Development of liposomes containing ethanol for skin delivery of temoporfin: Characterization and in vitro penetration studies

The aim of this study was to develop ethanol-containing (3.3–20%, w/v) liposomes loaded with temoporfin (mTHPC), which presents a highly hydrophobic photosensitizer with low percutaneous penetration, and to investigate their skin penetration enhancing effect. Characterization parameters of liposomes were measured by photon correlation spectroscopy, lamellarity was analyzed by cryo-electron microscopy and mTHPC-content in formulations was determined spectrofotometrically. In order to assess the stability of mTHPC–liposomes at 4 and 23 °C, at predetermined time intervals characterization parameters and mTHPC-content were measured. The in vitro skin penetration of mTHPC was investigated using human abdominal skin mounted in Franz cells. The results indicated that mTHPC–liposomes were of a small particle size, small polydispersity index, negative surface charge, unilamellar or oligolamellar, and of a spherical or oval shape. All liposomes were stable during 12 months’ storage at 4 °C. Increasing the amount of ethanol in mTHPC–liposomes the skin deposition of mTHPC increased also. Liposomes without ethanol delivered the lowest amount of mTHPC into the skin, while liposomes containing 20% ethanol showed the highest penetration enhancement. In conclusion, mTHPC–liposomes containing 20% ethanol could be a promising tool for delivering temoporfin to the skin, which would be beneficial for the photodynamic therapy of cutaneous malignant or non-malignant diseases.     

番茄红素脂质体的制备工艺

采用逆相蒸发法和薄膜法两种方法制备番茄红素脂质体.筛选出制备高包封率脂质体的工艺为:卵磷脂与胆固醇之比为3:1,温度为35℃,番茄红素与磷脂比例为1:6,旋转速度为200r/min,此条件下番茄红素脂质体的最高包封率可达71.26%.     

Tripolyphosphate-sensitive egg phosphatidylcholine liposomes incorporating hydrophobically modified poly(ethylene imine)

Liposomes, which release their contents in answer to tripolyphosphate (TPP, a penta-anion), were prepared by immobilizing hydrophobically modified poly(ethylene imine) (HmPEI) on the surface of egg phosphatidylcholine (egg PC) liposome. HmPEI was prepared by covalently attaching decanoyl chloride to PEI through a condensation reaction. According to the ¹H NMR spectrum, the number of decanoyl chloride per one molecule of PEI was about 21, and HmPEI was air/water interface-active. HmPEI could readily complex with TPP in HEPES buffer (30 mM, pH 7.0), confirmed by Fourier transformed infrared spectrophotometer spectroscopy. The complexation increased with increasing the concentration of HmPEI and TPP, investigated through the measurement of optical density and light scattering intensity. Liposomes incorporating HmPEI were prepared by a film hydration and sonication method. The liposomes were multi-lamellar vesicles, observed on transmission electron microscope. Liposomes free of HmPEI did not release calcien when they were mixed with TPP. Liposomes whose egg PC/HmPEI was relatively low (e.g., 20:1 and 20:2) released calcein but not extensively (less than 10%) when mixed with TPP. Liposomes whose egg PC/HmPEI was relatively high (e.g., 20:4 and 20:20) released calcein extensively. For example, when the liposomes with lager amount of HmPEI were mixed with TPP so that HmPEI/TPP weight ratio was 8:1, the release degree in 60 sec was more than 70%. HmPEI can complex with TPP through electrostatic interaction and the complexation was thought to cause perturbation in the liposomal membranes and trigger the release.     

脂质体封端CsPbX3(X=Cl,Br,I)纳米晶体的制备及在发光二极管中的应用

以脂质体充当表面封端配体修饰合成后的CsPbX₃纳米晶体.封端CsPbX₃纳米晶能保持原始形状和粒径大小,相对量子产率提升至（100±3）%,发射光谱在411~626 nm范围内可调.将其存储于空气（温度25℃,相对湿度50%）中150 d仍保持立方晶型.以DOPC-CsPbBr₃为颜色转换器可制造显色指数高达91.2的白色发光二极管,应用前景广阔.     

Near-infrared induced membrane surface electrostatic potential, fluorescent measurements

The change of the electrostatic surface potential induced by near-infrared radiation was monitored by the fluorescence probe technique. Fluorescence intensity of 1-anilinonaphtalene-8-sulfate (ANS) was studied in the pH range 4.8–9.5 before and after exposition to NIR (700–2000 nm). The intensity of fluorescence changed (decreased after exposition on radiation) only at pH 7.4. The effect is due to decreasing concentration of ANS in liposome membrane after irradiation. The modified distribution of ANS in liposome membrane upon irradiation is attributed to the dehydration of membrane surface. Dehydratation diminishes the electrostatic surface potential about 36±15 mV.     

Lipophilic peptide nucleic acids containing a 1,3-diyne function: synthesis, characterization and production of derived polydiacetylene liposomes

Adenine-, cytosine- and thymine-containing peptide nucleic acid (PNA) monomers have been synthesized in which either diacetylenic or stearoyl moieties are attached to the N-or C-terminus; the diacetylenic group is embedded within a long hydrocarbon chain. A range of analogous lipophilic functionalized PNA oligomers have been prepared using either solid phase synthesis or a post-synthetic solution phase procedure following cleavage of the PNA oligomer from the solid support. Selected functionalized PNA monomers and oligomers have been incorporated into liposomal polydiacetylenes and characterized by UV-vis absorption spectroscopy. Preliminary investigations show that blue PDA-liposomes containing thymine-based PNAs can be formed and that production of liposomes with other PNA systems are viable.     

Interaction Between Liposomes and Neutral Polymers: Effect of Adsorption on Drug Release

The processes of adsorption of two neutral polymers (poly(vinyl pyrrolidone), PVP and poly(vinyl alcohol), PVA) were investigated on liposomes composed of soy lecithin/dicetyl phosphate/cholesterol = 25:2:3 (molar ratio). The liposomes were prepared in buffered solution at pH = 7.4 and mixed with the solution of the measured polymers in the desired polymer/lipid (w/w) ratios. Adsorption was measured by determination of the equilibrium bulk concentration of the polymer. In the case of PVA quantitative adsorption measurements with a specific reagent were possible. Adsorption isotherms were recorded at 25 ± 1°C. It was concluded that adsorbed and unadsorbed PVA molecules are in equilibrium even at low polymer/ lipid ratios. The results were confirmed by dynamic laser light scattering (DLS), and thermal activity monitoring (TAM) experiments. Another group of the liposomes was prepared in 60 mM ammonium sulphate (pH = 5.0) and we filled the vesicles with a test dye, acridine orange (AO) using the pH-gradient (remote loading) method. The AO release property of liposomes was tested with a special vertical diffusion cell after we had made PVA adsorb on their surface in different PVA/lipid (w/w) ratios.     

Sterically Stabilized Vesicles

After significant developments in liquid crystal and polymer research, scientists became interested in lyotropic systems containing polymers. These studies investigated, for instance, phase behavior and stability characteristics of suspensions of colloidal particles containing water-soluble or surface-adsorbed polymers or block copolymers. The most frequently studied were micelles, latex prticles, and lipid vesicles (liposomes). Liposomes aggregate and fuse in the presence of hydrophilic polymers but their properties were difficult to explain when block copolymers were adsorbed or surfactants with larger polymeric polar heads were inserted into the liposome membrane, because such systems are inherently ill defined. Liposomes containing diacyl surfactants with covalently linked, longer polymer chains display many new properties with very important consequences for both basic and applied research. They stimulate fundamental studies on phase behavior and polymer conformation, scaling laws, colloidal and surface properties, and cell function: applications deal predominantly with liposomes as drug delivery systems. While in basic research theory is currently more advanced than experiment, in medical applications theoretical understanding lags behind experimental achievements. It was discovered only relatively late that liposomes with an appropriate polymer coating are significantly more stable in a biological milieu, a necessary condition for their utility as drug carriers. In particular in medical applications, this practice has rejuvenated the field of anticancer therapy and targeted drug deliviery. All these advances were made possible by an effective and synergistic overlap of many different disciplines.     

Homogeneous immunoassay of atrazine in water by terbium-entrapping liposomes as fluorescent markers

Atrazine (Atr) was conjugated to mastoparan (Mast) cytolytic peptide; Mast-Atr derivative was used as cytolytic agent on liposomes trapping Tb/citrate complex. This was applied in a time-resolved fluoroimmunoassay for detection of Atr in water. The cytolytic activity was read by means of time-resolved fluorescence after adding an excess of dipicolinic acid (DPA). Tb/citrate-entrapping liposomes are easy to prepare, and the assay is carried out in a short incubation time and in a range between 10 pg and 100 ng. The procedure was applied to analyse samples taken from Adda River and from irrigation ditches in an agricultural area around the town of Lodi. Recovery in samples spiked with two different Atr concentrations was between 95 and 105%.     

Potentiometric determination of octanol-water and liposome-water partition coefficients (log P) of ionizable organic compounds

The logarithm of the octanol-water partition coefficient, log P, is a key physicochemical property for both pharmaceutical drugs and agrochemicals. It is also required by legislation as part of the physicochemical properties profile for high volume production chemicals. This Letter describes a simple method for determining log P values (over a wide range from −0.8 to 5.3) for 12 organic weak acids and bases using potentiometric titrations, with octanol or phosphatidyl choline liposomes as the partitioning medium. Such titrations take comparatively little time (about 30-45 min per titration), are easy to implement, and can be carried out with an inexpensive laboratory titrator.