Polyurea nanoparticles

Morral-Ruiz G, Melgar-Lesmes P, Luisa Garcia M, Solans C, Jose Garcia-Celma M. Polyurethane and polyurea nanoparticles based on polyoxyethylene castor oil derivative surfactant suitable for endovascular applications. Int J Pharm January 30, 2014 461(1-2) 1-13. 

Table 7.1 Synthesis aspects of polyurethane and polyurea nanoparticles obtained from OAV nano-emulsions... 

Morral-Ruiz G, Solans C, Garcfa ML, Garcfa-Cehna MJ. Formation of pegylated polyurethane and lysine-coated polyurea nanoparticles obtained from OAV nano-emulsions. Langmuir 2012 28(15) 6256-64. 

Morral-Rufz G, Melgar-Lesmes P, Garcfa ML, Solans C, Garcfa-Cehna MJ. Design of biocompatible surface-modified polyurethane and polyurea nanoparticles. Polymer 2012 53(26) 6072-80. 

Ley S V, Mitchell C, Pears D, Ramarao C, Yu JQ, Zhou WZ. Recyclable polyurea-microencap-sulated Pd(0) nanoparticles an efficient catalyst for hydrogenolysis of epoxides. Org Lett 2003 5 4665-4668. 

An approach to immobilization which has recently become popular is microencapsulation in polymers, such as polystyrene and polyurea, developed by the groups of Kobayashi [34] and Ley [35], respectively. For example, microencapsulation of palladium salts or palladium nanoparticles in polyurea microcapsules... 

Fig. 20 TEM micrographs of polyurea capsules loaded with different amounts of silver nanoparticles (a) 30 mg AgN03, (b,c) 120 mg AgN03 in the aqueous phase [188]...

Hydrophilic materials can be encapsulated with the inverse minianulsions by using interfacial polymerization such as polyaddition and polycondensation, radical, or anionic polymerization. Crespy et al. reported that silver nitrate was encapsulated and subsequently reduced to give silver nanoparticles inside the nanocapsules. The miniemulsions were prepared by anulsilying a solution of amines or alcohols in a polar solvent with cyclohexane as the nonpolar continuous phase. The addition of suitable hydrophobic diisocyanate or diisothiocyanate monomers to the continuous phase allows the polycondensation or the cross-linking reactions to occur at the interface of the droplets. By using different monomers, polyurea, polythiourea, or polyurethane nanocapsules can be formed. The waU thickness of the capsules can be directly tuned by the quantity of the reactants. The nature of the monomers and the continuous phase are the critical factors for the formation of the hollow capsules, which is explained by the interfacial properties of the systan. The resulting polymer nanocapsules could be subsequently dispersed in water. 

T. Hirai, T. Watanabe and I. Komasawa, Preparation of semiconductor nanoparticle-polyurea... 

The formation of polyurethane nanoparticles from inverse nano-emulsions (W/O) has also been achieved. Interfacial polyaddition in inverse nano-emulsion is of special interest since this allows the encapsulation of hydrophilic active materials such as proteins or nucleic acids. Thus, taking advantage of the high reactivity of tolylene 2,4-diisocyanate with water molecules, polyurea lipid nanocapsules with aqueous cores obtained from W/O nano-emulsions and prepared by PIT method were designed. Polymer synthesis occurs by in situ interfacial polymerization after nano-emulsion formation. Volatile oils employed as the continuous phase were removed by evaporation and the nanocapsules were redispersed in water. These nanocapsules could be potentially used for encapsulation of both hydrophilic and lipophilic molecules simultaneously. 

Figure 7.1 Fonnation of different polyurethane nanoparticles (naked polyurethane, pegylated pol5mrethane, lysine-coated polyurea, biotinylated polyurethane-urea/pc DNA complex, and functionalized streptavidin-coated polyurethane-urea nanoparticles) obtained by interfacial polycondensation from O/W nano-emulsions (a) and transmission electron micrographs of polyurethane nanoparticles after being negatively stained with 1% v/v uranyl acetate (b).

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