Cryo-responses of two types of large unilamellar vesicles in the presence of non-permeable or permeable cryoprotecting agents

Lyophilization enhances the stability of Panax notoginseng total saponins-loaded transfersomes without adverse effects on ex vivo/in vivo skin permeation

Transfersomes (TFSs) have been extensively investigated to enhance transdermal drug delivery. As a colloidal dispersion system, TFSs are prone to problems such as particle aggregation and sedimentation, oxidation and decomposition of phospholipids. To enhance the stability of panax notoginseng saponins (PNS)-loaded transfersomes (PNS-TFSs) without adverse influences on their skin permeation, we prepared lyophilized PNS-loaded transfersomes (PNS-FD-TFSs), clarified their physicochemical characteristics and investigated their in vitro drug release, ex vivo skin permeation/deposition and in vivo pharmacokinetics. In this study, a simple, fast and controllable process was developed for preparing lyophilized PNS-TFSs. In the optimized PNS-FD-TFS formulation, sucrose and trehalose were added to the PNS-TFS dispersion with a mass ratio of trehalose, sucrose, and phospholipid of 3:2:1, and the mixture was frozen at -80 °C for 12 h followed by lyophilization at -45 °C and 5 Pa for 24 h. The optimized formulation of PNS-FD-TFSs was screened based on the appearance and reconstitution time of the lyophilized products, vesicle size, and PDI of the freshly reconstituted dispersions. It maintained stable physicochemical properties for at least 6 months at 4 °C. The vesicle size of PNS-FD-TFSs was below 100 nm and homogenous with a polydispersity index of 0.2 after reconstitution. The average encapsulation efficiencies of the five index saponins notoginsenoside R1 (NGR1), ginsenoside Rg1 (GRg1), ginsenoside Re (GRe), ginsenoside Rb1 (GRb1) and ginsenoside Rd (GRd) in PNS-FD-TFSs were 68.41 ± 5.77%, 68.95 ± 6.08%, 65.46 ± 10.95%, 91.50 ± 5.62% and 95.78 ± 1.70%, respectively. The reconstituted dispersions of PNS-FD-TFSs were similar to PNS-TFSs in in vitro release, ex vivo skin permeation, and deposition. The pharmacokinetic studies showed that, compared with the PNS liposomes (PNS-LPS), the PNS-FD-TFS-loaded drug could permeate through the skin and enter the blood rapidly. It can be concluded that the lyophilization process can effectively improve the stability of PNS-TFSs without compromising their transdermal absorption properties.

Cryopreservation of Plant Shoot Tips of Potato, Mint, Garlic, and Shallot Using Plant Vitrification Solution 3

Cryopreservation of shoot tips facilitates long-term storage of plant genetic resources which can otherwise only be propagated vegetatively. The vitrification approach using the cryoprotectant plant vitrification solution 3 (PVS3, 50% sucrose and 50% glycerol) is easy to handle, has shown to produce high regrowth percentages in a number of potato, mint, garlic, and shallot accessions, and is, thus, highly suitable for routine cryopreservation of plant genetic resources. In the current chapter, the vitrification procedure is described for potato, mint, garlic, and shallot and includes details about modifications for the different plant species. Special emphasis is given on the preparation of the different culture media, solutions, the culture conditions prior and post-cryopreservation, and the preparation of the shoot tips from different sources. Furthermore, protocols to introduce plants into in vitro culture and methods to estimate cryopreservation success are provided.

Lyophilized liposome-based parenteral drug development: Reviewing complex product design strategies and current regulatory environments

Given the successful entry of several liposomal drug products into market, and some with decades of clinical efficacy, liposomal drug delivery systems have proven capabilities to overcome certain limitations of traditional drug delivery, especially for toxic and biologic drugs. This experience has helped promote new liposomal approaches to emerging drug classes and current therapeutic challenges. All approved liposomal dosage forms are parenteral formulations, a pathway demonstrating greatest safety and efficacy to date. Due to the intrinsic instability of aqueous liposomal dispersions, lyophilization is commonly applied as an important solution to improve liposomal drug stability, and facilitate transportation, storage and improve product shelf-life. While lyophilization is a mature pharmaceutical technology, liposome-specific lyophilization platforms must be developed using particular lyophilization experience and strategies. This review provides an overview of liposome formulation-specific lyophilization approaches for parenteral use, excipients used exclusively in liposomal parenteral products, lyophilized liposome formulation design and process development, long-term storage, and current regulatory guidance for liposome drug products. Readers should capture a comprehensive understanding of formulation and process variables and strategies for developing parenterally administered liposomal drugs.

PEGylation and surface functionalization of liposomes containing drug nanocrystals for cell-targeted delivery

Liposomal formulations have important therapeutic applications in anti-cancer treatments but current formulations suffer from serious side effects, high dosage requirements and prolonged treatment. In this study, PEGylated azide-functionalized liposomes containing drug nanocrystals were investigated with the aim of increasing the drug payload and achieving functionalization for targeted delivery. Liposomes were characterized using cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), small and ultra-small angle neutron scattering (SANS/USANS) and small and wide angle X-ray scattering (SAXS/WAXS). Cryo-TEM experiments revealed the dimensions of the nanocrystal-loaded liposomes and the change of shape from spherical to elongated after the formation of nanocrystals. Results from SANS/USANS experiments confirmed the asymmetric particle shape. SAXS/WAXS experiments confirmed that the crystalline drug only occurred in freeze-thawed samples and correlated with a new unidentified polymorphic form of ciprofloxacin. Using a small molecule dye, dibenzocyclooctyne (DBCO)-cy5, specific conjugation between DBCO groups and surface azide groups on the liposomes was confirmed; this indicates the promise of this system for tumour-targeted delivery.

Changes of soluble sugars and ATP content during DMSO droplet freezing and PVS3 droplet vitrification of potato shoot tips

The potato's great genetic diversity needs to be maintained for future agricultural applications and can be preserved at ultra-low temperatures. To decipher detailed physiological processes, the aim of the study was to analyze the regrowth in 28 gene bank accessions and to reveal metabolite changes in a subset of four accessions that showed pronounced differences after shoot tip cryopreservation using DMSO droplet freezing and PVS3 droplet vitrification. Regrowth varied in all 28 genotypes ranging from 5% ('Kagiri') to 100% ('Karakter') and was higher after PVS3 droplet vitrification (71 ± 19%) than after cryopreservation using DMSO (54 ± 17%). Sucrose, glucose, and fructose were analyzed and showed significant increases after pre-culture in combination with PVS3 or DMSO and liquid nitrogen treatment and were reduced during regeneration. In contrast, adenosine triphosphate (ATP) reached its minimum concentration after cryoprotection and liquid nitrogen treatment and recovered most quickly after PVS3 droplet vitrification. A shortening of the explant pre-culture period reduced dramatically the regrowth after PVS3 vitrification. However, correlations between the shoot tip regrowth and sugar concentration were absent and significant at a low extent with ATP (r = 0.4, P < 0.01). Interestingly, several sub-cultivations of the donor plants from the previous stock affected negatively the regrowth. In conclusion, the cryopreservation protocol, genotypes, pre-culture period and number of sub-cultures affect the regrowth ability of explants, which was best estimated by the ATP concentration after low-temperature treatment. Due to the superior performance of PVS3, the routine potato cryopreservation at the Gatersleben gene bank was changed to PVS3 droplet vitrification.

Formation of drug nanocrystals under nanoconfinement afforded by liposomes

In response to freeze–thaw, liposome-encapsulated antibiotic (A) is converted into nanocrystalline form (B) resulting in an attenuated drug release profile.

Cyclodextrin as membrane protectant in spray-drying and freeze-drying of PEGylated liposomes

In this study it was investigated whether hydroxypropyl-β-cyclodextrin (HPβCD) is able to stabilize the liposomal membranes during drying of long circulating polyethylene glycol (PEG) coated liposomes, as compared to the disaccharides trehalose and sucrose. PEGylated liposomes loaded with prednisolone disodium phosphate (PLP) were dried by spray-drying or freeze-drying. The dried powders were tested on their residual moisture content, glass transition temperature and amorphous character. Upon reconstitution the liposomal size, size distribution and drug retention were determined and the results were compared to the characteristics of the formulation solution before drying. In contrast to the disaccharides, HPβCD stabilizes the liposomal membranes of the PEGylated liposomes during the drying process of both spray drying and freeze-drying when present in a lipid:carbohydrate ratio of 1:6 (w/w). The resulting powder can be stored at room temperature. No changes in size and size distribution were seen upon reconstitution of the HPβCD containing formulations. Drying resulted in a minimal leaking of PLP from the liposomes. Its relatively high [Formula: see text] and T(g) of HPβCD, as compared to the disaccharides, make HPβCD an excellent membrane protectant for dry PEGylated liposomal formulations.