Electrochemical Creatinine (Bio)Sensors for Point-of-Care Diagnosis of Renal Malfunction and Chronic Kidney Disorders

In the post-pandemic era, point-of-care (POC) diagnosis of diseases is an important research frontier. Modern portable electrochemical (bio)sensors enable the design of POC diagnostics for the identification of diseases and regular healthcare monitoring. Herein, we present a critical review of the electrochemical creatinine (bio)sensors. These sensors either make use of biological receptors such as enzymes or employ synthetic responsive materials, which provide a sensitive interface for creatinine-specific interactions. The characteristics of different receptors and electrochemical devices are discussed, along with their limitations. The major challenges in the development of affordable and deliverable creatinine diagnostics and the drawbacks of enzymatic and enzymeless electrochemical biosensors are elaborated, especially considering their analytical performance parameters. These revolutionary devices have potential biomedical applications ranging from early POC diagnosis of chronic kidney disease (CKD) and other kidney-related illnesses to routine monitoring of creatinine in elderly and at-risk humans.

Portable smartphone integrated 3D-Printed electrochemical sensor for nonenzymatic determination of creatinine in human urine

3D printing technologies are an attractive for fabricating electrochemical sensors due to their ease of operation, freedom of design, fast prototyping, low waste, and low cost. We report the fabrication of a simple 3D-printed electrochemical sensing device for non-enzymatic detection of creatinine, an important indicator of renal function. To create the 3D-printed electrodes (3DE), carbon black/polylactic acid (CB/PLA) composite filament was used. The 3DE was activated using 0.5 M NaOH via amperometry prior to use to improve electrochemical performance. To give selectivity for creatinine, the activated 3DE was modified with a copper oxide nanoparticle-ionic liquid/reduced graphene oxide (CuO-IL/rGO) composite. The modified 3DE was characterized using microscopy and electrochemistry. Cyclic voltammetry and amperometry were used to evaluate sensor performance. The modified 3DE provided electrocatalytic activity towards creatinine without enzymes. Under optimal conditions, the modified 3DE directly coupled with a portable smartphone potentiostat exhibited the linear detection range of 0.5-35.0 mM, and the limit of detection was 37.3 μM, which is sufficient for detecting creatinine in human urine samples. Furthermore, the other physiological compounds present in human urine were not detected on the modified 3DE. Therefore, the modified 3DE could be a tool for effective creatinine screening in the urine.

Anodic SnO2 Nanoporous Structure Decorated with Cu2O Nanoparticles for Sensitive Detection of Creatinine: Experimental and DFT Study

Advanced anodic SnO₂ nanoporous structures decorated with Cu₂O nanoparticles (NPs) were employed for creatinine detection. Anodization of electropolished Sn sheets in 0.3 M aqueous oxalic acid electrolyte under continuous stirring produced complete open top, crack-free, and smooth SnO₂ nanoporous structures. Structural analyses confirm the high purity of rutile SnO₂ with successful functionalization of Cu₂O NPs. Morphological studies revealed the formation of self-organized and highly-ordered SnO₂ nanopores, homogeneously decorated with Cu₂O NPs. The average diameter of nanopores is ∼35 nm, while the average Cu₂O particle size is ∼23 nm. Density functional theory results showed that SnO₂@Cu₂O hybrid nanostructures are energetically favorable for creatinine detection. The hybrid nanostructure electrode exhibited an ultra-high sensitivity of around 24343 μA mM^-1 cm^-2 with an extremely lower detection limit of ∼0.0023 μM, a fast response time (less than 2 s), and wide linear detection ranges of 2.5-45 μM and 100 μM to 15 mM toward creatinine. This is ascribed to the creation of highly active surface sites as a result of Cu₂O NP functionalization, SnO₂ band gap diminution, and the formation of heterojunction and Cu(1)/Cu(ll)-creatinine complexes through secondary amines which occur in the creatinine structure. The real-time analysis of creatinine in blood serum by the fabricated electrode evinces the practicability and accuracy of the biosensor with reference to the commercially existing creatinine sensor. The proposed biosensor demonstrated excellent stability, reproducibility, and selectivity, which reflects that the SnO₂@Cu₂O nanostructure is a promising candidate for the non-enzymatic detection of creatinine.

Electrochemical creatinine detection for advanced point-of-care sensing devices: a review

Creatinine is an amino acid derived from creatine catabolism at different steps of the body's organs, and its detection is significant because levels out of normal values are linked to some diseases like kidney failure. Normal concentration levels of creatinine in blood are from 45 to 110 μM, while in urine, typical concentrations range between 3.3 to 27 mM, and in saliva from 8.8 and 26.5 μM. Nowadays, the creatinine detection is carried through different spectroscopic-colorimetric methods; however, the resulting values present errors due to high interferences, delayed analysis, and poor stability. Electrochemical sensors have been an alternative to creatinine detection, and the electrochemical methods have been adapted to detect in enzymatic and non-enzymatic sensors, the latter being more relevant in recent years. Nanomaterials have made creatinine sensors more stable, sensitive, and selective. This review presents recent advances in creatinine electrochemical sensors for advances in point-of-care (POC) sensing devices, comprising both a materials point of view and prototypes for advanced sensing. The effect of the metal, particle size, shape and other morphological and electronic characteristics of nanomaterials are discussed in terms of their impact on the effective detection of creatinine. In addition, the application of nanomaterials in POC devices is revised pointing to practical applications and looking for more straightforward and less expensive devices to manufacture.

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.

Facile Detection of Blood Creatinine Using Binary Copper-Iron Oxide and rGO-Based Nanocomposite on 3D Printed Ag-Electrode under POC Settings

Metal nanoparticles have been helpful in creatinine sensing technology under point-of-care (POC) settings because of their excellent electrocatalyst properties. However, the behavior of monometallic nanoparticles as electrochemical creatinine sensors showed limitations concerning the current density in the mA/cm² range and wide detection window, which are essential parameters for the development of a sensor for POC applications. Herein, we report a new sensor, a reduced graphene oxide stabilized binary copper-iron oxide-based nanocomposite on a 3D printed Ag-electrode (Fe-Cu-rGO@Ag) for detecting a wide range of blood creatinine (0.01 to 1000 μM; detection limit 10 nM) in an electrochemical chip with a current density ranging between 0.185 and 1.371 mA/cm² and sensitivity limit of 1.1 μA μM^-1 cm^-2 at physiological pH. Interference studies confirmed that the sensor exhibited no interference from analytes like uric acid, urea, dopamine, and glutathione. The sensor response was also evaluated to detect creatinine in human blood samples with high accuracy in less than a minute. The sensing mechanism suggested that the synergistic effects of Cu and iron oxide nanoparticles played an essential role in the efficient sensing where Fe atoms act as active sites for creatinine oxidation through the secondary amine nitrogen, and Cu nanoparticles acted as an excellent electron-transfer mediator through rGO. The rapid sensor fabrication procedure, mA/cm² peak current density, a wide range of detection limits, low contact resistance including high selectivity, excellent linear response (R² = 0.991), and reusability ensured the application of advanced electrochemical sensor toward the POC creatinine detection.

Serum Creatinine Electrochemical Biosensor on Printed Electrodes Using Monoenzymatic Pathway to 1-Methylhydantoin Detection

The rising prevalence of Chronic Kidney Disease (CKD) has necessitated efforts towards the development of cost-effective and accurate biosensors for serum creatinine, which is a potent biomarker reflecting kidney function. This work presents a novel and cost-effective technique to estimate serum creatinine without any sample preprocessing. The technique involves the conversion of creatinine by a monoenzymatic pathway to 1-methylhydantoin. The concentration of 1-methylhydantoin is then quantified by utilizing its innate ability to form a complex with transition metals such as cobalt. The complex formation has been validated using optical spectroscopy and the transmittance at 290 nm wavelength is used to identify the optimum concentration of cobalt chloride in sensing chemistry. This chemical assay is shown to be robust against interference from serum albumin, the abundant plasma protein that can potentially influence the sensor response. The electrochemical biosensor developed using screen-printed electrodes thus provides highly selective creatinine estimation over the range of 0.2-4 mg/dL in a sample volume of 300 μL with no preprocessing and hence can be easily translated into a viable point-of-care (POC) device.

Recent Trends in Electrochemical Sensors for Vital Biomedical Markers Using Hybrid Nanostructured Materials

This work provides a succinct insight into the recent developments in electrochemical quantification of vital biomedical markers using hybrid metallic composite nanostructures. After a brief introduction to the biomarkers, five types of crucial biomarkers, which require timely and periodical monitoring, are shortlisted, namely, cancer, cardiac, inflammatory, diabetic and renal biomarkers. This review emphasizes the usage and advantages of hybrid nanostructured materials as the recognition matrices toward the detection of vital biomarkers. Different transduction methods (fluorescence, electrophoresis, chemiluminescence, electrochemiluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy) reported for the biomarkers are discussed comprehensively to present an overview of the current research works. Recent advancements in the electrochemical (amperometric, voltammetric, and impedimetric) sensor systems constructed with metal nanoparticle-derived hybrid composite nanostructures toward the selective detection of chosen vital biomarkers are specifically analyzed. It describes the challenges involved and the strategies reported for the development of selective, sensitive, and disposable electrochemical biosensors with the details of fabrication, functionalization, and applications of hybrid metallic composite nanostructures.