Surface plasmon resonance imaging (SPRi) by enabling label‐free, real time assessment of biomolecular interactions in multiplexed manner is one of the methods of choice for high throughput characterization of large pools of DNA aptamer candidates following in vitro selection. Moreover, with major advances in in situ amplification methods SPRi became also a viable detection platform for aptamer microarrays. In case of aptamer microarrays, commonly prepared by microspotting, the direct assessment of the surface density of aptamer probes, which is essential for both kinetic and sensing measurements is not possible. Therefore, here we introduce a methodology for simple, one‐step determination of surface densities of thiol labelled aptamer monolayers microspotted on gold SPRi chips. Based on this methodology we investigated in detail the effect of the surface density of aptamers on target binding through two aptamer‐target systems, i. e. human immunoglobulin E (hIgE) and six histidine tag 6xHis‐tag. We found that the surface density of the aptamers is indeed critical and shows a sharp maximum in terms of target binding efficiency, which is largely determined by the size of the target. The optimal aptamer surface densities determined, the immobilization chemistry (shared by many detection platforms, e. g., electrochemical, surface acoustic) and the trends identified may be used for rapid rational optimization of aptamer‐target assays.

One-step direct immobilization of peptide-nucleic acid (PNA) probes onto gold surfaces through Au-S chemistry is critical in terms of generating self-assembled monolayers with high hybridization efficiency.We found that this problem is more severe if the immobilization is performed by contact microspotting to generate PNA arrays. Therefore, here we propose a novel microspotting-based immobilization method to generate PNA arrays with high hybridization efficiency on bare gold surface plasmon resonance imaging (SPRi) chips. The essence of the approach is to spot thiol labelled PNA strands prehybridized with a short complementary DNA strand instead of conventionally used single stranded PNA (ssPNA) probes. After immobilization the complementary DNA strands could be easily removed to activate the surface confined PNA probes. The incubation time and the type of spotting needle also have a marked influence on the hybridization efficiency of the PNA layers. However, we show that if all other conditions remain the same, PNA layers from prehybridized PNA probes exhibit superior hybridization efficiency than those from ssPNA probes. † Electronic supplementary information (ESI) available: Typical SPR images and layout of the PNA arrays, results of prescreening of the spotting conditions and unprocessed SPR curves. See

In terms of hybridization assays surface plasmon resonance imaging (SPRi) offers high throughput, label-free and real-time monitoring of the binding kinetics. This requires DNA microarrays on bare or modified gold SPRi chips, which are generally premade by an off-line microspotting procedure.Therefore, the surface density of the immobilized probes is not known although it is an essential quality control parameter, especially, when it can vary in a very broad range as in case of selfassembled thiol-labeled DNAs on gold surface. Here we show that the small molecular weight ruthenium(III) hexamine complex (RuHex) introduced earlier for electrochemical quantitation of DNA coverage on gold electrodes can be used also in SPRi to assess the surface density of DNA probes in DNA microarrays. A single injection of RuHex solution allows the simultaneous visualization and quantification of the surface density of DNA probes (ranging in this study from 4×10 11 to 1.7×10 13 molecules cm -2 ) on all spots of a DNA microarray made by microspotting thiol labeled short DNA probes both in prehybridized and single-stranded form on a gold SPRi chip. The methodology was applied to determine the effect of the surface density of DNA probes on the hybridization efficiency and kinetics of complementary microRNAs, using hsa-miR-208a-3p as model. Single mismatch duplexes were found to be more effectively destabilized than fully complementary duplexes by steric hindrance at large surface densities of the DNA probes, which offers an effective mean to increase single mismatch selectivity.Keywords: DNA surface density, microspotting, surface plasmon resonance imaging, DNA microarray, microRNA DNA probes the critical experimental parameters to be considered for proper hybridization efficiency are well known, e.g., surface density of probes [14-17], probe design [18], the type and length of spacers [19], the nanostructure of the surface [20,21], ionic strength [15]. However, the optimal deployment of nucleic acid probes is also dependent on the type of detection used in the assay that limits the interlope of optimized immobilization methods between the various platforms. In channelmultiplexed SPR systems [22] the immobilization is less complex as requires solely the injection of the relevant coupling agents and probes into the channels. However, also the level of multiplexing is significantly smaller compared to photolithography or methods based on the local delivery and

TiO2/WO3 nanofibers were prepared in a one-step process by electrospinning. Titanium(IV) bis(ammonium lactato)dihydroxide (TiBALDH) and ammonium metatungstate (AMT) were used as water-soluble Ti and W precursors, respectively. Polyvinylpyrrolidone (PVP) and varying ratios of TiBALDH and AMT were dissolved in a mixture of H2O, EtOH and CH3COOH. The as-spun fibers were then heated in air at 1 °C min−1 until 600 °C to form TiO2/WO3 composite nanofibers. Fiber characterization was done using TG/DTA, SEM–EDX, FTIR, XRD, and Raman. The annealed composite nanofibers had a diameter range of 130–1940 nm, and the results showed a growth in the fiber diameter with an increasing amount of WO3. The photocatalytic property of the fibers was also checked for methyl orange bleaching in visible and UV light. In visible light, the photocatalytic activity increased with an increase in the ratio of AMT, while 50% TiBALDH composite fibers showed the highest activity among the as-prepared fibers in UV light.

A new electrospinning process was developed for preparing TiO 2 nanofibers using a water-soluble Ti-precursor, [bis(kappa1O-hydroxo)(bis(kappa2O,O 0 -lactato)titanium(IV)] commonly known as titanium(IV) bis (ammonium lactato) dihydroxide (TiBALDH). The importance of the study is justified by the fact that Ti-precursors used for electrospinning, sol-gel, hydrothermal and other fiber synthesis processes are mostly non-water soluble. Accordingly, anatase TiO 2 nanofibers of diameter between 20 and 140 nm were synthesized by electrospinning and annealing. Polyvinylpyrrolidone (PVP) and different concentrations of TiBALDH were dissolved in a mixture of water, ethyl alcohol and acetic acid to optimize the electrospinning conditions. The thermal decomposition and fragmentation of PVP, TiBALDH and the fibers with 50% mass fraction of TiBALDH were studied by TGA-MS measurements. The fibers were then annealed at 1°C min -1 until 600°C. The TiO 2 fibers were characterized using SEM-EDX, FTIR and XRD