A simple colorimetric detection of melamine was studied using 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) citrate-capped gold nanoparticles (AuNPs).

Amitava Mukherjee

Centre for Nanobiotechnology

Vellore Campus

Chandra Sekaran N

Paul I.E

Rajeshwari A

Prathna T.C

Raichur A.M

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Analytical Methods

In the current study, we emphasize that osteopontin is overexpressed in oral squamous cell carcinoma. Overexpression of osteopontin levels was confirmed by mRNA quantification studies and immunohistochemistry analysis. Based on this, a gold nanoparticle–based ELISA system was developed for non-invasive osteopontin detection. The incorporation of AuNRs (Gold nanorods) or AuNSs (Gold nanospheres) in the conventional ELISA improved the sensitivity of analyses. A considerably lowered detection limit in case of AuNR (detection limit: 0.02 ng mL− 1) and AuNS (detection limit: 0.03 ng mL− 1) modified assay was obtained as compared to commercially available OPN ELISA kit (detection limit: 0.14 ng mL− 1). The modified ELISA had a wide linear detection range (0.31–20 ng mL− 1), good reproducibility, and specificity against the tested interferents in the saliva. Finally, the nanoELISA was validated with osteopontin spiked in artificial and normal saliva samples and observed to show good recovery (95.4–97.85%), which indicates the application potential of the developed kit for real sample analysis. © 2017 Elsevier B.V.

Clinica Chimica Acta

A facile gold nanoparticle–based ELISA system for detection of osteopontin in saliva: Towards oral cancer diagnostics

Gold nanorods (AuNRs) have distinctive opto-electronic properties, which facilitate their exploitation in various fields, especially biology and medicine. However, their interaction with the biomolecules in the physiological system can cause the formation of a protein corona, composing of a soft and hard layer, which ultimately alters the physiochemical properties, toxicity, and fate of the nanoparticles. Thus, the formation and composition of protein corona on three differently functionalized AuNRs [CTAB-AuNRs (positive), PEG-AuNRs (neutral), PSS-AuNRs (negative)] were studied for the three most abundant proteins in the blood serum namely, human serum albumin, immunoglobulin tG, and transferrin. The variation in protein adsorption, mean hydrodynamic size, and zeta potential were studied for different protein incubation periods (0, 0.5, 1, 4, 8, 12, and 24 h). The soft and hard corona layers were estimated for the individual proteins and mixture of the three proteins at the time point of maximum protein adsorption (1 h). Finally, in order to study the biological consequence of the coronation of AuNRs, the cell viability and uptake of AuNRs before and after protein corona formation were studied. The formation of IgG corona helped to reduce cellular toxicity, and at the same time, showed improved cell uptake when compared to the respective as-prepared AuNRs, highlighting their application potential for drug delivery applications. © 2017 Elsevier B.V.

Journal of Molecular Liquids

Impact of gold nanorod functionalization on biocorona formation and their biological implication

Gold nanorods (AuNRs) used for biomedical applications could be encountered by biomolecules in the bloodstream, of which IgG is the most abundant antibody. With a view to mitigate their side effect on encountered proteins, the effect of Au concentration (5–40 μM) and functionalization (CTAB-positive;PSS-negative; PEG-neutral) of AuNRs was investigated on the stability of a model protein, IgG (1 μM). Electron microscopic images and particle size analyses indicated least aggregation behavior for PEG-AuNRs, which can be correlated to their neutral charge (from zeta potential analyses) or stearic hindrance of PEG chains. Variations in tryptophan domain were probed by UV–visible absorption and fluorescence quenching studies. Synchronous fluorescence study helped to provide information regarding variations in the hydrophobic region of IgG. The denaturation studies also indicated the stability of AuNR–IgG complex formation. These studies showed that positively charged IgG (pI: 7.8 ± 1.0) was mostly affected by negatively charged PSS-AuNRs and least affected by PEG-AuNRs. This was verified by secondary structural investigations performed using CD and FTIR spectroscopy. For cytotoxicity studies on human lymphocytes, CTAB-AuNRs are known to show higher toxicity compared to PSS-AuNRs and PEG-AuNRs (least). Though PSS-functionalized AuNRs were shown to affect cells to a lesser degree based on the negative charge of cell membrane, they could hamper with positively charged biomolecules in the bloodstream before they reach the target, which must also be considered for choosing the right AuNR functionalization. Thus, this work indicates the effect of different AuNR functionalization on protein and cellular toxicity and stresses the necessity to use neutral particles to mitigate their side effect for theranostic applications. © 2016 Elsevier B.V.

Materials Science and Engineering: C

Significance of surface functionalization of Gold Nanorods for reduced effect on IgG stability and minimization of cytotoxicity

Nanobiosensors

Detection of food contaminants by gold and silver nanoparticles

A comparative study on detection of melamine with different sized citrate capped AuNPs namely 15 nm (AuNPs-I), 30 nm (AuNPs-II), and 40 nm (AuNPs-III) was carried out by fluorescence spectroscopy. The AuNPs emitted strong fluorescence at 421 nm with different intensity at 116.122, 220.511 and 253.665 for AuNPs-I, AuNPs-II and AuNPs-III respectively on excitation with 308 nm. On interaction with melamine, the AuNPs aggregated resulting in the enhancement of the fluorescent intensity of AuNPs. The sensitivity of melamine detection was studied for three different sizes of AuNPs by drawing a calibration curve between the concentration of melamine and fluorescence intensity. A good sensitivity was observed for AuNPs-II having the detection limit as low as 0.66 nM (3σ) which was lower in comparison to the detection limit of AuNPs-I (2.78 nM) and AuNPs-III (7.74 nM). The cost of synthesis was low as the usage of HAuCl4 in the synthesis of AuNPs-II was lower compared to the other sizes of AuNPs resulting in low cost of chemicals. The AuNPs-II was further chosen for carrying out selectivity study and for detecting the concentration of melamine. The recovery percentage of melamine in raw milk, liquid milk and milk powder after pre-treatment was found to be 100 %, 97 % to 100 % and 94 % to 99 % respectively. © 2016, Springer Science+Business Media New York.

Journal of Fluorescence

Fluorescence Based Study for Melamine Detection Using Gold Colloidal Solutions

Biosensors and Bioelectronics

Visual detection of melamine based on the peroxidase-like activity enhancement of bare gold nanoparticles

Food Chemistry

Colorimetric sensor based on dual-functional gold nanoparticles: Analyte-recognition and peroxidase-like activity

Food Analytical Methods

A Rapid Colorimetric Detection of Melamine in Raw Milk by Unmodified Gold Nanoparticles

Size-dependent colorimetric visual detection of melamine in milk at 10 ppb level by citrate-stabilized Au nanoparticles

The Analyst

Bare gold nanoparticles as facile and sensitive colorimetric probe for melamine detection

Colorimetric detection of melamine based on the size effect of AuNPs

Journal	Data powered by TypesetAnalytical Methods
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	1759-9660
Open Access	0