Development of Ratiometric Fluorescent Biosensors for the Determination of Creatine and Creatinine in Urine

Al3+-Responsive Ratiometric Fluorescent Sensor for Creatinine Detection: Thioflavin-T and Sulfated-β-Cyclodextrin Synergy

Kidney disorders are a rising global health issue, necessitating early diagnosis for effective treatment. Creatinine, a metabolic waste product from muscles, serves as an ideal biomarker for kidney damage. The existing optical methods for creatinine detection often involve labor-intensive synthesis processes and present challenges with the aqueous solubility and sensitivity to experimental variations. In this study, we introduce a straightforward fluorescence "turn-on" ratiometric sensor system for creatinine detection in aqueous media with a limit of detection of 0.5 μM. The sensor is based on sulfated-β-cyclodextrin (SCD)-templated H-aggregate of a commercially available, ultrafast rotor dye thioflavin-T (ThT). The Al3+ ion-induced dissociation of ThT-SCD aggregates, followed by reassociation upon creatinine addition, generates a detectable signal. The modulation of monomer/aggregate equilibrium due to the disassembly/reassembly of the ThT-SCD system under Al3+/creatinine influence serves as the optimal strategy for ratiometric creatinine detection in aqueous media. Our sensor framework offers several advantages: utilization of the readily available dye ThT, which eliminates the need for a laborious synthesis of custom fluorescent probes; ratiometric sensing, which improves quantitative analysis accuracy; and compatibility with complex aqueous media. The sensor's practical utility has been successfully demonstrated in artificial urine samples. In summary, our sensor system represents a significant advancement in the rapid, selective, and sensitive detection of the clinically crucial bioanalyte creatinine, offering potential benefits for the early diagnosis and management of kidney disorders.

Insight into mechanisms of creatinine optical sensing using fluorescein-gold complex

Creatinine level in biological fluids is a clinically relevant parameter to monitor vital functions and it is well assessed that measuring creatinine levels in the human body can be of great utility to evaluate renal, muscular, or thyroid dysfunctions. The accurate detection of creatinine levels may have a critical role in providing information on health status and represents a tool for the early diagnosis of severe pathologies. Among different methods for creatinine detection that have been introduced and that are evolving with increasing speed, fluorescence-based and colorimetric sensors represent one of the best alternatives, thanks to their affordability, sensitivity and easy readability. In this work, we demonstrate that the fluorescein-Au3+ complex provides a rapid, selective, and sensitive tool for the quantification of creatinine concentrations in ranges typical of sweat and urine. UV-visible absorption, diffuse reflectance spectroscopy, steady state and time resolved fluorescence spectroscopy were used to shed light on the molecular mechanisms involved in the changes of optical properties, which underlie the multiplexed sensor analytical reply. Interestingly, sensing can be performed in solution or on solid nylon support accessing different physiological concentrations from micromolar to millimolar range. As a proof-of-concept, the nylon-based platform was used to demonstrate its effectiveness in creatinine detection on a solid and flexible substrate, showing its analytical colorimetric properties as an easy and disposable creatinine point-of-care test.

Trend in creatinine determining methods: Conventional methods to molecular‐based methods

Renal failure (RF) disease is ranked as one of the most prevalent diseases with severe morbidity and mortality. Early diagnosis of RF leads to subsequent control of disease to reduce the poor prognosis. The level of sera creatinine is considered as a significant biomarker for kidney biofunction, which is routinely detected by the Jaffe reaction. The normal range for creatinine in the blood may be 0.84‐1.21 mg/dL. Low accuracy, insufficient sensitivity, explosive and toxicity of picric acid, and pseudo‐interaction with nonspecific elements such as ammonium ions in the Jaffe method lead to the development of various techniques for precise detection of creatinine such as spectroscopic, electrochemical, and chromatography approaches and sensors based on enzymes, molecular imprinted polymer and nanoparticles, etc. Based on previously established results, they are trying to construct sensors with high accuracy, optimum sensitivity, acceptable linear/calibration range, and limit of detection, which are small in size and applicable by the patient him/herself (point‐of‐care testing). By comparing the results of research, a molecularly imprinted electrochemiluminescence‐based sensor with linear/calibration range of 5‐1 mMconcentration of creatinine and the detection limit of 0.5 nM has the best detectable resolution with 2 million measurable points. In this paper, we will review the recently developed methods for measuring creatinine concentration and renal biofunction.

Fabrication of an improved amperometric creatinine biosensor based on enzymes nanoparticles bound to Au electrode

An improved amperometric creatinine biosensor was fabricated that dependent on covalent immobilisation of nanoparticles of creatininase (CANPs), creatinase (CINPs) and sarcosine oxidase (SOxNPs) onto gold electrode (AuE). The CANPs/CINPs/SOxNPs/AuE was characterised by scanning electron microscopy and cyclic voltammetry at various stages. The working electrode exhibited optimal response within 2 s at a potential of 0.6 V, against Ag/AgCl, pH 6.5 and 30 °C. A linear relationship was observed between creatinine concentration range, 0.1-200μM and biosensor response i.e. current in mA, under optimum conditions. Biosensor offered a low detection limit of 0.1 μM with long storage stability. Analytical recoveries of added creatinine in blood sera at 0.5 mM and at 1.0 mM concentrations, were 92.0% and 79.20% respectively. The precision i.e. within and between-batch coefficients of variation were 2.04% and 3.06% respectively. There was a good correlation (R² = 0.99) between level of creatinine in sera, as calculated by the colorimetric method and present electrode. The CANPs/CINPs/SOxNPs/Au electrode was reused 200 times during the period of 180 days, with just 10% loss in its initial activity, while being stored at 4 °C, when not in use.HighlightsPrepared and characterised creatininase (CA), creatinase (CI) sarcosine oxidase (SOx) nanoparticles and immobilised them onto gold electrode (AuE) for fabrication of an improved amperometric creatinine biosensor.The biosensor displayed a limit of detection (LOD) of 0.1 μM with a linear working range of 0.1 μM-200 μM.The biosensor was evaluated and applied to measure elevated creatinine levels in sera from whom suffering from kidney and muscular disorders.The working electrode retained 90% of its initial activity, while being stored dry at 4 ˚C for 180 days.