A simple smartphone-assisted paper-based colorimetric biosensor for the detection of urea adulteration in milk based on an environment-friendly pH-sensitive nanocomposite

Advancements of paper-based microfluidics and organ-on-a-chip models in cosmetics hazards

Cosmetics have been used in society for centuries for beautification and personal hygiene maintenance. Modern cosmetics include various makeup, hair, and skincare products that range from moisturizers and shampoos to lipsticks and foundations and have become a quintessential part of our daily grooming activities. However, dangerous adulterants are added during the production of these cosmetics, which range from heavy metals to microbial contaminants. These adulterants not only reduce the quality and efficacy of cosmetic products but also pose a significant risk to human health. Detecting the presence of adulterants in cosmetics is crucial for regulating substandard cosmetic products in the industry. The conventional methods to detect such adulterants and quality testing are expensive and take a lot of effort, particularly when involving advanced analytical detection and clinical trials. Recently, efficient methods such as microfluidic methods have emerged to detect adulterants rapidly. In this review, we mainly focus on various adulterants present in cosmetics and their detection using paper-based microfluidic devices. In addition, this review also sheds light on the organ-on-a-chip model with the goal of developing a human tissue model for cosmetic testing. Combined, these approaches provide an efficient, inexpensive, and sustainable approach for quality testing in the cosmetics industry.

Nitrogen-Doped Carbon Dots Prepared via Microchannel Method for Visual Detection of Copper Ions

Copper ions (Cu2+) play a crucial role in biological processes; however, excessive intake can result in severe health problems. Current methods for detecting copper ions are both expensive and complex. Therefore, there is a need for efficient and straightforward visual detection methods. In this study, novel nitrogen-doped carbon dots (N-CDs) were synthesized via a microchannel method using diethylenetriamine and citric acid as precursors and were characterized by TEM, XRD, and IR, among others. The N-CDs demonstrated high selectivity and strong fluorescence, showing a linear quenching response to copper ions with a detection limit of 46 nM, whereas other common metal ions, such as Ca2+ and Mg2+, exhibited negligible interference even at higher concentrations. These N-CDs were subsequently applied to test paper, allowing for on-site visual and quantitative detection of copper ions via a colorimetric method. This approach provides a novel solution for the rapid detection of copper ions, with significant potential in environmental monitoring, public health, and industrial applications.

Synergistic applications of quantum dots and magnetic nanomaterials in pathogen detection: a comprehensive review

The rapid and accurate detection of pathogens is crucial for effective disease prevention and management in healthcare, food safety, and environmental monitoring. While conventional pathogen detection methods like culture-based techniques and PCR are sensitive and selective, they are often time-consuming, require skilled operators, and are not suitable for point-of-care or on-site testing. To address these limitations, innovative sensor technologies have emerged that leverage the unique properties of nanomaterials. Quantum dots (QDs) and magnetic nanomaterials are two classes of nanomaterials that have shown particular promise for pathogen sensing. This review comprehensively examines the synergistic applications of QDs and magnetic nanomaterials for detecting bacteria, viruses, phages, and parasites.

Enhancing mycotoxins detection through quantum dots-based optical biosensors

Quantum dot-based optical biosensors represent a significant advancement for detection of mycotoxins that are toxic secondary metabolites produced by fungi and pose serious health risk effects. This review highlights the importance of detection of filamentous fungi such as Aspergillus, Penicillium, Fusarium, Claviceps, and Alternaria in mycotoxin production, leading to contamination of agricultural products and subsequent health issues. Conventional detection methods such as thin-layer chromatography, high-performance liquid chromatography, gas chromatography, and enzyme-linked immunosorbent assay are discussed with their respective advantages and limitations. Then the innovative use of quantum dots (QDs) in fabrication of biosensors is discussed in the present review, emphasizing their unique optical properties, such as size-tunable fluorescence and high photostability. These properties enable the development of highly sensitive and specific biosensors for mycotoxin detection. The application of QD-based biosensors, based on their applied bioreceptors including antibodies, molecularly imprinted polymers and aptamer, is explored through various detection strategies and recent advancements. The review concludes by underscoring the potential of QD-based biosensors in providing portable, cost-effective, and efficient solutions for real-time monitoring of mycotoxin for enhancing food safety and protecting public health.

Detection of urea in milk by urease-inorganic hybrid nanoflowers combined with portable colorimetric microliter tube

A simple one-pot green synthesis method was used to prepare urease-inorganic hybrid nanoflowers (UE-HNFs), which had a high surface-to-volume ratio to improve enzyme catalytic efficiency and make urease reusable. A portable colorimetric microliter tube based on urease-inorganic hybrid nanoflowers (UE-HNFs-PCMT), as an urea colorimetric biosensor, was developed for determining urea concentration in milk. The combination of urea colorimetric biosensor and a smartphone is used for capturing the colour change of milk after reaction. There was a good linear relationship between colour intensity of the image (Δ intensity) and urea concentration (43-600 mg L-1), with a detection limit of 12.81 mg L-1. UE-HNFs-PCMT has the advantages of no need for complex equipment, easy operation, reusability, low detection cost, good portability, and environmental friendliness and can achieve urea detection in milk.

A biosensor integrating the electrochemical and fluorescence strategies for detection of aflatoxin B1 based on a dual-functionalized platform

BACKGROUND

Aflatoxin B1 (AFB1), is a potent hepatic carcinogen which causes cancer by inducing DNA changes in the liver cells. Variety of methods have been developed for detection of AFB1 which are based on single mode detection strategy. Fabrication of novel platform which are compatible for multimodal detection of AFB1 provide robust performance for reliable detection of AFB1. In this study, we aimed to develop a robust biosensing platform that combines electrochemical and fluorescence techniques for the sensitive and specific detection of Aflatoxin B1.

RESULTS

The sensing platform includes the magnetic core-shell Fe3O4@AuNPs and zeolitic imidazolate framework-8 (ZIF-8). In electrochemical mode, the applied voltametric approach was used through functionalization of glassy carbon electrode and exhibited a linear range between 0.5 and 10000 pg mL-1 with LOD of 0.32 pg mL-1. Fluorescence analysis was based on the FRET on/off status of FAM-functionalized aptamer deposited on the same platform. The FAM emission recovered by the addition of AFB1 concentration in the range of 6-60 fg mL-1 with the LOD of 0.20 fg mL-1. The real sample analysis demonstrated satisfactory relative recoveries in the range of 92.81-105.32 % and 91.66-106.66 % using the electrochemical and fluorescence methods, respectively, and its reliability was confirmed by the HPLC technique.

SIGNIFICANCE

The experimental results affirm that the proposed aptasensor serves as a sensitive, efficient, and precise platform for monitoring AFB1 in both electrochemical and fluorescence detection approaches. Proposed strategy showed efficient selectivity among different analytes and was reproducible. Furthermore, the applicability of biosensor was confirmed in food and biological samples.

Enhancing milk quality assessment with watermelon (Citrullus lanatus) urease immobilized on VS2-chitosan nanocomposite beads using response surface methodology

An eco-friendly hydrothermal method synthesized VS2 nanosheets. Several spectroscopic and microscopic approaches (TEM) were used to characterize the produced VS2 nanosheet microstructure. VS2, Chitosan, and nanocomposite were used to immobilize watermelon (Citrullus lanatus) urease. Optimization using the Response Surface Methodology and the Box-Behnken design yielded immobilization efficiencies of 65.23 %, 72.52 %, and 87.68 % for chitosan, VS2, and nanocomposite, respectively. The analysis of variance confirmed the mathematical model's validity, enabling additional research. AFM, SEM, FTIR, Fluorescence microscopy, and Cary Eclipse Fluorescence Spectrometer showed urease conjugation to the matrix. During and after immobilization, FTIR spectra showed a dynamic connectivity of chemical processes and bonding. The nanocomposite outperformed VS2 and chitosan in pH and temperature. Chitosan and VS2-immobilized urease were more thermally stable than soluble urease, but the nanocomposite-urease system was even more resilient. The nanocomposite retained 60 % of its residual activity after three months of storage. It retains 91.8 % of its initial activity after 12 reuse cycles. Nanocomposite-immobilized urease measured milk urea at 23.62 mg/dl. This result was compared favorably to the gold standard p-dimethylaminobenzaldehyde spectrophotometric result of 20 mg/dl. The linear range is 5 to 70 mg/dl, with a LOD of 1.07 (±0.05) mg/dl and SD of less than 5 %. The nanocomposite's ksel coefficient for interferents was exceptionally low (ksel < 0.07), indicating urea detection sensitivity. Watermelon urease is suitable for dairy sector applications due to its availability, immobilization on nanocomposite, and reuse.

Microplate-based 3D-printed image box for urea determination in milk by digital image colorimetry

In this study, we describe a rapid and high-throughput smartphone-based digital colorimetric method for determining urea in milk. A compact and cost-effective 3D-printed image box microplate-based system was designed to measure multiple samples simultaneously, using minimal sample and reagent volumes. The apparatus was applied for the quantification of urea in milk based on its reaction with p-dimethylaminobenzaldehyde (DMAB). The predictive performance of calibration was evaluated using RGB and different colour models (CMYK, HSV, and CIELAB), with the average blue (B) values of the RGB selected as the analytical signal for urea quantification. Under optimized conditions, a urea concentration linear range from 50 to 400 mg L-1 was observed, with a limit of detection (LOD) of 15 mg L-1. The values found with the smartphone-based DIC procedure are in good agreement with spectrophotometric (spectrophotometer and microplate treader) and reference method (mid-infrared spectroscopy) values. This proposed approach offers an accessible and efficient solution for digital image colorimetry, with potential applications for various target analytes in milk and other fields requiring high-throughput colorimetric analysis.

Recent advancements of smartphone-based sensing technology for diagnosis, food safety analysis, and environmental monitoring

The emergence of computationally powerful smartphones, relatively affordable high-resolution camera, drones, and robotic sensors have ushered in a new age of advanced sensible monitoring tools. The present review article investigates the burgeoning smartphone-based sensing paradigms, including surface plasmon resonance (SPR) biosensors, electrochemical biosensors, colorimetric biosensors, and other innovations for modern healthcare. Despite the significant advancements, there are still scarcity of commercially available smart biosensors and hence need to accelerate the rates of technology transfer, application, and user acceptability. The application/necessity of smartphone-based biosensors for Point of Care (POC) testing, such as prognosis, self-diagnosis, monitoring, and treatment selection, have brought remarkable innovations which eventually eliminate sample transportation, sample processing time, and result in rapid findings. Additionally, it articulates recent advances in various smartphone-based multiplexed bio sensors as affordable and portable sensing platforms for point-of-care devices, together with statistics for point-of-care health monitoring and their prospective commercial viability.