Pluronic surfactants solubilization

Lin and Yang (1987) also calculated the thermodynamic parameters of diazepam for micellar solubilization in Pluronic surfactant solutions at different temperatures (Table 13.4). For all systems, AG was negative, indicating micellar solubilization was spontaneous. The sign of entropy has been associated with the location of solubilized molecules within the micelles. Positive values have been observed for molecules embedded in the micelle center and negative values for adsorption of the molecules on the micelle surface. The results in this paper indicate that in the F-108 and F-88 Pluronics, diazepam molecules can penetrate into the micelle interior, whereas for F-68 and lower concentrations of F-88, diazepam is adsorbed on the micelle surface without penetration into the micellar core. 

Thermodynamic Parameters for the Solubilization of Diazepam by Pluronic Surfactants... 

Sek, L., et al., Examination of the impact of a range of pluronic surfactants nmvtfo solubilization behavior and oral bioavailability of lipidic formulations of atovaquodepharm. Pharmacql 58,... 

The importance of a consideration of both solubilizate and solubilizer structure in the selection of a particular surfactant for the solubilization of a given solute is illustrated by studies of the solubilization of para-substituted acetanilides by a series of structurally related poloxamer (polyoxyethylene-polypropylene) ABA block co-polymers (Pluronic surfactants) [83]. Fig. 5.19 shows the relation between the n value for the p-substituent group of the acetanilides and the slope K of plots of the amount of drug solubilized per... 

The solubility and release of naproxen from Pluronic PF-127 micelles were studied as a function of temperature and pH by Suh and Jun (1996). The solubility of the drug at pH 2 was signiLcantly increased as a linear function of PF-127 concentrations for three temperatures. Naproxen was highly entrapped by the micelles as indicated by large partition coefLcient. The micellar solubilization was a spontaneous (AG 0) and exothermic (AH< 0) process that resulted in a less ordered state (AS > 0). In the presence of PF-127, the release of naproxen was sustained at pH 2 and inversely proportional to the surfactant concentration. In contrast, at pH 7, PF-127 had little effect on the membrane transport of naproxen. The release of naproxen from the PF-127 gel into isopropanol myristate was also found to be dependent on the medium pH with the highest release observed at pH 6.3. 

These are stable micelles that are formed with polymeric surfactants. Amphiphilic block copolymers such as the pluronics (polyoxyethylene-polyoxypropylene block copolymers) are able to self-assemble into polymeric micelles and hydrophobic drugs may be solubilized within the core of the micelle or, alternatively, conjugated to the micelle-forming polymer. Although micelles are rather dynamic systems that continuously exchange units between the micelle structure and the free units in solution, those composed of polyoxyethylene - poly(aspartic acid) have been found sufficiently... 

Nonionic surfactants such as polyoxyethylated fatty alcohols (such as Emul-phor ON-870 from GAP), alkyl phenyl polyethylene glycol ethers (such as the Tergitols from Union Carbide) and polyoxyethylated octylphenol may be used as protective colloids along with anionic surfactants or, in some cases, as emulsifiers in their own right. The block copolymers of polyoxyethylene and polyoxypropylene (Pluronics) solubilized vinyl acetate. Polymerization takes place at the interface of the surfactant-monomer droplet and the aqueous phase [151]. 

Pluronic-coated carbon nanotubes The applicability of carbon nanotubes for neural tissue engineering was further proved by Bardi et al. (2009), wherein the carbon nanotubes when coated with Pluronic F127 (PF127), a PPO-PEO-PPO block copolymer, showed more distinctive biocompatibility properties than the individual components. The researchers proposed that PF127 stabilized and solubilized the CNTs due to its surfactant action, whereas CNTs circumvented the PF127-induced apoptosis by the so-called surfactant sequestration mechanism (Bardi et al., 2009). 

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