Alamethicin–lipid interaction studied by energy dispersive X-ray diffraction

A Comprehensive Review on Recent Advances and Patents of Niosomes

Niosomes are novel, self-assembled vesicular carriers that deliver both lipophilic and hydrophilic drugs at the specific site in a targeted way, enhancing bioavailability and extending therapeutic effects. Niosomes are a versatile drug delivery system with a diverse range of applications from gene to brain-targeted delivery and they are more attractive choices than liposomes as they are efficient at biodegrading. Niosome offers several advantages over conventional drug delivery systems, including enhanced stability, and also have gained a lot of focus in natural product delivery in recent years. This review provides a comprehensive view of niosomal research and recent advancements, including classification and fabrication methods, and their role in drug delivery and targeting. The description of the rise in niosomal formulation patents around the world is also elaborated along with the natural product delivery of niosomes which has recently gained significance. Patents on novel preparation, loading, and modification techniques have enhanced the importance of niosome in the pharmaceutical industry.

Functionalized niosomes as a smart delivery device in cancer and fungal infection

Various diseases remain untreated due to lack of suitable therapeutic moiety or a suitable drug delivery device, especially where toxicities and side effects are the primary reason for concern. Cancer and fungal infections are diseases where treatment schedules are not completed due to severe side effects or lengthy treatment protocols. Advanced treatment approaches such as active targeting and inhibition of angiogenesis may be preferred method for the treatment for malignancy over the conventional method. Niosomes may be a better alternative drug delivery carrier for various therapeutic moieties (either hydrophilic or hydrophobic) and also due to ease of surface modification, non-immunogenicity and economical. Active targeting approach may be done by targeting the receptors through coupling of suitable ligand on niosomal surface. Moreover, various receptors (CD44, folate, epidermal growth factor receptor (EGFR) & Vascular growth factor receptor (VGFR)) expressed by malignant cells have also been reviewed. The preparation of suitable niosomal formulation also requires considerable attention, and its formulation depends upon various factors such as selection of non-ionic surfactant, method of fabrication, and fabrication parameters. A combination therapy (dual drug and immunotherapy) has been proposed for the treatment of fungal infection with special consideration for surface modification with suitable ligand on niosomal surface to sensitize the receptors (C-type lectin receptors, Toll-like receptors & Nucleotide-binding oligomerization domain-like receptors) present on immune cells involved in fungal immunity. Certain gene silencing concept has also been discussed as an advanced alternative treatment for cancer by silencing the mRNA at molecular level using short interfering RNA (si-RNA).

Vertical ordering sensitivity of solid supported DPPC membrane to alamethicin and the related loss of cell viability

BACKGROUND

Experimental studies of antimicrobial peptides interacting with lipid membranes recently attracted growing interest due to their numerous biomedical applications. However, the influence of such peptides on the structural organisation of lipid membranes in connection with the actual cell response still remains an elusive issue.

METHODS

X-ray diffraction was employed on detecting the sensitivity of the periodical spacing of dipalmitoyl-phosphatidyl-choline stacked as solid-supported bilayers to the presence of varying amounts of the peptide alamethicin in a wide range of peptide-to-lipid molar ratios. These results were then correlated with the effects of alamethicin on biological membranes in vitro as observed by optical microscopy and microculture tetrazolium assay on the tumour cells HeLa to provide a comprehensive and quantitative analysis of these effects, based on a dose-response relationship.

RESULTS

The experiments allowed correlating the periodical spacing and the peptide-to-lipid molar ratio on alamethicin-dipalmitoyl-phosphatidyl-choline samples. Two different trends of periodical spacing vs. peptide-to-lipid molar ratio clearly appeared at low and high hydration levels, showing intriguing non-linear profiles. Unexpected correspondences were observed between the peptide-to-lipid molar ratio range where the changes in dipalmitoyl-phosphatidyl-choline structure occur and the alamethicin doses which alter the viability and the plasma membrane morphology of HeLa.

CONCLUSIONS

Alamethicin might induce either mechanical or phase changes on dipalmitoyl-phosphatidyl-choline bilayers. Such easily accessible ordering information was well-calibrated to predict the alamethicin doses necessary to trigger cell death through plasma membrane alterations.

GENERAL SIGNIFICANCE

This benchmark combined study may be valuable to predict bioeffects of several antimicrobial peptides of biomedical relevance.

Niosomes from 80s to present: the state of the art

Efficient and safe drug delivery has always been a challenge in medicine. The use of nanotechnology, such as the development of nanocarriers for drug delivery, has received great attention owing to the potential that nanocarriers can theoretically act as "magic bullets" and selectively target affected organs and cells while sparing normal tissues. During the last decades the formulation of surfactant vesicles, as a tool to improve drug delivery, brought an ever increasing interest among the scientists working in the area of drug delivery systems. Niosomes are self assembled vesicular nanocarriers obtained by hydration of synthetic surfactants and appropriate amounts of cholesterol or other amphiphilic molecules. Just like liposomes, niosomes can be unilamellar or multilamellar, are suitable as carriers of both hydrophilic and lipophilic drugs and are able to deliver drugs to the target site. Furthermore, niosomal vesicles, that are usually non-toxic, require less production costs and are stable over a longer period of time in different conditions, so overcoming some drawbacks of liposomes. The niosome properties are specifically dictated by size, shape, and surface chemistry which are able to modify the drug's intrinsic pharmacokinetics and eventual drug targeting to the areas of pathology. This up-to-date review deals with composition, preparation, characterization/evaluation, advantages, disadvantages and application of niosomes.

Temperature-dependent structural changes on DDAB surfactant assemblies evidenced by energy dispersive X-ray diffraction and dynamic light scattering

Cationic amphiphile DDAB (dimethyl-dioctadecyl-ammonium-bromide) can spontaneously form water-dispersed and solid supported mimicking biomembrane structures as well as valuable DNA delivery vehicles whose shape, stability and transfection efficiency can be easily optimized on varying temperature, water content and chemical composition. In this framework, disclosing the thermotropic behavior of DDAB assemblies can be considered as an essential step in conceiving and developing new non-viral vector systems. Our work has been focused primarily on understanding the mesophase structure of silicon supported DDAB thin film on varying temperature at constant relative humidity by energy dispersive X-ray diffraction (EDXD). Diffraction results have then been employed in providing a more comprehensive dynamic light scattering (DLS) analysis of corresponding thermotropic water dispersed vesicles made up of DDAB alone and in combination with helper lecithin DOPC (1,2-dioleoyl-sn-glycero-3-phosphatidylcholine) liposomes. We found that above 55 °C silicon-supported DDAB films undergo a significant thinning effect, whilst DDAB-water vesicles exhibit a reduction in size polydispersity. Upon cooling to 25 °C a distinct silicon supported DDAB mesophase, exhibiting a relative humidity-dependent spacing, has been pointed out, and modeled in terms of a lyotropic metastable gel-crystalline phase.DDAB/DOPC-water vesicles show a temperature-dependent switching in size distribution, leading to promising biomedical applications.