Preparation of floating alginate gel beads for drug delivery to the gastric mucosa

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

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 >24h with a maximum lag time of 46.3±3.2s. 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 15h 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.

Preparation and evaluation of berberine alginate beads for stomach-specific delivery

The purpose of this research was to prepare floating calcium alginate beads of berberine for targeting the gastric mucosa and prolonging their gastric residence time. The floating beads were prepared by suspending octodecanol and berberine in sodium alginate (SA) solution. The suspension was then dripped into a solution of calcium chloride. The hydrophobic and low-density octodecanol enhanced the sustained-release properties and floating ability of the beads. The bead formulation was optimized for different weight ratios of octodecanol and SA and evaluated in terms of diameter, floating ability and drug loading, entrapment and release. In vitro release studies showed that the floating and sustained release time were effectively increased in gastric media by addition of octodecanol. In vivo studies with rats showed that a significant increase in gastric residence time of beads had been achieved.

Floating drug delivery of nevirapine as a gastroretentive system

A multiple-unit floating drug delivery system based on gas formation technique was developed, in order to prolong the gastric residence time and to increase the overall bioavailability of the dosage form. The floating bead formulations were prepared by dispersing nevirapine together with calcium carbonate in a mixture of sodium alginate and hydroxypropyl methylcellulose solution and then dripping the dispersion into an acidified solution of calcium chloride. Calcium alginate beads were formed, as the alginate underwent ionotropic gelation by calcium ions, and carbon dioxide developed from the reaction of carbonate salts with acid. The obtained beads were able to float due to CO(2)-gas formation and the gas entrapment by the polymeric membrane. The prepared beads were evaluated for percent drug loading, drug entrapment efficiency, morphology, surface topography, buoyancy, in-vitro release, and release kinetics. The formulations were optimized for different weight ratios of the gas-forming agent and sodium alginate. The beads containing higher amounts of calcium carbonate demonstrated an instantaneous, complete, and excellent floating ability over a period of 24 hours. The increased amount of the gas forming agent did not affect the time to float, but increased the drug release from the floating beads, while increasing the coating level of the gas-entrapped membrane, increased the time to float, and slightly retarded the drug release. Good floating properties and sustained drug release were achieved. Finally, these floating beads seemed to be a promising gastroretentive drug delivery system.

Metronidazole-loaded bioabsorbable films as local antibacterial treatment of infected periodontal pockets

BACKGROUND

Periodontal disease is infectious in nature and leads to an inflammatory response. It arises from the accumulation of subgingival bacterial plaque and leads to the loss of attachment, increased probing depth, and bone loss. It is one of the world's most prevalent chronic diseases. In this study we developed and studied metronidazole-loaded 50/50 poly(DL-lactide-co-glycolide) (PDLGA), 75/25 PDLGA, and poly(DL-lactic acid) (PDLLA) films. These films are designed to be inserted into the periodontal pocket and treat infections with controlled-release metronidazole for >or=1 month.

METHODS

The structured films were prepared using the solution-casting technique. Concentrated solutions and high solvent-evaporation rates were used to get most of the drug located in the bulk, i.e., in whole film's volume. The effects of copolymer composition and drug content on the release profile, cell growth, and bacterial inhibition were investigated.

RESULTS

The PDLLA and 75/25 PDLGA films generally exhibited a low- or medium-burst release followed by a moderate release at an approximately constant rate, whereas the 50/50 PDLGA films exhibited a biphasic release profile. The drug released from films loaded with 10% weight/weight metronidazole resulted in a significant decrease in bacterial viability within several days. When exposed to human gingival fibroblasts in cell culture conditions, these films maintained their normal fibroblastic features.

CONCLUSIONS

This study enabled the understanding of metronidazole-release kinetics from bioabsorbable polymeric films. The developed systems demonstrated good biocompatibility and the ability to inhibit Bacteroides fragilis growth; therefore, they may be useful in the treatment of periodontal diseases.

Structured Drug-eluting Bioresorbable Films: Microstructure and Release Profile

Bioresorbable drug-eluting films can be used in many biomedical applications. Examples for such applications include biodegradable medical support devices which combine mechanical support with drug release and antibiotic-eluting film coatings for prevention of bacterial infections associated with orthopedic implants or during gingival healing. In the current study, bioresorbable drug-loaded polymer films are prepared by solution processing. Two film structures are studied: A polymer film with large drug crystals located on its surface (A-type) and a polymer film with small drug particles and crystals distributed within the bulk (B-type). The basic mode of drug dispersion/location in the film (A or B-type) is found to be determined mainly by the process of film formation and depends mainly on the solvent evaporation rate, whereas the drug's hydrophilicity has a minor effect on this structuring process. Most release profiles from A-type films exhibit a burst effect of ~30% and a second release stage that occurs at an approximately constant rate and is determined mainly by the polymer weight loss rate. An extremely high burst release is exhibited only by a very hydrophilic drug. The matrix (monolithic) nature of the B-type film enables release profiles that are determined mainly by the host polymer's degradation profile, with a very low burst effect in most of the studied systems. In addition to the drug location/ dispersion in the film, the host polymer and drug type also strongly affect the drug's release profile from the film. It has been demonstrated that appropriate selection of the process parameters and film components (polymer and drug) can yield film structures with desirable drug release behaviors. This can lead to the engineering of new bioresorbable drug-eluting film-based implants for various applications.

Stomach-specific drug delivery of 5-fluorouracil using floating alginate beads

A multiple-unit-type oral floating dosage form (FDF) of 5-fluorouracil (5-FU) was developed to prolong gastric residence time, target stomach cancer, and increase drug bioavailability. The floating bead formulations were prepared by dispersing 5-FU together with calcium carbonate into a mixture of sodium alginate and hydroxypropyl methylcellulose solution and then dripping the dispersion into an acidified solution of calcium chloride. Calcium alginate beads were formed, as alginate undergoes ionotropic gelation by calcium ions and carbon dioxide develops from the reaction of carbonate salts with acid. The evolving gas permeated through the alginate matrix, leaving gas bubbles or pores, which provided the beads buoyancy. The prepared beads were evaluated for percent drug loading, drug entrapment efficiency, image, surface topography, buoyancy, and in vitro release. The formulations were optimized for different weight ratios of gas-forming agent and sodium alginate. The beads containing higher amounts of calcium carbonate demonstrated instantaneous, complete, and excellent floating ability over a period of 24 hours. The optimized formulation was subjected to in vivo antitumor studies to check the therapeutic efficacy of the floating dosage forms containing 5-FU against benzo(a)pyrene-induced stomach tumors in albino female mice (Balb/C strain). The multiple-bead FDF was found to reduce the tumor incidence in mice by 74%, while the conventional tablet dosage form reduced this incidence by only 25%. Results indicate that FDF performed significantly better than the simple tablet dosage form.

Multiple-channel emulsion chips utilizing pneumatic choppers for biotechnology applications

The formation of micro-scale monodispersed emulsions is crucial for a variety of applications such as cosmetics, food industry and biotechnology. In this study, a new microfluidic chip with a multiple-channel layout for high-throughput emulsions is reported. This chip generated fine-tuned and uniform microdroplets in liquids with a higher throughput for emulsification applications. It employed a combination of multiple hydrodynamic flow focusing and liquid-cutting devices called "active pneumatic choppers." Experimental data indicated that oil-in-water microdroplets with diameters ranging from 6 to 120 microm can be successfully generated with a coefficient of variation less than 3.75%. The size of the droplets can be actively fine-tuned by using two approaches by adjusting relative sheath/sample flow velocity ratios and chopping frequency. Finally, two commonly used biocompatible materials, including collagen and calcium-alginate (Ca-alginate), were used to form microspheres by utilizing the liquid-cutting technique. The developed microfluidic chip is promising in various applications including biotechnology, nano-medicine and cosmetics.

Sustained release of hydrophobic and hydrophilic drugs from a floating dosage form

Floating dosage forms enable the sustained delivery of drugs in the gastro-intestinal tract. In this study, a type of multi-unit floating gel bead was synthesized with calcium alginate, sunflower oil, and a drug of interest through an emulsification/gelation process. The alginate beads with oil addition were able to continuously float over the medium for 24h under constant agitation while the non-oily beads could not. Three kinds of drugs with different hydrophilicities, ibuprofen, niacinamide and metoclopramide HCl, were tested in the study. The hydrophobic drug ibuprofen was released in a sustained manner for 24h, due to the oil partitioning. With suitable modification, the beads were able to also release the hydrophilic drugs, niacinamide and metoclopramide HCl, for a similar duration. Therefore a floating dosage form that is able to sustain release both hydrophobic and hydrophilic drugs within its extended gastric retention time has been developed.

Multifunctional Drug Delivery System Using Starch-Alginate Beads for Controlled Release

Utilizing starch-containing alginate beads, a novel drug delivery system (DDS) was developed. With the starch inside, the composite bead could be dried in its original bead shape and handled in the dried state. By employing alginate multi-coating strategy on the starch-alginate beads, detained or controlled release was efficiently achieved and successfully demonstrated for a model peptide drug, L-phenylalanine. The initial latent time and release rate of the drug inside the beads were able to be controlled simply by varying the number of multi-coatings. While the latent time for the initial release was negligible for non-coated starch-alginate beads, the latent times of beads coated one, two, and four times increased to 15, 30, and 70 min, respectively. Furthermore, the alginate component of the composite beads could adsorb and remove heavy metals such as lead from the body. These multifunctional beads combined with the novel coating process will greatly benefit alginate gel-based DDS.

Properties of calcium-induced gel beads prepared with alginate and hydrolysates

Calcium-induced alginate gel beads (Alg-Ca) containing alginate hydrolysate, such as the guluronic acid block (GB), was prepared and the drug release profiles were investigated under simulated gastrointestinal conditions. The addition of GB to Alg-Ca altered its rheological properties. A model drug (hydrocortisone) was incorporated at 78% of its theoretical yield within the dried Alg-Ca containing 5% GB and it was gradually released from the beads in JP XIV 1st medium for disintegration test (pH 1.2), while it was rapidly released with disintegration of the gel matrix in JP XIV 2nd medium (pH 6.8). In contrast, for Alg-Ca containing GB and chitosan, disintegration was not observed in these media and the drug release rate was markedly different. These results demonstrate that the release profiles of drugs incorporated into Alg-Ca can be controlled by adding these polysaccharides.