Paper Strips Research Articles

A Ratiometric Fluorescence Probe for Visualized Detection of Heavy Metal Cadmium and Application in Water Samples and Living Cells

Heavy metal cadmium (II) residuals have inflicted severe damage to human health and ecosystems. It has become imperative to devise straightforward and highly selective sensing methods for the detection of Cd2+. In this work, a ratiometric benzothiazole-based fluorescence probe (BQFA) was effortlessly synthesized and characterized using standard optical techniques for the visual detection of Cd2+ with a change in color from blue to green, exhibiting a significant Stokes shift. Moreover, the binding ratio of BQFA to Cd2+ was established as 1:1 by the Job’s plot and was further confirmed by FT-IR and 1HNMR titrations. The ratiometric fluorescence response via the ICT mechanism was confirmed by DFT calculations. Furthermore, the limit of detection for detecting Cd2+ was determined to be 68 nM. Furthermore, it is noteworthy that BQFA showed good performance in real water samples, paper strips, smartphone colorimetric identification, and cell imaging.

CRISPR-Cas12a based HSV DNA detection method using quantum dot-labeled immunochromatographic strips

Herpes simplex virus (HSV) infection poses a significant public health challenge, particularly affecting vulnerable populations such as pregnant women, newborns, and immunocompromised individuals. Traditional diagnostic methods for HSV are often time-consuming, requiring specialized expertise and infrastructure, resulting in delays and limitations in resource-limited regions. In this research, we established a novel detection method that integrates CRISPR-Cas12a with Recombinase Assisted Amplification (RAA), enabling the sensitive and specific detection of HSV DNA. Compared to TaqMan PCR, our CRISPR-Cas12a-based lateral flow assay (CRI-LFA) using universal primers demonstrated a sensitivity of 90.38 %, specificity of 98.08 %, positive predictive value (PPV) of 100 %, negative predictive value (NPV) of 91.22 %, kappa value of 0.904, and an area under the receiver operating characteristic curve (AUC) of 0.973. The subsequent typing tests on our platform for HSV-1 and HSV-2 showed a sensitivity of 100 % (95 % CI: 74.12 %–100 %) and 95.83 % (95 % CI: 86.02 %–99.26 %), respectively. Specificity was 97.85 % (95 % CI: 92.49 %–99.62 %) for HSV-1 and 96.64 % (95 % CI: 85.39 %–98.54 %) for HSV-2. The kappa values were 0.906 for HSV-1 and 0.883 for HSV-2, with PPV of 84.6 % and 97.7 %, and NPV of 100 % and 91.7 %, respectively. Our portable paper strip assay provides a convenient and user-friendly testing option suitable for decentralized settings. This approach has the potential to facilitate early detection and enhance public health efforts in controlling HSV transmission.

Rapid reagent-free anaemia screening using plant-derived “HemoQR” paper-strips and smartphone: A study on 200 human subjects

Detecting anaemia in resource-limited settings is challenging due to limited access to diagnostic tools, healthcare infrastructure, and trained personnel, often resulting in underdiagnosis and delayed treatment. This study aims to evaluate HemoQR, a novel point-of-care (POC) diagnostic method for haemoglobin (Hb) level detection using a smartphone-based system integrated with a paper strip without needing any reagent or additional auxiliary device. The goal is to assess the efficacy of this portable, user-friendly, rapid and accurate alternative for Hb measurement in large-scale intervention programmes such as Anaemia-mukt Bharat (AMB), which is crucial for diagnosing anaemia and monitoring various health conditions. The method involves the transfer of one drop of the blood sample to a paper strip that is made indigenously using plant based cellulosic sources for optimal functionality. The colour signal around the test spot is quantitatively analysed using a smartphone camera equipped with a custom application. The application processes the images through a machine learning algorithm to determine the Hb concentration. The system was evaluated in a clinical trial involving 200 participants, comparing its performance with the gold-standard laboratory Hb assay using automated haematology analyser. The smartphone-based method demonstrated high sensitivity (87.09 %) and specificity (96.11 %) for anaemia screening, as compared with laboratory results. The average detection time was significantly reduced to under q minute, and the system showed excellent user-friendliness and portability with no auxiliary device needed beyond the smartphone. Clinical trial results indicated that the device was accurate and reliable across different Hb levels. Summarily, HemoQR evidenced to be a promising tool for POC diagnostics. Its high accuracy, rapid results, and ease of use make it suitable for both clinical settings and remote areas with limited access to laboratory facilities. Future research will prioritize further validation and integration of the anaemia screening outcome with electronic health records from a large population cohort. This will help identify early indicators and signals of numerous emerging disease burdens that could escalate into secondary and tertiary health crises if not addressed in time.

Exploring Selective Fluorescence Turn-On Sensing of Caspase-3 with Molybdenum Disulfide Quenched Copper Nanoclusters: FRET Biosensor.

Sensing caspase-3 activity is essential for understanding the role of apoptosis in cancer dynamics, controlling therapeutic strategies, and improving patient care in cancer treatment. In this study, we demonstrate a highly sensitive recombinant human caspase-3 (rhC3) detection technique in biological fluids. This technique uses a copper nanocluster stabilized with bovine serum albumin (BSA-CuNCs) as a metal-based fluorescent biosensor, conjugated with anti-human caspase-3 (ahC3). To turn its fluorescence off, molybdenum disulfide nanosheets (MoS2 NSs) are added; this partnership is termed ahC3@BSA-CuNCs/MoS2 nanocouple. In the presence of rhC3, the energy transfer process is affected by strong ahC3/rhC3 interactions. When in close proximity, the rhC3 molecules cause detachment of the nanocluster from the MoS2 NS surface by attracting the ahC3 component of the nanocluster. This increases the distance between the nanocluster and quencher with a consequent restoration of intensity. As the concentration of rhC3 increases, the fluorescence intensity of the system also increases. A proportional response is seen in the concentration between 0.1 and 1.3 ng/mL with a very low limit of detection of 2.75 pg/mL and a quantification limit of 8.60 pg/mL. A simple filter paper strip was made to visually identify the presence of rhC3 under UV light.

Unveiling Milk Safety in Chennai: A Comprehensive Evaluation of Adulteration Across Diverse Milk Sources

Introduction: Milk is a complex biological fluid made up mostly of water, carbohydrates, lipids, proteins, and many bioactive compounds. This extremely nutritious food contains vital components like energy-giving lactose, fat, bone-forming calcium, minerals, body-building proteins, and health-promoting vitamins necessary for all age groups. To increase the protein content, SNF, fat %, adulterants are added to milk, which unnaturally raising the milk's quality. Regretfully, there are adulterants that can have serious long-term health effects. Infants may experience renal failure and even die if they consume melamine at levels higher than what is considered safe. Objectives: This study aims to systematically evaluate the extent and nature of all milk adulteration (breast, branded vegan, unbranded vegan milk, direct cow milk and packaged cow milk) in the Chennai city, Tamil Nadu, India. Methods: The study was conducted for a period of 3 months from May 2024 to July 2024. The collected milk samples were analysed using Delstrips paper strips. Results: The findings reveal a widespread presence of adulterants, with starch being the most prevalent across nearly all milk types. There were no statistically significant differences seen between government milk, private branded cow milk, and private direct milk in adulterant's sucrose and neutralizers. In contrast, almond milk offers a viable alternative for those seeking a vegan or lactose-free option, particularly for adults and older children. Conclusion: Milk Adulteration poses a significant threat to public health, economies and the diary industry worldwide. The prevalence of adulteration, particularly in developing countries, highlights the need for improved regulatory frameworks, enhanced testing methods, and vigilant monitoring. This study has demonstrated the severity of milk adulteration, its consequences, and the imperative for collective action. The current research demonstrates that both breast milk and almond milk, when used appropriately, are safe options within their respective contexts.

Lack of association between the length of anogenital distance and vaginal pH in women with endometriosis.

We investigated the association between the length of anogenital distance (AGD) and intra-vaginal pH, an indicator of vaginal eubiosis or dysbiosis, in women with endometriosis. A prospective cohort study was performed including patients with (n = 67) and without (n = 40) endometriosis undergoing surgery between July 2021 and June 2022. AGD was measured from the posterior fourchette to the center of the anus using digital caliper and vaginal pH was measured by inserting pH paper strip mostly into the posterior fornix. There was no significant difference in the median AGD among control women (n = 40) (21.5 mm), women with revised-American Society of Reproductive Medicine stage I-II endometriosis (n = 27) (22.0 mm) and stage III-IV endometriosis (n = 40) (20.0 mm). In contrast, a significant difference of vaginal pH was observed among groups (p = 0.012) and between groups: control versus stage I-II, p = 0.004; stage I-II, versus stage III-IV, p = 0.037. After adjusting different confounding variables, the univariate analysis showed that women with endometriosis are less likely to have an alkaline vaginal pH (≥4.5) (OR [95% CI] = 0.40 [0.17, 0.93], p = 0.034). Multivariate analysis revealed that AGD or any of the other variables did not serve as an independent risk factor to predict the presence of endometriosis. This study with Japanese women suggests a lack of association between length of AGD, either shorter or longer, and the status of vaginal pH or the presence of endometriosis in pelvis.

Photochemical and electrochemical behavior of a molecular probe: Fluorescence on-off-on response to detect multiple ions (Cu2+, ClO− and CN−) with different rate of reaction

A molecular probe 3 containing phenyl substituted imidazolyl unit and diaminomaleonitrile (DAMN) moiety has been synthesized and characterized. Photophysical and electrochemical behavior probe 3 were studied in partial aqueous medium (ACN/H2O, 9.5:0.5 v/v). Probe 3 upon interaction with different class of ions showed sensitivity for Cu2+, ClO− and CN− ions with different response time and reaction rates due to variation in intramolecular charge transfer (ICT) process. Both Cu2+ and ClO− ions displayed enhanced emission due to hydrolysis of imine bond to form compound 2 in the medium whereas, with CN− fluorescence quenching was observed due to the deprotonation of –OH/–NH2 functions. The kinetic and optical behavior of the probe suggested that interaction occurred in two steps with Cu2+ (complexation and hydrolysis; absk1,2,3(Cu2+) = 1.17, 0.74 and 0.06 s−1) and ClO− (hydrolysis and deprotonation; absk1,2(ClO−) = 3.0 and 0.60 s−1) ions while CN− (absk1,2(CN−) = 2.13 and 1.66 s−1) induces deprotonation in one step. The interaction of probe 3 with ClO− was relatively fast than with Cu2+/CN− ions. Job's plot analysis between probe 3 and ions revealed a 1:1 (Cu2+/ClO−) and 1:2 (CN−) ratio stoichiometry with good limit of detection (nM) and binding affinity (LOD, 17; KCu2+ = 3.23 × 106 M−1; LOD, 18.5; KClO− = 5.23 × 105 M−1 and LOD, 23.2; KCN− = 5.50 × 109 M−2) respectively. Probe 3 displayed a naked–eye sensitive fluorescence response to detect tested ions on test paper strips and good recovery percentage of ions in real water sample analysis.

Accordion-Structured Hydrogel Battery Capable of Maintaining Ion Gradients for Extended Periods.

Inspired by the electric eel, biomimetic, biocompatible energy storage, and power generation technologies show promise for applications in portable and wearable electronic devices by mimicking the electric cell tandem structure of the electric eel and utilizing ionic gradients between hydrogel compartments to generate electricity. Previously, inspired by the unique morphology of the torpedo fish, an artificial flexible power source that can output a large current was introduced. This power source uses a hydrogel-infused paper hybrid to create, accordionize, and reconfigure arbitrary-sized gel films in series and parallel, and the power output of the flexible battery was significantly enhanced. However, maintaining the ionic gradient of hydrogel batteries during storage remains a challenge. Here, by borrowing the isolation properties of the accordion structure, we propose a unique paper accordion structure design to fabricate an Accordion-Structured Hydrogel Battery (ASHB). Pretreatment of hydrogel-injected paper strips improved storage stability and maintained the ionic gradient of hydrogel cells in the nonworking state, so that the cell's gradient retention time after the assembly is completed is increased by at least 30 h compared to stacking, and its per-cell operating voltage is still able to reach. The design also makes the assembly and use of flexible batteries more modular and holistic. In the future, it may be possible to power the cells with ions generated by the human body or the metabolites of living organisms, leading to the development of more efficient, sustainable, and eco-friendly power solutions.

A Microbial Cocaine Bioreporter

The continuous emergence of new illegal compounds, particularly psychoactive chemicals, poses significant challenges for current drug detection methods. Developing new protocols and kits for each new drug requires substantial time, effort, and dedicated manpower. Whole-cell bacterial bioreporters have been proven capable of detecting diverse hazardous compounds in both laboratory and field settings, identifying not only single compounds but also chemical families. We present the development of a microbial bioreporter for the detection of cocaine, the nervous system stimulant that is the second-most widely used illegal drug in the US. Escherichia coli was transformed with a plasmid containing a bacterial luxCDABEG bioluminescence gene cassette, activated by a cocaine-responsive signaling cascade. The engineered bioreporter is demonstrated to be a sensitive and specific first-generation detection system for cocaine, with detection thresholds of 17 ± 8 μg/L and 130 ± 50 μg/L in a buffer solution and in urine, respectively. Further improvement of the sensor’s performance was achieved by altering the nucleotide sequence of the PBen gene promoter, the construct’s sensing element, using accelerated site-directed evolution. The applicability of ready-to-use paper strips with immobilized bioreporter cells was demonstrated for cocaine detection in aqueous solutions.

Ultrasensitive Rapid Antigen Test by Geometric Lateral Flow Assays and Highly Doped Upconversion Nanoparticles.

The paper-based lateral flow assay (LFA) testing strips are currently the most widely used for point-of-care testing (POCT), valued for their rapid result turnaround times in a few minutes. However, their sensitivity has been limited. Upconversion nanoparticles (UCNPs), especially highly doped ones, have emerged as promising luminescent reporters to enhance the LFA sensitivity. These UCNPs exhibit a nonlinear enhancement in luminescence with excitation power density, necessitating higher power densities for higher brightness. In this study, we utilized a geometric paper strip design to minimize the immune reaction area and maximize the excitation power density, enabling ultrasensitive detection of the SARS-CoV-2 nucleoprotein antigen. This design also slowed the antigen flow on the paper strip, extending the reaction time between antigen and antibody, thereby enhancing the efficiency of the immune reaction. Through this design, our approach achieved over a 100-fold enhancement in the limit of detection (LOD) compared with the widely used LFAs, based on gold colloidal nanoparticles and europium nanoparticles. This innovation expands the scope of LFA applications that require a low LOD.

A highly sensitive fluorescent sensor for reversible visual detection of fluoride ion and trace water in food products

A simple diphenylimidazole-based fluorescent sensor (DIP) had been designed for reversible fluorescence sensing of F− and trace water. The sensor showed superior selectivity for F− compared to other anions with fluorescence “turn on” mode. After adding F− to CH3CN solution of DIP, the emission color of DIP changed markedly from weak blue to strong cyan, which could be facilely discerned by the naked eye. The various technical analysis, including spectroscopies, 1H NMR titration and DFT calculation, indicated that the deprotonation of imidazole –NH and –OH occurred in the presence of F−. The detection limit of DIP toward F− could reach as low as 72.3 nM. Moreover, F−-induced deprotonation of DIP-F− system exhibited high sensitivity for water with the detection limit of 0.0015 vol%. The reversible switching characteristic of DIP prompted it suitable for the construction of molecular logic gate. In addition, DIP and DIP-F− were successfully applied to the determination of F− content in toothpaste and water content in table salt, sugar and tea, respectively. Moreover, DIP and DIP-F−-coated filter paper strips could be used as fluorescent display materials for inkless writing with repeatability.

Aminothiophenol and 7-diethylamino-4-hydroxycoumarin derived probe for reversible turn off–on–off detection of Cu2+ ions and cysteine

Here, we present a simple disulfide linked probe HTP for rapid detection of Cu2+ ions, which was prepared by a condensation reaction between 7-diethylamino-4-hydroxycoumarin aldehyde and 2-aminothiophenol. The disulfide linked probe HTP was characterized using 1H NMR, 13C NMR, and HRMS spectroscopic analysis and confirmed by single crystal X-ray diffraction analysis. The photophysical behavior of HTP in various solvents (non-polar to polar) was studied and HTP displayed aggregation induced emission (AIE) characteristics in CH3CN-water mixtures (0–99 %). Upon binding with Cu2+ ions, emission enhancement occurs along with color changes from weak green to intense yellow emission in CH3CN/Tris-HCl buffer (20 μM, 9:1, 10 mM Tris HCl Buffer, pH = 7.4). Detection limit for Cu2+ ions was found to be 0.97 nM which is lower than the recommended tolerance limit by the WHO and the association constant 0.42 × 108 M−1 was obtained using B-H plot. Furthermore, the stoichiometric ratio 1:1 was confirmed by job’s plot, 1H NMR, mass spectral analysis and DFT calculations were supported the formation of HTP-Cu2+ complex. The reversibility of HTP with Cu2+ ions was achieved by cysteine with detection limit and association constant value of 1.64 µM and 0.15 × 107 M−1 respectively. The reversible sensing nature of HTP with Cu2+/cysteine was further applied for constructing a molecular logic gate (INHIBIT) and practical applications such as paper strips, cotton swabs and real water analysis.

Superhydrophobic Paper Strips with Embedded Agarose-Anthocyanin Mini-Discs for Point-of-Need Quantitative pH Measurements.

Commercial pH paper is a quick and simple tool for measuring a solution's acidity/basicity, but it only provides qualitative or semi-quantitative results, and the synthetic indicator dyes within can be toxic or carcinogenic. Although pH meters enable more accurate and quantitative analysis, they are less convenient to operate and are tedious to calibrate. This presents a need for an alternative pH testing method for applications where it is not easy or possible to use a pH meter, yet quantitative results are desired. We report herein the fabrication of a pH test strip made from superhydrophobic paper and agarose-anthocyanin film discs. In the proposed method, test strips are dipped into samples and then imaged with a portable scanner (or a smartphone). The color of the film is extracted with ImageJ software (or a mobile app), using the RGB color system. By generating a calibration curve relating the film color to the sample pH using standard buffer solutions, we are able to quantify the pH of beverages and other liquids with an accuracy and precision comparable to that of a pH meter. The test strips offer the same convenience as conventional pH paper, with the added capabilities of quantitation and multiplexed testing, which presents a practical tool for point-of-need pH analysis.

New phenanthridine-based multi-functional chemosensor for selective detection of Th4+ and Hg2+ ions in both aqueous and solid state

A new phenanthridine-based multifunctional chemosensor (L), was synthesised via a green synthetic route and characterised using FT-IR, NMR and HRMS analysis. The sensing application of L towards metal ions in both solution and solid-state was studied using UV–vis and fluorescence spectroscopy, which exhibits dual-sensing behaviour for Th4+ and Hg2+ ions with good recyclability. In aqueous acetonitrile, L showed rapid response for the detection of environmental toxic metal ions and has a very low analytical detection limit of 125.5 pM and 1.94 nM for Th4+ and Hg2+ions respectively, which is remarkably lower than the World Health Organization standard. The cation binding property of the L with Th4+ and Hg2+ions was investigated by Job plot, 1H NMR titration, HR-MS and DFT calculation. The in-situ formed ensemble L-Hg2+ was further applied in the naked-eye detection of Cys (Cystine) and His (Histidine) over other common amino acids. The utility of L for real-time detection of Hg2+ and Th4+ ions was explored in various sources of environmental water samples, test paper strips, fingerprint imaging, fluorescent ink and smartphone-assisted sensing techniques, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in wastewater sources without resorting to expensive instruments.

Exploring Photophysical Properties of Organic Doped Polymeric Aggregates for Detecting Relevant Inorganic Pyrophosphate: A Pathway to Sustainable Development

Pyrophosphate (PPi) is an important environmentally and biologically relevant analyte and its easy and efficient detection is crucial for sustainable development. So, here we designed and synthesized organic-doped polymeric aggregates varying the signaling units (pyrene and anthracene) and examined their photophysical properties. By altering the signaling unit while keeping the polymeric backbone intact, we observed aggregate changes and studied their optical response with inorganic pyrophosphate (PPi). Among these probes, PYR-PEI exhibited a superior turn-off response(~6.1-fold) towards PPi in aqueous media whereas the other two probes ANH-PEI and PYR-PAH showed less response. The distinct response to PPi was primarily determined by electrostatic interaction and aggregate nature. The limit of detection (LOD) for PPi using the PYR-PEI probe was found to be 4.2 ppm, which is below the maximum allowable concentration of phosphate in surface water set by the World Health Organization (WHO) at 5mg/l. The quantification limit (LOQ) for PPi sensing was observed to be 14.27 ppm. Additionally, the PYR-PEI probe showed different fluorogenic responses (ratio-metric change) in the presence of anionic surfactant sodium dodecyl sulfate (SDS), and this resultant adduct was used for the PPi detection. The formation of premicellar aggregates between them drove the difference in the fluorogenic response with PYR-PEI and surfactant. Then the PYR-PEI composite was employed to detect PPi in spiked soil solution. Finally, chemically modified paper strips were prepared for the easy, fast, and on-location detection of PPi present in real-life samples.

Ethynylbenzaldehydes as novel reaction-based “turn-on” fluorescent probes for primary amine detection in solution, vapor, food, proteins, and live cells

Amine detection is of great importance as excess volatile amine exposure and increased concentration of biogenic amines in human body can cause adverse effects to human health. Thus, the development of easy-accessible and efficient fluorescent probes for amine detection is of great importance. In this study, we are the first to establish a cascade reaction sequence featuring imine formation followed by 6-endo-dig cyclization reaction for the development of sensitive and selective “turn-on” fluorescent probes toward primary amines by using the ortho-ethynylbenzaldehydes (EBAs) as the reaction site. The corresponding isoquinolinium products generated give a significant red-shifted absorbance change and highly intense “turn-on” fluorescence. Nine EBAs (EBA-1a-1e, EBA-2–5) were designed and synthesized to study the structure-photophysical property relationship (SPPR) for selective primary amine sensing. Our EBAs possessed a highly sensitive response toward primary amines in aqueous conditions within 30 min (LOD as low as 0.45 µM) with tunable absorption (338–430 nm) and emission (410–535 nm), large Stokes shift (up to 115 nm), and high fluorescence quantum yield (up to 0.86). EBA-loaded paper strips were prepared as a portable low cost tool for amine detection in solution, vapor, and food. Fluorogenic protein labelling and in-gel fluorescent imaging were efficiently achieved by using EBAs in which the fluorescence signal was obviously observed by naked eyes under 365 nm UV lamp. Moreover, the favorable membrane permeabilization, low to moderate cytotoxicity, and “turn-on” fluorescent response of EBA-1a-1e and EBA-4–5 allow wash-free live cell imaging. Interestingly, EBA-1a-1e and EBA-4 showed high selectivity to fluorescent imaging of mitochondria.

AuNP@Self-assembled 4H-Chromene-Enhanced colorimetric detection of ganciclovir using smartphone Technology: Portable solutions for healthcare

Any substance, radiation, or radionuclide in our environment that promotes carcinogenesis is a cancerogen. In the current work, we modified the 4H-chromene derivative by covering its surface with a shell of gold nanoparticles. Interestingly, ganciclovir (GCV) formed a bridge between the Nap-group of 4H-chromene and gold nanoparticles to display surface charge reduction properties in AuNP@Self-assembled 4H-Chromene. The surface charge of AuNPs is reduced as a result of the electron transfer mechanism brought on by the creation of the Nap-GCV-AuNP link, which leads to agglomeration. This led to the development of a dual-mode colorimetric sensor for GCV that incorporates solution form and portable sensor strip. The probe showed a linear range of 0–74 nM under ideal circumstances, with a detection limit of 4 nM in solution and 3 nM on paper strip detection. An evaluation of the practical utility in human serum using a portable visual read-out produced satisfactory findings, with a recovery percentage of 102.1 % and a standard deviation of ± 4 %. Surprisingly, this is the first work on the colorimetric detection of Ganciclovir that we are aware of.

A Dicyanoisophorone-based Fluorescent Turn-on Probe for Rapid Detecting Thiophenol in Aqueous Medium and Living Cell Imaging

A novel colorimetric and fluorescent thiophenol probe based on dicyanoisophorone has been successfully achieved, which has low-cost, easy operation, high selectivity, sensitivity and stability. The chemosensor shows a large Stokes shift and approximately 170 nm when excited at 510 nm. ISO-DiNO2 could be utilized as “Turn-on” and a naked-eyes chemosensor to detect PhSH, which is accompanied by a distinct color shift from red to dark purple with strong red fluorescence at 365 nm UV-light. Its limit of detection was determined to be 1.15 μM. More importantly, ISO-DiNO2 can react instantaneously (<10 s) with PhS−. In addition, ISO-DiNO2 has been utilized in test paper strips, water sample together with imaging of PhS− in living Raw264.7 cells, demonstrating that ISO-DiNO2 has excellent and promising applications.

Development of biochromic paper strips from cellulose nanocrystals and anthocyanin extract from pomegranate (Punica granatum L.) for colorimetric determination of urea

AbstractAn anthocyanin (ACN) spectroscopic probe was extracted and immobilized into a matrix of cellulose nanocrystals (CNC)/urease enzyme to create a colorimetric nanocomposite film sensor. The ACN@CNC composite is a disposable molecular biosensor that uses urease as a catalyst, ACN as a molecular probe, and CNC as a probe carrier with a high surface area. The ACN spectroscopic probe was isolated from the pomegranate peel (Punica granatum L.). A mordant was applied to fix ACN onto CNC by forming nanoparticles (6–14 nm) of mordant/ACN (M/ACN) complexation. CNC showed diameters in the range of 11–21 nm, and crystal lengths of 55–130 nm. Under acid/base conditions, the ACN probe solution in distilled water exhibited a reversible color change, as shown by the UV–Vis absorption spectra. In order to create a biocomposite film, CNC were reinforced with a sodium alginate biopolymer. Upon exposure to urea in an aqueous solution, the ACN@CNC film biosensor changes color from purple (598 nm) to white (432 nm). The detection limit of urea was determined at 25–450 ppm. Various methods were utilized to investigate the morphological properties of CNC and ACN@CNC films.

Response to the comments on “Cellular aggregation dictates universal spreading behaviour of a whole-blood drop on a paper strip”

In 2023, we published a research article in the Journal of Colloidal and Interface Science, based on our experimental findings and substantiating scaling arguments leading to a simple theoretical insight on the effect of red blood cell (RBC) aggregation on the wicking behaviour of a finite volume of blood as it navigates through the porous passages of a paper matrix (Laha et al., 2023). Of late, we received comments from Li (2024), which offered certain suggestions regarding the possible improvement of the capillary bundle model as considered in our article for analyzing the transport of blood through the paper pores. Herein, we provide a detailed discussion on each of the points raised by Li (2024) and rationalize our views in further details in addition to the contents already provided in our concerned article.