Amphiphile desymmetrisation-induced steric relief governs self-assembly pathways in aqueous media

Self-Assembly of Antisense DNA-Camptothecin Amphiphile into Glutathione-Responsive Nanoparticles for Combination Cancer Therapy

Recent years have witnessed the rapid growth of combination therapy for the treatment of cancer. Chemo and antisense DNA therapies are two clinically proven and efficient treatment modalities for cancer. However, direct delivery of both chemo and antisense oligonucleotides into the cancerous cells is challenging and hence there is a high demand for the development of new strategies that permit the direct delivery of chemo and antisense therapeutic agents in a targeted fashion. Herein, we show a supramolecular approach for the direct delivery of hydrophobic chemo drug and cell impermeable antisense oligonucleotide into a cancer cell in a targeted fashion. Synthesis of an amphiphile (DNA1-CPT) consist of hydrophobic camptothecin (CPT) conjugated to an antisense oligonucleotide (DNA1) via glutathione-responsive disulphide linker is reported. Self-assembly of DNA1-CPT results in the formation of GSH-responsive NPs with CPT as the hydrophobic core and DNA1 as the hydrophilic shell. Self-assembled NPs exhibits excellent cellular internalization via endocytosis pathway, and the high concentration of glutathione inside the cancer cells causes the cleavage of disulphide bond of the NPs and trigger the simultaneous release of CPT and DNA1a. Enhanced cytotoxicity is observed for the NPs due to the synergetic combination of chemo and antisense DNA therapies.

Coaxial Helices in Chiral Supramolecular Aggregates from Highly Hindered Chiral Allenes

Chiral allenes self-assembly following a cooperative mechanism into a supramolecular chiral aggregate consisting of two coaxial helices: the internal helix described by the allene stack and the external helix which consist in a 4-helix described by the four allene substituents. More precisely, this supramolecular aggregate possesses six axially chiral elements within its structure-the allene, the allene stack (internal helix) and the stacks of the four allene substituents (external 4-helix)-. Interestingly, slight variations in the magnitude of the tilting degree while keeping its P- or M- orientation (internal helix) can vary the orientation of the 4-axial motifs at the external helix. Thus, while (P)-1 produces a supramolecular helix with a Θ ca. 15° (Pint) and a M1/P2/M1'/P2' orientation of the four axial motifs at the periphery, (P)-2 produces a supramolecular helix with a Θ ca. 23° (Pint) and a P1/P2/P1'/P2' orientation of the four axial motifs at the external helix. As a result, the ECD spectra and the AFM images of the (P)-1 and (P)-2 supramolecular aggregates dominated by the 1 and 1' substituents of the chiral allene indicate opposite handedness although the chirality of the building block and the orientation of the allene stack are the same.

Interfacing Flexible Design and Social Self-Sorting Enables Comprehensive Control over Photophysical and Self-Assembly Properties of Supramolecular Polymers

Supramolecular self-assembly offers an intriguing approach to construct microarchitectures, which combine properties of their molecular constituents with dynamic supramolecular features. Control over intermolecular interactions and their resulting properties can sometimes be achieved by targeted design. However, it is often unfeasible to transfer the insights gained from a specific supramolecular synthon to another chromophore without tedious synthetic work guided by trial and error. Herein we demonstrate how a flexible molecular design approach enables access to a diverse library of photophysical properties, which can be further diversified by social self-sorting strategies using a second supramolecular building block as a modulator. By intercalation into the supramolecular polymer the modulator can disrupt interchromophore interactions and modulate the ensembles emissive properties across the visible color space by simply adjusting the ratio between the two building blocks. Furthermore, by combining a chromophore appended synthon with a different morphology than the modulator the mesoscopic size distribution of the coassemblies can be modified to resemble either of its constituents. Crucially, this moldability is not only achievable for systems under thermodynamic control, but can be also employed to tune photophysical properties and thermal stability profiles of kinetically controlled states. Finally, the thermodynamic stability of the modulated polymers can be adjusted by varying the amount of solubilizing alkyl chains in the ensemble. This peripheral stabilization approach does not affect the engineered photophysical or supramolecular properties. Our results demonstrate how flexible molecular design enriched by a supramolecular modulator can offer access to a wide variety of photophysical properties and enable unique fine-tuning of various supramolecular properties.

Optimal Method to Realize Quantitative Detection of 1D and 2D Nanoassemblies Based on AIE-Active Bolaamphiphilic Molecules

Controllable transformation between the bolaamphiphilic molecule assemblies with different morphological nanostructures represents an exciting new direction for materials. However, there are still significant challenges for the quantitative detection and real-time monitoring of a controllable nanoself-assembly process due to insufficient measuring methods. Herein, we propose a new and effective fluorescence technology for realizing quantitative detection of a controllable conversion process of one-dimensional (1D)/two-dimensional (2D) nanoassemblies by introducing AIEgens as the fluorescence signal part. First, an aggregation-induced emission (AIE)-active bolaamphiphilic molecule (TPE-C8-Br) was designed and synthesized by incorporating tetraphenylethene (TPE) as the chromophore into the cationic amphiphile. Subsequently, the 1D nanofibrous morphology of TPE-C8-Br was successfully converted into the 2D rectangular and circular sheet of tosylate (TPE-C8-Ts) and sodium 1-hexanesulfonate (TPE-C8-HS) with the same molecular skeleton by the simple counterion change, respectively. Interestingly, all 2D nanoassemblies exhibited a stronger fluorescence sensitization effect than that of the 1D nanoassembly at the concentration above the critical micelle concentration (CMC) due to the higher degree of aggregation; thus, the rotation of the AIE-active TPE moiety is more restricted in TPE-C8-Ts and TPE-C8-HS. More meaningfully, a rather good linear correlation (FI = 3174.86 + 5282.29MP, R2 = 0.999) and a quadratic correlation (FI = 2113.71 + 5163.56MP - 2966.07MP2) were obtained between the molar percentage (MP) of the 2D nanoassembly and the fluorescence intensity (FI). The two proposed methods respond very well with regard to dependability, which can be used for the quantitative calculation of the molar ratio of 1D and 2D components in the controllable nanoself-assembly process. Therefore, this work offers an efficient and practical method for realizing the dynamic monitoring and quantitative detection of mutual conversion between different nanoassemblies.

Pyrrole βC-B-N Fused Porphyrins: Molecular Structures and Opto-Electrochemical Studies

Herein, we report the design, synthesis, structure, and electrochemical study of doubly βC-B-N fused Ni(II) porphyrins (1-trans, 1-cis, 2-trans, and 2-cis). These compounds have been synthesized from A2B2 type dipyridyl Ni(II) porphyrins (Ar=Ph for 1 a; Ar=C6F5 for 2 a) via Lewis base-directed electrophilic aromatic borylation reactions. The solution state structures of these compounds have been established using 1H NMR, 11B NMR, 1H-1H COSY, 1H-13C HSQC, and 19F-13C HSQC NMR techniques. Single crystal X-ray analysis have revealed that 1-trans, 1-cis, and 2-trans adopt ruffled conformations, with alternate meso-carbons on the opposite sides of the mean porphyrin plane. The Soret bands in the absorption spectra of the B-N fused molecules are ~40 nm redshifted compared to unfused Ni(II) porphyrin precursors. The B-N fusion have diminished the redox potential of fused porphyrins. Although 1-trans and 1-cis, show four oxidation processes, 2-trans and 2-cis show only three oxidation processes. DFT studies have revealed that the tetrahedral geometry of the boron has induced a twist in the π-conjugation, which destabilizes the HOMO and stabilizes the LUMO in 1-trans, 1-cis, 2-trans, and 2-cis.