Matrix effects on an antigen immobilized format for competitive enzyme immunoassay of salivary testosterone

Metal-organic framework-based nanomaterials as opto-electrochemical sensors for the detection of antibiotics and hormones: A review

Increasing trace levels of antibiotics and hormones in the environment and food samples are concerning and pose a threat. Opto-electrochemical sensors have received attention due to their low cost, portability, sensitivity, analytical performance, and ease of deployment in the field as compared to conventional expensive technologies that are time-consuming and require experienced professionals. Metal-organic frameworks (MOFs) with variable porosity, active functional sites, and fluorescence capacity are attractive materials for developing opto-electrochemical sensors. Herein, the insights into the capabilities of electrochemical and luminescent MOF sensors for detection and monitoring of antibiotics and hormones from various samples are critically reviewed. The detailed sensing mechanisms and detection limits of MOF sensors are addressed. The challenges, recent advances, and future directions for the development of stable, high-performance MOFs as commercially viable next-generation opto-electrochemical sensor materials for the detection and monitoring of diverse analytes are discussed.

Quantitative Determination of Nitrofurazone Metabolites in Animal-Derived Foods Based on a Background Fluorescence Quenching Immunochromatographic Assay

Due to their facile synthesis and friendly functionalization, gold nanoparticles (AuNPs) have been applied in all kinds of biosensors. More importantly, these biosensors, with the combination of AuNPs and immunoassay, are expected to be used for the detection of different compounds with low concentrations in complex samples. In this study, a AuNPs-labeled antibody immunoprobe was prepared and combined with a fluorescence-quenching principle and a background fluorescence-quenching immunochromatographic assay (bFQICA), achieving rapid on-site detection. By using a portable fluorescence immunoquantitative analyzer and a QR code with a built-in standard curve, the rapid quantitative determination for nitrofurazone metabolite of semicarbazide (SEM) in animal-derived foods was realized. The limits of detection (LODs) for bFQICA in egg, chicken, fish, and shrimp were 0.09, 0.10, 0.12, and 0.15 μg kg⁻¹ for SEM, respectively, with the linear range of 0.08–0.41 μg L⁻¹, the recoveries ranging from 73.5% to 109.2%, and the coefficient of variation <15%, only taking 13 min for the SEM detection. The analysis of animal-derived foods by bFQICA complied with that of liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Salivary calprotectin is elevated in patients with active inflammatory bowel disease

OBJECTIVES

To assess the concentration of calprotectin, a heterodimer of S100A8 and S100A9 implicated in inflammatory bowel disease (IBD), in saliva of IBD patients compared to controls.

METHODS

Unstimulated and stimulated saliva, and serum was collected from 23 IBD patients with active intestinal inflammation, verified by endoscopy. Fifteen patients were re-sampled after treatment. Saliva was collected from 15 controls for protocol validation and group comparisons. Calprotectin concentrations were measured by enzyme-linked immunosorbent assay, correlated to clinical data/indexes and routine laboratory parameters.

RESULTS

Calprotectin was 4.0-fold (median) elevated in stimulated saliva of IBD patients compared to controls and tended to be elevated in unstimulated saliva (P = 0.001, P = 0.090). Crohn's (CD) patients had significantly elevated calprotectin in both unstimulated and stimulated saliva compared to controls (P = 0.011, P = 0.002). Newly diagnosed, treatment naïve CD patients had 8.2-fold (median) higher calprotectin concentrations in unstimulated saliva and 1.5-fold in stimulated saliva, compared to CD patients with established disease (P = 0.059, P = 0.019). Calprotectin decreased in serum of IBD patients after treatment (P = 0.011), and in unstimulated saliva of newly diagnosed, treatment naïve CD patients (P = 0.046, P = 0.028).

CONCLUSION

Salivary calprotectin is elevated in IBD, which suggests subclinical inflammatory responses in the oral cavity as a manifestation of IBD.

Assessment of free testosterone concentration

Testosterone (T) is strongly bound to sex hormone binding globulin and measurement of free T may be more appropriate than measuring total serum T, according to the free hormone theory. This view remains controversial and it has its detractors who claim that little extra benefit is gained than simply measuring total T, but it is endorsed by recent clinical practice guidelines for investigation of androgen disorders in both men and women. Free T measurement is very challenging. The gold standard equilibrium dialysis methods are too complex for use in routine clinical laboratories, assays are not harmonized and consequently there are no common reference intervals to aid result interpretation. The algorithms derived for calculating free T are inaccurate because they were founded on faulty models of testosterone binding to SHBG, however they can still give clinically useful results. To negate the effects of differences in binding protein constants, some equations for free T have been derived from accurate measurement of testosterone in large population studies, however a criticism is that the equations may not hold true in different patient populations. The free androgen index is not recommended for use in men because of inaccuracy at extremes of SHBG concentration, and in women it can also give inaccurate results when SHBG concentrations are low. If the free hormone hypothesis is to be believed, then calculated free testosterone may offer the best way forward but better equations are needed to improve accuracy and these should be derived from detailed knowledge of testosterone binding to SHBG. There is still much work to be done to improve harmonization of T and SHBG assays between laboratories because these can have a profound effect on the equations used to calculate free testosterone.

Salivary estradiol as a surrogate marker for serum estradiol in assisted reproduction treatment

INTRODUCTION

Controlled ovarian hyper-stimulation for in vitro fertilization or intra cytoplasmatic sperm injection necessitates close monitoring using ultrasound and estradiol measurements. Monitoring is also important to prevent or limit the severity of ovarian hyper stimulation syndrome, an iatrogenic and potentially life-threatening complication. Self-operated endovaginal telemonitoring has been shown to offer an attractive and less costly alternative to classic consultation and saliva estradiol measurements could be a stress-free and practical alternative to serial blood determinations. Objectives were to evaluate whether saliva can be a surrogate marker for serum estradiol and its potential applicability in assisted reproduction treatment monitoring.

MATERIAL AND METHODS

Serial blood and saliva samples were collected from 31 patients undergoing ovarian hyper-stimulation. All patients were followed-up using in-house serial vaginal sonograms and immunoassay serum estradiol measurements. Afterwards estradiol was determined in saliva and serum by LC-MS/MS. For a subset equilibrium dialysis and measurement of free serum estradiol was performed.

RESULTS

About 1% of estradiol is present in serum in its free, unbound, form. Salivary estradiol correlates well to both serum free estradiol and serum total estradiol (r=0.80). The concentration of salivary estradiol corresponds to the unbound concentration in serum. The dynamics observed in serum monitoring during treatment are closely mimicked in saliva. ROC analysis on the current limited dataset suggested a saliva cut-off of 22pg/mL (81pmol/L) could help predict risk for OHSS.

CONCLUSIONS

Salivary E2 can be considered a surrogate marker for free serum estradiol and total serum estradiol in assisted reproduction treatment. Additionally there might be a role as a prediction marker for OHSS although this finding has to be validated in larger datasets.

Highly Selective Capture Surfaces on Medical Wires for Fishing Tumor Cells in Whole Blood

The detection of circulating tumor cells (CTCs) in the blood of cancer patients is a challenging task. CTCs are, especially at the early stages of cancer development, extremely rare cells hidden in a vast background of regular blood cells. We describe a new strategy for the isolation of CTCs from whole blood. The key component is a medical wire coated with a multilayer assembly that allows highly specific capture of EpCAM (epithelial cell adhesion molecule) positive CTCs from blood. The assembly is generated in a layer-by-layer fashion through photochemically induced C,H insertion reactions and consists of a protective layer, which shields the contacting solution from the metal, a protein resistant layer, which prevents nonspecific interactions with proteins and a layer containing the EpCAM antibodies. In vitro experiments show that these surfaces can capture tumor cells from whole blood with enrichment factors (specifically vs nonspecifically bound cells) of up to about 3000 compared to the number of leucocytes in the blood. The purity of the isolated cells is greater than 90%. After "fishing" them from the blood, the cells, still bound to the wire, can be genetically analyzed. This demonstrates that this strategy might prove useful for next generation sequencing.

Isolation, characterization, and identification of proteins interfering with enzyme-linked immunosorbent assay of antibiotics in fish matrix

The interaction between some proteins and immune globulin has been confirmed as an important source of matrix interference with the immunoassay of fishery products, but detailed biochemical properties of these proteins have not been indicated. Two interference-inducing proteins (42 and 36 kD) in flounder were isolated, characterized, and identified. Their influences on the immunoassay of norfloxacin were confirmed by western blotting and enzyme-linked immunosorbent assay. The pI value and pH stability of the two proteins were also investigated. Using LC-MS/MS, the two proteins were identified as fructose-bisphosphate aldolase, and such results were partly verified by the aldolase activity of the 42 and 36 kD isolates. Considering the prevalence of these proteins (as multi-functional aldolase of muscles) in foods, these results would help to further understand the matrix effects in various immunoassays as well as the development of effective techniques to improve the efficiency of immunoassays.

A microfluidic indirect competitive immunoassay for multiple and sensitive detection of testosterone in serum and urine

We demonstrate a microfluidic-based indirect competitive chemiluminescence enzyme immunoassay (MIC) for multiple, sensitive, reliable and rapid detection of testosterone in human serum and urine samples. As MIC can detect biomarkers in a cost-effective and easy-to-operate manner, it may have great potential for clinical diagnosis and point-of-care testing (POCT).

A critical evaluation of salivary testosterone as a method for the assessment of serum testosterone

Although salivary testosterone (T) is often used in clinical studies accuracy is mostly questionable. State of the art data for men is sparse and for women absent. Our objective was to perform a critical evaluation of salivary T (Sal-T) as a method for indirect assessment of serum T using state of the art methods. Saliva was collected via 'Salivette' and 'passive drooling' methods. Sal-T and free T in serum after equilibrium dialysis were measured by LC-MS/MS RESULTS: Evaluation of Sal-T results versus free T by equilibrium dialysis (ED-T) for men gave: 'Salivette' Sal-T=0.05+0.88x ED-T, r=0.43; 'passive drooling' Sal-T=0.17+0.91x ED-T r=0.71. In women, correlation was comparable but values are higher than free T: 'passive drooling' Sal-T=0.12+2.32x ED-T, r=0.70. The higher than expected T values in saliva, appear to be explained by T binding to salivary proteins. Iso-electric focusing of saliva proteins, followed by fractionation and LC-MS/MS assay of T showed marked testosterone peaks at pH 5.3 and 8.4, providing evidence for T binding in saliva to proteins such as albumin and proline rich protein (PRP).

CONCLUSIONS

Passive drooling is the collection method of choice for testosterone in saliva. Sal-T is not directly comparable to serum free T due to T binding to saliva proteins, which substantially affects the low Sal-T in women but not the higher Sal-T in healthy adult men.