In this paper, we present the development of a highly sensitive, specific and reproducible nanobiosensor to detect one specific liver cancer biomarker, the manganese super oxide dismutase (MnSOD). The high sensitivity and reproducibility was reached by using SERS on gold nanostructures (nanocylinders and coupled nanorods) produced by electron-beam lithography (EBL). The specificity of the detection was provided by the use of a specific aptamer with high affinity to the targeted protein as a recognition element. With such a sensor, we have been able to observe the SERS signal of the MnSOD at concentrations down to the nM level and to show with negative control that this detection is specific due to the use of the aptamer. This latter issue has allowed us to detect the MnSOD in different body fluids (serum and saliva) at concentrations in the nM range. We have then demonstrated the effectiveness of our SERS nanobiosensor using aptamer as a bioreceptor for the detection of disease biomarker at low concentration and in complex fluids.

In this study, a simple fluorogenic immunoassay based on in situ formation of semiconductor quantum dots (QDs) is described. We discovered that alkaline phosphatase (ALP), the enzyme broadly used in enzyme-linked immuno-sorbent assay (ELISA), is able to trigger formation of fluorescent CdS QDs. ALP-catalyzed hydrolysis of p-nitrophenyl phosphate (pNPP) leads to the formation of p-nitrophenol and inorganic phosphate. The latter stabilizes CdS QDs produced in situ through interaction of Cd(2+) with S(2-) ions. So, the specific interaction of analyte (antibody) with ALP-labeled antibody can be detected through formation of CdS QDs, monitored by recording emission spectra at λex = 290 nm. The fluorescence intensity showed to be dependent on the concentration of target antibody. This method allowed us to detect as low as 0.4 ng mL(-1) of analyte antibody with a linear range up to 10 ng mL(-1). The sensitivity of this novel assay showed to be 1 order of magnitude better than that of the standard method based on colorimetric p-nitrophenyl phosphate assay.

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Copper is an essential element for regulation of many biological processes, however, in excess it is considered to be toxic for human health. This metal is frequently accompanied by other elements such as cadmium, nickel and lead. Thus, developing a selective and simple method for determination of copper in a matrix containing other heavy metal ions is of great importance. In this work, a novel selective method for copper detection was developed using electrodes modified with the DNAzyme capturing Cu(2+) ions. The DNAzyme reconstituted with copper catalyzes oxidation of ascorbic acid leading to the build-up and adsorption of oxidation products on the electrode surface and produces changes in the interfacial properties of the electrode. The increase in the interfacial electron-transfer resistance is probed with electrochemical impedance spectroscopy (EIS) in the presence of the reversible redox couple [Fe(CN)6](3-)/[Fe(CN)6](4-) as a marker. The DNAzyme based biosensor combines excellent selectivity against other heavy metal ions with sufficient sensitivity to Cu(2+) in the range of 6.5-40 μM.

Aldehydes and ketones caged as 4-(2,5-dihydroxyphenyl)-1,3-dioxolanes are efficiently (Phi = 0.1-0.2) released in a good to excellent chemical yield upon irradiation with 300 nm light. Caged carbonyl compounds are prepared by their acetalization with (2,5-dimethoxyphenyl)ethylene glycol followed by oxidative demethylation to produce corresponding (1,3-dioxolane-4-yl)-1,4-benzoquinones. The latter acetals are photochemically inert but can be converted into photolabile hydroquinones by mild reduction in situ.