Prevention of fusion and leakage in freeze-dried liposomes by carbohydrates

Protecting Proteins from Desiccation Stress Using Molecular Glasses and Gels

Faced with desiccation stress, many organisms deploy strategies to maintain the integrity of their cellular components. Amorphous glassy media composed of small molecular solutes or protein gels present general strategies for protecting against drying. We review these strategies and the proposed molecular mechanisms to explain protein protection in a vitreous matrix under conditions of low hydration. We also describe efforts to exploit similar strategies in technological applications for protecting proteins in dry or highly desiccated states. Finally, we outline open questions and possibilities for future explorations.

Tableting of Fluidized Bed Granules Containing Living Microorganisms

Tablets are the favored dosage form for numerous active pharmaceutical ingredients, among others because they are easy to take, ensure safe dosing and allow cost-effective production on a large scale. This dosage form is also frequently chosen for the administration of viable probiotic microorganisms. Saccharomyces cerevisiae cells granulated in a fluidized bed process, with dicalcium phosphate (DCP), lactose (LAC) and microcrystalline cellulose (MCC) as carrier materials, were tableted using a compaction simulator, varying the compression stress. The tablets were analyzed regarding physical properties, e.g., porosity and tensile strength, as well as microbial survival. Carrier material and compression stress showed a significant influence on survival rate and physical tablet properties. The dependencies were related to material specific deformation characteristics and linked to mechanistic approaches to explain the different sensitivities.

Specific protection mechanism of oligosaccharides on liposomes during freeze-drying

Liposomes have been received much attention during the past decades as bioactive compounds carriers in food field. However, the application of liposomes is extremely limited by the structural instability during processing such as freeze-drying. In addition, the protection mechanism of lyoprotectant for liposomes during freeze-drying remains controversial. In this study, lactose, fructooligosaccharide, inulin and sucrose were used as lyoprotectants for liposomes and the physicochemical properties, structural stability and freeze-drying protection mechanism were explored. The addition of oligosaccharides could significantly suppress the changes in size and zeta potential, and the amorphous state of liposomes was negligible changed from XRD. The T_g of the four oligosaccharides, especially for sucrose (69.50 °C) and lactose (95.67 °C), revealed the freeze-dried liposomes had formed vitrification matrix, which could prevent liposomes from fusion via increasing the viscosity and reducing membrane mobility. The decrease in T_m of sucrose (147.67 °C) and lactose (181.67 °C), and the changes in functional group of phospholipid and hygroscopic capacity of lyophilized liposomes indicated oligosaccharides replaced water molecules to interact with phospholipids by hydrogen bonds. It can be concluded that the protection mechanism of sucrose and lactose as lyoprotectant was attributed to the combination of vitrification theory and water replacement hypothesis, while the water replacement hypothesis was dominated by fructooligosaccharide and inulin.

A mucoadhesive patch loaded with freeze-dried liposomes for the local treatment of oral tumors

Oral cancers affect millions of people globally, with increasing incidences among adults aged 35 and above. Poor drug uptake by lesions in the oral cavity following systemic administration, as well as limited localized treatment modalities for oral tumors, result in poor patient quality of life and high mortality. Here, we describe a solid, dissolvable, bioadhesive alginate patch containing freeze-dried doxorubicin-loaded liposomes as a local treatment for oral tumors located on the tongue. By varying the alginate-to-liposome ratio in the mucoadhesive patch, we could control the degree of bioadhesion to the tongue and the release profile of the drug-loaded liposomes from the matrix. In vitro, exposing squamous cell carcinoma (SCC) to the alginate mucoadhesive patch or tablet resulted in dose-dependent cancer-cell death. In vivo, the efficacy of the local treatment was demonstrated in mice bearing orthotopic SCC tumors in the tongue. The bioadhesive patch, applied directly above the lesion, significantly reduced the tumor size and treatment-associated side effects compared to implanted patches or systemic drug administration. This study demonstrates that local bioadhesive therapies are effective in treating cancers of the oral cavity.

Metal-phenolic networks as tuneable spore coat mimetics

Bacillus subtilis are important probiotic microbes currently formulated for delivery as spores, but their ability to germinate in the gut remains debatable. To optimize their application, cells should be delivered in their vegetative state, but the sensitivity of B. subtilis prevents this. Through the application of self-assembled metal-phenolic network (MPN) cellular coatings, B. subtilis are protected from lyophilization stresses. These MPNs are an important class of self-assembled materials comprised of polyphenols and metal ions, and the efficacy of MPN protection was found to be dependent on the MPN components used for assembly. Both the size of the polyphenol and stability of the metal-phenol coordination were important factors that influenced their cellular protection; the smallest polyphenol, gallic acid, and the most stable chelated ion, Fe^III, were found to provide the highest level of protection. Further, delivery to the gut involves exposure to acidic conditions in the form of stomach acid and intestinal fluid. MPN coatings rapidly disassemble upon mild acid treatment but were found to protect B. subtilis from the negative impacts of the acid. Overall, optimized MPNs were found to protect vegetative B. subtilis cells from lyophilization stress and enable a more complete understanding of the role of each component in MPNs.

Decoquinate liposomes: highly effective clearance of Plasmodium parasites causing severe malaria

Background

Severe malaria caused by Plasmodium falciparum leads to most malaria-related deaths globally. Decoquinate (DQ) displays strong activity against multistage infection by Plasmodium parasites. However, the development of DQ as an oral dosage form for the treatment of malaria at the blood stage has not been successful. In this study, liposome formulations of DQ were created for intravenous (IV) injection to suppress Plasmodium berghei, a parasite that causes severe malaria in mice.

Methods

DQ liposomes were prepared by conventional ethanol injection method with slight modifications and encapsulation efficiency evaluated by the well-established centrifugation method. Potency of the DQ liposomes against P. falciparum was assessed in vitro using freshly isolated human red blood cells. The efficacy of the DQ liposomes was examined in the mouse model of severe malaria.

Results

The DQ liposomes were around 150 nm in size and had the encapsulation efficiency rates > 95%. The freshly prepared and lyophilized liposomes were stable after storage at − 20 °C for 6 months. The liposomes were shown to have excellent activity against P. falciparum in vitro with DQ IC₅₀ 0.91 ± 0.05 nM for 3D7 (chloroquine sensitive strain) and DQ IC₅₀ 1.33 ± 0.14 nM for Dd2 (multidrug resistant strain), which were 18- and 14-fold more potent than artemisinin, respectively. Mice did not have any signs of toxicity after receiving high dose of the liposomes (DQ 500 mg/kg per mouse) by IV injection. In the mouse model of severe malaria, the liposomes had impressive efficacy against P. berghei with DQ ED₅₀ of 0.720 mg/kg.

Conclusion

The DQ liposomes prepared in this study were stable for long term storage and safe for IV injection in mammalian animals. The newly created liposome formulations had excellent activity against Plasmodium infection at the blood-stage, which encourages their application in the treatment of severe malaria.

Protection of Anaerobic Microbes from Processing Stressors Using Metal-Phenolic Networks

The gut microbiome is essential to maintain overall health and prevent disease, which can occur when these microbes are not in homeostasis. Microbial biotherapeutics are important to combat these issues, but they must be alive at the time of delivery for efficacy. Many potentially therapeutic species are anaerobes and thus are difficult to manufacture because of the limited efficacy of existing protective methods, making their production nearly impossible. We have developed a self-assembling cellular coating to improve the viability and stability of the next-generation biotherapeutic Bacteroides thetaiotaomicron. We show protection from both harsh processing conditions and oxygen exposure, even in the absence of canonical cryoprotectants. This advance will increase the range of microbes that can be stably manufactured and facilitate the development of emerging strains of interest by ensuring their postproduction viability.

Recent advances in liposome formulations for breast cancer therapeutics

Among many nanoparticle-based delivery platforms, liposomes have been particularly successful with many formulations passed into clinical applications. They are well-established and effective gene and/or drug delivery systems, widely used in cancer therapy including breast cancer. In this review we discuss liposome design with the targeting feature and triggering functions. We also summarise the recent progress (since 2014) in liposome-based therapeutics for breast cancer including chemotherapy and gene therapy. We finally identify some challenges on the liposome technology development for the future clinical translation.

Current Approaches of Preservation of Cells During (freeze-) Drying

The widespread application of therapeutic cells requires a successful stabilization of cells for the duration of transport and storage. Cryopreservation is currently considered the gold standard for the storage of active cells; however, (freeze-) drying cells could enable higher shelf life stability at ambient temperatures and facilitate easier transport and storage. During (freeze-) drying, freezing, (primary and secondary) drying and also the reconstitution step pose the risk of potential cell damage. To prevent these damaging processes, a wide range of protecting excipients has emerged, which can be classified, according to their chemical affiliation, into sugars, macromolecules, polyols, antioxidants and chelating agents. As many excipients cannot easily permeate the cell membrane, researchers have established various techniques to introduce especially trehalose intracellularly, prior to drying. This review aims to summarize the main damaging mechanisms during (freeze-) drying and to introduce the most common excipients with further details on their stabilizing properties and process approaches for the intracellular loading of excipients. Additionally, we would like to briefly explain recently discovered advantages of drying microorganisms, sperm, platelets, red blood cells, and eukaryotic cells, paying particular attention to the drying technique and residual moisture content.

Microstructured Lipid Carriers (MLC) Based on N-Acetylcysteine and Chitosan Preventing Pseudomonas aeruginosa Biofilm

The aim of this work was the development of microstructured lipid carriers (MLC) based on chitosan (CH) and containing N-acetylcysteine (NAC), a mucolytic and antioxidant agent, to inhibit the formation of Pseudomonas aeruginosa biofilm. MLC were prepared using the high shear homogenization technique. The MLC were characterized for morphology, particle size, Z potential, encapsulation efficiency and drug release. The antioxidant properties of NAC-loaded microstructured carriers were evaluated through an in vitro spectrophotometer assay. Finally, the activity of NAC-CH-MLC on biofilm production by Pseudomonas aeruginosa was also evaluated. Results obtained from this study highlighted that the use of chitosan into the inner aqueous phase permitted to obtain microstructured particles with a narrow size range and with good encapsulation efficiency. NAC-loaded MLC showed higher antioxidant activity than the free molecule, demonstrating how encapsulation increases the antioxidant effect of the molecule. Furthermore, the reduction of biofilm growth resulted extremely high with MLC being 64.74% ± 6.2% and 83.74% ± 9.95%, respectively, at 0.5 mg/mL and 2 mg/mL. In conclusion, this work represents a favorable technological strategy against diseases in which bacterial biofilm is relevant, such as cystic fibrosis.

Structural Comparison between Sucrose and Trehalose in Aqueous Solution

The two sugar molecules sucrose and trehalose are both considered as stabilizing molecules for the purpose of preserving biological materials during, for example, lyophilization or cryo-preservation. Although these molecules share a similar molecular structure, there are several important differences in their properties when they interact with water, such as differences in solubility, viscosity, and glass transition temperature. In general, trehalose has been shown to be more efficient than other sugar molecules in preserving different biological molecules against stress, and thus by investigating how these two disaccharides differ in their water interaction, it is possible to further understand what makes trehalose special in its stabilizing properties. For this purpose, the structure of aqueous solutions of these disaccharides was studied by using neutron and X-ray diffraction in combination with empirical potential structure refinement (EPSR) modeling. The results show that there are surprisingly few differences in the overall structure of the solutions, although there are indications for that trehalose perturbs the water structure slightly more than sucrose.

Sperm Micromotors for Cargo Delivery through Flowing Blood

Micromotors are recognized as promising candidates for untethered micromanipulation and targeted cargo delivery in complex biological environments. However, their feasibility in the circulatory system has been limited due to the low thrust force exhibited by many of the reported synthetic micromotors, which is not sufficient to overcome the high flow and complex composition of blood. Here we present a hybrid sperm micromotor that can actively swim against flowing blood (continuous and pulsatile) and perform the function of heparin cargo delivery. In this biohybrid system, the sperm flagellum provides a high propulsion force while the synthetic microstructure serves for magnetic guidance and cargo transport. Moreover, single sperm micromotors can assemble into a train-like carrier after magnetization, allowing the transport of multiple sperm or medical cargoes to the area of interest, serving as potential anticoagulant agents to treat blood clots or other diseases in the circulatory system.

Compression of Vectors for Small Interfering RNAs Delivery: Toward Oral Administration of siRNA Lipoplexes in Tablet Forms

Currently, most nonviral nucleic acid vectors are in the form of colloidal suspensions administered primarily parenterally. This type of formulation and the mode of administration impose strong constraints such as the size of the administered vectors or the production of sterile preparations. The tablet form provides access to easy oral administration, well accepted by patients; As regards nucleic acid vectors, a dry form represents an advance in terms of stability. Using an optimized lipid-based small interfering RNA-delivery system, we studied the tabletability of a liquid suspension of these vectors. We optimized the conditions of freeze-drying by choosing excipients and process, allowing for the conservation of both the gene-silencing efficacy of the formulated siRNAs and the supramolecular structure of the lipid particulate system. Gene-silencing efficacy was assayed on luciferase-expressing cells and the structure of the siRNA vector in freeze-dried and tablet forms was examined using small-angle X-ray scattering (SAXS) synchrotron radiation. The freeze-dried powders were then mixed with excipients necessary for the good progress of the compression by allowing for a regular supply of the matrix and the reduction of friction. The compression was carried out using a rotary press simulator that allows for complete monitoring of the compression conditions. After compression, formulated siRNAs retained more than 60% of their gene-silencing efficacy. Within the tablets, a specific SAXS signal was detectable and the lamellar and cubic phases of the initial liquid suspension were restored after resuspension of siRNA vectors by disintegration of the tablets. These results show that the bilayer lipid structures of the particles were preserved despite the mechanical constraints imposed by the compression. If such a result could be expected after the freeze-drying step, it was never shown, to our knowledge, that siRNA-delivery systems could retain their efficacy and structure after mechanical stress such as compression. This opens promising perspectives to oral administration of siRNA as an alternative to parenteral administration.

Structural lipids and carbohydrates of the deep mycelium of phoma-like micromycetes, potential mycoherbicides

The work is devoted to the mycelium biochemical composition of Stagonospora cirsii C-211, Calophoma complanata 32.121, Didymella macrostoma 32.52. These phylogenetically distant species of phoma-like micromycetes are the potential mycoherbicides of Cirsium arvense, Heracleum sosnowskyi, and Convolvulus arvensis, respectively. The S. cirsii C-211, C. complanata 32.121, D. macrostoma 32.52 mycelium in the early stationary growth phase was obtained on sucrose-soybean nutrient medium. It was shown that the lipid and carbohydrate (polyols, sugars) profiles of these strains have much in common. We suppose that levels of arabitol and trehalose influence to the stress-resistant of phoma-like micromycetes. In particularly, these carbohydrates serve structural and protective roles in the cell walls during osmotic and temperatures stress. The ratio of phosphatidylcholine to phosphatidylethanolamine and the proportion of phosphatidylserine among structural lipids also determine the properties of mycelium, and can be used to assess its quality.

Freeze-drying cycle optimization for the rapid preservation of protein-loaded liposomal formulations

Technology such as the use of microfluidics to generate liposomes has been well researched, yet the stabilisation of liposomal formulations is a major challenge to their greater implementation. To the best of our knowledge, this is the first study investigating the use of 96 well plates to freeze-dry ovalbumin (OVA) loaded neutral (DMPC:Chol and DSPC:Chol), anionic (DSPC:Chol:PS) and cationic (DSPC:Chol:DOTAP) liposomes. Through the use of high throughput screening, a freeze drying cycle was optimised; ramp freezing from from 4 °C to -45 °C, followed by primary drying at -30 °C and secondary drying at 30 °C under a vacuum of 0.1 mBar. These parameters maintained liposome physicochemical properties, with the liposomes remaining below 100 nm and were homogenous (polydispersity index of less than 0.2 post rehydration). Minimal leakage of the OVA protein was observed, with almost 100% OVA remaining encapsulated post rehydration of the formulations. Here we have identified a simple method that allows for the rapid screening and freeze-drying of a range of liposomal formulations.

Glucose Can Protect Membranes against Dehydration Damage by Inducing a Glassy Membrane State at Low Hydrations

The physical effects of small sugars on membranes have been studied for decades, primarily because of their membrane stabilization in cold or dehydrated environments. We studied the effects of up to 20 mol% glucose in bilayers made of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) at low hydration by combining X-ray diffraction and Molecular Dynamics (MD) simulations. In agreement with previous studies, we observe membrane thinning at low and membrane thickening at high sugar concentrations. Glucose was found to preferentially localize to the outer head region of phospholipid bilayers at all concentrations, and partitioning of sugar in the membranes was found to monotonically increase with increasing sugar concentration. While the number of gauche defects in the lipid acyl tails and the lipid packing in the presence of sugar resembled values of a fluid lipid bilayer, tail dynamics, as assessed by autocorrelation of the carbon atoms in the phospholipid tails, were slowed down significantly with increasing glucose content. Thus, our findings suggest that sugar leads to a a disordered, glassy state of the hydrophobic membrane core. The non-monotonic effect of glucose on membrane thickness was found to be an effect of fluidification at low concentrations and decreased interdigitation in the higher sugar concentration regime.

Freezing, Vitrification, and Freeze-Drying of Equine Spermatozoa: Impact on Mitochondrial Membrane Potential, Lipid Peroxidation, and DNA Integrity

Maintaining the integrity of equine sperm subjected to preservation protocols is essential for the successful development of assisted reproduction procedures. The aim of this study was to assess the mitochondrial membrane potential, lipid peroxidation, and DNA integrity of equine sperm subjected to freezing, vitrification, and freeze-drying. Eight ejaculates obtained from four Colombian Creole horses were subjected to programmable freezing, vitrification, and freeze-drying. After thawing or rehydration, sperm motility and kinetics were assessed through a CASA system. The mitochondrial membrane potential (ΔΨM), lipid peroxidation (LPO), and DNA fragmentation index (DFI) of the spermatozoa were assessed by flow cytometry using the DiOC6 (3), C11-Bodipy 581/591, and propidium iodide (PI) fluorescent dyes. The statistical analysis was conducted via generalized linear models, mean comparisons via the Duncan test, and a principal component analysis. A higher rate of spermatozoa with a high ΔΨM was found for freeze-drying (40.26 ± 7.79%) compared with freezing (21.82 ± 5.38%) and vitrification (5.32 ± 1.17%) (P < .05). Likewise, a higher rate of nonperoxidized viable spermatozoa (Bodipy-/PI-) was found for freeze-drying (35.98 ± 7.01%) in relation to frozen (10.34 ± 2.69%) and vitrified (7.07 ± 2.00%) sperm (P < .05). The DFI of vitrified spermatozoa (0.12 ± 0.04%) was higher when compared with the frozen (0.03 ± 0.01%) and freeze-dried (0.02 ± 0.01%) samples (P < .05). The researchers conclude that vitrification generates greater sperm alterations than freeze-drying and freezing, whereas freeze-drying produces lower LPO and higher ΔΨM for equine spermatozoa.

Development of a solid dosage platform for the oral delivery of bilayer vesicles

Within this work, we develop vesicles incorporating sub-unit antigens as solid dosage forms suitable for the oral delivery of vaccines. Using a combination of trehalose, dextran and mannitol, freeze-dried oral disintegrating tablets were formed which upon rehydration release bilayer vesicles incorporating antigen. Initial studies focused on the optimisation of the freeze-dry cycle and subsequently excipient content was optimised by testing tablet hardness, disintegration time and moisture content. The use of 10% mannitol and 10% dextran produced durable tablets which offered strong resistance to mechanical damage yet appropriate disintegration times and dispersed to release niosomes-entrapping antigen. From these studies, we have formulated a bilayer vesicle vaccine delivery system as rapid disintegrating tablets and capsules.

Calcium gluconate as cross-linker improves survival and shelf life of encapsulated and dried Metarhizium brunneum and Saccharomyces cerevisiae for the application as biological control agents

Calcium chloride (CC) is the most common cross-linker for the encapsulation of biocontrol microorganisms in alginate beads. The aim of this study was to evaluate if calcium gluconate (CG) can replace CC as cross-linker and at the same time improve viability after drying and rehydration, hygroscopic properties, shelf life and nutrient supply. Hence, the biocontrol fungi Metarhizium brunneum and Saccharomyces cerevisiae were encapsulated in Ca-alginate beads supplemented with starch. Beads were dried and maximum survival was found in beads cross-linked with CG. Beads prepared with CG showed lower hygroscopic properties, but a higher shelf life for encapsulated fungi. Moreover, we demonstrated that gluconate has a nutritive effect on encapsulated fungi, leading to increased mycelium growth of M. brunneum and to enhanced CO₂ release from beads containing Saccharomyces cerevisiae. The application of CG as cross-linker will pave the way towards increasing drying survival and shelf life of various, especially drying-sensitive microbes.

Liposomal nanocarriers for plasminogen activators

Several plasminogen activators (PAs) have been found effective in treating different thromboembolic diseases. However, administration of conventional thrombolytic therapy is limited by a low efficacy of present formulations of PAs. Conventional treatments using these therapeutic proteins are associated with several limitations including rapid inactivation and clearance, short half-life, bleeding complications or non-specific tissue targeting. Liposome-based formulations of PAs such as streptokinase, tissue-plasminogen activator and urokinase have been developed to improve the therapeutic efficacy of these proteins. Resulting liposomal formulations were found to preserve the original activity of PAs, promote their selective delivery and improve thrombus targeting. Therapeutic potential of these liposome-based PAs has been demonstrated successfully in various pre-clinical models in vivo. Reductions in unwanted side effects (e.g., hemorrhage or immunogenicity) as well as enhancements of efficacy and safety were achieved in comparison to currently existing treatment options based on conventional formulations of PAs. This review summarizes present achievements in: (i) preparation of liposome-based formulations of various PAs, (ii) development of PEGylated and targeted liposomal PAs, (iii) physico-chemical characterization of these developed systems, and (iv) testing of their thrombolytic efficacy. We also look to the future and the imminent arrival of theranostic liposomal formulations to move this field forward.

Influence of type and proportion of lyoprotectants on lyophilized ginsenoside Rg3 liposomes

Objectives

To improve stability and shelf life, lyophilized formulations of 20(R)-Ginsenoside Rg3 liposomes (G-Rg3-Ls) were prepared.

Methods

Glucose, trehalose, sucrose, maltose, lactose, mannitol, inositol, hydroxypropyl-β-cyclodextrin and polyethylene glycol were used as single lyoprotectant and then compared in terms of their ability to protect lyophilized G-Rg3-Ls. Further, a glucose–mannitol complex was used to determine the optimal lyophilized preparation. The analysis of lyophilized liposomes or lyoprotectant was further investigated by scanning electron microscopy, thermogravimetry-differential thermal analysis, X-ray diffractometry and Fourier transform infrared spectroscopy. Cytotoxicity assay was used to assess the cyto-inhibition of freshly prepared and lyophilized liposomes.

Key findings

When the ratio of glucose–mannitol to phospholipids was 4 : 2 : 1 (w/w) the lyophilized G-Rg3-Ls exhibited good appearance, high DRR (86.52% ± 5.02%), small change in particle size (45.83 ± 0.50%) and short rehydration reconstruction time (8.3 ± 1.5 s). All indices were considerably better than those of each single protective agent. Results indicated that when the two lyoprotectants were combined, the stabilizing effect of glucose and shaping effect of mannitol were well maintained. The cyto-inhibition of freshly prepared and lyophilized G-Rg3 liposomes showed that lyophilization did not affect the bioactivity of G-Rg3.

Conclusions

The application of glucose–mannitol composite lyoprotectants can obtain a good G-Rg3 lyophilized preparation.

Effect of Osmotic Pressure on the Stability of Whole Inactivated Influenza Vaccine for Coating on Microneedles

Enveloped virus vaccines can be damaged by high osmotic strength solutions, such as those used to protect the vaccine antigen during drying, which contain high concentrations of sugars. We therefore studied shrinkage and activity loss of whole inactivated influenza virus in hyperosmotic solutions and used those findings to improve vaccine coating of microneedle patches for influenza vaccination. Using stopped-flow light scattering analysis, we found that the virus underwent an initial shrinkage on the order of 10% by volume within 5 s upon exposure to a hyperosmotic stress difference of 217 milliosmolarity. During this shrinkage, the virus envelope had very low osmotic water permeability (1 - 6×10-4 cm s-1) and high Arrhenius activation energy (Ea = 15.0 kcal mol-1), indicating that the water molecules diffused through the viral lipid membranes. After a quasi-stable state of approximately 20 s to 2 min, depending on the species and hypertonic osmotic strength difference of disaccharides, there was a second phase of viral shrinkage. At the highest osmotic strengths, this led to an undulating light scattering profile that appeared to be related to perturbation of the viral envelope resulting in loss of virus activity, as determined by in vitro hemagglutination measurements and in vivo immunogenicity studies in mice. Addition of carboxymethyl cellulose effectively prevented vaccine activity loss in vitro and in vivo, believed to be due to increasing the viscosity of concentrated sugar solution and thereby reducing osmotic stress during coating of microneedles. These results suggest that hyperosmotic solutions can cause biphasic shrinkage of whole inactivated influenza virus which can damage vaccine activity at high osmotic strength and that addition of a viscosity enhancer to the vaccine coating solution can prevent osmotically driven damage and thereby enable preparation of stable microneedle coating formulations for vaccination.

A comprehensive production method of self-cryoprotected nano-liposome powders

This study provided a convenient approach for large scale production of hydrogenated soya phosphatidylcholine nano-liposome powders using beclometasone dipropionate as a model drug and sucrose as proliposome carrier. Fluid-bed coating was employed to manufacture proliposomes by coating sucrose with the phospholipid (5%, 10%, 15% and 20% weight gains), followed by hydration, size reduction using high pressure homogenization, and freeze-drying to yield stable nano-vesicles. High pressure homogenization was compared with probe-sonication in terms of liposome size, zeta potential and drug entrapment. Furthermore, the effect of freeze-drying on vesicle properties generated using both size reduction methods was evaluated. Results have shown that high-pressure homogenization followed by freeze-drying and rehydration tended to yield liposomes smaller than the corresponding vesicles downsized via probe-sonication, and all size measurements were in the range of 72.64-152.50 nm, indicating that freeze-drying was appropriate, regardless of the size reduction technique. The liposomes, regardless of size reduction technique and freeze drying had slightly negative zeta potential values or were almost neutral in surface charge. The entrapment efficiency of BDP in homogenized liposomes was found to increase following freeze-drying, hence the drug entrapment efficiency values in rehydrated liposomes were 64.9%, 57%, 69.5% and 64.5% for 5%, 10%, 15% and 20% weight gains respectively. In this study, we have reported a reliable production method of nano-liposomes based on widely applicable industrial technologies such as fluid-bed coating, high pressure homogenization and freeze-drying. Moreover, sucrose played a dual role as a carrier in the proliposome formulations and as a cryoprotectant during freeze-drying.

Long-term storage of lyophilized liposomal formulations

Because aqueous liposomal formulations containing multiply unsaturated lipids are susceptible to chemical degradation, these formulations are often lyophilized. Despite their limited chemical stability, interest in the use of multiply unsaturated lipids to promote intracellular delivery has increased considerably in recent years. The goal of the current study was to examine the long-term storage stability of lyophilized formulations containing lipids with increasing levels of unsaturation, and various strategies that can be employed to improve stability. Aqueous lipid-trehalose formulations containing 1,2-dilinolenoyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLinPC), or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were lyophilized and stored at temperatures ranging from 4°C to 60°C. We observed that the lipid degradation rate increased as the storage temperature and unsaturation level were increased. Even the cleanest sugars, which are available commercially, contain iron contaminants, and it was observed that the chelation of these iron contaminants significantly improved the stability of DLPC during storage. However, the glass transition temperature of the sugar that was included in the formulation, the reduction of the oxygen in the aqueous sample prior to lyophilization, the inclusion of helper lipids (i.e., cholesterol), and the rate of freezing did not significantly improve stability.

Physico-chemical characterisation of cationic DOTAP liposomes as drug delivery system for a hydrophilic decapeptide before and after freeze-drying

In the present study, positively charged 1,2-dioleoyloxy-3-trimethylammoniumpropane (DOTAP) liposomes as a delivery system for a hydrophilic decapeptide were developed. The main objective was the preparation of a stable, highly loaded, lyophilised formulation to yield the basis for an acceptable shelf life. The influences of addition of cholesterol, pH value, amounts of lipid and peptide, type and amount of sugar-based cryoprotective agent (trehalose and sucrose), and time point for cryoprotector addition as well as the freeze-drying process parameters were investigated. The collapse temperatures of the liposome dispersions in the presence of the disaccharides trehalose and sucrose were determined using a freeze-drying microscope (Lyostat 2). The liposome morphology before freeze-drying was determined by transmission electron microscopy (TEM). The evidence of intact liposomes after freeze-drying was shown by scanning electron microscope (SEM) imaging. In summary, this study demonstrated the successful development of DOTAP liposomes including their lyophilisation as a drug delivery system for small hydrophilic peptides.

Programming desiccation-tolerance: from plants to seeds to resurrection plants

Desiccation-tolerance (DT) evolved as the key solution to survival on land by the early algal ancestors of terrestrial plants. This 'first' DT involved utilizing rapidly mobilisable repair mechanisms and is still found today in mosses, such as Tortula ruralis, and ferns, such as Mohria caffrorum. The first seed plants lost vegetative DT while investing their seeds with tolerance mechanisms improving their survival in unfavourable environments. The mechanisms of DT in seeds are strongly connected to their developmentally regulated maturation programs. We propose that angiosperm resurrection plants acquired tolerance by re-activating their innate DT mechanisms in their vegetative tissues. Here we review the current hypotheses regarding the genetic evidence for the evolution of DT in resurrection plants. We also present strong evidence showing the activation of seed specific genetic elements in the vegetative tissues of resurrection plants.

Emerging Role for Use of Liposomes in the Biopreservation of Red Blood Cells

SUMMARY: Biopreservation is the process of maintaining the integrity and functionality of cells held outside the native environment for extended storage times. The development of red blood cell (RBC) biopreservation techniques that maintain in vitro RBC viability and function represents the foundation of modern blood banking. The biopreservation of RBCs for clinical use can be categorized based on the techniques used to achieve biologic stability, including hypothermic storage and cryopreservation. This review will examine the emerging role of liposomes in the RBC biopreservation, including the incorporation of liposomes into RBC membranes as an effective approach for minimizing RBC hypothermic storage membrane lesion and use of liposomes as a permeabilization strategy for the intracellular accumulation of novel intracellular cryoprotectants. Integration of current biopreservation research with blood banking practices offers enormous potential for future improvements of safety and efficacy of RBC transfusion.

The Stability and Shelf-Life of Liposome Encapsulated Hemoglobin: A Potential Blood Substitute

For any viable blood substitute, questions of long-term storage and shelf-life must be addressed. Recently, we have made great progress in improving the stability of the blood substitute, liposome encapsulated hemoglobin (LEH). We have concentrated our efforts on protecting LEH in solution and in the long-term preservation of LEH by lyophilization. In particular, we have been able to retard and in some cases, reverse the oxidative process of metHb formation in solution by the addition of antioxidants such as NADH and glutathione. We have been able to regenerate Hb preparations with 60% metHb by the addition of 10 mM NADH and glutathione. In these preparations addition of these antioxidants results in a decrease of metHb levels from 62% to 15% over the course of 12.5 days at 4°C. We have also explored the use of protective solutes such as the disaccharide trehalose in the preservation of LEH in the freeze-dried state. Addition of increasing amounts of trehalose and other disaccharides results in the inhibition of lyophilization-induced fusion events and in the retention of hemoglobin within the unilamellar liposomal vesicles following rehydration.

Trehalose and trehalose-based polymers for environmentally benign, biocompatible and bioactive materials

Trehalose is a non-reducing disaccharide that is found in many organisms but not in mammals. This sugar plays important roles in cryptobiosis of selaginella mosses, tardigrades (water bears), and other animals which revive with water from a state of suspended animation induced by desiccation. The interesting properties of trehalose are due to its unique symmetrical low-energy structure, wherein two glucose units are bonded face-to-face by 1→1-glucoside links. The Hayashibara Co. Ltd., is credited for developing an inexpensive, environmentally benign and industrial-scale process for the enzymatic conversion of α-1,4-linked polyhexoses to α,α-d-trehalose, which made it easy to explore novel food, industrial, and medicinal uses for trehalose and its derivatives. Trehalose-chemistry is a relatively new and emerging field, and polymers of trehalose derivatives appear environmentally benign, biocompatible, and biodegradable. The discriminating properties of trehalose are attributed to its structure, symmetry, solubility, kinetic and thermodynamic stability and versatility. While syntheses of trehalose-based polymer networks can be straightforward, syntheses and characterization of well defined linear polymers with tailored properties using trehalose-based monomers is challenging, and typically involves protection and deprotection of hydroxyl groups to attain desired structural, morphological, biological, and physical and chemical properties in the resulting products. In this review, we will overview known literature on trehalose’s fascinating involvement in cryptobiology; highlight its applications in many fields; and then discuss methods we used to prepare new trehalose-based monomers and polymers and explain their properties.

Effects of different freezing parameters on the morphology and viability of preantral follicles after cryopreservation of doe rabbit ovarian tissue

OBJECTIVE

To compare the effects of dimethyl sulfoxide (DMSO), 1,2-propanediol (PROH), sucrose, trehalose, concentration of cryoprotectants, equilibration method, and postseeding freezing rate on doe rabbit ovarian tissue preservation after freezing, using fractional experimental design.

DESIGN

Experimental prospective study.

SETTING

Research institute in veterinary and agronomic colleges.

ANIMAL(S)

Californian doe rabbits.

INTERVENTION(S)

Ovarian cortices were prepared from ovaries collected in slaughterhouse. Fractional experimental design was used to evaluate simultaneously five chemophysical factors influencing the cryopreservation of ovarian tissue.

MAIN OUTCOME MEASURE(S)

Follicle viability by Live/Dead viability/cytotoxicity kit and histologic evaluation of the ovarian tissue.

RESULT(S)

Experimental design suggests that equilibration method and cryoprotectant concentration have no effect on the proportion of normal follicles. Penetrating and nonpenetrating cryoprotectants seems to influence the preservation of the follicles with advantage for PROH and trehalose. The follicular preservation seems to be highly influenced by the postseeding freezing rate. Freezing rate of 0.3 degrees C/min seems to be less deleterious than 2 degrees C/min. Morphologic preservation ratio reaches 85% using PROH and trehalose.

CONCLUSION(S)

Cryopreservation of doe rabbit ovarian tissue using conventional cryoprotectant and 0.3 degrees C/min as freezing rate seems to be a promising technique and could be used as a model for women.