Effects of natural polysaccharide addition on drug release from calcium-induced alginate gel beads

Alginate-poloxamer beads for clotrimazole delivery: Molecular interactions, mechanical properties, and anticandidal activity

Calcium alginate (CA) beads loaded with clotrimazole (CZ) were modified by adding poloxamer (PLX) in this study. Blends of PLX188 or PLX407 into sodium alginate (SA) dispersions caused a decrease in the SA zeta potential and led to viscosity synergism. SA with carboxyl and hydroxyl groups can interact with the hydroxyl groups of PLX via hydrogen bonding. A stronger interaction of SA with PLX407 was found when compared to the interaction between SA and PLX188. The PLX-CA beads gave a higher CZ entrapment efficiency than the CA beads. The highest PLX content used created an amorphous form of CZ in the beads because of the CZ solubilization by the PLX micelles. The addition of 0.5 or 1% w/v PLX can strengthen the CZ-loaded CA beads. Furthermore, the PLX-CA beads display a lower water uptake than the CA beads. PLX micellization can enhance CZ release and enhance the efficacy of CZ against Candida albicans. This study indicates that the molecular interaction of SA with PLX and the PLX micellization of CZ can improve the characteristics of CZ-loaded CA beads, which offer good potential for use as drug delivery systems or drug reservoirs in tablets for oral candidiasis.

Development of Functional or Medical Foods for Oral Administration of Insulin for Diabetes Treatment: Gastroprotective Edible Microgels

Insulin and an antacid [Mg(OH)₂] were co-encapsulated inside calcium alginate microgels (diameter = 280 μm) using a vibrating nozzle injector. Confocal microscopy indicated that insulin was successfully encapsulated inside the microgels and remained inside them after they were exposed to simulated gastric conditions. Localized fluorescence intensity measurements indicated that the internal pH of the antacid-loaded microgels was around pH 7.4 after incubation in acidic gastric fluids but below the limit of detection (pH < 4) in the antacid-free microgels. After incubation in small intestine conditions, around 30% of the insulin was released from the antacid-loaded microgels over a 2 h period. Encapsulation of insulin within the antacid-loaded microgels increased its biological activity after exposure to simulated gastric conditions. In particular, the encapsulated insulin significantly increased Akt phosphorylation at both Thr308 and Ser473 in L6 myotubes when compared to free insulin.

Calcium Alginate-Neusilin US2 Nanocomposite Microbeads for Oral Sustained Drug Delivery of Poor Water Soluble Drug Aceclofenac Sodium

The aim of the present study was to formulate and investigate the calcium alginate- (CA-) Neusilin US2 nanocomposite microbeads containing preconcentrate of aceclofenac sodium (ACF-Na) liquid microemulsion (L-ME) for enhancement of oral bioavailability. The preconcentrate L-ME is prepared by using Labrafac PG, Labrasol, and Span 80 as oil, surfactant, and cosurfactant, respectively. The solid CA nanocomposite microbeads of L-ME prepared by microemulsification internal gelation technique using sodium alginate (SA) gelling agent, Neusilin US2 as adsorbent, and calcium chloride as crosslinking agent. L-ME has good thermodynamic stability; globule size was found to be 32.4 nm with polydispersity index 0.219 and -6.32 mV zeta potential. No significant interactions of excipients, drug in the formulations observed by FT-IR, DSC and XPRD. The concentration of SA and Neusilin US2 influences the flow properties, mean particle size, mechanical strength, drug entrapment efficiency, and percentage of drug release. All the formulations show minimum drug release in simulated gastric fluid (SGF) pH 1.2 for initial 2 h, maximum drug release in pH 6.8 phosphate buffer solution (PBS) at 6 h, followed by sustaining in simulated intestinal fluid (SIF) of pH 7.4 up to 12 h. The interaction of SA with Neusilin US2 creates a thick thixotropic gel network structure which acts as barrier to control the release of drug in the alkaline pH environment. Neusilin US2 is a novel filler used to convert L-ME into solid nanocomposite microbeads to enhance dissolution rate of poor water soluble drugs sustaining the drug release for prolonged period of time.

Microencapsulation of probiotic strains for swine feeding

Probiotics are live microorganisms which have health-promoting attributes. These bacteria must overcome biological barriers, including acid in the stomach and bile in the intestine to exert beneficial effects. The encapsulation consists in a provision of an outer layer to protect the core material from damage. Microencapsulating in calcium alginate, nowadays, is being used to bacteria immobilization owing to its easy handling, nontoxic nature, and low cost. The aims of this study were to improve the microencapsulating method for probiotic bacteria and to investigate whether the material used as coating, afford an increase on strain survival under simulated gastrointestinal conditions. Lactic acid bacteria used in this work were isolated from feces of young and healthy pigs and they were selected because of their probiotic properties. Our results showed that the optimal encapsulation process was achieved using 1 : 1 (v/v) 20% non fat milk cell suspension mixed with 1.8% sodium alginate solution. Alginate capsules hardening was carried out using 0.1 m calcium chloride solution for 30 min. This microencapsulating technique could protect the probiotic bacteria against gastric environment, allowing viable cells get to the intestinal tract. So it could be a useful way to deliver these beneficial bacteria to host.

Sulindac loaded alginate beads for a mucoprotective and controlled drug release

Ionotropic gelation was used to entrap sulindac into calcium alginate beads as a potential drug carrier for the oral delivery of this anti-inflammatory drug. Beads were investigated in vitro for a possible sustained drug release and their use in vivo as a gastroprotective system for sulindac. Process parameters such as the polymer concentration, polymer/drug ratio, and different needle diameter were analysed for their influences on the bead properties. Size augmented with increasing needle diameter (0.9 mm needle: 1.28 to 1.44 mm; 0.45 mm needle: 1.04 to 1.07 mm) due to changes in droplet size as well as droplet viscosity. Yields varied between 87% and 98% while sulindac encapsulation efficiencies of about 88% and 94% were slightly increasing with higher alginate concentrations. Drug release profiles exhibited a complete release for all formulations within 4 hours with a faster release for smaller beads. Sulindac loaded alginate beads led to a significant reduction of macroscopic histological damage in the stomach and duodenum in mice. Similarly, microscopic analyses of the mucosal damage demonstrated a significant mucoprotective effect of all bead formulation compared to the free drug. The present alginate formulations exhibit promising properties of a controlled release form for sulindac; meanwhile they provide a distinct tissue protection in the stomach and duodenum.

Insulin encapsulation in reinforced alginate microspheres prepared by internal gelation

Insulin-loaded alginate microspheres prepared by emulsification/internal gelation were reinforced by blending with polyanionic additive polymers and/or chitosan-coating in order to increase the protection of insulin at simulated gastric pH and obtain a sustained release at simulated intestinal pH. Polyanionic additive polymers blended with alginate were cellulose acetate phtalate (CAP), Eudragit L100 (EL100), sodium carboxymethylcellulose (CMC), polyphosphate (PP), dextran sulfate (DS) and cellulose sulfate (CS). Chitosan-coating was applied by using a one-stage procedure. The influence of additive polymers and chitosan-coating on the size distribution of microspheres, encapsulation efficiency and release profile of insulin in simulated gastrointestinal pH conditions was studied. The mean diameter of blended microspheres ranged from 65 to 106 microm and encapsulation efficiency of insulin varied from 14 to 100%, reaching a maximum value when CS and DS were incorporated in the alginate matrix. Insulin release, at pH 1.2, was almost prevented by the incorporation of PP, DS and CS. When uncoated microspheres were transferred to pH 6.8, a fast dissolution occurred, independently of the additive polymer blended with alginate, and insulin was completely released. Increasing the additive polymer concentration in the alginate matrix and/or chitosan-coating the blended alginate microspheres did not promote a sustained release of insulin from microspheres at pH 6.8.

Molecular interaction in alginate beads reinforced with sodium starch glycolate or magnesium aluminum silicate, and their physical characteristics

Diclofenac calcium-alginate (DCA) beads were reinforced with different amounts of sodium starch glycolate (SSG) or magnesium aluminum silicate (MAS) and were prepared using ionotropic gelation method. Complex formation of sodium alginate (SA) and SSG or MAS in calcium-alginate beads was revealed using FTIR spectroscopy. Differential scanning calorimetric study indicated that diclofenac sodium (DS) in amorphous form was dispersed in the matrix of DCA beads. The thermal behavior of SSG-DCA and MAS-DCA beads was similar to the control bead. Both additives can improve the entrapment efficiency of DCA beads. The swelling and water uptake of the beads depended on the properties of incorporated additives. The SSG-DCA beads showed a higher water uptake and swelling than MAS-DCA beads. Moreover, the swelling of the beads showed a good correlation with the square root of time. The release kinetic of the beads in pH 6.8 phosphate buffer was swelling controlled mechanism, while that in distilled water followed Higuchi's model. The slower release rate and the longer lag time in pH 6.8 phosphate buffer was obtained from the SSG-DCA and MAS-DCA beads because of complex formation between SA and SSG or MAS. However, SSG in the beads could increase the release of DS from the beads in distilled water because it acted as a channeling agent. In contrast, MAS retarded the release of DS from the beads in distilled water due to the stronger matrix formation.

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.

Properties of an Alginate Gel Bead Containing a Chitosan-Drug Salt

A calcium-induced alginate gel bead (Alg-CS) containing chitosan (CS) and 2-(4-chlorophenoxy)-2-methylpropionic acid (CMP) was prepared. We then investigated (a) CMP release from Alg-CS, and (b) uptake of bile acid into the Alg-CS, within the gastrointestinal tract. Dried Alg-CS gradually swelled in taurocholate solution, while releasing CMP and taking up bile acid. The amount of bile acid taken up into the Alg-CS increased incrementally according to the degree of deacetylation of CS. Furthermore, the molecular weight of CS also affected the properties of the Alg-CS. An approximately linear relationship was observed between CMP release and bile acid uptake of Alg-CS.