Folic Acid Sensor Research Articles

A “turn-on” fluorescent sensor for folic acid based on thiourea-decorated bis-cyanostilbene

Although some detection methods for folic acid have been developed based on the conventional instruments, the rapid, simple and in-situ detection for folic acid was rarely reported. In this work, a “turn-on” and “color-changing” fluorescence sensor (TBCS) on detecting folic acid was designed and synthesized. TBCS emits the green fluorescence, which transferred to the strong blue fluorescence after binding folic acid. The high sensing selectivity was observed among various ions and biomolecules. The detection limitation of TBCS for folic acid was 4.32 × 10−7 M. The sensing mechanism was proposed as that the ICT effectiveness of TBCS was interrupted by sensing folic acid. The application experiments on test paper, folic acid tablets and simulated sample displayed the good in-situ detecting ability of TBCS for folic acid, suggesting the good application prospect on rapid, simple and in-situ detecting folic acid in real environments.

Highly Stable Rare Earth Metal-Organic Frameworks for Fluorescence Recognition of Folic Acid, Proton Conduction, and Magnetic Refrigeration.

Four new isostructural rare earth metal-organic frameworks (RE-MOFs) were synthesized and full characterized, namely, {[(CH)2NH2]3[RE2(BTDBA)2(HCOO)]·5H2O·2DMF}n (H4BTDBA = (4',4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid); RE = Eu (JXUST-34), Gd (JXUST-35), Tb (JXUST-36), and Dy (JXUST-37)). The single-crystal structures analysis shows that JXUST-34-37 are chain-based three-dimensional structures. Importantly, JXUST-34 exhibits excellent water, organic solvents, and acid-base stability, which can be used as a fluorescence sensor for folic acid and Al3+ with detection limits of 0.02 mM and 0.05 μM, respectively. The presence of free [(CH)2NH2]+ cations in the channels can engage the proton carrier during proton conduction. JXUST-34-37 display good proton conductivity, and the conductivities vary with relative humidity and temperatures, among which JXUST-37 has the highest conductivity of 9.66 × 10-3 S·cm-1 at 60 °C and 98% RH. The magnetic studies show that the -ΔSm of JXUST-35 reaches 16.13 J kg-1 K-1 at 2 K and ΔH = 7 T. JXUST-34-37 show multifunctional properties of fluorescence sensing, high proton conductivity, and magnetic refrigeration, which provides a new clue for the development of fluorescent-responsive, magnetic-refrigerant, and proton-conductive RE-MOF materials.

FRET-based probe for ratiometric detection and imaging of folic acid in real-time

Inadequate folic acid intake is linked to diseases such as megaloblastic anemia, neural tube defects, and hyperhomocysteinemia, increasing the risk of vascular disease and thrombosis. Folic acid, a cofactor in various enzymes, can be produced by plants and bacteria, but not by humans and other animals. L-5-methyl-tetrahydrofolate (L-5-methyl-THF) is the primary dietary folate form, transported in circulation for cellular metabolism. Traditional methods of determining folic acid levels are unreliable and time-consuming. SenFol (Sensor for folic acid) is a fluorescence resonance energy transfer (FRET)-based nanosensor that we have developed by inserting folic acid-binding protein (FolT) as the folate detecting domain between the pair of enhanced cyan fluorescent protein (ECFP) and Venus. The developed sensor is highly specific, produces a quick signal, which is pH stable, and delivers precise, ratiometric readings in cell-based experiments. The projected affinity score of folic acid with FolT was −7.4 kcal/mol. The apparent affinity (Kd) of SenFol for folic acid is 28.49 × 10−9 M, with a detection range of 5 × 10−9 M to 5 × 10−7 M, and a maximum FRET ratio change of 0.45. WT SenFol, a highly efficient folic acid nanosensor, can dynamically detect intracellular folic acid content in E. coli, yeast, and HEK-293 T cells, confirming its potential.

Development of a highly sensitive voltammetric sensor for the detection of folic acid by using MoS2 and ionic liquid-modified carbon paste electrode.

Sensitive analytical determination of folic acid is important in clinical laboratories due to its versatile biological functions. A simple folic acid sensor was successfully fabricated based on two-dimensional transition metal dichalcogenide MoS2 modified carbon ionic liquid paste electrode (MoS2-CILPE). The electrochemical properties of the fabricated electrode were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry. The fabricated sensor displayed excellent electroactivity towards folic acid using CV. Under optimal conditions (0.1 M PBS (pH 7.0)), the DPV oxidation peak current was proportional to folic acid concentration in the range from 5.0 μM to 100.0 μM with an estimated limit of detection of 1.0 μM and limit of quantification of 5.0 μM. The ability of the sensor for routine analyses was demonstrated by the detection of folic acid present in folic acid tablets and urine samples with appreciable recovery values.

Voltammetric folic acid sensor based on nickel ferrite nanoparticles modified-screen printed graphite electrode

In this study, an electrochemical sensor for the quantification of folic acid with voltam­metric detection in physiological conditions was constructed. For this purpose, nickel ferrite (NiFe2O4) nanoparticles were used to modify the surface of a screen-printed graphite electrode (NiFe2O4/SPGE) and applied in the determination of folic acid. The modified electrode displays a strong electrochemical response to folic acid. Folic acid was determined electrochemically using the differential pulse voltammetry (DPV) technique with a detection limit of 0.09±0.001 µM in 0.2–147.0 µM linear range in phosphate buffer solution (PBS) at pH 7.0 with this NiFe2O4/SPGE sensor, which has the best electron transfer rate. Also, the sensitivity of the modified electrode was obtained as 0.1139 µA µM-1. The NiFe2O4/SPGE sensor was successfully applied for the determination of folic acid in real samples.

Facile bimetallic co-amplified electrochemical sensor for folic acid sensing based on CoNPs and CuNPs.

Folic acid (FA) is essential for human health, particularly for pregnant women and infants. In this work, a glassy carbon electrode (GCE) was modified by a bimetallic layer of Cu/Co nanoparticles (CuNPs/CoNPs) as a synergistic amplification element by simple step-by-step electrodeposition, and was used for sensitive detection of FA. The proposed CuNPs/CoNPs/GCE sensor was characterized by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and field emission scanning electron microscopy (FESEM). Then, under optimal conditions, a linear relationship was obtained in the wide range of 110.00-1750.00 μM for the detection of FA with a limit of detection (LOD) of 34.79 μM (S/N = 3). The sensitivity was calculated as 0.096 μA μM-1 cm-2. Some interfering compounds including glucose (Glc), biotin, dopamine (DA), and glutamic acid (Glu) showed little effect on the detection of FA by amperometry (i-t). Finally, the average recovery obtained was in a range of 91.77-110.06%, with a relative standard deviation (RSD) less than 8.00% in FA tablets, indicating that the proposed sensor can accurately and effectively detect the FA content in FA tablets.

Fabrication of enzyme-less folic acid sensor probe based on facile ternary doped Fe2O3/NiO/Mn2O3 nanoparticles

• Fe 2 O 3 /NiO/Mn 2 O 3 nanoparticles prepared by facile wet-chemical method. • Highly sensitive Folic acid sensor by reliable electrochemical method. • Selective enzyme-less FA sensor development. • Sensor exhibits a large-linear dynamic ranges. • Effective enzyme-less sensor for health care and biomedical fields. In this approach, folic acid (FA) sensor was fabricated with wet-chemically prepared Fe 2 O 3 /NiO/Mn 2 O 3 nanoparticles (NPs), which was coated on a glassy carbon electrode (GCE) in the form of thin layers to create the desired sensor. The synthesized NPs were characterized by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Tunneling Electron Microscopy (TEM), surface area (BET), and Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy-dispersive X-ray spectroscopy (EDS). The fabricated sensor, Fe 2 O 3 /NiO/Mn 2 O 3 NPs/Nafion/GCE is responded linearly in electrochemical method over 0.1 nM to 0.01 mM of folic acid (FA) and denoted as a dynamic range of detection (LDR). The slope of LDR is designated as the sensor sensitivity, which is appreciable (48.588 µA µM -1 cm −2 ). The lower limit of FA detection is evaluated at a signal-to-noise ratio of 3, and it is equal to 96.89 ± 4.85 pM. The sensor analytical parameters such as stability, reproducibility, sensitivity, response time and long-time stability in buffer phase are found as outstanding. The FA sensor was valued to analyze the biological samples and found acceptable and satisfactory results. This prospective sensor might be an efficient probe for diagnosis of bio-samples in field of health career sector.

Multi-walled carbon nanotubes/nickel hydroxide composite applied as electrochemical sensor for folic acid (vitamin B9) in food samples

Folic acid (FA) acts as an essential nutrient for body functions. Several countries have already proposed a resolution for flour fortification with iron and FA; thus, of food industry concern. Therefore, a new electroanalytical method based on a composite material of functionalized MWCNTs with nickel hydroxide (f-MWCNT-Ni(OH)2) is hereby proposed. This composite material was characterized by FT-IR, TGA, SEM and TEM techniques. An inorganic ionic silsesquioxane polymer (Si4Pic+Cl−) was used to disperse the composite and applied on the modification of a glassy carbon electrode (GCE). Linear response from 0.5–26 μmol L−1 was obtained based on FA electrochemical oxidation through differential pulse voltammetry. The LoD and LoQ values obtained were 0.095 μmol L−1 and 0.3 μmol L−1 of FA, respectively. The GCE/f-MWCNT-Ni(OH)2-Si4Pic+Cl− was applied for the quantification of FA in wheat flour, fortifier, and dietary supplement. Validation was performed through a comparison with molecular absorption spectrometry, showing the accuracy of the newly proposed method.

Rapid One-Pot Synthesis of Polydopamine Encapsulated Carbon Anchored with Au Nanoparticles: Versatile Electrocatalysts for Chloramphenicol and Folic Acid Sensors.

Designing and engineering nanocomposites with tailored physiochemical properties through teaming distinct components is a straightforward strategy to yield multifunctional materials. Here, we describe a rapid, economical, and green one-pot microwave synthetic procedure for the preparation of ternary nanocomposites carbon/polydopamine/Au nanoparticles (C/PDA/AuNPs; C = carbon nanotubes (CNTs), reduced graphene oxide (rGO)). No harsh reaction conditions were used in the method, as are used in conventional hydrothermal or high-temperature methods. The PDA unit acts as a non-covalent functionalizing agent for carbon, through π stacking interactions, and also as a stabilizing agent for the formation of AuNPs. The CNTs/PDA/AuNPs modified electrode exhibited excellent electrocatalytic activity to oxidize chloramphenicol and the resulting sensor exhibited a low detection limit (36 nM), wide linear range (0.1–534 μM), good selectivity (against 5-fold excess levels of interferences), appreciable reproducibility (3.47%), good stability (94.7%), and practicality (recoveries 95.0%–98.4%). Likewise, rGO/PDA/AuNPs was used to fabricate a sensitive folic acid sensor, which exhibits excellent analytical parameters, including wide linear range (0.1–905 μM) and low detection limit (25 nM). The described synthetic route includes fast reaction time (5 min) and a readily available household microwave heating device, which has the potential to significantly contribute to the current state of the field.

Electrochemical investigation of a novel surfactant for sensitive detection of folic acid in pharmaceutical and biological samples by multivariate optimization

The present study is a report about of an electrochemical sensor for folic acid (FA) detection based on the adsorption of a cationic surfactant, n-dodecylpyridinium chloride (DPC), at the surface of a carbon paste electrode (CPE). The DPC performance compares with the cetyltrimethylammonium bromide (CTAB) to improve the electrochemical reaction and response of FA. It is notable for the first time, DPC is successfully utilized in electrochemical analysis. Determination of FA is performed by differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronocoulometry (CC) techniques. Response surface methodology (RSM) and central composite rotatable design (CCRD) is chosen for optimization of effective variables in the voltammetric peak current of FA. Another innovation in this study is the utilization of cubic terms in the experimental design. Under the optimized conditions, the FA oxidation peak current was linear to the FA concentration in the range of 0.01 µM–10.69 μM with the detection limit of 2.9 nM (3σ). After studying the influence of probable interferences, it was found that the offered method has excellent selectivity for FA. Finally, the offered procedure was successfully applied to the FA detection in tablet and urine samples with satisfactory results.

3D reduced graphene oxide/FeNi3-ionic liquid nanocomposite modified sensor; an electrical synergic effect for development of tert-butylhydroquinone and folic acid sensor

This paper reports an electroanalytical sensor developed based on reduced graphene oxide/FeNi3 (FeNi3/rGO)-ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate (HMPF6) carbon paste electrode (CPE) for determining the antioxidant additive tertbutylhydroquinone (TBHQ) in the presence of folic acid. The FeNi3/rGO synthesized by hydrothermal strategy and characterized by X-ray diffraction (XRD) and FESEM methods. The electrochemical response were found to be linearly symmetrical to TBHQ and folic acid concentrations in the range from 0.05 to 900 μM and 0.6–1100 μM with detection limits of 10.0 nM and 0.1 μM, respectively. The FeNi3/rGO/HMPF6/CPE showed high-quality for determination of TBHQ in the presence of folic acid in the real samples with the separation potential ∼600 mV.

A fluorescent sensor for folic acid based on crown ether-bridged bis-tetraphenylethylene.

Aggregation-induced emission (AIE) provides a new strategy for preparing fluorescent sensors in aggregated state. In this paper, a series of crown ether-bridged bis-tetraphenylethylene compounds were synthesized in 78-84% yield by a simple procedure. The molecules exhibited excellent AIE properties in THF/H2O solutions and solid films. The investigation on sensing abilities for various biomolecules and metal ions suggested that Bis-TPE-1 possessed obvious response to folic acid, with fluorescence enhancement and blue shift of maximum emission wavelength from 380 nm to 365 nm. The detection limit for folic acid was 6.36 × 10-7 M, and the sensor's selectivity for folic acid was little interfered by the other species. The sensor mechanism was studied by FT-IR, 1H NMR, MS spectra and fluorescence Jobs' plot. The selective sensor for folic acid was applied in test paper and the analyses of real samples of mung bean and spinach. The superior bioimaging performance of Bis-TPE-1 for sensing folic acid was confirmed by the live cell imaging experiments, which indicated its good practical application potential for detecting folic acid.

Cu-Mn codoped ZnS quantum dots-based ratiometric fluorescent sensor for folic acid

In the design of new fluorescent sensors, exploration of new materials with excellent properties and smart designs is of continuing interest. Herein, we designed a dual-emission ratiometric fluorescent sensor by doping ZnS quantum dots (QDs) with Cu2+ and Mn2+ ions. The codoped ZnS QDs with two separated dopant emissions were used as ratiometric fluorescent sensors for folic acid (FA). With addition of FA, the Cu dopant emission was quenched while the Mn dopant emission was enhanced. The fluorescence intensity ratios versus the FA concentrations could be fitted to a linear regression equation ranging from 0.01 to 5 μM (R2 = 0.995) and the detection limit was calculated to be 6 nM. Thus, this method generated ratiometric fluorescence signals for quantitative detection of FA. To understand the specific fluorescence response of the sensors for FA, the sensing mechanism was proposed based on electron transfer between QDs and FA. Additionally, the sensors were successfully applied to the determination of FA in spiked samples and recoveries were ranged from 95.5 to 102.2%. Therefore, the sensors show high sensitivity and selectivity for FA and the proposed method has good potential for extension to the detection of other biological molecules after further development.

A sensitive electrochemiluminescence folic acid sensor based on a 3D graphene/CdSeTe/Ru(bpy)32+-doped silica nanocomposite modified electrode

A rapid, facile, sensitive electrochemiluminescence sensor was fabricated based on a 3D graphene/CdSeTe/Ru(bpy)32+-doped silica nanocomposite modified electrode for the detection of folic acid (FA). 3D graphene which has the ability to enhance the intensity of electrochemiluminescence (ECL) was synthesized by a one-pot hydrothermal method. Then CdSeTe served as amplification elements were successively labeled on the layer of 3D graphene. In addition, per Ru(bpy)32+-doped silica nanoparticle encapsulated a great deal of Ru(bpy)32+, the ECL intensity has been further greatly enhanced. Importantly, the ECL signal on the 3D graphene/CdSeTe/Ru(bpy)32+-doped silica nanocomposite modified electrode was amplified by FA. The optimum detecting conditions were established by single-factor analysis and response surface multivariate optimization methodologies. Under the optimum conditions, the ECL intensity was well-proportional to logarithmic FA concentration range from 1.0×10−11M to 1.0×10−6M with the detect limit as low as 3.6×10−12M. In application to detect FA in drugs, the recoveries range from 95.0% to 97.5%, which indicates this sensor having potential application in folic acid analysis in real samples.

Delicate photoelectrochemical sensor for folic acid based on carbon nanohorns supported interwoven titanate nanotubes

Herein, a signal-amplified photoelectrochemical sensing platform based on interwoven titanate nanotubes and carbon nanohorns conjugates was constructed for folic acid determination. Specifically, titanate nanotubes with reticulation structure were employed as optoelectronic element, which possessed fine photocatalytic activity and enhancement in facilitating fast and long-distance electron transport. Hierarchical-structured carbon nanohorns were introduced as the mainstay to provide as the electron-transport medium to capture and transmit electrons from excited titanate nanotubes to the sensing matrix owing to the prominent conductivity and large surface. Furthermore, the holes from valence band of stimulated titanate nanotubes could transfer to their surface and be consumed by folic acid, thus enhancing the photocurrent response. Hence, under the optimal conditions, a linear relationship between photocurrent increase and logarithm concentration of folic acid was obtained in the wide range from 1×10−10 to 5×10−5 M with a detection limit of (2.5±0.005)×10−11 M. The well-designed transducer showed practical advantages, such as universality, simplicity and convenience, opening up a valuable application for other important molecules assessment.

Development of electrochemical folic acid sensor based on hydroxyapatite nanoparticles

We report the synthesis of hydroxyapatite (HA) nanoparticles (NPs) by a simple microwave irradiation method and its application as sensing element for the precise determination of folic acid (FA) by electrochemical method. The structure and composition of the HA NPs characterized using XRD, FTIR, Raman and XPS. SEM and EDX studies confirmed the formation of elongated spherical shaped HA NPs with an average particle size of about 34nm. The HA NPs thin film on glassy carbon electrode (GCE) were deposited by drop casting method. Electrocatalytic behavior of FA in the physiological pH 7.0 was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. The fabricated HA/GCE exhibited a linear calibration plot over a wide FA concentration ranging from 1.0×10−7 to 3.5×10−4M with the detection limit of 75nM. In addition, the HA NPs modified GCE showed good selectivity toward the determination of FA even in the presence of a 100-fold excess of ascorbic acid (AA) and 1000-fold excess of other common interferents. The fabricated biosensor exhibits good sensitivity and stability, and was successfully applied for the determination of FA in pharmaceutical samples.

Fabrication of folic acid sensor based on the Cu doped SnO2 nanoparticles modified glassy carbon electrode

A novel folic acid biosensor has been fabricated using Cu doped SnO2 nanoparticles (NPs) synthesized by a simple microwave irradiation method. Powder XRD and TEM studies confirmed that both the pure and Cu doped SnO2 (Cu: 0, 10, 20wt%) crystallized in tetragonal rutile-type structure with spherical morphology. The average crystallite size of pure SnO2 was estimated to be around 16 nm. Upon doping, the crystallite sizes decreased to 9 nm and 5 nm for 10 and 20wt% Cu doped SnO2 respectively. XPS studies confirmed the electronic state of Sn and Cu to be 4+ and 2+ respectively. Cu (20wt%) doped SnO2 NPs are proved to be a good sensing element for the determination of folic acid (FA). Cu-SnO2 NPs (20wt%) modified glassy carbon electrode (GCE) exhibited the lowest detection limit of 0.024 nM over a wide folic acid concentration range of 1.0 × 10−10 to 6.7 × 10−5 M at physiological pH of 7.0. The fabricated sensor is highly selective towards the determination of FA even in the presence of a 100 fold excess of common interferent ascorbic acid. The sensor proved to be useful for the estimation of FA content in pharmaceutical sample with satisfactory recovery.

On/off-switchable electrochemical folic acid sensor based on molecularly imprinted polymer electrode

The combination of smart polymers with molecular imprinting offers a powerful tool to design more effective sensors and medical devices. In this study, a temperature sensitive amine-terminated poly(N-isopropylacrylamide) block with (N,N'-methylenebisacrylamide) cross-linker along with o-phenylenediamine was electropolymerised on a gold electrode in the presence of folic acid (FA) as template to produce an on/off-switchable molecularly imprinted polymer (MIP) affinity sensor for folic acid. Differential pulse voltammetry and cyclic voltammetry were used to characterise the FA-imprinted layer. Incubation of the MIP-modified electrode with FA resulted in a suppression of the ferro/ferricyanide redox process. The highest sensitivity of this temperature gated on/off-switchable folic acid sensor was achieved at 22°C. Such switchable affinity materials offer considerable potential for the design of highly selective and controllable biosensors and immunoassays.

Biomimetic piezoelectric quartz sensor for folic acid based on a molecular imprinting technology

A novel molecularly imprinted polymer (MIP)-modified quartz crystal microbalance (QCM) sensor with high selectivity has been developed for the determination of folic acid via activator generated-atom transfer radical polymerization (AGET-ATRP) technique. It requires an alkyl halide (R-X) as an initiator, a transition metal complex as a catalyst, and an amine as reducing agent. Herein, chlorosilane was used as initiator which was grafted onto the self assembled monolayer modified-quartz crystal surface followed by the addition of pre-polymer mixture which latter underwent thermal cross-linking resulting in MIP-modified QCM sensor. The linear working range (quantification) was found to be 0.6-26.0 μg L-1, with the detection limit as low as 0.08 μg L-1 (S/N=3).

Voltammetric sensor based on ordered mesoporous carbon for folic acid determination

With ordered mesoporous carbon (OMC) as the modifier, a voltammetric sensor for folic acid (FA) was constructed on a glassy carbon electrode (GCE). Due to the good characteristics of OMC, FA exhibited an enhanced electrochemical response and lower reduction potential in the neutral solution. In addition, the experimental parameters such as pH values, accumulation time and potential were optimized. Using the differential pulse voltammetry (DPV) measurement, the peak current was found to be linear with FA concentration in the range from 5.0×10−10 to 1.0×10−7M with a lower detection limit of 6.0×10−11M (S/N=3). Also, in real samples analysis, the as-prepared sensor successfully gives satisfying results.