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The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution.

Pellach M, Margel S - Chem Cent J (2011)

Bottom Line: Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems.We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system.Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic) tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel. shlomo.margel@mail.biu.ac.il.

ABSTRACT
Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, however, is efficient for encapsulation only of hydrophobic compounds within hydrophobic template particles. In order to be encapsulated, the molecules must favor the hydrophobic phase of an organic/aqueous biphasic system, which is not easily achieved for molecules of amphiphilic character.The following work overcomes this difficulty by presenting a new method for encapsulation of amphiphilic molecules within uniform hydrophobic particles. We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system. Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic) tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

No MeSH data available.


Related in: MedlinePlus

A scheme explaining the low water solubility of fluorescein in presence of TEA and AcOH.
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Figure 4: A scheme explaining the low water solubility of fluorescein in presence of TEA and AcOH.

Mentions: After dissolving fluorescein in DCM containing either TEA or AcOH, on addition of an aqueous solution of the surfactant SDS, as expected, the fluorescein migrates to the aqueous phase, in ionic form. However, when fluorescein was dissolved in DCM, solvated using TEA, followed by addition of AcOH (a molar equivalent), on addition of an aqueous solution of SDS, the fluorescein remained in the organic phase (Figure 3). The ammonium acetate salt formed appears to have a "salting-out" effect, in which water molecules are attracted to the salt ions and are therefore less available for solvation of the compound in the aqueous phase. This effect in combination with H-bonds formed in the organic phase (e.g. as in Figure 4) together result in entrapment of fluorescein in the organic phase. With less than an equimolar amount of AcOH added compared to TEA, and therefore less salt formation and migration to the aqueous phase, the fluorescein is distributed throughout both the organic and aqueous phases (Figure 3f). With neutralisation of the basic solution, closure of the lactone ring is allowed, and the increase in ammonium acetate concentration forces the fluorescein back into the organic phase.


The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution.

Pellach M, Margel S - Chem Cent J (2011)

A scheme explaining the low water solubility of fluorescein in presence of TEA and AcOH.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3285059&req=5

Figure 4: A scheme explaining the low water solubility of fluorescein in presence of TEA and AcOH.
Mentions: After dissolving fluorescein in DCM containing either TEA or AcOH, on addition of an aqueous solution of the surfactant SDS, as expected, the fluorescein migrates to the aqueous phase, in ionic form. However, when fluorescein was dissolved in DCM, solvated using TEA, followed by addition of AcOH (a molar equivalent), on addition of an aqueous solution of SDS, the fluorescein remained in the organic phase (Figure 3). The ammonium acetate salt formed appears to have a "salting-out" effect, in which water molecules are attracted to the salt ions and are therefore less available for solvation of the compound in the aqueous phase. This effect in combination with H-bonds formed in the organic phase (e.g. as in Figure 4) together result in entrapment of fluorescein in the organic phase. With less than an equimolar amount of AcOH added compared to TEA, and therefore less salt formation and migration to the aqueous phase, the fluorescein is distributed throughout both the organic and aqueous phases (Figure 3f). With neutralisation of the basic solution, closure of the lactone ring is allowed, and the increase in ammonium acetate concentration forces the fluorescein back into the organic phase.

Bottom Line: Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems.We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system.Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic) tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel. shlomo.margel@mail.biu.ac.il.

ABSTRACT
Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, however, is efficient for encapsulation only of hydrophobic compounds within hydrophobic template particles. In order to be encapsulated, the molecules must favor the hydrophobic phase of an organic/aqueous biphasic system, which is not easily achieved for molecules of amphiphilic character.The following work overcomes this difficulty by presenting a new method for encapsulation of amphiphilic molecules within uniform hydrophobic particles. We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system. Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic) tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

No MeSH data available.


Related in: MedlinePlus