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This document is a correction notice for an article titled "Exploiting the high conjugation capacity of creatinine on 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester) functionalized gold nanoparticles towards sensitive determination of mercury (II) ion in water" published in the Journal of Nanostructure in Chemistry. The correction addresses errors in the TEM image and FTIR spectra included in the original article. The authors apologize for the mistakes and state that the corrected figures do not change the results and conclusions of the paper. The correction notice includes the corrected TEM image and FTIR spectra. The publisher, Springer Nature, remains neutral regarding jurisdictional claims and institutional affiliations. [Extracted from the article]

In this study, we present a facile and inexpensive colorimetric sensor for hydrogen peroxide (H2O2) and glucose based on the formation of an Fe3+ complex assisted by the Fenton reaction in a micellar medium. The mechanism of the sensor is based on the Fenton reaction occurring between the added H2O2 and ferrous ion (Fe2+) probe, which was stabilized by complexing with dithizone (Dz) before forming a micelle with the non-ionic surfactant Triton X-114 (TX-114). The extremely reactive hydroxyl radical (˙OH), the by-product of the Fenton reaction, exhibited much stronger oxidizing ability than H2O2, and thus strongly oxidized the stabilized Fe2+ ion, thereby accelerating the spectrophotometric response of the Fe3+ ion after coordinating with the thiocyanate ion (SCN−). The obtained absorbance of the Fe3+ and SCN− complex was related to the concentration of H2O2. Under the optimal condition, the micelle probe of Fe2+ exhibited good stability, without transforming to Fe3+ within 24 h. The sensor achieved an LOD of 5 μM and provided a linear range of 10 μM–4.0 mM for H2O2 determination. When coupled with glucose oxidase to generate a biosensing system, glucose was changed to H2O2 and could be measured down to 10 μM within a linear range of 10 μM–4.0 mM. The interferences naturally found in human blood plasma at the physiological level had no obvious effects on the glucose biosensor. According to the comparison with the hexokinase-spectrophotometric method used by hospitals, the results obtained from the proposed method for glucose measurements in human plasma samples were in good agreement (p > 0.05). This indicated the enormous potential of combining the Fenton reaction and micellar system-stabilized metal ion complex probes to design sensors for the alternative detection of H2O2 and glucose. [ABSTRACT FROM AUTHOR]

Mercury (Hg) contamination of the major environmental matrices, arising from human indiscriminate pursuit of industrialization without recourse to environment beneficiation is rife and worrisome. Amongst all the different forms of Hg, huge interest has been devoted to the inorganic Hg2+ determination, especially in water. Herein, a creatinine (CRN) conjugated on 3,3′-dithiodipropionic acid di(N-hydroxysuccinimide ester) (DTSP) functionalized gold nanoparticles (Au@DTSP/CRN)-based colorimetric assay was developed for Hg2+ detection in water samples. The DTSP was used to functionalize gold nanoparticles through the Au–S interaction, so as to impart a significantly high stability on the fabricated Au@DTSP, while also conferring coordination capacity on the nanoparticles. The Au@DTSP can bind to the amino group of CRN through its N-hydroxysuccinimide ester moiety, with the formation of an amide bond. The generated optical probe Au@DTSP/CRN aggregated in the presence of Hg2+, with a distinct change of solution colors from ruby red, through purple and to blue-grey within 10 min. The detection limit of 28.5 nM was achieved with linear calibration curves within 0.10–0.35 and 0.35–4.00 μM, while using the absorbance ratio (A680/A521) as the analytical response. Recoveries of 99.0–103.2% were obtained and the relative standard deviations were less than 5.5%. The Au@DTSP/CRN nanoprobe was applied for quantitative determination of Hg2+ in real water samples without significant interference from other metal ions, which is a positive indication of its utilitarian potentiality for Hg2+ profiling in aqueous environment. [ABSTRACT FROM AUTHOR]

A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportional to miRNA-21 concentrations between 0.20 fM and 1.0 nM, with a very low detection limit of 0.20 fM. The biosensor showed a high specificity which could discriminate between complementary, single-, doubled-base mismatched, and non-complementary targets. Three out of the seven tested plasma samples provided detectable concentrations (63 ± 4, 111 ± 4 and 164 ± 7 fM). The sensor also showed good recoveries (81–119%). The results indicated the possibilities of this biosensor for analysis without RNA extraction and/or amplification, making the sensor potentially useful for both the prognosis and diagnosis of cancer in clinical application. [ABSTRACT FROM AUTHOR]

This work describes the combined electrocatalytic and synergistic properties of gold nanoparticles (AuNPs) decorated multiwalled carbon nanotubes (MWCNTs) and the large surface area of chitosan (CS) cryogel for the fabrication of a highly sensitive and stable electrochemical non-enzymatic sensor. MWCNTs were pre-mixed with citrate ions that serve as the substrate for gold deposition along their chains. The AuNPs-MWCNTs nanocomposite and chitosan cryogel were easily modified on a gold electrode in only 1 h by freezing and thawing of the mixture after casting it on the electrode surface. Glucose, as a model analyte, was measured by the developed electrode in a flow-injection amperometric system. A fast response time and excellent sensitivity were obtained. The sensor exhibited a linear range between 0.001 and 1.0 mM with a low detection limit (0.5 μM) and a high operational stability (525 injections). There were no effects from the common interferences found in physiological levels in blood samples. After measuring glucose in human blood plasma using this sensor, the results were in good agreement ( P > 0.05) with those obtained from the standard spectrophotometrically-measured hexokinase method employed clinically. These good performances made this sensor a potential alternative tool for the detection of glucose and other oxidizable analytes. [ABSTRACT FROM AUTHOR]

Insulin is the polypeptide hormone that regulates blood glucose levels. It is used as an indicator of both types of diabetes. An electrochemical insulin sensor was developed using a gold electrode modified with carboxylated multiwalled carbon nanotubes (f-MWCNTs) and molecularly imprinted polymer (MIP) cryogel. The MIP provided specific recognition sites for insulin, while the macropores of the cryogel promoted the mass transfer of insulin to the recognition sites. The f-MWCNTs increased the effective surface area and conductivity of the sensor and also reduced the potential required to oxidize insulin. Insulin oxidation was directly measured in a flow system using square wave voltammetry. This MIP cryogel/f-MWCNTs sensor provided a linear range of 0.050–1.40 pM with a very low limit of detection (LOD) of 33 fM. The sensor exhibited high selectivity and long-term stability over 10 weeks of dry storage at room temperature. The results of insulin determination in human serum using the sensor compared well with the results of the Elecsys insulin assay. The developed MIP sensor offers a promising alternative for the diagnosis and treatment of diabetes. [Display omitted] • A molecularly imprinted polymer (MIP) sensor was synthesized. • The sensor directly detected insulin electro-oxidation in a flow system. • Insulin detection was highly selective against other proteins and small molecules. • The sensor can assess insulin levels in people with type 1 and type 2 diabetes. • The sensor could be used accurately up to 46 times. [ABSTRACT FROM AUTHOR]

This study introduces a disposable electrochemical sensor for measuring caffeine (CAF) based on a screen-printed electrode modified with a copper-based metal organic framework and multi-walled carbon nanotube nanocomposite (Cu-MOF@f-MWCNTs/SPE). The f-MWCNTs improved the conductivity and specific surface area of the electrode, and the f-MWCNTs/SPE demonstrated excellent electrocatalytic activity toward CAF oxidation. Incorporating Cu-MOF with f-MWCNTs increased the number of active sites for CAF oxidation, leading to a significant increase in the oxidation current response of CAF. The morphology of the Cu-MOF@f-MWCNT nanocomposite was observed by scanning electron microscopy. The electrochemical behavior of CAF on different electrode modifications was investigated using cyclic voltammetry and differential pulse voltammetry. The optimal detection conditions were also evaluated. The linear range of the developed sensor was from 0.010 to 1.50 mM, and the detection limit was 7.9 μM. The sensor showed selectivity against six possible interferents and achieved recoveries from 85.0 to 104.6% of CAF in black coffee samples. Hence, the proposed disposable CAF sensor could be used in real-world applications. [ABSTRACT FROM AUTHOR]