaded in-situ gels for ophthalmic uses, resulting in extended drug residency on the ocular surface and enhanced therapeutic effects. The current review presents a comprehensive discussion on preparation, characterisation, recent applications and future prospects of gellan gum-based in-situ gels for ocular drug delivery. In addition, it covers molecular structure, synthesis and characterisation of gellan gum.

Stimuli-responsive carrageenan-based biomaterials for biomedical applications

Carrageenan-based biomaterials have attracted considerable attention in recent years due to their unique biological properties, including their biodegradability, compatibility, and lack of adverse effects. These biomaterials exhibit a variety of beneficial properties, such as antiviral, antitumor, and immunomodulatory effects, which set them apart from other polysaccharides. Stimuli-responsive carrageenan-based biomaterials have attracted particular attention due to their unique properties, such as reducing systemic toxicity and controlling drug release. In this review, a comprehensive investigation of stimuli-responsive carrageenan-based biomaterials was conducted under the influence of various stimuli such as pH, electric field, magnetic field, temperature, light, and ions. These structures exhibited good stimulus-responsive properties and involved corresponding physical and chemical changes, such as changes in swelling ratio and gelling power among others. The biomedical application of carrageenan-based stimuli-responsive biomaterials in the field of tissue engineering, anticancer, antibacterial, and food monitoring has been investigated, showing the great potential of these structures. Although there are promising developments in the design and use of stimuli-responsive carrageenan-based biomaterials, further research is advisable to further investigate their potential applications, particularly in animal models. Extensive studies are needed to investigate the benefits and limitations of these materials to ensure their safety and effective use in biomedical applications.

Fostering the unleashing potential of nanocarriers-mediated delivery of ocular therapeutics

Ocular delivery is the most challenging aspect in the field of pharmaceutical research. The major hurdle for the controlled delivery of drugs to the eye includes the physiological static barriers such as the complex layers of the cornea, sclera and retina which restrict the drug from permeating into the anterior and posterior segments of the eye. Recent years have witnessed inventions in the field of conventional and nanocarrier drug delivery which have shown considerable enhancement in delivering small to large molecules across the eye. The dynamic challenges associated with conventional systems include limited drug contact time and inadequate ocular bioavailability resulting from solution drainage, tear turnover, and dilution or lacrimation. To this end, various bioactive-based nanosized carriers including liposomes, ethosomes, niosomes, dendrimer, nanogel, nanofibers, contact lenses, nanoprobes, selenium nanobells, nanosponge, polymeric micelles, silver nanoparticles, and gold nanoparticles among others have been developed to circumvent the limitations associated with the conventional dosage forms. These nanocarriers have been shown to achieve enhanced drug permeation or retention and prolong drug release in the ocular tissue due to their better tissue adherence. The surface charge and the size of nanocarriers (10-1000 nm) are the important key factors to overcome ocular barriers. Various nanocarriers have been shown to deliver active therapeutic molecules including timolol maleate, ampicillin, natamycin, voriconazole, cyclosporine A, dexamethasone, moxifloxacin, and fluconazole among others for the treatment of anterior and posterior eye diseases. Taken together, in a nutshell, this extensive review provides a comprehensive perspective on the numerous facets of ocular drug delivery with a special focus on bioactive nanocarrier-based approaches, including the difficulties and constraints involved in the fabrication of nanocarriers. This also provides the detailed invention, applications, biodistribution and safety-toxicity of nanocarriers-based therapeutcis for the ophthalmic delivery.

Carrageenan films as promising mucoadhesive ocular drug delivery systems

Polymer mucoadhesive films being developed for use in ophthalmology represent a new tool for drug delivery and are considered an alternative to traditional dosage forms. Due to their mucoadhesive properties, carrageenans (CRGs) are widely used in various forms for drug delivery. In this study, films based on CRGs of various structural types (κ/β, κ, x, and λ) for use in ophthalmology were studied. The films were loaded with the active substance echinochrome (ECH), a sea urchin pigment used in ophthalmology. Spectral data showed that ECH remained stable after its incorporation into the CRG films and did not oxidize for at least six months. Hydrophilic CRG films with a thickness of 10-12 µm were characterized in terms of their swelling and mucoadhesive properties. The rheological properties of solutions formed after film dissolution in artificial tears were also assessed. κ- and κ/β-CRG films with ECH exhibited pseudoplastic behavior after rehydrating films with an artificial tear solution. The CRG-loaded films had different swelling characteristics depending on the structure of the CRG used. The films based on highly sulfated CRGs dissolved in artificial tears, while the films of low-sulfated κ/β-CRG exhibited limited swelling. All studied ECH-loaded films exhibited mucoadhesive properties, which were evaluated by a texture analyzer using mucous tissue of the small intestine of the pig as a model. There was a slight prolongation of ECH release from CRG films in artificial tears. The effect of CRG/ECH on the epithelial cell lines of the outer shell of the human eye was investigated. At low concentrations, ECH in the composition of the CRG/ECH complex had no cytotoxic effect on corneal epithelial and conjunctival human cells. The use of ECH-containing films can prevent the drug from being immediately washed away by tears and help to retain it by increasing viscosity and having mucoadhesive properties.

In-situ gel: A smart carrier for drug delivery

In-situ gel technology is a promising drug delivery strategy that undergoes a 'sol to gel' transition upon administration, providing controlled and prolonged drug release. These gels are composed of cross-linked 3D networks of polymers, with hydrogels being a specific type of absorbing water while retaining their shape. Gelation can be triggered by various stimuli, such as temperature, pH, ions, and light. They offer several advantages like improved patient compliance, extended drug residence time, localized drug delivery, etc, but also have some disadvantages like drug degradation and limited mechanical strength. In-situ gel falls into three categories: temperature-sensitive, ion-sensitive, and pH-sensitive, but multi-responsive gels that respond to multiple stimuli have better drug release characteristics. The mechanism of in-situ gel formation involves physical and chemical mechanisms. There are various applications of in-situ gel, like ocular drug delivery, nose-to-brain delivery, etc. In this review, we have discussed the types, and mechanisms of in-situ gel & use of in-situ gel in the treatment of different diseases through various routes like buccal, vaginal, ocular, nasal, etc., along with its use in targeted drug delivery.

Bilayer wound dressing composed of asymmetric polycaprolactone membrane and chitosan-carrageenan hydrogel incorporating storax balsam

A comprehensive approach is needed to develop multifunctional wound dressing that is simple yet efficient. In this work, Liquidambar orientalis Mill. storax loaded hydroxyethyl chitosan (HECS)-carrageenan (kC) based hydrogel (HECS-kC) and polydopamine coated asymmetric polycaprolactone membrane (PCL-DOP) were used to develop a multifunctional and modular bilayer wound dressing. Asymmetric PCL-DOP membrane was prepared by non-solvent induced phase separation (NIPS) followed by polydopamine coating and demonstrated an excellent barrier against bacteria while allowing permeability for 5.45 ppm dissolved‑oxygen and 2130 g/m2 water vapor transmission in 24 h in addition to 805 kPa tensile strength. Storax loaded HECS-kC hydrogel, on the other hand, demonstrated a pH-responsive degradation and swelling to provide necessary conditions to facilitate wound healing. The hydrogels showed stretchability above 140 %, mild adhesive strength on sheep skin and PCL-DOP membrane, while the storax incorporation enhanced antibacterial and antioxidant activity. Furthermore, rat full-thickness skin defect model showed that the developed bilayer wound dressing could significantly facilitate wound healing compared to Tegaderm™ and control groups. This study shows that the bilayered wound dressing has the potential to be used as a simple and effective wound care system.

Carrageenan tethered ion sensitive smart nanogel containing oleophytocubosomes for improved ocular luteolin delivery

Ophthalmic delivery of luteolin (LU) was studied after formulating a carrageenan-based novel ion-sensitive in situ gel (ISG) incorporating oleophytocubosomes for prolonged ocular residence time and improved ocular bioavailability of the poorly absorbed herbal drug luteolin. The prepared oleophytocubosomes and ISG were compared with LU suspension. Optimized oleophytocubosomes possessed small, homogenously distributed negatively charged particles with high entrapment efficiency. Polarized light microscope revealed a cubic phase. Optimized ISG matrix composed of 0.4% kappa carrageenan (KC), and 2% hydroxypropylmethylcellulose (HPMC) demonstrated rapid gelation, high resistance to dilution, increased viscosity after gelation, and strong mucoadhesive properties. oleophytocubosomes exerted improved drug release, while a more sustained release was observed for ISG oleophytocubosomes. The antioxidant activity of both formulations was significantly higher than that of LU suspension. Oleophytocubosome and ISG oleophytocubosome revealed significantly higher apparent permeability coefficients of 3.62 and 2.90 folds, respectively, compared to LU suspension. Irritation tests showed the safety of both formulations for single- and multiple-ocular administration. In-vivo studies demonstrated that the ISG system showed prolonged antiglaucoma effects and a faster anti-inflammatory effect, followed by oleophytocubosomes.

Nanomedicine for the Detection and Treatment of Ocular Bacterial Infections

Ocular bacterial infection is a prevalent cause of blindness worldwide, with substantial consequences for normal human life. Traditional treatments for ocular bacterial infections areless effective, necessitating the development of novel techniques to enable accurate diagnosis, precise drug delivery, and effective treatment alternatives. With the rapid advancement of nanoscience and biomedicine, increasing emphasis has been placed on multifunctional nanosystems to overcome the challenges posed by ocular bacterial infections. Given the advantages of nanotechnology in the biomedical industry, it can be utilized to diagnose ocular bacterial infections, administer medications, and treat them. In this review, the recent advancements in nanosystems for the detection and treatment of ocular bacterial infections are discussed; this includes the latest application scenarios of nanomaterials for ocular bacterial infections, in addition to the impact of their essential characteristics on bioavailability, tissue permeability, and inflammatory microenvironment. Through an in-depth investigation into the effect of sophisticated ocular barriers, antibacterial drug formulations, and ocular metabolism on drug delivery systems, this review highlights the challenges faced by ophthalmic medicine and encourages basic research and future clinical transformation based on ophthalmic antibacterial nanomedicine.

Controlled Drug Release from Nanoengineered Polysaccharides

Polysaccharides are naturally occurring complex molecules with exceptional physicochemical properties and bioactivities. They originate from plant, animal, and microbial-based resources and processes and can be chemically modified. The biocompatibility and biodegradability of polysaccharides enable their increased use in nanoscale synthesis and engineering for drug encapsulation and release. This review focuses on sustained drug release studies from nanoscale polysaccharides in the fields of nanotechnology and biomedical sciences. Particular emphasis is placed on drug release kinetics and relevant mathematical models. An effective release model can be used to envision the behavior of specific nanoscale polysaccharide matrices and reduce impending experimental trial and error, saving time and resources. A robust model can also assist in translating from in vitro to in vivo experiments. The main aim of this review is to demonstrate that any study that establishes sustained release from nanoscale polysaccharide matrices should be accompanied by a detailed analysis of drug release kinetics by modeling since sustained release from polysaccharides not only involves diffusion and degradation but also surface erosion, complicated swelling dynamics, crosslinking, and drug-polymer interactions. As such, in the first part, we discuss the classification and role of polysaccharides in various applications and later elaborate on the specific pharmaceutical processes of polysaccharides in ionic gelling, stabilization, cross-linking, grafting, and encapsulation of drugs. We also document several drug release models applied to nanoscale hydrogels, nanofibers, and nanoparticles of polysaccharides and conclude that, at times, more than one model can accurately describe the sustained release profiles, indicating the existence of release mechanisms running in parallel. Finally, we conclude with the future opportunities and advanced applications of nanoengineered polysaccharides and their theranostic aptitudes for future clinical applications.

In situ gelling drug delivery systems for topical drug delivery

In situ gelling formulations are drug delivery systems which typically exist in a liquid form at room temperature and change into gel state after application to the body in response to various stimuli such as changes in temperature, pH and ionic composition. Their biomedical application can further be improved by incorporating drug nanoparticles into in situ gelling systems in order to prolong drug release, reduce dosing frequency and improve therapeutic outcomes of patients, developing highly functional but challenging dosage forms. The composition of in situ gelling formulations influence factors relating to performance such as their syringeability, rheology, drug release profile and drug bioavailability at target sites, amongst other factors. The inclusion of mucoadhesive polymeric constituents into in situ gelling formulations has also been explored to ensure that the therapeutic agents are retained at target site for extended period of time. This review article will discuss traditional techniques (water bath-based vial inversion and viscometry) as well as advanced methodology (rheometry, differential scanning calorimetry, Small Angle Neutron Scattering, Small Angle X-ray Scattering, etc.) for evaluating in situ gel forming systems for topical drug delivery. The clinical properties of in situ gelling systems that have been studied for potential biomedical applications over the last ten years will be reviewed to highlight current knowledge in the performance of these systems. Formulation issues that have slowed the translation of some promising drug formulations from the research laboratory to the clinic will also be detailed.

Preparation and Characterization of Ion-Sensitive Brimonidine Tartrate In Situ Gel for Ocular Delivery

Brimonidine tartrate (BRT) is a highly selective α2 adrenergic receptor agonist as treatment for patients with open angle glaucoma and high intraocular pressure. The objective of this study was to formulate an ophthalmic ion-sensitive in situ gel (ISG) of BRT to increase the retention time of the drug and its bioavailability. The optimum formulation of 2 mg/mL BRT-ISG was obtained with 0.45% gellan gum as the gel matrix. In vitro release results showed that the water-soluble drug bromonidine tartrate in ocular in situ gels exhibited a high burst effect and fast release in solution. The results of dialysis membrane permeation showed that there was a significant difference between the commercially available and BRT-ISG groups after 45 min. The results of the pre-corneal retention study indicated that gellan gum can effectively prolong ocular surface retention. Preliminary stability results showed that it should be stored in a cool and dark place, and the formulation under long-term preservation can be basically stable. The pharmacokinetic study of the BRT-ISG in the anterior chamber of the rabbit eye was studied by microdialysis technique, and microdialysis samples were analyzed by LC-MS/MS. The pharmacokinetic study showed that the BRT-ISG reached Cmax (8.16 mg/L) at 93 min after administration, which was 2.7 times that of the BRT eye drops, and the AUC(0-t) (1397.08 mg·min/L) was 3.4 times that of the BRT eye drops. The optimal prescription can prolong the retention time of BRT in front of the cornea and significantly improve the bioavailability of BRT in the eye. Combined with the results of in vitro release, permeation and pre-corneal retention studies, the improvement of BRT-ISG bioavailability in rabbit eyes was found to be mainly due to the retention effect after the mixture of ISG and tears.

Current Advances in Nano-Based and Polymeric Stimuli-Responsive Drug Delivery Targeting the Ocular Microenvironment: A Review and Envisaged Future Perspectives

Optimal vision remains one of the most essential elements of the sensory system continuously threatened by many ocular pathologies. Various pharmacological agents possess the potential to effectively treat these ophthalmic conditions; however, the use and efficacy of conventional ophthalmic formulations is hindered by ocular anatomical barriers. Recent novel designs of ophthalmic drug delivery systems (DDS) using nanotechnology show promising prospects, and ophthalmic formulations based on nanotechnology are currently being investigated due to their potential to bypass these barriers to ensure successful ocular drug delivery. More recently, stimuli-responsive nano drug carriers have gained more attention based on their great potential to effectively treat and alleviate many ocular diseases. The attraction is based on their biocompatibility and biodegradability, unique secondary conformations, varying functionalities, and, especially, the stimuli-enhanced therapeutic efficacy and reduced side effects. This review introduces the design and fabrication of stimuli-responsive nano drug carriers, including those that are responsive to endogenous stimuli, viz., pH, reduction, reactive oxygen species, adenosine triphosphate, and enzymes or exogenous stimuli such as light, magnetic field or temperature, which are biologically related or applicable in clinical settings. Furthermore, the paper discusses the applications and prospects of these stimuli-responsive nano drug carriers that are capable of overcoming the biological barriers of ocular disease alleviation and/or treatment for in vivo administration. There remains a great need to accelerate the development of stimuli-responsive nano drug carriers for clinical transition and applications in the treatment of ocular diseases and possible extrapolation to other topical applications such as ungual or otic drug delivery.

Temperature-Ion-pH Triple Responsive Gellan Gum as In Situ Hydrogel for Long-Acting Cancer Treatment

Background: Promising cancer chemotherapy requires the development of suitable drug delivery systems (DDSs). Previous research has indicated that a hydrogel is a powerful DDS for tumor therapy and holds great potential to offer a feasible method for cancer management. Methods: In this study, glutathione-gellan gum conjugate (GSH-GG) was synthesized through chemical reaction. Doxorubicin hydrochloride (DOX) was loaded into GSH-GG to accomplish DOX-loaded GSH-GG. The properties, injectability, drug release, and in vitro and in vivo anticancer effects of DOX-loaded GSH-GG were tested. Results: DOX-loaded GSH-GG showed a temperature-ion dual responsive gelling property with good viscosity, strength, and injectability at an optimized gel concentration of 1.5%. In addition, lower drug release was found under acidic conditions, offering beneficial long-acting drug release in the tumor microenvironment. DOX-loaded GSH-GG presented selective action by exerting substantially higher cytotoxicity on cancer cells (4T1) than on normal epithelial cells (L929), signifying the potential of complete inhibition of tumor progression, without affecting the health quality of the subjects. Conclusions: GSH-GG can be applied as a responsive gelling material for delivering DOX for promising cancer therapy.

Mucoadhesive Marine Polysaccharides

Mucoadhesive polymers are of growing interest in the field of drug delivery due to their ability to interact with the body’s mucosa and increase the effectiveness of the drug. Excellent mucoadhesive performance is typically observed for polymers possessing charged groups or non-ionic functional groups capable of forming hydrogen bonds and electrostatic interactions with mucosal surfaces. Among mucoadhesive polymers, marine carbohydrate biopolymers have been attracting attention due to their biocompatibility and biodegradability, sample functional groups, strong water absorption and favorable physiochemical properties. Despite the large number of works devoted to mucoadhesive polymers, there are very few systematic studies on the influence of structural features of marine polysaccharides on mucoadhesive interactions. The purpose of this review is to characterize the mucoadhesive properties of marine carbohydrates with a focus on chitosan, carrageenan, alginate and their use in designing drug delivery systems. A wide variety of methods which have been used to characterize mucoadhesive properties of marine polysaccharides are presented in this review. Mucoadhesive drug delivery systems based on such polysaccharides are characterized by simplicity and ease of use in the form of tablets, gels and films through oral, buccal, transbuccal and local routes of administration.

Marine Polysaccharides in Tailor- Made Drug Delivery

Abstract:

Marine sources have attracted much interest as an emerging source of biomaterials in drug delivery applications. Amongst all other marine biopolymers, polysaccharides have been the mostly investigated class of biomaterials. The low cytotoxic behavior, in combination with the newly explored health benefits of marine polysaccharides has made it one of the prime research areas in the pharmaceutical and biomedical fields. In this review, we focused on all available marine polysaccharides, including their classification based on biological sources. The applications of several marine polysaccharides in recent years for tissue-specific novel drug delivery including gastrointestinal, brain tissue, transdermal, ocular, liver, and lung have also been discussed here. The abundant availability in nature, cost-effective extraction, and purification process along with a favorable biodegradable profile will encourage researchers to continue investigating marine polysaccharides for exploring newer applications in targeting specific delivery of therapeutics.

Dietary κ-carrageenan facilitates gut microbiota-mediated intestinal inflammation

The inflammatory effects of carrageenan (CGN), a ubiquitous food additive, remains controversial. Gut microbiota and intestinal homeostasis may be a breakthrough in resolving this controversy. Here we show that, κ-CGN did not cause significant inflammatory symptoms, but it did cause reduced bacteria-derived short-chain fatty acids (SCFAs) and decreased thickness of the mucus layer by altering microbiota composition. Administration of the pathogenic bacterium Citrobacter rodentium, further aggravated the inflammation and mucosal damage in the presence of κ-CGN. Mucus layer degradation and altered SCFA levels could be reproduced by fecal transplantation from κ-CGN-fed mice, but not from germ-free κ-CGN-fed mice. These symptoms could be partially repaired by administering probiotics. Our results suggest that κ-CGN may not be directly inflammatory, but it creates an environment that favors inflammation by perturbation of gut microbiota composition and then facilitates expansion of pathogens, and this effect may be partially reversed by the introduction of probiotics.

In Situ Liquid Crystal Gel as a Promising Strategy for Improving Ocular Administration of Dexamethasone: Preparation, Characterization, and Evaluation

The purpose of this study was to design an in situ liquid crystal gel (ISLG) as an ophthalmic drug delivery system for dexamethasone (DEX) to enhance its eye retention and ocular bioavailability. The in situ liquid crystal gels (ISLGs) were prepared using a phytantriol/PEG400/water (65:30:5, w/w) ternary system. Polarized light microscope (PLM), small-angle X-ray scattering (SAXS), and rheology analysis confirmed that the internal structure of the preparations was Pn3m cubic phase liquid crystal gels with pseudoplastic fluid properties. Meanwhile, in vitro release behavior of the preparations conforms to the Higuchi equation. Corneal penetration experiments showed that compared with DEX sodium phosphate eye drops, DEX-ISLGs(F2) produced a 5.45-fold increase in the P_app value, indicating a significant enhancement of corneal penetration. In addition, in vivo experiments have confirmed that the ISLGs have better biocompatibility and longer retention time in the cornea. Simultaneously, corneal hydration level, eye irritation experiments, and histological observations proved the safety of the preparations. Pharmacokinetic studies have shown that the ISLG could maintain the DEX concentration in aqueous humor for at least 12 h after administration, which significantly improves the bioavailability of the drug. Collectively, these results indicated that ISLG would be a potential drug carrier for the treatment of diabetic retinopathy (DR).

Stimuli-Responsive Polymers for Transdermal, Transmucosal and Ocular Drug Delivery

Despite their conventional and widespread use, oral and intravenous routes of drug administration face several limitations. In particular, orally administered drugs undergo enzymatic degradation in the gastrointestinal tract and first-pass metabolism in the liver, which tend to decrease their bioavailability. Intravenous infusions of medications are invasive, painful and stressful for patients and carry the risk of infections, tissue damage and other adverse reactions. In order to account for these disadvantages, alternative routes of drug delivery, such as transdermal, nasal, oromucosal, ocular and others, have been considered. Moreover, drug formulations have been modified in order to improve their storage stability, solubility, absorption and safety. Recently, stimuli-responsive polymers have been shown to achieve controlled release and enhance the bioavailability of multiple drugs. In this review, we discuss the most up-to-date use of stimuli-responsive materials in order to optimize the delivery of medications that are unstable to pH or undergo primary metabolism via transdermal, nasal, oromucosal and ocular routes. Release kinetics, diffusion parameters and permeation rate of the drug via the mucosa or skin are discussed as well.

λ-carrageenan exacerbates Citrobacter rodentium-induced infectious colitis in mice by targeting gut microbiota and intestinal barrier integrity

For nearly half a century, the scientific community has been unable to agree upon the safety profile of carrageenan (CGN), a ubiquitous food additive. Little is known about the mechanisms by which consumption of CGN aggravates the etiopathogenesis of murine colitis. However, analyses of gut microbiota and intestinal barrier integrity have provided a breakthrough in explaining the synergistic effect of CGN upon colitis. In Citrobacter rodentium-induced infectious murine colitis, inflammation and the clinical severity of gut tissue were aggravated in the presence of λ-CGN. Using fecal transplantation and germ-free mice experiments, we evaluated the role of intestinal microbiota on the pro-inflammatory effect of λ-CGN. Mice with high dietary λ-CGN consumption showed altered colonic microbiota composition that resulted in degradation of the colonic mucus layer, a raised fecal LPS level, and a decrease in the presence of bacterially derived short-chain fatty acids (SCFAs). Mucus layer defects and altered fecal LPS and SCFA levels could be reproduced in germ-free mice by fecal transplantation from CGN-H-fed mice, but not from germ-free CGN-H-fed mice. Our results confirm that λ-CGN may create an environment that favors inflammation by altering gut microbiota composition and gut bacterial metabolism. The present study provides evidence that the "gut microbiota-barrier axis" could be an alternative target for ameliorating the colitis promoting effect of λ-CGN.

Carrageenan gel beads for echinochrome inclusion: Influence of structural features of carrageenan

Carrageenan (CRG) and carrageenan/chitosan (CH) gel beads (CRG/CH) were prepared as a release delivery system for echinochrome A (Ech). According to spectral data, the Ech was dispersed in the polymer matrix, interacted with CRG, was not oxidised, and remained stable after encapsulation in CRG beads. Carrageenan beads containing Ech were coated with CH by layering. The influence of the structural features of CRG on the formation of beads and the beads morphology, swelling behaviour, mucoadhesive properties and drug release were evaluated. The polysaccharide matrices with Ech showed different swelling characteristics depending on the pH of the medium and the structure of the CRG used. The slow drug release from polysaccharide matrixes was observed for κ- and κ/β-CRG beads, that contained 3,6-anhydro-α-d-galactopyranose units and had high molecular weight. The obtained results showed the prospects of using polysaccharide beads to include Ech.

Gellan Gum Hydrogels Filled Edible Oil Microemulsion for Biomedical Materials: Phase Diagram, Mechanical Behavior, and In Vivo Studies

The demand for wound care products, especially advanced and active wound care products is huge. In this study, gellan gum (GG) and virgin coconut oil (VCO) were utilized to develop microemulsion-based hydrogel for wound dressing materials. A ternary phase diagram was constructed to obtain an optimized ratio of VCO, water, and surfactant to produce VCO microemulsion. The VCO microemulsion was incorporated into gellan gum (GG) hydrogel (GVCO) and their chemical interaction, mechanical performance, physical properties, and thermal behavior were examined. The stress-at-break (σ) and Young's modulus (YM) of GVCO hydrogel films were increased along with thermal behavior with the inclusion of VCO microemulsion. The swelling degree of GVCO hydrogel decreased as the VCO microemulsion increased and the water vapor transmission rate of GVCO hydrogels was comparable to commercial dressing in the range of 332-391 g m^-2 d^-1. The qualitative antibacterial activities do not show any inhibition against Gram-negative (Escherichia coli and Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus and Bacillus subtilis) bacteria. In vivo studies on Sprague-Dawley rats show the wound contraction of GVCO hydrogel is best (95 ± 2%) after the 14th day compared to a commercial dressing of Smith and Nephew Opsite post-op waterproof dressing, and this result is supported by the ultrasound images of wound skin and histological evaluation of the wound. The findings suggest that GVCO hydrogel has the potential to be developed as a biomedical material.

The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye

The prevalence of chronic fundus diseases is increasing with the aging of the general population. The treatment of these intraocular diseases relies on invasive drug delivery because of the globular structure and multiple barriers of the eye. Frequent intraocular injections bring heavy burdens to the medical care system and patients. The use of topical drugs to treat retinal diseases has always been an attractive solution. The fast development of new materials and technologies brings the possibility to develop innovative topical formulations. This article reviews anatomical and physiological barriers of the eye which affect the bioavailability of topical drugs. In addition, we summarize innovative topical formulations which enhance the permeability of drugs through the ocular surface and/or extend the drug retention time in the eye. This article also reviews the differences of eyes between different laboratory animals to address the translational challenges of preclinical models. The fast development of in vitro eye models may provide more tools to increase the clinical translationality of topical formulations for intraocular diseases. Clinical successes of topical formulations rely on continuous and collaborative efforts between different disciplines.

Formulation development, optimization, and in vitro assessment of thermoresponsive ophthalmic pluronic F127-chitosan in situ tacrolimus gel

To overcome problems associated with topical delivery of tacrolimus (TCS), a thermoresponsive in situ gel system containing pluronic F127 (PL), and chitosan (CS) was developed, to enhance the precorneal retention, and to sustain the release of the drug. The PL-CS in situ gel was optimized using a 2-factor-3-level central composite experimental design by selecting the concentration of PL and CS as independent variables while gelation time, gelation temperature, and spreadability as dependent variables. The optimized formulation was developed using 22.5 g PL and 0.3 g CS, gels at 33.6 °C, in 22.93 s, and showed the spreadability of 6.2 cm. In vitro studies conducted for the optimized gel revealed the sustained release of TCS (81.73% in 4 h) and improved corneal permeation (74.13% in 4 h), compared with TCS solution. The mechanism of release of TCS followed the Higuchi model with Fickian diffusion transport. Further, histopathology and HET-CAM studies revealed that the developed gel was non-irritating and safe for ocular administration.

Intellective and stimuli-responsive drug delivery systems in eyes

Stimuli-responsive drug delivery systems have attracted widespread attention in recent years since they can control drug release in a spatiotemporal manner and can achieve tunable drug release according to patient's physiological or pathological condition. In this review, we briefly introduce the drug delivery barriers and drug delivery systems in the anterior and posterior segment of eyes, and collect the recent advances in stimuli-responsive drug delivery systems in eyes for controlled drug release in response to exogenous stimuli (ultrasound, magnetic stimulus, electrical stimulus, and light) or endogenous stimuli (enzyme, active oxygen species, temperature, ions, and pH). In addition, the design and mechanisms of the stimuli-responsive drug delivery systems have been summarized in this review, and the advantages and limitations are also briefly discussed.

Potential of Stimuli-Responsive In Situ Gel System for Sustained Ocular Drug Delivery: Recent Progress and Contemporary Research

Eyesight is one of the most well-deserved blessings, amid all the five senses in the human body. It captures the raw signals from the outside world to create detailed visual images, granting the ability to witness and gain knowledge about the world. Eyes are exposed directly to the external environment; they are susceptible to the vicissitudes of diseases. The World Health Organization has predicted that the number of individuals affected by eye diseases will rise enormously in the next decades. However, the physical barriers of the eyes and the problems associated with conventional ocular formulations are significant challenges in ophthalmic drug development. This has generated the demand for a sustained ocular drug delivery system, which serves to deliver effective drug concentration at a reduced frequency for consistent therapeutic effect and better patient treatment adherence. Recent advancement in pharmaceutical dosage design has demonstrated that a stimuli-responsive in situ gel system exhibits the favorable characteristics for providing sustained ocular drug delivery and enhanced ocular bioavailability. Stimuli-responsive in situ gels undergo a phase transition (solution-gelation) in response to the ocular environmental temperature, pH, and ions. These stimuli transform the formulation into a gel at the cul de sac to overcome the shortcomings of conventional eye drops, such as rapid nasolacrimal drainage and short contact time with the ocular surface This review highlights the recent successful research outcomes of stimuli-responsive in situ gelling systems in treating in vivo models with glaucoma and various ocular infections. Additionally, it also presents the mechanism, recent development, and safety considerations of stimuli-sensitive in situ gel as the potential sustained ocular delivery system for treating common eye disorders.

In situ forming and mucoadhesive ophthalmic voriconazole/HPβCD hydrogels for the treatment of fungal keratitis

Fungal keratitis is a severe infectious corneal disease. At present, no voriconazole ophthalmic formulations are approved by the FDA or EMA. This lack of therapeutic options leads to the reformulation of intravenous voriconazole preparations (VFEND®) by the hospital pharmacy departments to prepare the appropriate ophthalmic formulations (pharmacy compounding). However, the limited residence time of these formulations leads to an intensive treatment posology that may increase the occurrence of side effects. In the present study, two different hydrogels were developed and characterized in order to improve the voriconazole's ophthalmic solubility, permanence, and security. Voriconazole-cyclodextrin (HPβCD or HPɣCD) inclusion complexes in aqueous solutions were characterized by NMR and molecular modeling. Complexes were formed by encapsulation of voriconazole into the cyclodextrin's internal cavity which considerably increases its water solubility. Ocular safety was proven by ocular irritation studies. Permeability studies suggest both hydrogels have good corneal permeability. Furthermore, in vivo ocular permanence study by PET/CT showed a longer permanence time on the ocular surface (t_1/2 = 58.91 ± 13.4 min and 96.28 ± 49.11 min for VZHAH and VZISH 0.65 respectively) compared to the voriconazole control formulation (VFEND® t_1/2 = 32.27 ± 15.56 min). Results suggest these formulations are a good alternative for the treatment of fungal keratitis.

Recent Research in Ocular Cystinosis: Drug Delivery Systems, Cysteamine Detection Methods and Future Perspectives

Cystinosis is a rare genetic disorder characterized by the accumulation of cystine crystals in different tissues and organs. Although renal damage prevails during initial stages, the deposition of cystine crystals in the cornea causes severe ocular manifestations. At present, cysteamine is the only topical effective treatment for ocular cystinosis. The lack of investment by the pharmaceutical industry, together with the limited stability of cysteamine, make it available only as two marketed presentations (Cystaran® and Cystadrops®) and as compounding formulations prepared in pharmacy departments. Even so, new drug delivery systems (DDSs) need to be developed, allowing more comfortable dosage schedules that favor patient adherence. In the last decades, different research groups have focused on the development of hydrogels, nanowafers and contact lenses, allowing a sustained cysteamine release. In parallel, different determination methods and strategies to increase the stability of the formulations have also been developed. This comprehensive review aims to compile all the challenges and advances related to new cysteamine DDSs, analytical determination methods, and possible future therapeutic alternatives for treating cystinosis.

In Situ Gelling Ophthalmic Drug Delivery System for the Optimization of Diagnostic and Preoperative Mydriasis: In Vitro Drug Release, Cytotoxicity and Mydriasis Pharmacodynamics

Mydriasis is required prior to many eye examinations and ophthalmic surgeries. Nowadays, phenylephrine hydrochloride (PHE) and tropicamide (TPC) are extensively used to induce mydriasis. Several pharmaceutic dosage forms of these two active ingredients have been described. However, no optimal therapeutic strategy has reached the market. The present work focuses on the formulation and evaluation of a mucoadhesive ion-activated in situ gelling delivery system based on gellan gum and hydroxyethylcellulose (HEC) for the delivery of phenylephrine and tropicamide. First, in vitro drug release was studied to assess appropriate sustained drug delivery on the ocular surface region. Drug release mechanisms were explored and explained using mathematical modeling. Then, in situ gelling delivery systems were visualized using scanning electron microscopy illustrating the drug release phenomena involved. Afterward, cytotoxicity of the developed formulations was studied and compared with those of commercially available eye drops. Human epithelial corneal cells were used. Finally, mydriasis intensity and kinetic was investigated in vivo. Mydriasis pharmacodynamics was studied by non-invasive optical imaging on vigilant rabbits, allowing eye blinking and nasolacrimal drainage to occur physiologically. In situ gelling delivery systems mydriasis profiles exhibited a significant increase of intensity and duration compared with those of conventional eye drops. Efficient mydriasis was achieved following the administration of a single drop of in situ gel reducing the required amount of administered active ingredients by four- to eight-fold compared with classic eye drop regimen.

3D printing of cell-laden electroconductive bioinks for tissue engineering applications

Bioprinting is an emerging powerful fabrication method, which enables the rapid assembly of 3D bioconstructs with dispensing cell-laden bioinks in pre-designed locations.

Electrospun nanofibers - A promising solid in-situ gelling alternative for ocular drug delivery

A serious problem of the treatment of eye diseases is the very short residence time of the drug. The majority of the drug is cleared within few seconds due to the poor capability of the eye to accommodate additional liquids. We developed a new ocular drug delivery system, which is applied in dry form and forms immediately a gel after administration. The system is based on gellan gum/pullulan electrospun nanofibers. The rheological behavior of the spinning solution was investigated followed by further characterization of the in situ formed gel. Three-dimensional X-ray imaging with nanometric resolution (nano-CT) and electron scanning microscopy were used for a detailed characterization of the diameter and alignment of the fibers. A high porosity (87.5 ± 0.5%) and pore interconnectivity (99%) was found. To ensure a good fit to the eye anatomy, the prepared fibers were shaped into curved geometries. Additionally, a new innovative moistening chamber for the in vitro determination of the ocular residence time in porcine eyes was developed which mimics the tear turnover. A clear prolongation of the fluorescein residence time compared to conventional eye drops was achieved with the application of the curved nanofiber in situ gelling mat. In summary, the developed in situ gelling system with adapted geometry is a promising alternative system for ocular drug delivery.

Novel in situ gelling ophthalmic drug delivery system based on gellan gum and hydroxyethylcellulose: Innovative rheological characterization, in vitro and in vivo evidence of a sustained precorneal retention time

Achieving drug delivery at the ocular level encounters many challenges and obstacles. In situ gelling delivery systems are now widely used for topical ocular administration and recognized as a promising strategy to improve the treatment of a wide range of ocular diseases. The present work describes the formulation and evaluation of a mucoadhesive and ion-activated in situ gelling delivery system based on gellan gum and hydroxyethylcellulose for the delivery of phenylephrine and tropicamide. First, physico-chemical characteristics were assessed to ensure suitable properties regarding ocular administration. Then, rheological properties such as viscosity and gelation capacity were determined. Gelation capacity of the formulations and the effect of hydroxyethylcellulose on viscosity were demonstrated. A new rheological method was developed to assess the gel resistance under simulated eye blinking. Afterward, mucoadhesion was evaluated using tensile strength test and rheological synergism method in both rotational and oscillatory mode allowing mucoadhesive properties of hydroxyethylcellulose to be point out. Finally, residence time on the ocular surface was investigated in vivo, using cyanine 5.5 dye as a fluorescent marker entrapped in the in situ gelling delivery systems. Residence performance was studied by non-invasive optical imaging on vigilant rabbits, allowing eye blinking and nasolacrimal drainage to occur physiologically. Fluorescence intensity profiles pointed out a prolonged residence time on the ocular surface region for the developed formulations compared to conventional eye drops, suggesting in vitro / in vivo correlations between rheological properties and in vivo residence performances.

Hydrogel-based ocular drug delivery systems: Emerging fabrication strategies, applications, and bench-to-bedside manufacturing considerations

The physiological barriers of the eye pose challenges to the delivery of the array of therapeutics for ocular diseases. Hydrogels have been widely explored for medical applications and introduce possible solutions to overcoming the medication challenges of the ocular environment. While the innovations in drug encapsulation and release mechanisms, biocompatibility, and treatment duration have become highly sophisticated, the challenge of widespread application of hydrogel formulations in the clinic is still apparent. This article reviews the latest hydrogel formulations and their associated chemistries for use in ocular therapies, spanning from external anterior to internal posterior regions of the eye in order to evaluate the state of recent research. This article discusses the utility of hydrogels in soft contact lens, wound dressings, intraocular lens, vitreous substitutes, vitreous drug release hydrogels, and cell-based therapies for regeneration. Additional focus is placed on the pre-formulation, formulation, and manufacturing considerations of the hydrogels based on individual components (polymer chains, linkers, and therapeutics), final hydrogel product, and required preparations for clinical/commercial applications, respectively.

Ocular Biodistribution Studies using Molecular Imaging

Classical methodologies used in ocular pharmacokinetics studies have difficulties to obtain information about topical and intraocular distribution and clearance of drugs and formulations. This is associated with multiple factors related to ophthalmic physiology, as well as the complexity and invasiveness intrinsic to the sampling. Molecular imaging is a new diagnostic discipline for in vivo imaging, which is emerging and spreading rapidly. Recent developments in molecular imaging techniques, such as positron emission tomography (PET), single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI), allow obtaining reliable pharmacokinetic data, which can be translated into improving the permanence of the ophthalmic drugs in its action site, leading to dosage optimisation. They can be used to study either topical or intraocular administration. With these techniques it is possible to obtain real-time visualisation, localisation, characterisation and quantification of the compounds after their administration, all in a reliable, safe and non-invasive way. None of these novel techniques presents simultaneously high sensitivity and specificity, but it is possible to study biological procedures with the information provided when the techniques are combined. With the results obtained, it is possible to assume that molecular imaging techniques are postulated as a resource with great potential for the research and development of new drugs and ophthalmic delivery systems.

A Novel Phytantriol-Based Lyotropic Liquid Crystalline Gel for Efficient Ophthalmic Delivery of Pilocarpine Nitrate

The purpose of this paper was to investigate the potential of liquid crystalline (LC) gels for ophthalmic delivery, so as to enhance the bioavailability of pilocarpine nitrate (PN). The gels were prepared by a vortex method using phytantriol and water (in the ratio of 73:27 w/w). Their inner structures were confirmed by crossed polarized light microscopy, small-angle X-ray scattering, attenuated total reflectance-Fourier transform infrared spectrum, and rheology. The in vitro release studies revealed that PN could keep sustained release from the gels over a period of 12 h. The ex vivo apparent permeability coefficient of the gels demonstrated a 3.83-folds (P < 0.05) increase compared with that of eye drops. The corneal hydration levels of the gel maintained in the normal range of 79.46 ± 2.82%, hinting that the gel could be considered non-damaging and safe to the eyes. Furthermore, in vivo residence time evaluation suggested that a better retention performance of LC gel was observed in rabbit's eyes compared to eye drops. In vivo ocular irritation study indicated that LC gel was nonirritant and might be suitable for various eye applications. In conclusion, LC gels might represent a potential ophthalmic delivery strategy to overcome the limitations of eye drops.

Carrageenan based hydrogels for drug delivery, tissue engineering and wound healing

Carrageenan is a class of naturally occurring sulphated polysaccharides, which is currently a promising candidate in tissue engineering and regenerative medicine as it resemblances native glycosaminoglycans. From pharmaceutical drug formulations to tissue engineered scaffolds, carrageenan has broad range of applications. Here we provide an overview of developing various forms of carrageenan based hydrogels. We focus on how these fabrication processes has an effect on physiochemical properties of the hydrogel. We outline the application of these hydrogels not only pertaining to sustained drug release but also their application in bone and cartilage tissue engineering as well as in wound healing and antimicrobial formulations. Administration of these hydrogels through various routes for drug delivery applications has been critically reviewed. Finally, we conclude by summarizing the current and future outlook that promotes the seaweed-derived polysaccharide as versatile, promising biomaterial for a variety of bioengineering applications.

Biopolymer-based strategies in the design of smart medical devices and artificial organs

Advances in regenerative medicine and in modern biomedical therapies are fast evolving and set goals causing an upheaval in the field of materials science. This review discusses recent developments involving the use of biopolymers as smart materials, in terms of material properties and stimulus-responsive behavior, in the presence of environmental physico-chemical changes. An overview on the transformations that can be triggered in natural-based polymeric systems (sol-gel transition, polymer relaxation, cross-linking, and swelling) is presented, with specific focus on the benefits these materials can provide in biomedical applications.

Tripolymeric Corneal Coating Gel Versus Balanced Salt Solution Irrigation During Cataract Surgery: A Retrospective Analysis

PURPOSE

To compare the protective properties and ease of manipulation during cataract surgery of corneal coating with a gel (eyeDRO; AL.CHI.MI.A. S.R.L, Italy) and corneal irrigation with balanced salt solution (BSS).

METHODS

We analyzed the data of 51 patients receiving either eyeDRO or BSS during routine cataract surgery performed within a 20-day period in 2016. The selected parameters were intraoperative clarity and ease of manipulation; postoperative epithelial integrity; and patient discomfort.

RESULTS

Compared with BSS irrigation, eyeDRO coating significantly increased intraoperative clarity and ease of manipulation (P < 0.01). Single application was required in eyeDRO-treated eyes, whereas BSS was applied 5.3 ± 0.4 times on average (P < 0.01). Two hours postoperatively, a normal epithelium was observed in 90.0% and 60.0% of eyeDRO-coated and BSS-irrigated eyes, respectively; punctate epithelial damage was observed in 9.7% and 40.0% (P < 0.05) of eyeDRO-coated and BSS-irrigated eyes, respectively; eye irritation and foreign body sensation were experienced by 13.0% and 37.0% of eyeDRO-treated patients and by 65.0% and 100% of BSS-treated patients, respectively (P < 0.01). Twenty-four hours postoperatively, 80.0% of BSS-treated patients versus 19.0% of eyeDRO-treated patients still experienced foreign body sensation (P < 0.01).

CONCLUSIONS

EyeDRO coating was shown to be a safer and more effective option than BSS irrigation in cataract surgery because single application provided optimal hydration and intraoperative clarity during the entire surgery, better preserved the corneal epithelium, and offered postoperative comfort to the patient.

Ophthalmic Econazole Hydrogels for the Treatment of Fungal Keratitis

Econazole is a feasible alternative treatment in the management of fungal keratitis. Nevertheless, its low water solubility is considered the main limitation to the incorporation into ophthalmic formulations. In this work, econazole nitrate is solubilized by using cyclodextrins to achieve an optimum therapeutic concentration. Phase solubility diagrams suggest α-cyclodextrin as the most effective cyclodextrin and later the inclusion complex formed with this one was characterized in solution by 1D, 2D-NMR, and molecular modeling. Econazole-α-cyclodextrin inclusion complex was included in 2 types of ocular hydrogels: a natural polysaccharides ion-sensitive hydrogel and a hyaluronic acid hydrogel. Both of them show no ocular irritation in the hen's egg test on chorioallantoic membrane assay and a controlled econazole release over time. Permeability studies suggest that hydrogels do not modify the econazole nitrate permeability through bovine cornea in comparison with an econazole-α-cyclodextrin inclusion complex solution. Finally, ocular biopermanence studies performed using positron emission tomography show these hydrogels present a high retention time on the eye. Results suggest the developed formulations have a high potential as vehicles for the econazole topical ocular administration as fungal keratitis treatment.

A novel ion-activated in situ gelling ophthalmic delivery system based on κ-carrageenan for acyclovir

The aim of this study was to prepare and evaluate ion-activated in situ gel ophthalmic drug delivery system based on κ-carrageenan (KC), using acyclovir as a model drug, hydroxypropyl methylcellulose (HPMC) as the viscosity agent and hydroxypropyl-β-cyclodextrin (HP-β-CD) as the penetration enhancer. The two ternary phase diagrams exhibited the effect of K⁺ and Ca²⁺ on the sol-to-gel transition, which turned out that KC was more sensitive to K⁺. The optimal ophthalmic matrix (prepared from KC and HPMC) was optimized with in vitro drug release test. The apparent permeability coefficient of acyclovir under 2% HP-β-CD was found to have dramatically increased (2.16-ploid) than that of conventional eye drops (p < .05). The ion-activated in situ gel based on KC significantly delayed drug release and its bioavailability could be improved in comparison with the conventional eye drops. Hence, it has the potential to be a novel kind of ocular drug delivery system.

Recent trends on gellan gum blends with natural and synthetic polymers: A review

Gellan gum (GG), a linear negatively charged exopolysaccharide,is biodegradable and non-toxic in nature. It produces hard and translucent gel in the presence of metallic ions which is stable at low pH. However, GG has poor mechanical strength, poor stability in physiological conditions, high gelling temperature and small temperature window.Therefore,it is blended with different polymers such as agar, chitosan, cellulose, sodium alginate, starch, pectin, polyanaline, pullulan, polyvinyl chloride, and xanthan gum. In this article, a comprehensive overview of combination of GG with natural and synthetic polymers/compounds and their applications in biomedical field involving drug delivery system, insulin delivery, wound healing and gene therapy, is presented. It also describes the utilization of GG based materials in food and petroleum industry. All the technical scientific issues have been addressed; highlighting the recent advancement.