Chitosan-coated Alginate Beads Research Articles

Chitosan coated alginate beads for the survival of microencapsulated Lactobacillus plantarum in pomegranate juice

This work studied the effect of multi-layer coating of alginate beads on the survival of encapsulated Lactobacillus plantarum in simulated gastric solution and during storage in pomegranate juice at 4°C. Uncoated, single and double chitosan coated beads were examined. The survival of the cells in simulated gastric solution (pH 1.5) was improved in the case of the chitosan coated beads by 0.5–2 logs compared to the uncoated beads. The cell concentration in pomegranate juice after six weeks of storage was higher than 5.5logCFU/mL for single and double coated beads, whereas for free cells and uncoated beads the cells died after 4 weeks of storage. In simulated gastric solution, the size of the beads decreased and their hardness increased with time; however, the opposite trend was observed for pomegranate juice, indicating that there is no correlation between cell survival and the hardness of the beads.

Designing a Highly Efficient Chemical Chaperone System Using Chitosan-Coated Alginate

In the present work we prepared chitosan-coated alginate beads, to use as a chemical chaperone based on the electrostatic interaction between the carboxylate groups of alginate and the ammonium groups of chitosan. This procedure was an attempt for designing a highly efficient chemical chaperone to improve protein stability and refolding. Based on enzyme recovered activity, turbidity, far-UV CD and fluorescence data, alkaline phosphatase can be stabilized and refolded to a higher degree in the presence of alginate capsules compared with unassisted form and was further improved by including chitosan. Finally the maximum yield was obtained when the refolding process was achieved under a well worked out temperature program: incubation of the captured-enzyme for 20 min at 4 degrees C followed by overnight incubation at 22 degrees C, which showed that aggregation is a major limitation to refolding.

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.

Chitosan coated alginate beads containing poly(N‐isopropylacrylamide) for dual‐stimuli‐responsive drug release

Chitosan coated alginate beads containing poly(N-isopropylacrylamide) (PNIPAAM), were prepared to be used as a controlled pH/temperature sensitive drug delivery system with improved encapsulation efficiency and delayed release rate. The studied beads were characterized by differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy. Water uptake and release studies using indomethacin as a model drug were also performed. The drug loading efficiency of the beads with the polyelectrolyte complex coating is significantly higher (84%) than that of the uncoated ones (74%). The equilibrium swelling of the developed materials was found to be pH- and thermo- responsive. For all the conditions it was found that the release profile was slower for the coated beads, indicating that the polyelectrolyte complex coating could slow down the release rate effectively. These results suggest that the studied smart system has potential to be used as an effective pH/temperature sustainable delivery system for biomedical applications.

Studies on the applicability of alginate-entrapped Chryseomonas luteola TEM 05 for heavy metal biosorption

Chryseomonas luteola TEM 05 cells were entrapped both in alginate and chitosan coated alginate beads. Biosorption of metal ions on alginate beads was investigated by using a batch stirred system at pH 6.0, 25 °C, in initial metal concentration of 1.92 mM of Cr 6+, 0.89 mM Cd 2+ and 1.69 mM Co 2+. Then, a process of competitive biosorption of these metal ions was described and compared to single metal ion adsorption in solution. The apparent equilibrium biosorption was reached within the 180 min of contact for all metals. Although the competitive biosorption capacities of the beads for all metal ions were lower than those of single conditions, Cd 2+ biosorption on alginate and alginate–chitosan beads did not change significantly.

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 3 h, 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”.

Survival of probiotics encapsulated in chitosan-coated alginate beads in yoghurt from UHT- and conventionally treated milk during storage

Survival of the microencapsulated probiotics, Lactobacillus acidophilus 547, Bifidobacterium bifidum ATCC 1994, and Lactobacillus casei 01, in stirred yoghurt from UHT- and conventionally treated milk during low temperature storage was investigated. The probiotic cells both as free cells and microencapsulated cells (in alginate beads coated with chitosan) were added into 20 g/100 g total solids stirred yoghurt from UHT-treated milk and 16 g/100 g total solids yoghurt from conventionally treated milk after 3.5 h of fermentation. The products were kept at 4 °C for 4 weeks. The survival of encapsulated probiotic bacteria was higher than free cells by approximately 1 log cycle. The number of probiotic bacteria was maintained above the recommended therapeutic minimum (10 7 cfu g −1) throughout the storage except for B. bifidum. The viabilities of probiotic bacteria in yoghurts from both UHT- and conventionally treated milks were not significantly ( P > 0.05 ) different.

Laccase‐Mediated Remazol Brilliant Blue R Decolorization in a Fixed‐Bed Bioreactor

A crude laccase mixture preparation from Pleurotus ostreatus cultures supplemented with copper and ferulic acid was used to decolorize the anthraquinonic dye Remazol Brilliant Blue R (RBBR). Performance of this enzymatic system was tested, and a maximum of 70% decolorization was achievable under optimal conditions. The crude preparation was immobilized by entrapment in copper alginate beads attaining 65% yield of laccase activity. Stability of the immobilized laccases was remarkably increased in comparison with that of the free enzyme preparation. Efficiency of the immobilized system was evaluated during stepwise dye additions in batch operations. Under the best conditions, 70% RBBR decolorization was achieved even after 20 cycles, although decolorization time exponentially increased after the 10th cycle. Different fixed-bed bioreactors were prepared and analyzed in continuous decolorization processes. The best performance was obtained by decreasing the amount of enzyme loaded and by improving laccase retention using chitosan-coated alginate beads.

The influence of coating materials on some properties of alginate beads and survivability of microencapsulated probiotic bacteria

The probiotics, Lactobacillus acidophilus 547, Bifidobacterium bifidum ATCC 1994, and Lactobacillus casei 01, were encapsulated into uncoated calcium alginate beads and the same beads were coated with three types of material, chitosan, sodium alginate, and poly-l-lysine in combination with alginate. The thickness of the alginate beads increased with the addition of coating materials. No differences were detectable in the bead strength by texture analysis or in the thickness of the beads with different types of coating materials by transmission electron microscopy. The survivability of three probiotics in uncoated beads, coated beads, and as free cells (unencapsulated) was conducted in 0.6% bile salt solution and simulated gastric juice (pH 1.55) followed by incubation in simulated intestinal juice with and without 0.6% bile salt. Chitosan-coated alginate beads provided the best protection for L. acidophilus and L. casei in all treatments. However, B. bifidum did not survive the acidic conditions of gastric juice even when encapsulated in coated beads. r 2004 Elsevier Ltd. All rights reserved.

Matrix molecular weight cut-off for encapsulation of carbonic anhydrase in polyelectrolyte beads

The enzyme bovine carbonic anhydrase (BCA) has been immobilized in the chitosan-alginate system for the first time, to catalyze the conversion of CO2 to HCO3-. Chitosan-coated alginate beads are a biodegradable and environmentally benign matrix, chosen for application of the enzyme in a novel biomimetic CO2 sequestration system. The feasibility of the system and immobilization of the enzyme were demonstrated in our earlier studies [1–3]. Optimization of the matrix to improve the retention time of the enzyme in an encapsulated form is the subject of the present study. The improvement in the molecular weight cut-off of the beads was accomplished by adjusting the crosslinking conditions, coating composition, and molecular weight of the system. The quantity of enzyme released from the system was measured by a Bio-Rad protein assay. Poly-L-lysine was also used as a coating reagent for comparison purposes. The presence of a coating on the alginate beads was verified by Kjeldahl analyses. The difference in the microstructures of alginate and chitosan/alginate beads was demonstrated by SEM studies. Mineralization of the chitosan/alginate matrix in the presence of CaCO3 was also studied by FT-IR, to assess the possibility of using the beads continuously in a bioreactor.

Encapsulation of urease in alginate beads and protection from α-chymotrypsin with chitosan membranes

Urease was encapsulated in alginate beads coated with chitosan, poly-L-lysine or poly(methylene co-guanidine) membrane to exclude α-chymotrypsin and other proteases. Urease in uncoated alginate was highly susceptible to 21.6 kDa α-chymotrypsin, with 98% of the activity lost within 10 min exposure. Chitosan and poly-L-lysine membrane coating provided 50 and 12% activity retention respectively after exposure, while poly(methylene co-guanidine) membrane both inactivated urease and failed to provide protection from protease hydrolysis. Lyophilization of the beads caused shrinkage, and rehydrated beads did not swell to their original diameter, effectively reducing permeability. This was evident through a large improvement in protease exclusion for both chitosan-coated (89% activity retention) and uncoated (71%) beads. Results with trypsin were similar to that observed with α-chymotrypsin, likely due to similarity in molecular weight. A higher level of exclusion and urease protection within chitosan coated alginate beads was observed with higher molecular weight proteinase K.