Determination of serum creatinine by reaction with methyl-3,5-dinitrobenzoate in Methyl Sulfoxide

A review of recent advances in non-enzymatic electrochemical creatinine biosensing

Creatinine biosensing is a rapidly developing field owing to the clinical relevance of creatinine as a vital biomarker for several diseases associated with renal, thyroidal, and muscular dysfunctions. Over the years, we have observed numerous creatinine biosensing strategies, including the most widely studied enzymatic creatinine biosensors. Though the enzymatic approach provides excellent selectivity and reliability, it has certain drawbacks, which include high fabrication cost and poor storage stability (that is inherent to every enzyme-based biosensors). This has led to the development of non-enzymatic creatinine biosensors, of which electrochemical sensors are the most promising for point-of-care applications. However, only a limited number of studies have been conducted and there is a lack of reviews addressing the recent advances in this research area. Herein, we present for the first time, a review with a prime focus on the various strategies implemented in non-enzymatic electrochemical creatinine biosensing. We aim to offer a comprehensive context on the achievements and limitations of currently available non-enzymatic electrochemical creatinine biosensors and address the underlying factors pertaining to the interplay of modification/fabrication techniques with the sensitivity, selectivity, interferences, and long-term storage stability of the biosensor. We hope that this work shall prove to be seminal in the conception and advancement of future non-enzymatic electrochemical creatinine biosensors.

Quantification of creatinine in biological samples based on the pseudoenzyme activity of copper-creatinine complex

Glomerular filtration rate (GFR), the marker of chronic kidney disease can be analyzed by the concentration of cystatin C or creatinine and its clearance in human urine and serum samples. The determination of cystatin C alone as an indicator of GFR does not provide high accuracy, and is more expensive, thus measurement of creatinine has an important role in estimating GFR. We have made an attempt to quantify creatinine based on its pseudoenzyme activity of creatinine in the presence of copper. Creatinine in the presence of copper oxidizes paraphenylenediamine dihydrochloride (PPDD) which couples with dimethylamino benzoicacid (DMAB) giving green colored chromogenic product with maximum absorbance at 710 nm. Kinetic parameters relating this reaction were evaluated. Analytical curves of creatinine by fixed time and rate methods were linear at 8.8-530 μmol L(-1) and 0.221-2.65 mmol L(-1), respectively. Recovery of creatinine varied from 97.8 to 107.8%. Limit of detection and limit of quantification were 2.55 and 8.52 μmol L(-1) respectively whereas Sandell's sensitivity and molar absorption coefficient values were 0.0407 μg cm(-2) and 0.1427×10(4) L mol(-1) cm(-1) respectively. Precision studies showed that within day imprecision was 0.745-1.26% and day-to-day imprecision was 1.55-3.65%. The proposed method was applied to human urine and serum samples and results were validated in accordance with modified Jaffe's procedure. Wide linearity ranges with good recovery, less tolerance from excipients and application of the method to serum and urine samples are the claims which ascertain much advantage to this method.

Reactivity of creatinine with alkaline 3,5-dinitrobenzoate: a new fluorescent kidney function test

OBJECTIVES

To develop a new quantitative fluorometric assay for creatinine with enhanced specificity and inherent fluorescence sensitivity.

DESIGN AND METHODS

Creatinine is reacted with 3,5-dinitrobenzoate under alkaline reaction conditions to produce a fluorophore. Alternatively, 3,5-dinitrobenzoyl chloride or methyl-3,5-dinitrobenzoate may be employed as reagents. Fluorophore development was evaluated for Group 1A bases under aqueous and mixed solvent conditions.

RESULTS

The chemical reaction between creatinine and 3,5-dinitrobenzoate performed under highly alkaline conditions produced a fluorescent product with excitation and emission maxima near 410 and 475 nm, respectively. The reaction proceeds rapidly in the presence of group IA bases under both aqueous and mixed solvent conditions, in particular with water/dimethylsulfoxide and water/1,4-butanediol solvent systems containing 1.0 M LiOH. A linear calibration curve was obtained when the fluorescence intensity measured in microamperes was plotted versus creatinine concentration in the range of 5-50 mumol/L. The detection limit for creatinine was well below 1 mumol/L.

CONCLUSIONS

A simple, sensitive and highly specific fluorometric method for the determination creatinine has been developed.

Specific method for serum creatinine determination based on ion exchange chromatography and an automated alkaline picrate reaction -- a proposed reference method

A proposed reference method for serum creatinine has been developed under the auspices of the Committee on Reference Methods and Reference Materials of the Canadian Society of Clinical Chemists. A serum ultrafiltrate at pH 2.0 is applied through a closed sample loop injection system to a short column containing cationic resin of high resolving power. Elution with sodium citrate buffer by means of minipump at constant rate passes the eluate into alkaline picrate reagents in a continuous flow system (Technicon AAIII pump, AAII colorimeter 50 mm x 1.5 mm flow cell, narrow band width filter). The colour reaction peak is monitored visually to verify specificity and the area is calculated electronically. Specificity has been demonstrated by use of Jaffé-reactive substances such as glucose, sodium acetoacetate, L-ascorbic acid, pyruvic acid, L-dopa and glycocyamidine and also by use of an alternate colour reaction, sodium 3,5-dinitrobenzoate in place of alkaline picrate in the analysis of serum pools. Routine methods in common use, i.e., manual and automated alkaline picrate procedures, demonstrated a statistically significant high bias in interlaboratory studies in which this procedure was used for reference.