Proteins microspheres

One of the simplest methods of attaching biomolecules to hydrophobic polymeric particles is the use of passive adsorption. Some of the earliest examples related to the use of particles in immunoassays include the use of non-covalently adsorbed antibody or antigen onto latex microspheres. Protein adsorption onto hydrophobic particles takes place through strong interactions... 

Tracy, M. A. (1998), Development and scale-up of a microsphere protein delivery system, Biotechnol. Prog., 14,108-115. 

Lu, W., and Park,T. G. (1995), Protein release from poly(lactic-co-glycolic acid) microspheres Protein stability problems, PDA J. Pharm. Sci. Technol., 49,13-19. 

Kim HK, Park TG. Microencapsulation of human growth hormone within biodegradable polyester microspheres protein aggregation stability and incomplete release mechanism. Biotechnol Bioeng 1999 65(6) 659-667. 

Appiications adjuvants, bone replacement, controlled drug delivery, corrosion protection, chemotherapy, curing agent, implants (e.g., antibiotic delivery), microspheres (protein delivery), paper, vaccine delivery ... 

Kim, H.K., Park, T.G. Microencapsulation of human growth hormone within biodegradable polyester microspheres Protein aggregation stability and incomplete release mechanism. Biotechnol. Bioeng. 65(6), 659-667 (1999). doi 10.1002/ (sid)1097-0290(19991220)65 6<659 aid-bit6>3.0.co 2-9... 

In most cases the microspheres were insoluble. The polysaccharides might be partially cross-linked via amido groups formed by the carboxyl groups of the polyanion and the restored free amino group of chitosan. The susceptibility to enzymatic hydrolysis by lysozyme was poor, mainly because lysozyme, a strongly cationic protein, can be inactivated by anionic polysaccharides [207]. 

PEG/PBT copolymers are also very good matrix materials for the release of growth factors in tissue engineering. Proteins have been delivered from PEG/PBT microspheres with preservation of protein delivery of complete activity. In the case of protein delivery from PLGA and poly(ortho ester) microspheres, the protein activity was significantly reduced. " ... 

It appears that none of these process techniques is dominant, at least with the lactide/glycolide materials. Researchers have considerable choices available in regard to fabrication of microspheres from these polymers. The most commonly used procedures employ relatively mild conditions of pH and temperature and are usually quite compatible with the bioactive agents to be entrapped, including proteins and other macromolecules. Only in the case of live virus and living cell encapsulation have serious deactivation problems been encountered and those problems were due to solvents used in the process. 

As discussed earlier, noncollagenous proteins, particularly albumin and to a lesser extent gelatin, in the form of microspheres and nanoparticles continue to be exploited as drug delivery systems. Oppen-heim (71) and Speiser (72) reviewed the technology developed to produce ultrafine particles, often referred to as nanoparticles. 

Prior to the study by Chen et al. (140), only one publication discussed the use of the protein casein as a drug carrier (141). Chen et al. systematically compared the many features of albumin and casein microspheres—morphology, drug (adriamycin) incorporation, and release—in an effort to identify important factors in the antitumor effect of this delivery system. 

The culture broth was recovered after 72 h of fermentation, the biomass removed and the total protein content measured. Broth aliquots with a protein content of 1 mg were collected and their pH regulated at different values ranging from 3.5 to 8.0. To each broth fraction, 50 mg of the microspheres sample, previously equilibrated at the corresponding pH, was added and the suspension left under stirring overnight. Then, the microspheres were removed by centrifugation and the protein content and the PG activity were assayed on the resulting supernatant. 

Several scouting experiments were performed to find the best pH conditions. Figure 3 reports the ratio between the PG specific activity measured after the purification procedure (ASf) and the initial PG specific activity (ASi). At pH 3.5, the microspheres are able to remove from the broth the major part of the protein without PG activity, thus providing a four time increase of the enzyme specific activity. The purified PG from Kluyveromyces marxianus was immobilised following the above procedure. Batch reactions in the packed bed reactor were done to evaluate the biocatalyst stability. After an initial loss, due to enzyme release, the residual PG activity reaches a plateau value corresponding to about 40% of the initial activity. Probably, some broth component interfered during the immobilisation reaction weakening the protein-carrier interactions. 

With these principles in mind, we refer the reader to valuable recent reviews, original reports, and discussions [65-68] of probes consisting of proteins, organic dyes, and nanoparticles such as quantum dots (QDs, [2, 68-77]) and other intriguing particles plastic microspheres and nanoparticles [78], multifunctional encoded particles [79], nanodisk codes [80], nano-flares [81], E-PEBBLES [82], C-dots [83], nanocrystal (NC)-encoded microbeads... 

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