Fabrication of solid‐state nanopores and its perspectives

Nanofluidics is becoming an extensively developing technique in the field of bioanalytical chemistry. Nanoscale hole embed in an insulating membrane is employed in a vast variety of sensing platforms and applications. Although, biological nanopores have several attractive characteristics, in this paper, we focused on the solid‐state nanopores due to their advantages as high stability, possibility of diameter control, and ease of surface functionalizing. A detection method, based on the translocation of analyzed molecules through nanochannels under applied voltage bias and resistive pulse sensing, is well established. Nevertheless, it seems that the new detection methods like measuring of transverse electron tunneling using nanogap electrodes or optical detection can offer significant additional advantages. The aim of this review is not to cite all related articles, but highlight the steps, which in our opinion, meant important progresses in solid‐state nanopore analysis.     

Biosynthesis of Quantum Dots (CdTe) and its Effect on Eisenia fetida and Escherichia coli

Biosynthesis belongs to one of the new possibilities of nanoparticles preparation, whereas its main advantage is biocompatibility. In addition, the ability of obtaining the raw material for such synthesis from the soil environment is beneficial and could be useful for remediation. However, the knowledge of mechanisms that are necessary for the biosynthesis or effect on the bio-synthesizing organisms is still insufficient. In this study, we attempted to evaluate the effect of quantum dots (QDs) not only on a model organism of collembolans, but also on another soil organism—earthworm Eisenia fetida—and in also one widespread microorganism such as Escherichia coli. Primarily, we determined 28EC₅₀ as 72.4 μmol L^?1 for CdTe QDs in collembolans. Further, we studied the effect of QDs biosynthesis in E. fetida and E. coli. Using determination of QDs, low-molecular thiols and antioxidant activities, we found differences between both organisms and also between ways how they behave in the presence of Cd and/or Cd and Te. The biosynthesis in earthworms can be considered as its own protective mechanism; however, in E. coli, it is probably a by-product of protective mechanisms.     

Paramagnetic Particles and PNA Probe for Automated Separation and Electrochemical Detection of Influenza

Considerable efforts have been devoted to the development of rapid and sensitive methods allowing the detection of viral nucleic acid. We herein describe an assay for identification of a specific influenza sequence. The suggested method was based on isolation using paramagnetic particles coupled with electrochemical detection of isolated product. Peptide nucleic acid (PNA) was used as a probe for hybridization and identification of the influenza-derived specific sequence. The use of PNA can show numerous benefits: PNA probe is not degradable by enzymes and the duplex of PNA with RNA/DNA is more thermostable and more resistant to pH changes than DNA/DNA or RNA/RNA duplexes. This PNA probe assay can be applied as a magnetically guidable tool for detection of DNA/RNA samples under different conditions.

     

Enhancement of surface wettability via the modification of microtextured titanium implant surfaces with polyelectrolytes

Micrometer- and submicrometer-scale surface roughness enhances osteoblast differentiation on titanium (Ti) substrates and increases bone-to-implant contact in vivo. However, the low surface wettability induced by surface roughness can retard initial interactions with the physiological environment. We examined chemical modifications of Ti surfaces [pretreated (PT), R(a) ≤ 0.3 μm; sand blasted/acid etched (SLA), R(a) ≥ 3.0 μm] in order to modify surface hydrophilicity. We designed coating layers of polyelectrolytes that did not alter the surface microstructure but increased surface ionic character, including chitosan (CHI), poly(L-glutamic acid) (PGA), and poly(L-lysine) (PLL). Ti disks were cleaned and sterilized. Surface chemical composition, roughness, wettability, and morphology of surfaces before and after polyelectrolyte coating were examined by X-ray photoelectron spectroscopy (XPS), contact mode profilometry, contact angle measurement, and scanning electron microscopy (SEM). High-resolution XPS spectra data validated the formation of polyelectrolyte layers on top of the Ti surface. The surface coverage of the polyelectrolyte adsorbed on Ti surfaces was evaluated with the pertinent SEM images and XPS peak intensity as a function of polyelectrolyte adsorption time on the Ti surface. PLL was coated in a uniform thin layer on the PT surface. CHI and PGA were coated evenly on PT, albeit in an incomplete monolayer. CHI, PGA, and PLL were coated on the SLA surface with complete coverage. The selected polyelectrolytes enhanced surface wettability without modifying surface roughness. These chemically modified surfaces on implant devices can contribute to the enhancement of osteoblast differentiation.     

Electrophoretic fingerprint metallothionein analysis as a potential prostate cancer biomarker

Prostate-specific antigen (PSA) is a routinely used marker of prostate cancer; however, the cut-off values for unambiguous positive/negative prostate cancer diagnoses are not defined. Therefore, despite the best effort, certain percentage of misdiagnosed cases is being recorded every year. For this reason, search for more specific diagnostic markers is of great interest. In this study, systematic comparison of PSA and metallothionein (MT) levels in blood serum of 46 prostate cancer-diagnosed patients is presented. It is clearly demonstrated that PSA levels vary significantly and despite normal total PSA values in the range of 0 - 4?ng/mL were obtained in over 36.9% of cases, positive prostate cancer was diagnosed by biopsy. In contrary, MT levels were considerably elevated in all tested samples and no significant variations were observed. These results are indicating the potential of MT as an additional prostate cancer marker reducing, in combination with PSA, the probability of false positive/negative diagnosis. To increase the throughput of the screening, chip-based capillary electrophoresis was suggested as a rapid and effective method for the fingerprinting analysis of prostate cancer from diseased blood sera.     

Microfluidic robotic device coupled with electrochemical sensor field for handling of paramagnetic micro-particles as a tool for determination of plant mRNA

The expression of genes responsible for the biosynthesis of stress proteins corresponds to the exposition of an organism to abiotic and/or biotic stress. We utilize two types of paramagnetic particles for isolation of total mRNA from early somatic embryos of Norway Spruce (Picea abies /L./ Karst.) and maize plants (Zea mays L.) treated with cadmium(II) ions. The paramagnetic particles were evaluated for analysis of real samples, and poly-adenine was used as a model mRNA. Various approaches (from non-automatic to fully automatic) were tested in terms of handling the particles.

17O NMR and computational study of a tetrasiliconiobate ion, [H(2+x)Si4Nb16O56](14-x)-

Rates of oxygen-isotope exchange were measured in the tetrasiliconiobate ion [H(2+x)Si(4)Nb(16)O(56)]((14-x)-) to better understand how large oxide ions interact with water. The molecule has 19 nonequivalent oxygen sites and is sufficiently complex to evaluate hypotheses derived from our previous work on smaller clusters. We want to examine the extent to which individual oxygen atoms react independently with particular attention given to the order of protonation of the various oxygen sites as the pH decreases from 13 to 6. As in our previous work, we find that the set of oxygen sites reacts at rates that vary over approximately 10(4) across the molecule at 6相似文献   

Cytotoxic gold(I)-bearing dendrimers from alkyne precursors

A series of four dendrimers end-functionalized with gold(I) has been prepared from alkyne-terminated precursors and (tricyclohexylphosphine)gold(I) azide. Isolated yields range from 84-89%, based on gold. The first-generation dendrimer is cytotoxic toward 3T3 mouse fibroblast cells. Apoptosis ensues within 6 h of treatment with gold(I).     

Surprising photochemical reactivity and visible light-driven energy transfer in heterodimetallic complexes

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been used for the synthesis of a series of novel heterodimetallic complexes starting from [Ru(bpy)(2)(dppcb)]X(2) (1; X = PF(6), SbF(6)), so-called dyads, showing surprising photochemical reactivity. They consist of [Ru(bpy)(2)](2+)"antenna" sites absorbing light combined with reactive square-planar metal centres. Thus, irradiating [Ru(bpy)(2)(dppcb)MCl(2)]X(2) (M = Pt, 2; Pd, 3; X = PF(6), SbF(6)) dissolved in CH(3)CN with visible light, produces the unique heterodimetallic compounds [Ru(bpy)(CH(3)CN)(2)(dppcb)MCl(2)]X(2) (M = Pt, 7; Pd, 8; X = PF(6), SbF(6)). In an analogous reaction the separable diastereoisomers (ΔΛ/ΛΔ)- and (ΔΔ/ΛΛ)-[Ru(bpy)(2)(dppcb)Os(bpy)(2)](PF(6))(4) (5/6) lead to [Ru(bpy)(CH(3)CN)(2)(dppcb)Os(bpy)(2)](PF(6))(4) (9), where only the RuP(2)N(4) moiety of 5/6 is photochemically reactive. By contrast, in the case of [Ru(bpy)(2)(dppcb)NiCl(2)]X(2) (4; X = PF(6), SbF(6)) no clean photoreaction is observed. Interestingly, this difference in photochemical behaviour is completely in line with the related photophysical parameters, where 2, 3, and 5/6, but not 4, show long-lived excited states at ambient temperature necessary for this type of photoreaction. Furthermore, the photochemical as well as the photophysical properties of 2-4 are also in accordance with their single crystal X-ray structures presented in this work. It seems likely that differences in "steric pressure" play a major role for these properties. The unique complexes 7-9 are also fully characterized by single-crystal X-ray structure analyses, clearly showing that the stretching vibration modes of the ligand CH(3)CN, present only in 7-9, cannot be directly influenced by "steric pressure". This has dramatic consequences for their photophysical parameters. The trans-[Ru(bpy)(CH(3)CN)(2)](2+) chromophore of 9 acts as efficient "antenna" for visible light-driven energy transfer to the Os-centred "trap" site, resulting in k(en) ≥ 2 × 10(9) s(-1) for the energy transfer. Since electron transfer is made possible by the use of this intervening energy transfer, in dyads like 2-4 highly reactive M(0) species (M = Pt, Pd, Ni) could be generated. These species are not stable in water and M(II) hydride intermediates are usually formed, further reacting with H(+) to give H(2). Thus, derivatives of 3, namely [M(bpy)(2)(dppcb)Pd(bpy)](PF(6))(4) (M = Os, Ru) dissolved in 1:1 (v/v) H(2)O-CH(3)CN produce H(2) during photolysis with visible light.     

Antimicrobial activities of indole alkaloids from Tabernaemontana catharinensis

Tabernaemontana catharinensis root bark ethanol extract, EB2 fraction and the MMV alkaloid (12-methoxy-4-methylvoachalotine) were evaluated for their antimicrobial activities. T. catharinensis ethanol extract was effective against both strains of the dermatophyte Trichophyton rubrum at concentrations of 2.5 mg/mL (wild strain) and 1.25 mg/mL (mutant strain), while the EB2 fraction and MMV alkaloid showed a strong antifungal activity against wild and mutant strains with MIC values of <0.02 and 0.16 mg/mL, respectively. The EB2 fraction showed a strong antibacterial activity against ATCC strains of S. aureus, S. epidermidis, E. coli and P. aeruginosa with MICs from <0.02 to 0.04 mg/mL, as well as against resistant clinical isolates species of Enterococcus sp, Klebsiella oxytoca, Citrobacter, K. pneumoniae, P. mirabilis, S. aureus, S. epidermidis, E. coli and P. aeruginosa with MIC values ranging from 0.04 to 0.08 mg/mL. The MMV alkaloid presented a MIC of 0.16 mg/mL against the strains of S. aureus and E. coli ATCC. For the resistant clinical isolates Enterococcus sp, Citrobacter, S. aureus, S. epidermidis, E. coli and P. aeruginosa the MIC of MMV ranged from 0.08 to 0.31 mg/mL. The chromatography analysis of the EB2 fraction revealed the presence of indole alkaloids, including MMV, possibly responsible for the observed antimicrobial activity.