In vitro evaluation of chitosan coated- and uncoated-calcium alginate beads containing methyl salicylate-lactose physical mixture

Context: Methyl salicylate–lactose physical mixture (1:1 and 1:1.5 ratios) was incorporated into calcium alginate beads by a coacervation method involving an ionotropic gelation/polyelectrolyte complexation approach.

Objectives: This study aims to determine the influence of chitosan coating over the beads on drug entrapment efficiency (DEE) and release characteristics in artificial saliva compared to that of the uncoated beads.

Results and discussion: Changes in formulation parameters (gelation time, concentrations of Ca²⁺ and alginate) resulted in decrease in DEE of chitosan-uncoated beads (p?<?0.05). This is due to the combined effects of drug leach-out from the physical mixture by Ca²⁺ ions, alginate gel matrix cross-linking and free drug diffusion from chitosan-uncoated beads. However, an increment in the DEE was seen for chitosan-coated beads. A rapid drug release profile was noted for uncoated beads, but for chitosan-coated beads a sustained release profile was depicted depending upon the coating conditions. Chitosan-coated beads had reduced swelling and erosion properties and thus behaved as a physical barrier to drug release. Shifting from anomalous transport type to Fickian transport confirmed the formation of physical barrier onto chitosan-coated beads.

Conclusion: Calcium alginate beads could be used as a controlled-release system for methyl salicylate–lactose physical mixture.     

Swelling studies and in vitro release of verapamil from calcium alginate and calcium alginate-chitosan beads

The aim of the present work was to investigate the swelling behavior and the in vitro release of the antihypertensive drug verapamil hydrochloride from calcium alginate and chitosan treated calcium alginate beads. Calcium-alginate beads, chitosan-coated alginate beads and alginate-chitosan mixed beads were synthesized and their morphology was investigated by scanning electron microscopy. The swelling ability of the beads in different media was found to be dependent on the presence of the polyelectrolyte complex between alginate and chitosan, the pH of the aqueous media and the initial physical state of the beads. The results revealed that the encapsulation of verapamil in both calcium-alginate and calcium alginate-chitosan mixed beads exceeded 80%. Considering the in vitro stability of verapamil encapsulating beads, 70% of the drug released from wet and dry plain calcium alginate beads within 1 and 3h, respectively. The presence of chitosan was found to retard significantly the release from wet beads. However, in the case of dry beads the presence of chitosan had no significant effect on the initial release stage and significantly increased the release on the later stage. The results were analyzed by using a semi-empirical equation and it was found that the drug release mechanisms were either "anomalous transport" or "case-II transport".     

A Novel Approach to the Oral Delivery of Micro- or Nanoparticles

A novel oral multiple-unit dosage form which overcame many of the problems commonly observed during the compression of microparticles into tablets was developed in this study. Micro- or nano-particles were entrapped in beads formed by ionotropic gelation of the charged polysaccharide, chitosan or sodium alginate, in solutions of the counterion, tripolyphosphate (TPP) or calcium chloride (CaCl₂), respectively. The described technique did not change the physical properties of the microparticles, and it allowed a high microparticle loading (up to 98%). The ionic character of the polymers allowed pH-dependent release of the microparticles. Chitosan beads disintegrated and released the microparticles in 0.1 N HC1, while calcium alginate beads stayed intact in 0.1 N HC1 but rapidly disintegrated in simulated intestinal fluids. Coating the calcium alginate beads with cellulose acetate phthalate resulted in an enteric drug delivery system. Scanning electron microscopy and dissolution and disintegration tests were used to characterize the microparticle-containing beads. The disintegration time of the beads was studied as a function of the solution viscosity of the polysaccharide, gelation time, counterion concentration, and method of drying.     

Sustained release of antineoplastic drugs from chitosan-reinforced alginate microparticle drug delivery systems

Alginate based microparticle drug delivery systems were prepared for the sustained release of antineoplastic drugs. Two drugs, 5-fluorouracil (5-FU) and tegafur, were encapsulated into the microparticles. The drug loaded microparticles were fabricated using a very convenient method under very mild conditions, i.e., directly shredding the drug loaded beads into microparticles in a commercial food processor. The mean sizes of the obtained microparticles were between 100 and 200 μm. To effectively sustain the drug release, alginate microparticles were reinforced by chitosan during gelation. The drug release from the chitosan-reinforced alginate microparticles was obviously slower than that from the unreinforced microparticles. The effect of the reinforcement conditions on the drug release property of the microparticles was studied, and the optimized concentration of chitosan solution for reinforcement was identified. The effects of drug feeding concentration and pH value of the release medium on the drug release were investigated.     

Fabrication of cross-linked alginate beads using electrospraying for adenovirus delivery

Cross-linked alginate beads containing adenovirus (Ad) were successfully fabricated using an electrospraying method to achieve the protection and release of Ad in a controlled manner. An aqueous alginate solution containing Ad was electrosprayed into an aqueous phase containing a cross-linking agent (calcium chloride) at different process variables (voltages, alginate concentrations, and flow rates). Alginate beads containing Ad were used for transduction of U343 glioma cells and the transduction efficiency of the alginate beads was measured by quantification of gene expression using a fluorescence-activated cell sorter at different time points. In vitro results of gene expression revealed that the Ad encapsulated in the alginate beads with 0.5 wt% of alginate concentration exhibited a high activity for a long period (over 7 days) and was released in a sustained manner from the alginate beads. The Ad-encapsulating alginate beads could be promising materials for local delivery of Ad at a high concentration into target sites.     

Lactoferrin-Loaded Alginate Microparticles to Target Clostridioides difficile Infection

Some forms of bovine lactoferrin (bLf) are effective in delaying Clostridioides difficile growth and preventing toxin production. However, therapeutic use of bLf may be limited by protein stability issues. The objective of this study was to prepare and evaluate colon-targeted, pH-triggered alginate microparticles loaded with bioactive bLf and to evaluate their anti-C difficile defense properties in vitro. Different forms of metal-bound bLf were encapsulated in alginate microparticles using an emulsification or internal gelation method. The microparticles were coated with chitosan to control protein release. In vitro drug release studies were conducted in pH-simulated gastrointestinal conditions to investigate the release kinetics of encapsulated protein. No significant release of metal-bound bLf was observed at acidic pH; however, on reaching simulated colonic pH, most of the encapsulated lactoferrin was released. The application of bLf (5 mg/mL) delivered from alginate microparticles to human intestinal epithelial cells significantly reduced the cytotoxic effects of toxins A and B as well as bacterial supernatant on Caco-2 and Vero cells, respectively. These results are the first to suggest that alginate-bLf microparticles show protective effects against C difficile toxin-mediated epithelial damage and impairment of barrier function in human intestinal epithelial cells. The future potential of lactoferrin-loaded alginate microparticles against C difficile deserves further study.     

Multilayer alginate/protamine microsized capsules: encapsulation of alpha-chymotrypsin and controlled release study

Stable polyelectrolyte microcapsules with size 6.5 microm were produced by means of the layer-by-layer adsorption of sodium alginate and protamine to surface of melamine formaldehyde microparticles. Core decomposition at low pH leads to formation of polyelectrolyte multilayered capsules filled with alginate gel. A proteolytic enzyme, alpha-chymotrypsin, was loaded into these microcapsules by embedding in alginate gel with high efficacy. The protein in the capsules was found to retain a high physiological activity of about 70% showed with fluorescent product. The protein was found to keep inside the microcapsules in water and acid (HCl solution, pH 1.7) during 24 and 4 h, respectively, while 75-85% of protein can be revealed in supernatant after 6 h incubation at pH 8.0 (0.05 M Tris buffer) in the presence of 2.5% w/v of sodium deoxycholate. The release rate of enzyme from multilayer alginate/protamine microcapsules can be regulated by additional adsorption of polyelectrolytes onto the microcapsules with encapsulated protein. Such protein-loaded capsules can be proposed as a drug delivery system with controllable release properties.     

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。     

载有酮洛芬-乙基纤维素缓释固体分散体的海藻酸钙小珠的制备

目的:制备酮洛芬-乙基纤维素固体分散体并将其包载于海藻酸钙小珠中,以期制备酮洛芬缓释微丸制剂.方法:采用一种新的溶剂萃取共沉淀法制备固体分散体,差示扫描量热法进行固体分散体物相分析;离子胶凝法将固体分散体包载进海藻酸钙小珠,扫描电子显微镜分析其形态,并考察其体外释药特性.结果:差示扫描量热分析证实药物以非晶型分散于载体中,较低的药物损失率和简便操作证明这种制备方法是可行的,固体分散体具有缓释效果,使用海藻酸钙小珠包载后,降低了在释放介质中的突释性.结论:本方法制备酮洛芬-乙基纤维素缓释固体分散体可行,海藻酸钙包载后降低了释放介质中的突释.     

Novel preparation techniques for alginate-poloxamer microparticles controlling protein release on mucosal surfaces

The objective of this study was to develop novel preparation techniques for protein-loaded, controlled release alginate-poloxamer microparticles with a size range suitable for pulmonary administration. Bovine serum albumin (BSA)-loaded microparticles were prepared by spray-drying aqueous polymer-drug solutions, followed by cross-linking the particles in aqueous or ethanolic CaCl(2) or aqueous ZnSO(4) solutions. The microparticles were characterized with respect to their morphology (optical and scanning electron microscopy), particle size (laser light diffraction), calcium content (atom absorption spectroscopy), alginate content (complexation with 1,9-dimethyl methylene blue) and in vitro drug release (modified Franz diffusion cell). The spray-dried microparticles were spherical in shape with a size range of 4-6μm. Aqueous cross-linking led to a significant size increase (10-15μm), whereas ethanolic cross-linking did not. The substantial drug loss (～50%) during aqueous CaCl(2) cross-linking could be avoided by using aqueous ZnSO(4) or ethanolic CaCl(2) solutions. Protein release from microparticles cross-linked with ethanolic CaCl(2) solutions was much faster than in the case of aqueous CaCl(2) solutions, probably due to the lower calcium content. The salt concentration and temperature of the cross-linking solutions also affected the composition of and drug release from the microparticles. Cross-linked alginate-poloxamer microparticles can be produced in a size range appropriate for deep lung delivery and with controlled protein release kinetics (time frame: hours to days) with these novel preparation techniques. The systems offer an interesting potential for the controlled mucosal delivery of protein drugs.     

Floating dosage forms to prolong gastro-retention--the characterisation of calcium alginate beads

Floating calcium alginate beads, designed to improve drug bioavailability from oral preparations compared with that from many commercially available and modified release products, have been investigated as a possible gastro-retentive dosage form. A model drug, riboflavin, was also incorporated into the formula.

The aims of the current work were (a) to obtain information regarding the structure, floating ability and changes that occurred when the dosage form was placed in aqueous media, (b) to investigate riboflavin release from the calcium alginate beads in physiologically relevant media prior to in vivo investigations.

Physical properties of the calcium alginate beads were investigated. Using SEM and ESEM, externally the calcium alginate beads were spherical in shape, and internally, air filled cavities were present thereby enabling floatation of the beads. The calcium alginate beads remained buoyant for times in excess of 13 h, and the density of the calcium alginate beads was <1.000 g cm⁻³. Riboflavin release from the calcium alginate beads showed that riboflavin release was slow in acidic media, whilst in more alkali media, riboflavin release was more rapid.

The characterisation studies showed that the calcium alginate beads could be considered as a potential gastro-retentive dosage form.     

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。     

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.     

Development and evaluation of polyethyleneimine-treated calcium alginate beads for sustained release of diltiazem

The objective of this investigation is to develop a multi-unit sustained release dosage form of a water soluble drug from a completely aqueous environment avoiding the use of any organic solvent. The drug was complexed with resin and calcium alginate or polyethyleneimine-treated calcium alginate beads loaded with the resinate were prepared by a ionic/polyelectrolyte complexation method. The effect of different formulation variables on the characteristics of the beads was investigated. Although the drug release from spherical and smooth-surfaced calcium alginate beads in both acidic and alkaline dissolution media were slower than those obtained from plain resinate, none of the variables were found to prolong the drug release considerably due to rapid swelling and disintegration of calcium alginate beads in alkaline medium. On the other hand, drug release from polyethyleneimine-treated calcium alginate beads in acidic medium did not increase appreciably following a burst release. However, in alkaline medium, the drug release was found to increase gradually and extend over a different period of time depending on the intensity of polyethyleneimine treatment. Scanning electron micrographs revealed the formation of a dense membrane around the resinate-loaded calcium alginate matrix. The membrane appeared to be responsible for reduced swelling and protracted disintegration of the beads resulting in slow release of the drug. The results indicate that sustained release of a water soluble drug from polyethyleneimine-treated calcium alginate beads could be achieved by adjusting the formulation variables.     

Development and evaluation of polyethyleneimine-treated calcium alginate beads for sustained release of diltiazem

The objective of this investigation is to develop a multi-unit sustained release dosage form of a water soluble drug from a completely aqueous environment avoiding the use of any organic solvent. The drug was complexed with resin and calcium alginate or polyethyleneimine-treated calcium alginate beads loaded with the resinate were prepared by a ionic/polyelectrolyte complexation method. The effect of different formulation variables on the characteristics of the beads was investigated. Although the drug release from spherical and smooth-surfaced calcium alginate beads in both acidic and alkaline dissolution media were slower than those obtained from plain resinate, none of the variables were found to prolong the drug release considerably due to rapid swelling and disintegration of calcium alginate beads in alkaline medium. On the other hand, drug release from polyethyleneimine-treated calcium alginate beads in acidic medium did not increase appreciably following a burst release. However, in alkaline medium, the drug release was found to increase gradually and extend over a different period of time depending on the intensity of polyethyleneimine treatment. Scanning electron micrographs revealed the formation of a dense membrane around the resinate-loaded calcium alginate matrix. The membrane appeared to be responsible for reduced swelling and protracted disintegration of the beads resulting in slow release of the drug. The results indicate that sustained release of a water soluble drug from polyethyleneimine-treated calcium alginate beads could be achieved by adjusting the formulation variables.     

水相-水相乳化法制备载BSA的葡聚糖微粒

目的采用水相-水相乳化法,制备粒径小且分布集中的载蛋白的葡聚糖（Dx）微粒。方法Dx／聚乙二醇（PEG）双水相系统将蛋白富集于Dx相,两相按比例混匀得PEG包Dx型类乳液。添加海藻酸钠于PEG相作稳定剂,经冻干、除PEG后,得载牛血清白蛋白（BSA）的Dx微粒。采用显微镜及软件分析微粒外观和粒径数据,BCA法测定微粒的包封率和载药量,差示扫描量热器测定微粒及其成分的熔融吸热峰。结果优化的载药微粒圆整均一、平均粒径约5um,载药量、包封率分别在16％、88％以上。结论水相一水相乳化法可制备出粒径小且分布集中、载药性能良好的蛋白-Dx微粒。该法可进一步应用于干粉吸人剂或缓释微球等剂型的研究。     

Fabrication of novel core-shell hybrid alginate hydrogel beads

Novel hybrid alginate hydrogel beads with shells of porous CaCO3 microparticles were fabricated by templating water-in-oil emulsion and subsequent in situ gelation. Porous CaCO3 microparticles were self-assembled at interfaces of water-in-oil emulsion. Water droplets containing alginate in the emulsion were subsequently in situ gelated by Ca2+ released from CaCO3 through decreasing pH with slow hydrolysis of d-glucono-delta-lactone (GDL). The resulting hybrid beads with alginate gel cores and shells of porous CaCO3 microparticles were called colloidosomes. The packed density of CaCO3 microparticles in the shell increased with increasing the ratio of the CaCO3 microparticle weight to the water phase volume Mp/Vw and decreased with addition of NaCl into water. The size of the produced colloidosome beads was independent of Mp/Vw. Increasing the volume fraction of water Phi w to 0.5, some colloidosome beads deformed to nonspheral shape and even broken. Brilliant blue (BB) as a drug model was loaded into the colloidosome beads by being dissolved in the alginate aqueous solution before gelation. The BB release from the colloidosome beads was slowed down because of the formation of the shells of CaCO3 microparticles. The colloidosome beads may find applications as delivery vehicles for drugs, cosmetics, food supplements and living cell.     

The effect of solvent removal conditions on performance and release property of protein-loaded microparticles

This study was designed to investigate the influence of solvent removal conditions on the performance and release properties of protein-loaded poly(epsilon-caprolactone) microparticles. The microparticles were prepared by the coacervation method in three different conditions. The effects of vacuum pressure, fabrication temperature and evaporation time on the crystallinity, surface morphology, particle size as well as the yield of microparticles, encapsulation efficiency of BSA and in vitro release property were investigated. There was no significant difference in the size of microparticles prepared by varying the vacuum pressure and temperature. Similar results were obtained for the production yield of microparticles and the loading efficiency of protein in these microparticles. However, accelerating the evaporation rate of solvent significantly reduced the crystallinity of polymer from 54.13 +/- 2.67% down to 44.64 +/- 2.17% (p < 0.05). The release of protein from the resulting microparticles was rapid, within 6 h, after which BSA was continuously and slowly released for up to 7 days. The protein release rate and polymer crystallinity possessed a good correlation (r = -0.951). This result indicated that the higher the crystallinity, the slower the release rate. In other words, change in vacuum pressure and temperature reduced the crystallinity of polymer, which was feasible for protein to release from amorphous domain in microparticles.     

Comparison of the pharmaceutical properties of sustained-release gel beads prepared by alginate having different molecular size with commercial sustained-release tablet

Spherical alginate gel beads containing pindolol were prepared using three types of sodium alginate with different molecular size. The rate of gelation of sodium alginate in calcium chloride solution was in the range of 1.0 to 1.3 h-1 among the used three alginates, but the amount of water squeezed from the alginate gel beads during gelation increased from 5 to 40% with increasing molecular size of the alginate. The beads prepared were similar in diameter (1.2 mm after drying), weight (0.9 mg/bead), calcium content (27-29 micrograms/bead) and pindolol content (40-45%). Pindolol was rapidly released from all the alginate gel beads at pH 1.2 owing to the high solubility of pindolol, in spite of non-swelling of beads. On the other hand, pindolol release from alginate gel beads at pH 6.8 was dependent on the swelling of the beads and was significantly depressed compared to drug powder. Interestingly, the release rate of pindolol and the swelling rate of beads were markedly slow for gel beads prepared by low molecular size alginate. However, when the alginate gel beads were administered orally to beagle dogs, the serum levels of pindolol showed sustained-release profiles, depending on the molecular size of the alginate. The in vivo absorption of pindolol from alginate gel beads did not reflect their in vitro release profiles, because of a physical strength of beads in the intestinal tract. Furthermore, the in vivo and in vitro release of pindolol from alginate gel beads were compared with a commercial sustained-release tablet, Carvisken showed a rapid release of 50% of content in pH 1.2 fluid and residual 50% of pindolol were easily dissolved at pH 6.8. Although the release characteristics of pindolol from Carvisken and the alginate gel beads were completely different, the serum levels of pindolol in human volunteers were comparable.     

Controlling protein release from scaffolds using polymer blends and composites.

We report the development of three protein loaded polymer blend and composite materials that modify the release kinetics of the protein from poly(dl-lactic acid) (P(dl)LA) scaffolds. P(dl)LA has been combined with either poly(ethylene glycol) (PEG), poly(caprolactone) (PCL) microparticles or calcium alginate fibres using supercritical CO(2) (scCO(2)) processing to form single and dual protein release scaffolds. P(dl)LA was blended with the hydrophilic polymer PEG using scCO(2) to increase the water uptake of the resultant scaffold and modify the release kinetics of an encapsulated protein. This was demonstrated by the more rapid release of the protein when compared to the release rate from P(dl)LA only scaffolds. For the P(dl)LA/alginate scaffolds, the protein loaded alginate fibres were processed into porous protein loaded P(dl)LA scaffolds using scCO(2) to produce dual release kinetics from the scaffolds. Protein release from the hydrophilic alginate fibres was more rapid in the initial stages, complementing the slower release from the slower degrading P(dl)LA scaffolds. In contrast, when protein loaded PCL particles were loaded into P(dl)LA scaffolds, the rate of protein release was retarded from the slow degrading PCL phase.