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In situ precipitation: a novel approach for preparation of iron-oxide magnetoliposomes.

Xia S, Li P, Chen Q, Armah M, Ying X, Wu J, Lai J - Int J Nanomedicine (2014)

Bottom Line: Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading.The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response.In situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes.

View Article: PubMed Central - PubMed

Affiliation: Yiwu Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, People's Republic of China.

ABSTRACT

Background: Conventional methods of preparing magnetoliposomes are complicated and inefficient. A novel approach for magnetoliposomes preparation was investigated in the study reported here.

Methods: FeCl3/FeCl2 solutions were hydrated with lipid films to obtain liposome-encapsulated iron ions by ultrasonic dispersion. Non-encapsulated iron ions were removed by dialysis. NH3·H2O was added to the system to adjust the pH to a critical value. Four different systems were prepared. Each was incubated at a different temperature for a different length of time to facilitate the permeation of NH3·H2O into the inner phase of the liposomes and the in situ formation of magnetic iron-oxide cores in the liposomes. Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading.

Results: The magnetoliposomes prepared by in situ precipitation had an average particle size of 168±14 nm, zeta potential of -26.2±1.9 mV and polydispersity index of 0.23±0.06. The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response. Encapsulation efficiency ranged from 3% to 22%, while drug loading ranged from 0.2 to 1.58 mol Fe/mol lipid. The optimal conditions for in situ precipitation were found to be an alkalization pH of 12, temperature of 60°C, time of 60 minutes, and initial Fe concentration of 100 mM Fe(3+) + 50 mM Fe(2+).

Conclusion: In situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes.

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Possible mechanism of in situ precipitation within liposomes.
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f10-ijn-9-2607: Possible mechanism of in situ precipitation within liposomes.

Mentions: In this study, we developed a novel approach for the preparation of magnetoliposomes. Unlike other methods commonly used in other studies, the new method eliminated the demand for magnetofluid preparation, while the magnetic cores were formed in situ within the liposomes. The theoretical basis for this novel method is that different substances have different abilities to diffuse through the phospholipids bilayer, with small molecules, such as NH3, having a significantly greater permeability coefficient (10−2 cm/s) than ions, such as Fe3+/Fe2+ (10−13cm/s).8–10 Accordingly, FeCl3/FeCl2 solutions were first encapsulated into the inner aqueous phase of liposome, then NH3 · H2O was added into the external phase. The NH3 molecules rapidly diffused into the liposomes under the concentration gradient force, while only few Fe3+/Fe2+ ions leaked out from the liposomes because of their low permeability coefficient. With the accumulation of NH3 in the inner phase, the pH value increased gradually. Finally the Fe3+/Fe2+ were hydrolyzed and precipitated as iron oxides in an alkaline environment. The schematic diagram of the in situ precipitation is shown in Figure 10.


In situ precipitation: a novel approach for preparation of iron-oxide magnetoliposomes.

Xia S, Li P, Chen Q, Armah M, Ying X, Wu J, Lai J - Int J Nanomedicine (2014)

Possible mechanism of in situ precipitation within liposomes.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4043714&req=5

f10-ijn-9-2607: Possible mechanism of in situ precipitation within liposomes.
Mentions: In this study, we developed a novel approach for the preparation of magnetoliposomes. Unlike other methods commonly used in other studies, the new method eliminated the demand for magnetofluid preparation, while the magnetic cores were formed in situ within the liposomes. The theoretical basis for this novel method is that different substances have different abilities to diffuse through the phospholipids bilayer, with small molecules, such as NH3, having a significantly greater permeability coefficient (10−2 cm/s) than ions, such as Fe3+/Fe2+ (10−13cm/s).8–10 Accordingly, FeCl3/FeCl2 solutions were first encapsulated into the inner aqueous phase of liposome, then NH3 · H2O was added into the external phase. The NH3 molecules rapidly diffused into the liposomes under the concentration gradient force, while only few Fe3+/Fe2+ ions leaked out from the liposomes because of their low permeability coefficient. With the accumulation of NH3 in the inner phase, the pH value increased gradually. Finally the Fe3+/Fe2+ were hydrolyzed and precipitated as iron oxides in an alkaline environment. The schematic diagram of the in situ precipitation is shown in Figure 10.

Bottom Line: Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading.The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response.In situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes.

View Article: PubMed Central - PubMed

Affiliation: Yiwu Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, People's Republic of China.

ABSTRACT

Background: Conventional methods of preparing magnetoliposomes are complicated and inefficient. A novel approach for magnetoliposomes preparation was investigated in the study reported here.

Methods: FeCl3/FeCl2 solutions were hydrated with lipid films to obtain liposome-encapsulated iron ions by ultrasonic dispersion. Non-encapsulated iron ions were removed by dialysis. NH3·H2O was added to the system to adjust the pH to a critical value. Four different systems were prepared. Each was incubated at a different temperature for a different length of time to facilitate the permeation of NH3·H2O into the inner phase of the liposomes and the in situ formation of magnetic iron-oxide cores in the liposomes. Single-factor analysis and orthogonal-design experiments were applied to determinate the effects of alkalization pH, temperature, duration, and initial Fe concentration on encapsulation efficiency and drug loading.

Results: The magnetoliposomes prepared by in situ precipitation had an average particle size of 168±14 nm, zeta potential of -26.2±1.9 mV and polydispersity index of 0.23±0.06. The iron-oxide cores were confirmed as Fe3O4 by X-ray diffraction and demonstrated a superparamagnetic response. Encapsulation efficiency ranged from 3% to 22%, while drug loading ranged from 0.2 to 1.58 mol Fe/mol lipid. The optimal conditions for in situ precipitation were found to be an alkalization pH of 12, temperature of 60°C, time of 60 minutes, and initial Fe concentration of 100 mM Fe(3+) + 50 mM Fe(2+).

Conclusion: In situ precipitation could be a simple and efficient approach for the preparation of iron-oxide magnetoliposomes.

Show MeSH
Related in: MedlinePlus