Development of a Mucoadhesive and In Situ Gelling Formulation Based on κ-Carrageenan for Application on Oral Mucosa and Esophagus Walls. I. A Functional In Vitro Characterization

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.

Polymeric in situ forming depots for long-acting drug delivery systems

Polymeric in situ forming depots have emerged as highly promising drug delivery systems for long-acting applications. Their effectiveness is attributed to essential characteristics such as biocompatibility, biodegradability, and the ability to form a stable gel or solid upon injection. Moreover, they provide added versatility by complementing existing polymeric drug delivery systems like micro- and nanoparticles. The formulation's low viscosity facilitates manufacturing unit operations and enhances delivery efficiency, as it can be easily administered via hypodermic needles. The release mechanism of drugs from these systems can be predetermined using various functional polymers. To enable unique depot design, numerous strategies involving physiological and chemical stimuli have been explored. Important assessment criteria for in situ forming depots include biocompatibility, gel strength and syringeability, texture, biodegradation, release profile, and sterility. This review focuses on the fabrication approaches, key evaluation parameters, and pharmaceutical applications of in situ forming depots, considering perspectives from academia and industry. Additionally, insights about the future prospects of this technology are discussed.

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.

Current Status of Mucoadhesive Gel Systems for Buccal Drug Delivery

BACKGROUND

Buccal drug delivery is a fascinating research field. Gel-based formulations present potent characteristics as buccal systems since they have great physicochemical properties.

METHODS

Among the various gels, in situ gels are viscous colloidal systems consisting of polymers; when physiological conditions change (pH, temperature, ion activation), they are transformed into the gel phase. These systems can improve bioavailability. Other systems, such as nanogels or emulgels can also be applied for buccal delivery with promising results. Polymeric gel-based systems can be produced by natural, semisynthetic, and synthetic polymers. Their main advantage is that the active molecules can be released in a sustained and controllable manner. Several gels based on chitosan are produced for the entrapment of drugs demonstrating efficient retention time and bioavailability due to chitosan mucoadhesion. Besides polysaccharides, poloxamers and carbopol are also used in buccal gels due to their high swelling ability and reversed thermal gelation behavior.

RESULTS

Herein, the authors focused on the current development of mucoadhesive gel systems used in buccal drug delivery. After explaining buccal drug delivery and mucoadhesion, various studies with hydrogels, in situ gels, and nanogels were analyzed as buccal gel systems. Various mucoadhesive gel studies with mucoadhesive polymers have been studied and summarized. This review is presented as valuable guidance to scientists in formulating buccal mucoadhesive drug delivery systems.

CONCLUSION

This review aimed to assist researchers working on buccal drug delivery by summarizing buccal drug delivery, mucoadhesion, and buccal mucoadhesive gel systems recently found in the literature.

Promising Polymeric Drug Carriers for Local Delivery: The Case of in situ Gels

BACKGROUND

At present, the controlled local drug delivery is a very promising approach compared to systemic administration, since it mostly targets the affected tissue. In fact, various drug carriers for local delivery have been prepared with improved therapeutic efficacy.

OBJECTIVE

in situ polymer gels are drug delivery systems that not only present liquid characteristics before their administration in body, but once they are administered, form gels due to gelation. Their gelation mechanism is due to factors such as pH alteration, temperature change, ion activation or ultraviolet irradiation. in situ gels offer various advantages compared to conventional formulations due to their ability to release drugs in a sustainable and controllable manner. Most importantly, in situ gels can be used in local drug delivery applications for various diseases.

METHODS

This review includes the basic knowledge and theory of in situ gels as well as their various applications according to their administration route.

RESULTS

Various natural, semisynthetic, and synthetic polymers can produce in situ polymeric gels. For example, natural polysaccharides such as alginic acid, chitosan, gellan gum, carrageenan etc. have been utilized as in situ gels for topical delivery. Besides the polysaccharides, poloxamers, poly(Nisopropylacrylamide), poly(ethyleneoxide)/ (lactic-co-glycolic acid), and thermosensitive liposome systems can be applied as in situ gels. In most cases, in situ polymeric gels could be applied via various administration routes such as oral, vaginal, ocular, intranasal and injectable.

CONCLUSION

To conclude, it can be revealed that in situ gels could be a promising alternative carrier for both chronic and immediate diseases.

Recent Advances in the Development of In Situ Gelling Drug Delivery Systems for Non-Parenteral Administration Routes

In situ gelling drug delivery systems have gained enormous attention over the last decade. They are in a sol-state before administration, and they are capable of forming gels in response to different endogenous stimuli, such as temperature increase, pH change and the presence of ions. Such systems can be administered through different routes, to achieve local or systemic drug delivery and can also be successfully used as vehicles for drug-loaded nano- and microparticles. Natural, synthetic and/or semi-synthetic polymers with in situ gelling behavior can be used alone, or in combination, for the preparation of such systems; the association with mucoadhesive polymers is highly desirable in order to further prolong the residence time at the site of action/absorption. In situ gelling systems include also solid polymeric formulations, generally obtained by freeze-drying, which, after contact with biological fluids, undergo a fast hydration with the formation of a gel able to release the drug loaded in a controlled manner. This review provides an overview of the in situ gelling drug delivery systems developed in the last 10 years for non-parenteral administration routes, such as ocular, nasal, buccal, gastrointestinal, vaginal and intravesical ones, with a special focus on formulation composition, polymer gelation mechanism and in vitro release studies.

Evaluation of Eleview® Bioadhesive Properties and Cushion-Forming Ability

Submucosal injection is generally required for both endoscopic-mucosal resection (EMR) and submucosal dissection (ESD). SIC-8000 (Eleview®) is a new liquid composition in the form of a microemulsion for submucosal injection, approved by the Food and Drug Administration (FDA) 510(k) and Conformité Européene (CE) marked, containing a biocompatible polymer as a cushioning agent. The aim of this study was to evaluate Eleview®’s performance in terms of bioadhesive properties and cushion-forming ability. The bioadhesion was evaluated by measuring the interaction between Eleview® and the extracellular matrix (the main component of the submucosal layer) using the texture analyzer. To better comprehend the mechanism of action of Eleview® after submucosal injection, force of detachment and adhesion work were measured for the following formulations: Eleview®, Eleview® without poloxamer (functional polymer), poloxamer solution alone, normal saline, and MucoUp® (competing product on the Japanese market). The results obtained show the interaction between Eleview® and the extracellular matrix, highlighting the stronger bioadhesive properties of Eleview® compared with Eleview® without poloxamer, poloxamer solution alone, as well as normal saline and MucoUp®. The ability of Eleview® to form a consistent and long-lasting cushion in situ, once injected into the submucosal layer, was tested ex vivo on a porcine stomach. The results obtained show a better permanence in situ for the product compared with normal saline injection and to MucoUp® (t-test, p < 0.05).

An In Situ Gelling System for the Local Treatment of Inflammatory Bowel Disease (IBD). The Loading of Maqui (Aristotelia Chilensis) Berry Extract as an Antioxidant and Anti-Inflammatory Agent

The aim of the present work was the development of an innovative in situ gelling system, to be applied on the mucosa of the distal colon via rectal route. The system consisted of three polymers having different functions: gellan (GG), able to jellify in presence of ions; methylcellulose (MC), a thermosensitive polymer with a gelation temperature close to 50 °C; and hydroxypropylcellulose (HPC), a mucoadhesive polymer. The three polymers were able to act synergistically, increasing the permanence of the vehicle on the mucosa and forming a protective gel layer. A DoE approach, "simplex centroid mixture design," was used to identify the optimal quantitative composition of the vehicle. The response variables considered were: vehicle viscosity at room temperature; increase in vehicle viscosity on increasing temperature (from room to physiological value) and upon dilution with simulated colonic fluid (SCF); and viscoelastic behavior, thixotropic area, and mucoadhesion properties of the gel formed at 37 °C upon dilution in SCF. The optimized vehicle was loaded with maqui berry extract (MBE), known for its antioxidant and anti-inflammatory properties. MBE loading (0.5% w/w) into the vehicle improved rheological and mucoadhesive properties of the formulation. Both MBE and the optimized vehicle were not cytotoxic towards human fibroblasts and Caco-2 cells. Moreover, the optimized vehicle did not affect MBE antioxidant properties.

Development of a Mucoadhesive in Situ Gelling Formulation for the Delivery of Lactobacillus gasseri into Vaginal Cavity

Local administration of vaginal probiotics, especially lactobacilli, has been recently proposed as an effective prevention strategy against candidosis recurrences, which affect 40-50% of women. In this context, the aim of the present work was the development of a mucoadhesive in situ gelling formulation for the vaginal administration of Lactobacillus gasseri. Mixtures of poloxamer 407 (P407) and methylcellulose (MC), two thermosensitive polymers, were prepared and subjected to rheological analyses for the assessment of their sol/gel transition temperature. The association of P407 (15% w/w) with MC (1.5% w/w) produced an increase in gelation extent at 37 °C even after dilution in simulated vaginal fluid (SVF). The presence of 0.5% w/w pectin (PEC) produced a reduction of vehicle pH and viscosity at 25 °C that is the vehicle resistance to flow during administration. The presence of a low concentration of xyloglucan (XYL) (0.25% w/w) increases the mucoadhesive properties and the capability to gelify at 37 °C of the formulation after dilution with SVF. A three-component (P407/MC/PEC; 3cM) and a four-component (P407/MC/PEC/XYL; 4cM) mixture were selected as promising candidates for the delivery of L. gasseri to the vaginal cavity. They were able to preserve L. gasseri viability and were cytocompatible towards the HeLa cell line.

Development of a Mucoadhesive and an in Situ Gelling Formulation Based on κ-Carrageenan for Application on Oral Mucosa and Esophagus Walls. II. Loading of a Bioactive Hydroalcoholic Extract

The aim of the present work was to load a Hibiscus sabdariffa (HS) hydroalcoholic extract into in situ gelling formulations for the treatment of oral mucositis and esophagitis. Such formulations, selected as the most promising options in a previous work of ours, were composed by κ-carrageenan (κ-CG), a sulfated marine polymer able to gelify in presence of saliva ions, hydroxypropyl cellulose (HPC), used as mucoadhesive agent, and CaCl₂, salt able to enhance the interaction κ-CG/saliva ions. HS extract, which is rich in phytochemicals such as polyphenols, polysaccharides and organic acids, was selected due to its antioxidant and anti-inflammatory properties. For HS extraction, three different methodologies (maceration, Ultrasound Assisted Extraction (UAE) and Microwave Assisted Extraction (MAE)) were compared in terms of extraction yield and extract antioxidant activity, revealing that MAE was the best procedure. Rheological and mucoadhesive properties of HS-loaded formulations were investigated. Such formulations were characterized by a low viscosity at 25 °C, guaranteeing an easy administration, a proper in situ gelation behavior and marked elastic and mucoadhesive properties at 37 °C, functional to a protective action towards the damaged mucosa. Finally, the biocompatibility and the proliferative effect of HS-loaded formulations, as well as their antioxidant and anti-inflammatory properties, were proved in vitro on human dermal fibroblasts.