Spyridon Mourtas

Effect of curcumin-associated and lipid ligand-functionalized nanoliposomes on aggregation of the Alzheimer's Aβ peptide.

The effect of various types of nanoliposomes (associated with curcumin, phosphatidic acid, cardiolipin, or GM1 ganglioside) on the aggregation of the amyloid-β(1-42) (Aβ(1-42)) peptide was investigated. Nanoliposomes incorporating curcumin (curcumin-liposomes) were prepared by adding curcumin in the lipid phase during liposome preparation, whereas curcumin surface-decorated liposomes were prepared by using a curcumin-lipid conjugate (lipid-S-curcumin liposomes) or by attaching a curcumin derivative on preformed liposomes by click chemistry (click-curcumin liposomes). The lipid ligands (phosphatidic acid, cardiolipin, or GM1) were also incorporated into nanoliposomes during their formation. All nanoliposomes with curcumin, or the curcumin derivative, were able to inhibit the formation of fibrillar and/or oligomeric Aβ in vitro. Of the three forms of curcumin liposomes tested, the click-curcumin type was by far the most effective. Liposomes with lipid ligands only inhibited Aβ fibril and oligomer formation at a very high ratio of liposome to peptide. Curcumin-based liposomes could be further developed as a novel treatment for Alzheimers disease.

pH-Responsive Hydrogel/Liposome Soft Nanocomposites For Tuning Drug Release

A novel liposome/hydrogel soft nanocomposite was explored as a controlled drug delivery system. A P2VP-PAA-PnBMA biocompatible, pH-responsive triblock terpolymer was used as an injectable gelator, entrapping PC/Chol liposomes loaded with calcein as hydrophilic model drug. The composite hydrogel was formed in vitro through a pH-induced sol-gel transition by dialysis against buffer under physiological conditions and at polymer concentration as low as 1 wt %. Excellent control of the calcein release was achieved just by adjusting the gelator concentration; that is, from 1 to 1.5 wt %, the drug release period was significantly prolonged from 14 to 32 days.

Curcumin-conjugated nanoliposomes with high affinity for Aβ deposits: Possible applications to Alzheimer disease

UNLABELLED Accumulation of amyloid peptide (Aβ) in senile plaques is a hallmark lesion of Alzheimer disease (AD). The design of molecules able to target the amyloid pathology in tissue is receiving increasing attention, both for diagnostic and for therapeutic purposes. Curcumin is a fluorescent molecule with high affinity for the Aβ peptide but its low solubility limits its clinical use. Curcumin-conjugated nanoliposomes, with curcumin exposed at the surface, were designed. They appeared to be monodisperse and stable. They were non-toxic in vitro, down-regulated the secretion of amyloid peptide and partially prevented Aβ-induced toxicity. They strongly labeled Aβ deposits in post-mortem brain tissue of AD patients and APPxPS1 mice. Injection in the hippocampus and in the neocortex of these mice showed that curcumin-conjugated nanoliposomes were able to specifically stain the Aβ deposits in vivo. Curcumin-conjugated nanoliposomes could find application in the diagnosis and targeted drug delivery in AD. FROM THE CLINICAL EDITOR In this preclinical study, curcumin-conjugated nanoliposomes were investigated as possible diagnostics and targeted drug delivery system in Alzheimers disease, demonstrating strong labeling of Aβ deposits both in human tissue and in mice, and in vitro downregulation of amyloid peptide secretion and prevention of Aβ-induced toxicity.

Multifunctional nanoliposomes with curcumin-lipid derivative and brain targeting functionality with potential applications for Alzheimer disease.

With the objective to formulate multifunctional nanosized liposomes to target amyloid deposits in Alzheimer Disease (AD) brains, a lipid-PEG-curcumin derivative was synthesized and characterized. Multifunctional liposomes incorporating the curcumin derivative and additionally decorated with a Blood Brain Barrier (BBB) transport mediator (anti-Transferin antibody) were prepared and characterized. The fluorescence intensity of curcumin derivative was found to increase notably when the curcumin moiety was in the form of a diisopropylethylamine (DIPEA) salt. Both curcumin-derivative liposomes and curcumin-derivative Anti-TrF liposomes showed a high affinity for the amyloid deposits, on post-mortem brains samples of AD patients. The ability of both liposomes to delay Aβ1-42 peptide aggregation was confirmed by Thioflavin assay. However, the decoration of the curcumin-derivative liposomes with the Anti-TrF improved significantly the intake by the BBB cellular model. Results verify that the attachment of an antibody on the curcumin-liposome surface does not block deposit staining or prevention of Aβ aggregation, while the presence of the curcumin-PEG-lipid conjugate does not reduce their brain-targeting capability substantially, proving the potential of such multifunctional NLs for application in Alzheimer disease treatment and diagnosis.

Magnetoliposomes with high USPIO entrapping efficiency, stability and magnetic properties

The DRV technique (followed by extrusion) was used for construction of hydrophilic-USPIO encapsulating liposomes. Magnetoliposomes (ML) were characterized for size, surface charge, entrapment, physical stability and magnetic properties (relaxivity). Results show that nanosized extruded-DRV MLs encapsulate higher amounts of USPIOs in comparison with sonicated vesicles. Fe (III) encapsulation efficiency (EE) is 12%, the highest reported to date for nanosized MLs. EE of MLs is influenced by ML membrane composition and polyethyleneglycol (PEG) coating. PEG-coating increases ML EE and stability; however, r(2)-to-r(1) ratios decrease (in comparison with non-PEGylated MLs). Most ML-types are efficient T2 contrast agents (because r(2)-to-r(1) ratios are higher than that of free USPIOs). Targeted MLs were formed by successfully immobilizing OX-26 monoclonal antibody on ML surface (biotin-streptavidin ligation), without significant loss of USPIOs. Targeted MLs retained their nanosize and integrity during storage for 1 month at 4 °C and up to 2 weeks at 37 °C.

Protective properties of non-nucleoside reverse transcriptase inhibitor (MC1220) incorporated into liposome against intravaginal challenge of Rhesus Macaques with RT-SHIV

In the absence of an effective vaccine against HIV, it is urgent to develop an effective alternative such as a microbicide. Single and repeated applications of MC1220 microbicide were evaluated in macaques. First, animals were given a single application of 0.5% or 1.5% MC1220-containing liposomal gel. A second group were treated with 0.5% MC1220 once a day for 4 days. The control groups were treated by liposomal gel alone. Thirty minutes after the last application, animals were challenged with RT-SHIV. In the first protocol, 2 of 4 animals treated by 0.5% of the MC1220 and 2 of 5 treated by 1.5% were protected. In the second protocol, 3 of 5 treated animals were protected and 5 of 5 controls were infected. The RNA viral load at necropsy was significantly lower (p=0.05) in treated-infected animals than in controls. In both protocols, the number of CD4+ T cells was lower at viremia peak in infected than in protected animals.

Covalent immobilization of liposomes on plasma functionalized metallic surfaces.

A method was developed to functionalize biomedical metals with liposomes. The novelty of the method includes the plasma-functionalization of the metal surface with proper chemical groups to be used as anchor sites for the covalent immobilization of the liposomes. Stainless steel (SS-316) disks were processed in radiofrequency glow discharges fed with vapors of acrylic acid to coat them with thin adherent films characterized by surface carboxylic groups, where liposomes were covalently bound through the formation of amide bonds. For this, liposomes decorated with polyethylene glycol molecules bearing terminal amine-groups were prepared. After ensuring that the liposomes remain intact, under the conditions applying for immobilization; different attachment conditions were evaluated (incubation time, concentration of liposome dispersion) for optimization of the technique. Immobilization of calcein-entrapping liposomes was evaluated by monitoring the percent of calcein attached on the surfaces. Best results were obtained when liposome dispersions with 5mg/ml (liposomal lipid) concentration were incubated on each disk for 24h at 37°C. The method is proposed for developing drug-eluting biomedical materials or devices by using liposomes that have appropriate membrane compositions and are loaded with drugs or other bioactive agents.

Increasing the stability of curcumin in serum with liposomes or hybrid drug-in-cyclodextrin-in-liposome systems: A comparative study

Curcumin (CURC) was incorporated in liposomes as free drug or after formation of hydropropyl-β- or hydroxypropyl-γ-cyclodextrin (HPβCD or HPγCD) complexes prepared by coprecipitation and characterized by X-ray diffractometry. Liposomes encapsulating CURC as free drug or CD-complexes (hybrid formulations) were prepared by the dehydration-rehydration vesicle (DRV) method followed by extrusion, and characterized for size, zeta-potential and CURC loading. CURC stability (at 0.01 and 0.05 mg/mL) in 80% (v/v) fetal bovine serum (FBS) was evaluated at 37 °C. Results demonstrate that HPβCD stabilizes CURC more than HPγCD, but liposome encapsulation provides substantially more protection, than CDs. CURC stabilization is similar, when encapsulated as free compound or CD-complex. However, the last method increases CURC loading by 23 times (depending on the lipid composition of liposomes and the CD used), resulting in higher solubility. The stability profile of CURC in serum depends on the composition of liposomes and CURC concentration, since at lower concentrations larger CURC fractions are protected due to protein binding. Compared to the corresponding CD complexes, hybrid formulations provide intermediate CURC solubility (comparable to HPβCD) but profoundly higher stabilization.

Stability of protein-encapsulating DRV liposomes after freeze-drying: A study with BSA and t-PA.

Stability of protein-encapsulating DRV (dried-rehydrated vesicle) liposomes is evaluated after freeze-drying vesicles in presence (or not) of trehalose. Two proteins, bovine serum albumin (BSA) and tissue-type plasminogen activator (t-PA), are used, and protein-encapsulating liposomes with different lipid compositions are prepared by DRV technique. Encapsulation efficiencies are calculated, after measuring BSA with a fluorescence technique and t-PAs amidolytic activity toward a chromogenic substrate. Experimental results show that encapsulation of BSA in vesicles ranges between 35 and 53% of the protein and is only slightly affected by lipid composition. For t-PA, entrapment efficiencies are lower, ranging between 2 and 16%, while lipid composition has substantial effect on entrapment (cholesterol inclusion is very important). After freeze-drying, some lipid compositions remain stable, retaining most of initially entrapped proteins, while others do not, but they may be stabilized by trehalose. In the case of BSA, liposome behavior cannot be explained based on lipid membrane rigidity (more rigid = more stable). This may be connected with previously demonstrated interactions of BSA with membranes. Oppositely, t-PA behavior is more predictable, meaning that the lipid composition selected for the specific therapeutic application determines the need for cryoprotectant addition before freeze-drying t-PA containing DRV liposomes, perhaps due to the fact that under conditions applying minimum or no interactions between t-PA and lipid membranes occur. Thereby, interactions between proteins and membranes determine not only the encapsulation efficiency but also the need for cryopreservation of liposomal protein formulations.

Recent advancements in liposomes targeting strategies to cross blood-brain barrier (BBB) for the treatment of Alzheimer's disease

Abstract In this modern era, with the help of various advanced technologies, medical science has overcome most of the health‐related issues successfully. Though, some diseases still remain unresolved due to various physiological barriers. One such condition is Alzheimer; a neurodegenerative disorder characterized by progressive memory impairment, behavioral abnormalities, mood swing and disturbed routine activities of the person suffering from. It is well known to all that the brain is entirely covered by a protective layer commonly known as blood brain barrier (BBB) which is responsible to maintain the homeostasis of brain by restricting the entry of toxic substances, drug molecules, various proteins and peptides, small hydrophilic molecules, large lipophilic substances and so many other peripheral components to protect the brain from any harmful stimuli. This functionally essential structure creates a major hurdle for delivery of any drug into the brain. Still, there are some provisions on BBB which facilitate the entry of useful substances in the brain via specific mechanisms like passive diffusion, receptor‐mediated transcytosis, carrier‐mediated transcytosis etc. Another important factor for drug transport is the selection of a suitable drug delivery systems like, liposome, which is a novel drug carrier system offering a potential approach to resolving this problem. Its unique phospholipid bilayer structure (similar to physiological membrane) had made it more compatible with the lipoidal layer of BBB and helps the drug to enter the brain. The present review work focused on various surface modifications with functional ligand (like lactoferrin, transferrin etc.) and carrier molecules (such as glutathione, glucose etc.) on the liposomal structure to enhance its brain targeting ability towards the successful treatment of Alzheimer disease. Graphical abstract Figure. No Caption available.