Rhodamine derivative-functionalized mesoporous silica-Al3+ hybrid material for fluorescence "turn-on" detection of tetracycline antibiotics in aqueous media

The organic-inorganic hybrid material was prepared by embedding 2-amino-3',6'-bis(diethylamino)spiro[isoindoline-1,9'-xanthen]-3-one (RBH) onto mesoporous SBA-15 silica and coordinating it with Al3+ (RBH-SBA-15-Al3+). RBH-SBA-15-Al3+ was used for the selective and sensitive detection of tetracycline antibiotics (TAs) in aqueous media based on the binding site-signaling unit mechanism, in which Al3+ acted as the binding site and the fluorescence intensity at 586 nm as the response signal. The addition of TAs to RBH-SBA-15-Al3+ suspensions resulted in the formation of RBH-SBA-15-Al3+-TAs conjugates, which realized the electron transfer process and turned-on fluorescence signal at 586 nm. The detection limits for tetracycline (TC), oxytetracycline, and chlortetracycline were 0.06, 0.06, and 0.03 µM, respectively. Meanwhile, the detection of TC was feasible in real samples, such as tap water and honey. In addition, RBH-SBA-15 can operate as a TRANSFER logic gate by using Al3+ and TAs as input signals and the fluorescence intensity at 586 nm as output signal. This study proposes an efficient strategy for the selective detection of target analytes by introducing interaction sites (e.g. Al3+) with target analytes in the system.

1,2,3-Triazoles: Controlled Switches in Logic Gate Applications

A 1,2,3-triazole-based chemosensor is used for selective switching in logic gate operations through colorimetric and fluorometric response mechanisms. The molecular probe synthesized via "click chemistry" resulted in a non-fluorescent 1,4-diaryl-1,2,3-triazole with a phenol moiety (PTP). However, upon sensing fluoride, it TURNS ON the molecule's fluorescence. The TURN-OFF order occurs through fluorescence quenching of the sensor when metal ions, e.g., Cu2+, and Zn2+, are added to the PTP-fluoride ensemble. A detailed characterization using Nuclear Magnetic Resonance (NMR) spectroscopy in a sequential titration study substantiated the photophysical characteristics of PTP through UV-Vis absorption and fluorescence profiles. A combination of fluorescence OFF-ON-OFF sequences provides evidence of 1,2,3-triazoles being controlled switches applicable to multimodal logic operations. The "INH" gate was constructed based on the fluorescence output of PTP when the inputs are F- and Zn2+. The "IMP" and "OR" gates were created on the colorimetric output responses using the probe's absorption with multiple inputs (F- and Zn2+ or Cu2+). The PTP sensor is the best example of the "Write-Read-Erase-Read" mimic.

Ratiometric colorimetric detection of fluoride ions using a schiff base sensor: enhancing selectivity and sensitivity for naked-eye analysis

A Schiff base receptor with an active -NH group was designed and synthesized for the selective and sensitive colorimetric detection of inorganic fluoride (F^-) ions in an aqueous medium. The sensitivity of the receptor for F^- ions was enhanced by the influence of two electron-withdrawing -NO₂ groups at ortho and para positions which result in a vivid color change. The receptor underwent a remarkable color change from light yellow to violet, enabling naked-eye detection of F^- ions without the need for spectroscopic equipment. To ensure the structural integrity of the synthesized receptors, prominent spectroscopic techniques such as ¹H NMR, FTIR, and GCMS analysis were used for characterization. With a limit of detection (LoD) of 0.0996 ppm, a 1 : 2 stoichiometric binding ratio was observed for receptor and F^- ions. The binding mechanism confirmed the deprotonation of the -NH group followed by the formation of -HF₂, resulting in an intramolecular charge transfer (ICT) transition, which correlates with UV-vis and ¹H NMR titration results. In addition, the proposed binding mechanism of F^- ion interaction with the receptor was theoretically validated using DFT and TDDFT calculations. Furthermore, as a real-life implementation of the receptor, quantification of the F^- ions present in a commercially available mouthwash was demonstrated. To assess the sensitivity performance, a paper-based dip sensor and a solid substrate sensor by functionalizing the receptor on diatomaceous earth were demonstrated. Finally, sensors were built into smartphones that could recognize the red, green, and blue percentages (RGB%) where each parameter defines the intensity of the color, which could also be used as a supplement to the colorimetric investigations.

Dual-AND Logic Gate-Based Strip Assay for Amplified Detection of Four miRNAs and Diagnosis of Lung Cancer

The detection of circulating tumor microRNAs (miRNAs) holds great promise for the noninvasive and early-stage diagnosis of cancer. However, the low abundance of lung cancer-related miRNAs and the false-positive results of single miRNA detection limited the development of strip-based point-of-care testing methods in clinic. We developed a duplex-specific nuclease (DSN)-mediated and dual-AND logic gate-based triple-line lateral flow strip detection system for the rapid and simultaneous detection of four miRNAs of lung cancer in a single strip test. This system combines DSN-mediated signal amplification with AND logic gate-based simple signal output. Meanwhile, the limit of detection of this platform was calculated to be 26.51 fM. Furthermore, this assay was used to detect lung cancer-related miRNAs from serum in a homogeneous and separation-free format, which could discriminate lung cancer patients from healthy individuals with an accuracy of 100%. Our approach provides a simple and easy-to-handle method for the diagnosis of lung cancer in clinic.

Recent Advances in Microfluidic Platform for Physical and Immunological Detection and Capture of Circulating Tumor Cells

CTCs (circulating tumor cells) are well-known for their use in clinical trials for tumor diagnosis. Capturing and isolating these CTCs from whole blood samples has enormous benefits in cancer diagnosis and treatment. In general, various approaches are being used to separate malignant cells, including immunomagnets, macroscale filters, centrifuges, dielectrophoresis, and immunological approaches. These procedures, on the other hand, are time-consuming and necessitate multiple high-level operational protocols. In addition, considering their low efficiency and throughput, the processes of capturing and isolating CTCs face tremendous challenges. Meanwhile, recent advances in microfluidic devices promise unprecedented advantages for capturing and isolating CTCs with greater efficiency, sensitivity, selectivity and accuracy. In this regard, this review article focuses primarily on the various fabrication methodologies involved in microfluidic devices and techniques specifically used to capture and isolate CTCs using various physical and biological methods as well as their conceptual ideas, advantages and disadvantages.

An isocamphanyl-based fluorescent "turn-on" probe for highly sensitive and selective detection of Ga3+ and application in vivo and in vitro

A novel fluorescent probe 2-(4-(diethylamino)-2-hydroxybenzylidene)-N-(2,3,3-trimethylbicyclo[2.2.1]heptan-2-yl)hydrazinecarbothioamide (HT) was prepared in this study by a condensation reaction. HT has been confirmed to possess high specificity toward Ga³⁺ over other metal ions (including Al³⁺ and In³⁺) via a distinct fluorescence light-up response. Moreover, HT exhibited good detection performances for Ga³⁺ including high selectivity, excellent anti-interference ability, a wide working pH range, and good reversibility. The association constant and limit of detection (LOD) were calculated to be 5.34 × 10³ M^-1 and 1.18 × 10^-6 M, respectively. The detection mechanism of HT toward Ga³⁺ was proposed and confirmed by ¹H NMR analysis, HRMS analysis, and DFT calculations. A simple test strip-based portable detecting device and a molecular INHIBIT logic circuit were established for improving its practical applicability. Furthermore, the desirable sensing performance of HT for Ga³⁺ was successfully reconfirmed in MCF-7 cells and zebrafish.

Infochemistry and the Future of Chemical Information Processing

Nowadays, information processing is based on semiconductor (e.g., silicon) devices. Unfortunately, the performance of such devices has natural limitations owing to the physics of semiconductors. Therefore, the problem of finding new strategies for storing and processing an ever-increasing amount of diverse data is very urgent. To solve this problem, scientists have found inspiration in nature, because living organisms have developed uniquely productive and efficient mechanisms for processing and storing information. We address several biological aspects of information and artificial models mimicking corresponding bioprocesses. For instance, we review the formation of synchronization patterns and the emergence of order out of chaos in model chemical systems. We also consider molecular logic and ion fluxes as information carriers. Finally, we consider recent progress in infochemistry, a new direction at the interface of chemistry, biology, and computer science, considering unconventional methods of information processing.

TICT fluorescent probe for Al3+: Sequential detection of PPi, ATP and ADP in semi-aqueous medium and real-life applications

A ditopic Schiff base ligand, H₂L has been synthesized and characterized by all spectroscopic techniques. It is highly selective and specific towards Al³⁺ in semi aqueous medium (DMF/H₂O mixture) by exhibiting a drastic increase in the fluorescence intensity. The emission studies, spectroscopic data, life time and quantum yield results have been used to understand its binding mode, explore its specificity and establish its efficacy. The intensity difference is remarkable in physiological pH range. Due to its reversible behavior this ditopic fluorescent chemosensor can be used multiple times to make it cost effective. Detection limit for this chemosensor was found to be 0.65 μM. Experiments with TLC plates show that it can be used as a practical and portable sensor for studying environmental samples in real life. The L-Al³⁺ complex generated in the solution acts as a sensor to sequentially detect pyrophosphate groups present in inorganic pyrophosphates, ATP and ADP among other anions by turning off the fluorescence. Inhibit logic gate and its corresponding truth table has been developed to aid in further exploiting its multidimensional applications.

Nopinone-based AIE-active dual-functional fluorescent chemosensor for Hg2+ and Cu2+ and its environmental and biological applications

A nopinone-based dual-functional fluorescent probe for Hg²⁺ and Cu²⁺ and its applications in environmental analysis and bioimaging.

A potential naphthyl-thiazole-based organic dye and a ditopic chromogenic probe for CN− and Fe3+ with molecular logic functions

Dye sensitizers are entities designed primarily to serve the function of harvesting light photons in the functional wavelength, which is centered on charge transfer mechanisms.

Development of three ways molecular logic gate based on water soluble phenazine fluorescent 'selective ion' sensor

New hydrophilic fluorescent selective ion sensor based on phenazine and phthalazine moieties, 1,1'-(phenazine-2,3-diyl)-bis(3-(1,4-dihydroxyphthalazin-6-yl)urea) (1), has been designed, synthesized and characterized. Interestingly, sensor 1 exhibits prominent "turn-on" and "turn-off" fluorogenic signaling at 580 nm towards Fe²⁺ & AcO^- and Sr²⁺ & Cu²⁺, respectively. The fluorescence titration experiments shed light on the nature of the interaction between 1 and guest molecules (Fe²⁺, Sr²⁺, Cu²⁺ and AcO^-), which divulge that 1 is flexible enough to orient itself according to the size of the guest molecule. Water mediated excited-state intramolecular proton transfer (ESIPT) and photo-induced electron transfer (PET) mechanisms are responsible for the dual behavior of 1, which binds with guest molecules in 1:1 stoichiometry. Based on the significant duplex fluorescence response of 1, a molecular logic gate keypad lock with sixteen "on" passwords for a storage system has been developed.

A water-soluble BODIPY based 'OFF/ON' fluorescent probe for the detection of Cd2+ ions with high selectivity and sensitivity

A water-soluble dilithium salt BODIPY derivative (LiBDP) with appended dicarboxylate pseudo-crown ether [NO4] coordinating sites has been designed, synthesized and characterized successfully for the selective and sensitive recognition of Cd2+ in aqueous media. The chemosensor exhibits a remarkable increase in fluorescence intensity as well as a distinct color change upon the addition of Cd2+ over other environmentally and biologically relevant metal ions in H2O. The fluorometric response of LiBDP is attributed to the metal chelation-enhanced fluorescence (MCHEF) effect which has been confirmed by a strong association constant of 2.57 ± 1.06 × 105 M-1 and Job's plot, indicating 1 : 1 binding stoichiometry between LiBDP and Cd2+. Frontier molecular orbital analysis (obtained from DFT studies) also illustrates the turn-on fluorescence of the probe by blocking photoinduced electron transfer (PET) after coordination to Cd2+. The probe can detect Cd2+ in a competitive environment up to a submicromolar level in a biologically significant pH range. The sensor is proved to be reversible and reusable by the alternative addition of Cd2+ followed by S2-. The OFF/ON/OFF sensing behavior is utilized to construct an INHIBIT molecular logic gate based on the two inputs of Cd2+ and S2- and a fluorescence intensity at 512 nm as an output. The test paper experiment demonstrates the practical utility of LiBDP to monitor Cd2+ in an aqueous sample. Finally, the sensing probe was utilized to monitor Cd2+ in living cells.

Nanoscale fluorescent metal-organic framework composites as a logic platform for potential diagnosis of asthma

Asthma is a common chronic disorder, and the decreased hydrogen sulfide (H₂S) production in the lung has been considered as an early detection biomarker for asthma. However, the detection of H₂S in biological systems remains a challenge; because it requires the designed sensors to have the following features: nanoscale size, good biocompatibility, real-time detection, high selectivity/sensitivity, and good water stability. Here, we propose the potential of using nanoscale fluorescent metal-organic framework (MOF) composites Eu³⁺/Ag⁺@UiO-66-(COOH)₂ (hereafter denoted as EAUC) as a logic platform for tentative diagnosis of asthma by detecting the biomarker H₂S. This INHIBIT logic gate based on Eu³⁺@UiO-66-(COOH)₂ (EUC) can be produced by choosing Ag⁺ and H₂S as inputs and by monitoring the fluorescent signal (I₆₁₅) as an output. Our fluorescent studies indicate that the EAUC exhibits excellent selectivity, extreme sensitivity (limit of detection: 23.53 μM), and real-time in situ detection of H₂S. Further, MTT analysis in PC12 cells shows that the EAUC possesses low cytotoxicity and favourable biocompatibility that are suitable for the detection of biomarker H₂S in vivo, as demonstrated by the successful detection of spiked H₂S in the diluted serum samples. This work represents the possibility of using MOF-based logic platform for tentative diagnosis of asthma in clinical medicine.

A reversible fluoride chemosensor for the development of multi-input molecular logic gates

A reversible chemosensor for the development of a multi-input molecular logic gate was shown.

A novel biphenyl-derived salicylhydrazone Schiff base fluorescent probes for identification of Cu2+ and application in living cells

A novel biphenyl-derived salicylhydrazone Schiff base (BSS) fluorescent probes for highly sensitive and selective identification of Cu²⁺ has been synthesized. In addition, the recognition has been proved experimentally. The results indicated that the complex forms a 1:1 complex with Cu²⁺ shows fluorescent quenching. Furthermore, the detection limit of 1.54×10^-8M. More interesting, the probe BSS not only have a good biocompatibility in living cells, but also the sense behavior of Cu²⁺ in the cell nucleus.

Incorporating Electron-Deficient Bipyridinium Chromorphores to Make Multiresponsive Metal-organic Frameworks

Metal-organic frameworks (MOFs) are versatile platforms to design switchable and sensory materials responsive to external stimulus. Copuling the electron-deficient bipyridinium chromorphore with the pore structures of MOFs is a nice strategy to design multiresponsive MOFs. Here we present a proof-of-concept study. Postsynthetic N,N'-cycloalkylation of UiO-67-bpy (bpy = 2,2'-bipyridyl) leads to a novel ionic MOF (UiO-67-DQ) functionalized by the electron-deficient diquat (DQ) chromophore. The combination of porosity, cationic character and electron deficiency imparts UiO-67-DQ with versatile responsive properties. It readily undergoes anion exchange, with selective ionochromism associated with charge-transfer (CT) complexation; it is electrochemically active and shows anion-dependent photochromism associated with radical formation through electron transfer (ET); the iono- and photochromism cause efficient luminescence quenching because of energy transfer (EnT) to CT complexes or radicals. The properties of UiO-67-MQ (MQ = N,N'-dimethyl-2,2'-bipyridylium) are also presented for comparison. The CT and ET effects and consequently the EnT efficiency in UiO-67-MQ are weaker than those in UiO-67-DQ because the electron-deficient character is weakened by the severe interannular twist in MQ²⁺. On the basis of the rich responsive properties, the MOFs are used as sensory and switching materials for facile discrimination of a range of anions, for quantitative detection of I^-, and for mimicking of logic operations ranging from simple logic gates to complex integrated logic circuits.

Highly selective and sensitive macrocycle-based dinuclear foldamer for fluorometric and colorimetric sensing of citrate in water

The selective detection of citrate anions is essential for various biological functions in living systems. A quantitative assessment of citrate is required for the diagnosis of various diseases in the human body; however, it is extremely challenging to develop efficient fluorescence and color-detecting molecular probes for sensing citrate in water. Herein, we report a macrocycle-based dinuclear foldamer (1) assembled with eosin Y (EY) that has been studied for anion binding by fluorescence and colorimetric techniques in water at neutral pH. Results from the fluorescence titrations reveal that the 1·EY ensemble strongly binds citrate anions, showing remarkable selectivity over a wide range of inorganic and carboxylate anions. The addition of citrate anions to the 1·EY adduct led to a large fluorescence enhancement, displaying a detectable color change under both visible and UV light in water up to 2 μmol. The biocompatibility of 1·EY as an intracellular carrier in a biological system was evaluated on primary human foreskin fibroblast (HF) cells, showing an excellent cell viability. The strong binding properties of the ensemble allow it to be used as a highly sensitive, detective probe for biologically relevant citrate anions in various applications.

Anion-induced isomerization of fluorescent semi(thio)carbazones

An anion-controlled flapping motion has been observed in a series of novel semi(thio)carbazone molecules.

A self-calibrating bimetallic lanthanide metal–organic luminescent sensor integrated with logic gate operation for detecting N-methylformamide

A luminescent [Eu_0.1Tb_1.9(FDA)₃(DMF)₂]·2DMF sensor has been constructed integrated with a logic gate capable of detecting NMF by intelligent discrimination.

A Double-Stimuli-Responsive Fluorescent Center for Monitoring of Food Spoilage based on Dye Covalently Modified EuMOFs: From Sensory Hydrogels to Logic Devices

Unsafe food is a huge threat to human health and the economy, and detecting food spoilage early is an ongoing and imperative need. Herein, a simple and effective strategy combining a fluorescence sensor and one-to-two logic operation is designed for monitoring biogenic amines, indicators of food spoilage. Sensors (methyl red@lanthanide metal-organic frameworks (MR@EuMOFs)) are created by covalently modifying MR into NH₂ -rich EuMOFs, which have a high quantum yield (48%). A double-stimuli-responsive fluorescence center is produced via energy transfer from the ligands to Eu³⁺ and MR. Portable sensory hydrogels are obtained by dispersing and solidifying MR@EuMOFs in water-phase sodium salt of carboxy methyl cellulose (CMC-Na). The hydrogels exhibit a color transition upon "smelling" histamine (HI) vapor. This transition and shift in the MR-based emission peak are closely related to the HI concentration. Using the HI concentration as the input signal and the two fluorescence emissions as output signals, an advanced analytical device based on a one-to-two logic gate is constructed. The four output combinations, NOT (0, 1), YES (1, 0), PASS 1 (1, 1), and PASS 0 (0, 0), allow the direct analysis of HI levels, which can be used for real-time food-freshness evaluation. The novel strategy suggested here may be a new application for a molecular logic system in the sensing field.

Performing Logical Operations with Stimuli-Responsive Building Blocks

Chemical logic gates can be fabricated by synthesizing molecules that have the ability to detect external stimuli (e.g., temperature or pH) and provide logical outputs. It is, however, challenging to fabricate a system that consists of many logic gates using this method: complex molecules can be difficult to synthesize and these logic gates typically cannot be integrated together. Here, we fabricated different types of logic gates by assembling a combination of different types of stimuli-responsive hydrogels that change their size under the influence of one type of stimulus. Importantly, the preparation of these stimuli-responsive hydrogels is widely reported and technically simple. Through designing the geometry of the systems, we fabricated the YES, NOT, OR, AND, NOR, and NAND gates. Although the hydrogels respond to different types of stimuli, their outputs are the same: a change in size of the hydrogel. Hence, we show that the logic gates can be integrated easily (e.g., by connecting an AND gate to an OR gate). In addition, we fabricated a standalone system with the size of a normal drug tablet (i.e., a "smart tablet") that can analyze (or diagnose) different stimuli and control the release of a chemical (or drug) via the logic gates.

A new pyrazoline-based probe of quenched fluorescent reversible recognition for Cu2+ and its application in cells

A new pyrazoline-based probe D was designed and synthesized, which can be used as a highly sensitive, selective and reversible recognizing fluorescent to detect Cu²⁺. The recognition properties of this compound was investigated by UV-vis absorption and fluorescence spectrophotometry. The results showed that the probe D forms a 1:1 complex with Cu²⁺ and displayed a linear fluorescence response to Cu²⁺ with a detection limit of 1.94×10^-7M. In addition, the probe have a good biocompatibility in living cells.

A fluorescent combinatorial logic gate with Na+, H+-enabled OR and H+-driven low-medium-high ternary logic functions

A fluorescent combinatorial Na⁺, H⁺ logic gate is demonstrated that could represent a class of probes for investigating antiporters in biological systems.

Proof of principle of a three-input AND–INHIBIT–OR combinatorial logic gate array

A designed molecule provides a fluorescent signal according to a combinatorial logic array comprised of three-input AND, three-input INHIBIT and two-input OR logic gates.

Selenoureas for anion binding as molecular logic gates

The first example of a molecular logic gate based on selenourea/anion host–guest interaction that performs a ternary logic operation using an ¹H-NMR easy to read response output is described here.

Anion-Controlled Positional Switching of a Phenyl Group about the Dinuclear Core of a AuSb Complex

As part of our continuing interest in redox-active, anion-responsive main-group transition-metal platforms, we have investigated the effect of chloride by fluoride anion substitution on the core structure of a dinuclear AuSb platform. Starting from [(o-(iPr2P)C6H4)2Cl2SbPh]AuCl (2) in which the antimony-bound phenyl group is positioned trans to the gold atom, we found that the introduction of fluoride anions, as in [(o-(iPr2P)C6H4)2F2SbPh]AuCl (3) and [(o-(iPr2P)C6H4)2ClFSbPh]AuCl (4), produces structures in which the phenyl group switches to a perpendicular direction with respect to the gold atom. Replacement of the gold-bound chloride anion in 3 by a fluoride anion can be achieved by successive treatment with TlPF6 and [nBu4N][Ph3SiF2]. These reactions, which proceed via the intermediate zwitterionc gold antimonate complex [o-(iPr2P)C6H4)2F3SbPh]Au (6), trigger migration of the phenyl group to gold and afford [(o-(iPr2P)C6H4)2F3Sb]AuPh (7). Because the phenyl group in 7 is orthogonal to that in 3 and opposite to that in 2, the title AuSb platform can be regarded as a molecular analogue of a mechanical three-way switch in which the switching element is a phenyl group. Finally, while all complexes involved retain a Au → Sb interaction, this interaction is no longer present in the zwitterionic derivative 6 because of the neutralization of the Lewis acidity of the antimony center.

Multiscale Approach to the Study of the Electronic Properties of Two Thiophene Curcuminoid Molecules

We studied the electronic and conductance properties of two thiophene-curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), in which the only structural difference is the position of the sulfur atoms in the thiophene terminal groups. We used electrochemical techniques as well as UV/Vis absorption studies to obtain the values of the HOMO-LUMO band gap energies, showing that molecule 1 has lower values than 2. Theoretical calculations show the same trend. Self-assembled monolayers (SAMs) of these molecules were studied by using electrochemistry, showing that the interaction with gold reduces drastically the HOMO-LUMO gap in both molecules to almost the same value. Single-molecule conductance measurements show that molecule 2 has two different conductance values, whereas molecule 1 exhibits only one. Based on theoretical calculations, we conclude that the lowest conductance value, similar in both molecules, corresponds to a van der Waals interaction between the thiophene ring and the electrodes. The one order of magnitude higher conductance value for molecule 2 corresponds to a coordinate (dative covalent) interaction between the sulfur atoms and the gold electrodes.