Sarina Grinberg

Cationic vesicles from novel bolaamphiphilic compounds

Effective targeted drug delivery by cationic liposomes is difficult to achieve because of their rapid clearance from the blood circulation. Bolaamphiphiles that form monolayer membrane may provide vesicles with improved stability, as shown for archaeosomes. We investigated a series of bolaamphiphiles with acetylcholine head groups and systematic structural changes in their hydrophobic domain for their ability to form stable nanovesicles. Bolaamphiphiles with two aliphatic chains separated by a short amide midsection produced spherical nanovesicles ranging in diameter from 80 to 120 nm. These vesicles lost their encapsulated material within 24 hours of incubation in phosphate-buffered saline (PBS). Similar bolaamphiphiles with a longer midsection produced a mixture of fibers and more stable nanovesicles. Bolaamphiphiles with ester amide midsection produced only spherical nanovesicles that were stable during incubation in PBS for several days. Vesicles made from bolaamphiphiles with acetylcholine head groups conjugated to the aliphatic chain via the amine were less stable than vesicles made from bolaamphiphiles with head groups conjugated to the aliphatic chain via the acetyl group. Vesicles that were stable in vitro showed good stability in the blood circulation after intravenous administration to mice. These results help in elucidating the bolaamphiphile structures needed to form stable cationic vesicles for targeted drug delivery.

Delivery of proteins to the brain by bolaamphiphilic nano-sized vesicles.

Bolaamphiphilic cationic vesicles with acetylcholine (ACh) surface groups were investigated for their ability to deliver a model protein-bovine serum albumin conjugated to fluorescein isothiocyanate (BSA-FITC) across biological barriers in vitro and in vivo. BSA-FITC-loaded vesicles were internalized into cells in culture, including brain endothelial b.End3 cells, at 37 °C, but not at 4 °C, indicating an active uptake process. To examine if BSA-FITC-loaded vesicles were stable enough for in vivo delivery, we tested vesicle stability in whole serum. The half-life of cationic BSA-FITC-loaded vesicles with ACh surface groups that are hydrolyzed by choline esterase (ChE) was about 2 h, whereas the half-life of vesicles with similar surface groups, but which are not hydrolyzed by choline esterase (ChE), was over 5 h. Pyridostigmine, a choline esterase inhibitor that does not penetrate the blood-brain barrier (BBB), increased the stability of the ChE-sensitive vesicles to 6 h but did not affect the stability of vesicles with ACh surface groups that are not hydrolyzed by ChE. Following intravenous administration to pyridostigmine-pretreated mice, BSA-FITC encapsulated in ChE-sensitive vesicles was distributed into various tissues with marked accumulation in the brain, whereas non-encapsulated (free) BSA-FITC was detected only in peripheral tissues, but not in the brain. These results show that cationic bolaamphiphilic vesicles with ACh head groups are capable of delivering proteins across biological barriers, such as the cell membrane and the blood-brain barrier (BBB). Brain ChE activity destabilizes the vesicles and releases the encapsulated protein, enabling its accumulation in the brain.

In Silico, In Vitro, and In Vivo Studies Indicate the Potential Use of Bolaamphiphiles for Therapeutic siRNAs Delivery

Specific small interfering RNAs (siRNAs) designed to silence different oncogenic pathways can be used for cancer therapy. However, non-modified naked siRNAs have short half-lives in blood serum and encounter difficulties in crossing biological membranes due to their negative charge. These obstacles can be overcome by using siRNAs complexed with bolaamphiphiles, consisting of two positively charged head groups that flank an internal hydrophobic chain. Bolaamphiphiles have relatively low toxicities, long persistence in the blood stream, and most importantly, in aqueous conditions can form poly-cationic micelles thus, becoming amenable to association with siRNAs. Herein, two different bolaamphiphiles with acetylcholine head groups attached to an alkyl chain in two distinct configurations are compared for their abilities to complex with siRNAs and deliver them into cells inducing gene silencing. Our explicit solvent molecular dynamics (MD) simulations showed that bolaamphiphiles associate with siRNAs due to electrostatic, hydrogen bonding, and hydrophobic interactions. These in silico studies are supported by various in vitro and in cell culture experimental techniques as well as by some in vivo studies. Results demonstrate that depending on the application, the extent of siRNA chemical protection, delivery efficiency, and further intracellular release can be varied by simply changing the type of bolaamphiphile used.

Pentacyclic triterpenoids from Embelia schimperi.

Five oleanane-type pentacyclic triterpenoids were isolated by chromatographic separation of a chloroform extract of the stem bark of Embelia schimperi. Three of these compounds have a methyleneoxy bridge. Two compounds, embelinone and schimperinone, are reported here for the first time from a natural source (they have been synthesized previously during chemical transformations). Their structures were determined by spectroscopic techniques, among which 2-D NMR was useful for complete characterization. Three of the triterpenoids exhibited mild antibacterial properties against the gram-positive bacterial strain Rhodococcus sp.

Delivery of analgesic peptides to the brain by nano-sized bolaamphiphilic vesicles made of monolayer membranes

Inefficient drug delivery to the brain is a major obstacle for pharmacological management of brain diseases. We investigated the ability of bolavesicles - monolayer membrane vesicles self-assembled from synthetic bolaamphiphiles that contain two hydrophilic head groups at each end of a hydrophobic alkyl chain - to permeate the blood-brain barrier and to deliver the encapsulated materials into the brain. Cationic vesicles with encapsulated kyotorphin and leu-enkephalin (analgesic peptides) were prepared from the bolalipids GLH-19 and GLH-20 and studied for their analgesic effects in vivo in experimental mice. The objectives were to determine: (a) whether bolavesicles can efficiently encapsulate analgesic peptides, (b) whether bolavesicles can deliver these peptides to the brain in quantities sufficient for substantial analgesic effect, and to identify the bolavesicle formulation/s that provides the highest analgetic efficiency. The results indicate that the investigated bolavesicles can deliver analgesic peptides across the blood-brain barrier and release them in the brain in quantities sufficient to elicit efficient and prolonged analgesic activity. The analgesic effect is enhanced by using bolavesicles made from a mixture the bolas GLH-19 (that contains non-hydrolyzable acetylcholine head group) and GLH-20 (that contains hydrolysable acetylcholine head group) and by incorporating chitosan pendants into the formulation. The release of the encapsulated materials (the analgesic peptides kyotorphin and leu-enkephalin) appears to be dependent on the choline esterase (ChE) activity in the brain vs. other organs and tissues. Pretreatment of experimental animals with pyridostigmine (the BBB-impermeable ChE inhibitor) enhances the analgesic effects of the studied formulations. The developed formulations and the approach for their controlled decapsulation can serve as a useful modality for brain delivery of therapeutically-active compounds.

Site-directed decapsulation of bolaamphiphilic vesicles with enzymatic cleavable surface groups

Stable nano-sized vesicles with a monolayer encapsulating membrane were prepared from novel bolaamphiphiles with choline ester head groups. The head groups were covalently bound to the alkyl chain of the bolaamphiphiles either via the nitrogen atom of the choline moiety, or via the choline esters methyl group. Both types of bolaamphiphiles competed with acetylthiocholine for binding to acetylcholine esterase (AChE), yet, only the choline ester head groups bound to the alkyl chain via the nitrogen atom of the choline moiety were hydrolyzed by the enzyme. Likewise, only vesicles composed of bolaamphiphiles with head groups that were hydrolyzed by AChE released their encapsulated material upon exposure to the enzyme. Injection of carboxyfluorescein (CF)-loaded vesicles with cleavable choline ester head groups into mice resulted in the accumulation of CF in tissues that express high AChE activity, including the brain. By comparison, when vesicles with choline ester head groups that are not hydrolyzed by AChE were injected into mice, there was no accumulation of CF in tissues that highly express the enzyme. These results imply that bolaamphiphilic vesicles with surface groups that are substrates to enzymes which are highly expressed in target organs may potentially be used as a drug delivery system with controlled site-directed drug release.

Reaction of benzoquinones and naphthoquinones with 1,8-diamino-3,6-dioxanonane and with 1,11-diamino-3,6,9-trioxaundecane

Reaction of 1,4-naphthoquinone or 2,3-dichloro-1,4-naphthoquinone with α,ω-diamino-derivatives of poly(alkylenoxides) leads to the formation of α,ω-bis(quinonyl) amines. A similar reaction with chloranil, bromanil, dichlorodicyanobenzoquinone, S-phenylbenzoquinone and 1,4-benzoquinone itself, leads to the formation of quinoid crown ethers.

Catalytic activity of PEG-quat phase-transfer catalysts in dehydrohalogenation reactions

Abstract New polyethylene glycol ammonium and phosphonium salts (PEG-quat) phase-transfer catalysts were synthesized and their catalytic activity was studied in a dehydrohalogenation liquid-liquid phase-transfer system. The catalytic activity of the PEG-quat catalyst depended on the nature of the quaternary salt, the most effective compounds being those in which only one hydroxyl group is replaced by the quaternary function.

Soluble polymer-bound phase-transfer catalysts

Abstract New soluble polymer-bound phase-transfer catalysts (PTCs) were synthesized using commercially available oxidized polyethylene as the substrate polymer. These new polymeric compounds are bifunctional catalysts containing I ether and quaternary ammonium groups attached to a polyethylene skeleton. They were prepared by direct amidation of oxidized polyethylene with diamino Jeffamines — diamino derivatives of poly(alkene) glycols — followed by a quaternization reaction. Their catalytic activity was studied in the nucleophilic substitution reaction of bromine atoms in 1,6-dibromohexane by cyanide and iodide anions. The activity of the PTCs was dependent on the nature of the starting reagents (oxidized polyethylene and polyglycol diamine), the procedure by which catalysts were synthesized, and the conditions of the substitution reaction. The temperature-dependent solubility of the PTC facilitates their use as homogeneous catalysts, since they can be separated out by filtration at the end of the reaction. The new catalysts can then easily be separate from the products and recovered without loss of activity.

Oxidative stability of jojoba wax

The rates of autoxidation of crude, bleached and stripped jojoba wax were determined under conditions of accelerated oxidation (98 C). Oxidation of the raw yellow wax had a long induction period (50 hr) compared with the bleached wax (10–12 hr) or stripped wax (2 hr). These differences indicate the presence of a natural antioxidant in the crude wax. Addition of 0.02% butylated hydroxytoluene or butylated hydroxyanisole to the bleached wax restored and even improved its stability. Autoxidation of jojoba wax was also studied at room temperature. In the presence of light and air, the activity of the natural inhibitor was rapidly lost.