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Determination of underivatized long chain fatty acids using RP-HPLC with capacitively coupled contactless conductivity detection

Makahleh A, Saad B, Siang GH, Saleh MI, Osman H, Salleh B

Talanta, 2010 Apr 15;81(1-2):20-4.
PMID: 20188881 DOI: 10.1016/j.talanta.2009.11.030

A reversed-phase high-performance liquid chromatographic method with capacitively coupled contactless conductivity detector (C(4)D) has been developed for the separation and the simultaneous determination of five underivatized long chain fatty acids (FAs), namely myristic, palmitic, stearic, oleic, and linoleic acids. An isocratic elution mode using methanol/1mM sodium acetate (78:22, v/v) as mobile phase with a flow rate of 0.6 mL min(-1) was used. The separation was effected by using a Hypersil ODS C(18) analytical column (250 mm x 4.6 mm x 5 microm) and was operated at 45 degrees C. Calibration curves of the five FAs were well correlated (r(2)>0.999) within the range of 5- 200 microg mL(-1) for stearic acid, and 2-200 microg mL(-1) for the other FAs. The proposed method was tested on four vegetable oils, i.e., pumpkin, soybean, rice bran and palm olein oils; good agreement was found with the standard gas chromatographic (GC) method. The proposed method offers distinct advantages over the official GC method, especially in terms of simplicity, faster separation times and sensitivity.

Matched MeSH terms: Limit of Detection
Polysilicon nanogap lab-on-chip facilitates multiplex analyses with single analyte

Balakrishnan SR, Hashim U, Gopinath SC, Poopalan P, Ramayya HR, Veeradasan P, et al.

Biosens Bioelectron, 2016 Oct 15;84:44-52.
PMID: 26560969 DOI: 10.1016/j.bios.2015.10.075

Rationally designed biosensing system supports multiplex analyses is warranted for medical diagnosis to determine the level of analyte interaction. The chemically functionalized novel multi-electrode polysilicon nanogap (PSNG) lab-on-chip is designed in this study, facilitates multiplex analyses for a single analyte. On the fabricated 69nm PSNG, biocompatibility and structural characteristics were verified for the efficient binding of Human Chorionic Gonadotropin (hCG). With the assistance of microfluidics, hCG sample was delivered via single-injection to 3-Aminopropyl(triethoxy)silane (APTES) and Glycidoxypropyl(trimethoxy)silane (GPMS) modified PSNG electrodes and the transduced signal was used to investigate the dielectric mechanisms for multiplex analyses. The results from amperometric response and impedance measurement delivered the scale of interaction between anti-hCG antibody and hCG that exhibited 6.5 times higher sensitivity for the chemical linker, APTES than GPMS. Under optimized experimental conditions, APTES and GPMS modified immunosensor has a limit of detection as 0.56mIU/ml and 2.93mIU/ml (at S/N=3), with dissociation constants (Kd) of 5.65±2.5mIU/ml and 7.28±2.6mIU/ml, respectively. These results suggest that multiplex analysis of single target could enhance the accuracy of detection and reliable for real-time comparative analyses. The designed PSNG is simple, feasible, requires low sample consumption and could be applied for any given multiplex analyses.

Matched MeSH terms: Limit of Detection
Fulltext A simple, high-throughput, colourimetric, field applicable loop-mediated isothermal amplification (HtLAMP) assay for malaria elimination

Britton S, Cheng Q, Sutherland CJ, McCarthy JS

Malar J, 2015;14:335.
PMID: 26315027 DOI: 10.1186/s12936-015-0848-3

To detect all malaria infections in elimination settings sensitive, high throughput and field deployable diagnostic tools are required. Loop-mediated isothermal amplification (LAMP) represents a possible field-applicable molecular diagnostic tool. However, current LAMP platforms are limited by their capacity for high throughput.

Matched MeSH terms: Limit of Detection
Electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere label for detection of Vibrio cholerae

Liew PS, Lertanantawong B, Lee SY, Manickam R, Lee YH, Surareungchai W

Talanta, 2015 Jul 1;139:167-73.
PMID: 25882423 DOI: 10.1016/j.talanta.2015.02.054

Vibrio cholerae is a Gram-negative bacterium that causes cholera, a diarrheal disease. Cholera is widespread in poor, under-developed or disaster-hit countries that have poor water sanitation. Hence, a rapid detection method for V. cholerae in the field under these resource-limited settings is required. In this paper, we describe the development of an electrochemical genosensor assay using lyophilized gold nanoparticles/latex microsphere (AuNPs-PSA) reporter label. The reporter label mixture was prepared by lyophilization of AuNPs-PSA-avidin conjugate with different types of stabilizers. The best stabilizer was 5% sorbitol, which was able to preserve the dried conjugate for up to 30 days. Three methods of DNA hybridization were compared and the one-step sandwich hybridization method was chosen as it was fastest and highly specific. The performance of the assay using the lyophilized reagents was comparable to the wet form for detection of 1aM to 1fM of linear target DNA. The assay was highly specific for V. cholerae, with a detection limit of 1fM of PCR products. The ability of the sensor is to detect LAMP products as low as 50ngµl(-1). The novel lyophilized AuNPs-PSA-avidin reporter label with electrochemical genosensor detection could facilitate the rapid on-site detection of V. cholerae.

Matched MeSH terms: Limit of Detection
Fulltext Subtractive inhibition assay for the detection of Campylobacter jejuni in chicken samples using surface plasmon resonance

Masdor NA, Altintas Z, Shukor MY, Tothill IE

Sci Rep, 2019 09 20;9(1):13642.
PMID: 31541137 DOI: 10.1038/s41598-019-49672-2

In this work, a subtractive inhibition assay (SIA) based on surface plasmon resonance (SPR) for the rapid detection of Campylobacter jejuni was developed. For this, rabbit polyclonal antibody with specificity to C. jejuni was first mixed with C. jejuni cells and unbound antibody was subsequently separated using a sequential process of centrifugation and then detected using an immobilized goat anti-rabbit IgG polyclonal antibody on the SPR sensor chip. This SIA-SPR method showed excellent sensitivity for C. jejuni with a limit of detection (LOD) of 131 ± 4 CFU mL-1 and a 95% confidence interval from 122 to 140 CFU mL-1. The method has also high specificity. The developed method showed low cross-reactivity to bacterial pathogens such as Salmonella enterica serovar Typhimurium (7.8%), Listeria monocytogenes (3.88%) and Escherichia coli (1.56%). The SIA-SPR method together with the culturing (plating) method was able to detect C. jejuni in the real chicken sample at less than 500 CFU mL-1, the minimum infectious dose for C. jejuni while a commercial ELISA kit was unable to detect the bacterium. Since the currently available detection tools rely on culturing methods, which take more than 48 hours to detect the bacterium, the developed method in this work has the potential to be a rapid and sensitive detection method for C. jejuni.

Matched MeSH terms: Limit of Detection
Magnetic poly(β-cyclodextrin-ionic liquid) nanocomposites for micro-solid phase extraction of selected polycyclic aromatic hydrocarbons in rice samples prior to GC-FID analysis

Boon YH, Mohamad Zain NN, Mohamad S, Osman H, Raoov M

Food Chem, 2019 Apr 25;278:322-332.
PMID: 30583379 DOI: 10.1016/j.foodchem.2018.10.145

Poly(β-cyclodextrin functionalized ionic liquid) immobilized magnetic nanoparticles (Fe3O4@βCD-Vinyl-TDI) as sorbent in magnetic µ-SPE was developed for the determination of selected polycyclic aromatic hydrocarbons (PAHs) in rice samples coupled with gas chromatographic-flame ionization detector (GC-FID). The nanocomposite was characterized by various tools and significant parameters that affected the extraction efficiency of PAHs were investigated. The calibration curves were linear for the concentration ranging between 0.1 and 500 μg kg-1 with correlation determinations (R2) from 0.9970 to 0.9982 for all analytes. Detection limits ranged at 0.01-0.18 μg kg-1 in real matrix. The RSD values ranged at 2.95%-5.34% (intra-day) and 4.37%-7.05% (inter-day) precision for six varied days. The sorbents showed satisfactory reproducibility in 2.9% to 9.9% range and acceptable recovery values at 80.4%-112.4% were obtained for the real sample analysis. The optimized method was successfully applied to access content safety of selected PAHs for 24 kinds of commercial rice available in Malaysia.

Matched MeSH terms: Limit of Detection
Reflectance aptasensor based on metal salphen label for rapid and facile determination of insulin

Taib M, Tan LL, Abd Karim NH, Ta GC, Heng LY, Khalid B

Talanta, 2020 Jan 15;207:120321.
PMID: 31594568 DOI: 10.1016/j.talanta.2019.120321

An optical aptasensor-based sensing platform for rapid insulin detection was fabricated. Aminated porous silica microparticles (PSiMPs) were synthesized via a facile mini-emulsion method to provide large surface area for covalent immobilization of insulin-binding DNA aptamer (IGA3) by glutaraldehyde cross-linking protocol. A Nickel-salphen type complex with piperidine side chain [Ni(II)-SP] was synthesized with a simple one-pot reaction, and functionalized as an optical label due to strong π-π interaction between aromatic carbons of G-quadruplex DNA aptamer and planar aromatic groups of Ni(II)-SP to form the immobilized IGA3-Ni(II)-SP complex, i.e. the dye-labeled aptamer, thereby bringing yellow colouration to the immobilized G-quartet plane. Optical characterization of aptasensor towards insulin binding was carried out with a fiber optic reflectance spectrophotometer. The maximum reflectance intensity of the immobilized IGA3-Ni(II)-SP complex at 656 nm decreased upon binding with insulin as aptasensor changed to brownish orange colouration in the background. This allows optical detection of insulin as the colour change of aptasensor is dependent on the insulin concentration. The linear detection range of the aptasensor is obtained from 10 to 50 μIU mL-1 (R2 = 0.9757), which conformed to the normal fasting insulin levels in human with a limit of detection (LOD) at 3.71 μIU mL-1. The aptasensor showed fast response time of 40 min and long shelf life stability of >3 weeks. Insulin detection using healthy human serums with informed consent provided by participants suggests the DNA aptamer biosensor was in good agreement with ELISA standard method using BIOMATIK Human INS (Insulin) ELISA Kit.

Matched MeSH terms: Limit of Detection
Fulltext Supramolecular Electrochemical Sensor for Dopamine Detection Based on Self-Assembled Mixed Surfactants on Gold Nanoparticles Deposited Graphene Oxide

Uppachai P, Srijaranai S, Poosittisak S, Md Isa I, Mukdasai S

Molecules, 2020 May 29;25(11).
PMID: 32485804 DOI: 10.3390/molecules25112528

A new supramolecular electrochemical sensor for highly sensitive detection of dopamine (DA) was fabricated based on supramolecular assemblies of mixed two surfactants, tetra-butylammonium bromide (TBABr) and sodium dodecyl sulphate (SDS), on the electrodeposition of gold nanoparticles on graphene oxide modified on glassy carbon electrode (AuNPs/GO/GCE). Self-assembled mixed surfactants (TBABr/SDS) were added into the solution to increase the sensitivity for the detection of DA. All electrodes were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The supramolecular electrochemical sensor (TBABr/SDS⋅⋅⋅AuNPs/GO/GCE) showed excellent electrocatalytic activity toward the oxidation of DA. Under the optimum conditions, the concentration of DA was obtained in the range from 0.02 µM to 1.00 µM, with a detection limit of 0.01 µM (3s/b). The results displayed that TBABr/SDS⋅⋅⋅AuNPs/GO/GCE exhibited excellent performance, good sensitivity, and reproducibility. In addition, the proposed supramolecular electrochemical sensor was successfully applied to determine DA in human serum samples with satisfactory recoveries (97.26% to 104.21%).

Matched MeSH terms: Limit of Detection
Proline-Modified UIO-66 as Nanocarriers to Enhance Candida rugosa Lipase Catalytic Activity and Stability for Electrochemical Detection of Nitrofen

Cheng Y, Lai OM, Tan CP, Panpipat W, Cheong LZ, Shen C

ACS Appl Mater Interfaces, 2021 Jan 27;13(3):4146-4155.
PMID: 33440928 DOI: 10.1021/acsami.0c17134

Immobilization can be used to improve the stability of lipases and enhances lipase recovery and reusability, which increases its commercial value and industrial applications. Nevertheless, immobilization frequently causes conformational changes of the lipases, which decrease lipase catalytic activity. in the present work, we synthesized UIO-66 and grafted UIO-66 crystals with proline for immobilization of Candida rugosa lipase (CRL). As indicated by steady-state fluorescence microscopy, grafting of proline onto UIO-66 crystals induced beneficial conformational change in CRL. CRL immobilized on UIO-66/Pro (CRL@UIO-66/Pro) demonstrated higher enzyme activity and better recyclability than that immobilized on UIO-66 (CRL@UIO-66) in both hydrolysis (CRL@UIO-66/Pro: 0.34 U; CRL@UIO-66: 0.15 U) and transesterification (CRL@UIO-66/Pro: 0.93 U; CRL@UIO-66: 0.25 U) reactions. The higher values of kcat and kcat/Km of CRL@UIO-66/Pro also showed that it had better catalytic efficiency as compared to CRL@UIO-66. It is also worth noting that CRL@UIO-66/Pro (0.93 U) demonstrated a much higher transesterification activity as compared to free CRL (0.11 U), indicating that UIO-66/Pro has increased the solvent stability of CRL. Both CRL@UIO-66 and CRL@UIO-66/Pro were also used for the fabrication of biosensors for nitrofen with a wide linear range (0-100 μM), lower limit of detection, and good recovery rate.

Matched MeSH terms: Limit of Detection
Fulltext Alzheimer's Disease Determination by a Dual Probe on Gold Nanourchins and Nanohorn Hybrids

Qiu Z, Shen Q, Jiang C, Yao L, Sun X, Li J, et al.

Int J Nanomedicine, 2021;16:2311-2322.
PMID: 33776435 DOI: 10.2147/IJN.S302396

Background: Alzheimer's disease (AD) is a neurodegenerative chronic disorder that causes dementia and problems in thinking, cognitive impairment and behavioral changes. Amyloid-beta (Aβ) is a peptide involved in AD progression, and a high level of Aβ is highly correlated with severe AD. Identifying and quantifying Aβ levels helps in the early treatment of AD and reduces the factors associated with AD.
Materials and Methods: This research introduced a dual probe detection system involving aptamers and antibodies to identify Aβ. Aptamers and antibodies were attached to the gold (Au) urchin and hybrid on the carbon nanohorn-modified surface. The nanohorn was immobilized on the sensor surface by using an amine linker, and then a Au urchin dual probe was immobilized.
Results: This dual probe-modified surface enhanced the current flow during Aβ detection compared with the surface with antibody as the probe. This dual probe interacted with higher numbers of Aβ peptides and reached the detection limit at 10 fM with R2=0.992. Furthermore, control experiments with nonimmune antibodies, complementary aptamer sequences and control proteins did not display the current responses, indicating the specific detection of Aβ.
Conclusion: Aβ-spiked artificial cerebrospinal fluid showed a similar response to current changes, confirming the selective identification of Aβ.

Matched MeSH terms: Limit of Detection
Nylon 6,6 modified screen printed carbon electrodes as electrochemical sensors for rapid chlorothalonil determination in water samples using differential pulse cathodic stripping voltammetry

Thanalechumi P, Mohd Yusoff AR, Yusop Z

J Environ Sci Health B, 2019;54(4):294-302.
PMID: 30729855 DOI: 10.1080/03601234.2018.1561057

A newly developed electrochemical sensor for chlorothalonil based on nylon 6,6 film deposited onto screen printed electrode (SPE) with electrochemical modulation of pH at the electrode/solution interface was studied for the first time. Differential pulse cathodic stripping voltammetry (DPCSV) was used to carry out the electrochemical and analytical studies. Experimental parameters such as accumulation potential, initial potential, accumulation time and pH of Britton-Robinson buffer have been optimized. Chlorothalonil gave optimum analytical signal in a medium of 0.04 M Britton-Robinson buffer at pH 6.0. A well-defined reduction peak was observed, at Ep= -0.851 and -0.938 V vs. Ag/AgCl (3.0 M KCl) for both bare SPE and modified SPE, respectively. The peak currents of modified SPE were significantly increased as compared to bare SPE. At the modified SPE, a linear relationship between the peak current and chlorothalonil concentration was obtained in the range from 0.1 to 2.8 × 10-6 M with a detection limit of 1.53 × 10-8 M (S/N= 3). The practical applicability of the newly developed method has been demonstrated on analyses of real water samples. The newly developed sensor shows good reproducibility with RSD of 3.92%. The nylon 6,6 modified SPE showed itself as promising sensor with good selectivity for chlorothalonil determination.

Matched MeSH terms: Limit of Detection
Deriving the optimal limit of detection for an HCV point-of-care test for viraemic infection: analysis of a global dataset

Morgan Freiman J, Wang J, Easterbrook PJ, Robert Horsburgh C, Marinucci F, White LF, et al.

J Hepatol, 2019 Feb 20.
PMID: 30797050 DOI: 10.1016/j.jhep.2019.02.011

BACKGROUND & AIMS: Affordable point-of-care (POC) tests for hepatitis C (HCV) viraemia are needed to improve access to treatment in low and middle income countries (LMICs). Our aims were to determine the target limit of detection (LOD) necessary to diagnose the majority of persons with HCV eligible for treatment, and identify characteristics associated with low-level viraemia (LLV) (defined as the lowest 3% of the distribution of HCV RNA) to understand those at risk of being mis-diagnosed.
METHODS: We established a multi-country cross-sectional dataset of first available quantitative HCV RNA linked to demographic and clinical data. We excluded individuals on HCV treatment. We analyzed the distribution of HCV RNA and determined critical thresholds for detection of HCV viraemia. We then performed logistic regression to evaluate factors associated with LLV, and derived relative sensitivities for significant covariates.
RESULTS: The dataset included 66,640 individuals with HCV viraemia from Georgia (44.4%), Canada (40.9%), India (8.1%), Cambodia (2.6%), Egypt (1.6%), Pakistan (1.3%), Cameroon (0.4%), Indonesia (0.2%), Thailand (0.2%), Vietnam (0.1%), Malaysia (0.05%), and Mozambique (0.02%). The 97% LOD was 1,318 IU/mL (95% CI 1298.4, 1322.3). Factors associated with LLV were younger age 18-30 vs. 51-64 years (OR 2.56 95% CI 2.19, 2.99), female vs. male sex (OR 1.32, 95% CI 1.18, 1.49), and advanced fibrosis stage F4 vs. F0-1 (OR 1.44, 95%CI 1.21, 1.69). Only the younger age group had a decreased relative sensitivity below 95% at 93.3%.
CONCLUSIONS: In this global dataset, a test with an LOD of 1,318 IU/mL would identify 97% of viraemic HCV infections among almost all populations. This LOD will help guide manufacturers in the development of affordable POC diagnostics to expand HCV testing and linkage to care in LMICs.
LAY SUMMARY: We created and analyzed a dataset from 12 countries with 66,640 participants with chronic hepatitis C virus infection. We determined that about 97% of those with viraemic infection had 1300 International Units/mL or more of circulating virus at the time of diagnosis. While current diagnostic tests can detect as little as 12 International Units/mL of virus, our findings suggest that increasing the level of detection closer to 1300 would maintain good test accuracy and will likely allow for more affordable portable tests to be developed for use in low and middle income countries.

Matched MeSH terms: Limit of Detection
A reduced graphene oxide-titanium dioxide nanocomposite based electrochemical aptasensor for rapid and sensitive detection of Salmonella enterica

Muniandy S, Teh SJ, Appaturi JN, Thong KL, Lai CW, Ibrahim F, et al.

Bioelectrochemistry, 2019 Jun;127:136-144.
PMID: 30825657 DOI: 10.1016/j.bioelechem.2019.02.005

Recent foodborne outbreaks in multiple locations necessitate the continuous development of highly sensitive and specific biosensors that offer rapid detection of foodborne biological hazards. This work focuses on the development of a reduced graphene oxide‑titanium dioxide (rGO-TiO2) nanocomposite based aptasensor to detect Salmonella enterica serovar Typhimurium. A label-free aptamer was immobilized on a rGO-TiO2 nanocomposite matrix through electrostatic interactions. The changes in electrical conductivity on the electrode surface were evaluated using electroanalytical methods. DNA aptamer adsorbed on the rGO-TiO2 surface bound to the bacterial cells at the electrode interface causing a physical barrier inhibiting the electron transfer. This interaction decreased the DPV signal of the electrode proportional to decreasing concentrations of the bacterial cells. The optimized aptasensor exhibited high sensitivity with a wide detection range (108 to 101 cfu mL-1), a low detection limit of 101 cfu mL-1 and good selectivity for Salmonella bacteria. This rGO-TiO2 aptasensor is an excellent biosensing platform that offers a reliable, rapid and sensitive alternative for foodborne pathogen detection.

Matched MeSH terms: Limit of Detection
Fulltext Rapid Quantification and Validation of Biomarker Scopoletin in Paederia foetida by qNMR and UV-Vis for Herbal Preparation

Tan DC, Quek A, Kassim NK, Ismail IS, Lee JJ

Molecules, 2020 Nov 06;25(21).
PMID: 33171900 DOI: 10.3390/molecules25215162

Scopoletin has previously been reported as a biomarker for the standardization of Paederia foetida twigs. This study is the first report on the determination and quantification of scopoletin using quantitative nuclear magnetic resonance (qNMR) in the different extracts of Paederia foetida twigs. The validated qNMR method showed a good linearity (r2 = 0.9999), limit of detection (LOD) (0.009 mg/mL), and quantification (LOQ) (0.029 mg/mL), together with high stability (relative standard deviation (RSD) = 0.022%), high precision (RSD < 1%), and good recovery (94.08-108.45%). The quantification results of scopoletin concentration in chloroform extract using qNMR and microplate ultraviolet-visible (UV-vis) spectrophotometer was almost comparable. Therefore, the qNMR method is deemed accurate and reliable for quality control of Paederia foetida and other medicinal plants without extensive sample preparation.

Matched MeSH terms: Limit of Detection
Microcrystalline cellulose/metal-organic framework hybrid as a sorbent for dispersive micro-solid phase extraction of chlorophenols in water samples

Ghaemi F, Amiri A

J Chromatogr A, 2020 Aug 30;1626:461386.
PMID: 32797858 DOI: 10.1016/j.chroma.2020.461386

In this study, the microcrystalline cellulose/metal-organic framework 199 hybrid (MCC/MOF-199) was applied as sorbent for the dispersive micro-solid phase-extraction (D-μSPE) of chlorophenols. The D-μSPE method combined with high-performance liquid chromatography- ultraviolet detection (HPLC-UV) was employed to determine of four chlorophenols including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), and 2,5-dichlorophenol (2,5-DCP) in aqueous. The main parameters of the D-μSPE process that influence the extraction (i.e. the amount of sorbent, elution condition, extraction time, and pH) were investigated and optimized. Based on the outputs, the presence of MCC on the surface of MOF-199 leads to improve the properties of MOF-199 and the MCC/MOF-199 has the highest sorption capacity, durability, and porosity in comparison with MCC and MOF-199. According to the validation study at the optimized conditions, the linearity for the analytes was achieved in the range from 0.1 to 200 ng mL-1 for 2-CP and 4-CP and 0.15 to 200 ng mL-1 for 2,3-DCP and 2,5-DCP with correlation coefficients between 0.9928 and 0.9965. The limits of detection calculated at S/N=3 were in the range of 0.03-0.05 ng mL-1. Besides, the relative standard deviations (RSDs) for three spiking levels (0.2, 10,100 ng mL-1) do not exceed 6.8% and extraction recoveries are between 81.0% and 88.3%. Finally, the D-μSPE-HPLC-UV method was successfully applied to the analysis of CPs in real water samples (mineral, river and wastewater samples) with good recoveries (95.8 to 99.5%) and satisfactory precisions (RSD < 6.8%).

Matched MeSH terms: Limit of Detection
Electrochemical DNA detection of hepatitis E virus genotype 3 using PbS quantum dot labelling

Ngo DB, Chaibun T, Yin LS, Lertanantawong B, Surareungchai W

Anal Bioanal Chem, 2021 Feb;413(4):1027-1037.
PMID: 33236225 DOI: 10.1007/s00216-020-03061-1

The aim of this study was to develop a highly specific electrochemical DNA sensor using functionalized lead sulphide (PbS) quantum dots for hepatitis E virus genotype 3 (HEV3) DNA target detection. Functionalized-PbS quantum dots (QDs) were used as an electrochemical label for the detection of HEV3-DNA target by the technique of square wave anodic stripping voltammetry (SWASV). The functionalized-PbS quantum dots were characterized by UV-vis, FTIR, XRD, TEM and zeta potential techniques. As-prepared, functionalized-PbS quantum dots have an average size of 4.15 ± 1.35 nm. The detection platform exhibited LOD and LOQ values of 1.23 fM and 2.11 fM, respectively. HEV3-DNA target spiked serum is also reported.Graphical abstract.

Matched MeSH terms: Limit of Detection
Magnetic molecularly imprinted polymer nanoparticles for the extraction and clean-up of thiamethoxam and thiacloprid in light and dark honey

Abdulhussein AQ, Jamil AKM, Bakar NKA

Food Chem, 2021 Oct 15;359:129936.
PMID: 33957328 DOI: 10.1016/j.foodchem.2021.129936

In this work, new selective and sensitive dual-template molecularly imprinted polymer nanoparticles (MIPs) were synthesized and characterized. Sorbent MIPs were investigated for simultaneous extraction and clean-up of thiamethoxam and thiacloprid from light and dark honey samples. In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry triple-quadrupole (UHPLC-MS/MS) (QQQ) was used to detect and quantify the pesticides. The kinetic model with adsorption kinetics of sorbent was investigated. The optimal adsorption conditions were 80 mg of polymer MIPs, a 30-min extraction time, and a pH of 7. The detection limit (LOD) and the quantification limit (LOQ) varied from 0.045 to 0.070 µg kg-1 and from 0.07 to 0.10 µg kg-1, respectively. The intra-day and inter-day precision (RSD, %) ranged from 1.3 to 2.0% and from 8.2 to 12.0%, respectively. The recovery of thiamethoxam and thiacloprid ranged from 96.8 to 106.5% and 95.3 to 104.4%, respectively, in light and dark honey samples.

Matched MeSH terms: Limit of Detection
Short targeting multiplex PCR assay to detect and discriminate beef, buffalo, chicken, duck, goat, sheep and pork DNA in food products

Uddin SMK, Hossain MAM, Chowdhury ZZ, Johan MRB

Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2021 Aug;38(8):1273-1288.
PMID: 34077338 DOI: 10.1080/19440049.2021.1925748

Food fraud is a global problem raising increased concerns during the past decades and food authenticity is now a burning issue. Beef, buffalo, chicken, duck, goat, sheep, and pork are heavily consumed meats bearing nutritional, economic and cultural/religious importance and are often found to be adulterated in raw and processed states. To authenticate these species, we developed and validated a highly specific multiplex (heptaplex) PCR assay targeting short length amplicons (73-263 bp) using seven pairs of species-specific primer sets targeting mitochondrial cytochrome b (cytb) and NADH dehydrogenase subunit 5 (ND5) genes. Specificity checking (in silico and in vitro) against 25 non-target species revealed no cross-species amplification. The developed multiplex assay was validated with various adulterated and heat-treated (boiled, microwaved and autoclaved) meatball products and were found to show high sensitivity and stability under all processing conditions. The assay was sensitive enough to detect 0.01-0.005 ng of DNA from raw meat and 0.5% (w/w) adulterated meat in mixed matrices. A market survey revealed mislabelling of 95% beef and 15% chicken products while pork products were found pure. Given some advantageous features including short sizes of amplicons, exceptional stability and superior sensitivity, the developed assay could be conveniently used for discriminatory detection of target species with a variety of raw meat as well as processed meat products undergoing extreme processing treatments.

Matched MeSH terms: Limit of Detection
A rapid MCM-41 dispersive micro-solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids

Yahaya N, Sanagi MM, Abd Aziz N, Wan Ibrahim WA, Nur H, Loh SH, et al.

Biomed Chromatogr, 2017 Feb;31(2).
PMID: 27474795 DOI: 10.1002/bmc.3803

A rapid dispersive micro-solid phase extraction (D-μ-SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM-41 was used as sorbent in d-μ-SPE of the azole compounds from biological fluids. Important D-μ-SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB-C18 column (2.1 × 100 mm, 3.5 μm), using a mobile phase of acetonitrile-0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v/v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1-10,000 μg/L with satisfactory limit of detection (≤0.06 μg/L) and limit of quantitation (≤0.3 μg/L). The proposed method also showed acceptable intra- and inter-day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3-114.8%. The MCM-41-D-μ-SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 μL); thus it is advantageous for routine drug analysis.

Matched MeSH terms: Limit of Detection
Detection of Citrus tristeza virus by using fluorescence resonance energy transfer-based biosensor

Shojaei TR, Salleh MA, Sijam K, Rahim RA, Mohsenifar A, Safarnejad R, et al.

Spectrochim Acta A Mol Biomol Spectrosc, 2016 Dec 05;169:216-22.
PMID: 27380305 DOI: 10.1016/j.saa.2016.06.052

Due to the low titer or uneven distribution of Citrus tristeza virus (CTV) in field samples, detection of CTV by using conventional detection techniques may be difficult. Therefore, in the present work, the cadmium-telluride quantum dots (QDs) was conjugated with a specific antibody against coat protein (CP) of CTV, and the CP were immobilized on the surface of gold nanoparticles (AuNPs) to develop a specific and sensitive fluorescence resonance energy transfer (FRET)-based nanobiosensor for detecting CTV. The maximum FRET efficiency for the developed nano-biosensor was observed at 60% in AuNPs-CP/QDs-Ab ratio of 1:8.5. The designed system showed higher sensitivity and specificity over enzyme linked immunosorbent assay (ELISA) with a limit of detection of 0.13μgmL(-1) and 93% and 94% sensitivity and specificity, respectively. As designed sensor is rapid, sensitive, specific and efficient in detecting CTV, this could be envisioned for diagnostic applications, surveillance and plant certification program.

Matched MeSH terms: Limit of Detection

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