Detection of Phosphate in Human Blood Based on a Catalytic Hydrogen Wave at a Molybdenum Phosphide Modified Electrode

Development of electrochemical sensors for quick detection of environmental (soil and water) NPK ions

All over the world, technology is becoming more and more prevalent in agriculture. Different types of instruments are already being used in this sector. For the time being, every farmer is trying to produce more crops on a piece of land. Eventually, soil loses its nutrients; however, to grow more crops, farmers use more fertilizers without knowing the proper conditions of the soil in real time. To overcome this issue, many scientists have recently focused on developing electrochemical sensors to detect macronutrients, i.e., nitrogen (N), phosphorus (P), and potassium (K), in soil or water rapidly. In this review, we focus mainly on the recent developments in electrochemical sensors used for the detection of nutrients (NPK) in different types of samples. As it is outlined, the use of smart and portable electrochemical sensors can be helpful for the reduction of excess fertilizer and can play a vital role in maintaining suitable conditions in soils and water. We are optimistic that this review can guide researchers in the development of a portable and suitable NPK detection system for soil nutrients.

Electrochemical Sensors Based on Transition Metal Materials for Phenolic Compound Detection

Electrochemical sensors have been recognized as crucial tools for monitoring comprehensive chemical information, especially in the detection of a significant class of molecules known as phenolic compounds. These compounds can be present in water as hazardous analytes and trace contaminants, as well as in living organisms where they regulate their metabolism. The sensitive detection of phenolic compounds requires highly efficient and cost-effective electrocatalysts to enable the development of high-performance sensors. Therefore, this review focuses on the development of advanced materials with excellent catalytic activity as alternative electrocatalysts to conventional ones, with a specific emphasis on transition metal-based electrocatalysts for the detection of phenolic compounds. This research is particularly relevant in diverse sectors such as water quality, food safety, and healthcare.

Synthesis of rare-earth metal-organic frameworks to construct high-resolution sensing array for multiplex anions detection, cell imaging and blood phosphorus monitoring

Accurate detection and differentiation of multiple anions is still a difficult problem due to their wide variety, structural similarity, and mutual interference. Hence, four rare-earth metal-organic frameworks (RE-MOFs) including Dy-MOFs, Er-MOFs, Tb-MOFs and Y-MOFs are successfully prepared by using TCPP as the ligand and rare-earth ions as the metal center via coordination chelation. It is found that 7 anions can light up their fluorescence. Thus, a high-resolution sensing array based on RE-MOFs nanoprobes is employed to differentiate these anions from intricate analytes in real-time scenarios. The distinctive host-guest response promotes the RE-MOFs nanoprobes to selectively extract the target anions from the complex samples. By taking advantage of the cross-response between RE-MOFs nanoprobes and anions, it allows to create an array for detecting target analytes using pattern recognition. Additionally, RE-MOFs nanoprobes also facilitate the quantitative analysis of these anions (PO43-, H2PO4-, HPO42-, F-, S2-, CO32- and C2O42-). More importantly, the exceptional effectiveness of this method has been demonstrated through various successful applications, including quality monitoring of 8 toothpaste brands, intracellular phosphate imaging, and blood phosphorus detection in mice with vascular calcification. These findings provide robust evidence for the efficacy and reliability of the RE-MOFs nanoprobes array for anion recognition.

Self-Calibrating Lanthanide Infinite Coordination Polymer Constructs Fluorescent Probes: A Sensitive Approach for Early Diagnosis of Hepatocellular Carcinoma and Environmental Analysis

The development of a self-calibrating ratio fluorescence probe without the need for additional substrates is a major advancement in biosensing. In this study, at room temperature, a self-calibrating infinite coordination polymer (SSA-Tb-ATP ICPs) has been proposed by self-assembling adenosine triphosphate (ATP) with 5-sulfosalicylic acid (SSA) and Tb3+. Due to the antenna effect, SSA-Tb-ATP ICPs exhibited strong green fluorescence emission of Tb3+ (at 547 nm) and blue fluorescence emission of SSA (at 407 nm). This material offers several advantages over existing detection methods, including simplicity of synthesis and exceptional sensitivity. Our self-calibrating SSA-Tb-ATP ICPs demonstrated excellent performance in detecting alkaline phosphatase (ALP) and phosphate (Pi) in both serum and environmental samples with detection limits of 0.076 U/L and 0.025 μM, respectively. Moreover, we successfully employed the SSA-Tb-ATP ICPs to perform cellular imaging of ALP in both hepatocellular carcinoma cells (HepG2) and normal liver cells (LO2), representing a significant advancement in ALP detection and imaging. The simplicity of the synthesis and high sensitivity make this probe a promising tool for early diagnosis of hepatocellular carcinoma in clinical settings and environment analysis.

Kill two birds with one stone: Ratiometric sensing of phosphate via a single-component probe with fluorescence-scattering dual-signal response behavior

Ratiometric fluorescence sensors gain stronger anti-interference ability via self-calibration. Nevertheless, ratiometric analysis of phosphate (Pi) still faces problems such as complicated construction process of dual emission probes and possible interferences from outputting mono-category fluorescent signal. Herein, we propose a "kill two birds with one stone" strategy to address these challenges, by simply introducing a single-component probe, porphyrin paddlewheel framework-3 (PPF-3) nanosheets without modification, encapsulation or complex, to integrate fluorescence (FL)-second-order scattering (SOS) dual-signal for ratiometric detection of Pi. PPF-3 nanosheets are constructed by coordination of Co²⁺ with 5,10,15,20-tetrakis(4-carboxyl-phenyl)-porphyrin (TCPP) ligands, displaying weak FL and strong SOS, two different and independent signals. In the response system to Pi, Co²⁺ and TCPP serve as the recognition element and signal unit, respectively. After interacting with Pi, the high affinity for Co²⁺ makes Pi snatch Co²⁺ from the PPF-3 nanosheets, causing their structure disassembly (SOS decrease) and TCPP release (FL increase). Finally, the FL-SOS ratiometric platform is successfully employed to access Pi in real water samples. Synchronous collection of FL and SOS from the single-component probe provides a simpler and more efficient way on ratiometric sensor design as well as a new useful technique for monitoring target-induced aggregation and disaggregation behavior.

Detecting phosphate using lysine-sensitized terbium coordination polymer nanoparticles as ratiometric luminescence probes

Probes for detecting phosphate ions (Pi) are required for environmental monitoring and to protect human health. Here, novel ratiometric luminescent lanthanide coordination polymer nanoparticles (CPNs) were successfully prepared and used to selectively and sensitively detect Pi. The nanoparticles were prepared from adenosine monophosphate (AMP) and Tb³⁺, and lysine (Lys) was used as a sensitizer (through the antenna effect) to switch on Tb³⁺ luminescence at 488 and 544 nm while Lys luminescence at 375 nm was quenched because of energy transfer from Lys to Tb³⁺. The complex involved is here labeled AMP-Tb/Lys. Pi destroyed the AMP-Tb/Lys CPNs and therefore decreased the AMP-Tb/Lys luminescence intensity at 544 nm and increased the luminescence intensity at 375 nm at an excitation wavelength of 290 nm, meaning ratiometric luminescence detection was possible. The ratio between the luminescence intensities at 544 and 375 nm (I₅₄₄/I₃₇₅) was strongly associated with the Pi concentration between 0.1 and 6.0 μM, and the detection limit was 0.08 μM. The dual-emission reverse-change ratio luminescence sensing method can exclude environmental effects, so the proposed assay was found to be very selective. The method was successfully used to detect Pi in real water samples, and acceptable recoveries were found, suggesting that the method could be used in practice to detect Pi in water samples.

Progress and current trends in the electrochemical determination of phosphate ions for environmental and biological monitoring applications

The determination of phosphate ions in biological testing is critical for environmental safety. A reliable and accurate method is required to measure the true phosphate ion concentrations; in this regard, the electrochemical method is preferable because of its simple operation, fast response, and high sensitivity. By compiling existing electroanalytical techniques, researchers can compare the advantages and disadvantages of each method. This review examines the progress and recent advances in electrochemical sensing strategies adapted for the determination of phosphate ions in the environmental and during biological monitoring. We first discuss the history of phosphorus and the development of methods to detect phosphates. The recognition elements of phosphate ion sensors for environmental applications include metal-based, nanomaterial-based, carbon-based, and enzymatic electrodes. Phosphate determination in biological samples, such as blood serum, drugs, and other biological fluids, such as urine and saliva, as well as phosphate esters, is also discussed. The final part of our review addresses the current challenges that phosphate sensing technology faces and illustrates future opportunities for more reliable phosphate detection.

Enhanced Ultrasensitive Photoelectrochemical Probe for Phosphate Detection in Water Based on a Zirconium-Porphyrin Framework

Excessive phosphate poses a serious ecological and human health risk, and thereby, monitoring its trace concentration is of great significance to environmental protection and human health. In this work, a zirconium-porphyrin framework (PCN-222) with excellent stability and unique luminescence properties was designed to modify the surface of the indium tin oxide electrode, which was first used as a photoelectrochemical (PEC) probe for phosphate detection. The PCN-222-modified PEC probe demonstrated an excellent selectivity and stability and indicated a linear response to phosphate in the range of 0-10⁶ nM with a limit of detection (LOD) as low as 1.964 nM. To the best of our knowledge, this is the phosphate probe with the lowest LOD, and this is also the first signal-on PEC probe toward phosphate based on PCN-222. More importantly, the PEC probe can be validated for the good applicability of trace phosphate detection in real water samples, indicating a good application prospect. Finally, a series of electrochemical and spectroscopic studies have proved that phosphate can bind to the indium tin oxide (ITO)/PCN-222 electrode, which shortens the distance of the space charge region while reducing the bandwidth and thus facilitates the transfer of photogenerated electrons across the energy band barrier to reduce O₂ in the electrolyte, producing an enhanced cathodic photocurrent signal. The proposed strategy of the highly sensitive PEC probe provides a promising platform for more effective label-free phosphate monitoring in the environment and organisms.

Multi-Oxyanion Detection by an Organic Field-Effect Transistor with Pattern Recognition Techniques and Its Application to Quantitative Phosphate Sensing in Human Blood Serum

We herein report an organic field-effect transistor (OFET) based chemical sensor for multi-oxyanion detection with pattern recognition techniques. The oxyanions ubiquitously play versatile roles in biological systems, and accessing the chemical information they provide would potentially facilitate fundamental research in diagnosis and pharmacology. In this regard, phosphates in human blood serum would be a promising indicator for early case detection of significant diseases. Thus, the development of an easy-to-use chemical sensor for qualitative and quantitative detection of oxyanions is required in real-world scenarios. To this end, an extended-gate-type OFET has been functionalized with a metal complex consisting of 2,2'-dipicolylamine and a copper(II) ion (CuII-dpa), allowing a compact chemical sensor for oxyanion detection. The OFET combined with a uniform CuII-dpa-based self-assembled monolayer (SAM) on the extended-gate gold electrode shows a cross-reactive response, which suggests a discriminatory power for pattern recognition. Indeed, the qualitative detection of 13 oxyanions (i.e., hydrogen monophosphate, pyrophosphate, adenosine monophosphate, adenosine diphosphate, adenosine triphosphate, terephthalate, phthalate, isophthalate, malonate, oxalate, lactate, benzoate, and acetate) has been demonstrated by only using a single OFET-based sensor with linear discriminant analysis, which has shown 100% correct classification. The OFET has been further applied to the quantification of hydrogen monophosphate in human blood serum using a support vector machine (SVM). The multiple predictions of hydrogen monophosphate at 49 and 89 μM have been successfully realized with low errors, which indicates that the OFET-based sensor with pattern recognition techniques would be a practical sensing platform for medical assays. We believe that a combination of the OFET functionalized with the SAM-based recognition scaffold and powerful pattern recognition methods can achieve multi-analyte detection from just a single sensor.

Gold dispersed hierarchical flower-like copper oxide microelectrodes for the sensitive detection of glucose and lactic acid in human serum and urine

Herein, we report self-supported gold dispersed copper oxide microflowers (Au@CuO MFs) on copper microelectrodes (CME) as a sensitive platform for the sensing of glucose and lactic acid in human serum...

Electrochemical Detection of Phosphate Ion in Body Fluids with a Magnesium Phosphate Modified Electrode

An electrochemical sensor for phosphate detection in body fluids was developed based on the hydration transition of magnesium hydrogen phosphate (newberyite, MgHPO₄·3H₂O). The sensor was fabricated through incubation of a multi-walled carbon nanotube/Nafion (MWCNT/Nafion) modified glassy carbon electrode (GCE) in magnesium phosphate solution, where MgHPO₄·3H₂O was self-assembled on the electrode surface (denoted as MgP/MWCNT/Nafion). An electrooxidation peak at 1.0 V vs. Ag/AgCl was observed when the as-prepared electrode was subjected to a differential pulse voltammetry (DPV) scan in the presence of phosphate in acetate solution. When the DPV scan was performed in 0.4 - 1.3 V vs. Ag/AgCl, a linear relationship was observed between the peak height and the phosphate concentration in the range from 0.01 to 25 μM in the presence of 0.1 mM Mg²⁺ in the acetate solution with a limit of detection of 32 nM. And the sensor was successfully applied for phosphate detection in human urine and saliva samples with recoveries of 94.7 - 104.4 and 96 - 103.3%, respectively.

Direct Electrochemical Sensing of Phosphate in Aqueous Solutions Based on Phase Transition of Calcium Phosphate

Electrochemical determination of phosphate in aqueous solutions attracts considerable interests in both biological and environmental fields. Because of the electrochemically inactive nature of phosphate, direct electrochemical detection of phosphate is still a highly challenging task. Herein, we reported a direct electrochemical approach for the determination of phosphate based on the oxidation of coordinated OH during the phase transition of calcium phosphates (CaPs). The mixture of amorphous CaPs and octacalcium phosphate (Ca₈(HPO₄)₂(PO₄)₄·5H₂O), which acts as the starting material for hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂), was self-assembled on a Nafion-modified glassy carbon electrode. The as-prepared electrode (CaPs/Nafion) showed a distinct oxidation peak at 1.0 V versus Ag/AgCl in phosphate solution. The peak heights were directly proportional to the concentration of phosphate from 0.1 to 10 μM in the presence of 1 mM Ca²⁺. After comprehensive characterization of the CaPs/Nafion electrode, it was understood that phosphate ions as a proton acceptor could stimulate the generation of coordinated OH from coordinated water (H₂O) in CaP. The addition of Ca²⁺ could magnify the coordinated H₂O source because of its hydration to H₂O. The CaPs/Nafion electrode also displayed good selectivity as the electrochemical oxidization response was not affected by up to 10 μM of potentially competitive species like CO₃^2-, NO₃^-, CH₃COO^-, SO₄^2-, and Cl^-. The results obtained in this work not only provided a new method for direct detection of phosphate in aqueous solution but also suggested that Ca²⁺ could be a promoter for electrochemical oxygen generation.