A copper nanoclusters probe for dual detection of microalbumin and creatinine

Nitrogen doped carbon dots and gold nanoparticles mediated FRET for the detection of creatinine in human urine samples

Serum creatinine (CR) is regarded as one of the most sought out prognostic biomarkers in medical evaluation of chronic kidney disease (CKD). In light of the diagnostic significance of CR, the utility of a fluorescence biosensor for its detection in human urine specimens has been explored based on Förster resonance energy transfer (FRET) across nitrogen-doped carbon dots (N-CDs) and gold nanoparticles (GNPs). A straightforward microwave-assisted synthesis procedure has been adopted to prepare N-CDs (λexcitation = 400 nm, λemission = 540 ± 5 nm) with bright green emissions. On addition of pre-synthesized GNPs, the radiative emanation of the N-CDs is completely suppressed on account of FRET across the N-CDs and the GNPs. About 77 % of their fluorescence intensity is recovered after adding CR to GNPs@N-CDs nanocomposite. The limit of detection for CR sensing is estimated as 0.02 µg•mL-1. This biosensor is selective enough to recognize CR in the existence of potential interfering substances (e.g., ascorbic acid, glucose, glutathione, urea, and electrolytes). Its practical utility for CR detection has been validated further on the basis of satisfactory correlation with the benchmark Jaffe method, as observed in artificial/human urine specimens. Consequently, this manuscript marks a pioneering report on employing CDs and GNPs-based FRET for identifying CR in urine specimens of CKD patients.

Excreted albumin of diabetic microalbuminuria cases exhibits pseudo esterase activity: A new way to explore microalbuminuria, perhaps with more information

BACKGROUND

Microalbuminuria is associated with several clinical conditions of public health concern. Particularly in diabetic patients, there is routine microalbuminuria screening to understand whether the renal complication has progressed to the microalbuminuria stage or not. Therefore, microalbuminuria detection is a matter of considerable interest. For such detection, the clinical labs rely on immunochemical methods. Nevertheless, the immunochemical methods are believed to be less sensitive for the purpose. So, the need arises for continuous research in the field. We believe that pseudoesterase activity of the excreted albumin in microalbuminuria cases is a potential target. This aspect is investigated here and it is shown that the excreted albumin in diabetic microalbuminuria cases retains its pseudoesterase activity, unlike the overt albuminuria cases.

METHODS

The cases of diabetic nephropathy and healthy controls were included in the study. The patients were divided into diabetic controls microalbuminuria, and overt albuminuria group considering the albumin to creatinine ratio (ACR). The urinary proteins of the cases were isolated by centrifugation. The obtained protein pellet was then checked for pseudoesterase activity by electrophoretic and fluorescence-based methods. The CD spectroscopy and LC-MS study was carried out to show the suitability of the substrate for the detection of albumin pseudoesterase activity. To further, understand the structure-function relation, molecular docking studies were carried out.

RESULTS

From the CD and LC-MS study the suitability of the used substrate was confirmed. The electrophoretic and fluorescence study showed that the protein of the microalbuminuria group retained the pseudoesterase activity whereas the same is lost in the overt albuminuria group. The molecular docking studies indicated that a change in albumin structure may result in a change in its pseudoesterase activity.

CONCLUSION

The urinary protein of diabetic microalbuminuria cases exhibits pseudoesterase activity. It distinguishes the excreted protein in the diabetic albuminuria group and the overt albuminuria group. This is the first study that showed the retention of pseudoesterase property in excreted albumin. Further, in this study a simple test is developed that distinguishes the excreted albumin in the microalbuminuria group and overt albuminuria group.

Rapid chemical reduction synthesis of copper nanoclusters with blue fluorescence for highly sensitive detection of furazolidone

Tannic acid (TA), as a stabilizing agent, was successfully utilized to establish blue-emitting copper nanoclusters (TA-Cu NCs) on the basis of a facile chemical reduction preparation method. Characterization results proved successful synthesis of TA-Cu NCs with uniform size and excellent stability. TA-Cu NCs exhibited a blue emission wavelength at 431 nm when excited at 364 nm. Interestingly, the as-prepared TA-Cu NCs were selectively quenched by furazolidone based on static quenching. In addition, this analysis platform for furazolidone detection had an excellent linear range from 0.5 to 120 μM with a detection limit of 0.074 μM (S/N = 3). Furthermore, the accuracy of this sensing method was successfully confirmed by detecting furazolidone in bovine serum samples, indicating that TA-Cu NCs had bright application prospects.

Glutathione S-transferase templated copper nanoclusters as a fluorescent probe for turn-on sensing of chlorotetracycline

Hereby, facile-green copper nanoclusters templated by glutathione S-transferase (GST-CuNCs) have been innovatively synthesized via a simple one-pot stirring method at room temperature. The as-prepared nanoclusters exhibited uniform size with satisfactory fluorescence intensity, good stability and low cytotoxicity. Significantly, the fluorescence of the obtained GST-CuNCs could be considerably enhanced by the addition of chlorotetracycline (CTC) rather than other analogues of CTC, which was ascribed to the aggregation-induced enhancement caused by the interaction between CTC and GST. The enhanced fluorescence intensity demonstrated a good linear correlation with the CTC concentration in the range of 30-120 μM (R2 = 0.99517), and the low detection limit was 69.7 nM. Furthermore, the proposed approach showed favorable selectivity and anti-interference toward CTC among prevalent ions and amino acids. Additionally, this nanoprobe was also applied to the quantitative detection of CTC in serum samples with satisfactory outcomes, which demonstrated excellent prospects for practical applications.

Adjustable luminescence copper nanoclusters nanoswitch based on competitive coordination of samarium ions for cascade detection of adenosine triphosphate and acid phosphatase activity

Benefit from the strong coordination property, lanthanide metal ions have been used as competitive reagents to modulate the fluorescence changes of the system. However, lanthanide metal ions as inducers for aggregation-induced emission enhancement in nanosystems is rare. Herein, we report a "turn on-off-on" fluorescent switch for cascade detection of acid phosphatase (ACP) and adenosine triphosphate (ATP) based on the competitive coordination of samarium ions (Sm3+). Novel copper nanoclusters (CuNCs) with long wavelength emission (614 nm) stabilized by glutathione (GSH) and glycylglycine (Gly-Gly) have been confirmed to have AIE property. With the continuous aggregation of GSH/Gly-Gly CuNCs under the induction of Sm3+, the fluorescence of the system increased to achieve the "turn-on" process. The coordinated behaviour between Sm3+ and GSH/Gly-Gly CuNCs is discussed. Due to the strong metal coordination ability of ATP, the Sm3+ coordinated with the GSH/Gly-Gly CuNCs is competed out, resulting in the fluorescence "turn-off" process of the system. As the substrate of enzymatic hydrolysis of ACP, with the continuous hydrolysis of ATP by ACP, Sm3+ coordinates with GSH/Gly-Gly CuNCs again, which leads to the AIE effect and realize the fluorescence "turn-on" process of the system. This strategy results in ATP linear range of 0.508 ~ 120.0 μM with a detection limit of 0.508 μM (S/N = 3) and ACP linear range of 0.011 ~ 30.0 U·L-1 with a detection limit of 0.011 U·L-1 (S/N = 3). Application to biologic samples was successful.

Design and development of opto-electrochemical biosensing devices for diagnosing chronic kidney disease

Chronic kidney disease (CKD) is emerging as one of the major causes of the increase in mortality rate and is expected to become 5th major cause by 2050. Many studies have shown that it is majorly related to various risk factors, and thus becoming one of the major health issues around the globe. Early detection of renal disease lowers the overall burden of disease by preventing individuals from developing kidney impairment. Therefore, diagnosis and prevention of CKD are becoming the major challenges, and in this situation, biosensors have emerged as one of the best possible solutions. Biosensors are becoming one of the preferred choices for various diseases diagnosis as they provide simpler, cost-effective and precise methods for onsite detection. In this review, we have tried to discuss the globally developed biosensors for the detection of CKD, focusing on their design, pattern, and applicability in real samples. Two major classifications of biosensors based on transduction systems, that is, optical and electrochemical, for kidney disease have been discussed in detail. Also, the major focus is given to clinical biomarkers such as albumin, creatinine, and others related to kidney dysfunction. Furthermore, the globally developed sensors for the detection of CKD are discussed in tabulated form comparing their analytical performance, response time, specificity as well as performance in biological fluids.

Design and Engineering of a Palm-Sized Optical Immunosensing Device for the Detection of a Kidney Dysfunction Biomarker

Creatinine is one of the most common and specific biomarkers for renal diseases, usually found in the serum and urine of humans. Its level is extremely important and critical to know, not only in the case of renal diseases, but also for various other pathological conditions. Hence, detecting creatinine in clinically relevant ranges in a simplistic and personalized manner is interesting and important. In this direction, an optical sensing device has been developed for the simple, point-of-care detection of creatinine. The developed biosensor was able to detect creatinine quantitatively based on optical signals measured through a change in color. The sensor has been integrated with a smartphone to develop a palm-sized device for creatinine analysis in personalized settings. The sensor has been developed following facile chemical modification steps to anchor the creatinine-selective antibody to generate a sensing probe. The fabricated sensor has been thoroughly characterized by FTIR, AFM, and controlled optical analyses. The quantitative analysis is mediated through the reaction between picric acid and creatinine which was detected by the antibody-functionalized sensor probe. The differences in color intensity and creatinine concentrations show an excellent dose-dependent correlation in two different dynamic ranges from 5 to 20 μM and 35 to 400 μM, with a detection limit of 15.37 (±0.79) nM. Several interfering molecules, such as albumin, glucose, ascorbic acid, citric acid, glycine, uric acid, Na⁺, K⁺, and Cl^-, were tested using the biosensor, in which no cross-reactivity was observed. The utility of the developed system to quantify creatinine in spiked serum samples was validated and the obtained percentage recoveries were found within the range of 89.71-97.30%. The fabricated biosensor was found to be highly reproducible and stable, and it retains its original signal for up to 28 days.

A highly selective fluorescent sensor for chlortetracycline based on histidine-templated copper nanoclusters

In this study, histidine-protected copper nanoclusters (Cu NCs@His) were established by using a one-pot method, which histidine and ascorbic acid were applied as the template and reducing agent, respectively. The as-developed Cu NCs@His endued green emission wavelength at 494 nm with the excitation of 378 nm. The Cu NCs@His exhibited green fluorescence under UV light (365 nm). Using Cu NCs@His as a pattern nanosensor, the fluorescent "turn off" mechanism was fabricated for the determination of chlortetracycline in the light of the linear decrease of fluorescence intensities around 494 nm. The chlortetracycline conducted as a quencher, leading to reveal an excellent linear relationship between ln(F₀/F) of Cu NCs@His and chlortetracycline concentrations with the range of 0.5-200 μM, and the detection limit was 0.876 μM. The fluorescence quenching of Cu NCs@His revealed excellent selectivity for chlortetracycline over other potential interfering substances in the human body. This strategy was exhibited to be a convenient sensing platform for the detection of chlortetracycline in real medical samples, which could unfold a brand new and direct system for the sensing of chlortetracycline in real samples.

Synthesis of Copper Nanoclusters and Their Application for Environmental Pollutant Probes: A Review

Copper nanoclusters (CuNCs) as a new type of probe for environmental contaminants are gaining increasing attention because of its low cost, superior water dispersibility, wide availability and excellent optical properties. Compared with the other probes such as quantum dots and organic dyes, CuNCs show much more potential in practical application for their excellent photostability, large Stokes shift, low toxicity and other preponderance, especially in the fields of biosensing and environmental monitoring. Recently, the template-assisted synthesis of metal nanoclusters (MNCs) has been widely studied. A variety of templates such as proteins, small thiol molecules, polymers, and DNA with different spatial configuration have been used for the preparation of MNCs so far. This review primarily described recent advances in CuNCs in terms of the synthesis of CuNCs from different templates, the methods to improve the fluorescence (FL) properties of CuNCs, as well as the basic detection mechanisms based on the FL properties or catalytic properties. Finally, to promote the practical application of CuNCs probes, the challenges and prospects of CuNCs multifunctional probes are also discussed.

A flexible mesoporous Cu doped FeSn–G–SiO2 composite based biosensor for microalbumin detection

A new mesoporous Cu-doped FeSn–G–SiO₂ (CFSGS) based biosensor was developed for the detection of microalbumin in urine samples. The mechanically flexible FeSn modified sensor was fabricated at room temperature. These demonstrations highlight the unexplored potential of FeSn for developing novel biosensing devices. It is extremely sensitive and selective. Surfactant-aided self-assembly was used to synthesise the mesoporous CFSGS. The large surface area due to the mesopore presence in the CFSG surface that has been composited inside the mesoporous SiO₂ boosted the electrochemical detection. The linear range and detection limit of microalbumin under optimum circumstances were 0.42 and 1 to 10 μL, respectively. This easily fabricated mesoporous CFSGS provided a fast response with high sensitivity, and good selectivity. The sensor's reusability and repeatability were also quite high, with just a 90 percent drop after 4 weeks of storage at ambient temperature. The biosensor also demonstrated high selectivity against typical potential interfering chemicals found in urine (ascorbic acid, urea, and sodium chloride). The good performance of the mesoporous CFSGS biosensor was validated by measuring microalbumin, and the findings indicated that this sensing device performed very well.

Microalbumin sensing mechanism with electrochemical performance system.