Starch microspheres

Schroder, U., Lager, C., and Norrlow, O., Carbo-lactic microspheres Graft polymerization of PLA to starch microspheres, Proc. Int. Control. Rel. Bioact. Mater.. 14, 238,... 

Starch is usually derivatized by the introduction of acrylic groups, prior to polymerization and manufacture into microspheres. Poly(acryl) starch microspheres, as they are referred to, are an example of a semisynthetic polymer system. Their extensive use as... 

Chemoembolization with microencapsulated drugs has been in clinical use since 1978 [6]. Using biodegradable starch microspheres containing anticancer drugs which occlude selected arteries, anticancer drugs can be locally released upon the degradation of starch by serum amylases [333, 334]. 

Ilium, L., et al. 2001. Bioadhesive starch microspheres and absorption enhancing agents act synergistically to enhance the nasal absorption of polypeptides. Int J Pharm 222 109. 

A temporary widening of the tight junctions of cultured cells, which coincided with an increase in the rate of absorption of the applied drug, insulin, has been observed in the presence of starch microspheres. It is likely that the dry starch microspheies took up water from the cells causing them to dehydrate and shrink resulting in a separation of the intercellular junctions. Should this be the case, it provides evidence for the paracellular absorption of insulin. 

Biodegradable starch microspheres, 40 pm in diameter, were shown to be capable of enhancing the vaginal absorption of insulin. The effect was further enhanced when the penetration enhancer lysophosphatidylcholine was used. 

Work in this field has concentrated on the use of poly(lactide-co-glycolide) microparticles, which have the advantages of being biocompatible, biodegradable and well tolerated in humans. Promising results have also been obtained with the use of biodegradable starch microspheres in conjunction with the absorption enhancer lysophosphatidylcholine. 

FIGURE 17 Morphine plasma concentration after nasal administration of morphine formulations in sheep Mor Sol, morphine solution Mor Chi Sol, morphine solution containing chitosan Mor Chi PWD, morphine chitosan powder Mor SMS LPC, starch microspheres with lysophosphatidylcholine and morphine as a freeze-dried powder. (Reproduced from ref. 105 with permission of the American Society for Pharmacology and Experimental Therapeutics.)... 

The use of degradable starch microspheres has proved to be well tolerated in both experimental animals and humans. No alterations of nasal mucosa were detected after eight weeks of nasal administration of starch microspheres to rabbits. Additionally, a preliminary test on healthy volunteers also showed good acceptability [62], Another study of healthy volunteers revealed no changes in mucociliary clearance or in the geometry of the nasal cavities after eight days of nasal administration of dry starch microspheres [87],... 

Bjork, E., and Edman, P. (1988), Degradable starch microspheres as a nasal delivery system for insulin, Int. I. Pharm., 47,233-238. 

Nakamura et al. ° studied the adhesion of water-soluble and neutral polymers, hydroxypropyl cellulose (HPC), xanthan gum (XG), tamarind gum (TG), and polyvinyl alcohol (PVA) to nasal mucosa in vitro and in vivo. The polymers, mixed with a dye, were applied as powders to the nasal cavity of rabbits, and the remaining dye residue was determined at 2, 4, and 6 h after nasal instillation with a thin fiberscope. The polymer XG showed the longest residence time of the dye in the cavity, followed by TG, HPC, and PVA in decreasing order. For the mixture XG and XG-PVA (2 8), some residue of dye could still be observed 6h after administration. The order of adhesion of these polymers to agar plates in vitro agreed with that of their mucoadhesion in vivo. Ilium et al. introduced bioadhesive microspheres for nasal delivery of poorly absorbable drugs. Radiolabelled microspheres made from diethylaminoethyl (DEAE)-dextran, starch microspheres, and albumin microspheres were administered to human volunteers and appeared to be cleared significantly slower than solutions or... 

To increase the residence time in the nasal mucosa, a bioadhesive formulation may be one of the most reasonable approaches. In fact, microspheres containing bioadhesive polymers such as starch, albumin, and Sephadex with a particle size of 40-60 pm have been found to be cleared from the nasal cavity much more slowly than solutions. Starch microspheres improved the nasal absorption of insulin, with synergistic effects of some absorption enhancers in sheep. In another paper, dry powder containing starch and Carbopol 974P showed significantly higher bioavailability after nasal administration than the formulation without Carbopol. ° Chitosan, already mentioned above, also has a bioadhesive property and is found to be useful as a potent absorption enhancer for nasal peptide delivery. Other bioadhesive polymer systems,... 

Woo BH, Jiang G, Jo YW, DeLuca PP. Preparation and characterization of a composite PLGA and poly(acryloyl hydro-xyethyl starch) microsphere system for protein delivery. Pharm Res 2001 18 1600-1606. 

Shiba, H. Okamato, T. Fugawa, Y. Misawa, T. Yanaga, K. Ohashi, T. Eto, Y. Adenovirus vector-mediated gene transfer using degradable starch microspheres for hepatocellular carcinoma in rats. J. Surg. Res. 2006,133 (2), 193-196. 

Fundueanu G, Constantin M, Ascenzi P, Simionescu BC. An intelligent multicompartmental system based on thermo-sensitive starch microspheres for temperature-controlled release of drugs. Biomedical Microdevices. August 2010 12(4) 693-704. PubMed PMID 20414809. 

Fabrication Common preparation techniqnes discussed in earlier sections are nsed in formnlating bioadhesive microspheres. An important criterion is the use of bioadhesive polymers like chitosan, hyaluronic acid, starch, lysophosphatidylcholine along with degradable starch microspheres. 

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