Temperature- and ionic strength-induced conformational changes in the lipid head group region of liposomes as suggested by zeta potential data

Makino, Kimiko; Yamada, Takeshi; Kimura, M.; Oka, Takashi; Ohshima, Hiroyuki; Kondo, Tamotsu

doi:10.1016/0301-4622(91)80017-l

Cited by 242 publications

(184 citation statements)

References 23 publications

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“…Although, in the present study, liposomes were prepared with phosphatidylcholine, which is a neutral lipid, they possessed a slight negative charge at higher cholesterol ratios and a slight positive charge at low cholesterol content (Table 1). This finding is consistent with the results obtained by Garcia-Manyes & Sanz (2005), who reported that phosphatidylcholine bilayer acquired negative zeta potential values in ultrapure water probably due to hydration layers formed around the surface (Egawa & Furusawa, 1999) and to the orientation of lipid headgroups (Makino et al, 1991). However, they observed a shift of zeta potential to positive values upon increasing the ionic strength of the medium, which was attributed to membrane interaction with mono-and divalent cations present in the medium.…”

Section: Zeta Potentialsupporting

confidence: 92%

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

2017

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Vaginal administration of sildenafil citrate has shown recently to develop efficiently the uterine lining with subsequent successful embryo implantation following in vitro fertilization. The aim of the present study was to develop sildenafil-loaded liposomes coated with bioadhesive polymers for enhanced vaginal retention and improved drug permeation. Three liposomal formulae were prepared by thin-film method using different phospholipid:cholesterol ratios. The optimal liposomal formulation was coated with bioadhesive polymers (chitosan and HPMC). A marked increase in liposomal size and zeta potential was observed for all coated liposomal formulations. HPMC-coated liposomes showed the greater bioadhesion and higher entrapment efficiency than chitosan-coated formulae. The in vitro release studies showed prolonged release of sildenafil from coated liposomes as compared to uncoated liposomes and sildenafil solution. Ex vivo permeation study revealed the enhanced permeation of coated relative to uncoated liposomes. Chitosan-coated formula demonstrated highest drug permeation and was thus selected for further investigations. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful coating of the liposomes by chitosan. Histopathological in vivo testing proved the efficacy of chitosan-coated liposomes to improve blood flow to the vaginal endometrium and to increase endometrial thickness. Chitosan-coated liposomes can be considered as potential novel drug delivery system intended for the vaginal administration of sildenafil, which would prolong system's retention at the vaginal site and enhance the permeation of sildenafil to uterine blood circulation.

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Section: Zeta Potentialsupporting

confidence: 92%

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

2017

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“…When looking at fpotential versus salt concentration of the dilution medium, a plateau was reached at a concentration of about 10 mM NaNO 3 and dilution with higher ionic strengths did not lead to a further increase in the f-potential. An explanation for this is found in Makino et al [24]. At low ionic strengths, the phosphatidyl groups are located at the outer end of the head group region.…”

Section: Influence Of Ionic Strength Of the Carrier Solutionmentioning

confidence: 87%

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

Hupfeld

Ausbacher

Brandl

2009

J of Separation Science

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Original Paper Asymmetric flow field-flow fractionation of liposomes: optimization of fractionation variablesThe purpose of this study was to investigate the influence of ionic strength of the carrier liquid, cross flow rate, focus flow rate, and sample load on the retention behavior of liposomes in asymmetric flow field-flow fractionation (AF4). Two differently prepared samples of large unilamellar vesicles (LUV) were used. Experiments were performed varying the factors systematically and evaluating their effect on both retention behavior of the liposomes and on particle size as obtained from online coupled multi-angle light scattering (MALS) analysis. The results showed that the focus flow rate had the least influence on the elution of liposomes. Elution of LUV is mainly governed by the chosen cross flow condition and ionic strength of the carrier liquid as well as its sample load. Optimal fractionation and size analysis were achieved using a sample load of about 10 lg, a cross flow gradient from 1.0 to 0.1 mL/min over 35 min and a carrier solution of NaNO 3 with a concentration of 10 mM. IntroductionLiposomes are vesicles consisting of an aqueous core surrounded by a phospholipid bilayer [1]. They have the ability to incorporate both amphiphilic and lipophilic compounds in their membrane-like bilayer as well as to encapsulate hydrophilic compounds [2]. Due to this ability liposomes have contributed to improving drug delivery of e.g., anthracyclines and play an important role in drug delivery research. It is widely accepted that liposomes as drug carriers may improve drug delivery in terms of therapeutic activity and safety [3 -5]. The size distribution of liposomes is important in terms of both the systemic circulation time upon injection into the blood stream and targeting abilities [3,6,7]. A study of the biodistribution of liposomes showed that the average size of the samples does not supply enough information and rather the size distribution should be used, especially for less homogeneous samples [7]. Asymmetric flow FFF (AF4) in combination with multi-angle light scattering (MALS) is the mostly applied sub-class of the FFF family and has gained increasing importance in the field of protein and peptide therapeutics as well as natural and synthetic polymers in recent years [8,9]. However, the number of publications about FFF of liposomes is rather limited compared to other applications and the technique has still not found widespread use despite it has various promising advantages over current particle size analysis methods such as photon correlation spectroscopy (PCS), and size exclusion chromatography [10,11]. For liposomal drug carriers a reliable size determination over the whole particle size spectrum from a few nanometers up to a micrometer could not be achieved with a single method so far. Such information on the other hand is essential for stringent control of the particle size which is governing the biodistribution and tumor targeting [7]. Despite a handful of successful attempts to characterize ...

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“…3,4) are probably caused by the fact that the packing of DOPC molecules in the layer is looser (0.67-0.69 nm 2 ) than in DPPC (0.46-0.49 nm 2 ) layer (Vaknin et al 1991), resulting from two unsaturated bonds present in DOPC hydrocarbon chains. The negative zeta potential of DPPC liposomes in low concentrated 1 mM NaCl may results from the exposed phosphate negatively charged groups outward (Makino et al 1991), while adsorption of Cl -ions rather does not takes place there (Ikonen et al 2010). Small zeta potential values in the phosphate buffer suggest that phosphate ions do not adsorb in large amounts to the liposome headgroups, what would compete with the diffuse layer compression caused by the high ionic strength.…”

Section: Particle Size Polydispersity and Zeta Potential Determinationmentioning

confidence: 99%

“…The sign and magnitude of zeta potential is determined by net charge accumulated on the liposome surface. The phospholipid DPPC and DOPC molecules are zwitterionic and according to Makino et al (1991) their polar heads can reorient depending on the ionic strength. It reflects in the zeta potential whose changes with the ionic strength can be interpreted via changes of the polar heads orientation, as well compression of the diffuse part of electric double layer.…”

Section: Particle Size Polydispersity and Zeta Potential Determinationmentioning

confidence: 99%

“…He also concluded that the origin of stagnancy is not caused by the interaction between the first water layer and the surface and the electrokinetic charge can maximally amount only a few lC cm -2 . Although the dipole potential cannot be directly measured experimentally but via some indirect experiments it can be evaluated (Clarke 2001;Wang 2012), on the other hand neither DPPC nor DOPC molecules possess net charge in a broad range of pH, and hence it was postulated that the surface potential may arise from oriented head groups (dipoles) (Makino et al 1991) of the lipid molecules, among others reasons, because even in 1.0 M KCl the zeta potential was measured where no diffuse ionic double layer should be present, and any changes in the bilayer structure have to change the dipole potential (Warshawiak et al 2011;Haldky and Haydon 1973;Gross et al 1994). Moreover, changes in the ionic strength (from 1lM to 1 M KCl) do not cause any significant changes in the dipole potential, which of course causes changes in the surface potential (Gross et al 1994).…”

Section: Profile Of Electric Potential Across the Liposome Bilayermentioning

confidence: 99%

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Zeta potential and surface charge of DPPC and DOPC liposomes in the presence of PLC enzyme

2016

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Zeta potential of liposomes is often measured in studies of their properties and/or applications. However, there are not many papers published in which zeta potential was determined during enzymatic reaction of a lipid. Therefore in this paper size, polydispersity index, and zeta potentials of 1,2-dipalmitoylsn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) liposomes were investigated in 1 mM NaCl (pH 6.2) and phosphate buffer (pH 8.1) during 60 min of phospholipase C action at 20 and 37°C. The hydrocarbon chains saturation differ these two phospholipids what appears in some differences in the zeta potential changes during the hydrolysis reaction run. The polydispersity index of the liposomes indicates that they are relatively stable and monodisperse, except for DPPC in phosphate buffer where up to 30 % of the initial amount forms larger size moieties, possibly aggregates of the liposomes, enzyme and the hydrolysis products. However, in this buffer zeta potential of the liposomes practically does not change during PLC action. Also the changes of zeta potential of DOPC liposomes are minor, although their negative values are much smaller than those of DPPC at both temperatures. These small changes of the potential may be due to compression of the diffuse double layer by present phosphate buffer. However, distinct changes of the zeta potentials in the presence of PLC take place in NaCl solution. The observed changes can be explained by reorientation of the phospholipid polar heads and their different density on DPPC and DOPC surface of the liposomes. Although it appeared that the zeta potential is not a very sensitive parameter for tracking the hydrolysis reaction in phosphate buffer, generally zeta potential enables the characterization of such reactions through determination of electrokinetic properties of liposomes as well as the polydispersity and size distribution of the liposomes do.

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Temperature- and ionic strength-induced conformational changes in the lipid head group region of liposomes as suggested by zeta potential data

Cited by 242 publications

References 23 publications

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

Asymmetric flow field‐flow fractionation of liposomes: optimization of fractionation variables

Zeta potential and surface charge of DPPC and DOPC liposomes in the presence of PLC enzyme

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