Floating mucoadhesive alginate beads of amoxicillin trihydrate: A facile approach for H. pylori eradication

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Abstract

This study investigates the design of sunflower oil entrapped floating and mucoadhesive beads of amoxicillin trihydrate using sodium alginate and hydroxypropyl methylcellulose as matrix polymers and chitosan as coating polymer to localize the antibiotic at the stomach site against Helicobacter pylori. Beads prepared by ionotropic gellation technique were evaluated for different physicochemical, in-vitro and in-vivo properties. Beads of all batches were floated for >24 h with a maximum lag time of 46.3 ± 3.2 s. Scanning electron microscopy revealed that the beads were spherical in shape with few oil filled channels distributed throughout the surfaces and small pocket structures inside the matrix confirming oil entrapment. Prepared beads showed good mucoadhesiveness of 75.7 ± 3.0% to 85.0 ± 5.5%. The drug release profile was best fitted to Higuchi model with non fickian driven mechanism. The optimized batch showed 100% Helicobacter pylori growth inhibition in 15 h in in-vitro culture. Furthermore, X-ray study in rabbit stomach confirmed the gastric retention of optimized formulation. The results exhibited that formulated beads may be preferred to localize the antibiotic in the gastric region to allow more availability of antibiotic at gastric mucus layer acting on Helicobacter pylori, thereby improving the therapeutic efficacy.

Introduction

Helicobactor pylori (H. pylori) is a small, spiral, microaerophilic, gram-negative bacteria with 4–6 bulbous tipped unipolar-sheathed flagella at it’s one end, which helps it to penetrate human gastric mucosa and colonize on the gastric antrum [1], [2]. Infection with H. pylori is universally accepted as the main threat for chronic gastritis and gastric carcinogenesis at present, and was classified as a carcinogen by the World Health Organization in 1994 [3]. Amoxicillin (α-amino-hydroxybenzylpenicillin) is a semi-synthetic, orally absorbed, broad-spectrum antibiotic. It is now widely used in a standard eradication treatment of gastric H. pylori infection combined with a second antibiotic and an acid-suppressing agent [4]. These triple therapies are proved to be effective in clinical application. However, some other reports and clinical trials indicate that the therapies cannot bring out complete eradication of H. pylori and suggest that the therapeutic effect needs more investigation [5]. One reason for the incomplete eradication of H. pylori is probably due to the short residence time of antimicrobial agents in the stomach so that effective antimicrobial concentration cannot be achieved in the gastric mucous layer or epithelial cell surfaces where H. pylori exists [6]. It has therefore been proposed that local delivery could increase drug levels in the gastric mucus and mucosa to effective bactericidal levels and extend the contact time of drugs with the organism [7].

Various strategies those are currently available for the development of improved amoxicillin trihydrate (AT) loaded formulations include the formation of floating tablets, mucoadhesive tablets, mucoadhesive beads, etc., in order to retain these in the gastrointestinal tract (GIT) for an extended time to offer increased effectiveness [8], [9], [10]. Since last decade, the strategy for effective delivery of antibiotics to H. pylori has shifted to the use of mucoadhesive microspheres to extend the residence time in the stomach, but their drug loading capacities are poor [11], [12]. On the other hand, beads have higher drug loading efficiency and can achieve sufficient therapeutic concentrations of antibiotics for treating gastric diseases, such as peptic ulcers [13], [14]. In addition, the bead formulations using vegetable oils can have a lower bulk density than gastric fluids, thereby causing the beads to float and be retained in the stomach [15]. The extended retention of the drug can maintain a higher antibiotic concentration in the gastric region where H. pylori exists and thereby improve the therapeutic efficacy.

Based on this concept, we have made an attempt to develop sunflower oil entrapped floating and mucosadhesive beads of amoxicillin trihydrate using sodium alginate and hydroxypropyl methylcellulose (HPMC) as matrix polymers and chitosan as coating polymer. The core polymer used, sodium alginate, is an inexpensive, nontoxic product extracted from kelp. Literature reports widespread use of sodium alginate for achieving sustained release of drugs [16], targeting gastric mucosa [17] and increasing the bioavailability of drugs [18]. Additionally it also reduces interfacial tension between an oil and water phase and is efficient for preparation of emulsion. Another core polymer, hydroxypropyl methylcellulose (HPMC), is a widely accepted pharmaceutical excipient, because HPMC is available in a wide range of molecular weights and it has been reported to enhance the sustained-release properties of alginate by providing a denser inner matrix [19]. Sunflower oil, the non-volatile oil compressed from sunflower (Helianthus annuus) seeds, also greatly aids the buoyancy the formulation [20]. Chitosan, a polysaccharide derived from chitin by alkaline deacetylation, has been proposed as a useful coating excipient for control release of water-soluble drugs [15].

Section snippets

Materials

Sodium alginate (low viscosity grade; 250 cP of 2% solution at 25 °C) was purchased from Loba Chemie Pvt. Ltd., Mumbai. Amoxicillin trihydrate (drug) was obtained as gift sample from Martina Bio Genics Private Limited, Kolkata. Sunflower oil (density 0.91 g/cm3 at 25 °C) was purchased from Agro Tech Food Ltd., Secundrabad, India. Glacial acetic acid was purchased from SD Fine Chem Ltd., India. Chitosan was purchased from Sisco Research Laboratories, Mumbai. Hydroxypropyl methylcellulose, Calcium

Formation of beads

When emulsion of sodium alginate and HPMC with sunflower oil was dropped into calcium chloride solution, spherical beads were then formed instantaneously due to intermolecular cross linking between the divalent calcium ions and the negatively charged carboxyl group of alginic acid, which provided a gel barrier at the surface of the formulation. Further, chitosan coating to the formulation offered extra protection from the harsh gastric environment. At slow speed of stirring, the oil get

Conclusion

The present work demonstrated a facile approach to develop sunflower oil entrapped chitosan coated floating mucoadhesive alginate beads to increase the efficacy of amoxicillin trihydrate for eradicating Helicobacter pylori infection. The oil-entrapped alginate beads as core accomplished by ionotropic gelation method and were further coated with chitosan barrier. These developed floating beads exhibited good mucoadhesive property (mucoadhesiveness of 75.7 ± 3.0%–85.0 ± 5.5%, excellent drug

Conflict of interest

The authors report no conflict of interest.

Acknowledgements

Authors would like to acknowledge to Jadavpur University, Kolkata, India and Dr. B. C. Roy College of Pharmacy and AHS, Durgapur, India for providing the necessary facilities to carry out this research work. The authors are thankful to National Institute of Cholera and Enteric Diseases, Kolkata, India for providing the essential laboratory facilities for in-vitro Helicobacter pylori growth inhibition study. The authors also wish to express thanks to Martina Bio Genics Private Limited, Kolkata,

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