Efficient modulation of a barium metal-organic framework using amino acids.

In recent years, significant advances have been made in the precise control of the physical properties of metal-organic frameworks (MOFs) via the linker-modulated method in which modulators compete with linkers and impose kinetic limitations through crystal growth. In this regard, the structure of a new barium-organic framework [Ba(H2BTC)2(H2O)4]n, BaBTC (BTC = 1,3,5-benzene tricarboxylic acid) is introduced, which allows the competitive coordination strategy and growth orientation of an alkaline-earth metal-organic framework (AEMOF) to be probed without sacrificing phase purity, porosity and crystallinity. The modulator effect of an assortment of amino acids on the particle size and morphology of BaBTC is investigated. Additionally, another new MOF [Ba(BTC)2(H2O)3]n.nH2O, BaBTC-2, is synthesized through a change in the ligand concentration. This work gives a successful example of a modulation method for AEMOF synthesis by amino acids that may contribute towards targeting future avenues of nanomaterial synthesis.

A V(iii)-induced metallogel with solvent stimuli-responsive properties: structural proof-of-concept with MD simulations.

A new solvent stimuli-responsive metallogel (VGel) was synthesized through the introduction of vanadium ions into an adenine (Ade) and 1,3,5-benzene tricarboxylic acid (BTC) organogel, and its supramolecular self-assembly was investigated from a computational viewpoint. A relationship between the synthesized VGel integrity and the self-assembly of its components is demonstrated by a broad range of molecular dynamics (MD) simulations, an aspect that has not yet been explored for such a complex metallogel in particular. MD simulations and Voronoi tessellation assessments, both in agreement with experimental data, confirm the gel formation. Based on excellent water stability and the ethanol/methanol stimuli-responsive feature of the VGel an easy-to-use visualization assay for the detection of counterfeit liquor with a 6% (v/v) methanol limit of detection in 40% (v/v) ethanol is reported. These observations provide a cheap and technically simple method and are a step towards the immersible screening of similar molecules in methanol-spiked beverages.

Crystal engineering of an adenine-decavanadate molecular device towards label-free chemical sensing and biological screening.

Due to the inherent geometrical interdependencies of nucleic acid structures, the ability to engineer biosensors that rely on the specific interactions of these compounds is of considerable importance. Additionally, sensing or screening in a label-free fashion is a capability of these structures that can be readily achieved by exploiting the fluorescent component. In this work, the [AdH]6[V10O28].4(H2O) (1) supramolecular structure is introduced using adenine and decavanadate moieties that allow probing of selectivity to specific nucleic acid binding events by optical changes. The structure of (1) is an alternating organic-inorganic hybrid architecture of cationic adeninium (AdH+) ribbons and anionic decavanadate (DV)-water sheets. The luminescent screening and anticancer activity of compound (1) on the two human mammary carcinoma cell lines MDA-MB-231 and MCF7 were investigated using fluorescent microscopy and MTT assays, respectively. It was found that compound (1) is cell permeable with no toxicity below 12.5 µM concentration and moderate cytotoxicity at concentrations as high as 200 µM in human breast cancer cell lines, making it a useful tool to study the cell nucleus in real time.

Peptide-Fluorophore Hydrogel as a Signal Boosting Approach in Rapid Detection of Cancer DNA.

Cancer is a major health risk in the modern society that requires rapid, reliable, and inexpensive diagnostics. Because of the low abundance of cancer DNA in biofluids, current detection methods require DNA amplification. The amplification can be challenging; it provides only relative quantification and extends time and cost of an assay. Herein, we report a new oligonucleotide hybridization platform for amplification-free detection of human cancer DNA. Using a large PEG-capture probe allows rapid separation of the bound (mutant) versus unbound (wild type) DNA. Next, a supramolecular hydrogel forming peptide attached to a detection oligonucleotide probe serves as a signal amplification tool. Having screened multiple short peptides and fluorophores, we identified the system P1 + cyanine 3.5 that allows for sensitive quantitative detection of mutation L858R in EGFR oncogene. The peptide-fluorophore-based assay provides absolute target DNA quantification at the detection limit of 20 ng cancer DNA versus >500 ng for Cy3.5-labeled oligonucleotide in only 1 hour.

The salt-cocrystal spectrum in salicylic acid-adenine: the influence of crystal structure on proton-transfer balance.

At one extreme of the proton-transfer spectrum in cocrystals, proton transfer is absent, whilst at the opposite extreme, in salts, the proton-transfer process is complete. However, for acid-base pairs with a small ΔpKa (pKa of base - pKa of acid), prediction of the extent of proton transfer is not possible as there is a continuum between the salt and cocrystal ends. In this context, we attempt to illustrate that in these systems, in addition to ΔpKa, the crystalline environment could change the extent of proton transfer. To this end, two compounds of salicylic acid (SaH) and adenine (Ad) have been prepared. Despite the same small ΔpKa value (≈1.2), different ionization states are found. Both crystals, namely adeninium salicylate monohydrate, C5H6N5+·C7H5O3-·H2O, I, and adeninium salicylate-adenine-salicylic acid-water (1/2/1/2), C5H6N5+·C7H5O3-·2C5H5N5·C7H6O3·2H2O, II, have been characterized by single-crystal X-ray diffraction, IR spectroscopy and elemental analysis (C, H and N) techniques. In addition, the intermolecular hydrogen-bonding interactions of compounds I and II have been investigated and quantified in detail on the basis of Hirshfeld surface analysis and fingerprint plots. Throughout the study, we use crystal engineering, which is based on modifications of the intermolecular interactions, thus offering a more comprehensive screening of the salt-cocrystal continuum in comparison with pure pKa analysis.