The influence of serum uric acid on renal function in patients with calcium or uric acid stone: A population-based analysis

OBJECTIVES

To determine the influence of serum uric acid (UA) levels on renal impairment in patients with UA stone.

MATERIALS AND METHODS

We retrospectively analyzed 463 patients with calcium oxalate and/or calcium phosphate stones (CaOx/CaP), and 139 patients with UA stones. The subjects were divided into the serum UA-high (UA ≥ 7.0 mg/dL) or the UA-low group (UA < 7.0 mg/dL). The control group comprised 3082 community-dwelling individuals that were pair-matched according to age, sex, body mass index, comorbidities, hemoglobin, serum albumin, and serum UA using propensity score matching. We compared renal function between controls and patients with UA stone (analysis 1), and between patients with CaOx/CaP and with UA stone (analysis 2). Logistic regression analysis was used to evaluate the impact of the hyperuricemia on the development of stage 3 and 3B chronic kidney disease (CKD) (analysis 3).

RESULTS

The renal function was significantly associated with serum UA levels in the controls and patients with CaOx/CaP and UA stones. In pair-matched subgroups, patients with UA stone had significantly lower renal function than the control subjects (analysis 1) and patients with CaOx/CaP stones (analysis 2) regardless of hyperuricemia. Multivariate logistic regression analysis revealed that patients with UA stone, CaOx/CaP, hyperuricemia, presence of cardiovascular disease, higher body mass index, older age and lower hemoglobin had significantly higher risk of stage 3 and 3B CKD (analysis 3).

CONCLUSION

Patients with UA stones had significantly worse renal function than controls and CaOx/CaP patients regardless of hyperuricemia. Urolithiasis (CaOx/CaP and UA stone) and hyperuricemia had an association with impaired renal function. Our findings encourage clinicians to initiate intensive treatment and education approaches in patients with urolithiasis and/or hyperuricemia in order to prevent the progression of renal impairment.

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with dinoflagellates (Symbiodinium sp.). We argue, however, that the direct negative effects on the symbiosis are not necessarily caused by the nutrient enrichment itself but by the phosphorus starvation of the algal symbionts that can be caused by skewed nitrogen (N) to phosphorus (P) ratios. We exposed corals to imbalanced N:P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals. In contrast, the corals tolerated an undersupply with nitrogen at high phosphate concentrations without negative effects on symbiont photosynthesis, suggesting a better adaptation to nitrogen limitation. Transmission electron microscopy analysis revealed that the signatures of ultrastructural biomarkers represent versatile tools for the classification of nutrient stress in symbiotic algae. Notably, high N:P ratios in the water were clearly identified by the accumulation of uric acid crystals.

Double injection/single detection asymmetric flow injection manifold for spectrophotometric determination of ascorbic acid and uric acid: Selection the optimal conditions by MCDM approach based on different criteria weighting methods

A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe³⁺ in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe²⁺/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50-5.00 and 0.50-4.00mgL^-1 for AA and UA, respectively. The 3σ detection limits were 0.07mgL^-1 for AA and 0.12mgL^-1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.

Kidney Function in Patients With Different Variants of Beta-Thalassemia

INTRODUCTION

Renal involvement is a rare complication of β-thalassemia. Both tubular and glomerular dysfunction might occur in these patients. The aim of this study was to evaluate and compare kidney function in the major, intermedia, and minor variants of β-thalassemia.

MATERIALS AND METHODS

Renal tubular and glomerular function of 72 patients with β-thalassemia (25 major, 23 intermedia, and 24 minor) were evaluated. Patients older than 40 years and those with chronic kidney disease, diabetes mellitus, congestive heart failure, associated infections, congenital anomalies of the kidney and urinary tract were excluded. Blood and urine samples were collected electrolytes and markers of kidney function.

RESULTS

Mean age at the time of study was significantly higher in the minor group. The majority of patients with thalassemia major were males. Hematuria and pyuria occurred in 4% to 8% of the patients. Serum level of all variables were within normal limits, with no significant difference between the three groups. Glomerular filtration rate was nonsignificantly higher in the major and intermedia groups, compared to the minor variant. A significantly lower urine phosphorus and uric acid excretion was noted with the minor variant. Urine phosphorus and uric acid excretion increased more frequently in the major and intermedia groups.

CONCLUSIONS

Tubular and glomerular functions appear to be well preserved in all variants of β-thalassemia.

Evaluation of copeptin and commonly used laboratory parameters for the differential diagnosis of profound hyponatraemia in hospitalized patients: 'The Co-MED Study'

OBJECTIVE

Hyponatraemia is common and its differential diagnosis is challenging. Commonly used diagnostic algorithms have limited diagnostic accuracy. Copeptin, the c-terminal portion of the precursor peptide of arginine vasopressin might help in the differential diagnosis of hyponatraemia.

DESIGN

Prospective multicentre observational study.

PATIENTS/METHODS

A total of 298 patients admitted with profound hypoosmolar hyponatraemia (Na < 125 mmol/l) were evaluated. Three experts uninvolved in the patients' care determined the aetiology of hyponatraemia after standardized diagnostic evaluation.

RESULTS

Hyponatraemia differential diagnoses were as follows: syndrome of inappropriate antidiuresis (SIAD), 106 patients (35·6%); 'diuretic-induced', 72 (24·2%); 'hypovolaemic', 59 (19·8%); 'hypervolaemic', 33 (11·1%); primary polydipsia (PP), 24 (8·1%); and cortisol deficiency, 4 (1·3%). Copeptin levels <3·9 pmol/l identified patients with PP with high specificity (91%). Further, copeptin levels >84 pmol/l were highly predictive for hypovolaemic hyponatraemia (specificity: 90%). Urinary sodium levels and copeptin/urinary sodium ratio in patients with SIAD were higher and lower as compared to other hyponatraemia aetiologies (P < 0·0001). However, the specificity to identify SIAD was moderate for both parameters (31% and 61%). Fractional uric acid excretion (FE_UA ) and fractional urea excretion (FE_urea ) were higher in patients with SIAD compared to other hyponatraemia aetiologies (both P < 0·0001). FE_urea values >55% and FE_UA values >12% had a specificity of 96% and 77% to detect patients with SIAD. These results remained similar after excluding patients taking diuretics.

CONCLUSIONS

Overall, there is only limited diagnostic utility of copeptin in the differential diagnosis of profound hyponatraemia. Very low copeptin levels are seen in patients with PP and highest copeptin levels in hypovolaemic hyponatraemia. To discriminate between SIAD and other hyponatraemia aetiologies, FE_urea and FE_UA levels are valuable irrespective of diuretics use.

Evaluation of carbon nanotube fiber microelectrodes for neurotransmitter detection: Correlation of electrochemical performance and surface properties

Fibers made of CNTs are attractive microelectrode sensors because they can be directly fabricated into microelectrodes. Different protocols for making CNT fibers have been developed, but differences in surface structure and therefore electrochemical properties that result have not been studied. In this study, we correlated the surface and electrochemical properties for neurochemical detection at 3 types of materials: CNT fibers produced by wet spinning with (1) polyethylenimine (PEI/CNT) or (2) chlorosulfonic acid (CA/CNT), and (3) CNT yarns made by solid-based CNT drawing. CNT yarns had well-aligned, high purity CNTs, abundant oxygen functional groups, and moderate surface roughness which led to the highest dopamine current density (290 ± 65 pA/cm²) and fastest electron transfer kinetics. The crevices of the CNT yarn and PEI/CNT fiber microelectrodes allow dopamine to be momentarily trapped during fast-scan cyclic voltammetry detection, leading to thin-layer cell conditions and a response that was independent of applied waveform frequency. The larger crevices on the PEI/CNT fibers led to a slower time response, showing too much roughness is detrimental to fast detection. CA/CNT fibers have a smoother surface and lower currents, but their negative surface charge results in high selectivity for dopamine over uric acid or ascorbic acid. Overall, small crevices, high conductivity, and abundant oxygen groups led to high sensitivity for amine neurotransmitters, such as dopamine and serotonin. Thus, different surfaces of CNT fibers result in altered electrochemical properties and could be used in the future to predict and control electrochemical performance.

Plasmonic Schirmer Strip for Human Tear-Based Gouty Arthritis Diagnosis Using Surface-Enhanced Raman Scattering

Biomarkers in tear fluid have attracted much interest in daily healthcare sensing and monitoring. Recently, surface-enhanced Raman scattering (SERS) has enabled highly sensitive label-free detection of small molecules. However, a highly stable straightforward tear assay with superior sensitivity is still under development in tear collection and analysis. Here we report a plasmonic Schirmer strip for on-demand, rapid, and simple identification of biomarkers in human tears. The diagnostic strip features gold nanoislands directly and evenly formed on the top surface of cellulose fibers, which maintain a hygroscopic nature for an efficient collection of tear production as well as provide plasmonic enhancement in SERS signals for identification of tear molecules. The uric acid in human tears was quantitatively detected at physiological levels (25-150 μM) by using SERS. The experimental results also clearly reveal a strong linear correlation between uric acid level in both human tears and blood for gouty arthritis diagnosis. This functional paper strip enables noninvasive diagnosis of disease-related biomarkers and healthcare monitoring using human tears.

Assessment of Uric Acid Level in the Saliva of Patients with Oral Lichen Planus

OBJECTIVE

The aim of this study was to evaluate the level of uric acid (UA) in saliva, which is considered to be an antioxidant defense biomarker against oxidative stress in patients with oral lichen planus (OLP).

SUBJECTS AND METHODS

In this case-control study, 25 OLP patients were included. The reticular form of OLP was verified by a clinical examination with Wickham striae, and other types (erosive, atrophic, ulcerative) were confirmed by histopathological assessment. Thirty healthy individuals matched for age and gender were selected as the control group. In both groups, the Navazesh technique was used to collect the unstimulated saliva. Then, the amount of UA was measured using a Cobas Mira autoanalyzer with a wavelength of 546 nm. The Student t test was used to analyze the data assuming a significance level at <0.05.

RESULTS

Of the 25 patients, the most common type of OLP was erosive (n = 11, 44%), and the most common site of OLP was seen as bilateral in the buccal mucosa (n = 12, 48%). The mean level of salivary UA was significantly lower in the patients with OLP (2.10 ± 0.19 mg/dL) in comparison with the control group (4.80 ± 0.29 mg/dL; p < 0.001).

CONCLUSION

In this study, OLP was associated with a decrease in UA levels in the saliva. Salivary UA as a biomarker could be used for monitoring and treating OLP.

[Dual-energy CT: new diagnostic possibilities]

Dual-energy CT (DECT) provides more information than a conventional CT scan. This new technique does not only provide morphological information, but also provides information about the chemical composition of tissues and substances, e.g. uric acid or calcium, based on material-specific differences in X-ray attenuation, leading to diagnostic improvement. Other benefits include reduced radiation dose, reduced use of contrast fluids due to better iodine detection and improved image quality. DECT fulfils a need in patients with a hypersensitivity to contrast agents, leads to less kidney damage, and avoids the necessity of more invasive diagnostic methods such as lumbar punctures. There are clinical applications in the fields of cardiovascular and pulmonary medicine, urology and musculoskeletal diagnostics. For example, DECT can display monosodium urate depositions in a non-invasive manner, so that the effectiveness of gout treatment can be monitored. Kidney stones, coronary plaques and pulmonary emboli can also be displayed on the basis of their material-specific X-ray attenuation.

[Etiopathogenic factors of the different types of urinary litiasis.]

In this review, we analyze the etiopathogenic principles of urinary lithiasis formation. In the kidney, calcifications that may cause renal lithiasis are produced as a consequence of processes that injury the urothelium at the papilla and Bellini's ducts. With the improvement of imaging techniques, mainly micro CT scan, it is possible to detect them and we may be able to anticipate to the formation of lithiasis. As we well know, there are different factors that influence the formation of the calculi depending on their composition. In calcium lithiasis it is key to review the modification of the categories of hypercalciuria, we currently distinguish two types instead of three, thanks to the fasting calcium/ creatinine ratio, differentiating absorptive hypercalciuria and fasting hypercalciuria. In the fasting hypercalciuria, it is important to emphasize the relationship between this factor and the loss of bone mineral density in patients with recurrent renal calcic lithiasis, so that in this kind of patients it is compulsory the study of bone metabolism by bone remodelling markers and bone densitometry. Regarding the other factors that participate in the formation of calcium lithiasis we should specially emphasize on hypercalciuria and its growing increase because of its relationship with obesity and metabolic syndrome, as well as hipocitraturia, present in an important percentage of patients and related in some cases with metabolic acidosis and osteopenia-osteoporosis too. In relation to uric acid lithiasis it should be highlighted that urinary pH is the most determinant factor and, therefore, its control and modifications would be paramount for prevention of this type of lithiasis. In the infectious lithiasis, the presence of germs that split urea is mandatory. They generate ammonia ions with the ability to injure the urothelium and to form magnesium ammonium phosphate lithiasis mainly. Regarding cystine lithiasis, rare, it was classically divided in three types and now passed to be classified in type A and B depending on the muted gene, and it is more useful to perform direct 24-hour urine measurement than screening tests which have low sensitivity. In general, we tried to give a comprehensive view of the various types of lithiasis emphasizing the most interesting clinical points for the urologist.

Allantoin Increases Cadmium Tolerance in Arabidopsis via Activation of Antioxidant Mechanisms

Plants apply various molecular, physiological and morphological strategies in response to undesirable environmental conditions. One of the possible responses which may contribute to surviving stressful conditions is the accumulation of ureides. Ureides are recognized as important nitrogen-rich compounds involved in recycling nitrogen in plants to support growth and reproduction. Amongst them, allantoin not only serves as a transportable nitrogen-rich compound, but has also been suggested to protect plants from abiotic stresses via minimizing oxidative damage. This work focuses on the effect of cadmium (Cd) on ureide metabolism in Arabidopsis, in order to clarify the potential role of allantoin in plant tolerance to heavy metals. In response to Cd treatment, allantoin levels increase in Arabidopsis thaliana, ecotype Col-0, due to reduced allantoinase (ALN) gene expression and enzyme activity. This coincides with increases in uricase (UO) transcripts. UO and ALN encode the enzymes for the production and degradation of allantoin, respectively. ALN-negative aln-3 Arabidopsis mutants with elevated allantoin levels demonstrate resistance to soil-applied CdCl₂, up to 1,500 μM. Although aln-3 mutants take up and store more Cd within their leaf tissue, they contain less damaging superoxide radicals. The protective mechanism of aln-3 mutants appears to involve enhancing the activity of antioxidant enzymes such as superoxide dismutase and ascorbate peroxidase.

Uric acid transporters hiding in the intestine

CONTEXT

Hyperuricaemia is known as an abnormally increased uric acid level in the blood. Although it was observed many years ago, since uric acid excretion via the intestine pathway accounted for approximately one-third of total elimination of uric acid, the molecular mechanism of 'extra-renal excretion' was poorly understood until the finding of uric acid transporters.

OBJECTIVE

The objective of this study was to gather all information related to uric acid transporters in the intestine and present this information as a comprehensive and systematic review article.

METHODS

A literature search was performed from various databases (e.g., Medline, Science Direct, Springer Link, etc.). The key terms included uric acid, transporter and intestine. The period for the search is from the 1950s to the present. The bibliographies of papers relating to the review subject were also searched for further relevant references.

RESULTS

The uric acid transporters identified in the intestine are discussed in this review. The solute carrier (SLC) transporters include GLUT9, MCT9, NPT4, NPT homolog (NPT5) and OAT10. The ATP binding cassette (ABC) transporters include ABCG2 (BCRP), MRP2 and MRP4. Bacterial transporter YgfU is a low-affinity and high-capacity transporter for uric acid.

CONCLUSION

The present review may be helpful for further our understanding of hyperuricaemia and be of value in designing future studies on novel therapeutic pathways.

Clinical Inquiry: How do clinical prediction rules compare with joint fluid analysis in diagnosing gout?

Clinical prediction rules effectively diagnose gout without joint fluid analysis. The American College of Rheumatology clinical prediction rules, the most accurate rules developed for research purposes, have a sensitivity of 92%, specificity of 89%, positive likelihood ratio of 8.36, and negative likelihood ratio of 0.09.

Different Contributions of Physical Activity on Arterial Stiffness between Diabetics and Non-Diabetics

BACKGROUND

We compared the contribution of physical activity to the change in arterial stiffness between patients with and without diabetes in ischemic heart disease.

METHODS

We studied 96 (diabetes) and 109 (without diabetes) patients with ischemic heart disease treated by percutaneous coronary intervention (PCI). Arterial stiffness was assessed by cardio-ankle vascular index (CAVI) at the first diagnosis of significant coronary ischemia and 6 months after PCI and optimal medical therapy. Physical activity was evaluated using the long form of the International Physical Activity Questionnaire (IPAQ).

RESULTS

CAVI values increased more for diabetic patients than for non-diabetic. The IPAQ scores did not differ between the two groups. During follow-up, CAVI values did not significantly change in either group. In diabetic patients, the CAVI score for 48 patients did not change (NC-group) and 48 patients improved (Improved-group). Physical activity scores were 937.9 ± 923.2 and 1524.6 ± 1166.2 in the NC- and Improved-groups, respectively. IPAQ scores and uric acid levels significantly affect CAVI improvement after adjusting for age, sex, baseline CAVI, total cholesterol, and estimated glomerular filtration rate.

CONCLUSION

Determining factors influencing CAVI improvement during follow-up were significantly different between patients with and without diabetes. IPAQ scores and uric acid levels were significantly correlated with CAVI changes.

Enzyme mediated synthesis of polypyrrole in the presence of chondroitin sulfate and redox mediators of natural origin

Polypyrrole (PPy) was synthesized by enzyme mediated oxidation of pyrrole using naturally occurring compounds as redox mediators. The catalytic mechanism is an enzymatic cascade reaction in which hydrogen peroxide is the oxidizer and soybean peroxidase, in the presence of acetosyringone, syringaldehyde or vanillin, acts as a natural catalysts. The effect of the initial reaction composition on the polymerization yield and electrical conductivity of PPy was analyzed. Morphology of the PPy particles was studied by scanning electron microscopy and transmission electron microscopy whereas the chemical structure was studied by X-ray photoelectron and Fourier transformed infrared spectroscopic techniques. The redox mediators increased the polymerization yield without a significant modification of the electronic structure of PPy. The highest conductivity of PPy was reached when chondroitin sulfate was used simultaneously as dopant and template during pyrrole polymerization. Electroactive properties of PPy obtained from natural precursors were successfully used in the amperometric quantification of uric acid concentrations. PPy increases the amperometric sensitivity of carbon nanotube screen-printed electrodes toward uric acid detection.

Cardiometabolic Profile Related to Body Adiposity Identifies Patients Eligible for Bariatric Surgery More Accurately than BMI

BACKGROUND

Eligibility criteria for bariatric surgery (BS) are based on BMI and the presence of major comorbidities. Our aim was to analyze the usefulness of body adiposity determination in establishing the indication for BS.

METHODS

In order to analyze the cardiometabolic risk according to eligibility criteria for BS, four groups were studied. Morbidly obese patients with BMI ≥ 40 kg/m(2) (n = 360), and obese subjects with BMI ≥ 35 kg/m(2) and at least one comorbidity (n = 431), represented two groups of patients meeting original NIH criteria for BS. A third group included two cohorts of patients with a high body fat (BF)% that do not meet the original NIH eligibility criteria for BS: patients with either a BMI <35 kg/m(2) or a BMI ≥ 35 kg/m(2) without comorbidities (n = 266, NEHF). Lean subjects by BMI were the reference group (n = 140). BMI, BF% and markers of insulin sensitivity, lipid profile, and cardiovascular risk were measured.

RESULTS

Individuals from the NEHF group exhibited increased HbA1c (P < 0.05) and decreased insulin sensitivity evidenced by a significant reduction in QUICKI (P < 0.001). Triglyceride concentrations were similarly increased (P < 0.05) in the three groups of obese patients. Uric acid concentrations were significantly elevated (P < 0.01) to a similar extent in the obese groups. Levels of the inflammatory marker CRP and hepatic enzymes were significantly increased in the three obese groups.

CONCLUSION

The present study provides evidence for the existence of an adverse cardiometabolic profile in subjects currently considered to be outside traditional NIH guidelines but exhibiting a highly increased adiposity. It is concluded that body composition analysis yields valuable information to be incorporated into indication criteria for BS and that adiposity may be an independent indicator for BS.

[Uroliths of dogs in Switzerland from 2003 to 2009]

Information on composition of uroliths collected between 2003 and 2009 from dogs in Switzerland and epidemiologic data of affected dogs are summarised in this paper. Of 490 stones analysed 44% were composed of calcium oxalate, 330% of struvite, 80% of silica, 7% of urate, 3% of cystine, 3% were mixed stones and 1% each were calcium phosphate and xanthine stones. Compared to other dogs, Norwich Terriers, Norfolk Terriers, Miniature Schnauzers, Miniature Pinscher and Yorkshire Terriers had a significantly increased risk to suffer from calcium oxalate stones, Dalmatians and Continental Bulldogs from urate stones and English Bulldogs from cystine stones. No breed had an increased risk of struvite or silica stones. Stones composed of silica were more prevalent in Switzerland compared to other countries and were more common in the eastern part than in the western part of Switzerland. This study shows that there are differences in occurrence and prevalence of uroliths between Switzerland and surveys of other countries.

Identification of mineral compositions in some renal calculi by FT Raman and IR spectral analysis

We present in this paper accurate and reliable Raman and IR spectral identification of mineral constituents in nine samples of renal calculi (kidney stones) removed from patients suffering from nephrolithiasis. The identified mineral components include Calcium Oxalate Monohydrate (COM, whewellite), Calcium Oxalate Dihydrate (COD, weddellite), Magnesium Ammonium Phosphate Hexahydrate (MAPH, struvite), Calcium Hydrogen Phosphate Dihydrate (CHPD, brushite), Pentacalcium Hydroxy Triphosphate (PCHT, hydroxyapatite) and Uric Acid (UA). The identification is based on a satisfactory assignment of all the observed IR and Raman bands (3500-400c m(-1)) to chemical functional groups of mineral components in the samples, aided by spectral analysis of pure materials of COM, MAPH, CHPD and UA. It is found that the eight samples are composed of COM as the common component, the other mineral species as common components are: MAPH in five samples, PCHT in three samples, COD in three samples, UA in three samples and CHPD in two samples. One sample is wholly composed of UA as a single component; this inference is supported by the good agreement between ab initio density functional theoretical spectra and experimental spectral measurements of both sample and pure material. A combined application of Raman and IR techniques has shown that, where the IR is ambiguous, the Raman analysis can differentiate COD from COM and PCHT from MAPH.

Engineered Carbon-Nanomaterial-Based Electrochemical Sensors for Biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.

Dual energy can accurately differentiate uric acid-containing urinary calculi from calcium stones

PURPOSE

To retrospectively evaluate the accuracy of dual-energy CT (DECT) in the detection of the chemical composition of urinary calculi in correlation with infrared spectroscopic stone analysis.

METHODS

We reviewed the CT scans of 255 patients who underwent DECT due to a clinical suspicion of urolithiasis. Out of this group, we included 64 patients with clinically symptomatic urolithiasis requiring stone removal. After surgical removal of the stone by ureterorenoscopy, chemical composition was analyzed with infrared spectroscopy. We correlated DECT stone characterization results with chemical stone composition based on dual-energy indices (DEI). A total of 213 renal and ureteral stones could be removed and chemically analyzed.

RESULTS

A total of 213 calculi were evaluated. Thirty eight out of sixty four (59 %) patients had >1 stone. DECT was used to differentiate stones by using DEI. Stones harboring calcium (CA) were color-coded in blue, while stones containing uric acid (UA) were colored red. Median DEI in UA-containing stones were 0.001. Non-UA-containing stones had a DEI between 0.073 for pure CA stones and 0.077 containing CA and other substances (p = 0.001; p = 0.03, respectively). Sensitivity of DECT was 98.4 % for differentiation of UA from non-UA-containing calculi. Specificity was 98.1 %. Mean effective radiation dose of DECT was 4.18 mSv (0.44-14.27 mSv), thus comparable to conventional CT scans of the abdomen. Conventional measurement of Hounsfield units did not correlate with stone composition.

CONCLUSION

DECT with image post-processing reliably discriminates UA-containing calculi from all other stones, but the study offered limitations. Discrimination within the non-UA stones cannot be reliably achieved but is clinically insignificant.

Efficacy and Biocompatibility of Neutral Icodextrin Peritoneal Dialysis Fluid

Neutral icodextrin peritoneal dialysis (PD) fluid (n-ICO) has become available for use in Japan. However, removal of water and solutes remains to be elucidated in detail. The present study was designed to determine removal of water, electrolytes, and small, middle, and large molecules in a period of 16 hours. In addition, biocompatibility with respect to peritoneal mesothelial cells was determined.Three stable patients undergoing PD at Tohoku University Hospital were administered n-ICO. Water removal was monitored every 2 hours. Sodium, urea nitrogen [molecular weight (MW): 28 Da], uric acid (MW: 168 Da), β₂-microglobulin [β2M (MW: 11,800 Da)], α₁-microglobulin [α1M (MW: 33,000 Da)], albumin (MW: 66,000 Da), and immunoglobulin G (MW: 160,000 Da) were measured in plasma and dialysate.Primary human peritoneal mesothelial cells were collected from 6 patients. Equal numbers of cells were seeded into 96-well culture plates and cultured for 12 hours. Culture medium was then replaced with dialysate, and 24-hour cell proliferation was determined by WST-1 assay.Water removal was sustained for 16 hours with n-ICO. The Na concentration in effluent did not change over that time. Small molecules such as urea nitrogen and uric acid were rapidly removed. Thus, their dialysate-to-plasma concentration ratio (D/P) approached 1.0 (equilibrium) in 2 - 4 hours. The D/P values for the larger molecules β2M and α1M were 0.4 and less than 0.1 respectively at 16 hours. However, larger molecules were removed in a time-dependent manner.Cell proliferation with n-ICO PD fluid was not different from that with lactate-buffered glucose PD fluid, but was increased from that with acidic icodextrin PD fluid (a-ICO).Water and solute removal with the new n-ICO is not much different from that with a-ICO. However, biocompatibility as reflected by cell proliferation was superior under n-ICO than under a-ICO and equal to proliferation under glucose PD fluid.

Wearable salivary uric acid mouthguard biosensor with integrated wireless electronics

This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications.

Carbon nanospikes grown on metal wires as microelectrode sensors for dopamine

Carbon nanomaterials are advantageous as electrodes for neurotransmitter detection, but the difficulty of nanomaterials deposition on electrode substrates limits the reproducibility and future applications. In this study, we used plasma enhanced chemical vapor deposition (PECVD) to directly grow a thin layer of carbon nanospikes (CNS) on cylindrical metal substrates. No catalyst is required and the CNS surface coverage is uniform over the cylindrical metal substrate. The CNS growth was characterized on several metallic substrates including tantalum, niobium, palladium, and nickel wires. Using fast-scan cyclic voltammetry (FSCV), bare metal wires could not detect 1 μM dopamine while carbon nanospike coated wires could. The highest sensitivity and optimized S/N ratio was recorded from carbon nanospike-tantalum (CNS-Ta) microwires grown for 7.5 minutes, which had a LOD of 8 ± 2 nM for dopamine with FSCV. CNS-Ta microelectrodes were more reversible and had a smaller ΔE(p) for dopamine than carbon-fiber microelectrodes, suggesting faster electron transfer kinetics. The kinetics of dopamine redox were adsorption controlled at CNS-Ta microelectrodes and repeated electrochemical measurements displayed stability for up to ten hours in vitro and over a ten day period as well. The oxidation potential was significantly different for ascorbic acid and uric acid compared to dopamine. Growing carbon nanospikes on metal wires is a promising method to produce uniformly-coated, carbon nanostructured cylindrical microelectrodes for sensitive dopamine detection.

2015 Gout Classification Criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative

OBJECTIVE

Existing criteria for the classification of gout have suboptimal sensitivity and/or specificity, and were developed at a time when advanced imaging was not available. The current effort was undertaken to develop new classification criteria for gout.

METHODS

An international group of investigators, supported by the American College of Rheumatology and the European League Against Rheumatism, conducted a systematic review of the literature on advanced imaging of gout, a diagnostic study in which the presence of monosodium urate monohydrate (MSU) crystals in synovial fluid or tophus was the gold standard, a ranking exercise of paper patient cases, and a multicriterion decision analysis exercise. These data formed the basis for developing the classification criteria, which were tested in an independent data set.

RESULTS

The entry criterion for the new classification criteria requires the occurrence of at least 1 episode of peripheral joint or bursal swelling, pain, or tenderness. The presence of MSU crystals in a symptomatic joint/bursa (i.e., synovial fluid) or in a tophus is a sufficient criterion for classification of the subject as having gout, and does not require further scoring. The domains of the new classification criteria include clinical (pattern of joint/bursa involvement, characteristics and time course of symptomatic episodes), laboratory (serum urate, MSU-negative synovial fluid aspirate), and imaging (double-contour sign on ultrasound or urate on dual-energy computed tomography, radiographic gout-related erosion). The sensitivity and specificity of the criteria are high (92% and 89%, respectively).

CONCLUSION

The new classification criteria, developed using a data-driven and decision analytic approach, have excellent performance characteristics and incorporate current state-of-the-art evidence regarding gout.