A new spacer group derived from arylmalonaldehydes for glucuronylated prodrugs

A new glucuronylated prodrug of doxorubicin, potentially useful for ADEPT or PMT cancer chemotherapy, has been prepared from 4-methyl phenyl malonaldehyde. The enol ether spacer, linked via a carbamate to the 3'-amino group of doxorubicin is rapidly cleaved after beta-glucuronidase (E coli) catalyzed hydrolysis at pH 7.2 and 37 degrees C.     

Wear‐Resistant Nanoscale Silicon Carbide Tips for Scanning Probe Applications

The search for hard materials to extend the working life of sharp tools is an age‐old problem. In recent history, sharp tools must also often withstand high temperatures and harsh chemical environments. Nanotechnology extends this quest to tools such as scanning probe tips that must be sharp on the nanoscale, but still very physically robust. Unfortunately, this combination is inherently contradictory, as mechanically strong, chemically inert materials tend to be difficult to fabricate with nanoscale fidelity. Here a novel process is described, whereby the surfaces of pre‐existing, nanoscale Si tips are exposed to carbon ions and then annealed, to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance that is orders of magnitude greater than that of conventional silicon tips and at least 100‐fold higher than that of monolithic, SiO‐doped diamond‐like‐carbon (DLC) tips. The wear is well‐described by an atom‐by‐atom wear model, from which kinetic parameters are extracted that enable the prediction of the long‐time scale reliability of the tips.     

Diameter-dependent electromechanical properties of GaN nanowires

The diameter-dependent Young's modulus, E, and quality factor, Q, of GaN nanowires were measured using electromechanical resonance analysis in a transmission electron microscope. E is close to the theoretical bulk value ( approximately 300 GPa) for a large diameter nanowire (d=84 nm) but is significantly smaller for smaller diameters. At room temperature, Q is as high as 2,800 for d=84 nm, significantly greater than what is obtained from micromachined Si resonators of comparable surface-to-volume ratio. This implies significant advantages of smooth-surfaced GaN nanowire resonators for nanoelectromechanical system (NEMS) applications. Two closely spaced resonances are observed and attributed to the low-symmetry triangular cross section of the nanowires.     

Preventing Nanoscale Wear of Atomic Force Microscopy Tips Through the Use of Monolithic Ultrananocrystalline Diamond Probes

Nanoscale wear is a key limitation of conventional atomic force microscopy (AFM) probes that results in decreased resolution, accuracy, and reproducibility in probe‐based imaging, writing, measurement, and nanomanufacturing applications. Diamond is potentially an ideal probe material due to its unrivaled hardness and stiffness, its low friction and wear, and its chemical inertness. However, the manufacture of monolithic diamond probes with consistently shaped small‐radius tips has not been previously achieved. The first wafer‐level fabrication of monolithic ultrananocrystalline diamond (UNCD) probes with <5‐nm grain sizes and smooth tips with radii of 30–40 nm is reported, which are obtained through a combination of microfabrication and hot‐filament chemical vapor deposition. Their nanoscale wear resistance under contact‐mode scanning conditions is compared with that of conventional silicon nitride (SiN_x) probes of similar geometry at two different relative humidity levels (≈15 and ≈70%). While SiN_x probes exhibit significant wear that further increases with humidity, UNCD probes show little measurable wear. The only significant degradation of the UNCD probes observed in one case is associated with removal of the initial seed layer of the UNCD film. The results show the potential of a new material for AFM probes and demonstrate a systematic approach to studying wear at the nanoscale.     

Bioorthogonal Reactions in Animals

The advent of bioorthogonal chemistry has led to the development of powerful chemical tools that enable increasingly ambitious applications. In particular, these tools have made it possible to achieve what is considered to be the holy grail of many researchers involved in chemical biology: to perform unnatural chemical reactions within living organisms. In this minireview, we present an update of bioorthogonal reactions that have been carried out in animals for various applications. We outline the advances made in the understanding of fundamental biological processes, and the development of innovative imaging and therapeutic strategies using bioorthogonal chemistry.     

Electromechanical properties of individual single-walled carbon nanotubes grown on focused-ion-beam patterned substrates

The combined capabilities of focused-ion-beam (FIB) nano-patterning and transmission electron microscope characterization have been employed to measure the electromechanical resonance of individual single-walled carbon nanotubes (SWNTs). Suspended and isolated SWNTs of length up to 7 μm were grown on FIB-patterned molybdenum substrates. The Young's modulus of a 5 nm diameter SWNT is found to be E=1.34±0.06 TPa, which is deduced from the measured resonance frequency based on the elastic beam theory. The patterned substrates help locate the nanostructure effectively, allowing the same structure to be inspected after multiple processing steps.     

Oxidative decarboxylation of diclofenac by manganese oxide bed filter

Diclofenac (DCF) was eliminated by fast chemical oxidation on natural manganese oxide in a column reactor. Identification of transformation by-products of DCF by HPLC-UV-MSⁿ gave evidence of decarboxylation, iminoquinone formation and dimerization. The fast oxidation of DCF is also accompanied by a strong adsorption of organic carbon that was explained by the sorption of dimer products on the surface of manganese oxide. Decarboxylation and dimerization increased the hydrophobic interactions with manganese oxide and reduced the presence of potentially toxic by-products in the effluent. The rate of oxidation was first order with respect to DCF and was slowed down by the presence of organic buffer MOPS (3-morpholinopropane-1-sulfonic acid). The first order rate constant in absence of MOPS was extrapolated by considering a surface site-binding model and MOPS as a co-adsorbate. The rate constant was 0.818 min⁻¹ at pH 7 and 10 mM NaCl corresponding to empty bed residence time of 50 s only for 50% removal of DCF. Rate constants increased when pH decreased from pH 8.0 to 6.5 and when ionic strength increased. Manganese oxide bed filter can be considered as an alternative treatment for polishing waste water effluent or for remediation of contaminated groundwater.