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

Abstract

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.

Development of antiproliferative long-circulating liposomes co-encapsulating doxorubicin and curcumin, through the use of a quality-by-design approach

“…The negative surface charge which the liposomes exhibited is due to the type of structural phospholipids and, according to the literature, is consistent with the liposomes prepared with phosphatidylcholine 43. These findings are in agreement with those reported by others 55,57. DPPC is a zwitterionic-type phospholipid which can change the orientation of its polar groups depending on the ionic strength of the medium.…”

“…DPPC is a zwitterionic-type phospholipid which can change the orientation of its polar groups depending on the ionic strength of the medium. In low-ionic strength conditions, the net surface charge of the particles is negative, while the opposite can be observed with high ionic strength 55. Other research groups reported that by adding a PEGylated lipid, the zeta potential would shift toward more negative values 52.…”

“…The temperature was adequately selected for this study to be over the transition temperature of DPPC (41°C) 55. During melting, the phospholipids undergo transformation from a gel to a fluid phase.…”

Essential oil-loaded lipid nanoparticles for wound healing

“…These results should conceivably be due to the presence onto nanoparticle surface of lecithin, which was proved to confer a negative zeta potential to nanosystems. 27 The presence of lecithin allowed particle stabilization and controlled particle aggregation as evidenced by 3-month stability results ( Figure 1A and B). Eucalyptus EO loaded in NLC o/e was close to 100% (101.74±9.06%, mean value ± SD, n=3), indicating that the preparation procedure did not impair oil stability and loading, although it is a volatile extract.…”

Stratum corneum lipid liposome-encapsulated panomycocin: preparation, characterization, and the determination of antimycotic efficacy against <em>Candida</em> spp. isolated from patients with vulvovaginitis in an in vitro human vaginal epithelium tissue model

“…21,[40][41][42] Also, an absolute value of zeta potential .20 mV for the liposomes shows their stability. 43 Thus, we have concluded that empty and panomycocinloaded SCLLs with zeta potential values of +22.0 mV and +21.4 mV, respectively, were stable in the colloidal system. An essential criterion for the active ingredient to be released at the target site in high amounts and in an active form is the lack of covalent bonds with its encapsulating vesicle.…”