Calcium alginate microspheres

Brown JQ, Srivastava R, McShane MJ. Encapsulation of glucose oxidase and an oxygen-quenched fluorophore in polyelectrolyte-coated calcium alginate microspheres as optical glucose sensor systems. Biosensors Bioelectronics 2005, 21, 212-216. 

Fig. 8. Spray device for the preparation of calcium alginate microspheres...

It has been shown that a modified drug release can be obtained from calcium alginate microcapsules, pellets, and microspheres. When biodegradable bone implants composed of calcium alginate spheres and containing gentamicin were introduced into the femur of rats, effective drug levels in bone and soft tissue were obtained for 30 days and 7 days, respectively. ... 

Small calcium alginate gel microspheres containing entrapped cells are formed. Like the general procedure, some cells protrude out of the surface of the smaller calcium alginate gel microspheres. These gel microspheres are resuspended in alginate solution to repeat the same droplet formation. 

This entraps the small miciospheres within larger calcium alginate gel microspheres and eliminates cells protruding out of the larger alginate gel microspheres. 

The next two steps are the same as the previous process. In the last step, the entire content of the microcapsule was liquified by citrate. This also liquified the small calcium alginate gel microspheres inside the microcapsule. This way the hepatocytes in the smaller gel microsphere are released to float freely inside the microcapsule. 

The advantage of complex coacervates is that high payloads can be obtained. Chitosan/alginate coacervates have been reported to encapsulate up to 87% shark liver oil, which is rich in omega-3 fatty acids (Peniche et al. 2004). Microspheres of carboxymethyl chitosan/alginate hardened with calcium chloride have been used for encapsulation of up to 80% bovine serum albumin (Zhang et al. 2004). 

In contrast, low-methoxy (LM) pectins gel in the presence of divalent cations, especially calcium, by the egg box mechanism proposed for alginates. Moreover, calcium pectinate gels prepared at neutral pH are heat stable, whereas acidic pH gels are thermo-reversible. Gel strength depends on the extent of esterification (levels from 30% to 50% are optimal), the distribution of ester groups on the chain, and the average molecular weight. LM pectins have been used traditionally in antidiarrheal formulations with kaolin. HM pectins were evaluated in controlled release matrix formulations. Pectin microspheres were reported to improve ophthalmic bioavailability of piroxicam in rabbits compared with commercial piroxicam eye drops. ... 

The gelation technology employs chemical interactions to cause liquid droplets to gel, forming microcapsules or microspheres. This technique is used by the pharmaceutical industry to encapsulate active agents and also to immobilize live cells and organisms. In one process, live cells are first entrapped in gel matrix beads produced by the reaction of sodium alginate with calcium ions. The outer layer of the beads is then hardened by treatment with a polycation to form a polyelectrolyte complex, while the interior of the beads is solubilized by treating with sodium nitrate to form a soluble complex. 

Microsphere beads were prepared with alginate-derived polymeric surfactants in aqueous solution of sodium and calcium chloride [33]. Ibuprofen, a hydrophobic drug, was loaded on the modified alginate beads and the in vitro control release was studied. It was found that drug loading level was higher than those obtained for unmodified alginated with a well controlled release rate [33]. 

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