Paper-Based Multiplexed Colorimetric Device for the Simultaneous Detection of Salivary Biomarkers

In this study, we describe a monolithic and fully integrated paper-based device for the simultaneous detection of three prognostic biomarkers in saliva. The pattern of the proposed multiplexed device is designed with a central sample deposition zone and three identical arms, each containing a pre-treatment and test zone. Its one-step fabrication is realized by CO2 laser cutting, providing remarkable parallelization and rapidity (ca. 5 s/device). The colorimetric detection is based on the sensitive and selective target-induced reshaping of plasmonic multibranched gold nanoparticles, which exhibit a clear spectral shift (and blue-to-pink color change) in case of non-physiological concentrations of the three salivary biomarkers. A rapid and multiplexed naked-eye or smartphone-based readout of the colorimetric response is achieved within 10 min. A prototype kit for POCT testing is also reported, providing robustness and easy handling of the device.

Spectral Analysis of Azo Derivatives for their Colorimetric Response to some Special Metal Ions

The present study describes an efficient chromogenic probing ability possessed by an azo linkage that could sense Ni, Fe, and Co in the semi-aqueous medium. The chromogenic sensing properties of the four azo dyes were studied towards Fe(III), Co(II), and Ni(II) ions, the IR and UV-VIS spectral data revealed that the nitrogen and oxygen atoms of –N=N-, C=O and –OH groups participated in bonding with the metal ions. Also, an obvious change in the color of the azo dyes A and B solution from yellow to dark brown in the case of Fe+2 metal ions and Co+2 and Ni+2 colorless solutions appeared yellowish, while the addition of other metal ions did not cause any color change. These results imply that the two azo dyes are viable, portable chromogenic chemosensors for the detection of Fe (III), Co (II), and Ni (II) ions in various biological and environmental fields.

Design, Synthesis, and Evaluation of New Colorimetric Chemosensors Containing Quinazolinones Moiety for some Cations Detection in an Aqueous Medium and Biological Sample

The current project deals with designing and synthesizing of colorimetric chemosensors to detect the cations in the aqueous medium and biological sample. To achieve this goal a new series of quinazolinone derivatives were synthesized via reaction of the novel 6-nitro-2-propyl-4H-benzo[d][1,3]oxazin-4-one (3) with selected nitrogen nucleophiles, namely, formamide, hydrazine hydrate, hydroxylamine hydrochloride, O-phenylendiamine, O-aminophenol and O-aminothiophenol, urea and/or thiourea. Structures of the new compounds have been investigated depending on their spectral data (IR, 1H NMR, 13C NMR and MS) and elemental analyses. Some of the newly synthesized products exhibited a significant response as chemosensors for some cations detection. The synthesized chemosensors 11a and 11b showed high-selectivity and specificity towards cooper (CuII) and mercury (HgII) cations detection through exhibiting colormetric responses. Chemosensors 7 and 10b showed high selectivity toward cadmium (CdII) cation, whilst other examined compounds (9b, c, 10a, 12, 13, and 14) did not exhibit colorimetric response in all cation's samples. Resumen. En el presente proyecto se diseñan y sintetizan quimiosensores colorimétricos para detectar los cationes en el medio acuoso y en la muestra biológica. Para lograr este objetivo se sintetizó una nueva serie de derivados de quinazolinona mediante la reacción de la 6-nitro-2-propil-4H-benzo[d][1,3]oxazin-4-ona (3) con nucleófilos nitrogenados seleccionados, a saber, formamida, hidrato de hidracina, clorhidrato de hidroxilamina, O-fenilendiamina, O-aminofenol y O-aminotiofenol, urea y/o tiourea. Las estructuras de los nuevos compuestos se han comprobado en función de sus datos espectrales (IR, 1H NMR, 13C NMR y MS) y de los análisis elementales. Algunos de los nuevos productos sintetizados mostraron una respuesta significativa como quimiosensores para la detección de algunos cationes. Los quimiosensores sintetizados 11a y 11b mostraron una alta selectividad y especificidad hacia la detección de los cationes cobre (Cu II) y mercurio (Hg II) al mostrar respuestas colormétricas. Los quimiosensores 7 y 10b mostraron una alta selectividad hacia el catión cadmio (Cd II), mientras que otros compuestos examinados (9b, c, 10a, 12, 13 y 14) no mostraron respuesta colorimétrica con los cationes investigados.

Fabrication and Characterization of Multifunctional Curcumin Loaded Poly(methyl methacrylate) Fluorescent Nanofiber Membrane

This work aims at the development of curcumin loaded poly(methyl methacrylate) (CC-PMMA) fluorescent nanofiber membrane and the evaluation of its multifunctional characteristics. The nanofibers were created by electrospinning method. The conditions of the spinning were optimized to obtain beadless and smooth nanofibers. The physico-chemical characteristics of the nanofibers were studied by various techniques including, polarizing light microscope, FT-IR, inverted epi fluorescence microscope and HR-TEM. The HR-TEM results confirm the formation of nanofibers with the diameter in the range of 90–200 nm. The average width of PMMA and CC-PMMA nanofibers are ˜90±0.02 nm and ˜110±0.01 nm, respectively. The CC-PMMA nanofibers exhibited the fluorescence shift with an emission around 520 nm. The multifunctional characteristic of CC-PMMA nanofiber was evaluated for sensor and antibacterial applications. The CC-PMMA nanofiber membrane showed a visible color variation from yellow to red on interaction with ammonia. This colorimetric response to ammonia is highly selective and there was no any interference from other related organic vapors. In addition, it showed good antibacterial activities for Gram-positive and Gram-negative bacteria (zone of inhibition of 27 mm for S. aureus). This is the initial research report in the combination of curcumin and PMMA nanofiber. The multifunctionality of the CC-PMMA nanofibers could be exploited for various applications including sensors, antibacterial coatings, air filtration and drug delivery.

Solvent-Controlled Self-Assembled Oligopyrrolic Receptor

We report a fully organic pyridine-tetrapyrrolic U-shaped acyclic receptor 10, which prefers a supramolecular pseudo-macrocyclic dimeric structure (10)2 in a less polar, non-coordinating solvent (e.g., CHCl3). Conversely, when it is crystalized from a polar, coordinating solvent (e.g., N,N-dimethylformamide, DMF), it exhibited an infinite supramolecular one-dimensional (1D) “zig-zag” polymeric chain, as inferred from the single-crystal X-ray structures. This supramolecular system acts as a potential receptor for strong acids, e.g., p-toluenesulfonic acid (PTSA), methane sulfonic acid (MSA), H2SO4, HNO3, and HCl, with a prominent colorimetric response from pale yellow to deep red. The receptor can easily be recovered from the organic solution of the host–guest complex by simple aqueous washing. It was observed that relatively stronger acids with pKa < −1.92 in water were able to interact with the receptor, as inferred from 1H NMR titration in tetrahydrofuran-d8 (THF-d8) and ultraviolet–visible (UV–vis) spectroscopic titrations in anhydrous THF at 298 K. Therefore, this new dynamic supramolecular receptor system may have potentiality in materials science research.

Polydiacetylene Vesicles Acting as Colorimetric Sensor for the Detection of Plantaricin LD1 Purified From Lactobacillus Plantarum LD1

The interaction of antimicrobial peptides with membrane lipids plays a major role in numerous physiological processes. Bacteriocins are antimicrobial peptides known to kill target cells by pore formation and membrane disruption. In this study, polydiacetylene (PDA) vesicles were applied as artificial membrane for detection of plantaricin LD1 purified from Lactobacillus plantarum LD1. Plantaricin LD1 (200 µg/ml) was able to change the color of PDA vesicles from blue to red with colorimetric response CR % 30.26 ± 0.59. Nisin (200 µg/ml), used as control, also changed the color of the vesicles with CR % 50.56 ± 0.98 validating the membrane-acting nature of these bacteriocins. The PDA vesicles treated with nisin and plantaricin LD1 showed increased infrared absorbance at 1411.46 cm-1 and 1000-1150 cm-1 indicated the interaction of bacteriocins with phospholipids and fatty acids, respectively. Further, microscopic examination also suggested the disruption of bacteriocin-treated vesicles indicating the interaction of bacteriocins. These findings suggest that the PDA vesicles may be used as bio-mimetic sensor for the detection of bacteriocins produced by several probiotics in food and therapeutic applications.