A RET-supported logic gate combinatorial library to enable modeling and implementation of intelligent logic functions

Chemically Fueled Logic AND Gate with Double Encoding in the Time Domain

To increase information density and security in communication, Nature at times encodes signals in the time domain, for instance, Ca2+ ion signals. Double encoding in the time domain operates beyond this level of security because the data are encoded in two time-dependent output signals showing distinct periods, frequencies, and full duration half-maxima. To illustrate such a protocol, a three-component ensemble consisting of a double ion-selective luminophore with two distinct receptor sites, hexacyclen, and diaza-18-crown-6 ether is demonstrated to act as a logic AND gate with Ag+ and Ca2+ ions as inputs. The gate shows an unprecedented 2-fold time-encoded fluorescence output at 590 and 488 nm based on metal ion pulses with distinct periods when trichloroacetic acid is applied as chemical fuel.

Nanoclusters with specific DNA overhangs: modifying configurability, engineering contrary logic pairs and the parity generator/checker for error detection

The most promising alternative for next-generation molecular computers is biocomputing, which uses DNAs as its primary building blocks to perform a Boolean operation. DNA nanoclusters (NCs) have emerged as promising candidates for biosensing applications due to their unique self-assembly properties and programmability. It has been demonstrated that adding DNA overhangs to DNA NCs improves their adaptability in identifying specific biomolecular interactions. A recent proposal in DNA computing is the concept of "contrary logic pairs (CLPs)" executed by employing a DNA hybrid architecture as a universal platform. We have designed thymine overhang-modified DNA-templated NCs (T-Au/Ag NCs). These NCs serve as a chemosensing ensemble platform, where the presence of HgII ions mediates the formation of M-Au/Ag NCs. The resulting NCs exhibit the capability to drive elementary CLPs (YES, NOT, OR, NOR, INH and IMP) as well as complex logic operations (XOR and XNOR). Additionally, they can be utilized for advanced non-arithmetic DNA logic devices like a parity generator (pG) and a parity checker (pC) for "error detection". Bit errors are an unavoidable and common occurrence during any computing. A cascade of XOR operations was used to evaluate these errors by introducing the pG and pC at the transmitting (TX) and receiving (RX) ends in binary transmission, respectively, which has devastating implications for reliable logic circuits, especially in advanced logic computation. Moreover, an even/odd natural number from 0 to 9 distinguishable pC was designed based on a dual-source responsive computing platform. This work offers inspiring avenues for a cost-effective strategy to construct highly-intelligent DNA computing devices by enhancing the multi-input responsive single DNA platform concept.

Cell-Membrane-Anchored DNA Logic-Gated Nanoassemblies for In Situ Extracellular Bioimaging

Extracellular K⁺ and adenosine triphosphate (ATP) levels are significantly elevated in the tumor microenvironment (TME) and can be used as biomarkers for early cancer detection and tumor localization. Most reported TME sensors only respond to single abnormal factors, resulting in a lack of accuracy and specificity for the detection of complex environments. Thus, precisely locating the TME remains challenging. In this work, we aimed to develop an intelligent DNA nanoassembly controlled by a "YES-AND" logic circuit using a bimolecular G-quadruplex (G4) and ATP aptamer as logical control units. As a proof of concept, in the presence of K⁺ (input 1) and ATP (input 2), the YES-AND Boolean operator returned a true value and the output was the fluorescence resonance energy transfer (FRET) signal, indicating high sensitivity and selectivity. After being anchored to living cell surfaces, this logic nanosensor imaged extracellular K⁺ and ATP present at abnormal levels in situ. Owing to diverse disease markers in the TME, this novel logic sensor might hold great promise for the targeted delivery of intelligent anticancer drugs and Boolean logic-controlled treatment.

Mercury mediated DNA-Au/Ag nanocluster ensembles to generate a gray code encoder for biocomputing

Boolean operations utilizing DNA as a platform for biocomputing have become a promising tool for next-generation bio-molecular computers. In the whole process of any binary data transmission, bit errors are unavoidable and commonly occur. Cascades of exclusive-OR (XOR) operations show the great potential to evaluate these errors by introducing a parity generator (pG) and a parity checker (pC). Herein, we constructed a DNA hybrid architecture platform employing a chemosensing ensemble of mercury-mediated DNA-Au/Ag nanoclusters (M-Au/Ag NCs) to operate unconventional pG/pC for "error detection". Taking advantage of pG/pC, the transmitted and received data is converted to secure information using a binary to gray code encoder. To the best of our knowledge, this is the first molecular gray code encoder for biocomputing, which discovers an exciting avenue to protect information security through sophisticated logic circuits.

Contrary Logic Pair Library, Parity Generator/Checker and Various Concatenated Logic Circuits Engineered by a Label-Free and Immobilization-Free Electrochemiluminescence Resonance Energy Transfer System

Herein, a label-free and immobilization-free electrochemiluminescence resonance energy transfer (ECL-RET) system based on graphitic carbon nitride nanosheets (GCNNs)/Ru(phen)32+ donor/acceptor pair is developed, in which the ECL-RET is regulated by regulating the diffusivity of Ru(phen)32+ molecules toward the negatively charged GCNNs through logically programmed DNA hybridization reactions. The two optical signals of GCNNs (445 nm) and Ru(phen)32+ (593 nm) show completely opposite changes through the same one-time DNA hybridization reaction. Based on this ECL-RET system, a contrary logic pair (CLP) library, a parity generator/checker system for differentiating the erroneous bits during data transmission, the parity checker to identify the even/odd natural numbers from 0 to 9, and a series of concatenated logic circuits including a six-input logic gate capable of implementing of 64 input combinations for meeting the needs of computational complexity are developed. The ECL-RET-based molecular logic system avoids the time-consuming, costly and inefficient labeling procedures and the laborious processes of immobilization, presenting great potential for building more complicated and advanced logic gates, and providing a refreshing inspiration for the construction of combinatorial logic circuits based on ECL method.

Current progress in metabolomics of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is one of the most common metabolic disorders of pregnancy and can cause short- and long-term adverse effects in both pregnant women and their offspring. However, the etiology and pathogenesis of GDM are still unclear. As a metabolic disease, GDM is well suited to metabolomics study, which can monitor the changes in small molecular metabolites induced by maternal stimuli or perturbations in real time. The application of metabolomics in GDM can be used to discover diagnostic biomarkers, evaluate the prognosis of the disease, guide the application of diet or drugs, evaluate the curative effect, and explore the mechanism. This review provides comprehensive documentation of metabolomics research methods and techniques as well as the current progress in GDM research. We anticipate that the review will contribute to identifying gaps in the current knowledge or metabolomics technology, provide evidence-based information, and inform future research directions in GDM.

The Construction of DNA Logic Gates Restricted to Certain Live Cells Based on the Structure Programmability and Aptamer-Cell Affinity of G-Quadruplexes

DNA computation is considered a fascinating alternative to silicon-based computers; it has evoked substantial attention and made rapid advances. Besides realizing versatile functions, implementing spatiotemporal control of logic operations, especially at the cellular level, is also of great significance to the development of DNA computation. However, developing simple and efficient methods to restrict DNA logic gates performing in live cells is still a challenge. In this work, a series of DNA logic gates was designed by taking full advantage of the diversity and programmability of the G-quadruplex (G4) structure. More importantly, by further using the high affinity and specific endocytosis of cells to aptamer G4, an INHIBIT logic gate has been realized whose operational site is precisely restricted to specific live cells. The design strategy might have great potential in the field of molecular computation and smart bio-applications.

Information processing using an integrated DNA reaction network

Living organisms use interconnected chemical reaction networks (CRNs) to exchange information with the surrounding environment and respond to diverse external stimuli. Inspired by nature, numerous artificial CRNs with a complex information processing function have been recently introduced, with DNA as one of the most attractive engineering materials. Although much progress has been made in DNA-based CRNs in terms of controllable reaction dynamics and molecular computation, the effective integration of signal translation with information processing in a single CRN remains to be difficult. In this work, we introduced a stimuli-responsive DNA reaction network capable of integrated information translation and processing in a stepwise manner. This network is designed to integrate sensing, translation, and decision-making operations by independent modules, in which various logic units capable of performing different functions were realized, including information identification (YES and OR gates), integration (AND and AND-AND gates), integration-filtration (AND-AND-NOT gate), comparison (Comparator), and map-to-map analysis (Feynman gate). Benefitting from the modular and programmable design, continuous and parallel processing operations are also possible. With the innovative functions, we show that the DNA network is a highly useful addition to the current DNA-based CRNs by offering a bottom-up strategy to design devices capable of cascaded information processing with high efficiency.

Scalable Logic Circuits with Multiple Outputs and an Automatic Reset Function Based on DNAzyme-Mediated Branch Migration

A scalable logic platform made up of multilayer DNA circuits was constructed using Pb²⁺, Cu²⁺, and Zn²⁺ as the three inputs and three different fluorescent signals as the outputs. DNAzyme-guided cyclic cleavage reactions and DNA toehold-mediated strand branch migration were utilized to organize and connect nucleic acid probes for building the high-level logic architecture. The sequence communications between each circuit enable the logic network to work as a keypad lock, which is an information protection model at the molecular level. The multi-output mode was used to monitor the gradual unlocking process of the security system, from which one can determine which password is correct or not immediately. The autocatalytic cleavage of DNAzyme makes the biocomputing circuit feasible to realize the reset function automatically without external stimuli. Importantly, the logic platform is robust and can work effectively even in complex environmental samples.

Self-powered molecule release systems activated with chemical signals processed through reconfigurable Implication or Inhibition Boolean logic gates

The Implication (IMPLY) and Inhibition (INHIB) Boolean logic gates were realized using switchable chimeric pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH-Clamp) containing a fused affinity clamp unit recognizing a signal-peptide. The second component of the logic gate was the wild-type PQQ-glucose dehydrogenase working cooperatively with the PQQ-GDH-Clamp enzyme. The IMPLY and INHIB gates were realized using the same enzyme composition activated with differently defined input signals, thus representing reconfigurable logic systems. The logic gates were first tested while operating in a solution with optical analysis of the output signals. Then, the enzymes were immobilized on a buckypaper electrode for electrochemical transduction of the output signals. The switchable modified electrodes mimicking the IMPLY or INHIB logic gates were integrated with an oxygen-reducing electrode modified with bilirubin oxidase to operate as a biofuel cell activated/inhibited by various input signal combinations processed either by IMPLY or INHIB logic gates. The switchable biofuel cell was used as a self-powered device triggering molecule release function controlled by the logically processed molecule signals.

A versatile molecular logic system based on Eu(III) coordination polymer film electrodes combined with multiple properties of NADH

Herein, a new type of lanthanide coordination polymer film made up of europium (Eu(iii)) and poly(N-methacryloylglycine) (Eu(iii)-PMAG) was prepared on an ITO electrode surface driven by the coordination between N-methacryloylglycine (MAG) and Eu(iii) through a single-step polymerization process. The fluorescence signal of Eu(iii)-PMAG films at 617 nm originating from Eu(iii) could be well retained in the buffer solution but was regulated by the concentration of Cu(ii) and the complexing agent EDTA. The switching of fluorescence by Cu(ii) was attributed to the inhibition of the "antenna effect" between Eu(iii) and the MAG ligand in the films. The coexistence of reduced β-nicotinamide adenine dinucleotide (NADH) in the solution can apparently quench the fluorescence of Eu(iii)-PMAG films through the internal filtration effect of UV absorbance overlapping the excitation wavelength, but itself exhibiting a fluorescence emission at 468 nm. In addition, the electrocatalytic oxidation of NADH with the help of the ferrocenedicarboxylic acid (FcDA) probe demonstrated a cyclic voltammetry (CV) signal at 0.45 V (vs. SCE). Based on various reversible stimulus-responsive behaviours, a 4-input/10-output logic network was built using Cu(ii), EDTA, NADH and FcDA as inputs and the signals of fluorescence from Eu(iii)-PMAG (617 nm) and NADH (468 nm), the CV response from FcDA and the UV-vis absorbance from the Cu(ii)-EDTA complex as outputs. Meanwhile, 6 different functional logic devices were constructed based on the same versatile platform, including a 2-to-1 encoder, a 1-to-2 decoder, a 1-to-2 demultiplexer, a parity checker, a transfer gate and a reprogrammable 3-input/2-output keypad lock. Combined with the new type of lanthanide coordination polymer film, NADH played central roles in designing sophisticated computing systems with its fluorescence, UV and electrocatalytic properties. This work might provide a novel avenue to develop intelligent multi-analyte sensing and information processing at the molecular level based on one single platform.

Condensation Product of p-anisaldehyde and L-phenylalanine: Fluorescent "on-off" Sensor for Cu2+ and IMPLICATION Logic Gate

(Z)-2-(4-methoxybenzylideneamino)-3-phenylpropanoic acid (L) synthesized by condensation of p-anisaldehyde and L-phenylalanine acts as selective fluorescent as well as voltammetric sensor for Cu²⁺ in 2:1 (v/v) CH₃OH:H₂O. The fluorescence intensity of L (λ_max 425 nm) is quenched ca. 65% by Cu²⁺. Metal ions - Li⁺, Na⁺, K⁺, Al³⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Mn²⁺, Ni²⁺ and Pb²⁺ do not interfere. The binding constant and the detection limits were calculated to be 0.56 × 10² M^-1 and 10^-6 M respectively. DFT and TDDFT calculations confirmed 2:1 binding stoichiometry between L and Cu²⁺ obtained from fluorescence data. The interaction between L and Cu²⁺ is reversible for many cycles with respect to ethylenediamine tetraacetate anion (EDTA^2-) which results in IMPLICATION logic gate.

Indicator Displacement Assay Inside Dye-Functionalized Covalent Organic Frameworks for Ultrasensitive Monitoring of Sialic Acid, an Ovarian Cancer Biomarker

Identifying biomolecules for disease diagnosis requires simple, accurate, and reliable analytical techniques. Multiple signal transduction pathways have promoted the development of various biological analysis systems. However, most systems are largely limited by a single mechanism or model analysis, which can easily lead to false-positive/negative results. Herein, we report a covalent organic framework (COF) (TpPa-1) functionalized with a dye (fluorescein sodium) and design this hybrid material (TpPa-1@Dye) to fabricate hydrogels for subsequent analysis with the indicator displacement assay (IDA) method. Selecting a suitable metal cation (Cr³⁺) for the preparation of hydrogels can reduce the background fluorescence, improve the detection sensitivity, and increase the corresponding sensing selectivity. The TpPa-1@Dye functions as an indicator in the IDA-in-COF system, and Cr³⁺ is a receptor of the analyte (sialic acid (SA), a biomarker for ovarian cancer diagnosis). Based on the above studies, the integrative logic operations (AND + IMP) are further established, it helps in elucidating the design rules of the IDA-in-COF approach. This work represents the first effort in designing IDA-in-COF luminescent sensors with an On-Off-On mechanism to determine biomarkers and provides a new approach for developing hybrid COF luminescent materials as analysis platforms for human health monitoring.

In situ formation of transcriptional modulators using non-canonical DNA i-motifs

Herein, i-motif DNA-immobilized magnetic nanoparticles are used as templates to promote the in situ cycloaddition generating specific binders for i-motifs.

Non-canonical DNA i-motifs and G-quadruplexes are postulated as genetic switches for the transcriptional regulation of proto-oncogenes. However, in comparison to G-quadruplexes, the therapeutic potential of i-motifs is less explored. The development of i-motif selective ligands by conventional approaches is challenging due to the structural complexity of i-motifs. The target guided synthetic (TGS) approach involving in situ cycloaddition could provide specific ligands for these dynamic DNA structures. Herein, we have used i-motif forming C-rich DNA and their complementary G-quadruplex forming DNA sequences of c-MYC and BCL2 promoter regions as well as a control self-complementary duplex DNA sequence as the templates to generate selective ligands from a pool of reactive azide–alkyne building blocks. In our approach, thiolated DNA targets are immobilized on the surface of gold-coated iron nanoparticles to enable efficient isolation of the newly generated ligands from the solution mixture by simple magnetic decantation. The combinatorial in situ cycloaddition generated cell-membrane permeable triazole leads for respective DNA targets (c-MYC and BCL2 i-motifs and G-quadruplexes) that selectively promote their formation. In vitro cellular studies reveal that the c-MYC i-motif and G-quadruplex leads downregulate c-MYC gene expression whereas the BCL2 i-motif lead upregulates and the BCL2 G-quadruplex lead represses BCL2 gene expression. The TGS strategy using i-motif DNA nanotemplates represents a promising platform for the direct in situ formation of i-motif specific ligands for therapeutic intervention.

A Janus-inspired amphichromatic system that kills two birds with one stone for operating a "DNA Janus Logic Pair" (DJLP) library

Although DNA computing has exhibited a magical power across diverse areas, current DNA logic gates with different functions are always separately operated and can only produce hard-to-visualize output. The fussy/obligatory gates' redesign/reconstruction and the non-intuitive output cause the wastage of time and costs, low efficiency and practicality. Herein, inspired by the ancient Roman mythical God Janus, for the first time, we propose the concept of "DNA Janus Logic Pair" (DJLP) to classify the DNA logic gates with contrary functions into "Positive + Negative" gates (DJLP = Pos + Neg). Based on the biocatalytic property of G-quadruplex DNAzyme (G4zyme) and the luminescence quenching ability of oxidized 3,3',5,5'-tetramethylbenzidine (OxTMB) towards the upconversion (UC) particles, we fabricated a universal amphichromatic platform that kills two birds with one stone for operating a versatile DJLP library. Different from the previous DNA logic systems, the "Pos + Neg" gates of each DJLP in this study were concomitantly achieved via the same one-time DNA reaction, which avoided the gates' redesign/reoperation and reduced the operating costs/time of the DNA gates by at least half. Besides, both the amphichromatic outputs (Visual-blue and UC luminescent-green) can be visualized under harmless-NIR, thus bringing greatly enhanced practicality to the method. Moreover, we constructed various concatenated logic circuits via logically modulating the G4zyme's biocatalytic property with glutathione, thus enabling the largely improved computing complexity. Furthermore, taking the circuit "YES-INH-1-2 decoder" as the "computing core", we designed an "antioxidant indicator" with ratiometric logical responses that could recognize the presence of antioxidants smartly (output changed from "10" to "01"), which provided a typical prototype for potential intelligent bio-applications.

MIL-61 and Eu3+@MIL-61 as Signal Transducers To Construct an Intelligent Boolean Logical Library Based on Visualized Luminescent Metal-Organic Frameworks

MIL-61 and its postsynthesis product (Eu³⁺@MIL-61) are employed as signal transducers to construct a series of basic logic gates (NOT, NAND, INHIBIT, and XNOR) on account of their simple synthetic process and fascinating luminescent properties. Also, a two-output combinational logic gate and a cascaded logic gate can be constructed on these two signal transducers by changing the inputs. In this logic gate library system, the fluorescence of MIL-61 (λ_395nm) or Eu³⁺@MIL-61 (λ_615nm) is used as outputs with a threshold of 0.5. The advantage of this boolean logical library is that the two signal transducers are readily available and cost effective. In addition, the luminescence change is visible to the naked eye under a UV lamp, which is more convenient in application. More importantly, it presents a new route for the design of a molecular logic gate library based on luminescent metal-organic frameworks. And for further application, we experimentally construct two logic devices (a 4-to-2 encoder and a parity checker) based on Eu³⁺@MIL-61 to perform nonarithmetic information.

Recent Progress in Fluorescence Signal Design for DNA-Based Logic Circuits

DNA-based logic circuits, encoding algorithms in DNA and processing information, are pushing the frontiers of molecular computers forward, owing to DNA's advantages of stability, accessibility, manipulability, and especially inherent biological significance and potential medical application. In recent years, numerous logic functions, from arithmetic to nonarithmetic, have been realized based on DNA. However, DNA can barely provide a detectable signal by itself, so that the DNA-based circuits depend on extrinsic signal actuators. The signal strategy of carrying out a response is becoming one of the design focuses in DNA-based logic circuit construction. Although work on sequence and structure design for DNA-based circuits has been well reviewed, the strategy on signal production lacks comprehensive summary. In this review, we focused on the latest designs of fluorescent output for DNA-based logic circuits. Several basic strategies are summarized and a few designs for developing multi-output systems are provided. Finally, some current difficulties and possible opportunities were also discussed.

Fabrication of prime number checkers based on colorimetric responses of gold nanoparticles

In this work, we demonstrated the fabrication of molecular prime number checkers based on the concentration- and sequence-dependent colorimetric responses of citrate-capped gold nanoparticles (Au NPs) to two simple model chemicals, i.e. cysteine (Cys) and Hg²⁺ ions.

A simple, label-free, electrochemical DNA parity generator/checker for error detection during data transmission based on "aptamer-nanoclaw"-modulated protein steric hindrance

The first electrochemical DNA parity generator/checker system for error detection during data transmission was constructed based on “aptamer-nanoclaw”-modulated protein steric hindrance.

Versatile DNA logic devices have exhibited magical power in molecular-level computing and data processing. During any type of data transmission, the appearance of erroneous bits (which have severe impacts on normal computing) is unavoidable. Luckily, the erroneous bits can be detected via placing a parity generator (pG) at the sending module and a parity checker (pC) at the receiving module. However, all current DNA pG/pC systems use optical signals as outputs. In comparison, sensitive, facilely operated, electric-powered electrochemical outputs possess inherent advantages in terms of potential practicability and future integration with semiconductor transistors. Herein, taking an even pG/pC as a model device, we construct the first electrochemical DNA pG/pC system so far. Innovatively, a thrombin aptamer is integrated into the input-strand and it functions as a “nanoclaw” to selectively capture thrombin; the electrochemical impedance changes induced by the “nanoclaw/thrombin” complex are used as label-free outputs. Notably, this system is simple and can be operated within 2 h, which is comparable with previous fluorescent ones, but avoids the high-cost labeled-fluorophore and tedious nanoquencher. Moreover, taking non-interfering poly-T strands as additional inputs, a cascade logic circuit (OR-2 to 1 encoder) and a parity checker that could distinguish even/odd numbers from natural numbers (0 to 9) is also achieved based on the same system. This work not only opens up inspiring horizons for the design of novel electrochemical functional devices and complicated logic circuits, but also lays a solid foundation for potential logic-programmed target detection.

Enzyme-Regulated DNA-Based Logic Device

Herein, we report a carbazole (Cz) ligand that displays distinct turn-on fluorescence signals upon interaction with human telomeric G-quadruplex ( h-TELO) and nuclease enzymes. Interestingly, Cz selectively binds and stabilizes the mixed hybrid topology of h-TELO G-quadruplex that withstands digestion by exonucleases and nuclease S1. The distinct fluorescence signatures of Cz-stabilized h-TELO with nucleases are used to design conceptually novel DNA devices for selectively detecting the enzymatic activity of DNase I as well as performing logic operations. An INHIBIT logic gate is constructed using h-TELO and DNase I as the inputs while the inputs of h-TELO and nuclease S1 form a YES logic gate. Furthermore, a two-input two-output reusable logic device with "multireset" function is developed by using h-TELO and DNase I as inputs. On the basis of this platform, combinatorial logic systems (INHIBIT-INHIBIT and NOR-OR) have been successfully installed using different combinations of nucleases as inputs. Moreover, this new strategy of using a synthetic dual emissive probe and enzyme/DNA inputs for constructing reusable logic device may find important applications in biological computing and information processing.

Molecular logic gates: the past, present and future

The field of molecular logic gates originated 25 years ago, when A. P. de Silva published a seminal article in Nature. Stimulated by this ground breaking research, scientists were inspired to join the race to simulate the workings of the fundamental components of integrated circuits using molecules. The rules of this game of mimicry were flexible, and have evolved and morphed over the years. This tutorial review takes a look back on and provides an overview of the birth and growth of the field of molecular logics. Spinning-off from chemosensor research, molecular logic gates quickly proved themselves to be more than intellectual exercises and are now poised for many potential practical applications. The ultimate goal of this vein of research became clearer only recently - to "boldly go where no silicon-based logic gate has gone before" and seek out a new deeper understanding of life inside tissues and cells.

Facile preparation of highly sensitive and selective fluorescent paper sensor for the visual and cyclic detection of Cu2+ and Hg2+

The fluorescent paper sensor based on LAA-CQDs was prepared and applied to detect heavy metal ions Cu²⁺ and Hg²⁺. Notably, the paper sensor can be recycled for detecting at least four times, which greatly reduced resource consumption.

Studies on a multifunctional chromo-fluorogenic sensor for dual channel recognition of Zn2+ and CN− ions in aqueous media: mimicking multiple molecular logic gates and memory devices

A new effectual naphthalene-based azomethine receptor has been systematically designed and synthesized as a selective colorimetric and fluorescent chemosensor for dual channel detection of cations and anions in aqueous environments.

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.

Solvent Polarity-Dependent Behavior of Aliphatic Thiols and Amines toward Intriguingly Fluorescent AuAgGSH Assembly

Highly stable fluorescent glutathione (GSH)-protected AuAg assembly has been synthesized in water under UV irradiation. The assembly is composed of small Ag₂/Ag₃ clusters. These clusters gain stability through synergistic interaction with Au(I) present within the assembly. This makes the overall assembly fluorescent. Here, GSH acts as a reducing as well as stabilizing agent. The assembly is so robust that it can be vacuum-dried to solid particles. The as-obtained solid is dispersible in nonaqueous solvents. The interaction between solvent and the assembly provides stability to the assembly, and the assembly shows fluorescence. It is interesting to see that the behavior of long-chain aliphatic thiols or amines toward the fluorescent assembly is altogether a different phenomenon in aqueous and nonaqueous mediums. The assembly gets ruptured in water due to direct interaction with long-chain thiols or amines, whereas in nonaqueous medium, solvation of added thiols or amines becomes pronounced, which hinders the interaction of solvent with the assembly. However, the fluorescence of the assembly is always quenched with thiols or amines no matter what the solvent medium is. In aqueous medium, the fluorescence quenching by aliphatic thiol or amine becomes pronounced with successive decrease in their chain length, whereas in nonaqueous medium, the trend is just reversed with chain length. The reasons behind such an interesting reversal of fluorescence quenching in aqueous and nonaqueous solvents have been discussed explicitly. Again, in organic solvents, thiol or amine-induced quenched fluorescence is selectively recovered by Pb(II) ion without any alteration of excitation and emission maxima. This phenomenon is not observed in water because of the ruptured fluorescent assembly. The fluorescence recovery by Pb(II) and unaltered emission peak only in nonaqueous solvent unequivocally prove the engagement of Pb(II) with thiols or amines, which in turn revert the original solvent-supported stabilization of the assembly.

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.

A quantum dot-labelled aptamer/graphene oxide system for the construction of a half-adder and half-subtractor with high resettability

By a combination of quantum dot-labelled aptamers and graphene oxide, a hybrid molecular system was developed for the integration of multiple logic gates to implement half adder and half subtractor functions. On the merits of quantum dots, repetitious arithmetic operations and a reliable fluorescent switch were demonstrated.

Coordination polymer nanoparticles from nucleotide and lanthanide ions as a versatile platform for color-tunable luminescence and integrating Boolean logic operations

Novel supramolecular coordination polymer nanoparticles (CPNs) were synthesized via the self-assembly of guanosine monophosphate (GMP) and lanthanide ions (Ln³⁺, including Tb³⁺, Eu³⁺ and Ce³⁺) in aqueous solution. These CPNs (GMP/Tb³⁺, GMP/Eu³⁺ and GMP/Ce³⁺) have an identical coordination environment but exhibit completely different luminescence properties responding to external stimuli such as dipicolinic acid (DPA), ethylene diamine tetraacetic acid (EDTA), pH and metal ions, which has inspired us to tune the emission color of the CPNs and perform multiple logic operations. Firstly, color-tunable luminescence from red to green can be easily achieved by modulating the doping ratio of Tb³⁺ and Eu³⁺ into GMP. Notably, trichromatic white light emitting CPNs can be successfully realized by simultaneously doping Tb³⁺, Eu³⁺ and Ce³⁺ into the host or just adjusting the pH of the solution. What's more, by employing GMP/Tb³⁺ CPNs as a logic operator, we have achieved the implementation of multilayered gate cascades (INH-INH, NOR-OR). When GMP/Eu³⁺ CPNs served as a logic operator, the logic elements can be integrated as another combinatorial gate (AND-INH). Moreover, by employing the red emission of Eu³⁺ and blue emission of GMP as the dual-output signal transducer, a set of parallel logic gates was established successfully. These results help elucidate the design rules by which simple logic can be integrated to construct cascaded logic gates and expand the applications of CPNs in light-emitting diode (LED) lamps and biological systems.

Integration of G-quadruplex and DNA-templated Ag NCs for nonarithmetic information processing

To create sophisticated molecular logic circuits from scratch, you may not believe how common the building blocks can be and how diverse and powerful such circuits can be when scaled up. Using the two simple building blocks of G-quadruplex and silver nanoclusters (Ag NCs), we experimentally construct a series of multifunctional, label-free, and multi-output logic circuits to perform nonarithmetic functions: a 1-to-2 decoder, a 4-to-2 encoder, an 8-to-3 encoder, dual transfer gates, a 2 : 1 multiplexer, and a 1 : 2 demultiplexer. Moreover, a parity checker which is capable of identifying odd and even numbers from natural numbers is constructed conceptually. Finally, a multi-valued logic gate (ternary inhibit gate) is readily achieved by taking this DNA/Ag NC system as a universal platform. All of the above logic circuits share the same building blocks, indicating the great prospects of the assembly of nanomaterials and DNA for biochemical logic devices. Considering its biocompatibility, the novel prototypes developed here may have potential applications in the fields of biological computers and medical diagnosis and serve as a promising proof of principle in the not-too-distant future.

Fluorescent detection of multiple ions by two related chemosensors: structural elucidations and logic gate applications

Two related chemosensors L1 and L2 display selective detection of multiple ions (Cu²⁺, Al³⁺, Cd²⁺ and S²⁻) as a result of minor variation of functional groups at a remote arene ring.

A resettable and reprogrammable biomolecular keypad lock with dual outputs based on glucose oxidase-Au nanoclusters-Prussian blue nanocomposite films on an electrode surface

In this work, electrochromic Prussian blue (PB) films were electrodeposited on the surface of indium tin oxide (ITO) electrodes, and a dispersion mixture of glucose oxidase (GOD), chitosan (CS) and gold nanoclusters (AuNCs) was then cast on the PB surface to form CS-AuNC-GOD/PB nanocomposite film electrodes. The blue PB component in the films could be changed into its colourless reduced form of Prussian white (PW) upon application of -0.2 V. The addition of glucose to the solution would produce H₂O₂ with the help of GOD in the films and oxygen in the solution, which could oxidize PW back to PB. In the meantime, the fluorescence emission signal of the AuNCs in the films was greatly influenced by the form of PB/PW. Based on these properties, the amperometric current, fluorescence intensity and UV-vis absorbance of the film electrodes demonstrated potential- and glucose-sensitive ON-OFF behaviors. Thus, a 2-input/3-output biomolecular logic gate system with 3 different types of output signals and a 2-to-1 encoder were developed. Furthermore, a resettable and reprogrammable 3-input biomolecular keypad lock was established with fluorescence intensity and UV-vis absorbance as dual outputs, which greatly enhanced the security level of the keypad lock. This work reported for the first time an enzyme-based keypad lock with dual outputs, which might open a new avenue to design more complicated biomolecular keypad lock systems.

The analytical and biomedical potential of cytosine-rich oligonucleotides: A review

Polycytosine DNA strands are often found among natural sequences, including the ends of telomeres, centromeres, and introns or in the regulatory regions of genes. A characteristic feature of oligonucleotides that are rich in cytosine (C-rich) is their ability to associate under acidic conditions to form a tetraplex i-motif consisting of two parallel stranded cytosine-hemiprotonated cytosine (C·C+) base-paired duplexes that are mutually intercalated in an antiparallel orientation. Nanotechnology has been exploiting the advantages of i-motif pH-dependent formation to fabricate nanomachines, nanoswitches, electrodes and intelligent nanosurfaces or nanomaterials. Although a few reviews regarding the structure, properties and applications of i-motifs have been published, this review focuses on recently developed biosensors (e.g., to detect pH, glucose or silver ions) and drug-delivery biomaterials. Furthermore, we have included examples of sensors based on parallel C-rich triplexes and silver nanoclusters (AgNCs) fabricated on cytosine-rich DNA strands. The potential diagnostic and therapeutic applications of this type of material are discussed.