A convenient approach for the self-assembly of well-defined porphyrin nanowires in water, wherein the individual monomers do not aggregate via pi-pi interactions, is disclosed. These unidirectional and heteromeric assemblies are instead composed of robust beta-CD/adamantane host/guest interactions. A combination of surface microscopies and fluorescence energy transfer experiments were conducted on the nanowires demonstrating their stability and resistance to disassembly.
The naturally occurring nucleic acid bases (nucleobases) adenine, thymine (uracil), guanine, and cytosine are widely appreciated for their ability to stabilize canonical Watson-Crick base-pairing motifs, as well as a number of other well-characterized arrangements, such as Hoogsteen and wobble heterodimers, and a variety of homodimers. In this tutorial review, the use of these kinds of interactions to form synthetic polymeric and oligomeric ensembles is summarized. Particular emphasis will be placed on synthetic analogues of guanine that stabilize the formation of well-defined higher order aggregates, as well as de novo polymeric systems whose properties are modulated by the presence of nucleobase derivatives incorporated within or attached to the chain-defining backbone. In both cases, nucleobase-nucleobase interactions serve to underlie the chemistry, establish the structural morphology, and enable the development of bioinspired, environmentally responsive materials.
A novel water-soluble nanorod is discussed, which is prepared via the self-assembly of pristine C60 and a double-sided porphyrin projecting four beta-cyclodextrins from each face.
Taxol is one of the potential anticancer drugs; however, the yield of Taxol and its cytotoxicity are common challenges. Thus, manipulating the Taxol biosynthetic pathway from endophytic fungi, in addition to chemical modification with biocompatible polymers, is the challenge. Four fungal isolates, namely, Aspergillus flavipes, A. terreus, A. flavus, and A. parasiticus, were selected from our previous study as potential Taxol producers, and their potency for Taxol production was evaluated in response to fluconazole and silver nitrate. A higher Taxol yield was reported in the cultures of A. flavipes (185 µg/L) and A. terreus (66 µg/L). With addition of fluconazole, the yield of Taxol was increased 1.8 and 1.2-fold for A. flavipes and A. terreus, respectively, confirming the inhibition of sterol biosynthesis and redirecting the geranyl phosphate pool to terpenoids synthesis. A significant inhibition of ergosterol biosynthesis by A. flavipes with addition of fluconazole was observed, correlating with the increase on Taxol yield. To increase the Taxol solubility and to reduce its cytotoxicity, Taxol was modified via chemical conjugation with porphyrin, and the degree of conjugation was checked from the Thin layer chromatography and UV spectral analysis. The antiproliferative activity of native and modified Taxol conjugates was evaluated; upon porphyrin conjugation, the activity of Taxol towards HepG2 was increased 1.5-fold, while its cytotoxicity to VERO cells was reduced 3-fold.
A porphyrin functionalised with pillar[5]arene and a viologen at its 5- and 15-meso positions assembles in a head-to-tail manner, producing linear supramolecular daisy chains in dichloromethane. At high concentrations, it forms an organogel which has been investigated by electron microscopy and rheological measurements, paving the way for the preparation of other functional supramolecular assemblies which harness viologen⊂pillararene host-guest interactions.
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