A Paper-Based Analytical Device Integrated with Smartphone: Fluorescent and Colorimetric Dual-Mode Detection of β-Glucosidase Activity

A colour sensor integrated into a microcontroller platform as a reliable tool for measuring pH changes in biochemistry applications

Colorimetry is a widely used technique for optical detection in point-of-care testing and on-site detection. Although some studies employ a multiplex approach to analyse coloured solutions, many still analyse one sample at a time. We have prepared a simple and affordable colorimetric assay based on a TCS34725 colour sensor (ams-OSRAM) integrated into an M5Stack module and an RGB LED module both inserted into a 3D printed frame. We found that the colorimetric assay can be easily transferred to a colour sensing platform, and the signal range obtained using the prepared colorimeter is more than 200 times larger than that obtained using digital image colorimetry (DIC) for the same samples containing cholinesterase or urease as a model enzyme providing a change in pH of the processed solution. The assay appears to be ready for practical use.

Advancement in Biosensor Technologies of 2D MaterialIntegrated with Cellulose-Physical Properties

This review paper provides an in-depth analysis of recent advancements in integrating two-dimensional (2D) materials with cellulose to enhance biosensing technology. The incorporation of 2D materials such as graphene and transition metal dichalcogenides, along with nanocellulose, improves the sensitivity, stability, and flexibility of biosensors. Practical applications of these advanced biosensors are explored in fields like medical diagnostics and environmental monitoring. This innovative approach is driving research opportunities and expanding the possibilities for diverse applications in this rapidly evolving field.

Sensitive determination of naftazone using carbon quantum dots nanoprobe by fluorimetry and smartphone-based techniques

A simple, fast, and direct mix-and-read spectrofluorimetric method has been developed for the sensitive determination of naftazone (NFZ) utilizing graphene quantum dots (GQDs) as a greener and highly luminescent nanosensor. NFZ effectively quenches the strong fluorescence of GQDs at λex/λem of 350/440 nm via the inner filter effect mechanism. The nanosensor exhibits excellent linearity for NFZ over the concentration range of 0.46 to 186 μM with a limit of detection of 0.04 μM. The proposed method was validated for the successful determination of NFZ in tablets and on manufacturing equipment surfaces with good % recoveries of 98.4-101.6 and 96.3 - 102.2%, respectively. Furthermore, an integrated smartphone-based reader has been implemented and successfully applied for the determination of NFZ. The smartphone-based reader consists of a 365 nm UV torch as an excitation source, a smartphone for recording images, and smartphone-powered image analysis software for signal interpretation, together with a paper-based analytical device (PAD) utilizing filter paper as a substrate and correction fluid as a barrier for creation of detection zones. This smart platform showed excellent sensitivity with a limit of detection down to 0.12 nmol/zone, and it could be used for in-site determination of NFZ, especially for the limited resources laboratories.

Smartphone-integrated paper-based biosensor for sensitive fluorometric ethanol quantification

The development of fluorometric paper-based analytical devices (fPADs) integrated with smartphone for fluorometric quantification of ethanol in an instrument-free and portable setup is described. The NAD+-dependent alcohol dehydrogenase immobilized within chitosan modified paper substate was utilized as a bio-recognition element and enzymatically generated NADH was used as a fluorescent probe. 3D-printed imaging setup which houses a paper chip holder and UV-light emitting device (LED) was developed for rapid, accurate capture of the fluorescent images. The biocompatible chitosan layer covering the paper provides a feasible environment for enzyme immobilization and enhances the fluorescence signal. The developed fPADs exhibited high sensitivity for ethanol detection and has a linear range for ethanol detection from 17 µM to 8.75 mM (R2 =0.99). Additionally, the fPADs were applied to quantify ethanol in four different wine samples including red, white, rose, and sparkling wines successfully. Moreover, the fPADs produce reproducible signals without loss of enzyme activity for at least 14 days and ~80% activity remained till 28 days. Thus, the proposed approach can provide a facile, affordable, portable, and instrument-free tool for the onsite quantification of ethanol in real samples and is applicable for food quality controls.

A novel "Turn-on" fluorometric assays triggered reaction for β-glucosidase activity based on quercetin derived silicon nanoparticles and its potential use for cell imaging

β-Glucosidase (β-Gluco) is an enzyme that is crucial to numerous diseases, including cancer, and in sector of industries, it is used in the manufacturing of food. Measuring its enzymatic activity is critical for biomedical studies and other activities. Herein, we have developed a novel and precise fluorescent sensing method for measuring β-Gluco activity based on the production of yellow-green fluorescent quercetin-silicon nanoparticles (Q-SiNPs) produced from quercetin (QN) as a reducing agent and 3-[2-(2-aminoethyl amino) ethylamino] propyl-trimethoxy silane (AEEA) as a silane molecule. β-Gluco hydrolyzed quercetin-3-O-β-d-glucopyranoside (QO-β-DG) to produce QN, which was then used to produce Q-SiNPs. Reaction parameters, including temperature, time, buffer, pH, and probe concentration, were carefully tuned in this study. Subsequently, the fluorescence intensity was performed, showing good linearity (R2 = 0.989), a broad linear dynamic range between 0.5 and 12 U L-1, and a limit of detection (LOD) as low as 0.428 U L-1, which was proven by fluorescence measurements. Most importantly, various parameters were detected and characterized with or without β-Gluco. The designed probe was successively used to assess β-Gluco activity in human serum and moldy bread. However, the mathematical findings revealed recoveries for human serum ranging from 99.3 to 101.66% and for moldy bread from 100.11 to 102.5%. Additionally, Q-SiNPs were well suited to being incubated in vitro with L929 and SiHa living cells, and after using an Olympus microscope, imaging showed good fluorescence cell images, and their viability evinced minimal cytotoxicity of 77% for L929 and 88% for SiHa. The developed fluorescence biosensor showed promise for general use in diagnostic tests. Therefore, due to this outstanding sensing modality, we anticipate that this research can provide a novel schematic project for creating simple nanostructures with a suitable plan and a green synthetic option for enzyme activity and cell imaging.