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1.
Anal Bioanal Chem ; 414(15): 4427-4439, 2022 Jun.
Article in English | MEDLINE | ID: mdl-35303136

ABSTRACT

Light-emitting nanoparticles like semiconductor nanocrystals (termed quantum dots, QDs) are promising candidates for biosensing and bioimaging applications based on their bright and stable photoluminescent properties. As high-quality QDs are often synthesized in organic solvents, strategies needed to be developed to render them water-dispersible without affecting their optical properties and prevent changes in postmodification steps like the biofunctionalization with antibodies or DNA. Despite a large number of studies on suitable surface modification procedures, the preparation of water-soluble QDs for nanobiotechnology applications still presents a challenge. To highlight the advantages of surface silanization, we systematically explored the influence of the core/multishell architecture of CdSe/CdS/ZnS QDs and the silanization conditions on the optical properties of the resulting silanized QDs. Our results show that the optical properties of silica-coated CdSe/CdS/ZnS QDs are best preserved in the presence of a thick CdS (6 monolayers (ML)) intermediate shell, providing a high photoluminescence quantum yield (PL QY), and a relatively thick ZnS (4.5 ML) external shell, effectively shielding the QDs from the chemical changes during silica coating. In addition to the QD core/shell architecture, other critical parameters of the silica-coating process, that can have an influence on the optical properties of the QD, include the choice of the surfactant and its concentration used for silica coating. The highest PL QY of about 46% was obtained by a microemulsion silica-coating procedure with the surfactant Brij L4, making these water-dispersible QDs to well-suited optical reporters in future applications like fluorescence immunoassays, biomedicine, and bioimaging.


Subject(s)
Cadmium Compounds , Quantum Dots , Selenium Compounds , Cadmium Compounds/chemistry , Quantum Dots/chemistry , Selenium Compounds/chemistry , Silicon Dioxide/chemistry , Sulfides/chemistry , Surface-Active Agents , Water/chemistry , Zinc Compounds/chemistry
2.
Sci Rep ; 10(1): 19668, 2020 11 12.
Article in English | MEDLINE | ID: mdl-33184321

ABSTRACT

Using a combination of experimental Raman, FTIR, UV-VIS absorption and emission data, together with the corresponding DFT calculations we propose the mechanism of modification of the folic acid specifically under the hydrothermal treatment at 200 °C. We established that folic acid breaks down into fragments while the pteridine moiety remains intact likely evolving into 6-formylpterin with the latter responsible for the increase in fluorescence emission at 450 nm. The results suggest that hydrothermal approach can be used for production of other purpose-engineered fluorophores.

3.
Colloids Surf B Biointerfaces ; 181: 533-538, 2019 Sep 01.
Article in English | MEDLINE | ID: mdl-31185445

ABSTRACT

A new fundamental concept for one-step in-situ functionalization of gold nanoparticles (GNPs) with folic acid using hydrothermal treatment is described. Hydrothermal treatment has been tuned to increase the light emission from the pterin moiety of folic acid molecule, while retain its structure and functionality, thus providing a simple route to multimodal tags for a variety of in vitro and in vivo biomedical applications. Successful functionalization of GNPs with the biological ligand is confirmed by specific binding with anti-folic acid antibody.


Subject(s)
Folic Acid/chemistry , Gold/chemistry , Metal Nanoparticles/chemistry , Temperature , Animals , Cattle , Immunoglobulin G/chemistry , Mice , Molecular Structure , Serum Albumin, Bovine/chemistry
4.
Sci Total Environ ; 656: 760-777, 2019 Mar 15.
Article in English | MEDLINE | ID: mdl-30530146

ABSTRACT

Air pollution is one of the leading causes of deaths in Southeast Asian countries including India. Exposure to air pollutants affects vital cellular mechanisms and is intimately linked with the etiology of a number of chronic diseases. Earlier work from our laboratory has shown that airborne particulate matter disturbs the mitochondrial machinery and causes significant damage to the epigenome. Mitochondrial reactive oxygen species possess the ability to trigger redox-sensitive signaling mechanisms and induce irreversible epigenomic changes. The electrophilic nature of reactive metabolites can directly result in deprotonation of cytosine at C-5 position or interfere with the DNA methyltransferases activity to cause alterations in DNA methylation. In addition, it also perturbs level of cellular metabolites critically involved in different epigenetic processes like acetylation and methylation of histone code and DNA hypo or hypermethylation. Interestingly, these modifications may persist through downstream generations and result in the transgenerational epigenomic inheritance. This phenomenon of subsequent transfer of epigenetic modifications is mainly associated with the germ cells and relies on the germline stability of the epigenetic states. Overall, the recent literature supports, and arguably strengthens, the contention that air pollution might contribute to transmission of epimutations from gametes to zygotes by involving mitochondrial DNA, parental allele imprinting, histone withholding and non-coding RNAs. However, larger prospective studies using innovative, integrated epigenome-wide metabolomic strategy are highly warranted to assess the air pollution induced transgenerational epigenetic inheritance and associated human health effects.


Subject(s)
Air Pollution/adverse effects , Epigenesis, Genetic/drug effects , Animals , DNA Methylation/drug effects , Humans
5.
Front Genet ; 9: 616, 2018.
Article in English | MEDLINE | ID: mdl-30574163

ABSTRACT

Lung cancer is the most frequently occurring malignancy and the leading cause of cancer-related death for men in our country. The only recommended screening method is clinic based low-dose computed tomography (also called a low-dose CT scan, or LDCT). However, the effect of LDCT on overall mortality observed in lung cancer patients is not statistically significant. Over-diagnosis, excessive cost, risks associated with radiation exposure, false positive results and delay in the commencement of the treatment procedure questions the use of LDCT as a reliable technique for population-based screening. Therefore, identification of minimal-invasive biomarkers able to detect malignancies at an early stage might be useful to reduce the disease burden. Circulating nucleic acids are emerging as important source of information for several chronic pathologies including lung cancer. Of these, circulating cell free miRNAs are reported to be closely associated with the clinical outcome of lung cancer patients. Smaller size, sequence homology between species, low concentration and stability are some of the major challenges involved in characterization and specific detection of miRNAs. To circumvent these problems, synthesis of a quantum dot based nano-biosensor might assist in sensitive, specific and cost-effective detection of differentially regulated miRNAs. The wide excitation and narrow emission spectra of these nanoparticles result in excellent fluorescent quantum yields with a broader color spectrum which make them ideal bio-entities for fluorescence resonance energy transfer (FRET) based detection for sequential or simultaneous study of multiple targets. In addition, photo-resistance and higher stability of these nanoparticles allows extensive exposure and offer state-of-the art sensitivity for miRNA targeting. A major obstacle for integrating QDs into clinical application is the QD-associated toxicity. However, the use of non-toxic shells along with surface modification not only overcomes the toxicity issues, but also increases the ability of QDs to quickly detect circulating cell free miRNAs in a non-invasive mode. The present review illustrates the importance of circulating miRNAs in lung cancer diagnosis and highlights the translational prospects of developing QD-based nano-biosensor for rapid early disease detection.

6.
Sci Rep ; 8(1): 16301, 2018 11 02.
Article in English | MEDLINE | ID: mdl-30390023

ABSTRACT

Carbon nanodots (CNDs) doped with Tb ions were synthesized using different synthetic routes: hydrothermal treatment of a solution containing carbon source (sodium dextran sulfate) and TbCl3; mixing of CNDs and TbCl3 solutions; freezing-induced loading of Tb and carbon-containing source into pores of CaCO3 microparticles followed by hydrothermal treatment. Binding of Tb ions to CNDs (Tb-CND coupling) was confirmed using size-exclusion chromatography and manifested itself through a decrease of the Tb photoluminescence lifetime signal. The shortest Tb photoluminescence lifetime was observed for samples obtained by hydrothermal synthesis of CaCO3 microparticles where Tb and carbon source were loaded into pores via the freezing-induced process. The same system displays an increase of Tb photoluminescence via energy transfer with excitation at 320-340 nm. Based on the obtained results, freezing-induced loading of cations into CNDs using porous CaCO3 microparticles as reactors is proposed to be a versatile route for the introduction of active components into CNDs. The obtained CNDs with long-lived emission may be used for time-resolved imaging and visualization in living biological samples where time-resolved and long-lived luminescence microscopy is required.

7.
Materials (Basel) ; 11(5)2018 May 05.
Article in English | MEDLINE | ID: mdl-29734729

ABSTRACT

A sensor based on microstructured waveguides (MWGs) with a hollow core inner surface covered with polyelectrolyte-layer-stabilized gold nanostars was developed for the SERS sensing of dissolved analytes. A polyelectrolyte-layer coating over the inner surface of glass cladding served as a spacer, reducing nonlinear optical effects in the glass near plasmonic hotspots of nanoparticles, as a stabilizing agent for thermodynamically unstable gold nanostars and as an optical coating for the fine-tuning of MWG bandgaps. This approach can be used to construct different kinds of SERS sensors for dissolved analytes, providing conservation, the prevention of coagulation, and the drying of a liquid sample for the time required to record the signal.

8.
Anal Chim Acta ; 1019: 14-24, 2018 Aug 17.
Article in English | MEDLINE | ID: mdl-29625680

ABSTRACT

This review covers the current state of the art of luminescent biosensors based on various types of microstructured optical fiber. The unique optical and structural properties of this type of optical fiber make them one of the most promising integrated platforms for bioassays. The individual sections of this review are devoted to a) classification of microstructured optical fibers, b) microstructured optical fiber materials, c) aspects of biosensing based on the biomolecules incorporated into the microstructured optical fibers, and d) development of models for prediction of the efficiency of luminescent signal processing. The authors' views on current trends and limitations of microstructured optical fibers for biosensing as well as the most promising areas and technologies for application in analytical practice are presented.


Subject(s)
Biosensing Techniques , Luminescence , Optical Fibers , Molecular Structure
9.
Mikrochim Acta ; 185(2): 94, 2018 01 10.
Article in English | MEDLINE | ID: mdl-29594559

ABSTRACT

A lateral flow immunoassay (LFIA) was developed for the determination of fumonisin mycotoxins. The fluorescence of CdSe/ZnS quantum dots (QDs), observed at excitation/emission wavelengths of 365/525 nm, is suppressed by the addition of silver nanoparticles (SNPs) or gold nanoparticles (GNPs) because SNPs overlap the excitation bands of the QDs, and GNPs overlap the emission bands. The fluorescence of the QDs is recovered upon addition of fumonisins, allowing for the sensitive detection in "positive mode" of the target mycotoxin by monitoring the changes of the QDs fluorescence intensity. The SNPs are found to be the most effective quenchers, while the use of GNPs allows for an efficient recovery of fluorescence and can be employed in the LFIA. The method was successfully applied to the fluorometric determination of fumonisins in spiked maize flour samples. The visual detection limit is at the ng·mL-1 level. This is four times lower compared to the colorimetric LFIA based on the use of the conventional gold NPs. Graphical abstract Schematic of the fluorescence quenching lateral flow immunoassay that uses fluorescent quantum dots (QD) and metal nanoparticles (NP) as the quencher: the binding of NP-labelled antibody to the antigen (purple triangle) modulates QD luminescence at the Test line, allowing for 'positive mode' detection of fumonisins. The NP accumulation at Control line assures validity of the test.


Subject(s)
Fluorescence , Fumonisins/analysis , Immunoassay/methods , Metal Nanoparticles/chemistry , Quantum Dots/chemistry , Cadmium Compounds , Gold , Immunoassay/standards , Limit of Detection , Mycotoxins/analysis , Selenium Compounds , Silver , Sulfides , Zea mays/microbiology , Zinc Compounds
10.
Langmuir ; 30(25): 7567-75, 2014 Jul 01.
Article in English | MEDLINE | ID: mdl-24892375

ABSTRACT

We report on the synthesis of core-shell CuInS2/ZnS quantum dots (QDs) in organic solution, their encapsulation with a PEG-containing amphiphilic polymer, and the application of the resulting water-soluble QDs as fluorescent label in quantitative immunoassay. By optimizing the methods for core synthesis and shell growth, CuInS2/ZnS QDs were obtained with a quantum yield of 50% on average after hydrophilization. After conjugation with an aflatoxin B1-protein derivative, the obtained QDs were used as fluorescent labels in microplate immunoassay for the quantitative determination of the mycotoxin aflatoxin B1. QDs-based immunoassay showed higher sensitivity compared to enzyme-based immunoassay.


Subject(s)
Copper/chemistry , Indium/chemistry , Quantum Dots , Zinc Compounds/chemistry , Hydrophobic and Hydrophilic Interactions , Immunoassay , Sulfides/chemistry
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