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1.
Anal Chim Acta ; 1178: 338804, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34482869

RESUMO

Gold nanoparticle (AuNP)-based colorimetric biosensors have been widely used for pH sensing and monitoring its changes. However, few AuNP-based pH sensors have been developed through the manipulation of the aggregation states of AuNPs via i-motif DNA. We herein report i-motif DNA-assisted pH-responsive gold nanoparticle assembly (termed RGA), which shows a reversible and highly sensitive response to pH variation between 6.20 and 7.40. The acidic pH triggers the disassembly of the RGA, thus converting the AuNPs from aggregation state to disperse state, which leads to a color transition from blue-purple to red. Therefore, the pH value can be estimated by naked-eye determination or UV-vis spectroscopy analysis. More significantly, the visually detectable color change is monitored using the built-in camera of a smartphone. The RGB (red, green, blue) values of the RGA solution are measured by a smartphone application (APP). Following data processing, the RGB values can be converted into pH value, providing a new strategy for the on-site and real-time pH sensing. Furthermore, the pH-induced conformation change of i-motif DNA allows the RGA to detect a slight pH fluctuation in the catalytic oxidation of glucose by glucose oxidase and the hydrolysis of urea by urease.


Assuntos
Ouro , Nanopartículas Metálicas , Colorimetria , Concentração de Íons de Hidrogênio , Smartphone
2.
Anal Chim Acta ; 1176: 338765, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34399900

RESUMO

Herein, we report a novel hairpin structure-mediated diagnostic method for the simple and rapid colorimetric detection of miRNA through the sensing of pyrophosphate. When the hairpin structure of the template DNA (h-Probe) was hybridized with the primer, the DNA primer extension mediated by nPfu special enzyme was blocked. However, this h-Probe was extended using nPfu special enzyme, upon the structural change of the template DNA, from a hairpin to a linear structure, in the presence of the target miRNA. The miRNA-hybridized template DNA sequence was cleaved by a duplex-specific nuclease (DSN), which cleaved the DNA from the RNA-DNA hybrid, thereby allowing the target miRNA to be recycled. Primer extension using nPfu special enzyme produced pyrophosphate when nucleotide triphosphate was incorporated into the DNA; this pyrophosphate was sensed in terms of a color change, from pink to colorless, when using pp Probe, a probe developed previously by our group. This novel system for the colorimetric detection of target miRNA operated with high sensitivity (LOD = 132 aM) and selectivity, with the whole detection process requiring only 30 min. Furthermore, this system could also detect miRNA fluorimetrically with similar sensitivity (LOD = 105 aM), highlighting the dual-sensing properties of pp Probe. This unique, extremely simple, and rapid system for the detection of miRNA through a highly sensitive color change would presumably be useful in applications requiring point-of-care detection.


Assuntos
Técnicas Biossensoriais , MicroRNAs , Colorimetria , DNA , Limite de Detecção , Técnicas de Amplificação de Ácido Nucleico
3.
Analyst ; 146(17): 5357-5361, 2021 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-34333580

RESUMO

Nitrogen doped carbon dots (N-CDs) were synthesized by a one-step hydrothermal method with dopamine and ethylenediamine. The as-prepared N-CDs were characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fluorescence spectrophotometer, UV-Vis spectrophotometry and Fourier transform infrared spectroscopy (FTIR). The average particle dimension of the as-prepared N-CDs was 2.68 nm, and the best excitation and emission wavelengths were 405 nm and 535 nm, separately. N-CDs exhibits excellent selectivity and sensitivity to detect the curcumin (Cur), attaining a wider linear range of 97.5 nM-67.9 µM and a limit of detection (LOD) of as low as 94 nM. Interestingly, N-CDs can also give responsive signals of a visible colour change (yellow to red). Moreover, a novel fluorescent/colorimetric dual-mode method has been successfully employed for the determination of Cur in real samples with good recoveries (94%-110%) and precision (RSD = 0.3-2.9%).


Assuntos
Curcumina , Pontos Quânticos , Carbono , Colorimetria , Corantes Fluorescentes , Nitrogênio , Espectrometria de Fluorescência
4.
Sensors (Basel) ; 21(16)2021 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-34450980

RESUMO

Copper (II) ions have been shown to greatly improve the chemical stability and peroxidase-like activity of gold nanoclusters (AuNCs). Since the affinity between Cu2+ and pyrophosphate (PPi) is higher than that between Cu2+ and AuNCs, the catalytic activity of AuNCs-Cu2+ decreases with the introduction of PPi. Based on this principle, a new colorimetric detection method of PPi with high sensitivity and selectivity was developed by using AuNCs-Cu2+ as a probe. Under optimized conditions, the detection limit of PPi was 0.49 nM with a linear range of 0.51 to 30,000 nM. The sensitivity of the method was three orders of magnitude higher than that of a fluorescence method using AuNCs-Cu2+ as the probe. Finally, the AuNCs-Cu2+ system was successfully applied to directly determine the concentration of PPi in human urine samples.


Assuntos
Ouro , Nanopartículas Metálicas , Colorimetria , Cobre , Difosfatos , Corantes Fluorescentes , Humanos , Limite de Detecção , Peroxidase , Peroxidases , Espectrometria de Fluorescência
5.
ACS Appl Mater Interfaces ; 13(33): 38931-38946, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34374513

RESUMO

With the continuous development of DNA nanotechnology, various spatial DNA structures and assembly techniques emerge. Hybridization chain reaction (HCR) is a typical example with exciting features and bright prospects in biosensing, which has been intensively investigated in the past decade. In this Spotlight on Applications, we summarize the assembly principles of conventional HCR and some novel forms of linear/nonlinear HCR. With advantages like great assembly kinetics, facile operation, and an enzyme-free and isothermal reaction, these strategies can be integrated with most mainstream reporters (e.g., fluorescence, electrochemistry, and colorimetry) for the ultrasensitive detection of abundant targets. Particularly, we select several representative studies to better illustrate the novel ideas and performances of HCR strategies. Theoretical and practical utilities are confirmed for a range of biosensing applications. In the end, a deep discussion is provided about the challenges and future tasks of this field.


Assuntos
DNA/química , Técnicas Biossensoriais , Colorimetria , Técnicas Eletroquímicas , Humanos , Nanopartículas/química , Técnicas de Amplificação de Ácido Nucleico/métodos , Conformação de Ácido Nucleico , Hibridização de Ácido Nucleico/métodos , Sensibilidade e Especificidade , Espectrometria de Fluorescência
6.
ACS Appl Mater Interfaces ; 13(33): 39719-39729, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34392680

RESUMO

In this work, cucurbiturils (CBs), a class of macrocyclic supramolecules, were observed to have an interesting peroxidase-like activity, which is metal-free, substrate-specific, thermophilic, acidophilic, and insensitive to ionic strength. By coating CBs on enzyme-encapsulated zeolitic imidazolate framework-8 (ZIF-8), a composite nanozyme was constructed, which retains the catalytic ability of CBs and enzymes and makes them cascade. On addition of the substrate, i.e., the detection target, a highly efficient cascade catalysis can be launched in all the spatial directions to generate sensitive and visible signals. Convenient detection of glucose and cholesterol as models is thereby achieved. More importantly, we have also successfully constructed a composite nanozyme-based sensor array (6 × 8 wells) and thereby achieved simultaneous colorimetric analysis of multiple samples. The concept and successful practice of the construction of the unique core-shell supramolecule/biomolecule@nanomaterial architecture provide the possibility to fabricate next-generation multifunctional materials and create new applications by integrating their unique functions.


Assuntos
Hidrocarbonetos Aromáticos com Pontes/química , Imidazóis/química , Nanocompostos/química , Peroxidases/química , Zeolitas/química , Técnicas Biossensoriais , Hidrocarbonetos Aromáticos com Pontes/metabolismo , Catálise , Colorimetria , Corantes Fluorescentes/química , Glucose Oxidase/química , Glucose Oxidase/metabolismo , Peróxido de Hidrogênio/química , Imidazóis/metabolismo , Simulação de Acoplamento Molecular , Oxirredução , Peroxidases/metabolismo , Impressão Tridimensional
7.
Talanta ; 234: 122645, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364454

RESUMO

In view of the broad application prospect of peroxidase-like nanozymes in biomedical analysis, it is of great significance to eliminate the interference of their oxidase-like activity and enable them to work under neutral conditions. Herein, flower-like NiV2O6 was synthesized and their enzyme-mimicking activity was investigated. Through the regulation of pH, NiV2O6 nanozyme showed only peroxidase-like activity but not oxidase-like activity under neutral conditions, which could catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine into its blue product in the presence of H2O2. Furthermore, based on the competitive effect of glutathione (GSH) on the catalytic activity of nanozymes, a semi-quantitative/quantitative colorimetric assay was established for GSH detection by using peroxidase-like NiV2O6. The assay exhibited a good linear relationship in GSH concentration ranging from 3-100 µmol L-1, with a detection limit of 0.89 µmol L-1. Moreover, in the presence of formaldehyde as masking agent, this method showed satisfactory specificity for GSH under the interference of a variety of interfering substances and even biothiols. Concerning the practical application, the system was applied to monitor GSH level in fetal bovine serum, human serum and SiHa cells. Satisfyingly, the obtained results were consistent well with those of Ultra performance liquid chromatography (UPLC) and assay kit, indicating the constructed assay has great potential in clinical application.


Assuntos
Glutationa , Peróxido de Hidrogênio , Colorimetria , Humanos , Concentração de Íons de Hidrogênio , Peroxidase , Peroxidases
8.
Talanta ; 234: 122647, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364456

RESUMO

Nanozymes, as a new type of artificial enzyme, have recently become a research hotspot in the field of catalysis and biomedicine. However, the application of nanozyme is limited by catalytic activity changes of different substrates and low specificity. This work shows that citrate-capped platinum nanoparticles (Cit-PtNPs) exhibit stronger oxidase-like activity than other platinum nanozymes at different pH when 3-methyl-2-benzothiazolinonehydrazone hydrochloride (MBTH) and n-ethyl-n- (2-hydroxy-3-sulfopropyl)-m-toluidine sodium salt (TOOS) were used as chromogenic substrates. This phenomenon has important reference value for different nanozymes to choose chromogenic substrates in catalysis. In MBTH-TOOS chromogenic system, MBTH (-NH) radical is first produced during the reaction through catalytic oxidation of Cit-PtNPs, which reacts with TOOS to produce a colorless compound. The blue-purple quinoid dye was produced through the dismutation of the colorless compound. The catalytic mechanism of the oxidase-like activity of Cit-PtNPs is that two-electron reduction process and four-electron reduction process are simultaneously carried out in the catalytic process. Furthermore, to solve the problem of low specificity of metal nanozymes, protamine is designed as aggregation promoter of Cit-PtNPs and the specifichydrolysis substrate of trypsin. In this work, it can achieve one-step detection of trypsin by the boosting oxidase activity of Cit-PtNPs at pH8. The catalytic activity of Cit-PtNPs is proportional to the concentration of trypsin. The linear range for trypsin is 1.0-70.0 ngmL-1 and the limit of detection is measured to be 0.6 ngmL-1. This novel method has also been successfully applied to the detection of inhibitors and trypsin in urine samples.


Assuntos
Nanopartículas Metálicas , Platina , Catálise , Colorimetria , Oxirredutases , Sódio , Tripsina
9.
Talanta ; 234: 122655, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364464

RESUMO

Hypochlorous acid (HClO) as well as its ionic form (ClO-), representative of reactive oxygen species (ROS), are essential players in all sorts of biological processes. The abnormal level of each can lead to the onset of various diseases. Besides, Sodium hypochlorite, a commonly-used bleaching agent in our daily lives, could also result in breathing and skin problems when overexposed. Therefore, developing a molecular chemosensor for sensing HClO is of biological and environmental importance. Though many such chemosensors have been reported, new HClO chemosensors with different sensing performances may still come in handy in certain situations. In this work, we have developed a new coumarin-based chemosensor, CM-hbt, for realizing both ratiometric and colorimetric imaging detection of HClO in live cells. Notably, we further explored its application in sensing HClO in plant mung beans as well as fabricated an easy-to-use paper strip apparatus for facilitating its quick detection, which is seldomly seen in other HClO chemosensors. All the analysis results confirmed the high sensitivity and selectivity of this novel chemosensor. DFT calculations were used to decipher the underlying sensing mechanism of CM-hbt. Overall, this work presents a novel chemosensor, CM-hbt, as a colorimetric and ratiometric chemosensor for realizing imaging detection of HClO in a variety of different model systems, which highlights its broad spectrum of application potentials.


Assuntos
Colorimetria , Vigna , Corantes Fluorescentes , Ácido Hipocloroso , Imagem Óptica
10.
Talanta ; 234: 122675, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364475

RESUMO

Hepatitis B virus (HBV) infection is one of the global healthcare burdens, and its early diagnosis is crucial for the prevention of HBV-induced chronic hepatitis, liver fibrosis, cirrhosis, and hepatocellular carcinoma. Although different detection approaches have been reported, most of these methods either rely on sophisticated machines or procedures, which limit their use particularly in the high endemic, developing countries. In this work, we report a dual-sensing nanoplatform built on noble metal-molybdenum disulfide (MoS2) nanohybrids, and this platform can detect the HBV DNA target through either fluorometric or colorimetric readouts. The design with the silver nanocluster (AgNC)-MoS2 nanohybrid enables multiplex fluorescent detection, while the HBV DNA-regulated growth of platinum nanoparticles (PtNPs) on the MoS2 nanosheets offers signal-on colorimetric detection. Both AgNC-MoS2 and PtNP-MoS2 nanohybrids show high sensitivity with pico-molar detection limit and single nucleotide specificity, even with the spiked human serum. Collectively, the proposed nanohybrids possess their potential in the use of early HBV diagnosis, particularly suitable for the high endemic areas with limited medical and instrumental supports.


Assuntos
Técnicas Biossensoriais , Nanopartículas Metálicas , Colorimetria , DNA , Dissulfetos , Vírus da Hepatite B/genética , Humanos , Limite de Detecção , Molibdênio , Platina
11.
Talanta ; 234: 122681, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364481

RESUMO

Hypoxia refers to the lack of oxygen supply to cells or tissues. The overexpression of nitroreductase has been shown to be closely related to the degree of hypoxia, which leads to the level of nitroreductase (NTR) being used as an indicator of hypoxia. We reported a facile visual detection of NTR based on the aggregation of gold and silver alloy nanoparticles. Compared with gold nanoparticles (AuNPs), the aggregation behavior of Au80Ag20 NPs caused a more prominent color change. Copper ions (Cu2+) can be rapidly reduced by nicotinamide adenine dinucleotide (NADH) under the catalysis of Au80Ag20 NPs. But NADH is consumed as an electron donor during the catalytic reduction reaction of p-nitrophenol (pNP) by NTR. A decrease of NADH amount results in the aggregation of Au80Ag20 NPs by the excess Cu2+ and different aggregation degrees of Au80Ag20 NPs lead to observable color change. A linear correlation of A600/A505 = 0.0285 [NTR]+0.361 (R2 = 0.980) was obtained with a limit of detection (LOD) of 0.23 µg/mL for UV-vis spectrophotometer. For visual detection, the values of R/B against the concentration of NTR obtains a calibration curve of R/B = -0.031 [NTR]+ 1.54 (R2 = 0.985) with a LOD of 0.76 µg/mL, which is of the same order of magnitude as the UV-vis spectrophotometer analysis. As a comparison, Au80Ag20 NPs was replaced by several different composition nanoparticles (Au NPs, Au70Ag30 NPs, Au50Ag50 NPs) to be a chromogenic substrate, and the results suggest the Au80Ag20 NPs is the most sensitive substrate in our assay. Selectivity tests showed that the detection system did not respond to other common substances, and the reaction mechanism was verified by inhibitor research. Finally, the assay was used on the human serum samples with spiking NTR, and the recovery rates of this assay with UV-vis spectrophotometer were basically consistent with RGB analysis.


Assuntos
Nanopartículas Metálicas , Prata , Ligas , Colorimetria , Cobre , Ouro , Ligas de Ouro , Humanos , Íons , NAD , Nitrorredutases
12.
Talanta ; 234: 122706, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34364501

RESUMO

Biogenic amines (BAs) are not only well-known indicators for food freshness but can cause serious harm to the body after excessive consumption, which makes the determination of its content in food of great significance. In this work, a simple and convenient method for colorimetric detection of BAs was developed based on the sensitivity of the polymerization of dopamine to the presence of BAs on the surface of gold nanoparticles (AuNPs). Taking histamine as a representative, the system exhibited a distinct color change from wine red to black among the amine concentration of 1-100 µg/mL with the detection limit of 2.8 µg/mL. The detection system also exhibited sensitivity to other common kinds of BAs, such as putrescine, cadaverine, spermine, spermidine, tyramine, and tryptamine. Moreover, the proposed method showed encouraging performance in visual detection of the freshness of real samples, which provided a new approach for food quality and freshness evaluation.


Assuntos
Ouro , Nanopartículas Metálicas , Aminas Biogênicas , Colorimetria , Dopamina , Polimerização
13.
Anal Chem ; 93(33): 11424-11432, 2021 08 24.
Artigo em Inglês | MEDLINE | ID: mdl-34378906

RESUMO

Enzyme-linked immunosorbent assays (ELISA), as one of the most used immunoassays, have been conducted ubiquitously in hospitals, research laboratories, etc. However, the conventional ELISA procedure is usually laborious, occupies bulky instruments, consumes lengthy operation time, and relies considerably on the skills of technicians, and such limitations call for innovations to develop a fully automated ELISA platform. In this paper, we have presented a system incorporating a robotic-microfluidic interface (RoMI) and a modular hybrid microfluidic chip that embeds a highly sensitive nanofibrous membrane, referred to as the Robotic ELISA, to achieve human-free sample-to-answer ELISA tests in a fully programmable and automated manner. It carries out multiple bioanalytical procedures to replace the manual steps involved in classic ELISA operations, including the pneumatically driven high-precision pipetting, efficient mixing and enrichment enabled by back-and-forth flows, washing, and integrated machine vision for colorimetric readout. The Robotic ELISA platform has achieved a low limit of detection of 0.1 ng/mL in the detection of a low sample volume (15 µL) of chloramphenicol within 20 min without human intervention, which is significantly faster than that of the conventional ELISA procedure. Benefiting from its modular design and automated operations, the Robotic ELISA platform has great potential to be deployed for a broad range of detections in various resource-limited settings or high-risk environments, where human involvement needs to be minimized while the testing timeliness, consistency, and sensitivity are all desired.


Assuntos
Técnicas Analíticas Microfluídicas , Procedimentos Cirúrgicos Robóticos , Colorimetria , Ensaio de Imunoadsorção Enzimática , Humanos , Imunoensaio , Microfluídica
14.
Molecules ; 26(16)2021 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-34443603

RESUMO

Abnormal levels of reduced glutathione (GSH) and glutathione reductase (GR) are usually related to a variety of diseases, so it is of great significance to determine the GSH concentration and GR activity. We herein develop a smartphone-assisted colorimetric biosensor for the detection of GSH and GR activity in human serum and mouse liver using hemin/G-quadruplex DNAzyme. Firstly, an obvious color change from colorless to green can be observed, owing to the high peroxidase-like activity of hemin/G-quadruplex DNAzyme toward 2,2'-azino-bis(3-ethylbenzothiozoline-6-sulfonic acid) (ABTS). With the addition of GSH or GR, the H2O2-mediated oxidation of ABTS catalyzed by hemin/G-quadruplex DNAzyme is significantly inhibited, resulting in remarkable color fading. Therefore, the detection of GSH and GR activity can be achieved by observing the color transition or measuring the absorbance at 420 nm. The detection limit was estimated to be as low as 0.1 µM and 10 µU/mL for GSH and GR, respectively. More interestingly, the RGB values of the sensing system can be identified by the smartphone application (APP, color collect), which makes it an ideal format for on-site determination and point-of-care testing (POCT). In addition, the proposed method shows excellent selectivity and acceptable applicability for the determination of GSH concentration and GR activity in human serum samples and mouse liver tissues, which might hold great application potential in clinical diagnosis and drug screening.


Assuntos
Técnicas Biossensoriais/métodos , DNA Catalítico/metabolismo , Glutationa Redutase/sangue , Glutationa/sangue , Hemina/metabolismo , Fígado/metabolismo , Smartphone , Animais , Colorimetria , DNA Catalítico/química , Quadruplex G , Glutationa/metabolismo , Glutationa Redutase/metabolismo , Humanos , Camundongos , Oxirredução
15.
Sci Rep ; 11(1): 16430, 2021 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-34385527

RESUMO

Until there is an effective implementation of COVID-19 vaccination program, a robust testing strategy, along with prevention measures, will continue to be the most viable way to control disease spread. Such a strategy should rely on disparate diagnostic tests to prevent a slowdown in testing due to lack of materials and reagents imposed by supply chain problems, which happened at the beginning of the pandemic. In this study, we have established a single-tube test based on RT-LAMP that enables the visual detection of less than 100 viral genome copies of SARS-CoV-2 within 30 min. We benchmarked the assay against the gold standard test for COVID-19 diagnosis, RT-PCR, using 177 nasopharyngeal RNA samples. For viral loads above 100 copies, the RT-LAMP assay had a sensitivity of 100% and a specificity of 96.1%. Additionally, we set up a RNA extraction-free RT-LAMP test capable of detecting SARS-CoV-2 directly from saliva samples, albeit with lower sensitivity. The saliva was self-collected and the collection tube remained closed until inactivation, thereby ensuring the protection of the testing personnel. As expected, RNA extraction from saliva samples increased the sensitivity of the test. To lower the costs associated with RNA extraction, we performed this step using an alternative protocol that uses plasmid DNA extraction columns. We also produced the enzymes needed for the assay and established an in-house-made RT-LAMP test independent of specific distribution channels. Finally, we developed a new colorimetric method that allowed the detection of LAMP products by the visualization of an evident color shift, regardless of the reaction pH.


Assuntos
Teste para COVID-19/métodos , COVID-19/virologia , Colorimetria/métodos , Técnicas de Diagnóstico Molecular/métodos , Técnicas de Amplificação de Ácido Nucleico/métodos , SARS-CoV-2/isolamento & purificação , COVID-19/diagnóstico , Humanos , Pandemias , Portugal/epidemiologia , RNA Viral/genética , SARS-CoV-2/genética , Saliva/química , Saliva/virologia , Sensibilidade e Especificidade
16.
Analyst ; 146(16): 5074-5080, 2021 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-34318784

RESUMO

Diabetes mellitus has received much attention because its complications include liver, kidney, eye, heart and cerebrovascular diseases. Thus, it would be highly significant to develop a rapid and efficient method for glucose detection in biological samples. In this work, a point-of-care testing (POCT) method of glucose detection was proposed using a standard colorimetric card for semi-quantitative determination patterns. In the prepared fluorescence color card for glucose, a good linear relationship was acquired by plotting the ratio of the grayscale value (I/I0) versus the logarithm of glucose concentration within 100.0 to 1000.0 µmol L-1, and the LOD of glucose detection was 1.1 µmol L-1. A large number of actual samples (30 serum and 7 urine) were analyzed and the results demonstrated that this method had good potential to be applied in the primary screening of diabetic patients. In addition, this method is universal and can be applied in the simultaneous detection of multiple small molecules. It provides a new strategy for the primary screening of multiple diseases simultaneously, which presents excellent application potential.


Assuntos
Diabetes Mellitus , Testes Imediatos , Colorimetria , Diabetes Mellitus/diagnóstico , Glucose , Humanos , Sistemas Automatizados de Assistência Junto ao Leito
17.
Anal Methods ; 13(30): 3348-3358, 2021 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-34286735

RESUMO

In this research, the pH differential method was explored for the first time using a mobile phone as a detector, replacing UV-Vis spectrophotometry. A smartphone digital image colorimetric (SDIC) system was developed for the determination of the total monomeric anthocyanin content in black rice grains using colour values. The change in colour of anthocyanin cyanidin-3-glucoside (C3G) at pH 1.0 and pH 4.5 was investigated and described through colour model systems (RGB and CIELAB). Under optimum conditions, the quantitative method based on the chroma difference, was able to quantify the total amount of monomeric anthocyanins with a linear correlation (R2 = 0.989) to that of UV-Vis spectrophotometry and high performance liquid chromatography (HPLC) (reference method). The SDIC system displayed good precision (≤1.88% RSD) and a low detection limit (2.2 ± 0.1 µg g-1). The validated results demonstrated that the developed method was a cost-effective alternative for the quantitation of anthocyanins. In addition, the effect of six mineral elements on black rice cultivation was investigated. The results showed that the addition of the Ca fertiliser resulted in black rice grains with an anthocyanin content 2-fold higher than that of the control with a significant difference (p < 0.05).


Assuntos
Antocianinas , Oryza , Colorimetria , Concentração de Íons de Hidrogênio , Smartphone
18.
J Nanosci Nanotechnol ; 21(12): 6094-6100, 2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34229809

RESUMO

In this article, we propose high-performance colorimetric detection of Hg+2 using silver nanoprisms. The spherical and triangular AgNPs were synthesized using varied concentration of NaBH4. Pristine AgNPs without any further modification were used for the detection of various metal ions including Hg2+, Pb2+, Cl-, Cd2+, Co2+, Cu2+, Ba2+, Pb2+, Cr3+, Cr2O2-7 , Fe2+, Fe3+ etc. AgNPs were not only selective in detecting the ions of Cl- and Hg+2 ions but also highly sensitive. Minimum detection limit was observed to be as low as 10-7 ppm for both Hg+2 and Cl-. Water samples collected from various locations detected for the presence of various heavy metals. Silver nanoprisms owing to their surface plasmon resonance exhibit highly selective tendency towards detection against Hg+2.


Assuntos
Mercúrio , Nanopartículas Metálicas , Colorimetria , Íons , Prata
19.
Analyst ; 146(15): 4848-4857, 2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34231560

RESUMO

A colorimetric aptasensor for chlorpyrifos detection utilizing the localized surface plasmon resonance (LSPR) of gold nanoparticle (AuNP) aggregates coupling with a specific aptamer and cationic polyethyleneimine (PEI) has been developed. The measurement principle is based on a remarkable characteristic of AuNPs that can change their colors under the aggregation and dispersion conditions, which enables a sensitive colorimetric detection. In the absence of chlorpyrifos, negatively charged phosphate backbones of the aptamer potentially interact with the cationic PEI, resulting in the red color appearance of the dispersed AuNPs, whereas, in the presence of chlorpyrifos, the aptamer binds explicitly to chlorpyrifos, consequently releasing cationic PEI. Uninteracted PEI induces AuNP aggregation, causing a color change from red to blue that can be observed through the naked eye. Under the optimized conditions, 6 nM PEI, 10 nM aptamer, and a pH buffer of 7.5, the colorimetric aptasensor gives a linear response in the range of 20-300 ng mL-1 with a low detection limit of 7.4 ng mL-1. The developed method has been successfully applied to complex sample analysis. The accuracy and precision of chlorpyrifos quantification in spiked samples, including tap water, pomelo, and longan samples, are in the acceptable criteria of method validation, indicating that the developed aptasensor can be utilized as an alternative analytical tool for chlorpyrifos determination in complex samples. This aptasensor provides advantages such as a simple procedure, low cost, short analysis time, and involving uncomplicated instruments. Moreover, it offers high sensitivity, selectivity, and stability.


Assuntos
Aptâmeros de Nucleotídeos , Técnicas Biossensoriais , Clorpirifos , Nanopartículas Metálicas , Colorimetria , Ouro , Polietilenoimina
20.
Analyst ; 146(15): 4767-4774, 2021 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-34231566

RESUMO

Molecular diagnosis of viral genotyping devoid of polymerase chain reaction (PCR) amplification in clinical cohorts has hitherto been challenging. Here we present a simplified molecular diagnostic strategy for direct genotyping of hepatitis C virus (HCV) 1 and 3 (prevalent worldwide) using a combination of rationally designed genotype-specific antisense oligonucleotides (ASOs) and plasmonic gold nanoparticles. The ASOs specific to genotypes 1 and 3 have been designed from the nonstructural region 5A (NS5A) of the viral genome using the ClustalW multiple sequence alignment tool. A total of 79 clinical samples including 18 HCV genotype 1, 18 HCV genotype 3, one HIV positive, one HBV positive, and 41 healthy controls have been tested against both the designed ASOs. The study reveals 100% specificity and sensitivity with the employed samples and thereby opens up new avenues for PCR-free direct genotyping of other viruses as well, through the rational design of ASOs.


Assuntos
Hepatite C , Nanopartículas Metálicas , Colorimetria , Genótipo , Ouro , Hepacivirus/genética , Hepatite C/diagnóstico , Humanos , Oligonucleotídeos Antissenso , Reação em Cadeia da Polimerase , RNA Viral/genética
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