The Introduction of π-π Stacking Moieties for Fabricating Stable Micellar Structure: Formation and Dynamics of Disklike Micelles

The effect of π-Conjugation on the self-assembly of micelles and controlled cargo release

Here we presented a novel micelle self-assembled from amphiphiles with π-conjugated moieties (OEG-DPH). The π-conjugated structural integrity of the micelles enabled stable encapsulation of Nile Red (NR, model drug). The self-assembly behaviour of the amphiphiles and the release profile of NR loaded micelles were investigated. Spherical core-shell structured NR loaded micelles with low CMC of 57 μg/mL and the efficient intracellular delivery process was monitored. This research provided a way to fabricate stable polymeric micelles and develop a practical nanocarrier for therapeutics delivery.

Conversion of curved assemblies into two dimensional sheets

The design and preparation of organic two dimensional (O2D) sheets and their conversion to curved nanostructures is in its infancy. To convert a flat structure into a curved structure, the molecule must have multiple interaction possibilities and an in-built twist. The conjugated small molecule iso-Indigo (i-Indigo) comprises two phenyl rings that are twisted (the dihedral angle is 15°) at the junction. The i-Indigo has been connected with moieties that impart hydrogen bonding and van der Waals interactions. Due to the presence of the π cloud in i-Indigo, π-π interactions are also present in the molecule. While all three interactions are in operation, rings and toroids are formed. Upon addition of hydrogen bonding competing solvents, the rings and toroids unravel to form O2D sheets. Control molecules that don't have hydrogen bonding moieties and π-π interactions form random assemblies. Please note that the rings, toroids and O2D sheets are formed in a single solvent by simple dissolution, unlike previous approaches that involve multiple steps and solvents.

Smart Organic Two-Dimensional Materials Based on a Rational Combination of Non-covalent Interactions

Rational design of organic 2D (O2D) materials has made some progress, but it is still in its infancy. A class of self-assembling small molecules is presented that form nano/microscale supramolecular 2D materials in aqueous media. A judicial combination of four different intermolecular interactions forms the basis for the robust formation of these ultrathin assemblies. These assemblies can be programmed to disassemble in response to a specific protein and release its non-covalently bound guest molecules.

Terminal modification of polymeric micelles with π-conjugated moieties for efficient anticancer drug delivery

High drug loading content is the critical factor to polymeric micelles for efficient chemotherapy. Small molecules of cinnamic acid, 7-carboxymethoxy coumarin and chrysin with different π-conjugated moieties were immobilized on the terminal hydroxyl groups of PCL segments in mPEG-PCL micelles to improve drug loading content via the evocation of π-π stacking interaction between doxorubicin (DOX) and polymeric micelles. The modification of π-conjugated moieties enhanced the capability of crystallization of mPEG-PCL block copolymers. The drug loading content increased dramatically from 12.9% to 25.5% after modification. All the three modified mPEG-PCL micelles were nontoxic to cells. Chrysin modified polymeric micelles exhibited the most efficient anticancer activity. The in vivo anticancer activity of 10 mg/kg DOX dose of chrysin modified micelle formulation for twice injections was comparable to that of 5 mg/kg dose of free DOX·HCl for four injections under the circumstance of same total DOX amount. The systemic toxicity of DOX loaded chrysin modified micelles was significantly reduced. This research provided a facile strategy to achieve polymeric micelles with high drug loading content and efficient anticancer activity both in vitro and in vivo.

Complete Regression of Xenograft Tumors upon Targeted Delivery of Paclitaxel via Π-Π Stacking Stabilized Polymeric Micelles

Treatment of cancer patients with taxane-based chemotherapeutics, such as paclitaxel (PTX), is complicated by their narrow therapeutic index. Polymeric micelles are attractive nanocarriers for tumor-targeted delivery of PTX, as they can be tailored to encapsulate large amounts of hydrophobic drugs and achiv prolonged circulation kinetics. As a result, PTX deposition in tumors is increased, while drug exposure to healthy tissues is reduced. However, many PTX-loaded micelle formulations suffer from low stability and fast drug release in the circulation, limiting their suitability for systemic drug targeting. To overcome these limitations, we have developed PTX-loaded micelles which are stable without chemical cross-linking and covalent drug attachment. These micelles are characterized by excellent loading capacity and strong drug retention, attributed to π-π stacking interaction between PTX and the aromatic groups of the polymer chains in the micellar core. The micelles are based on methoxy poly(ethylene glycol)-b-(N-(2-benzoyloxypropyl)methacrylamide) (mPEG-b-p(HPMAm-Bz)) block copolymers, which improved the pharmacokinetics and the biodistribution of PTX, and substantially increased PTX tumor accumulation (by more than 2000%; as compared to Taxol or control micellar formulations). Improved biodistribution and tumor accumulation were confirmed by hybrid μCT-FMT imaging using near-infrared labeled micelles and payload. The PTX-loaded micelles were well tolerated at different doses, while they induced complete tumor regression in two different xenograft models (i.e., A431 and MDA-MB-468). Our findings consequently indicate that π-π stacking-stabilized polymeric micelles are promising carriers to improve the delivery of highly hydrophobic drugs to tumors and to increase their therapeutic index.

Concentration-dependent and light-responsive self-assembly of bolaamphiphiles bearing α-cyanostilbene based photochromophore

In this paper, a new bolaamphiphile bearing 1-cyano-1,2-bis(phenyl)ethene (CNBE) has been synthesized. The self-assembly of this molecule in aqueous solution is concentration-dependent. Two distinct morphologies, monomolecular layered lamellas and helical nanofibres have been obtained with the as-prepared molecular configuration. Note worthily, the helical nanofibres provide an experimental evidence for the pure twisted structure in the liquid crystals, which is theoretically proposed by De Gennes. Due to the photoisomerization of CNBE, the self-assembled nanostructures undergo morphological changes upon irradiation. Although various nanostructures were observed in the solution-state, only nanofibres were obtained after the solution was cast on a substrate, which was attributed to a strong dewetting effect. This work illustrates concentration-dependent and light-responsive self-assembly and provides a novel avenue for fabricating smart soft materials.

Biodegradable stereocomplex micelles based on dextran-block-polylactide as efficient drug deliveries

Biodegradable stereocomplex micelles (SCMs) based on amphiphilic dextran-block-polylactide (Dex-b-PLA) were designed and used for efficient intracellular drug deliveries. The Dex-b-PLA copolymers were successfully synthesized by click reaction. The structures of the resultant copolymers were verified by (1)H NMR and FT-IR spectra. The formation of stable micelles through self-assembly driven by the stereocomplexation between enantiomeric l- and d-PLA blocks was characterized by transmission electron microscopy (TEM), dynamic laser scattering (DLS), and fluorescence techniques. It was interesting to observe that the SCMs showed lower critical micelle concentration values (CMCs) because of the stereocomplex interaction between PLLA and PDLA. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis provided information on the thermal and crystal properties of the copolymers and SCMs. The improved stability of SCMs should be attractive for intracellular drug delivery. Thus, a model anticancer drug doxorubicin (DOX) was loaded into micelles, and the in vitro drug release in was also studied. The release kinetics of DOX showed DOX-loaded SCMs exhibited slower DOX release. Confocal laser scanning microscopy (CLSM) and flow cytometry studies also showed that the DOX-loaded SCMs exhibited a slower drug release behavior. Meanwhile, the MTT assay demonstrated that DOX-loaded SCMs show lower cellular proliferation inhibition against HepG2. In sum, the micelles through self-assembly driven by stereocomplex interaction would have great potential to be used as stable delivery vehicles for pharmaceutical and biomedical applications.