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Abstract: DNA capture surfaces represent a powerful approach to developing highly sensitive sensors for identifying the cause of infection. Electrochemically deposited polypyrrole, PPy, films have been functionalized with electrodeposited gold nanoparticles to give a nanocomposite material, PPy–AuNP. Thiolated capture strand DNA, that is complementary to the sequence from the pathogen Staphylococcus aureus that causes mammary gland inflammation, was then immobilized onto the gold nanoparticles and any of the underlying gold electrode that is exposed. A probe strand, labelled with horse radish peroxidase, HRP, was then hybridized to the target. The concentration of the target was determined by measuring the current generated by reducing benzoquinone produced by the HRP label. Semi-log plots of the pathogen DNA concentration vs. faradaic current are linear from 150pM to 1μM and pM concentrations can be detected without the need for molecular, e.g., PCR or NASBA, amplification. The nanocomposite also exhibits excellent selectivity and single base mismatches in a 30 mer sequence can be detected. [Copyright &y& Elsevier]

Abstract: Due to its low toxicity and excellent biocompatibility, titanium dioxide and its alloyed are widely used in biomedical applications. Furthermore, TiO2 can be excited by UV light to create charge carriers giving rise to photocatalytic redox reactions at its surface and photo-induced super-hydrophilicity. In this work, TiO2 films were modified with silver (Ag–TiO2) by the photocatalytic reduction of Ag+ from solution. The films and the adsorption of β-amyloid (1–42), were studied using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscopy (AFM). These films were confirmed to contain mainly anatase crystallites and the photo-reduced Ag was predominantly Ag0 (>0%). Ag loading of the TiO2 markedly enhanced the Raman signal (ca. 15-fold), but caused significant changes to the protein spectrum indicating non-specific binding of β-amyloid side chain residues to the silver. The amide modes remained well-resolved and were used to estimate the conformational change induced in the protein by the silver. Raman analysis showed an increase in the intensity of the band at ∼1665cm−1 assigned to the disordered conformation of the β-amyloid, suggesting that the adsorption to the silver sites induces conformational changes. Contaminated surfaces were exposed to UVB irradiation, caused further conformational changes in the β-amyloid, which mildly inhibited amyloid fibril formation, thought to be induced through a photocatalytic mechanism. [Copyright &y& Elsevier]

Abstract: Titanium dioxide is a useful material in the biomedical field as it has excellent biocompatibility based on its non-toxicity and non-inflammatory properties. Furthermore, TiO2 can be excited by UV light to create charge carriers giving rise to photocatalytic redox reactions at the surface and photo-induced super-hydrophilicity. These properties might be exploited for surface decontamination of medical devices and implants. With this in mind, titanium dioxide TiO2 films were prepared on stainless steel substrates using magnetron sputtering. Silver loaded (Ag–TiO2) films were prepared by the photocatalytic reduction of Ag+ from solution. The adsorption of human serum albumin (HSA) was studied. Surface analysis methods used included X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and atomic force microscopy (AFM). The TiO2 films were predominantly anatase crystal phase and the photoreduced Ag was present at greater than 90% of the silver content as Ag0 on the surface. Ag loading of the TiO2 markedly enhanced the Raman signal (ca. 15-fold), but caused significant changes to the spectrum indicating non-specific binding of protein side chain residues to the Ag. The amide I and III modes remained well-resolved and were used to estimate the conformational change induced by the Ag. Raman analysis showed an increase in the intensity of the band at ∼1665cm−1 assigned to the disordered conformation, suggesting that the adsorption to the Ag sites induces conformational changes in the protein. UVB irradiation of the protein contaminated surfaces caused further changes in the protein conformation, consistent with denaturation and enhanced binding and oxidation, thought to be induced through a photocatalytic mechanism. [Copyright &y& Elsevier]

Abstract: TiO2 thin films are of great interest as biocompatible coatings and also as photocatalytic self-cleaning and antimicrobial coatings. In this work we used β-amyloid as a model for infectious protein to investigate the attachment and photocatalytic degradation. TiO2 films were prepared on stainless steel substrates using magnetron sputtering. The films were characterised before and after exposure to β-amyloid (1–42), using XRD, Raman spectroscopy, XPS and AFM. The TiO2 film was mostly composed of the anatase phase with a relatively high surface roughness. The presence of Raman peaks at 1668cm−1 and 1263cm−1, with the XPS spectral feature for nitrogen at 400eV, confirmed the adsorption of amyloid on surface. Following exposure of the β-amyloid contaminated TiO2 to UV-B irradiation a slight shift of amide modes was observed. Furthermore, the amide I spectra show an overall decrease in α-helix content with presence of a minor peak around 1591cm−1, which is related to tryptophanyl and tyrosinyl radicals, which can lead to conformational change of β-amyloid. The C1s band at 292.2eV suggests the formation of free carboxylic acid. The loss in the crucial structure of β-amyloid leads to reduce the fibril formation, thought to be induced through a photocatalytic process. [Copyright &y& Elsevier]

Abstract: Dual function platinum nanoparticles (PtNPs) incorporating two functions, i.e., DNA capture and electrocatalysis that are physically separated, are described. The physical separation of the two functions significantly enhances the sensitivity of DNA detection giving attomolar limits of detection. The regio-selective functionalisation has been achieved using defects within a dodecanethiol (C12) monolayer deposited on a gold electrode. These defects–nucleation sites allow for the electrodeposition of electrocatalytic, mushroom shaped PtNPs. The monolayer allows one side of the nanoparticle to be functionalised with a 20-base oligonucleotide with a C3 spacer thiol (probe) that selectively captures a sequence specifically associated with the strain of Staphylococcus aureus associated with mastitis. Once functionalised with capture strand DNA, the particles are released by sonication which maintains the structural integrity of the DNA. Thus, the desorbed nanoparticles are capable of biorecognition on the top curved side and electrocatalytic reduction of hydrogen peroxide on the non-functionalised lower surface. A second gold disc electrode was modified with a 15-base oligonucleotide with a C3 spacer thiol (capture). The presence of a 41-base target oligonucleotide, S. Aureus, which hybridized with both capture and probe oligonucleotides, brings the PtNP close to the electrode surface facilitating the electrocatalytic reduction of hydrogen peroxide generating a significant current for each hybridisation event. This highly sensitive detection approach opens up the possibility of avoiding polymerase chain reaction (PCR) or nucleic acid sequence-based amplification (NASBA) based amplification of the target. [Copyright &y& Elsevier]

Abstract: Thin films of a novel Ru-phenolate based metallopolymer, [Ru(terpy)(box)PVP20]PF6, in which one in every twenty of the 4-vinyl pyridine monomer units is labelled with the ruthenium complex have been formed on glassy carbon electrodes, terpy is 2,2′:6′,2″-terpyridine, box is 2-(2-hydroxyphenyl)benzoxazole, and PVP is poly(4-vinylpyridine). Cyclic voltammetry and Raman spectroscopy reveal that the Ru2+/3+ couple is electrochemically reversible but that the phenolate ligand based oxidation is irreversible. These redox processes are associated with reversible colour changes from wine red (reduced) to red orange (mixed composition) then to light green (oxidized) in the visible region and an irreversible change in the near-IR region, respectively. Scanning electron microscopy reveals that repeated switching in LiClO4 aqueous solution does not induce any significant structural change within the deposit films. Cyclic voltammetry has been used to determine the electrochromic switching rate under semi-infinite linear diffusion conditions. In aqueous LiClO4, the homogeneous charge transport diffusion coefficient, D CT, decreases from 3.6±0.3×10−13 to 2.7±0.2×10−13 cm2 s−1 as the LiClO4 concentration increases from 0.1 to 1.0M. This weak dependence of D CT on electrolyte concentration suggests that counterion availability is not rate-determining and that the overall rate of charge transport through the metallopolymer film is limited by the rate of segmental polymer chain motion necessary to bring adjacent centres sufficiently close to allow electron transfer to occur. Also the impact of changing the identity of the charge compensating anion of the redox electrochromic switching rate has been investigated. Finally, the electronic conductivity has been determined using interdigitated array electrodes (IDAs). [Copyright &y& Elsevier]

Abstract: The synthesis of a novel donor–acceptor system comprising a ruthenium polypyridyl unit covalently linked to the secondary face of β-cyclodextrin which has a hydrxy bridged dinuclear copper(II) moiety on its primary face is described and the spectroscopic, electrochemical and photophysical properties of this complex are outlined. Photophysical studies demonstrate evidence for photoinduced electron transfer from the excited ruthenium to the copper centre. The rate of electron transfer, was estimated from luminescence lifetime studies to be 1.86×10−6 s−1. The parent ruthenium polypyridyl functionalized β-cyclodextrin complex binds to both Cu(II) and Zn(II) in alkaline aqueous solution and the affects of these cations on the luminescence intensity of this complex is explored and compared with the photophysics of the isolated supramolecular complex. Whereas Cu(II) statically quenches the ruthenium centre, Zn(II) has little effect. This work suggests luminescent CD complexes, with long-lived luminophores may have value in metal ion sensing. [Copyright &y& Elsevier]

Abstract Dawson-type 18-molybdodisulphate anion [S 2 Mo 18 O 62 ]4-has been immobilized within polypyrrole film by means of electrochemical polymerization. The polymer modified electrodes have been characterized with voltammetry and surface based techniques. The noticeable change in electrochemical properties of [S 2 Mo 18 O 62 ]4- has been observed with immobilization, which is favours its electrocatalytic performance. Hydrogen peroxide reduction in neutral pH as a standard system for electrocatalytic properties assessment has been studied on composite film-modified electrodes and showed the sensitivity of 127 mAM−1cm−2. Developed system showed high stabilities towards redox switching and peroxide reduction. [ABSTRACT FROM AUTHOR]

Gold nanowires with a diameter of 70 ± 20 nm, and gold nanotubes of the same diameter with a wall thicknesses of 20 ± 10 nm, have been electrodeposited within the pores of a track etched polycarbonate membrane filter. These nanowires and nanotubes were then utilised in a DNA detection assay. The top end of the nanowire/nanotube was selectively functionalised with a 20-base oligonucleotide with a C3 spacer thiol (probe strand) that is complementary to a sequence specifically associated with S. Aureus mastitis. Once functionalised with probe strand DNA, the nanowires/nanotubes were released by dissolving the polycarbonate membrane and are capable of biorecognition on the top end of the nanowire and electrocatalytic reduction of hydrogen peroxide along their entire length. A gold disc electrode was modified with a 15-base oligonucleotide with a C3 spacer thiol (capture strand). The target, a 41 base oligonucleotide specific to S. Aureus mastitis, hybridises with both capture and probe oligonucleotides and brings the nanowires close to the electrode surface enabling the electrocatalytic reduction of hydrogen peroxide. Semi-log plots of the pathogen DNA concentration vs. faradaic current are linear from 1 fM to 1 μM and aM concentrations can be detected without the need for molecular, e.g., PCR or NASBA, amplification. [ABSTRACT FROM AUTHOR]

An electrochemical Lab-on-a-Disc (eLoaD) platform for the automated quantification of ovarian cancer cells (SKOV3) from whole blood is reported. This centrifugal microfluidic system combines complex sample handling, i.e., blood separation and cancer cell extraction from plasma, with specific capture and sensitive detection using label-free electrochemical impedance. Flow control is facilitated using rotationally actuated valving strategies including siphoning, capillary and centrifugo-pneumatic dissolvable-film (DF) valves. For the detection systems, the thiol-containing amino acid, l -Cysteine, was self-assembled onto smooth gold electrodes and functionalized with anti-EpCAM. By adjusting the concentration of buffer electrolyte, the thickness of the electrical double layer was extended so the interfacial electric field interacts with the bound cells. Significant impedance changes were recorded at 117.2 Hz and 46.5 Hz upon cell capture. Applying AC amplitude of 50 mV at 117.2 Hz and open circuit potential, a minimum of 214 captured cells/mm 2 and 87% capture efficiency could be recorded. The eLoaD platform can perform five different assays in parallel with linear dynamic range between 16,400 and (2.6±0.0003)×10 6 cancer cells/mL of blood, i.e. covering nearly three orders of magnitude. Using the electrode area of 15.3 mm 2 and an SKOV3 cell radius of 5 µm, the lower detection limit is equivalent to a fractional surface coverage of approximately 2%, thus making eLoaD a highly sensitive and efficient prognostic tool that can be developed for clinical settings where ease of handling and minimal sample preparation are paramount. [ABSTRACT FROM AUTHOR]

Highlights: [•] Self-assembled films of [Ru(bpy)3]2γ*-[W18O54(SO4)2] were prepared at Pt electrodes. [•] Low electrolyte concentrations are required to maintain film integrity. [•] Photocatalysis by [W18O54(SO4)2]4− is sensitized by the ruthenium centres. [•] Photocatalytic performance of the film was optimised under low electrolyte conditions. [•] The highest photocurrent response from POM films under visible irradiation is reported. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and characterisation of iridium(III) bis(2-(2,4-difluorophenyl)pyridinato-N, C2′)-2(4-carboxylphenyl)imidazo[4,5-f][1,10]phenanthroline perchlorate, [Ir(dfpp)2(picCOOH)]+ and its octaarginine conjugate [Ir(dfpp)2(picCONH-Arg8)]9+ are reported. Both complex and conjugate exhibit intense and long-lived luminescence, which is O2 and pH sensitive. Conjugation to the polyarginine peptide renders the complex very water soluble. The uptake of the parent iridium(III) complex and conjugate are compared in two mammalian cell lines; SP2 myeloma and Chinese hamster ovary (CHO). Both complexes internalise into the cytoplasm, however dye uptake rate and distribution vary with peptide conjugation and with cell identity. Whereas transmembrane transport is thought to have been facilitated by the dimethyl sulfoxide (DMSO) used as co-solvent (0.05% v/v) for the parent complex, the octaarginine, the dye-conjugate (iridium-R8) is membrane permeable in water only. Both complexes exhibit high cytotoxicity, evident through blebbing and vacuole formation within living cells, indicative of apoptosis, within 30min of exposure to the probe. The IC50 recorded for the cells in the dark was independent, in the case of the parent complex, of the identity of the cell, with IC50 of 84.8μM and 88μM respectively for SP2 and CHO cells. The IC50 approximately doubled for the polyarginine conjugate and displayed a significant dependence on cell type with IC50 of 35μM and 54.1μM respectively for SP2 and CHO cells. These IC50 values were recorded in the dark. However under irradiation cell death is considerably faster. Evidence from imaging suggests that the conjugate penetrates the nucleus whereas the parent does not, indicating that nuclear penetration may play a role in cytotoxicity. [Copyright &y& Elsevier]