A Heparinase Sensor Based on a Ternary System of Hg2+-Heparin-Osmium Nanoparticles.

A visual assay for the detection of heparinase was developed on the basis of a ternary system of Hg2+-heparin-osmium nanoparticles (OsNPs). First, heparin-capped OsNPs (heparin-OsNPs) were synthesized by a facile reduction method using heparin as the protecting/stabilizing agent. The oxidase-like activity of heparin-OsNPs, however, turned out to be low, which somewhat limits their application. We discovered that Hg2+ can significantly/specifically boost the oxidase-like activity of heparin-OsNPs via electrostatic interaction. The oxidase-like activity of heparin-OsNPs toward the oxidation of the substrate, 3,3',5,5'-tetramethylbenzidine, by dissolved O2 was found to increase by 76-fold in the presence of Hg2+. More significantly, heparin in heparin-OsNPs could be specifically hydrolyzed into small fragments in the presence of heparinase, which resulted in the weakening of the oxidase-like activity of Hg2+/heparin-OsNPs. On the basis of these findings, a linear response of the sensor for heparinase was obtained in the range 20-1000 µg/L with a low detection limit (15 µg/L), which is comparable to those of other reported sensors. Further, the colorimetric sensor was employed for the detection of heparinase in human serum samples with satisfactory results. We speculate that combining such surface modification of the osmium nanozyme with a sensing element could be an interesting direction for promoting nanozyme research in medical diagnosis.

Accelerating the Peroxidase-Like Activity of Gold Nanoclusters at Neutral pH for Colorimetric Detection of Heparin and Heparinase Activity.

The peroxidase-like catalytic activity of gold nanoclusters (Au-NCs) is quite low around physiological pH, which greatly limits their biological applications. Herein, we found heparin can greatly accelerate the peroxidase-like activity of Au-NCs at neutral pH. The catalytic activity of Au-NCs toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2 was 25-fold increased in the presence of heparin at pH 7. The addition of heparin not only accelerated the initial catalytic rate of Au-NCs but also prevented the Au-NCs from catalyst deactivation. This allows the sensitive colorimetric detection of heparin at neutral pH. In the presence of heparinase, heparin was hydrolyzed into small fragments, weakening the enhancement effect of catalytic activity. On the basis of this phenomenon, the colorimetric determination of heparinase in the range from 0.1 to 3 µg·mL-1 was developed with a detection limit of 0.06 µg·mL-1. Finally, the detection of heparin and heparinase activity in diluted serum samples was also demonstrated.

Heparin triggered dose dependent multi-color emission switching in water: a convenient protocol for heparinase I estimation in real-life biological fluids.

Oligo(p-phenylenevinylene) based bis-pyridinium derivatives show 'ratiometric' detection of heparin in water. For the first time, we present a dose-dependent, multi-color emission switching in the presence of heparin. The reversible self-assembly of probes with heparin as the stimulus is also exploited for the screening of heparinase I enzyme.

A novel fluorescent nanosensor for detection of heparin and heparinase based on CuInS2 quantum dots.

In this work, a novel fluorescence "turn off-on" nanosensor for the determination of heparin and heparinase based on CuInS2 quantum dots (QDs) was established. CuInS2 QDs (modified by l-cysteine) featuring amino groups were directly prepared in aqueous solution via a hydrothermal synthesis method. The amino groups on the surface of CuInS2 QDs can interact with sulfate and carboxylate groups in heparin via electrostatic interactions and hydrogen bonding, which led the fluorescence of CuInS2 QDs to "turn-off". However, the heparin could be hydrolyzed into small fragments in the presence of heparinase, which resulted in the fluorescence of CuInS2 QDs being recovered. Therefore, the addition of heparinase to the heparin/CuInS2 QDs system activated the fluorescence of CuInS2 QDs to "turn-on" state. Thus, the determination of heparin and heparinase could be achieved by monitoring the fluorescence "turn off-on". Under the optimum conditions, there was a good linear relationship between I/I0 (I and I0 were the fluorescence intensity of CuInS2 QDs in the presence and absence of heparin, respectively) and heparin concentration in the range of 0.05-15 µmol L(-1) with the detection limit of 12.46 nmol L(-1). The linear detection for heparinase was in the range of 0.2-5 µg mL(-1) with the detection limit of 0.07 µg mL(-1). The proposed nanosensor was employed for the detection of heparin in fetal bovine serum samples with satisfactory results.

Development of both colorimetric and fluorescence heparinase activity assays using fondaparinux as substrate.

Because tumors and other diseases are characterized by increased heparanase levels, human heparanase is a promising drug target and diagnostic marker. Therefore, methods are needed to determine heparanase activity and to examine potential inhibitors. Because of substrate comparability, we used the bacterial enzyme heparinase II (heparinase) for the assay development. Usually the substrate of heparanase assays is heparan sulfate, which has several disadvantages. Because of that, we used fondaparinux, which is being cleaved by both heparanase and heparinase. Two concepts to detect its degradation were examined: measurement of anti-factor Xa activity of fondaparinux and its direct quantification with the fluorescent sensor polymer-H. Using fondaparinux as substrate, the anti-factor Xa assay was shsown to be appropriate to determine heparinase activity. The detection with polymer-H was easier and even faster to perform. Linearity was given with fondaparinux as well as heparan sulfate, and heparin as substrates, but fondaparinux turned out to be most suitable. By modifications (incubation time, fondaparinux concentration, and polymer-H concentration), the limit of quantification and the linear range can be adapted to the respective requirements. In conclusion, a simple, accurate, and robust heparinase assay was developed. It is suitable for heparinase quality control and testing heparinase inhibitors and could be adapted to heparanase.

Colorimetric heparinase assay for alternative anti-metastatic activity.

Heparanase has been previously associated with the metastatic potential, inflammation, and angiogenesis of tumor cells. Heparanase activity has been detected by means of UV absorption, radiolabeled substrates, electrophoretic migration, and heparan sulfate affinity assays. However, those methods have proven to be somewhat problematic with regards to application to actual biological samples, the accessibility of the immobilized substrates, experimental sensitivity, and the separation of degraded products. Rather than focusing on heparanase activity, then, we have developed a rapid, alternative colorimetric heparinase assay, on the basis of the recent finding that sulfated disaccharides generated from heparin by bacterial heparinase exhibit biological properties comparable to those from heparan sulfate by mammalian heparanase. In this study, the concentrations of porcine heparin and bacterial heparinase I were determined using a Sigma Diagnostics Kit. Morus alba was selected as a candidate through this assay system, and an inhibitor, resveratrol, was purified from its methanol extract. Its anti-metastatic effects on the pulmonary metastasis of murine B16 melanoma cells were also evaluated. Our findings suggest that this assay may prove useful as a diagnostic tool for heparinase inhibition, as an alternative anti-metastatic target.

Heparanase expression during normal liver development and following partial hepatectomy.

Heparan sulphate proteoglycans are major components of the liver extracellular matrix. Their cleavage by heparanase (endo-beta-glucuronidase) may thus be involved in liver-specific normal and pathological processes. Heparanase mRNA and protein were expressed during liver development but not in the mature healthy liver. A biphasic gain of heparanase expression, detected by immunostaining, western blotting, and real-time RT-PCR, was clearly noted following partial hepatectomy, peaking at 12 and 96-168 h and subsiding 2 weeks post-surgery. Expression of heparan sulphate gradually increased throughout the regeneration process. Unlike heparanase, baseline levels of matrix metalloproteinase-2 (MMP-2) were detected in the intact liver, increasing up to 4 days following partial hepatectomy and subsiding at day 10. Bands matching MMP-9 were absent prior to hepatectomy, but visible 2 h post-hepatectomy. Thioacetamide-induced liver fibrosis was associated with increased levels of MMP-9 and MMP-2, correlating with the severity of the disease. Elevated heparanase levels were noted in the early stages of fibrosis, with no further increase evident in rats exhibiting higher fibrotic grades. Taken together, these data suggest a role for heparanase during liver development and remodelling.

Quantitative bead assay for hyaluronidase and heparinase I.

A novel, simple, and sensitive assay was developed to monitor, quantitatively, the hyaluronidase and heparinase I-catalyzed cleavage of fluoresceinamine-labeled hyaluronic acid and heparin, respectively. The fluoresceinamine-labeled substrates were hydrophobically absorbed onto 4-microm polystyrene beads. In the presence of enzyme, the change in fluorescence output of the substrate-absorbed beads was monitored in a noncontinuous manner using a flow cytometer. Our results show that hyaluronidase and heparinase I can cleave their respective substrates on the beads in a concentration- and time-dependent manner. The assay is suitable for detecting the presence of these glycosaminoglycan-degrading enzymes in cell lysates, extracts, or purified fractions, for quantifying their amounts, and for investigating the activity of potential inhibitors.

Multiple heparanases are expressed in polymorphonuclear cells.

BACKGROUND: Heparan sulfate proteoglycans are complex cell surface molecules containing polysaccharides called heparan sulfate. Lysosomes, platelet granules, and neutrophils (polymorphonuclear cells) contain heparanases that degrade heparan sulfate. There are at least two groups of heparanases: connective tissue-activating-peptide (CTAP-III) and mammalian heparanase (hpa). The purpose of this study was to quantify the expression of both CTAP-III and hpa in neutrophils and their heparanase activity. MATERIALS AND METHODS: Neutrophils were isolated from whole blood, total RNA collected, and reverse transcriptase--polymerase chain reaction (RT-PCR) performed. Primers were designed for CTAP-III and hpa-1 sequences from GenBank. Neutrophil lysate underwent Western blot analysis (and quantification) with antibodies to the C-terminus of CTAP-III and the 50-kDa subunit of hpa1. Chromatography separated these components of lysate, which were then tested for heparanase activity. RESULTS: Both CTAP-III (281 bp) and hpa-1 (485 bp) messenger RNA (mRNA) were expressed equally by neutrophils with use of quantitative RT-PCR. By Western blot analysis, a CTAP-III-like protein was detected at 80 kDa, and hpa-1 was detected as a 50-kDa protein, with expression not significantly different (P > 0.05). Heparanase activity was significantly different (P < 0.0001) for the 50-kDa hpa-1 protein (1.51 x 10(-6) micromol/min) and the 80-kDa CTAP-III-like protein (0.85 x 10(-6) micromol/min). CONCLUSIONS: Human neutrophils express mRNA and protein for both a CTAP-III-like protein and hpa-1. Although expressed in similar quantity for mRNA and protein, Hpa-1 was more active as heparanase than the CTAP-III-like protein. With more than one class of heparanase in their granules, neutrophils may be able to modify different kinds of heparan sulfate chains.

Enzyme kinetics determined using calorimetry: a general assay for enzyme activity?

Two techniques for determining enzyme kinetic constants using isothermal titration microcalorimetry are presented. The methods are based on the proportionality between the rate of a reaction and the thermal power (heat/time) generated. (i) An enzyme can be titrated with increasing amounts of substrate, while pseudo-first-order conditions are maintained. (ii) Following a single injection, the change in thermal power as substrate is depleted can be continuously monitored. Both methods allow highly precise kinetic characterization in a single experiment and can be used to measure enzyme inhibition. Applicability is demonstrated using a representative enzyme from each EC classification, including (i) oxidation-reduction activity of DHFR (EC 1.5.1.3); (ii) transferase activity of creatine phosphokinase (EC 2.7.3.2) and hexokinase (EC 2.7.1.1); (iii) hydrolytic activity of Helicobacter pylori urease (EC 3.5.1.5), trypsin (EC 3.4.21.4), and the HIV-1 protease (EC 3.4.21.16); (iv) lyase activity of heparinase (EC 4.1.1.7); and (v) ligase activity of pyruvate carboxylate (EC 6.4.1.1). This nondestructive method is completely general, enabling precise analysis of reactions in spectroscopically opaque solutions, using physiological substrates. Such a universal assay may have wide applicability in functional genomics.