In vivo eye surface residence determination by high-resolution scintigraphy of a novel ion-sensitive hydrogel based on gellan gum and kappa-carrageenan

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.

Recent opportunities and application of gellan gum based drug delivery system for intranasal route

OBJECTIVES

In the recent years, in-situ hydrogel based on gellan gum has been investigated for delivery of various drug molecules particularly to treat neurological disorders via intranasal route. The major objective of the present manuscript is to review the recent research studies exploring gellan gum as ionic triggered in-situ gel for intranasal administration to enhance absorption of drugs and to increase their therapeutic efficacy.

METHODS

This review include literature from 1982 to 2023 and were collected from various scientific electronic databases like Scopus, PubMed and Google Scholar to review source, chemistry, ionotropic gelation mechanism, and recent research studies for gellan gum based in-situ hydrogel for intransasl administration.Keywords such as gellan gum, in-situ hydrogel, intranasal administration and brain targeting were used to search literature. The present review included the research studies which explored gellan gum based in-situ gel for intranasal drug delivery.

RESULTS

The findings have shown enhanced biavailability of various drugs upon intranasal administration using gellan-gum based in-situ hydrogel.Moreover, the review indicated that intranasal administration of in-situ hydrogel facilitate to overcome blood brain barrier effectively. Hence, significantly higher drug concentration was found to be achieved in brain tissues upon intranasal administration than that of other routes like oral and intravenous.

CONCLUSION

The present work conducted a comprehensive review for gellan gum based in-situ hydrogel particularly for intransal administration to overcome BBB. The study concluded that gellan gum based in-situ hydrogel could be potential promising delivery system for intranasal administration to improve bioavailability and efficacy of drugs specifically to treat neurological disorders.

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.

Aflibercept Loaded Eye-Drop Hydrogel Mediated with Cell-Penetrating Peptide for Corneal Neovascularization Treatment

Corneal neovascularization (CoNV) is a major cause of visual impairment worldwide. Currently, available treatment options have limited efficacy and are associated with adverse effects due to biological barriers and clearance mechanisms. To address this challenge, a novel topical delivery system is developed-Gel 2_1&Eylea-an aflibercept-loaded eye-drop hydrogel mediated with cell-penetrating peptide 1. Gel 2_1&Eylea demonstrates superior membrane permeability, increased stability, and prolonged drug retention time on the ocular surface, and thus may improve drug efficacy. In a rabbit CoNV model, Gel 2_1&Eylea significantly reduces the density of neovascularization with no adverse effects on normal corneoscleral limbal vessels, demonstrating high efficacy and biocompatibility. This work identifies a promising treatment for CoNV which has the potential to benefit other ocular neovascular diseases.

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.

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.

Hydrogels as Emerging Materials for Cornea Wound Healing

Hydrogel biomaterials have many favorable characteristics including tuneable mechanical behavior, cytocompatibility, optical properties suitable for regeneration and restoration of the damaged cornea tissue. The cornea is a tissue susceptible to various injuries and traumas with a complicated healing cascade, in which conserving its transparency and integrity is critical. Accordingly, the hydrogels' known properties along with the stimulation of nerve and cell regeneration make them ideal scaffold for corneal tissue engineering. Hydrogels have been used extensively in clinical applications for the repair and replacement of diseased organs. The development and optimizing of novel hydrogels to repair/replace corneal injuries have been the main focus of researches within the last decade. This research aims to critically review in vitro, preclinical, as well as clinical trial studies related to corneal wound healing using hydrogels in the past 10 years, as this is considered as an emerging technology for corneal treatment. Several unique modifications of hydrogels with smart behaviors have undergone early phase clinical trials and showed promising outcomes. Financially, this considers a multibillion dollars industry and with huge interest from medical devices as well as pharmaceutical industries with several products may emerge within the next five years.

Biological Role of Gellan Gum in Improving Scaffold Drug Delivery, Cell Adhesion Properties for Tissue Engineering Applications

Over the past few decades, gellan gum (GG) has attracted substantial research interest in several fields including biomedical and clinical applications. The GG has highly versatile properties like easy bio-fabrication, tunable mechanical, cell adhesion, biocompatibility, biodegradability, drug delivery, and is easy to functionalize. These properties have put forth GG as a promising material in tissue engineering and regenerative medicine fields. Nevertheless, GG alone has poor mechanical strength, stability, and a high gelling temperature in physiological conditions. However, GG physiochemical properties can be enhanced by blending them with other polymers like chitosan, agar, sodium alginate, starch, cellulose, pullulan, polyvinyl chloride, xanthan gum, and other nanomaterials, like gold, silver, or composites. In this review article, we discuss the comprehensive overview and different strategies for the preparation of GG based biomaterial, hydrogels, and scaffolds for drug delivery, wound healing, antimicrobial activity, and cell adhesion. In addition, we have given special attention to tissue engineering applications of GG, which can be combined with another natural, synthetic polymers and nanoparticles, and other composites materials. Overall, this review article clearly presents a summary of the recent advances in research studies on GG for different biomedical applications.

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.

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.

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.

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.

Tailored nanostructured platforms for boosting transcorneal permeation: Box-Behnken statistical optimization, comprehensive in vitro, ex vivo and in vivo characterization

Ocular drug delivery systems suffer from rapid drainage, intractable corneal permeation and short dosing intervals. Transcorneal drug permeation could increase the drug availability and efficiency in the aqueous humor. The aim of this study was to develop and optimize nanostructured formulations to provide accurate doses, long contact time and enhanced drug permeation. Nanovesicles were designed based on Box-Behnken model and prepared using the thin film hydration technique. The formed nanodispersions were evaluated by measuring the particle size, polydispersity index, zeta potential, entrapment efficiency and gelation temperature. The obtained desirability values were utilized to develop an optimized nanostructured in situ gel and insert. The optimized formulations were imaged by transmission and scanning electron microscopes. In addition, rheological characters, in vitro drug diffusion, ex vivo and in vivo permeation and safety of the optimized formulation were investigated. The optimized insert formulation was found to have a relatively lower viscosity, higher diffusion, ex vivo and in vivo permeation, when compared to the optimized in situ gel. So, the lyophilized nanostructured insert could be considered as a promising carrier and transporter for drugs across the cornea with high biocompatibility and effectiveness.

Polymeric Hydrogels as Technology Platform for Drug Delivery Applications

Hydrogels have become key players in the field of drug delivery owing to their great versatility in terms of composition and adjustability to various administration routes, from parenteral (e.g., intravenous) to non-parenteral (e.g., oral, topical) ones. In addition, based on the envisioned application, the design of bioadhesive or mucoadhesive hydrogels with prolonged residence time in the administration site may be beneficial. For example, hydrogels are used as wound dressings and patches for local and systemic therapy. In a similar way, they can be applied in the vaginal tract for local treatment or in the nasal cavity for a similar goal or, conversely, to target the central nervous system by the nose-to-brain pathway. Overall, hydrogels have demonstrated outstanding capabilities to ensure patient compliance, while achieving long-term therapeutic effects. The present work overviews the most relevant and recent applications of hydrogels in drug delivery with special emphasis on mucosal routes.