Poloxamers

Because the lengths of the polymer blocks can be customized, many different poloxamers exist that have slightly different properties. For the generic term "poloxamer", these copolymers are commonly named with the letter "P" (for poloxamer) followed by three digits, the first two digits x 100 give the approximate molecular mass of the polyoxypropylene core, and the last digit x 10 gives the percentage polyoxyethylene content (e.g., [|P407] Poloxamer with a polyoxypropylene molecular mass of 4,000 g/mol and a 70% polyoxyethylene content). For the Pluronic tradename, coding of these copolymers starts with a letter to define its physical form at room temperature. liquid, P = paste, F = flake (solid)) followed by two or three digits, The first digit (two digits in a three-digit number) in the numerical designation, multiplied by 300, indicates the approximate molecular weight of the hydrophobe; and the last digit x 10 gives the percentage polyoxyethylene content (e.g., L61 = Pluronic with a polyoxypropylene molecular mass of 1,800 g/mol and a 10% [|polyoxyethylene] content). In the example given, poloxamer 181 (P181) = Pluronic L61.
 * Poloxamers** are nonionic composed of a central [|hydrophobic] chain of [|polyoxypropylene] (poly(propylene oxide)) flanked by two [|hydrophilic] chains of [|polyoxyethylene] (poly(ethylene oxide)). The word "poloxamer" was coined by the inventor, Irving Schmolka, who received the patent for these materials in 1973. [|[1]] Poloxamers are also known by the trade name **Pluronics**. [|[2]]

**Uses** Among other things, they can be used to increase the water solubility of hydrophobic, oily substances.For this reason, these polymers are commonly used in industrial applications, cosmetics, and pharmaceuticals. They have also been evaluated for various drug delivery applications and were shown to sensitize drug resistant cancers to chemotherapy. Poloxamers are substances of high molecular weight made up of repeating monomer units. These are widely used in pharmaceutical systems as adjuvants, suspending and emulsifying agents, adhesives, packaging and coating materials and increasingly, components of controlled and site specific drug delivery systems. The chemical reactivity of polymers depends upon the chemistry of their monomer units, but their properties depend to large extent on the way the monomers are put together.

In bioprocess applications, pluronic is also used in cell culture media for its cell cushioning effects because its addition leads to less stressful shear conditions for cells in reactors.



Biological Effects
Work led by Kabanov has recently shown that some of these polymers, originally thought to be inert carrier molecules, have a very real effect on biological systems independently of the drug they are transporting. The poloxamers have been shown to incorporate into cellular membranes affecting the microviscosity of the membranes.

The poloxamers have also been shown to enhance proto-apoptotic signaling, decrease anti-apoptoic defense in MDR cells, inhibit the glutathione/glutathione S-transferase detoxification system, induce the release of cytochrome C, increase reactive oxygen species in the cytoplasm, and abolish drug sequestering within cytoplasmic vesicles.