E.M. Martín Del Valle

Cyclodextrins and their uses: a review

Abstract Cyclodextrins are a family of cyclic oligosaccharides composed of α-(1,4) linked glucopyranose subunits. Cyclodextrins are useful molecular chelating agents. They possess a cage-like supramolecular structure, which is the same as the structures formed from cryptands, calixarenes, cyclophanes, spherands and crown ethers. These compounds having supramolecular structures carry out chemical reactions that involve intramolecular interactions where covalent bonds are not formed between interacting molecules, ions or radicals. The majority of all these reactions are of ‘host–guest’ type. Compared to all the supramolecular hosts mentioned above, cyclodextrins are most important. Because of their inclusion complex forming capability, the properties of the materials with which they complex can be modified significantly. As a result of molecular complexation phenomena CDs are widely used in many industrial products, technologies and analytical methods. The negligible cytotoxic effects of CDs are an important attribute in applications such as rug carrier, food and flavours, cosmetics, packing, textiles, separation processes, environment protection, fermentation and catalysis.

Immobilized Metal‐Ion Affinity Chromatography: Status and Trends

Abstract The correct folding of solubilized recombinant proteins is of key importance for their production in industry. On‐column refolding of proteins is mainly achieved by three methods: size‐exclusion chromatography, ion exchange chromatography and affinity chromatography using immobilized metal chelates. The principles of these methods were first laid down in the 1990s, but many recent improvements have been made to these processes. Immobilized metal‐ion affinity chromatography (IMAC) represents a relatively new separation technique that is primarily appropriate for the purification of proteins with natural surface‐exposed histidine residues and for recombinant proteins with engineered histidine tags or histidine clusters. Because the method has gained broad popularity in recent years, the main recent developments in the field of new sorbents, techniques and possible applications are discussed in this article.

SUPERCRITICAL FLUID TECHNIQUE FOR PARTICLE ENGINEERING: DRUG DELIVERY APPLICATIONS

Supercritical Fluid (SCF) technology is now considered as a very innovative and promising way to design particles, especially for therapeutic drug formulation.(l) The advantages of SCF technology include use of mild conditions for pharmaceutical processing (which is advantageous for labile proteins and peptides), use of environmentally benign nontoxic materials (such as CO2), minimization of organic solvent use, and production of particles with controllable morphology, narrow size distribution, and low static charge(l). SCF technology is making inroads in several pharmaceutical industrial operations including crystallization, particle size reduction, and preparation of drug delivery systems, coating, and product sterilization. It has also been shown to be a viable option in the formulation of paniculate drug delivery systems, such as microparticles and nanoparticles, liposomes, and inclusion complexes, which control drug delivery and/or enhance the drug stability. This review describes the recent advances in the use of SCF technology for particle engineering and for the preparation of drug delivery systems.

Separation of asparaginase and trypsin by affinity chromatography combined with batchwise adsorption and columnwise desorption

Abstract The main goal of this paper was to check experimentally that in affinity chromatography, when porous particles are used, the enzymes inside the particles are partly retained instead of being adsorbed. Trypsin and Asparaginase were separated by affinity chromatography using a combined system with batchwise adsorption and columnwise desorption. The data obtained on specifically and non-specifically adsorbed enzymes were compared with those previously obtained from equilibrium studies. Langmuir-type behaviour was observed for the adsorption of asparaginase. From the isotherms obtained, the adsorption equilibrium constants were determined taking into account the partition coefficient. These constants were compared with those experimental determined from equilibrium studies. The mass balances carried out from the elution process revealed that asparaginase is adsorbed by specific bonds (73% of total bonds), non-specific bonds (27% of total bonds) and partly occluded (38% of the initial concentration). By contrast, trypsin was not adsorbed by specific bonds, but a small amount of occluded enzyme and non-specific bonded enzyme inside the particles was observed. It may thus be concluded that affinity chromatography affords perfect separation of these enzymes.