Reverse Pluronics

Reverse pluronics, 24 151 Reverse-roll coaters, 7 12—13 method summarized, 7 5t shear rates, 7 32t... 

Choi SH, Lee JH, Choi SM, Park TG. Thermally reversible pluronic/heparin nanocapsules exhibiting 1000-fold volume transition. Langmuir. 2(X)6 22 1758-62. 

The second type of EO/PO copolymers are prepared by reaction of poly(ethylene glycol) (difunctional) with PO or mixed EO/PO. These will have the structure (PO) (EO) ,(PO) and are referred to as reverse Pluronics. 

PEO-based copolymers have received much attention. In this respect, PEO-PPO and PEO-PPO-PEO Pluronic copolymers were investigated in organic solvents such as formamides, as illustrated by the works of Lindmann and coworkers and Alexandridis et al. [92-94], However, the formation of reverse micelles in organic solvents from PEO-based block copolymers has been shown to be a complex phenomenon due to the ability of PEO to crystallize. 

A further extension to the range is the Pluronic R surfactants in which the hydrophobic and hydrophilic blocks are reversed to give the structure below ... 

PEO-PPO-PEO triblock copolymers (Pluronics or Poloxamers) form reversible physically cross-linked hydrogels under certain concentration range and temperature. The use of this system in tissue engineering is scarce because of its inability to degrade. Di- or tri-block copolymers of PEG with PLA have been developed to overcome this problem. Multiple blocks of PEG and PLA, synthesized by condensation reaction of L-lactic acid in the presence of succinic acid. 

Evers R, Kool M, Smith AJ, van Deemter L, de Haas M, Borst P. Inhibitory effect of the reversal agents V-104, GF120918 and pluronic L61 on MDRl Pgp-, MRPl- and MRP2-mediated transport. Br J Cancer 2000 83 366-374. 

Since rapid collection of erstwhile single cells can be brought about by the use of dielectrophoresis, and the shape of the mass of cells so formed is controlled by the shape of the electrodes, by the frequency of the field, and by the shape of the cells, it appeared worthwhile to see if the shapes so formed could be made more permanent, so as to prepare desired structures of the cellular aggregates. To this end, the gel-forming properties of a relatively nontoxic block copolymer solution in water were used. A concentrated aqueous solution of the block copolymer of polyethylene oxide and polypropylene oxide (PEO-PPO) is quite fluid at 0°C to about 5°C, but sets reversibly to a rather stiff gel at about 30-40°C. The PEO-PPO polymer solutions are reported to be relatively nontoxic to most organisms (Pluronic resin F-127), Wyandotte Chemicals Corp.). 

As presented in Table 1, composite hydrogel based on PECE and Pluronic FI27 copolymers from SI to S5 showed temperature-dependent reversible sol-gel-sol phase transition. The composite hydrogels flowed freely at lower temperature, but became gelation at body temperature about 37°C (Figure 3). 

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