Biosensor based on chemically-designed anchorable cytochrome c for the detection of H2O2 released by aquaticcells

Abstract

a b s t r a c tA novel third generation biosensor was developed based on one-shot adsorption of chemicallymodified cytochrome c (cyt c) onto bare gold electrodes. In contrast to the classic approach which consists of attaching cyt c onto an active self-assembled monolayer (SAM) priory chemisorbed on gold, here short-chain thiol derivatives (mercaptopropionic acid, MPA) were chemically introduced on cyt c protein shell via its lysine residues enabling the very fast formation (o 5 min) of an electroactive biological self-assembled monolayer (SAM) exhibiting a quasi-reversible electrochemical behavior and a fast direct electron transfer (ET). The heterogeneous ET rate constant was estimated to be k s ¼ 1600 s, confirming that short anchors facilitate the ET via an efficient orientation of the heme pocket. In comparison, no ET was observed in the case of native and long-anchor (mercaptoundecanoic acid, MUA) modified cyt c directly adsorbed on gold. However, in both cases the ET was efficiently restored upon in-bulk generation of gold nanoparticles which acted as electron shuttles. This observation emphasizes that the lack of electroactivity might be caused by either an inappropriate orientation of the protein (native cyt c) or a critical distance (MUA-cyt c). Finally, the sensitivity of the bare gold electrode directly modified with MPA-cyt c to hydrogen peroxide (H 2 O 2 ) was evaluated by amperometry and the so-made amperometric biosensor was able to perform real-time and noninvasive detection of endogeneous H 2 O 2 released by unicellular aquatic microorganisms, Chlamydomonas reinhardtii, upon cadmium exposure.

Silver nanoparticle toxicity and association with the alga Euglena gracilis

“…showing that the toxicity of AgNP to algae was dependent on dissolved Ag in the exposure medium, [7][8][9]29 we hypothesized that also in E. gracilis the dissolved Ag was a major contributor of AgNP toxicity. 30,31 AgNP and AgNO 3 also affected the morphology of E. gracilis cells. Accordingly, the effects on photosynthesis were completely prevented, thus supporting our hypothesis that the toxicity of AgNP was due to dissolved Ag.…”

Modulation of the Silica Sol–Gel Composition for the Promotion of Direct Electron Transfer to Encapsulated Cytochrome c

“…Accordingly, several strategies for the immobilization of enzymes have been assayed: covalent binding 15,16 , physical adsorption [17][18][19][20][21] or encapsulation within polymeric matrices 22 .…”

A miniaturized electrochemical assay for homocysteine using screen-printed electrodes with cytochrome c anchored gold nanoparticles

“…S3. This may be due to the better affinity of cyt c to the GNP than to carbon, resulting in immobilization of more cyt c. 46 An earlier reported strategy 47 indicates that cyt c shows its optimum activity at pH 7.0, hence, the present immobilization process does not strongly affect the catalytic function of cyt c. Prior to the addition of HcySH, no changes were observed on both surfaces, whereas after addition a clear oxidation peak was observed at the potential starting from +0.3 V and extending to +0.6 V, which is in agreement with earlier reports. S3, † curve a) shows a higher current response than on the bare SPE (curve b).…”