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Lipid-Based Nanoparticles: SLN, NLC, and MAD
Published in Madhu Gupta, Durgesh Nandini Chauhan, Vikas Sharma, Nagendra Singh Chauhan, Novel Drug Delivery Systems for Phytoconstituents, 2020
Rita Cortesi, Paolo Mariani, Markus Drechsler, Elisabetta Esposito
The hexagonal phase H is characterized by cylindrical micelles as the structure elements, packed in a 2-D hexagonal lattice. Notably, two types of hexagonal phase are possible, namely the type I (direct) phase and the type II (inverse) phase. In the first case, the water is outside and the hydrophilic groups lie on the cylinder surface while the hydrophobic chains are inside the cylinders; in the second case, the water is contained in each cylinder that is wrapped by the hydrophilic lipid groups; on the other hand the region between the cylinders is filled by the hydrophobic chains.
Liquid Crystals as Drug Delivery Systems for Skin Applications
Published in Andreia Ascenso, Sandra Simões, Helena Ribeiro, Carrier-Mediated Dermal Delivery, 2017
Dispersed systems can also be prepared when the bulk liquid crystalline structure is dispersed in an excess of water and forms nanoparticles. In this way, cubic phase gels can be fragmented and, with the addition of stabilizers, form stable colloidal dispersions, which are termed cubosomes. In the same way, hexagonal phases can also be dispersed and form structures named hexosomes [2,10]. These nanostructured particles consist of a unique drug delivery system with interesting properties, such as an increased surface area generated by their inherent nanostructure. An important feature of these particles is that they retain the inner structures of liquid crystalline systems, which confers sustained release properties [9,12,21–23].
Polymorphic Phase Behaviour of Membrane Lipids
Published in Sek Wen Hui, Freeze-Fracture Studies of Membranes, 1989
The common nonbilayer phases formed by lipids in aqueous dispersions are (1) micelles, (2) inverted micelles, (3) inverted hexagonal or hexagonal II (Hex II), and (4) cubic.11 Micelles are generally too small to be seen by freeze-fracture electron microscopic techniques. Inverted micelles are larger due to the water pocket enclosed by the lipid and can be seen by electron microscopy (see Section III). The inverted hexagonal phase is the most common nonbilayer phase found in biological lipids. Figure 4 is an electron micrograph of a freeze-fracture replica of 1,2 dilinlenoylmonogalactosylglycerol and is typical of a Hex II phase. The long tube-like structures are clearly evident. MGDG-like phosphatidylethanolamine favor the Hex II phase.13 The Hex II phase for both lipids appear at lower temperatures with an increase in the unsaturation of the acyl chains and can be easily detected by X-ray diffraction and by 31P NMR, in the case of the phospholipids. Transition from lamellar to Hex II can also be detected by differential scanning calorimetry though the transition enthalpy is small as compared to that of gel to liquid crystalline transition.6
Hexagonal liquid crystalline system containing cinnamaldehyde for enhancement of skin permeation of sinomenine hydrochloride
Published in Pharmaceutical Development and Technology, 2022
Jingbao Chen, Wu Long, Baoqi Dong, Wenxuan Cao, Xu Yuhang, Yun Meng, Chu Xiaoqin
In the experiment of frequency scanning, it can be concluded from Figure 6 that the complex viscosity (η*) of the LCC gels dropped as the shear rate increased, which indicates the characteristic of shear thinning. Then power law model was utilized to analyze the relation between frequency and complex viscosity (Equation: η* = Sωm) (Mishraki-Berkowitz et al. 2017). Table 3 showed that the m values of all LCC gels were between −1 and 0, which exhibited semi-solid behavior. The value of m reflects the phase behavior, when m is closer to 0, the system behaves more like a liquid, and when the value of m is closer to −1, the system behaves more like a solid. Meanwhile, S is the parameter of gel strength, indicating the intensity of intermolecular interaction. As exhibited in Table 3, it can be discovered that the S value of H4 was 19, 254, reflecting that the intensity of intermolecular interaction was the largest. It is assumed that in this case, the combination of effects attributed to the strong interaction of CA with the PT tail chain and SH interacted with the head groups of PT. The S value of the H2 was 14 431, showing the intensity of intermolecular interaction, it may be that the drug molecules were totally dissolved in the water channels. These results are consistent with previous SAXS analysis, lipophilic molecules obviously have an influence on nanostructures of the hexagonal phase.
Smart phase transformation system based on lyotropic liquid crystalline@hard capsules for sustained release of hydrophilic and hydrophobic drugs
Published in Drug Delivery, 2020
Xuejuan Zhang, Yujun Xiao, Zhengwei Huang, Jintian Chen, Yingtong Cui, Boyi Niu, Ying Huang, Xin Pan, Chuanbin Wu
The property of drug had great impact on their distribution in crystalline cell of cubic or hexagonal phase. Water channels and lipid bilayers built up the crystalline cell. Hydrophilic DOXY was most distributed in the water channels, where the release medium could penetrate in, and hence a rapid release was expected. Hydrophobic MLX would migrate into the lipid bilayers. Thus, its released from the crystalline cell had to break through the oil–water interface first, resulting a low release rate and incomplete release content. In addition, the hydrophilic property of DOXY was against the transformation process from lamellar phase with low viscosity to cubic or hexagonal phase with high viscosity, which benefited the water uptake and drug release. On the contrary, the attendance of MLX favored this process. The influence of hydrophilic molecules and hydrophobic molecules on the phase transformation of LLC can be explained in terms by the surfactant packing parameter P: v is the partial volume of the hydrophobic group, a is the area of head group, and l is the average length of the hydrophilic group (Mulet et al., 2013; Yamada, 2015).
Cubic and hexagonal liquid crystals as drug carriers for the transdermal delivery of triptolide
Published in Drug Delivery, 2019
Qian-Qian Shan, Xiao-Jing Jiang, Fang-Yuan Wang, Zi-Xuan Shu, Shuang-Ying Gui
Lyotropic liquid crystals (LLCs), which is composed of amphiphilic lipids that self-assembly in solvents, has attracted extensive attention due to its good performance of drug loading and drug release (Zabara & Mezzenga, 2014; Linkevičiūtė et al., 2015; Martiel et al., 2015). LLCs are usually classified as lamellar (Lα), reversed hexagonal (H2), and reversed cubic (V2) based on their different internal structures (Pershan, 1982; Kaasgaard & Drummond, 2006; Chen et al., 2014). In recent years, the cubic and hexagonal phases as the transdermal drug delivery system have received more attention. Their structures and chemical properties are similar to those of cell membranes, allowing drugs to penetrate the stratum corneum that facilitate the percutaneous penetration of drugs (Lopes et al., 2007; Maghraby, 2010; Marganit et al., 2012; Kadhum et al., 2016; Yu et al., 2016; Mei et al., 2018). Owing to these properties, V2 and H2 phases can be particularly used for the transdermal delivery system.