Polymer micelles dialysis method

Several methods for effective solubilization of drugs into polymer micelles have been developed (Fig. 2). The dialysis method (Fig. 2A) is most widely used for many polymeric micelle systems. The first step involves the dissolution of both polymer and drug in a water-miscible organic solvent such as acetonitrile, acetone, dimethylformamide, or ethanol. Then, the polymer-drug solution is dialyzed against water. As the organic... 

Figure 18.4 Polymer micelles. Drug loading of polymer micelles by (a) dialysis and (b) oil-inwater emulsion method [27].

Binding ratios of SDS (BHD Ltd.) and CPC (Tokyo Kasei Ltd.) to HPC (M.W. =11 -I5xl0 Tokyo Kasei Ltd.) were determined at 30 °C by an equilibrium dialysis method. Cloud point of an HPC solution was observed by the naked eye. Amounts of p-dimethylaminoazobenzene (Nakarai Ltd.) solubilized by the surfactant micelle and the surfactant-polymer complex were determined at 30 °C by colorimetry at 1 = 418 nm. Viscosity was measured by an Ubbelohde-type capillary viscometer, a cone-plate rotary viscometer, or a Brookfield-type rotary viscometer at 25 or 30 °C. Mean diameter of secondary particles of kaolinite in its dilute suspension (1 g/dl) was estimated by a Coulter counter (type TA-II) in 154 mmol/dm NaCl at room temperature. 

Polymeric micelles Poloxamer-like block copolymers PEG and lipophilic polymer copolymers PEGylated lipids Dialysis, emulsification, or film method 35,36... 

The literature mentions many procedures that can be followed to prepare micelles. One approach consists of the introduction of the copolymer in a nonselective solvent that represents the common solvent for both polymer blocks. The desired micellar structure is obtained by the selection of certain solution parameters such as temperature of a cosolvent or the subsequent addition of a selective solvent into a previously prepared solution from a common solvent after that, the common solvent is removed from the solution by dialysis. Another approach in the preparation of micelles involves the addition of the dry copolymer powder into a selective solvent. The preference for one method or another depends on the system investigated (Rodriguez-Hernandez et al. 2005). 

Film casting method— This involves the dissolution of the copolymer and drug in a volatile solvent then, the solvent is evaporated, leaving the polymer film that will be used in the bottom of a vial. Afterward, a warm buffer (or water) is added under agitation to dissolve the polymer film (Burt et al. 1999 Letchford and Burt 2007). If the copolymer is not soluble in water, the literature mentions dialysis or oil in water emulsion as micelles preparation procedures ... 

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