Photochemical decoration of magnetic composites with silver nanostructures for determination of creatinine in urine by surface-enhanced Raman spectroscopy

Boric acid-functionalized silver nanoparticles as SERS substrate for sensitive and rapid detection of fructose in artificial urine

The accurate detection of fructose in human urine can help prevent and screen for diseases such as fructokinase deficiency and hereditary fructose intolerance. Surface-enhanced Raman spectroscopy (SERS) is an analytical technique with selectivity and high sensitivity, which has been widely applied to the detection of targets with complex backgrounds. In this work, 4-mercaptophenylboronic acid (4-MPBA) was modified on the surface of silver nanoparticles (AgNPs) under mild conditions to obtain a boronic acid-functionalized SERS substrate for the detection of fructose in artificial urine. The detection mechanism was based on the deboronization reaction of 4-MPBA on the surface of AgNPs, which was induced by fructose, and the Raman signal of the generated thiophenol (TP) molecules was significantly enhanced by the silver nanoparticles, with a linear increase in SERS peak intensity at 1570 cm^-1. We achieved the detection limits of 0.084 µmol/L in water and 0.535 µmol/L in urine by this method. The relative standard deviation (RSD) in the recovery experiments of urine ranged from 1.01 % to 2.22 %, and the whole detection time was less than 10 min, which indicated that this method is highly reliable for fructose detection and has a good prospect in bioassay and clinical medicine.

Tyndall-effect-based colorimetric assay with colloidal silver nanoparticles for quantitative point-of-care detection of creatinine using a laser pointer pen and a smartphone

Herein, this paper initially reports a new colorimetric Tyndall effect-inspired assay (TEA) for simple, low-cost, sensitive, specific, and point-of-care detection of creatinine (an important small biomolecule) by making use of silver nanoparticles (AgNPs) as model colloidal nanoprobes for visual light scattering signaling. The naked-eye TEA method adopts negatively-charged citrate-capped AgNPs (Cit-AgNPs) prepared by sodium citrate reduction. In the presence of alkaline conditions, the creatinine analyte can form carbanion/oxoanion amino tautomers which in turn crosslink with carboxylate groups on the Cit-AgNPs via a hydrogen bonding network to mediate the aggregation of such colloidal nanoprobes showing a significantly-enhanced TE signal that was created and quantified by a hand-held laser pointer pen and a smartphone, respectively. The results demonstrate that the resulting equipment-free method with the TE readout could enable the portable quantification of creatinine with a detection limit of ∼55 nM, which was ∼90–2334 times lower than that obtained from AgNP-based colorimetric approaches with the most common localized surface plasma resonance signaling. Moreover, it shows a larger analytical sensitivity up to ∼580.8227 signal per nM, offering ∼2.4–232-fold improvement in comparison with many of the recent instrumental creatinine nanosensors. The accuracy and practicality of the developed nanosensing system was additionally confirmed with satisfactory recovery results ranging from ca. 98.52 to 100.36% when analyzing a set of real complex human urine samples.

This work describes a new nanosensor for one-step ultrasensitive naked-eye detection of creatinine based on the target-triggered aggregation of silver nanoparticles showing dramatically enhanced Tyndall effect.

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.

Quantitative determination of creatinine from serum of prostate cancer patients by N-doped porous carbon antimony (Sb/NPC) nanoparticles

Creatinine is an indicator of hindrance in urination and renal insufficiency. Creatinine levels are the marker of the late stages of prostate cancer. Early and sensitive detection of creatinine can reduce deaths associated with prostate cancer. In this work, nitrogen-doped porous carbon antimony (Sb/NPC) nanoparticles are fabricated to be employed as a non-enzymatic biosensor. Sb/NPC has promising redox activity and is synthesized by a two-step reaction using low-cost precursors. Electrochemical sensing by Sb/NPC is conducted for standard creatinine solutions on a three-electrodes system. Cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy are used to sense creatinine. LOD and LOQ of the Sb/NPC modified electrode are 0.74 µM and 2.4 µM, respectively. This electrode system analyzes creatinine in the serum of prostate cancer patients who have elevated PSA levels. More than 90% creatinine is recovered from a spiked serum sample of a prostate cancer patient. A direct relation is observed between PSA levels and creatinine levels in prostate cancer. The developed cyclic voltammetric setup detects trace concentrations of creatinine in serum.

Development of a cysteine sensor based on the peroxidase-like activity of AgNPs@ Fe3O4 core-shell nanostructures

In this study, a facile one step solvo-thermal procedure has been employed in generating magnetite-silver core-shell nanocomposites (AgNPs@ Fe₃O₄) with superior peroxidase-like catalytic property than bare magnetic nanoparticles (Fe₃O₄). The composites were characterized using different techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and surface-enhanced infrared absorption spectroscopy (SEIRA). In the presence of hydrogen peroxide, the synthesized composites were able to oxidize the colorless o-phenylenediamine (OPD) to a yellow colour 2, 3-diaminophenazine (DAP) with a better peroxidase-like activity than Fe₃O₄ alone. The obtained K_m value of AgNPs@ Fe₃O₄ with H₂O₂ and OPD substrates are 28.0 mM and 2.91 mM respectively. These are substantially lower than previously reported values and indicate the strong binding affinity of the substrates towards AgNPs@ Fe₃O₄ nanocomposites. Based on the obstruction activity of cysteine on the peroxidase-like catalytic property of the nanocomposites, a sensor was developed for detection of cystein with a limit of detection as low as 87 nM and a wider range of linearity. The sensor also exhibited excellent selectivity against potentially interfering molecules.

Citrate-capped silver nanoparticles as a probe for sensitive and selective colorimetric and spectrophotometric sensing of creatinine in human urine

Urinary creatinine concentration is a critical physiological parameter that enables reliable assessment of patient renal function and diagnosis of a broad spectrum of diseases. In this study, a simple and inexpensive sensor comprising monodisperse, citrate-capped silver nanoparticles (cc-AgNPs) was developed, which enabled rapid, sensitive and selective quantitation of creatinine directly in unprocessed urine. The mechanism of this sensor entails the creatinine-mediated aggregation of the cc-AgNPs (within 1 min) under alkaline conditions (pH 12). This is attributed to the tautomerization of creatinine to its amino anionic species at alkaline pH, which cross-link the cc-AgNPs via hydrogen bond networks with the negatively charged citrate caps. Creatinine elicited visibly-discernable color changes of the cc-AgNPs colloids in a concentration-dependent manner up to 10 μM. UV-visible spectroscopic analyses of the cc-AgNPs revealed that creatinine elicited a concentration-dependent decrease in intensity of the localized surface plasmon resonance (LSPR) band centered around 403 nm, with a concomitant increase in intensity of the red-shifted LSPR band at 670 nm. This observation denotes a creatinine-mediated increase in cc-AgNP particle size via aggregation, as confirmed by transmission electron microscopy analysis. The cc-AgNP sensor exhibited a linear correlation between the A₆₇₀/A₄₀₃ extinction ratio and creatinine concentration range of 0-4.2 μM in aqueous solutions (R² = 0.996), and a low detection limit of 53.4 nM. Hence, the simplicity, short assay time, and high sensitivity and selectivity of our cc-AgNP sensor affirms its utility as a creatinine monitoring assay for low-resource, point-of-care settings.

A Boronate Affinity-Assisted SERS Tag Equipped with a Sandwich System for Detection of Glycated Hemoglobin in the Hemolysate of Human Erythrocytes

Phenylboronic acid-functionalized, Ag shell-coated, magnetic, monodisperse polymethacrylate microspheres equipped with a glycoprotein-sensitive sandwich system were proposed as a surface-enhanced Raman scattering (SERS) substrate for quantitative determination of glycated hemoglobin (HbA1c). The magnetization of the SERS tag and the formation of the Ag shell on the magnetic support were achieved using the bifunctional reactivity of newly synthesized polymethacrylate microspheres. The hemolysate of human red blood cells containing both HbA1c and nonglycated hemoglobin was used for determination of HbA1c. The working principle of the proposed SERS tag is based on the immobilization of HbA1c by cyclic boronate ester formation between glycosyl residues of HbA1c and boronic acid groups of magnetic polymethacrylate microspheres and the binding of p-aminothiophenol (PATP)-functionalized Ag nanoparticles (Ag NPs) carrying another boronic acid ligand via cyclic boronate ester formation via unused glycosyl groups of bound HbA1c. Then, in situ formation of a Raman reporter, 4,4'-dimercaptoazobenzene from PATP under 785 nm laser irradiation allowed for the quantification of HbA1c bound onto the magnetic SERS tag, which was proportional to the HbA1c concentration in the hemolysate of human erythrocytes. The sandwich system provided a significant enhancement in the SERS signal intensity due to the plasmon coupling between Ag NPs and Ag shell-coated magnetic microspheres, and low HbA1c concentrations down to 50 ng/mL could be detected. The calibration curve obtained with a high correlation coefficient between the SERS signal intensity and HbA1c level showed the usability of the SERS protocol for the determination of the HbA1c level in any person.

From near-infrared and Raman to surface-enhanced Raman spectroscopy: progress, limitations and perspectives in bioanalysis

Over recent decades, spreading environmental concern entailed the expansion of green chemistry analytical tools. Vibrational spectroscopy, belonging to this class of analytical tool, is particularly interesting taking into account its numerous advantages such as fast data acquisition and no sample preparation. In this context, near-infrared, Raman and mainly surface-enhanced Raman spectroscopy (SERS) have thus gained interest in many fields including bioanalysis. The two former techniques only ensure the analysis of concentrated compounds in simple matrices, whereas the emergence of SERS improved the performances of vibrational spectroscopy to very sensitive and selective analyses. Complex SERS substrates were also developed enabling biomarker measurements, paving the way for SERS immunoassays. Therefore, in this paper, the strengths and weaknesses of these techniques will be highlighted with a focus on recent progress.

Spectroscopic and structural study of the newly synthesized heteroligand complex of copper with creatinine and urea

Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concentrations have been analyzed and the complex is found to be rigid and stable in its monomeric form at very low concentrations.