No abstract

The targeting of drugs specifically to their sites of action is an important strategy for increasing drug efficacy. Chemists have come up with many elegant schemes that aim to convert drugs into magic bullets. This review focuses on the chemistry that underlies these schemes, with particular emphasis on two types of cleavable covalent bonds that are frequently used to link drugs to their various carriers: disulfide bonds and hydrazone bonds. These linkages have been used to release drugs under specific conditions; in the case of disulfides, cleavage is triggered by the mildly reducing environment found in intracellular fluids, and in the case of hydrazones, the acidic conditions that prevail in endosomes cause release of the drug. The applications of these chemistries in drug delivery are reviewed.

A combined single-source precursor approach has been developed for the deposition of thin films of Cr-doped molybdenum disulfide (MoS2) by aerosol-assisted chemical vapor deposition (AACVD). Tris­(diethyldithiocarbamato)­chromium­(III) can also be used for the deposition of chromium sulfide (CrS). Films have been analyzed by a range of techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and powder X-ray diffraction (pXRD) to elucidate film morphology, composition, and crystallinity. The presence of Cr in the MoS2 films produces a number of striking morphological, crystallographic, and nanomechanical changes to the deposited films. The chromium dopant appears to be uniform throughout the MoS2 from the scanning transmission electron microscopy (STEM) EDX spectrum imaging of nanosheets produced by liquid-phase exfoliation of the thin films in N-methyl-2-pyrollidone.

[structure: see text] Dynamic combinatorial libraries (DCLs) containing water-soluble disulfide-linked cages (alongside macrocyclic structures) have been generated and characterized. Unlike most other strategies for generating molecular cages, the structures are held together by covalent bonds, which are formed under thermodynamic control. The diversity of the cages generated opens new possibilities for a generalized combinatorial strategy toward molecular encapsulation.

A simple water-soluble naphthalenedithiol building block is converted quantitatively into a series of octameric [2]-catenanes, composed of two interlocked molecular squares. When this mixture is re-equilibrated in the presence of an adamantyl ammonium guest, the catenanes disassemble into their macrocyclic components that bind the guest with nanomolar affinity in water.