Highest Mucoadhesive Strength Research Articles

A review on topical ophthalmic drug delivery system: Reference to viscosity enhancer.

The eye is the most accessible site for topical drug delivery. Drug's ocular bioavailability is quite low when administered topically as eye drops. Viscosity enhancers are used to increase ocular bioavailability by extending the precorneal residence time of the drug at the ocular site. Cellulose, polyalcohol and polyacrylic acid are examples of hydrophilic viscosity enhancers. The addition of viscosity modifiers increases the amount of time the drug is in contact with the ocular surface. Several polysaccharides have been studied as excipients and viscosity boosters for ocular formulations, including cellulose derivatives such as chitosan (CS), xyloglucan and arabinogalactan (methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose (HPMC), and sodium carboxymethylcellulose). Viscosity-increasing substances reduce the surface tension, extend the corneal contact time, slow the drainage, and improve the bioavailability. Chitosan is a viscosity enhancer that was originally thought to open tight junction barrier cells in the epithelium. Chitosan thickens the medication solution and allows it to penetrate deeper. Alginate is an anionic polymer with carboxyl end groups that has the highest mucoadhesive strength and is used to improve penetration. Carboxymethylcellulose (CMC), a polysaccharide with a high molecular weight, is one of the most common viscous polymers used in artificial tears to achieve their longer ocular surface residence period. Hyaluronic acid (HA) is biocompatible and biodegradable in nature, and it is available in ocular sustained-release dose forms. A polymer known as xanthan gum is used to increase viscosity. At 0.2% concentration, carbomer forms a highly viscous gel.

Mucoadhesive Vaginal Tablets Containing Metronidazole: Screening of Optimal Natural Polymer in the Composition

(1) Background: The study aimed to compare the impact of various natural polymers–sodium alginate, acacia gum, carrageenan, guar gum, xanthan gum, and tragacanth on the formulation and the physical properties of mucoadhesive vaginal tablets containing metronidazole (167 mg/g). (2) Methods: The quality of the tablets prepared by direct compression was evaluated by pharmacopoeia tests (uniformity of mass, resistance to crushing, friability). Mucoadhesion of the tablets was characterized by swelling capacity and mucoadhesive strength, i.e., the force required to detach the tablet from the rabbit mucosa. In vitro drug release was performed by a modified dissolution method in paddle apparatus containing the simulated vaginal fluid (pH 4.5). Scanning electron microscopy observed morphological changes on the swollen tablets’ surface. (3) Results: Pharmacopoeia tests have shown that all prepared tablets met the requirements on quality. The highest mucoadhesive strength was noted in tablets containing guar and xanthan gum. The highest swelling capacity was possessed by tablets containing carrageenan. (4) Conclusions: Summarizing all tests’ results, sodium alginate can be considered the most suitable natural polymer in tablet formulation. The combination of polymers providing higher mucoadhesiveness and at the same time a prolonged release, e.g., xanthan or guar, together with sodium alginate, could also be of interest.

Gellan–thioglycolic acid conjugate: Synthesis, characterization and evaluation as mucoadhesive polymer

Gellan–thioglycollic acid conjugate was synthesized with the objective to improve its mucoadhesive properties. Synthesis of conjugate was confirmed by –SH stretch in the Fourier-transform infrared spectra at 2571cm−1. It was found to contain 13.92mM of thiol groups/g of the conjugate. Thiolation of gellan gum was found to slightly increase its degree of crystallinity and decrease its sensitivity to Ca2+-induced gelation. On screening of gellan–thioglycollic acid conjugate for ex-vivo ocular tolerance using hen's egg chorio-allantoic membrane test and for biocompatibility by resazurin assay on Vero-cells, it was found to be non-irritant and biocompatible. Metronidazole gels formulated using gellan thioglycollic acid conjugate as bioadhesive agent showed 1.82-fold higher mucoadhesive strength than the gels formulated using gellan gum. Further, the metronidazole gels containing gellan and gellan–thioglycollic conjugate released the drug following first-order and Higuchi's square-root release kinetics. In conclusion, gellan–thioglycollic acid conjugate is a promising bioadhesive excipient.

Evaluation of carboxymethyl gellan gum as a mucoadhesive polymer

The study was conducted to evaluate carboxymethyl gellan gum as bioadhesive polymer for drug delivery applications. Gellan gum was carboxymethylated by reacting it with monochloroacetic acid. Degree of carboxymethyl substitution was found to be 1.18. Further, carboxymethylation of gellan gum was found to increase its degree of crystallinity, surface roughness and diminish the cation-induced gelation. On comparative evaluation carboxymethyl gellan gum showed 2.71-fold higher mucoadhesive strength than gellan gum. Evaluation of ex vivo ocular tolerance using chorioallantoic membrane of hen's egg and cytotoxicity screening on Vero cells using resazurin assay revealed that caroboxymethyl gellan gum is non-irritant and biocompatible. Ionotiropically gelled beads of carboxymethyl gellan gum formulated using metformin as the model drug and calcium chloride as the cross-linking agent showed ex vivo bioadhesion of 100% over 24h. Further, it was observed that carboxymethyl gellan gum beads released metformin at a rate faster than gellan gum.

Mucoadhesive sustained delivery of diclofenac sodium using carbopol 675 and PVP admixtures as mucoadhesive motif

The mucoadhesiveness, swelling characteristics and release profile of diclofenac sodium from mucoadhesive tablets prepared with Carbopol 675 and polyvinyl pyrrolidone (PVP) and their physical mixtures were studied to evaluate their applicability in sustained drug delivery. The ex-vivo mucoadhesive strengths of the tablet compacts were determined by tensiometry using Lecomte du Nuoy tensiometer and everted pig jejunum. Release studies were carried out in three different pH media (1.2, 7.0 and 7.5). The results of mucoadhesive test revealed that tablets formulated from 1:1 physical mixture of Carbopol 675 and PVP had the highest mucoadhesive strength, which showed they bound tightly to the mucus pig jejunum. Their low swelling and release behaviours also indicated that the tablet compacts are very good candidates for sustained release formulation since release of diclofenac sodium was sustained by the compacts.