Immunoreactive serum trypsin in diseases of the pancreas

Detection of factor Xa activity using giant magnetoresistive biosensors

BACKGROUND

As anticoagulants are widely used to treat patients with atrial fibrillation (AF) and other thrombotic conditions, it is necessary for physicians to determine whether the medication has been taken in emergencies. Among many anticoagulants, rivaroxaban has attracted attention due to its safety and convenience. Since rivaroxaban inhibits activated coagulation factor X (factor Xa), measuring factor Xa activity can determine the presence of rivaroxaban.

RESULTS

We report a magnetic biosensing platform capable of measuring the activity of factor Xa using peptide substrates conjugated with magnetic nanoparticles (MNPs). Due to the size of factor Xa, a new method of solution-phase assays was proposed for magnetic biosensing platforms to address issues with immobilized peptides on the sensors. This method was validated with factor Xa and trypsin, both of which are serine proteases. In the solution-phase assays, samples with either the enzymes of interest or no enzyme were simultaneously measured, and the activity of the enzyme was estimated using the difference between the measurements. Unlike conventional optical methods, our platform was capable of detecting the activity of factor Xa at 2 μg mL-1 with a 30 min sample incubation.

SIGNIFICANCE

The assay using giant magnetoresistive biosensors outperformed conventional optical techniques. This platform can facilitate the determination of the presence of rivaroxaban and assist physicians in deciding on appropriate treatments for patients.

NIR-Sensitive Squaraine Dye-Peptide Conjugate for Trypsin Fluorogenic Detection

Trypsin enzyme has gained recognition as a potential biomarker in several tumors, such as colorectal, gastric, and pancreatic cancer, highlighting its importance in disease diagnosis. In response to the demand for rapid, cost-effective, and real-time detection methods, we present an innovative strategy utilizing the design and synthesis of NIR-sensitive dye-peptide conjugate (SQ-3 PC) for the sensitive and selective monitoring of trypsin activity by fluorescence ON/OFF sensing. The current research deals with the design and synthesis of three unsymmetrical squaraine dyes SQ-1, SQ-2, and SQ-3 along with a dye-peptide conjugate SQ-3-PC as a trypsin-specific probe followed by their photophysical characterizations. The absorption spectral investigation conducted on both the dye alone and its corresponding dye-peptide conjugates in water, utilizing SQ-3 and SQ-3 PC respectively, reveals enhanced dye aggregation and pronounced fluorescence quenching compared to observations in DMSO solution. The absorption spectral investigation conducted on dye only and corresponding dye-peptide conjugates in water utilizing SQ-3 and SQ-3 PC, respectively, reveals not only the enhanced dye aggregation but also pronounced fluorescence quenching compared to that observed in the DMSO solution. The trypsin-specific probe SQ-3 PC demonstrated a fluorescence quenching efficiency of 61.8% in water attributed to the combined effect of aggregation-induced quenching (AIQ) and fluorescence resonance energy transfer (FRET). FRET was found to be dominant over AIQ. The trypsin-mediated hydrolysis of SQ-3 PC led to a rapid and efficient recovery of quenched fluorescence (5-fold increase in 30 min). Concentration-dependent changes in the fluorescence at the emission maximum of the dyes reveal that SQ-3 PC works as a trypsin enzyme-specific fluorescence biosensor with linearity up to 30 nM along with the limit of detection and limit of quantification of 1.07 nM and 3.25 nM, respectively.

Micelle-based fluorogenic sensing of trypsin: a sensitive method in pancreatic disease diagnosis

Protamine-mediated micellar aggregates, featuring an AIE-based fluorescent sensor, facilitate efficient detection of trypsin activity. This method enables the detection of trypsin at exceptionally low concentrations (0.01-0.1 μg mL-1) in urine, demonstrating its potential for early clinical diagnosis of trypsin-related pancreatic diseases.

Expanding the scope of self-assembled supramolecular biosensors: a highly selective and sensitive enzyme-responsive AIE-based fluorescent biosensor for trypsin detection and inhibitor screening

Trypsin, a pancreatic enzyme associated with diseases like pancreatic cancer and cystic fibrosis, requires effective diagnostic tools. Current detection systems seldom utilize macrocyclic molecules and tetraphenyl ethylene (TPE) derivative-based supramolecular assemblies, known for their biocompatibility and aggregation-induced emission (AIE) properties, for trypsin detection. This study presents an enzyme-responsive, AIE-based fluorescence 'Turn-On' sensing platform for trypsin detection, employing sulfated-β-cyclodextrin (S-βCD), an imidazolium derivative of TPE (TPE-IM), and protamine sulfate (PrS). The anionic S-βCD and cationic TPE-IM formed a strongly fluorescent supramolecular aggregation complex in an aqueous buffer. However, PrS suppresses fluorescence because of its strong binding affinity with S-βCD. The non-fluorescent TPE-IM/S-βCD/PrS supramolecular assembly system exhibits trypsin-responsive properties, as PrS is a known trypsin substrate. Trypsin restores fluorescence in the TPE-IM/S-βCD system through the enzymatic cleavage of PrS, correlating linearly with trypsin catalytic activity in the 0-10 nM concentration range. The limit of detection is 10 pM. This work contributes to the development of self-assembled supramolecular biosensors using charged TPE derivatives and β-cyclodextrin-based host-guest chemistry, offering an innovative fluorescence 'Turn-On' trypsin sensing platform. The sensing system is highly stable under various conditions, selective for trypsin, and demonstrates potential for biological analysis and disease diagnosis in human serum. Additionally, it shows promise for the screening of trypsin inhibitors.

Simple and sensitive fluorescence detection of trypsin with Cu2+-Bovine serum albumin complex as a peroxidase mimic

Trypsin is a serine protease playing a key role in regulating pancreatic exocrine function and can be applied as a marker for the diagnosis of pancreatitis. In this work, a convenient and sensitive fluorescent assay was developed toward trypsin. Hydrogen peroxide slowly oxidized a non-fluorescent o-phenylenediamine (OPD) into a fluorescent product 2,3-diaminophenothiazine (DAP) under the catalytic from copper ions. After the introduction of bovine serum albumin (BSA), the combination of BSA with copper ions formed a peroxidase mimic and significantly accelerated the reaction rate. As an efficient protease, trypsin cleaved the lysine and arginine residues in BSA. This destroyed the binding between Cu2+ and BSA, and brought in a reduction of the catalytic effect. The accompanying decrease in fluorescence provided a response to trypsin in the range of 0.01-600 ng/mL, with a detection limit of 0.007 ng/mL. The scheme had a good selectivity and was successfully applied to the detection of real samples.

Fluorescence-Based Portable Assays for Detection of Biological and Chemical Analytes

Fluorescence-based detection techniques are part of an ever-expanding field and are widely used in biomedical and environmental research as a biosensing tool. These techniques have high sensitivity, selectivity, and a short response time, making them a valuable tool for developing bio-chemical assays. The endpoint of these assays is defined by changes in fluorescence signal, in terms of its intensity, lifetime, and/or shift in spectrum, which is monitored using readout devices such as microscopes, fluorometers, and cytometers. However, these devices are often bulky, expensive, and require supervision to operate, which makes them inaccessible in resource-limited settings. To address these issues, significant effort has been directed towards integrating fluorescence-based assays into miniature platforms based on papers, hydrogels, and microfluidic devices, and to couple these assays with portable readout devices like smartphones and wearable optical sensors, thereby enabling point-of-care detection of bio-chemical analytes. This review highlights some of the recently developed portable fluorescence-based assays by discussing the design of fluorescent sensor molecules, their sensing strategy, and the fabrication of point-of-care devices.

Characterization of temporospatial distribution of renal tubular casts by nephron tracking after ischemia-reperfusion injury

Renal tubular casts originating from detached epithelial cells after ischemia-reperfusion injury (IRI) can obstruct tubules and negatively impact glomerular filtration rate. Using multiphoton imaging of 400-μm-thick kidney sections, the distribution of casts and morphometric measurement of tubules was performed along the entire nephron for the first time. Tubular nuclei are shed before cell detachment, and visually occlusive casts (grade 3) appeared at 12 h after IRI at the S3/thin descending limb (tDL) junction. Grade 3 casts peaked at 24 h after injury [present in 99% of S3, 78% of tDL, 76% of thin ascending limb (tAL), 60% of medullary thick ascending limb (mTAL), and 10% of connecting tubule segments]. Cast formation in the S3 correlated with selective loss of cell numbers from this tubule segment. By day 3, most mTALs and connecting tubules were cast free, whereas 72% of S3 tubules and 58% of tDLs still contained grade 3 casts. Although bulk phagocytosis of cast material by surviving tubular cells was not observed, mass spectrometry identified large numbers of tryptic peptides in the outer medulla, and trypsin levels were significantly increased in the kidney and urine 24 h after IRI. Administration of either antipain or camostat to inhibit trypsin extended cast burden to the S2, led to sustained accumulation of S3 casts after IRI, but did not affect cast burden in the mTAL or renal function. Our data provide detailed and dynamic mapping of tubular cast formation and resolution after IRI that can inform future interventions to accelerate cast clearance and renal recovery.NEW & NOTEWORTHY This detailed characterization of the dynamic distribution of dead cell debris in ischemically injured kidney tubules reveals which cells in the kidney are most severely injured, when and where tubular casts form, and when (and to a lesser extent, how) they are cleared.

Detection of Sub-Nanomolar Concentration of Trypsin by Thickness-Shear Mode Acoustic Biosensor and Spectrophotometry

The determination of protease activity is very important for disease diagnosis, drug development, and quality and safety assurance for dairy products. Therefore, the development of low-cost and sensitive methods for assessing protease activity is crucial. We report two approaches for monitoring protease activity: in a volume and at surface, via colorimetric and acoustic wave-based biosensors operated in the thickness-shear mode (TSM), respectively. The TSM sensor was based on a β-casein substrate immobilized on a piezoelectric quartz crystal transducer. After an enzymatic reaction with trypsin, it cleaved the surface-bound β-casein, which increased the resonant frequency of the crystal. The limit of detection (LOD) was 0.48 ± 0.08 nM. A label-free colorimetric assay for trypsin detection has also been performed using β-casein and 6-mercaptohexanol (MCH) functionalized gold nanoparticles (AuNPs/MCH-β-casein). Due to the trypsin cleavage of β-casein, the gold nanoparticles lost shelter, and MCH increased the attractive force between the modified AuNPs. Consequently, AuNPs aggregated, and the red shift of the absorption spectra was observed. Spectrophotometric assay enabled an LOD of 0.42 ± 0.03 nM. The Michaelis-Menten constant, KM, for reverse enzyme reaction has also been estimated by both methods. This value for the colorimetric assay (0.56 ± 0.10 nM) is lower in comparison with those for the TSM sensor (0.92 ± 0.44 nM). This is likely due to the better access of the trypsin to the β-casein substrate at the surface of AuNPs in comparison with those at the TSM transducer.

Low serum trypsinogen levels in chronic pancreatitis: Correlation with parenchymal loss, exocrine pancreatic insufficiency, and diabetes but not CT-based cambridge severity scores for fibrosis

BACKGROUND

Chronic pancreatitis (CP) is a complex inflammatory disorder of the pancreas affecting acinar cells, duct cells, islet cells and inflammatory cells including fibrosis-producing stellate cells. Serum trypsinogen is a biomarkers of acinar cell function.

AIM

To define the degree of correlation between low trypsinogen levels as a marker of acinar cell function and variable features of CP.

METHODS

Serum samples from previously ascertained and well phenotyped case and control subjects from the North American Pancreatitis Study II (NAPS2) were used to measure serum trypsinogen levels in a commercial laboratory. Control samples were used to define normal ranges and compared with levels in CP patients with defined features.

RESULTS

A final cohort of 279 CP patients and 262 controls from the NAPS2 studies were evaluated. In controls trypsinogen had a mean of 34.96 ng/ml and SD = 11.99. Cut-off values for low trypsinogen ranged from <20 to 10 ng/ml and very low trypsinogen at <10 ng/ml. Compared to controls, CP was associated with very low trypsinogen levels (p < 0.0001). Within CP, very low trypsinogen levels correlated with parenchymal loss (pancreatic surgery [p < 0.05]; atrophy with calcifications, [p < 0.001]), EPI (p < 0.01, trend p < 0.001) and diabetes (trend p < 0.01) but not CT-based criteria for fibrosis (pancreatic duct dilation, irregularity, strictures).

CONCLUSIONS

Very low serum trypsinogen levels correlate with measures of acinar cell loss including surgical resection, atrophic-calcific CP, diabetes and functional symptoms EPI but not duct morphology criteria. Serum trypsinogen levels correlate with decreased acinar cell function and therefore have biomarker utility clinical management.

Remote biosensor for the determination of trypsin by using nanoporous anodic alumina as a three-dimensional nanostructured material

The determination of trypsin in the human real sample is a routine medical investigation to assess the pancreatic disease. Herein, we fabricated an interferometric reflectance spectroscopy based biosensor for the determination trypsin. For this purpose, urease and fluorescein 5(6)-isothiocyanate (FLITC) were immobilized on the nanoporous anodic alumina (NAA). The operation principle of the proposed biosensor is based on the change in the pH of the solution during the reaction of urease and urea and therefore change in the light-absorbing ability of FLITC in the presence of trypsin. The reaction of the urease enzyme with urea increased the pH of the solution because of producing ammonia. This increase in the pH of solution increased the light-absorbing ability of the immobilized FLITC on NAA and therefore the intensity of the reflected light from the NAA to the charge-coupled device detector decreased. In the presence of trypsin, the catalytic activity of immobilized urease on NAA decreased. This decrease in the activity of urease enzyme consequent on the decrease in the amount of the generated ammonia. Therefore, the immobilized FLITC on the NAA did not absorb more light and consciously, the intensity of the light reflected light into the detector increased. The proposed biosensor exhibited a good response to the concentration of trypsin in the range of 0.25–20 μg.mL⁻¹ with the limit of detection of 0.06 μg.mL⁻¹.

Function tests in the diagnosis of chronic pancreatitis. Critical evaluation

Direct pancreatic function tests, such as the secretin-pancreozymin test and the Lundh test, are--by direct measurement of the contents of duodenal secretion following exogenous (hormonal) or endogenous (test meal) stimulation--the best way to assess exocrine pancreatic function. However, these tests are time-consuming, invasive, and expensive, and therefore their use is limited to specialized centers only. Several studies have shown that indirect pancreatic function tests are a practicable alternative to direct pancreatic function tests for diagnosing exocrine pancreatic insufficiency. They allow staging of the disease and thereby facilitate comparison of different studies. They are also useful in some cases for determining whether pancreatic enzyme replacement therapy is necessary or not. In contrast to morphological procedures, they involve neither side effects, risks for the patient, nor complications for patients, investigators, and laboratory staff alike. The procedures being standardized, the test results depend to a lesser extent on the experience of the investigator, and more on the selection of and the instructions to the patient, and to some extent, on the severity of the exocrine pancreatic insufficiency. Like all pancreatic function tests, the indirect tests do not give a clue to etiology nor help investigators to differentiate between pancreatic insufficiency owing to chronic pancreatitis and that owing to pancreatic cancer. The role of pancreatic function tests in diagnosing early chronic pancreatitis in comparison to morphological examinations remains to be established.

Serum cathodic trypsin-like immunoreactivity, pancreatic lipase, and pancreatic isoamylase as diagnostic tests of chronic pancreatitis or pancreatic steatorrhea

We compared serum concentrations of cathodic trypsin-like immunoreactivity, pancreatic lipase, and pancreatic isoamylase as diagnostic tests of chronic pancreatitis (and of pancreatic steatorrhea in the 41 patients with steatorrhea) in 105 patients (57 men, 48 women) consecutively investigated because of clinical suspicion of chronic pancreatitis. Chronic pancreatitis (36 patients), pancreatic steatorrhea (24 patients), and other diseases were diagnosed without knowledge of the serum levels of the three enzymes. When evaluated by means of receiver operating characteristic curves, no differences were found in diagnostic performance of the enzymes with regard to chronic pancreatitis or pancreatic steatorrhea. The sensitivity and specificity for recognition of chronic pancreatitis ranged from 0.306 to 0.444 and from 0.942 to 0.986 when the discrimination values were chosen to give highest efficiencies. The similar ranges for pancreatic steatorrhea were 0.500-0.708 and 0.882-0.941. In conclusion, none of the three enzymes had any advantage over the others as diagnostic tests of chronic pancreatitis or of pancreatic steatorrhea. Only positive test results have clinical importance because of the low sensitivities of the three enzymes.

Trypsin/creatinine clearance ratio and serum immunoreactive trypsin in digestive and pancreatic diseases

The behavior of trypsin/creatinine clearance ratio (Ctr/Ccr) and serum immunoreactive trypsin (IRT) was evaluated in a total of 168 subjects with pancreatic cancer, chronic pancreatitis and non-pancreatic digestive diseases. Amylase/creatinine clearance ratio (Cam/Ccr) and serum amylase levels were also evaluated in order to establish their possible relationship with Ctr/Ccr and IRT values. Elevated Ctr/Ccr and IRT values were observed in several patients with pancreatic cancer and chronic pancreatitis. Abnormal IRT and Ctr/Ccr values were found in 28.2 and 4% of non-pancreatic digestive diseases, respectively. IRT and amylase serum levels showed consensual modifications, while Ctr/Ccr showed a behavior different from that of Cam/Ccr. Liver damage seems to play a role in increasing serum IRT levels of patients without pancreatic involvement, while the increased Ctr/Ccr seems to depend on other factors, for instance renal tubular dysfunction.

Serum elastase 1 in chronic pancreatic disease

Elastase 1 and immunoreactive trypsin were assessed by a RIA technique in the sera of 29 control subjects, 24 pancreatic cancer patients, 22 patients with chronic pancreatitis and 31 with extra-pancreatic diseases to ascertain and compare their usefulness in chronic pancreatic disease diagnosis. Increased levels of elastase 1 were detected in 60.9% of pancreatic cancer and in 61.1% of chronic pancreatitis patients; low values were found in only two subjects with pancreatic disease. A close correlation between the two enzymes was found in patients suffering from pancreatic cancer and chronic pancreatitis. These data suggest that serum elastase 1, as well as immunoreactive trypsin, is of limited value in chronic pancreatic disease diagnosis; increased levels of the two enzymes always occur simultaneously; low immunoreactive trypsin values together with normal elastase 1 serum levels are detectable in a number of patients with chronic pancreatitis and severe exocrine insufficiency.

Cathodic trypsin-like immunoreactivity in serum: influence of sex, age, renal function, food and diurnal variation

Radioimmunologically determined cathodic trypsin-like immunoreactivity (TLI) in serum was positively correlated with age (Spearman's rho = 0.40, p less than 0.001) and negatively correlated with estimated creatinine clearance (Spearman's rho = -0.31, p less than 0.01) in healthy adults (37 women, 27 men) under standard conditions. Women had higher TLI concentrations than men (median value 358 micrograms trypsin standard/l compared with 283 micrograms trypsin standard/l, p less than 0.02). A clinically significant uptake of cathodic trypsin from the intestine to the blood is not likely because no change was found in serum concentrations of TLI and the two major protease inhibitors (alpha 1-antitrypsin and alpha 2-macroglobulin) one hour after a standard meal. No diurnal variation of TLI in serum was found in a group of 12 healthy subjects. The results indicate that due consideration must be given to sex, age and renal function of the persons used in reference groups for TLI determination.

Variations with age of immunoreactive serum trypsin: higher reference ranges in "healthy" elderly people

According to the literature, the mean values of immunoreactive serum trypsin (IRT) (RIA-gnost Hoechst) in controls vary considerably between 150 and 283 ng/ml. The reasons for these variations are unknown. The purpose of the present investigation was to study the variations of IRT in relation to age in adults. We studied 124 hospital controls, who were without evidence of pancreatic disease or renal insufficiency and who varied in age between 17 and 84 years. Utilizing the kit of Hoechst, IRT was determined in fasting serum specimens. The mean (+/- SD) in patients over 60 years was 469.6 +/- 197.4 ng/ml, in contrast to 309.1 +/- 118.9 ng/ml (30-59 years) and 209.7 +/- 80.7 (less than 30 years). Of cases over 60 years 36.5% had elevated IRT levels above 500 ng/ml. In 25 cases over 60 years no correlation was found between IRT levels and creatinine clearance and in eight of ten cases of this group with high IRT (greater than 500 ng/ml) the serum pancreatic isoamylase levels were normal. The data indicate that in the diagnosis of pancreatic disease the higher reference ranges in the elderly people have to be taken into account. The age-related higher reference ranges seem not to be due to subclinical renal disease nor to clinically evident pancreatic disease.

Enteropancreatic circulation of trypsin in man

Following the intraduodenal installation of purified 125I-labeled human trypsin up to about 4--6% of the label was measured after 15--30 min in blood plasma and found to separate in a dextran-gel filtration system similar to purified human trypsin (-125I) after incubation with human serum. About 1% of the installed trypsin-(-125I)-dose was found already after 20 min in 100 ml of aspirated pancreatic secretion and later on also in the duodenal content. The results support the concept of the existence of an enteropancreatic circulation of trypsin also in man and explain in part the low to non-detectable levels of immunoreactive serum trypsin observed in patients with exocrine pancreatic insufficiency.