Marina Shamis

Targeting Antibacterial Agents by Using Drug-Carrying Filamentous Bacteriophages

ABSTRACT Bacteriophages have been used for more than a century for (unconventional) therapy of bacterial infections, for half a century as tools in genetic research, for 2 decades as tools for discovery of specific target-binding proteins, and for nearly a decade as tools for vaccination or as gene delivery vehicles. Here we present a novel application of filamentous bacteriophages (phages) as targeted drug carriers for the eradication of (pathogenic) bacteria. The phages are genetically modified to display a targeting moiety on their surface and are used to deliver a large payload of a cytotoxic drug to the target bacteria. The drug is linked to the phages by means of chemical conjugation through a labile linker subject to controlled release. In the conjugated state, the drug is in fact a prodrug devoid of cytotoxic activity and is activated following its dissociation from the phage at the target site in a temporally and spatially controlled manner. Our model target was Staphylococcus aureus, and the model drug was the antibiotic chloramphenicol. We demonstrated the potential of using filamentous phages as universal drug carriers for targetable cells involved in disease. Our approach replaces the selectivity of the drug itself with target selectivity borne by the targeting moiety, which may allow the reintroduction of nonspecific drugs that have thus far been excluded from antibacterial use (because of toxicity or low selectivity). Reintroduction of such drugs into the arsenal of useful tools may help to combat emerging bacterial antibiotic resistance.

Titanium(IV) complexes of trianionic amine triphenolate ligands

Abstract Two trianionic amine triphenolate ligands are introduced and their isopropoxide Ti(IV) complexes synthesized. The two complexes are mononuclear and C3-symmetrical on the NMR timescale. High barriers to inversion ( ΔG ‡ >65 KJ mol −1 ) between the enantiomers of each complex were found. The complex derived from the bulkier tripodal ligand shows a better resistance to hydrolysis.

Tantalum(v) complexes of an amine triphenolate ligand: a dramatic difference in reactivity between the two labile positionsElectronic supplementary information (ESI) available: synthetic and spectroscopic data for all complexes. See http://www.rsc.org/suppdata/dt/b2/b206759e/

A tetradentate trianionic amine triphenolate ligand leads to octahedral Ta(V) complexes of Cs-symmetry, in which the two labile positions that are in cis geometry exhibit a dramatic difference in reactivity, the position trans to a phenoxy group being the active one.

Neuroblastoma directed therapy by a rational prodrug design of etoposide as a substrate for tyrosine hydroxylase.

Tumor directed cytotoxic therapy is one of the major challenges for the success of chemotherapy. In order to accomplish this goal in neuroblastoma, we rationally designed a prodrug of etoposide as substrate for tyrosine hydroxylase, a well established neuroblastoma associated enzyme. Here, we report synthesis and characterization of a 3,4 dihydroxy-phenyl carbamate derivative of etoposide. In order to demonstrate activation by tyrosine hydroxylase, the coding sequence of murine tyrosine hydroxylase was generated by reverse transcriptase-polymerase chain reaction from NXS2 neuroblastoma cells and cloned into the pRSET-A bacterial expression vector. The enzyme was expressed in Escherichia coli, characterized by Western blot and enzymatic activity was demonstrated by conversion of tyrosine into DOPA in the presence of cofactors using reversed phase high-performance liquid chromatography. Under these enzymatic conditions, we demonstrate conversion of 3,4 dihydroxy-phenyl carbamate prodrug into free etoposide. This effect was clearly mediated by the enzyme since bacteria transformed with the empty vector were ineffective of prodrug activation. Furthermore, tyrosine hydroxylase positive cells exposed to the etoposide prodrug were effectively killed in contrast to tyrosine hydroxylase negative controls. These findings demonstrate that etoposide can be designed as a prodrug substrate for tyrosine hydroxylase and thereby establish proof of concept for neuroblastoma directed enzyme prodrug therapy.