An appealing alternative approach to the conventional electrochem. deposition is presented, which can be universally utilized to form nanomaterial coatings from their aq. dispersions without involving their oxidn.-redn. It is based on altering the ionic strength by elec. potential in the vicinity of the electrode surface, which causes the nanomaterials to deposit. The concept has been demonstrated for four different systems. [on SciFinder(R)]

Sensitive and selective detection of cancer biomarkers is vital for the successful diagnosis of early stage cancer and follow-up treatment. Surface Plasmon Resonance (SPR) in combination with different amplification strategies is one of the anal. approaches allowing the screening of protein biomarkers in serum. Here we describe the development of a point-of-care sensor for the detection of folic acid protein (FAP) using graphene-based SPR chips. The exceptional properties of CVD graphene were exploited to construct a highly sensitive and selective SPR chip for folate biomarker sensing in serum. The specific recognition of FAP is based on the interaction between folic acid receptors integrated through π-stacking on the graphene coated SPR chip and the FAP analyte in serum. A simple post-adsorption of human serum:bovine serum albumin (HS:BSA) mixts. onto the folic acid modified sensor resulted in a highly anti-fouling interface, while keeping the sensing capabilities for folate biomarkers. This sensor allowed femtomolar (fM) detection of FAP, a detection limit well adapted and promising for quant. clin. anal. [on SciFinder(R)]

Molecularly imprinted polymer (MIP) particles offer many advantages as recognition objects. Therefore, we examd. thoroughly the effect of various exptl. parameters including cross-linker concn., nature of solvent, type of template and its concn., reaction vol. and temp. on the formation of particulate MIPs using pptn. polymn. The particles were characterized by various methods, such as XHR-SEM, HR-TEM and BET. Statistical calcns. were carried out using ImageJ software over population of at least 200 particles in each expt. The reproducibility of MIP synthesis was examd. and the SD was better than 10%. MIP particles were imprinted with different Sudan dye derivs. (Sudan II, III, IV and Sudan orange G). Raman and FTIR spectroscopies were used to prove the successful imprinting. Reuptake measurements were carefully compared between non-imprinted molecularly polymer (NIP) and MIP particles employing the same quantity and similar diam. and polydispersity of NIP and MIP, as never reported before. The results showed that MIP particles imprinted by Sudan IV showed higher selectivity toward this specific dye as compared with MIPs imprinted by other Sudan dyes and NIPs. [on SciFinder(R)]

Measuring and monitoring of protein oxidn. modifications is important for biopharmaceutical process development and stability assessment during long-term storage. Currently available methods for biomols. oxidn. anal. use time-consuming peptide mapping anal. Therefore, it is desirable to develop high-throughput methods for advanced process control of protein oxidn. Here, we present a novel approach by which oxidative protein modifications are monitored by an indirect potentiometric method. The method is based on adding an electron mediator, which enhances electron transfer (ET) between all redox species and the electrode surface. Specifically, the procedure involves measuring the sharp change in the open circuit potential (OCP) for the mediator system (redox couple) as a result of its interaction with the oxidized protein species in the soln. Application of Pt and Ag/AgCl microelectrodes allowed for a high-sensitivity protein oxidn. anal. We found that the Ru(NH3)2+/3+6 redox couple is suitable for measuring the total oxidn. of a wide range of therapeutic proteins between 1.1 and 13.6%. Accuracy detd. by comparing with the known percentage oxidn. of the ref. std. showed that percentage oxidn. detd. for each sample was within ±20% of the expected percentage oxidn. detd. by mass spectrometry. [on SciFinder(R)]

The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and sepn. based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochem. detection using the concept of "nanoparticles imprinted matrixes" (NAIM). Neg. charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The selective matrix is formed by the adsorption of either oleic acid (OA) or poly(acrylic acid) (PAA) on the non-occupied areas. The AuNPs are removed by electrooxidn. to form complementary voids. These voids are able to recognize the AuNPs selectively based on their size. Furthermore, the selectivity could be improved by adsorbing an addnl. layer of 1-hexadecylamine, which deepened the voids. Interestingly, silver nanoparticles (AgNPs) were also recognized if their size matched those of the template AuNPs. The steps in assembling the NAIMs and the reuptake of the nanoparticles were characterized carefully. The prospects for the anal. use of NAIMs, which are simple, of small dimension, cost-efficient and portable, are in the sensing and sepn. of nanoobjects. [on SciFinder(R)]

The electrochemical detection of mercury in aqueous solutions was studied at glassy carbon (GC) and indium-tin oxide (ITO) electrodes modified by gold nanoparticles (Au NPs). Two methods of modification were used: electrochemical reduction of HAuCl4 and electrostatic adsorption of Au NPs stabilized by citrate. We found that the Au NPs modified surfaces yielded higher sensitivity and sharper and more reproducible stripping peaks of Hg as compared with the bare electrodes. The effect of the modification by Au NPs on the stripping potential was examined. Interestingly, the stripping of Hg on GC and ITO modified by Au NPs occurred at the same potential as on bare GC and ITO, respectively. Only the full coverage of ITO by either electrochemically deposited Au for a long time or by vapor deposition, shifted the stripping potential more positive by ca. 0.4 V to that observed on a bare Au electrode. These and further experiments led us to conclude that the Au NPs served as nucleation sites for the deposition of Hg, whereas the GC or ITO are superior for the stripping of mercury. Hence, a combination of well-defined Au NPs on ITO or GC were found ideal for the electrochemical detection of Hg. Indeed, we achieved a remarkable detection limit of 1 μm·L(-1) of Hg using an ITO surface modified by electrostatically adsorbed Au NPs.[on SciFinder (R)]

In this work we report the sensitive electroanalytical detection of uranium(VI) in aqueous solutions. Uranium commonly exists in aqueous solutions in the form of its oxo ion, uranyl (U(VI)O2(2+)). The detection of uranyl has been accomplished by us through its deposition upon reduction by two electrons to the insoluble UO2 using a bare disk gold macroelectrode and anodic stripping voltammetry (ASV). This gave an unsatisfactory detection limit of ca. 1 × 10(-5) M uranyl. Moreover, the evolution of hydrogen bubbles blocked the electrode surface as a result of water reduction at negative deposition potential (-0.7 V vs Ag/AgCl). The application of a 25 μm diameter Au microwire electrode on which UO2 precipitated at negative potential (-1.2 V) improved substantially the detection limit. Further improvement was accomplished by vibrating the microwire working electrode, which increased the amounts of UO2 deposition due to decreasing the diffusion layer. The effect of the vibrating amplitude and frequency on the electroanalytical response was studied and optimized. Eventually, a detection limit of ca. 1 × 10(-9) M uranyl was achieved using a 5 min deposition time, -1.2 V deposition potential, and vibrating the electrode at frequency of 250 Hz and amplitude of 6 V.[on SciFinder (R)]