Keith Fisher

Free radical functionalization of surfaces to prevent adverse responses to biomedical devices

Immobilizing a protein, that is fully compatible with the patient, on the surface of a biomedical device should make it possible to avoid adverse responses such as inflammation, rejection, or excessive fibrosis. A surface that strongly binds and does not denature the compatible protein is required. Hydrophilic surfaces do not induce denaturation of immobilized protein but exhibit a low binding affinity for protein. Here, we describe an energetic ion-assisted plasma process that can make any surface hydrophilic and at the same time enable it to covalently immobilize functional biological molecules. We show that the modification creates free radicals that migrate to the surface from a reservoir beneath. When they reach the surface, the radicals form covalent bonds with biomolecules. The kinetics and number densities of protein molecules in solution and free radicals in the reservoir control the time required to form a full protein monolayer that is covalently bound. The shelf life of the covalent binding capability is governed by the initial density of free radicals and the depth of the reservoir. We show that the high reactivity of the radicals renders the binding universal across all biological macromolecules. Because the free radical reservoir can be created on any solid material, this approach can be used in medical applications ranging from cardiovascular stents to heart-lung machines.

Synthesis, characterisation, activities, cell uptake and DNA binding of a trinuclear complex: [{trans-PtCl(NH3)}2μ-{trans-Pd(NH3)(2-hydroxypyridine)-(H2N(CH2)6NH2)2]Cl4

The trinuclear complex: [[trans-PtCl(NH3)](2)mu-[trans-Pd(NH(3))(2-hydroxypyridine)-(H(2)N(CH(2))(6)NH(2))(2)]Cl(4) (code named CH25) has been synthesized and characterized. The activity of the compound against human ovarian cancer cell lines: A2780, A2780 cisR and A2780 ZD0473R, cell up take, level of binding with DNA and nature of its interaction with pBR322 plasmid DNA have been determined. The compound is found to exhibit significant anticancer activity against the cell lines-about 45 times as active as cisplatin against A2780 cell line, about 76 times as active as cisplatin against A2780(cisR) cell line and about seven times as active as cisplatin against A2780cell line. The higher activity of CH25 suggests that the compound is able to overcome multiple mechanisms of resistance operating in A2780(cisR) and A2780(ZD0473R) cell lines. The compound is believed to form a range of interstrand GG adducts with duplex DNA that induces global changes in the DNA conformation, unlike cisplatin and ZD0473 [also known as AMD473 and JM473: cis-(2-methylpyridine)(ammine)dichloroplatinum(II)] that form mainly intrastrand adducts that induces a local kink in a DNA strand. The increasing prevention of BamH1 digestion of form I and form II pBR322 plasmid DNA with the increase in concentration of the compound is believed to be due to interstrand binding that brings about global changes in DNA conformation.

Predesigned hexanuclear Cu(II) and Cu(II)/Ni(II) metallacycles featuring six-node metallacoronand structural motifs.

The metal-ion-directed assembly of discrete molecular architectures, especially those with interesting supramolecular topologies, has received very considerable attention over recent years. The resulting metallostructures range from simple molecular ellipses, through higher polygons, to large polyhedrons with molecular weights of many thousands. A condition for the rational assembly of such metal–organic structures is that the metal ion(s) and organic component(s) display the steric and electronic complementarity that is required to promote formation of the molecular architecture of interest. In previous studies, we have investigated the synthesis of a range of neutral nanometer-scale metal–organic architectures that employ 1,3and 1,4-aryl-linked bis(b-diketonate) dianions as the organic components. The products include a discrete tetranuclear cofacial dimer of dimers , dinuclear helicates, supramolecular tetranuclear tetrahedral structures, and a range of interesting extended structures, which also incorporate difunctional co-ligands that fall in the category of metal–organic framework materials. 3] It is clear both from our studies, as well as those of other research groups, 5] that bis(b-diketone) derivatives of the above type show uncommon utility as structural elements for the construction of interesting discrete and extended metal–organic architectures. We report herein the results of a further investigation in which the assembly of new hexanuclear species of unprecedented structure has been achieved by the interaction of Cu alone or a combination of Ni and Cu with the 1,4-aryllinked bis(b,d-triketone) LH4. The latter is the first example of a 1,4-aryl-linked bis(b,d-triketone) ligand reported to date. While LH4 may be considered a bis(b,d-triketone) analogue of the corresponding 1,4-aryl-linked bis(b-diketone) species employed in our previous studies, it incorporates the capacity for coordination to two additional metal ions over the bis(bdiketone) species (that is, four ions in all), the pairs of which will be in proximity. Several factors influenced our choice of LH4 for use in this study. Although without direct precedence, individual ligands of this type are readily synthesized using chemistry that is well established by our research group. A strong affinity of the b,dtriketonate units for metal ions across several areas of the periodic table was anticipated based on the known metal-ion chemistry of the corresponding simple b,d-triketone ligands, as well as of the corresponding 1,3-aryl-linked bis(b,dtriketone) derivatives. Furthermore, the ability of each b,d-triketone unit to lose two protons upon metal complexation provides the opportunity for neutral metal complexes to be generated. As no additional anions additional are required, the equilibria involved in the assembly process are simplified, thus assisting the generation of the targeted molecular geometry. Furthermore, by analogy with the behavior of the above-mentioned 1,4-aryl-linked bis(b-diketonato) analogue towards Cu, and, as expected for the formation of an entropy-favored discrete product, it seemed likely that the coordination vectors of the b,d-triketonato fragments in L would be orientated in an aligned (that is, non-opposed) manner upon complex formation. This orientation, coupled with the restricted flexibility that arises from the fully sp hybridized ligand backbone, was expected to generate a bent geometry for L on metal coordination (Figure 1). As expected, a molecular mechanics calculation also confirmed the existence of an energy minimum for this essentially planar bent ligand configuration. Consideration of the coordination vectors in the above ligand arrangement reveals that if an uncharged discrete metal-containing product is to be generated, then the simplest least-strained neutral assembly will involve the interaction of six divalent metal ions with three L ligands to yield a hexanuclear array in which all donor oxygen atoms and the metal centers occupy the same plane. The resulting structure corresponds to an unprecedented hexanuclear metallacoronand motif (1, Figure 1). The preparation of LH4 was based on the related synthesis of the corresponding 1,3-linked analogue and involved a Claisen condensation between dimethyl terephthalate and 6methyl-2,4-heptane-dione (the synthesis and characterization of LH4, including its X-ray structure showing a transoid arrangement of the b,d-triketone groups, is given in the Supporting Information). [*] Dr. F. Li, Dr. J. K. Clegg, Dr. P. Jensen, Dr. K. Fisher, Prof. L. F. Lindoy School of Chemistry, University of Sydney Sydney, NSW, 2006 (Australia) Fax: (+ 61)2-9351-3329 E-mail: l.lindoy@chem.usyd.edu.au

Studies on the synthesis, characterization, binding with DNA and activities of two cis-planaramineplatinum(II) complexes of the form:cis-PtL(NH3)Cl2 where L = 3-hydroxypyridine and 2,3-diaminopyridine

Background Cis-planaramineplatinum(II) complexes like their trans isomers are often found to be active against cancer cell lines. The present study deals with the synthesis, characterization and determination of activity of new cis-planaramineplatinum(II) complexes. Results Two cis-planaramineplatinum(II) complexes: cis-(3-hydroxypyridine)(ammine)dichloroplatinum(II) (code named AH3) and cis-(2,3-diaminopyridine)(ammine)dichloroplatinum(II) (code named AH7) have been prepared and characterised based on elemental analyses, IR, Raman, mass and 1H NMR spectral measurements. The interactions of the compounds with pBR322 plasmid DNA have been investigated and their activity against ovarian cancer cell lines: A2780, A2780cisR and A2780ZD047Rhave been determined. Like cisplatin, AH3 and AH7 are believed to form mainly monofunctional N7(G) and bifunctional intrastrand N7(G)N7(G) adducts with DNA, causing a local distortion of a DNA strand. As a result, gel mobility of the DNA changes. Both AH3 and AH7 are found to be less active than cisplatin against the three cell lines with AH3 being the more active compound of the two. The higher activity of AH3 is in line with its lower molar conductivity value corresponding to a lower degree of dissociation. Conclusion The differences in activity of AH3, AH7 and cisplatin against the cell lines illustrate structure-activity relationship.

Synthesis and Activity of a Trinuclear Platinum Complex: [{trans‐PtCl(NH3)2}2μ‐{trans‐Pt(3‐hydroxypyridine)2(H2N(CH2)6NH2)2}]Cl4 in Ovarian Cancer Cell Lines

This paper describes the synthesis, characterisation, and cytotoxicity of a novel trinuclear platinum complex code named TH1. In addition to its activity against human ovarian cancer cell lines: A2780, A2780cisR, and A2780ZD0473R, cell uptake, DNA‐binding, and the nature of the compound interaction with pBR322 plasmid DNA have been determined. TH1 is found to be significantly more cytotoxic than cisplatin ‐ two times more active than cisplatin against the parent cell line A2780, thirteen times more active against the cisplatin‐resistant cell line A2780cisR and 11.5 times more active against the cell line A2780ZD0473R. Whereas the resistance factors for cisplatin as applied to the cell lines A2780 and A2780cisR, and A2780 and A2780ZD0473R are 12.9 and 3.0 respectively, the corresponding values for TH1 are 1.98 and 0.5. The results suggest that TH1 has been able to significantly overcome resistance in A2780cisR and A2780ZD0473R cell lines. Whereas cisplatin binds with DNA forming mainly intrastrand GG adduct that causes local bending of a DNA strand, TH1 should bind with DNA forming mainly interstrand GG adducts that would cause more of a global change in DNA conformation. Provided it has favourable toxicity profile, TH1 has the potential to be developed into a highly active anticancer drug with a wider spectrum of activity than cisplatin.

Elevated volatile concentrations in high-nutrient plants: do insect herbivores pay a high price for good food?

1. A tritrophic perspective is fundamental for understanding the drivers of insect–plant interactions. While host plant traits can directly affect insect herbivore performance by either inhibiting or altering the nutritional benefits of consumption, they can also have an indirect effect on herbivores by influencing rates of predation or parasitism.

Studies on the synthesis and activity of three tripalladium complexes containing planaramine ligands

The present study deals with the synthesis, characterization and activity against human cancer cell lines: A2780, A2780cisR and A2780ZD0473R of three tripalladium complexes, MH3, MH4 and MH5, that each have two planaramine ligands bound to the central metal ion. Cellular uptake levels, extent of DNA binding, and nature of interaction with salmon sperm and pBR322 plasmid DNA were determined for each complex. Palladium compounds are much more reactive than their corresponding platinum derivatives, which makes them therapeutically inactive but toxic. However, the results of the present study suggest that significant antitumour activity can be introduced in palladium complexes by lessening their reactivity by the introduction of sterically hindered ligands such as 2‐hydroxypyridine, 3‐hydroxypyridine and 4‐hydroxypyridine. When bound to the central palladium ion, 4‐hydroxypyridine appears to be more activating than 2‐hydroxypyridine and 3‐hydroxypyridine, suggesting that noncovalent interactions, such as hydrogen bonding, may also be key determinants of antitumour activity in addition to the steric effect. While cisplatin binds with DNA to form intrastrand GG adducts that causes local bending of a DNA strand, these planaramine‐derived palladium complexes are expected to bind with DNA and form a number of long‐range interstrand GG adducts that would cause a global change in DNA conformation, provided the tripalladium cations in MH3, MH4 and MH5 persist under physiological conditions.

Synthesis, Activity and Binding with DNA of [{trans-PtCl(NH ) }2μ-{trans- Pd(4-hydroxypyridine) (H N(CH ) NH ) ]Cl (TH8)

This paper describes the synthesis, characterization, cytotoxicity of a new trinuclear Pt-Pd-Pt complex code named TH8 containing two 4-hydroxypyridine ligands bound to the central metal ion. In addition to its activity against human ovarian cancer cell lines: A2780, A2780(cisR) and A2780(ZD0473R), cell uptake, level of DNA-binding and nature of interaction of the compound with pBR322 plasmid DNA have also been determined. TH8 is found to be less active than cisplatin against the parent cell line A2780 but is more active against the cisplatin-resistant cell line A2780(cisR). Whereas the resistance factors for cisplatin as applied to the cell lines A2780 and A2780(cisR), and A2780 and A2780(ZD0473R) are 12.9 and 3.0 respectively, the corresponding values for TH8 are 1.4 and 2.1. The results suggest that TH8 has been better able to overcome the resistance operating in A2780(cisR) cell line. Whereas cisplatin binds with DNA forming mainly intrastrand GG adduct that causes local bending of a DNA strand, TH8 is expected to bind with DNA forming mainly interstrand GG adducts that would cause more of a global change in DNA conformation.

An integrated solution for rapid biosensing with robust linker free covalent bindingsurfaces

A novel integrated biosensor methodology is proposed and demonstrated. The methodology utilizes a nitrogen-containing plasma polymer to achieve linker-free binding of a layer of biorecognition molecules. The sensor surface has been shown to maintain its performance after freeze-drying providing a long shelf life under ambient conditions. The sensor is configured for single wavelength ellipsometric detection providing a low cost, versatile, and rapid sensing and diagnosis platform suitable for a wide range of applications and end-users. The merits of the methodology are demonstrated using three antigen-antibody pairs.

Studies on Two New Mixed Ligand Platinum Compounds with a Trans- Geometry

In this paper we report the synthesis and in vitro activity of two new mixed ligand platinum complexes: trans-[PtCl₂(thiazole)(imidazole) [JH3] and trans-[PtCl₂(thiazole)(3-hydroxypyridine) [JH4]. Although the compounds are less active than cisplatin against the parent ovarian cancer cell line A2780, they are more active than cisplatin against the resistant cell lines A2780(cisR) and A2780(ZD0473R), thus indicating that JH3 and JH4 have been better able to overcome mechanisms of resistance operating in A2780(cisR) and A2780(ZD0473R). When Pt-DNA binding levels at 24 h in A2780, A2780(cisR) and A2780(ZD0473R) cell lines are compared it is found that whereas for cisplatin the values in resistant cell lines are significantly lower than that in the parent cell line, for JH3 and JH4 Pt-DNA binding levels in the parent and resistant cell lines are comparable, thus providing an explanation for variations in activity of the compounds in the three cell lines.