Controlled release of hydrophilic guest molecules from photoresponsive nucleolipid vesicles

Chiral graphene-based supramolecular hydrogels toward tumor therapy

Drugs with chiral property are playing very important role on precise treatment of diseases (especially antitumor drugs), however, enantioselective delivery of chiral anticancer drugs is still challenge. Herein, a chiral...

Strategies for altering lipid self-assembly to trigger liposome cargo release

While liposomes have proven to be effective drug delivery nanocarriers, their therapeutic attributes could be improved through the development of clinically viable triggered release strategies in which encapsulated drug contents could be selectively released at the sites of diseased cells. As such, a significant amount of research has been reported involving the development of stimuli-responsive liposomes and a broad range of strategies have been explored for driving content release. These have included the introduction of trigger groups at either the lipid headgroup or within the acyl chains that alter lipid self-assembly properties of known lipids as well as the rational design of lipid analogs programed to undergo conformational changes induced by events such as binding interactions. This review article describes advances in the design of stimuli-responsive liposome strategies with an eye towards emerging trends in the field.

Self-assemblies of nucleolipid supramolecular synthons show unique self-sorting and cooperative assembling process

The inherent control of the self-sorting and co-assembling process that has evolved in multi-component biological systems is not easy to emulate in vitro using synthetic supramolecular synthons. Here, using the basic component of nucleic acids and lipids, we describe a simple platform to build hierarchical assemblies of two component systems, which show an interesting self-sorting and co-assembling behavior. The assembling systems are made of a combination of amphiphilic purine and pyrimidine ribonucleoside-fatty acid conjugates (nucleolipids), which were prepared by coupling fatty acid acyl chains of different lengths at the 2'-O- and 3'-O-positions of the ribose sugar. Individually, the purine and pyrimidine nucleolipids adopt a distinct morphology, which either supports or does not support the gelation process. Interestingly, due to the subtle difference in the order of formation and stability of individual assemblies, different mixtures of supramolecular synthons and complementary ribonucleosides exhibit a cooperative and disruptive self-sorting and co-assembling behavior. A systematic morphological analysis combined with single crystal X-ray crystallography, powder X-ray diffraction (PXRD), NMR, CD, rheological and 3D X-ray microtomography studies provided insights into the mechanism of the self-sorting and co-assembling process. Taken together, this approach has enabled the construction of assemblies with unique higher ordered architectures and gels with remarkably enhanced mechanical strength that cannot be derived from the respective single component systems.

Mechanism of the photorelease of alcohols from the 9-phenyl-9-tritylone protecting group

A mechanistic investigation of the 9-phenyl-9-tritylone photoremovable protecting group for alcohols revealed that the anion radical is the key intermediate required for clean deprotection.

Engineering hot-melt extruded solid dispersion for controlled release of hydrophilic drugs

It is often challenging to precisely manipulate the release behavior of hydrophilic drugs that is believed to be crucial for a satisfactory therapeutic outcome. The aim of this work was to regulate the dissolution of hydrophilic drug from hot-melt extruded solid dispersion via rational screening of the pore-forming agents. Venlafaxine hydrochloride and Compritol® 888 ATO was selected as the model drug and carrier excipient, respectively. Hydrophilic polyethylene glycol (PEG 6000) and polyvinylpyrolidone (PVP K30) were chosen as the transient pore-forming agents. The X-ray diffraction and thermal analysis showed that both drug and carrier existed in the crystalline form. Both types of polymers could generate pores upon dissolution test and the drug release rate was proportionally correlated to the pore-forming agent content. The mathematical modelling showed that the Ritger-Peppas model gave the best fit to the release curves, which demonstrates a diffusion-dominant release mechanism. The scanning electron microscopy and mercury intrusion porosimetry analysis proved that PVP K30 could generate large pores with low porosity, but PEG 6000 produced smaller pores with relatively high porosity. The in vivo pharmacokinetics study in rat revealed that solid dispersions containing either PEG 6000 or PVP K30 (both at 2.5%, w/w) exhibited an elevated bioavailability compared to the commercial product, Effexor® XR. The current work implied that rational screening of transient pore-forming polymer in solid dispersion could be a robust approach for controlling hydrophilic drug release.

Light-responsive molecular containers

This review highlights relevant studies of light-controlled molecular containers able to catch and release small molecules.

Near-infrared light-sensitive liposomes for controlled release

A 6-bromo-7-hydroxy-4-hydroxymethylcoumarin containing amphiphilic lipid was synthesized and applied as a near-infrared light triggered controlled release system.

Surface properties of nucleolipids and photo-controlled release of hydrophobic guest molecules from their micellar aggregates

Two series of nucleolipids have been designed and synthesized, one with a varying chain length (the dT-Cn series) and the other incorporating an aromatic photo-responsive moiety at the molecular hydrophobic and hydrophilic interface (the P-dT-Cn series). Surface tension measurements revealed the variations of critical micelle concentrations (CMCs) with the alkyl chain length and the incorporation of the photo-responsive segment. The P-dT-Cn series showed broadly lower CMCs and the minimum area per molecule (Amin) values because the π-π stacking between the additional aromatic rings favours more tight packing in the micelle formation. Both series showed similar surface tensions at the CMCs to conventional surfactants with equivalent molecular structures. Their micellar aggregates were used for encapsulation of hydrophobic Nile Red (NR). For the P-dT-Cn series, the encapsulated NR was released upon light irradiation and the controlled release was readily realized by controlling irradiation intensities or switching on and off irradiation. The integration of biocompatibility, complementary base recognition and photo-responsiveness makes the amphiphilic nucleolipids promising in biomedical and biotechnological applications.

Oxygen and Carbon Dioxide Dual Responsive Nanoaggregates of Fluoro- and Amino-Containing Copolymer

We report herein a novel approach for preparing CO₂- and O₂-responsive polymer nanoaggregates. The polymer, synthesized via atom transfer radical polymerization (ATRP), has one hydrophilic poly(ethylene glycol) (PEG) block, and the other hydrophobic block composed of 88 randomly distributed units of CO₂-responsive N,N-diethylaminoethyl methacrylate (DEA) and 43 units of O₂-responsive 2,2,2-trifluoroethyl methacrylate (FMA). The amphiphilic copolymer self-assembled into vesicular nanoaggregates in water. With O₂ bubbling, the vesicles expanded eight times in volume. With CO₂ bubbling, the vesicular morphology collapsed and transformed into a small spherical micelle. The dual gas-responsivity significantly expanded the scope in designing stimuli-responsive materials and processes.

Glycosyl-Nucleolipids as new bioinspired amphiphiles

Four new Glycosyl-NucleoLipid (GNL) analogs featuring either a single fluorocarbon or double hydrocarbon chains were synthesized in good yields from azido thymidine as starting material. Physicochemical studies (surface tension measurements, differential scanning calorimetry) indicate that hydroxybutanamide-based GNLs feature endothermic phase transition temperatures like the previously reported double chain glycerol-based GNLs. The second generation of GNFs featuring a free nucleobase reported here presents a better surface activity (lower γ_lim) compared to the first generation of GNFs.