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Open AccessArticle

Supercritical Carbon Dioxide Impregnation of Gold Nanoparticles Demonstrates a New Route for the Fabrication of Hybrid Silk Materials

by Manish Singh, Estera S. Dey, Sunil Bhand and Cedric Dicko

Insects 2022, 13(1), 18; https://doi.org/10.3390/insects13010018 - 23 Dec 2021

Cited by 5 | Viewed by 4993

Abstract

How many nanoparticles can we load in a fiber? How much will leak? Underlying is the relatively new question of the “space available” in fibers for nanoparticle loading. Here, using supercritical carbon dioxide (scCO₂) as a carrier fluid, we explored the impregnation in four Indian silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold nanoparticles (5, 20, 50, 100 and 150 nm in diameter). All silks could be permanently impregnated with nanoparticles up to 150 nm in size under scCO₂ impregnation. Accompanying structural changes indicated that the amorphous silk domains reorganized to accommodate the gold NPs. The mechanism was studied in detail in degummed Mulberry silk fibers (i.e., without the sericin coating) with the 5 nm nanoparticle. The combined effects of concentration, time of impregnation, scCO₂ pressure, and temperature showed that only a narrow set of conditions allowed for permanent impregnation without deterioration of the properties of the silk fibers. Full article

(This article belongs to the Special Issue Silkworm and Silk: Traditional and Innovative Applications)

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19 pages, 1478 KB

Open AccessReview

Designed Strategies for Fluorescence-Based Biosensors for the Detection of Mycotoxins

by Atul Sharma, Reem Khan, Gaelle Catanante, Tauqir A. Sherazi, Sunil Bhand, Akhtar Hayat and Jean Louis Marty

Toxins 2018, 10(5), 197; https://doi.org/10.3390/toxins10050197 - 11 May 2018

Cited by 94 | Viewed by 10804

Abstract

Small molecule toxins such as mycotoxins with low molecular weight are the most widely studied biological toxins. These biological toxins are responsible for food poisoning and have the potential to be used as biological warfare agents at the toxic dose. Due to the poisonous nature of mycotoxins, effective analysis techniques for quantifying their toxicity are indispensable. In this context, biosensors have been emerged as a powerful tool to monitors toxins at extremely low level. Recently, biosensors based on fluorescence detection have attained special interest with the incorporation of nanomaterials. This review paper will focus on the development of fluorescence-based biosensors for mycotoxin detection, with particular emphasis on their design as well as properties such as sensitivity and specificity. A number of these fluorescent biosensors have shown promising results in food samples for the detection of mycotoxins, suggesting their future potential for food applications. Full article

(This article belongs to the Special Issue Advanced Sensors for Toxins)

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15 pages, 2112 KB

Open AccessReview

Recent Advances in Electrochemical-Based Sensing Platforms for Aflatoxins Detection

by Atul Sharma, Kotagiri Yugender Goud, Akhtar Hayat, Sunil Bhand and Jean Louis Marty

Chemosensors 2017, 5(1), 1; https://doi.org/10.3390/chemosensors5010001 - 26 Dec 2016

Cited by 45 | Viewed by 9654

Abstract

Mycotoxin are small (MW ~700 Da), toxic secondary metabolites produced by fungal species that readily colonize crops and contaminate them at both pre- and post-harvesting. Among all, aflatoxins (AFs) are mycotoxins of major significance due to their presence in common food commodities and the potential threat to human health worldwide. Based on the severity of illness and increased incidences of AFs poisoning, a broad range of conventional and analytical detection techniques that could be useful and practical have already been reported. However, due to the variety of structural analogous of these toxins, it is impossible to use one common technique for their analysis. Numerous recent research efforts have been directed to explore alternative detection technologies. Recently, immunosensors and aptasensors have gained promising potential in the area of sample preparation and detection systems. These sensors offer the advantages of disposability, portability, miniaturization, and on-site analysis. In a typical design of an aptasensor, an aptamer (ssDNA or RNA) is used as a bio-recognition element either integrated within or in intimate association with the transducer surface. This review paper is focused on the recent advances in electrochemical immuno- and aptasensing platforms for detection of AFs in real samples. Full article

(This article belongs to the Special Issue Electrochemical Immunosensors and Aptasensors)

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14 pages, 1637 KB

Open AccessArticle

Titanium Dioxide Nanoparticles (TiO₂) Quenching Based Aptasensing Platform: Application to Ochratoxin A Detection

by Atul Sharma, Akhtar Hayat, Rupesh K. Mishra, Gaëlle Catanante, Sunil Bhand and Jean Louis Marty

Toxins 2015, 7(9), 3771-3784; https://doi.org/10.3390/toxins7093771 - 22 Sep 2015

Cited by 34 | Viewed by 9748

Abstract

We demonstrate for the first time, the development of titanium dioxide nanoparticles (TiO₂) quenching based aptasensing platform for detection of target molecules. TiO₂ quench the fluorescence of FAM-labeled aptamer (fluorescein labeled aptamer) upon the non-covalent adsorption of fluorescent labeled aptamer on TiO₂ surface. When OTA interacts with the aptamer, it induced aptamer G-quadruplex complex formation, weakens the interaction between FAM-labeled aptamer and TiO₂, resulting in fluorescence recovery. As a proof of concept, an assay was employed for detection of Ochratoxin A (OTA). At optimized experimental condition, the obtained limit of detection (LOD) was 1.5 nM with a good linearity in the range 1.5 nM to 1.0 µM for OTA. The obtained results showed the high selectivity of assay towards OTA without interference to structurally similar analogue Ochratoxin B (OTB). The developed aptamer assay was evaluated for detection of OTA in beer sample and recoveries were recorded in the range from 94.30%–99.20%. Analytical figures of the merits of the developed aptasensing platform confirmed its applicability to real samples analysis. However, this is a generic aptasensing platform and can be extended for detection of other toxins or target analyte. Full article

(This article belongs to the Collection Biorecognition Assays for Mycotoxins)

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13 pages, 306 KB

Open AccessArticle

A High-Throughput Enzyme Assay for Organophosphate Residues in Milk

by Rupesh K. Mishra, Kanchanmala Deshpande and Sunil Bhand

Sensors 2010, 10(12), 11274-11286; https://doi.org/10.3390/s101211274 - 9 Dec 2010

Cited by 15 | Viewed by 8979

Abstract

A rapid, high-sensitivity, chemiluminescence (CL) enzyme assay for the determination of organophosphate (OP) residues in milk is presented. The assay for quantification of OP residues in milk is based on the inhibition of enzyme butyrylcholinesterase (BuChE). BuChE was stabilized and preloaded in 384 well plates at 30 °C. The assay permits rapid determination of OPs in milk within 12 min including an incubation step. The enzyme assay was tested for individual and mixtures of OPs such as methyl paraoxon (MPOx), methyl parathion (MP) and malathion (MT) in milk to evaluate their synergistic effect on BuChE inhibition. Good linearity was obtained in the range 0.005–50 µg·L⁻¹ for MPOx and 0.5–1,000 µg·L⁻¹ for MP as well as MT in milk. Mean recovery of 93.2%–98.6% was obtained for MPOx spiked milk samples with 0.99%–1.67% reproducibility (RSD). The proposed method facilitated rapid screening of milk samples in 384 well plate formats with further miniaturization presented in 1,536 well plates. Full article

(This article belongs to the Section Biosensors)

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18 pages, 240 KB

Open AccessArticle

A High Sensitivity Micro Format Chemiluminescence Enzyme Inhibition Assay for Determination of Hg(II)

by Kanchanmala Deshpande, Rupesh K. Mishra and Sunil Bhand

Sensors 2010, 10(7), 6377-6394; https://doi.org/10.3390/s100706377 - 28 Jun 2010

Cited by 20 | Viewed by 11150

Abstract

A highly sensitive and specific enzyme inhibition assay based on alcohol oxidase (AlOx) and horseradish peroxidase (HRP) for determination of mercury Hg(II) in water samples has been presented. This article describes the optimization and miniaturization of an enzymatic assay using a chemiluminescence reaction. The analytical performance and detection limit for determination of Hg(II) was optimized in 96 well plates and further extended to 384 well plates with a 10-fold reduction in assay volume. Inhibition of the enzyme activity by dissolved Hg(II) was found to be linear in the range 5–500 pg^.mL⁻¹ with 3% CVin inter-batch assay. Due to miniaturization of assay in 384 well plates, Hg(II) was measurable as low as 1 pg^.mL⁻¹within15 min. About 10-fold more specificity of the developed assay for Hg(II) analysis was confirmed by challenging with interfering divalent metal ions such as cadmium Cd(II) and lead Pb(II). Using the proposed assay we could successfully demonstrate that in a composite mixture of Hg(II), Cd(II) and Pb(II), inhibition by each metal ion is significantly enhanced in the presence of the others. Applicability of the proposed assay for the determination of the Hg(II) in spiked drinking and sea water resulted in recoveries ranging from 100–110.52%. Full article

(This article belongs to the Section Chemical Sensors)

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