Release characteristics of brilliant blue from calcium-alginate beads coated with quaternized chitosan

Calcium-alginate beads coated with quaternized chitosan were prepared in a neutral environment, and morphologies were observed by SEM. Optimum conditions for the encapsulation and retention of a model drug (brilliant blue, BB) in acid were obtained from studies of preparation conditions, including alginate and quaternized chitosan concentration, calcium chloride (CaCl2) concentration in the gelling medium and by comparing one-step and two-step preparation methods. Results showed that very high BB encapsulation efficiency (99%, w/w) and low leakage in acid (8%, w/w) was achieved from dry beads when 2.0% (w/v) alginate was dropped into 1.0% (w/v) CaCl2 containing 0.3% (w/v) quaternized chitosan by a one-step method. The release of BB in 0.9% (w/v) NaCl was modulated by coating calcium-alginate with different weight average molecule weight (Mw) and degree of substitution (DS) of quaternized chitosan. A decreased of Mw accelerated the release of BB and a high DS value significantly decreased the release in 0.9% (w/v) NaCl.     

The release behavior of brilliant blue from calcium-alginate gel beads coated by chitosan: the preparation method effect.

The aim of this study is to reveal how the release behavior of a model drug (brilliant blue, BB) from chitosan coating calcium-alginate gel beads (CCAGB) was influenced by the preparation methods. The CCAGB were prepared by dropping alginate solution into CaCl(2)/chitosan solution (method 1(a)), or into chitosan solution then gelled by CaCl(2) (method 1(b)), or into CaCl(2) solution then coated by chitosan (method 2). Scanning electron microscopy was used for morphology observation, and elemental analysis was applied to determine the chitosan content bound on calcium-alginate gel beads (CAGB). Compared to CAGB, the dried CCAGB had poorer shape and rougher surface morphology especially in methods 1(a) and (b); moreover, CCAGB was found to be more instable in 0.9% NaCl and serious burst of beads occurred when high concentration of alginate (3.0 and 5.0% w/v) was used. The influence on BB release from the beads by chitosan coating was not only related to the chitosan density on bead surface, but also preparation method and other factors. Under un-dried bead state in method 1(a), the increase of chitosan content prolonged BB release in 0.9% (w/v) NaCl; while in method 2, the increase of chitosan concentration over 0.1% (w/v) (3.0% (w/v) alginate concentration was used) resulted in more serious burst of beads and hence facilitated BB release. Furthermore, in both methods 1(a) and 2, the increase of alginate from 1.5 to 3.0 or 5.0% (w/v) usually resulted in the significant burst of beads and accelerated BB release when 0.3 or 0.5% (w/v) chitosan was used for coating. Drying process greatly influenced BB release profile due to the destroying of alginate-chitosan film. The acceleration of BB release from CCAGB by drying process was more significant in the case of method 1 than of method 2.     

Mucoadhesive and floating chitosan-coated alginate beads for the controlled gastric release of amoxicillin

This work focused on the development of mucoadhesive and floating chitosan-coated alginate beads as a gastroretensive delivery vehicle for amoxicillin, towards the effective eradication of Helicobacter pylori, a major causative agent of peptic ulcers. Alginate was used as the core bead core polymer and chitosan as the mucoadhesive polymer coating. Amoxicillin-loaded alginate beads coated with 0.5% (w/v) chitosan (ALG/0.5%CHI) exhibited excellent floating ability, high encapsulation efficiency, high drug loading capacity, and a strong in vitro mucoadhesion to the gastric mucosal layer. In vitro, amoxicillin was released faster in simulated gastric fluid (pH 1.2, HCl) than in simulated intestinal fluid (phosphate buffer, pH 7.4). ALG/0.5%CHI could be prepared with a > 90% drug encapsulation efficiency and exhibited more than 90% muco-adhesiveness, 100% floating ability, and achieved sustained release of amoxicillin for over six hours in SGF.     

Novel pH-sensitive citrate cross-linked chitosan film for drug controlled release

Turbidimetric titration revealed that there were electrostatic attractive interactions between citrate and chitosan in the pH region of 4.3-7.6, depending on their degree of ionization. Citrate cross-linked chitosan film was prepared simply by dipping chitosan film into sodium citrate solution. The swelling ratio of citrate/chitosan film was sensitive to pH, ionic strength etc. Under acidic conditions, citrate/chitosan film swelled and even dissociated in the pH less than 3.5, and the model drugs (brilliant blue and riboflavin) incorporated in the film were released quickly (usually within 2 h released completely in simulated gastric fluid at 37 degrees C) while under neutral conditions the swelling ratio of citrate/chitosan film was less significant and the release rate of brilliant blue and riboflavin was low (less than 40% released in simulated intestinal fluid in 24 h). Sodium chloride weakened the electrostatic interaction between citrate and chitosan, and therefore facilitated the film swelling and accelerated drug release. The parameters of film preparation such as citrate concentration, solution pH etc. influencing the film swelling and drug release profiles were examined. The lower concentration and the higher pH of citrate solution resulted in a larger swelling ratio and quicker riboflavin release. To improve the drug controlled release properties of citrate/chitosan film, heparin, pectin and alginate were further coated on the film surface. Among them only the coating of alginate prolonged riboflavin release noticeably (for 80% of drug released the time was extended from 1.5 to 3.5 h with 0.5% w/v alginate used). The results indicated that the citrate/chitosan film was useful in drug delivery such as for the site-specific drug controlled release in stomach.     

Mucoadhesive Polymers in Peroral Peptide Drug Delivery. VI. Carbomer and Chitosan Improve the Intestinal Absorption of the Peptide Drug Buserelin In Vivo

Purpose. To evaluate the effect of the crosslinked poly(acrylate) carbomer 934P (C934P) and its freeze-dried neutralized sodium salt (FNaC934P) as well as chitosan hydrochloride on the intestinal absorption of the peptide drug buserelin. Methods. Buserelin was applied intraduodenally in control buffer, 0.5% (w/v) C934P, 0.5% (w/v) FNaC934P, 1.5% (w/v) chitosan hydrochloride or FNaC934P/chitosan hydrochloride (1:1 (v/v)) mixture in rats. Results. All polymer preparation showed a statistically significant improvement of buserelin absorption compared to the control solution. The absolute bioavailabilities for the different polymer preparations were: control, 0.1%; 0.5% FNaC934P, 0.6%; 0.5% C934P, 2.0%; chitosan hydrochloride, 5.1% and FNaC934P/chitosan hydrochloride (1:1 (v/v)) mixture, 1.0%. The higher bioavailability with chitosan hydrochloride compared to C934P and FNaC934P indicates that for buserelin the intestinal transmucosal transport enhancing effect of the polymer plays a more dominant role than the protection against proteases such as -chymotrypsin. Conclusions. The mucoadhesive polymers carbomer 934P and chitosan hydrochloride are able to enhance the intestinal absorption of buserelin in vivo in rats, and may therefore be promising excipients in peroral delivery systems for peptide drugs.     

Characterization of alginate/poly-L-lysine particles as antisense oligonucleotide carriers

The gel forming characteristics of alginate in the presence of calcium ions and further crosslinking with poly-L-lysine led to the formation of sponge-like nano- and microparticles. The particle size was varied by adjusting the final concentrations of and proportions between the components. The region for particle formation was from 0.04 to 0.08% (w/v) of alginate in the final formulation, the change from the nm to microm size range occurred at a concentration of approx. 0.055% (w/v). Oligonucleotide-loaded microparticles were prepared by two different methods, either by absorption of the drug into the crosslinked polymeric matrix or by incorporation of an oligonucleotide/poly-L-lysine complex into a calcium alginate pre-gel. The release of oligonucleotide from microparticles prepared by the first method was higher. The addition of increasing amounts of poly-L-lysine resulted in larger particles, higher oligonucleotide loading and slower drug release. An increase in the final solid content of the formulation led to larger particles, especially with high concentrated calcium alginate pre-gels. Microparticles based on alginate and poly-L-lysine are potential carriers for antisense oligonucleotides.     

Preparation and characterization of Mitomycin-C loaded chitosan-coated alginate microspheres for chemoembolization

Mitomycin-C loaded and chitosan-coated alginate microspheres were prepared for use in chemoembolization studies. In this respect, first alginate microspheres were prepared by using a spraying method using an extrusion device with a small orifice and following suspension cross-linking in an oil phase. Chitosan-coating onto the alginate microspheres was achieved by polyionic complex formation between alginate and chitosan. CaCl(2) was used as a cross-linker for alginate microspheres. The obtained chitosan-coated alginate microspheres were spherical shaped and approximately 100-400 microm average size. The microspheres were evaluated based on their swellability and the swelling ratio was changed between 50-280%. CaCl(2) concentration, stirring rate, chitosan molecular weight, chitosan concentration and time for coating with chitosan were selected as the effective parameters on microsphere size and swelling ratio. Equilibrium swellings were achieved in approximately 30 min. On the other hand, chitosan molecular weight, chitosan concentration and time for coating with chitosan were found as the most effective parameters on both drug loading ratio and release studies. Maximum drug loading ratio of 65% was achieved with high molecular weight (HMW) chitosan, highest chitosan concentration (i.e. 1.0% v/v) and shortest time for coating with chitosan (i.e. 1 h) values.     

Mucoadhesive microspheres for nasal administration of an antiemetic drug, metoclopramide: in-vitro/ex-vivo studies

Microparticulate delivery systems designed for the nasal administration of an antiemetic drug, metoclopramide hydrochloride, were prepared. Microspheres composed of sodium alginate, chitosan hydrochloride, or both, were obtained using a spray-drying method; some batches of drug-free microparticles were prepared as a comparison. The morphology, in-vitro swelling behaviour, mucoadhesive properties and drug release from microparticles were evaluated. Ex-vivo drug permeation tests were carried out using sheep nasal mucosa; permeation test of the drug solution was performed as comparison. During ex-vivo permeation tests, transmission electron microscopy (TEM) analyses were carried out on the nasal mucosa to study the morphological changes of epithelial cells and tight junctions, while the change in microsphere morphology was examined using photostereo microscopy (PM). Spray-dried microparticles had a mean diameter (d(vs)) in the range of about 3-10 microm. They showed good in-vitro mucoadhesive properties. In-vitro release profiles and swelling behaviour depended on their composition: the drug release occurred in 1-3 h. Ex-vivo studies showed that drug permeation through the mucosa from microparticles based on chitosan was higher than from those consisting of alginate alone. This can be related to the penetration enhancing properties of chitosan. Complexation of chitosan with alginate led to a control of the drug release. Microscopy observation of microspheres during the permeation tests revealed that microparticles swelled and gelled, maintaining their shape. TEM analyses of the mucosa after exposure to the microparticles consisting of alginate/chitosan showed opened tight junctions. This preliminary study shows that alginate/chitosan spray-dried microspheres have promising properties for use as mucoadhesive nasal carriers of an antiemetic drug.     

Methylated N-(4-N,N-dimethylaminocinnamyl) chitosan-coated electrospray OVA-loaded microparticles for oral vaccination

The purpose of this study was to prepare microparticles entrapping ovalbumin (OVA) as a model antigen to induce immune responses in mice following oral vaccination. In this study, calcium-alginate and calcium-yam-alginate microparticles were prepared by crosslinking alginate with calcium chloride solution using an electrospraying technique. 0.1% (w/v) of methylated N-(4-N,N-dimethylaminocinnamyl) chitosan (TM₆₅CM₅₀CS) was used to coat microparticles entrapping an initial OVA of 20% w/w to polymer. The results indicated that the coated microparticles were spherical and had a smooth surface, with an average size of 1–3 μm, and were positively charged. In addition, the particles demonstrated a greater swelling and mucoadhesive properties than did uncoated microparticles. The in vitro release from the microparticles indicated that the coated microparticles resulted in more sustained release than uncoated microparticles. The cytotoxicity results showed that all of the formulations were safe. The in vivo oral administration demonstrated that at the same amount of 250 μg OVA, coated microparticles exhibited the highest in vivo adjuvant activity in both IgG and IgA immunogenicity.     

5-Fluorouracil encapsulated alginate beads for the treatment of breast cancer

Alginate beads containing 5-fluorouracil (5-FU) were prepared by the gelation of alginate with calcium cations. Alginate beads loaded with 5-FU were prepared at 1.0 and 2.0% (w/v) polymers. The effect of polymer concentration and the drug loading (1.0, 5.0 and 10%) on the release profile of 5-FU was investigated. As the drug load increased, larger beads were obtained in which the resultant beads contained higher 5-FU content. The encapsulation efficiencies obtained for 5-FU loads of 1.0, 5.0 and 10% (w/v) were 3.5, 7.4 and 10%, respectively. Scanning electron microscopy (SEM) and particle size analysis revealed differences between the formulations as to their appearance and size distribution. The amount of 5-FU released from the alginate beads increased with decreasing alginate concentrations.     

亚甲蓝海藻酸微球的研究

报道了一种适合于放大规模的制备多孔隙的海藻酸微球的方法—喷雾-凝聚法。当5％(w／v)海藻酸钠溶液通过3／8″的喷枪在40～60psi气压下喷雾到1mol／L氯化钙溶液中可以形成空隙率最大的微球。亚甲蓝被选作水溶性阳离子模型药物。亚甲蓝的载药方法是吸附法。亚甲蓝的释放度结果表明载药微球在去离子水中释药不完全，在氯化钠溶液中由于钠离子和钙离子的交换使微球崩解而迅速释放药物。结果表明：由喷雾凝聚法制得的海藻酸微球可以作为通过温和的条件载运阳离子药物。     

酮洛芬果胶钙凝胶小球和海藻酸钙凝胶小球的制备及性能比较

目的酮洛芬果胶钙凝胶小球和酮洛芬海藻酸钙凝胶小球的制备及性能比较。方法利用果胶、海藻酸钠及二者不同比例,以酮洛芬为模型药物采用滴制法制备凝胶小球,考察2种多糖物质对药物包封率和释放行为的影响。利用大鼠肠囊外翻实验对凝胶小球的生物黏附性能进行比较,通过对释放机理的探讨和凝胶小球溶胀性的测定进一步证明2种凝胶小球释药行为的不同。结果酮洛芬果胶钙凝胶小球和酮洛芬海藻酸钙凝胶小球均具有良好的生物黏附性能,果胶钙凝胶小球主要通过溶胀作用缓慢释药,而海藻酸钙凝胶小球的释药与凝胶小球慢慢吸水后骨架溶蚀有关。结论酮洛芬果胶钙凝胶小球和酮洛芬海藻酸钙凝胶小球通过与生物黏膜的紧密结合缓慢释药,而二者的释放行为有所不同。     

Effect of manufacturing parameters on the characteristics of vitamin C encapsulated tripolyphosphate-chitosan microspheres prepared by spray-drying

To prepare the sustained release vitamin C carriers, vitamin C was successfully encapsulated in tripolyphosphate (TPP) cross-linked chitosan (TPP-chitosan) microspheres by the spray-drying method at different manufacturing conditions. Manufacturing parameters (inlet temperature, liquid flow rate, chitosan concentration and volume of 1% w/v TPP solution) had a significant influence on the characteristics of thus prepared microspheres. The optimum spray-drying conditions such as inlet temperature, liquid flow rate and compressed air flow rate for the encapsulation of vitamin C in TPP-chitosan microspheres was found to be 170 degrees C, 2 ml min(-1) and 101 min(-1), respectively. The size and yield of the TPP-chitosan microspheres ranged from 3.9-7.3 microm and 54.5-67.5%, respectively. The encapsulation efficiency of TPP-chitosan microspheres ranged from 45.72-68.7% and it decreased with the increasing volume of 1% w/v TPP solution. At the same cross-linking extent, the encapsulation efficiency of TPP-chitosan microspheres increased when the concentration of chitosan was increased from 0.5-1% w/v. Effect of volume of 1% w/v TPP solution on the surface morphology of chitosan microspheres was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These studies revealed that chitosan solution (250 ml) cross-linked with 15 ml 1% w/v TPP solution produced more porous microspheres than that cross-linked with 5 and 10 ml TPP solution. The release rate of vitamin C from TPP-chitosan microspheres decreased when the concentration of chitosan was increased from 0.5-1.0% w/v. Vitamin C release rate was also modulated by varying the volume of 1% w/v TPP solution. The release rate of vitamin C from TPP-chitosan microspheres decreased with increasing volume (5-15 ml) of 1% w/v TPP solution.     

In vitro and in vivo characterization of scleral implant of indomethacin: role of plasticizer and cross-linking time

Film-type scleral implants of indomethacin using sodium alginate and PEG 400 and 600 (3, 5, 8, and 10% w/w w.r.t. sodium alginate) as plasticizers were fabricated by solvent casting. The prepared implants were cross-linked by treatment with calcium chloride 10, 20, and 30% w/v solution, for periods between 1 to 24 hr. Uniformity of thickness, weight, and drug content and surface pH of the implants were evaluated. The influence of plasticizer type/concentration and crosslinking time/concentration of calcium chloride on indomethacin release was studied on a static dissolution setup developed by us. Selected batches of the implants were subjected to pharmacodynamic studies, after scleral placement, in uveitis-induced (intravitreal injection of bovine serum albumin 50 μg/ml) rabbit eyes. The release of indomethacin from the implants was influenced by the concentration and nature of plasticizers used. Chemical cross-linking with calcium chloride was successful in retarding the drug release. The pharmacodynamic studies showed a marked improvement in the various clinical parameters (congestion, keratitis, flare, clot, aqueous cells, and synechias) in the implanted eye when compared with the control eye in the rabbits. The implants survived for 2 weeks in vivo.     

Influence of chitosan and polycarbophil on permeation of a model hydrophilic drug into the urinary bladder wall

Influence of dispersions of mucoadhesive polymers chitosan and polycarbophil on permeability properties of urinary bladder was investigated in vitro on isolated porcine urinary bladder. Pipemidic acid as a model hydrophilic drug was used. Its distribution in the bladder wall was determined from actual tissue concentrations by a method based on sectioning of frozen tissue and extraction of tissue slices. Pipemidic acid tissue concentration versus tissue depth profiles were evaluated by a diffusion model assuming constant diffusion coefficient. Increase in bladder wall permeability was observed in the presence of both polymers. Apparent permeability (mean+/-S.D.) of urinary bladder wall was increased 2.7+/-2.9 and 2.8+/-2.0 times for chitosan, and 2.3+/-2.0 and 4.3+/-4.2 times for polycarbophil at 0.5 and 1.0%, w/v polymer concentration, respectively. This increase is a consequence of the increased permeability of urothelium. These findings support investigations on application of chitosan and polycarbophil in development of mucoadhesive intravesical drug delivery systems. Experimental model may be applied to evaluate the results of experiments with drugs used in intravesical therapy.     

Preparation and characterization of Mitomycin-C loaded chitosan-coated alginate microspheres for chemoembolization

Mitomycin-C loaded and chitosan-coated alginate microspheres were prepared for use in chemoembolization studies. In this respect, first alginate microspheres were prepared by using a spraying method using an extrusion device with a small orifice and following suspension cross-linking in an oil phase. Chitosan-coating onto the alginate microspheres was achieved by polyionic complex formation between alginate and chitosan. CaCl₂ was used as a cross-linker for alginate microspheres. The obtained chitosan-coated alginate microspheres were spherical shaped and ～100–400?µm average size. The microspheres were evaluated based on their swellability and the swelling ratio was changed between 50–280%. CaCl₂ concentration, stirring rate, chitosan molecular weight, chitosan concentration and time for coating with chitosan were selected as the effective parameters on microsphere size and swelling ratio. Equilibrium swellings were achieved in ～30?min. On the other hand, chitosan molecular weight, chitosan concentration and time for coating with chitosan were found as the most effective parameters on both drug loading ratio and release studies. Maximum drug loading ratio of 65% was achieved with high molecular weight (HMW) chitosan, highest chitosan concentration (i.e. 1.0% v/v) and shortest time for coating with chitosan (i.e. 1?h) values.     

Preparation of chitosan beads by simultaneous cross-linking/insolubilisation in basic pH. Rheological optimisation and drug loading/release behaviour.

A one-step procedure to prepare chitosan beads by simultaneous cross-linking with glutaraldehyde and insolubilisation in 1.5 M NaOH solution has been developed. The optimisation of the procedure was carried out by monitoring the evolution of the loss and storage moduli of chitosan solutions (1.5% (w/v), in acetic acid 0.2 M) in the presence of different proportions of glutaraldehyde. Increasing the chitosan molecular weight, glutaraldehyde concentration and/or process temperature from 20 to 37 degrees C, a reduction of time to reach the gel point was observed. The diameter of freshly prepared swollen beads was 3.2+/-0.4 mm and, after drying 0.48+/-0.18 mm. Swollen or previously dried beads were loaded with metronidazole by immersion in 0.1% (w/v), drug solution in a phosphate buffer pH 7.5, purified water, 0.2 M acetic acid or 0.1 M HCl. Beads synthesised at 37 degrees C experimented faster swelling than the ones prepared at 20 degrees C and even disintegrated in acetic acid. The amounts of metronidazole loaded (ranging from 1 to 286 mg/g dried beads) increased with swelling capacity of beads. The release studies carried out in 0.1 M HCl indicated that, regardless of the medium used to load the beads, all of them released the dose in less than 30 min. In summary, applying this one-step procedure and choosing the adequate glutaraldehyde proportion, it is possible to obtain particles of chitosan cross-linked with itself, which exhibit pH-sensitive swelling and which are able to release all the drug quickly into an acidic environment such as the stomach. The results obtained also highlight the importance of the pH of the medium for modulating the amount of drug loaded (it is remarkably greater at lower pHs) and the influence of temperature at which the beads are prepared on their tendency to disintegrate.     

Encapsulation of olive leaf antioxidants in microbeads: Application of alginate and chitosan as wall materials

Edible microcapsule technology has been declared as a newly developed technology in 21st century by some certain authorities in order to preserve food products. Encapsulation of the bioactive materials in edible coatings is a blessing that can eliminate many undesirable situations that might arise when it is used as additive. In this study, olive leaf extract has been evaluated as active material to prepare microcapsules by using alginate as coating. Ionic gelation was used to produce microbeads. The experimental design of the encapsulation system, the effects of the process parameters, the modeling of the experimental data and the optimization of the conditions were carried out with Box-Behnken design of response surface method (Box-Behnken-RSM). Box-Behnken-RSM produced 17 experimental runs. Calcium chloride (2–15%, w/v) and sodium alginate concentrations (1–2%, w/v), and hardening time (15–45 min) were selected as independent variables, while encapsulation efficiency (EE) of the capsules in terms of total phenolic content (TPC) and oleuropein concentration were responses. Impact of chitosan as coating layer was also investigated with three different ratios of chitosan (0.4%, 0.7%, 1% w/v). Accelerated oxidation test was employed to measure the stability of the microcapsules against oxidation by means of Rancimat method. Encapsulation of the olive leaf extract in alginate microbeads was satisfying with >70% and >90% efficiencies with respect to TPC and oleuropein under optimum conditions (2.34% calcium chloride concentration and 2% sodium alginate for 26 min of hardening time).     

Novel solvent-based method for preparation of alginate beads with improved roundness and predictable size

Attempts to determine conditions or processes within alginate gel beads often suffer from inaccuracies due to an improper roundness of the analysed beads. Therefore, a novel solvent-based method for the preparation of alginate beads with improved shape was developed: An aqueous solution of 2% (w/v) alginate in water was injected into a solvent layering consisting of hexane, n-butanol, n-butanol with 1% (w/v) CaCl2 and finally 2% (w/v) CaCl2 in water. Beads of up to 3.5 mm in diameter obtained with this method had a roundness which was approximately 5% better than comparable beads prepared by dropping an alginate solution into a CaCl2-hardening bath. This was determined by a software supported quantitative analysis of bead size and shape. Additionally, the novel solvent-based method allows for highly reproducible preparation of alginate beads with exactly predictable sizes. The biggest beads obtained with this method were 9 mm in diameter. Thus, with the solvent-based preparation of alginate beads it is now possible to easily obtain beads of exactly the type needed for a specific analytical purpose.     

Preparation of sodium alginate microspheres containing hydrophilic β-lactam antibiotics

Alginate microspheres were prepared by the emulsification process as a drug delivery system of ampicillin sodium (AMP-Na). The preparation parameters such as the concentration of calcium chloride, the stirring time and the amount of AMP-Na were investigated. The alginate microspheres containing hydroxypropylmethylcellulose (HPMC) were found to be generally spherical, discrete and had smoother surfaces when compared to without HPMC. However, there was no significant difference in the release profile of AMP-Na from alginate microspheres prepared with or without HPMC. The concentration of calcium chloride solution and the stirring time in the preparation of alginate microspheres influenced the aggregation of alginate microspheres. The amount of AMP-Na in alginate microspheres influenced the surface morphology and the practical drug content in microspheres.