Microencapsulation achievements

Some of the most remarkable achievements include microencapsulation in polystyrenes such as entrapped 0s04 for olefin hydroxylation (exploiting the interaction between n-electrons of benzene rings of the polystyrenes used as polymer backbones and the vacant orbitals of the catalysts) 5 polyurea-entrapped palladium (PdEnCat)6 for a multiplicity of C C forming reactions and the use of carboxylic acid-functionalized polymer (FibreCat).7 In general, however, metal leaching cannot be avoided. The PdEnCat catalyst, for instance, leaches some 4% of palladium per catalytic reaction run. 

Type 3 metal complexes involve the physical interaction of a metal complex, chelates, or metal cluster with an organic polymer or inorganic high molecular weight compound. The preparation of type 3 compounds differs from those of type 1 and type 2, as they are ultimately achieved through the use of adsorption, deposition by evaporation, microencapsulation, and various other methods. 

A Chromobacterium viscosum lipase is microencapsulated in AOT reversed micelles in isooctane with a Wo=24 and used in the controlled hydrolysis of 50 mM triolein at pH 7.0 and 35°C, in a continous stirred membrane reactor, with a flow rate of 1 l.min 1 Design the reactor in order to achieve 95% of conversion. 

Microcapsules represent an extra degree of freedom in the formulation or development of these food products. Many of the reasons or causes for the use of microcapsules are covered in a previous symposium (1) and a continued updated review on this subject (2). The use of microcapsules is one means of achieving controlled release of the core or inner material. The term controlled release actually covers a wide range of technologies and microencapsulation is one way of achieving controlled release. In fact, microencapsulation is the dominant means for achieving controlled release both in product volume and dollar value. 

The liposomes did not interfere with alginate capsule formation and were retained within the finished capsules. When myoglobin (used as a model protein) was not entrapped within liposomes but was simply enclosed as "free" protein within the coated alginate beads, 60% of it diffused out of the capsule over the first two days. In contrast, delayed release was achieved with microencapsulated liposomes containing myoglobin. Very little myoglobin appeared outside the capsules until 10 days after the start of the release experiment. It required a further 12 days to reach a level of 60% and not until 50 days after the start of the experiment was 100% release achieved. (Figure 5)... 

When the microencapsulated liposomes are left untreated the lipid bilayer provides a barrier to diffusion through which the entrapped protein does not pass until the liposomes gradually become leaky, primarily due to oxidation of the phospholipid side chains. This mechanism results in a delayed release. Triton or sonic treatment of the microencapsulated liposomes provide pulsed re ease. Since both detergent and sonication disrupt lipid bi ayers, the mechanism by which pulsed release is achieved may be that these stimuli initially disrupt the liposomes and then the lipid reforms around some of the protein solution inside the capsule, possibly in an altered lamellar form alternatively, the treatment could disrupt only the more susceptible liposomes, leading to two phases of release, first from the freed protein and later from protein that remained liposome-entrapped. 

In the early 1990s, Fuji Photofilm Ltd. Introduced Copiart 3 proofing materials, which also depended on HABI chemistry. The chemistry used the lower cost o-Cl-HABI and Leuco Crystal Violet along with tribromomethyl phenyl sulfone, which were microencapsulated in selected vehicles. The image stabilization was achieved by a thermal aftertreatment, which ruptured the microcapsules, which then interacted with phenidone, or other reducing agents to prevent subsequent color formation. 

Scher ( ) has reviewed the microencapsulation of pesticides and discussed some of the possible ways of achieving such a delivery system. 

Simple coacervation of cellulose derivatives has been used for microencapsulation of various drugs, such as theophylline, ibuprofen, indomethacin, adryamicin, " and nicardipine. The goal of micro-encapsulating these drugs was to decrease their gastric irritation, mask the bitter taste and, very importantly, to achieve sustained release. 

Fig. 5 shows microencapsulated mice islets intended for intraportal (liver) transplantation to achieve clinical normoglycemia. The islet s p-cells produce insulin in response to a blood glucose stimulus providing a therapeutic alternative to daily insulin injections. The capsule size is optimized to permit oxygen diffusion ... 

Most patients with malabsorption will require pancreatic enzyme supplementation and a reduction in dietary fat in order to achieve satisfactory nutritional status and become relatively asymptomatic. An initial prandial dose of 30,000 international units of lipase (uncoated tablet, capsule, or powder) is recommended to be given with each meal (see Fig. 34—5). Alternatively, the use of microencapsulated enteric-coated dosage forms may be used. The total daily lipase dose should be titrated to reduce steatorrhea. In some patients a reduction in dietary fat may be necessary. The addition of an antisecretory drug should be reserved for patients resistant to enzyme therapy (see Fig. 39-5). If these measures are ineffective, documentation of the diagnosis and exclusion of other diseases should be undertaken. 

Polymers such as polylysine (22,25,57) and dendrimers (26-28), have been shown to promote transfection at least as well as the cationic lipid-delivery systems. Polylysine, like other polycations, condenses plasmid DNA (58,59), which may impart a protective effect against nucleases and possibly improve its eventual activity within the cell. Polylysine can be covalently coupled to targeting peptides, as discussed later, to achieve improved specificity of uptake. Antigenicity of polylysine is not anticipated to be a concern, evidenced by the use of polylysine as a component of the microencapsulation system used to protect live cells in allogeneic transplantation from immune attack (60-62). 

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