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Different liposomal formulations containing the tetraether lipid GDNT are characterized regarding their stability. The initial diameter ranged from 69 nm for the mixture 9:1 GDNT: Phospholipon to 137.5 nm for the pure GDNT. The negative zeta potential is representative for all liposomal formulations. (a) The size stability of the liposomes is tested at different temperatures. The measurements are done after incubating 40 µl liposome solutions in 240 µl bidestilled water for 4 h. The results show the stabilizing effect of GDNT content in the liposome structure. (b) The diagram represents the stability of particles after autoclavation. The samples are incubated 15 min at 121°C and 29 psi for sterilization. (c) Both of the samples are investigated after incubating 4 days in different pH solutions. Standard deviations are calculated from three independent measurements
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Liposomes are widely investigated for their applicability as drug delivery systems. However, the unstable liposomal constitution is one of the greatest limitations, because the liposomes undergo fast elimination after application to the human body. In the presented study, novel archeal lipids were used to prepare liposomal formulations which were t...
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... In Fig. 2, the initial diameter and zeta potential values of liposome formulations are ...
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... The size measurements in Fig. 2. It could be shown that the liposomal formulations containing GDNT can be autoclaved. The diameter is relatively ...
Citations
... Benvegnu et al. have also shown that adding synthetic TEL to conventional liposomes increases their stability [18]. Ozecetin et al. prepared liposomes containing TEL from thermophilic or hyperthermophilic archaea to overcome the drawbacks of conventional liposomes, i.e., Thermoplasma acidophilum or Sulfolobus acidocaldarius, and the impact on stability was investigated [21]. ...
... Therefore, the stability of TEL liposomes was investigated under autoclavation conditions, according to Bode et al. [43]. Previously, we reported the autoclavation data for Glycerol Dialkyl Nonitol Tetraether (GDNT) liposomes [21]. Due to the high stability of TEL, we investigated the total polar lipids, and different TEL formulations were compared after autoclavation. ...
Conventional liposomes often lack stability, limiting their applicability and usage apart from intravenous routes. Nevertheless, their advantages in drug encapsulation and physicochemi-cal properties might be helpful in oral and pulmonary drug delivery. This study investigated the feasibility and stability of liposomes containing tetraether lipids (TEL) from Thermoplasma acidophi-lum. Liposomes composed of different molar ratios of TEL:Phospholipon 100H (Ph) were produced and exposed to various temperature and pH conditions. The effects on size, polydispersity index, and zeta potential were examined by dynamic and electrophoretic light scattering. Autoclaving, which was considered an additional process step after fabrication, could minimize contamination and prolong shelf life, and the stability after autoclaving was tested. Moreover, 5(6)-carboxyfluores-cein leakage was measured after incubation in the presence of fetal calf serum (FCS) and lung sur-factant (Alveofact). The incorporation of TEL into the liposomes significantly impacted the stability against low pH, higher temperatures, and even sterilization by autoclaving. The stability of lipo-somes containing TEL was confirmed by atomic force microscopy as images revealed similar sizes and morphology before and after incubation with FCS. It could be concluded that increasing the molar ratio in the TEL:Ph liposome formulations improved the structural stability against high temperature , low pH, sterilization via autoclaving, and the presence of FCS and lung surfactant.
... TEL are the main part of cell membrane of archaeon Thermoplasma acidiophilum, this kind of archaea grow at pH 2 and 56 °C and since they have no cell wall, it is the lipid composition of their membrane that provides high chemical and thermal stability (U. Dayyoub et al., 2008;Frant et al., 2006;Ozcetin et al., 2011Ozcetin et al., , 2010Vidawati et al., 2010). The hydrocarbon chains of these lipids have no double bonds and are bond to the glycerol residues via ether bonds instead of ester bonds. ...
Bacterial biofilm and crystalline deposits are the common causes of failure of long-term indwelling urinary catheter. Bacteria colonise the catheter surface causing serious infections in the urinary tract and encrustations that can block the catheter and induce trauma in patients. In this study, the strategy used to resist bacterial adhesion and encrustation represents a combination of the antibacterial effects of norfloxacin and silver nanoparticles and the PLGA-based neutralisation of alkali products of urea hydrolysis gained through the degradation of the polymer in an aqueous milieu. Silver nanoparticles were coated with tetraether lipids (TEL) to avoid aggregation when dispersed in acetone and during the film formation. The polymer films loaded with the two antibacterial agents were applied on Polyurethane (PUR) and Silicon sheets. We demonstrated the antibacterial and anti-adhesion effectiveness of the coatings whereby commercially available biocompatible polymers PUR and Silicon were used as controls. Using artificial urine and an in vitro encrustation model, it was shown that the coatings resist the encrustation for at least 2 weeks. This combination of a biodegradable polymer and wide-range antibacterial agents represents a potentially attractive biocompatible coating for urinary catheters.
... liposomes TEL was extracted from biomass of Thermoplasma acidophilum in the presence of chloroform:methanol (2:1 v/v) [12][13][14]. TEL was mixed with DPPC in the concentration of 1 mg/ml (70:30 molar ratio) and dried under vacuum at 50 °C in round bottomed flask in order to obtain a thin lipid film. The film was hydrated with PBS buffer pH 7.4 containing 0.1 M NaCl. ...
For the development of site specific liposomes, high stability and long circulation properties are very promising for the improvement of drug targeting and drug delivery system as well as improvement of bioavailability of efficient bioactive drugs. Tetraether lipids (TELs) are very stabile lipids, extracted from Thermoplasma acidophilum. Because of its high chemical stability and its biocompatibility, Tetraether lipid liposomes prepared with TELs are excellent candidates for liposomal drug delivery. In this study a model protein, Concanavalin A (ConA) was chosen for a simulation of a specific adsorbtion onto mannan surface. Concanavalin A (ConA) is a lectin, extracted from Canavalia ensiformis, which interacts with sugar domains localized on inflammatory active tissues or tumors. In this study, stable TEL liposomes were prepared and characterized. Furthermore to develop side specific liposomes, tetraether lipids were activated and, ConA was covalently bond onto the surface of the prepared liposomes. Interaction of ConA conjugated liposomes with mannan-modified surfaces was investigated by Biomolecular Interaction Analysis (BIA) via Reflectometric Interference Spectroscopy (RIfS). This provides real time observation of interactions between carbohydrate structure and TEL liposomes. Specific interaction was also visualised by AFM imaging subsequent to the RIfS measurements. According to the results, with ConA conjugated liposomes, high specific adsorption efficiency was observed. Consequently, this specific adsorption assay between ConA and mannan surface can be considered as a model for the further studies utilized with specific biomarkers for a selective active agent transfer to tumors and inflammatory active tissues. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
... Atomic force microscopy was performed on a NanoWizard (JPK instruments, Berlin, Germany) as described in detail elsewhere [23]. The microscope was vibration-damped. ...
The monomolecular organisation of the natural asymmetric and symmetric bolaamphiphilic (archaebacterial tetraether lipids) was studied using a combination of Langmuir film balance, ellipsometry, and atomic force microscopy (AFM). Monolayer films were transferred onto silicon wafer substrates. After transfer of the lipids onto several kinds of silicon wafer substrates (hydrophobic, hydrophilic, and amino-silanised), the monolayer films were further investigated by ellipsometry and AFM in order to determined whether bolaamphiphiles are oriented differently at the water-air interface, including "horseshoe" and "upright" configurations. The thickness of the monolayer film, which was determined by ellipsometry, represents a combined mean value of the domains. The surface morphology, which was evaluated by AFM showed that in all films, the domains were arranged in small domains or the most homogeneous organisation, depending on the properties of the wafer silicon substrates. From all films, the hydrophobically transferred lipids showed the most homogeneous organisation on the substrates. After transfer onto hydrophilic and amino-silanised surfaces, the lipids were arranged in small islands on the substrates.
Due to their special chemical structure, tetraether lipids (TEL) represent essential elements of archaeal membranes, providing these organisms with extraordinary properties. Here we describe the characterization of a newly isolated structural element of the main lipids. The TEL fragment GDNT‐β‐Glu was isolated from Sulfolobus metallicus and characterized in terms of its chemical structure by NMR‐ and MS‐investigations. The obtained data are dissimilar to analogically derived established structures – in essence, the binding relationships in the polar head group are re‐determined and verified. With this work, we provide an important contribution to the structure elucidation of intact TEL also contained in other Sulfolobus strains such as Solfulobus acidocaldarius and Sulfolobus solfataricus. The isolation and structure elucidation of a tetraether lipid (TEL) fragment GDNT‐β‐Glu occurring in Sulfolobus strains are described. The investigations reveal new knowledge regarding the binding relationships which is also important for the general structure determination of intact TEL.
The initial burst release of water-soluble photosensitizers is one of the major problems encountered the development of controlled release formulations. In this study, the freely water soluble chlorin e6 (Ce6) was assembled with cationic lipid 1, 2-dioleoyl-3-trimethylammonium-propane (DOTAP) at DOTAP: Ce6 to improve its loading efficiency in the liposomal bilayer. Tetraether lipids (TELs) derived from Sulfolobus acidocaldarius were added to DOTAP: Ce6 assembly in a concentration range of 2.5 x 10(-4)-1.6 x 10(-3) M to stabilize the membrane rigidity of the liposomes and to provide controlled release system. From the comparative spectroscopic experiments, it has been shown that the assembled DOTAP: Ce6 along with addition of TELs have improved the loading efficiency of Ce6 in TELs-liposomes and obviously modified the release profile of Ce6. The in vitro cell viability of Ce6 in mouse neuro-blastoma (Neuro-2a) and ovarian cell carcinoma (SK-OV-3) confirmed neglected dark cytotoxicity and presented potential photo-induced cytotoxicity with the effect was being more pronounced in Neuro 2a than in SK-OV-3. In-situ IV-injection of chick chorioallantoic membrane (CAM) showed hemorrhage and necrosis 30 min post irradiation at 1.8 mole % TELs (19.9 J/cm(2)). Higher TELs of 2.2 and 3.7 mole % in particular demonstrated localized vascular destruction within the irradiated area. Our results suggest that TELs favored slower release rates of Ce6. This, in turn, tetraether lipids can be considered as a versatile class of lipids for photodynamic modality for destruction of cancer cells and tumor vasculature while sparing the quiescent ones.
Copyright © 2015 Elsevier B.V. All rights reserved.
The monomolecular organisation of symmetric, chemically modified tetraether lipids caldarchaeol-PO(4) was studied using Langmuir film balance, ellipsometry, and atomic force microscopy (AFM). Solid silicon wafer substrates were modified to hydrophobic, hydrophilic, and amino-silanised surfaces; and Langmuir-Blodgett (LB)-films were transferred onto each. LB-caldarchaeol-PO(4) films were subjected to further rinsing with organic solvent and additional physical treatments, to compare their resistance and stability on chemisorbed (amino-silanised) and physisorbed (hydrophobic and hydrophilic) surfaces. The resistance and stability of these monolayer films was characterized by ellipsometry and AFM, and film thickness was determined using ellipsometry. AFM was also employed to observe surface morphology. Monolayer films on hydrophobic surfaces were found to be more resistant to rinsing with organic solvent and additional physical treatments than monolayer films on either amino-silanised or hydrophilic surfaces. The hydrophobic effect with hydrophobic surfaces appears to support the formation of stronger caldarchaeol-PO(4) films on silicon wafer substrates, with increased resistance and stability.
