Rapid Determination of Creatinine in Human Urine by Microchip Electrophoresis with LED Induced Fluorescence Detection

Recent advances in microchip electrophoresis for analysis of pathogenic bacteria and viruses

Life-threatening diseases, such as hepatitis B, pneumonia, tuberculosis, and COVID-19, are widespread due to pathogenic bacteria and viruses. Therefore, the development of highly sensitive, rapid, portable, cost-effective, and selective methods for the analysis of such microorganisms is a great challenge. Microchip electrophoresis (ME) has been widely used in recent years for the analysis of bacterial and viral pathogens in biological and environmental samples owing to its portability, simplicity, cost-effectiveness, and rapid analysis. However, microbial enrichment and purification are critical steps for accurate and sensitive analysis of pathogenic bacteria and viruses in complex matrices. Therefore, we first discussed the advances in the sample preparation technologies associated with the accurate analysis of such microorganisms, especially the on-chip microfluidic-based sample preparations such as dielectrophoresis and microfluidic membrane filtration. Thereafter, we focused on the recent advances in the lab-on-a-chip electrophoretic analysis of pathogenic bacteria and viruses in different complex matrices. As the microbial analysis is mainly based on the analysis of nucleic acid of the microorganism, the integration of nucleic acid-based amplification techniques such as polymerase chain reaction (PCR), quantitative PCR, and multiplex PCR with ME will result in an accurate and sensitive analysis of microbial pathogens. Such analyses are very important for the point-of-care diagnosis of various infectious diseases.

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.

A highly selective colorimetric assay for the determination of creatinine in biological samples using gluconic acid capped silver nanoparticles after ionic liquid based dispersive liquid phase microextraction

A dispersive liquid-phase microextraction method combined with UV–vis spectrophotometry was utilized to highly selective determination of creatinine in human serum and urine samples. To overcome the interferences in complex matrices, creatinine reacted with 1,4-naphthoquinone-2- potassium sulfonate reagent to produce a red coloured product that could be extracted into a small volume of 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF6) ionic liquid solvent. To increase the sensitivity of the assay, gluconic acid capped silver nanoparticles (Ag NPs) were used. On addition of Ag NPs to the red coloured extracted product, the solution turned to blue accompanied with a red shift in wavelength around 620 nm that could be detected by the naked eye. The effective variables on the determination of creatinine such as concentration of the reagent, amount of formic and hydrochloric acids, type and volume of the extractant, and concentration of Ag NPs were investigated. Under the optimal conditions, the calibration plot was bimodal with linear ranges from 0.1 to 1.5 µg mL−1 and 1.5 to 105 µg mL−1 creatinine with a limit of detection 0.1 µg mL−1. The relative standard deviation for five measurements at 35 µg mL−1 concentration level was 3.8%. The newly developed assay was used for the determination of creatinine in human serum and urine specimens with satisfactory results.

Optical model of light propagation in total internal reflection fluorescence sensors

We report the development of a three-dimensional optical model to predict the propagation of light through multilayer optical fluorescence sensors employing total internal reflection. The ray-tracing-based model visualizes the propagation of light from a light source through the optical sensor allowing optimization of the optical path, optical properties of the materials, and the coupling strategy. The model demonstrates how light can be guided through different layers of the sensor structure by controlling the incident angle of light and the relationship between the incident angle and the relative sensitivity. Simulation results are compared against experimental data to validate the model in a fluorescence-based dissolved oxygen sensor. Customization of the light source parameters, coupling optics, sensor optical properties, and sensor dimensions could allow developers to refine and optimize sensor prototypes before conducting bench testing.

Microchip electrophoresis based multiplexed assay for silver and mercury ions simultaneous detection in complex samples using a stirring bar modified with encoded hairpin probes for specific extraction

It is crucially important to rapidly, simultaneously, and sensitively determine trace amounts of heavy metal ions in complex samples. Herein, a stirring bar modified with two kinds of encoded hairpin DNA probes (H₀ and H₀') was used in a multiplexed strategy allowing for specific extraction of Hg²⁺ and Ag⁺ coupled to microchip electrophoresis (MCE) separation and LED induced fluorescence (LIF) detection. The extraction step utilizes stir bars, which are functionalized with designed hairpin DNA probes (H₀ with TT and H₀' with CC mismatches in stems). This allows the specific capture of Hg²⁺ and Ag⁺ through CAg⁺C and THg²⁺T interactions. These complexes are then enzymatically degraded by the action of exonuclease III (Exo III). The ions released during this enzymatic reaction can initiate a new cycle of interactions with hairpin structures and enzymatic reactions and so on. This cyclic step is specific to the presence of Hg²⁺ and Ag⁺ and represents the first round of amplification of the presence of the selected ions. The resulting single strand DNAs on the stirring bars after enzymatic degradation were used in the second step as primers to trigger the catalytic hairpin assembly (CHA) in the presence of a couple of hairpin structures in solution. Such a reaction allows producing duplexes that can be monitored by MCE-LIF. The fluorescence intensity of CHA products (I_P) increased and that of hairpin DNAs (I_R) decreased with the increase of target concentrations. The signal ratios (I_P/I_R and I_P'/I_R') consisted of targets. The assay was employed for Hg²⁺ and Ag⁺ detection in several mediums including water, milk, and fish samples with complex matrices. The results showed that the assay could avoid matrix interference to increase the sensitivity. Therefore, the multiplexed assay was ideal to simultaneously and quickly detect metal ions in complex samples.

A decade of microchip electrophoresis for clinical diagnostics - A review of 2008-2017

A core element in clinical diagnostics is the data interpretation obtained through the analysis of patient samples. To obtain relevant and reliable information, a methodological approach of sample preparation, separation, and detection is required. Traditionally, these steps are performed independently and stepwise. Microchip capillary electrophoresis (MCE) can provide rapid and high-resolution separation with the capability to integrate a streamlined and complete diagnostic workflow suitable for the point-of-care setting. Whilst standard clinical diagnostics methods normally require hours to days to retrieve specific patient data, MCE can reduce the time to minutes, hastening the delivery of treatment options for the patients. This review covers the advances in MCE for disease detection from 2008 to 2017. Miniaturised diagnostic approaches that required an electrophoretic separation step prior to the detection of the biological samples are reviewed. In the two main sections, the discussion is focused on the technical set-up used to suit MCE for disease detection and on the strategies that have been applied to study various diseases. Throughout these discussions MCE is compared to other techniques to create context of the potential and challenges of MCE. A comprehensive table categorised based on the studied disease using MCE is provided. We also comment on future challenges that remain to be addressed.

Microfluidic chip-capillary electrophoresis device for the determination of urinary metabolites and proteins

Microfluidic chip-CE (MC-CE) devices have caught recent attention for diagnostic applications in urine. This is due to the successes reported in handling real urine samples by integrating microfluidic chips (MC) with analyte enrichment and sample cleanup to CE with high separation efficiency and sensitive analyte detection. Here, we review the determination of urinary metabolites and proteins by MC-CE devices within the past 7 years. The application scope for MC-CE integrated devices was found to exceed the use of either technique alone, showing comparable performance to laser-induced fluorescence detection using less sensitive UV detectors, offering the flexibility to handle difficult urine samples with on-chip dilution and online standard addition and delivering enhanced performance as compared with commercial microfluidic chip electrophoresis chips.

Picric acid capped silver nanoparticles as a probe for colorimetric sensing of creatinine in human blood and cerebrospinal fluid samples

A new approach has been proposed for the traditional Jaffe's reaction by coating Ag NPs with picric acid to form an assembly that can selectively detect creatinine. This sensor proficiently and selectively recognizes creatinine due to the ability of picric acid to bind with it and form a complex.

Two low-cost digital camera-based platforms for quantitative creatinine analysis in urine

In clinical analysis creatinine is a routine biomarker for the assessment of renal and muscular dysfunctions. Although several techniques have been proposed for a fast and accurate quantification of creatinine in human serum or urine, most of them require expensive or complex apparatus, advanced sample preparation or skilled operators. To circumvent these issues, we propose two home-made platforms based on a CD Spectroscope (CDS) and Computer Screen Photo-assisted Technique (CSPT) for the rapid assessment of creatinine level in human urine. Both systems display a linear range (r(2) = 0.9967 and 0.9972, respectively) from 160 μmol L(-1) to 1.6 mmol L(-1) for standard creatinine solutions (n = 15) with respective detection limits of 89 μmol L(-1) and 111 μmol L(-1). Good repeatability was observed for intra-day (1.7-2.9%) and inter-day (3.6-6.5%) measurements evaluated on three consecutive days. The performance of CDS and CSPT was also validated in real human urine samples (n = 26) using capillary electrophoresis data as reference. Corresponding Partial Least-Squares (PLS) regression models provided for mean relative errors below 10% in creatinine quantification.

Present state of microchip electrophoresis: state of the art and routine applications

Microchip electrophoresis (MCE) was one of the earliest applications of the micro-total analysis system (μ-TAS) concept, whose aim is to reduce analysis time and reagent and sample consumption while increasing throughput and portability by miniaturizing analytical laboratory procedures onto a microfluidic chip. More than two decades on, electrophoresis remains the most common separation technique used in microfluidic applications. MCE-based instruments have had some commercial success and have found application in many disciplines. This review will consider the present state of MCE including recent advances in technology and both novel and routine applications in the laboratory. We will also attempt to assess the impact of MCE in the scientific community and its prospects for the future.

Analytical devices based on light-emitting diodes--a review of the state-of-the-art

A general overview of the development of the uses of light-emitting diodes in analytical instrumentation is given. Fundamental aspects of light-emitting diodes, as far as relevant for this usage, are covered in the first part. The measurement of light intensity is also discussed, as this is an essential part of any device based on light-emitting diodes as well. In the second part, applications are discussed, which cover liquid and gas-phase absorbance measurements, flow-through detectors for chromatography and capillary electrophoresis, sensors, as well as some less often reported methods such as photoacoustic spectroscopy.

Light-emitting diodes for analytical chemistry

Light-emitting diodes (LEDs) are playing increasingly important roles in analytical chemistry, from the final analysis stage to photoreactors for analyte conversion to actual fabrication of and incorporation in microdevices for analytical use. The extremely fast turn-on/off rates of LEDs have made possible simple approaches to fluorescence lifetime measurement. Although they are increasingly being used as detectors, their wavelength selectivity as detectors has rarely been exploited. From their first proposed use for absorbance measurement in 1970, LEDs have been used in analytical chemistry in too many ways to make a comprehensive review possible. Hence, we critically review here the more recent literature on their use in optical detection and measurement systems. Cloudy as our crystal ball may be, we express our views on the future applications of LEDs in analytical chemistry: The horizon will certainly become wider as LEDs in the deep UV with sufficient intensity become available.

Point of care creatinine measurement for diagnosis of renal disease using a disposable microchip

A point-of-care device for the determination of elevated creatinine levels in blood is reported. This device potentially offers a new and simple clinical regime for the determination of creatinine that will give huge time savings and removal of several steps of determination. The test employs a disposable prefilled microchip and the handheld Medimate Multireader®. By optimizing the analytical conditions it was found that the LOD of the proposed method was 87 μM creatinine, close to the normal human serum levels that are in the range of 60 to 100 μM. A statistical analysis of the residual shows a normal distribution, indicating the absence of systematic errors in the proposed method. The test can be used to distinguish patients with renal insufficiency (creatinine levels >100 μM) from healthy persons. Long-term monitoring could furthermore distinguish between acute renal failure and chronic kidney disease by the rate of creatinine concentration rise.