Potentiometric assay for acid and alkaline phosphatase

Polymer-enhanced peroxidase activity of ceria nanozyme for highly sensitive detection of alkaline phosphatase

Nanoceria have demonstrated a wide array of catalytic activity similar to natural enzymes, holding considerable significance in the colorimetric detection of alkaline phosphatase (ALP), which is a biomarker of various biological disorders. However, the issues of physiological stability and formation of protein corona, which are strongly related to their surface chemistry, limit their practical application. In this work, CeO2 nanoparticles characterized by enhanced dimensional uniformity and specific surface area were synthesized, followed by encapsulation with various polymers to further increase catalytic activity and physiological stability. Notably, the CeO2 nanoparticles encapsulated within each polymer exhibited improved catalytic characteristics, with PAA-capped CeO2 exhibiting the highest performance. We further demonstrated that the PAA-CeO2 obtained with enhanced catalytic activity was attributed to an increase in surface negative charge. PAA-CeO2 enabled the quantitative assessment of AA activity within a wide concentration range of 10 to 60 μM, with a detection limit of 0.111 μM. Similarly, it allowed for the evaluation of alkaline phosphatase activity throughout a broad range of 10 to 80 U/L, with a detection limit of 0.12 U/L. These detection limits provided adequate sensitivity for the practical detection of ALP in human serum.

Evaluation of Dexamethasone-Induced Osteoporosis In Vivo Using Zebrafish Scales

Glucocorticoid-induced osteoporosis (GIOP) is a major cause of secondary osteoporosis, and the pathogenic mechanisms of GIOP remain to be elucidated. Here, we show a rapid dexamethasone-induced osteoporosis animal model using zebrafish scales. Intraperitoneal injection of dexamethasone over a 5-day period suppressed the regeneration of scales. Furthermore, the circularity of the newly formed regenerated scales was also slightly reduced compared to that of the control group on day 5. The changes in bone-related enzymes, such as cathepsin K, tartrate-resistant acid phosphatase (TRAP) for bone resorption, and alkaline phosphatase (ALP) for bone formation, provide insight into the progression of bone diseases; therefore, we further developed a method to measure the activities of cathepsin K, TRAP, and ALP using zebrafish scales. We found that a lysis buffer with detergent at neutral pH under sonication efficiently helped extract these three enzymes with high activity levels. Interestingly, treatment with a dexamethasone injection produced considerably higher levels of cathepsin K activity and a lower Ca/P ratio than those in the control group, suggesting that dexamethasone increased osteoclast activity, with no significant changes in the activities of TRAP and ALP. Our GIOP model and enzyme assay method could help to design better treatments for GIOP.

A colorimetric alkaline phosphatase biosensor based on p-aminophenol-mediated growth of silver nanoparticles

Alkaline phosphatase (ALP) is an enzyme that catalyzes the dephosphorylation of proteins, nucleic acids, and biomolecules. It is a potential biomarker for diverse diseases such as breast cancer, osteopenia, and hepatobiliary. Herein, we developed a colorimetric sensor for the ALP assay based on its enzymatic activity to dephosphorylate the p-aminophenol phosphate (pAPP) into pAP. In a solution containing silver nanoparticles (AgNPs) and Ag⁺ ions prepared using a low concentration of NaBH₄, pAP mediates the growth of AgNPs by reducing the concentration of Ag⁺ ions to enhance the intensity of localized surface plasmon resonance as the pAPP cannot induce a reduction of the remaining Ag⁺ due to the masking of the hydroxyl with phosphate. The quantitative assay of the ALP was demonstrated via the colorimetric detection of the pAP-mediated growth of AgNPs in the presence of an ALP. The highly sensitive enzymatic growth of AgNPs provided a wider dynamic linear range of 0.5-225 U/L with a lower limit of detection of 0.24 U/L than that previously reported. The use of pAP resulted in excellent selectivity of the sensor for the ALP assay in human serum, yielding a high recovery rate and a high precision of 99.2 ± 1.5 % for the standard addition method.

Impact of manure on soil biochemical properties: A global synthesis

Manure application mitigates land degradation and improves soil fertility. Despite many individual studies on manure effects, a comprehensive overview of its consequences for a broad range of soil properties is lacking. Through a meta-analysis of 521 observations spanning the experiments from days after pulse addition up to 113 years with continues manure input, we quantified and generalized the average responses of soil biochemical properties depending on climate factors, management, soil, and manure characteristics. Large increase of pools with fast turnover (microbial carbon (C) and nitrogen (N): +88% and +84%, respectively) compared to stable organic matter pools (+27% for organic C, and +33% for total N) reflects acceleration of C and N cycles and soil fertility improvement. Activities of enzymes acquiring C-, energy-, N-, phosphorus- and sulfur were 1.3-3.3 times larger than those in soil without manure for all study durations included. Soil C/N ratio remained unaffected, indicating the stability of coupled C and N cycles. Microbial C/N ratio decreased, indicating a shift towards bacterial domination, general increase of C and N availability and acceleration of element cycling. Composted manure or manure without mineral fertilizers induced the greatest increase compared to non-composted manure or manure with mineral fertilizers, respectively, in most biochemical properties. The optimal manure application rate for adjusting proper soil pH was 25 Mg ha^-1 year^-1. Among manure types, swine manure caused the greatest increase of N-cycle-related properties: microbial N (+230%), urease (+258%) and N-acetyl-β-D-glucosaminidase (+138%) activities. Manure application strategies should avoid P and N losses and pollution via runoff, leaching or gaseous emissions due to fast mineralization and priming of soil organic matter. In conclusion, manure application favors C accumulation and accelerates nutrient cycling by providing available organic substances and nutrients and thus increasing enzyme activities.

Ultrasensitive Assay of Alkaline Phosphatase Based on the Fluorescent Response Difference of the Metal-Organic Framework Sensor

The assay of alkaline phosphatase (ALP) is important in clinical diagnosis because the abnormal expression of this enzyme is related to many serious diseases. In this work, using a luminescent metal-organic framework (MOF) as the sensor, a fluorescent method was developed for the activity assay of ALP. With nanoscale particle size, the prepared MOF sensor exhibited good dispersability and stable photoluminescence in aqueous suspension. The emission of this MOF is inert to p-nitrophenylphosphate (NPP) but could be efficiently quenched by its dephosphorylated product, p-nitrophenol. Taking advantage of this feature, this MOF was added to the system of ALP-catalyzed NPP dephosphorylation to transduce the proceeding of the reaction real-timely to the fluorescent signal. The enzyme activity could be calculated based on the recorded kinetic trace. This method presented a low detection limit (2 × 10-3 U L-1) and a wide quantification range (0.6-90 U L-1) in our experiments, showing its quantification capability challenges the best of current ALP analytical methods. As a practical application, our method was successfully applied to the ALP analysis in human serum samples.

Overview of Optical and Electrochemical Alkaline Phosphatase (ALP) Biosensors: Recent Approaches in Cells Culture Techniques

Alkaline phosphatase (ALP), which catalyzes the dephosphorylation process of proteins, nucleic acids, and small molecules, can be found in a variety of tissues (intestine, liver, bone, kidney, and placenta) of almost all living organisms. This enzyme has been extensively used as a biomarker in enzyme immunoassays and molecular biology. ALP is also one of the most commonly assayed enzymes in routine clinical practice. Due to its close relation to a variety of pathological processes, ALP's abnormal level is an important diagnostic biomarker of many human diseases, such as liver dysfunction, bone diseases, kidney acute injury, and cancer. Therefore, the development of convenient and reliable assay methods for monitoring ALP activity/level is extremely important and valuable, not only for clinical diagnoses but also in the area of biomedical research. This paper comprehensively reviews the strategies of optical and electrochemical detection of ALP and discusses the electrochemical techniques that have been addressed to make them suitable for ALP analysis in cell culture.

Novel "Turn-On" Fluorescent Probe for Highly Selectively Sensing Fluoride in Aqueous Solution Based on Tb3+-Functionalized Metal-Organic Frameworks

A Zr-based metal-organic framework (Zr-MOF) which has free carbonyl groups is synthesized successfully through mix-ligand strategy. Subsequently, Tb³⁺ is encapsulated into a Zr-MOF by postcoordinated modification. The Tb³⁺@Zr-MOF exhibits the characteristic emission of Tb³⁺ because of efficient sensitization through antenna effects. The Tb³⁺@Zr-MOF is further developed as a novel "turn-on" fluorescent probe to detect fluoride ions in aqueous solution. The results show that Tb³⁺@Zr-MOF exhibits excellent selectivity, high stability, low detection limits, and good anti-interference for sensitizing fluoride ions. In addition, the possible sensing mechanism that the induced luminescence properties may be attributed to Lewis acid-base interactions is discussed.

A study on the AMACR catalysed elimination reaction and its application to inhibitor testing

α-Methylacyl-CoA racemase (AMACR; P504S) catalyses a key step in the degradation of branched-chain fatty acids and is important for the pharmacological activation of Ibuprofen and related drugs. Levels of AMACR are increased in prostate and other cancers, and it is a drug target. Development of AMACR as a drug target is hampered by lack of a convenient assay. AMACR irreversibly catalyses the elimination of HF from 3-fluoro-2-methylacyl-CoA substrates, and this reaction was investigated for use as an assay. Several known inhibitors and alternative substrates reduced conversion of 3-fluoro-2-methyldecanoyl-CoA by AMACR, as determined by (1)H NMR. The greatest reduction of activity was observed with known potent inhibitors. A series of novel acyl-CoA esters with aromatic side chains were synthesised for testing as chromophoric substrates. These acyl-CoA esters were converted to unsaturated products by AMACR, but their use was limited by non-enzymatic elimination. Fluoride sensors were also investigated as a method of quantifying released fluoride and thus AMACR activity. These sensors generally suffered from high background signal and lacked reproducibility under the assay conditions. In summary, the elimination reaction can be used to characterise inhibitors, but it was not possible to develop a convenient colorimetric or fluorescent assay using 3-fluoro-2-methylacyl-CoA substrates.

A label-free conjugated polymer-based fluorescence assay for the determination of adenosine triphosphate and alkaline phosphatase

A sensor was developed based on the quenching effect of Cu²⁺ on PPESO₃ and the hydrolysis of ATP by ALP.

Potentiometric enzyme immunoassay using miniaturized anion-selective electrodes for detection

An enzyme-linked immunosorbent assay (ELISA) for prostate specific antigen (PSA) detection in human serum was developed based on the potentiometric detection of 6,8-difluoro-4-methylumbelliferone (DiFMU). The assays were carried out in anti-human PSA capture antibody modified microtiter plates (150 microL volume). After incubation in the PSA-containing serum samples, beta-galactosidase-labeled PSA tracer antibody was added. The beta-galactosidase label catalyzed the hydrolysis of 6,8-difluoro-4-methylumbelliferyl-beta-D-galactopyranoside (DiFMUG) and the resulting DiFMU(-) anion was detected by potentiometric microelectrodes with anion-exchanger membrane. The selectivity of the anion-exchanger electrode is governed by the lipophilicity of the anions in the sample. Since DiFMU(-) is much more lipophilic (log P = 1.83) than any of the inorganic anions normally present in the working buffers and occurs in its anionic form at the physiological pH (pK(a) = 4.19), it was chosen as the species to be detected. The potentiometric ELISA-based method detects PSA in serum with a linear concentration range of 0.1-50 ng/mL. These results confirm the applicability of potentiometric detection in diagnostic PSA assays. Owing to simple methodology and low cost, potentiometric immunoassays seem to offer a feasible alternative to the development of in vitro diagnostic platforms.

Potentiometric flow-injection system for determination of alkaline phosphatase in human serum

A flow-injection system for detection of alkaline phosphatase (ALP) activity in human serum samples has been developed. As a specific and inexpensive ALP substrate for this kinetic assay monofluorophosphate (MFP) was applied. For detection of fluoride ions, generated in the course of the biocatalytic hydrolysis of MFP, conventional fluoride ion-selective electrode based on LaF(3)-crystalline membrane was applied. After optimization the system allows analysis of human serum with high selectivity and relatively short time of analysis (5-6 samples h(-1)). Volume of serum required for analysis is 0.05 mL. The system is useful for determination of the enzyme activity in human serum samples at physiological and pathological levels as well as for detection of isoenzymatic forms of ALP.

Flow injection system for potentiometric determination of alkaline phosphatase inhibitors

A simple flow injection system for potentiometric detection of alkaline phosphatase (ALP) activity has been developed and adapted for determination of selected inhibitors of this enzyme. In this system monofluorophosphate (MFP) has been applied as a specific ALP substrate. The use of this substrate enables application of fluoride ion selective electrode (FISE) as a detector of the product of the enzyme catalyzed reaction. Moreover, chemical stability and low cost of MFP enables the use of the substrate as a component of the carrier. This way, fluoride ions contained in this substrate define and stabilize baseline signal generated by the detector. Effects from several potential ALP inhibitors and interfering species were studied and discussed. The system allows inhibitive detection of beryllium and vanadate ions at ppb levels with relatively high selectivity, short time of analysis and high throughput of the system (near 8 samples h(-1)).