Poloxamers materials

The initiator usually constitutes less than 1% of the final product, and since starting the process with such a small amount of material in the reaction vessel may be difficult, it is often reacted with propylene oxide to produce a precursor compound, which may be stored until required [6]. The yield of poloxamer is essentially stoichiometric the lengths of the PO and EO blocks are determined by the amount of epoxide fed into the reactor at each stage. Upon completion of the reaction, the mixture is cooled and the alkaline catalyst neutralized. The neutral salt may then be removed or allowed to remain in the product, in which case it is present at a level of 0.5-1.0%. The catalyst may, alternatively, be removed by adsorption on acidic clays or with ion exchangers [7]. Exact maintenance of temperature, pressure, agitation speed, and other parameters are required if the products are to be reproducible, thus poloxamers from different suppliers may exhibit some difference in properties. 

Poloxamers and other polymeric materials such as albumin may coat the micro- or nano particle, alter their surface characteristics and reduce their phagocytosis and opsonization by the reticuloendothelial system following IV injection. Such surface modifications often result in prolongation in the circulation time of intravenously injected colloidal dispersions.Poloxamers also have been used to stabilize suspension such as NanoCrystal . ... 

Poloxamers are stable materials. Aqueous solutions are stable in the presence of acids, alkalis, and metal ions. However, aqueous solutions support mold growth. 

Poloxamers are used in a variety of oral, parenteral, and topical pharmaceutical formulations and are generally regarded as nontoxic and nonirritant materials. Poloxamers are not metabolized in the body. 

Note that in the USA the trade name Pluronic is used by BASE Corp. for pharmaceutical-grade and industrial-grade poloxamers, while in Europe the trade name Lutrol is used by BASE Corp. for the pharmaceutical-grade material. 

In this mode of synthesis of polymeric nanoparticles (e.g., of polybutylcycanoacrylates), monomeric materials (e.g., butylcyanoacrylate) are dispersed in a suitable solvent and emulsified. An initiator is generally added to the system and the monomers condense to form a polymeric matrix, although in the case of the alkyl cyanoacrylates no initiator is required as the aqueous medium acts as the initiator of polymerization. As one example (78) isobutylcyanoacrylate dissolved in ethanol can be mixed with an oil plus an oil-soluble drug to constitute one phase the second phase is an aqueous solution of 0.5% Pluronic F68 (poloxamer 118). The two phases are mixed and the polyisobutylcyanoa-crylate is formed at the interface between the oil and the water. The formation of alkylcyanoacrylate films at oil/water interfaces was investigated over 30 years ago (79). 

Figure 14.13 Oil-in-water emulsions may be stabilized by (A) non-ionic surfactants, [B) poloxamer block copolymers or [C) polymeric materials. The hydrophilic chains produce repulsion by mixing interaction [osmotic) or volume restriction [entropic).

Many drug carriers are made of hydrophobic materials such as lipids and poly(butyl cyanoacrylate). It will be thermodynamically unstable for submicron particles made of these materials to remain dispersed in an aqueous environment such as blood circulation. Surfactants or block co-polymers are therefore routinely included in these formulations to prevent particle aggregation. Studies showed that a number of these agents, most noticeably the nonionic surfactants such as polysorbates (also known as Tweens) and Tritons and block co-polymers such as poloxamers (also known as Pluronics), may inhibit the ABC transporters [97-99]. As previously discussed, ABC transporters interact with their substrates in the lipid bilayers of the plasma membrane. Surfactants can disrupt the arrangement of the lipid bilayer expressing the transporters and subsequently inhibit their drug efflux activities [97, 100]. It... 

Pluronic poloxamers can be suitable carrier materials for this purpose due to their capacity to enhance the absorption of water-insoluble compounds by formation of micelles in aqueous environment that can host such hydrophobic compounds. Different authors have described the formation of quercetin-loaded Pluronic micelles by thin-film hydration methods and have shown that the resulting micelles enhanced the solubilization of the active compound. Ghanem et al. described the encapsulation of quercetin in Pluronic F127 via spray drying. ... 

Another major factor affecting the particle uptake is the nature of the material used to prepare the particles. Uptake of nanoparticles prepared from hydrophobic polymers seems to be higher than that from particles with more hydrophilic surfaces. Microspheres composed of polystyrene, poly(methylmethacrylate), poly(hydroxybutyrate), poly(D,L-lactide), poly(L-lactide), and poly(o,L-lactide-co-glycolide) were absorbed into the Peyer s patches of the small intestine, whereas those composed of ethyl cellulose, cellulose acetate hydrogen phthalate, and cellulose triacetate were not absorbed. Residual poly(vinyl alcohol) in the surface of PLGA nanoparticles significantly reduced the intercellular uptake, in spite of the smaller particle size." Similarly, poloxamer coating of... 

Suh, J.M., Bae, S.J. and Jeong, B., 2005. ThetmogeUing multiblock poloxamer aqueous solutions with closed-loop sol-gel-sol transitions upon increasing pH. Advanced Materials, 17(1), 118-120. 

Various factors, which determine the poloxamer characteristics and behavior are the molecular weight, the ratio of poly(phenyl-ene oxide) to poly(ethylene oxide), temperature conditions, concentration, and the presence of ionic materials. There is thus a wide range of characteristics in existing commercially available poloxamers which can be exploited in formulating the compositions of the present disclosure, especially where the composition further includes a medicinal agent and is utilized for drug delivery purposes (29). 

Water-soluble coating materials dissolve promptly to reveal the uncoated suture underneath after wound closure. A typical example is poloxamer 188 found on Dexon Plus. There is, however, one technical concern about using water-soluble coating in actual wound closure. Suture materials are frequently soaked in saline after their removal from packages before use. Some or the bulk of water-soluble coating materials might be removed by this routine soaking practice. Thus, it is important... 

Although coating of suture materials facilitates easy passage through tissue, it frequently results in poor knot security. For example, Dexon Plus and coated Vicryl require four or hve square throws to form secure knots, while the uncoated Dexon and Vicryl sutures form secure knots with only two throws (1 = 1) (Rodeheaver et ah, 1981, 1983). Water-soluble coating materials like poloxamer 188, found on Dexon Plus, do not suffer from the adverse effects of water-insoluble coating materials on knot security. 

Abstract A review is presented of the main types of bioresorbable or bioabsorbable materials used in medical applications such as drug delivery. Groups discussed include aliphatic polyesters, polyanhydrides, poly(ortho esters) (POE), polyphosphazenes, poly(amino acids) and pseudo poly(amino acids), polyalkylcyanoacrylates, poly(propylene fumarate) (PPF), poloxamers, poly(p-dioxanone) (PPDO) and polyvinyl alcohol (PVA). 

Poloxamers are copolymers composed of two polyoxyethylene blocks separated by a polyoxypropylene block (Fig. 1.29). Polyoxyethylene content can vary from 10 to 90% in weight terms. Poloxamers are soluble in water and in polar solvents they can be solid, liquid, or paste depending on POE/ POP ratio and molecular weight. This material has been investigated for drug delivery applications. However, since poloxamers contain ether linkages, they are not readily metabolized and thus are not truly bioresorbable (Domb et al., 1997). 

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