Microparticles systems

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

A number of patented technologies for multiparticulate dosage forms have been described recently, such as the Micropump system, which is an osmotically driven coated microparticle system designed to increase the absorption time for rapidly absorbed drugs.59 Combination of water-soluble and water-insoluble polymers could provide enhanced controlled release rates and profiles. A patented technology (COSRx) has been reported to be capable of delivering various sophisticated release profiles. The formulation involves a guar-gum-based tablet and a combination of water-soluble and water-insoluble polymeric tablet coat.60... 

Controlled crosslinking of cationic starches improves performance in microparticle-containing papermaking systems.84-86 Superior performance over cationic potato starch was achieved with crosslinked cationic or amphoteric waxy maize, tapioca or potato starch in microparticle systems when the starch cooking was optimized to produce the proper colloidal dispersions.86... 

A novel sizing strategy utilizes a microparticle system that enhances retention.166 A representative example is a combination of cationic potato starch (DS = 0.04), a metallosilicate hydrosol and AKD. In an approach to combine elevated filler retention, effective sizing and high paper strength, calcium carbonate is reacted with a starch-soap complex and combined with AKD.167168... 

The microparticle system has become an indispensable part of the controlled drug delivery fields for the past few decades since it can readily be adapted for various administration methods. In particular, biodegradable polymeric microparticles can provide a number of advantages over conventional parenteral formulations ... 

With the recent advance of biotechnology and polymer chemistry, the use of microparticle systems will continue to grow for a variety of applications. The objective of this article is to provide a review of the technical aspects of the microencapsulation techniques that have been widely used in the pharmaceutical industry and recent advances of the technology so that the pharmaceutical scientists can take full advantage of the existing assets of this area in developing new microparticle systems. 

Despite the extensive use of PLGA polymers in the microencapsulation arena, it has been found through decades of research that the PLGA microparticle systems are not universally suited for different applications. One of the limitations in the prevalent PLGA systems is that bulk hydrolysis of the polymer induces acidification of microenvironment of the microparticles, which can be detrimental to various payloads such as proteins and nucleic acids. In addition, their drug release kinetics are not readily tunable and, thus, are inappropriate for specific applications.f ... 

Drug release from biodegradable polymer microparticles is determined by the polymer degradation kinetics, structural features of the microparticles, and distribution of the drugs within the particle matrix. The ultimate goal of microparticle systems in the controlled drug delivery is to achieve readily tunable release profiles, which has been pursued in various perspectives. 

Use of microparticle systems is not limited to the sustained or local delivery and has a wide range of applications. A limited number of examples are introduced below. 

Yeo, Y. Park, K. Control of encapsulation efficiency and initial burst in polymeric microparticle systems. Arch. Pharmacol. Res. 2004, 27 (1), 1-12. 

Microparticle systems - starch and or polymer with sihca microparticle (in various... 

Microparticle systems - polymer with bentonite (in various orders of addition)... 

Calcium-alginate and calcium-yam-alginate, methylated N-ii-NJ / dimethylaminocinnamyl) chitosan (TM65CM CS) was used to coat microparticles Wheat germ agghitiiiin (WGA)-aiichored salmeterolxinafoatefSalX)-loaded nanoparticles-in-microparticles system (NiMS)... 

Finally, the glucose-stimulated release of physiologically relevant amounts of entrapped insulin from the microparticle system was demonstrated... 

Starch 2 wt% PAA 0-D.08 wt% Classical dual systems are both less reversible and show a lower dewatering compared with microparticle systems [19]... 

Although PLGA has been shown to be extremely safe as a material for macroscopic and microparticle systems, unique considerations may arise when using nanoscale applications. Several studies suggest that nanoparticles of any material may create specific biodistribution and toxicological profiles [87]. 

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