A Fluorophore Capable of Crossword Puzzles and Logic Memory

Algorithm in chemistry: molecular logic gate-based data protection

Data security is crucial for safeguarding the integrity, authenticity, and confidentiality of documents, currency, merchant labels, and other paper-based assets, which sequentially has a profound impact on personal privacy and even national security. High-security-level logic data protection paradigms are typically limited to software (digital circuits) and rarely applied to physical devices using stimuli-responsive materials (SRMs). The main reason is that most SRMs lack programmable and controllable switching behaviors. Traditional SRMs usually produce static, singular, and highly predictable signals in response to stimuli, restricting them to simple "BUFFER" or "INVERT" logic operations with a low security level. However, recent advancements in SRMs have collectively enabled dynamic, multidimensional, and less predictable output signals under external stimuli. This breakthrough paves the way for sophisticated encryption and anti-counterfeiting hardware based on SRMs with complicated logic operations and algorithms. This review focuses on SRM-based data protection, emphasizing the integration of intricate logic and algorithms in SRM-constructed hardware, rather than chemical or material structural evolutions. It also discusses current challenges and explores the future directions of the field-such as combining SRMs with artificial intelligence (AI). This review fills a gap in the existing literature and represents a pioneering step into the uncharted territory of SRM-based encryption and anti-counterfeiting technologies.

Activatable Near-Infrared Versatile Fluorescent and Chemiluminescent Dyes Based on the Dicyanomethylene-4H-pyran Scaffold: From Design to Imaging and Theranostics

Activatable fluorescent and chemiluminescent dyes with near-infrared emission have indispensable roles in the fields of bioimaging, molecular prodrugs, and phototheranostic agents. As one of the most popular fluorophore scaffolds, the dicyanomethylene-4H-pyran scaffold has been applied to fabricate a large number of versatile activatable optical dyes for analytes detection and diseases diagnosis and treatment by virtue of its high photostability, large Stokes shift, considerable two-photon absorption cross-section, and structural modifiability. This review discusses the molecular design strategies, recognition mechanisms, and both in vitro and in vivo bio-applications (especially for diagnosis and therapy of tumors) of activatable dicyanomethylene-4H-pyran dyes. The final section describes the current shortcomings and future development prospects of this topic.

Dual-channel recognition of Al3+ and Cu2+ ions using a chiral pyrene-based fluorescent sensor

Specific recognition between Al3+ and Cu2+ has been achieved based on the new mechanism of Cu2+ detection by pyrene dimerization.

Light and Cation-Driven Optical Switch based on a Stilbene-Appended Terpyridine System for the Design of Molecular-Scale Logic Devices

A molecular system comprising a terpyridine moiety capable of coordinating with different cations and a photoswitchable stilbene unit has been utilized here for the fabrication of multiply configurable logic systems. Incorporation of a substituted stilbene unit into the terpyridine motif generates an intraligand charge-transfer-sensitive module whose absorption and emission spectral properties are highly sensitive to light as well as cations. On the basis of the optical response profile of the receptor in the presence of selected cations as well as light of a specific wavelength, we are able to demonstrate multiple Boolean logic functions such as INHIBIT, IMPLICATION, OR, NOR, and NAND, as well as various combinations of them. Of particular interest, we utilized the present system for the construction of security keypad locks and memory devices by maintaining a proper sequence of the stimuli and monitoring either absorption or emission spectral response at a specific wavelength as the output signal. In addition to various Boolean logic functions, the present system has also the ability to mimic fuzzy logic operations for generating an infinite-valued logic scheme depending on its emission spectral responses upon varying the concentration of cationic (Fe²⁺ and/or Zn²⁺) and anionic (CN^-) inputs.

Fluorescent probes based on nucleophilic aromatic substitution reactions for reactive sulfur and selenium species: Recent progress, applications, and design strategies

Reactive sulfur species (RSS) and reactive selenium species (RSeS) are important substances for the maintenance of physiological balance. Imbalance of RSS and RSeS is closely related to a series of human diseases, so it is considered to be an important biomarker in early diagnosis, treatment, and stage monitoring. Fast and accurate quantitative analysis of different RSS and RSeS in complex biological systems may promote the development of personalized diagnosis and treatment in the future. One way to explore the physiological function of various types of RSS and RSeS in vivo is to detect them at the molecular level, and one of the most effective methods for this is to use fluorescent probes. Nucleophilic aromatic substitution (SNAr) reactions are commonly exploited as a detection mechanism for RSS and RSeS in fluorescent probes. In this review, we cover recent progress in fluorescent probes for RSS and RSeS based on SNAr reactions, and discuss their response mechanisms, properties, and applications. Benzenesulfonate, phenyl-O ether, phenyl-S ether, phenyl-Se ether, 7-nitro-2,1,3-benzoxadiazole (NBD), benzoate, and selenium-nitrogen bonds are all good detection groups. Moreover, based on an integration of different reports, we propose the design and synthesis of RSS- and RSeS-selective probes based on SNAr reactions, current challenges, and future research directions, considering the selection of active sites, the effect of substituents on the benzene ring, and the introduction of other functional groups.

Photophysical Properties of 4-Dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran Revisited: Fluorescence versus Photoisomerization

Although 4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM) has been known for many decades as a bright and photostable fluorophore, used for a wide variety of applications in chemistry, biology and physics, only little attention has been paid so far to the presence of multiple isomers and conformers, namely s-trans-(E), s-cis-(E), s-trans-(Z), and s-cis-(Z). In particular, light-induced E-Z isomerization plays a great role on the overall photophysical properties of DCM. Herein, we give a full description of a photoswitchable DCM derivative by a combination of structural, theoretical and spectroscopic methods. The main s-trans-(E) isomer is responsible for most of the fluorescence features, whereas the s-cis-(E) conformer only contributes marginally. The non-emitting Z isomers are generated in large conversion yields upon illumination with visible light (e.g., 485 or 514 nm) and converted back to the E forms by UV irradiation (e.g., 365 nm). Such photoswitching is efficient and reversible, with high fatigue resistance. The E→Z and Z→E photoisomerization quantum yields were determined in different solvents and at different irradiation wavelengths. Interestingly, the fluorescence and photoisomerization properties are strongly influenced by the solvent polarity: the fluorescence is predominant at higher polarity, whereas photoisomerization becomes more efficient at lower polarity. Intermediate medium (THF) represents an optimized situation with a good balance between these two features.

The improved targeting of an aspirin prodrug albumin-based nanosystem for visualizing and inhibiting lung metastasis of breast cancer

Lung metastasis is the principal reason for the majority of deaths from breast cancer. The nonsteroidal anti-inflammatory drug aspirin can prevent lung metastasis in breast tumors via inhibiting heparanase. However, the lack of specific targets and limited accumulation at the site of the tumor have thus far hindered the use of aspirin in oncotherapy. In this study, we developed the nanoplatform FA-BSA@DA and loaded it with the versatile aspirin prodrug DA to visualize and inhibit breast cancer metastasis via targeting heparanase. This nanosystem can be effectively targeted to folic acid (FA)-positive tumor cells, and would then subsequently release a high dose of DA, whose ester bond is specifically ruptured by H2O2 in the tumor microenvironment to afford the therapeutic drug aspirin and near-infrared (NIR) fluorescent reporter DCM. The released aspirin can effectively prevent breast cancer lung metastasis through the inhibition of heparanase activity, and the NIR fluorescent signals emitted from DCM can be used to monitor and evaluate the metastasis levels of breast cancer. Our results showed that the expression of heparanase was significantly decreased, and lung metastasis from breast cancer was effectively monitored and inhibited after treatment with FA-BSA@DA. Furthermore, the collaborative therapy nanoplatform FA-BSA@DA/DOX exhibited strong therapeutic effects in the treatment of breast cancer in vitro and in vivo via the introduction of doxorubicin (DOX) to the system, which resulted in an even stronger result due to its synergistic effects with aspirin. This heparanase-reliant strategy has profound significance for the extended development of nanoplatforms based on versatile aspirin prodrugs, which may offer a solution to clinically prevent breast cancer recurrence and lung metastasis.

High-Performance Quinoline-Malononitrile Core as a Building Block for the Diversity-Oriented Synthesis of AIEgens

In vivo fluorescent monitoring of physiological processes with high-fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation-caused quenching (ACQ) and short-wavelength fluorescence. The development of high-performance and long-wavelength aggregation-induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline-malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near-infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale-up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.

Engineering diformyl diaryldipyrromethane into a molecular keypad lock

A diaryldipyrromethane-based acyclic system acts as a photolabile sequential chemosensor for both anions and cations via ESIDPT and deprotonation, which is engineered into a fluorescent molecular keypad lock system.

A point-of-care diagnostics logic detector based on glucose oxidase immobilized lanthanide functionalized metal-organic frameworks

In this work, a novel lanthanide functionalized metal organic framework enzyme (L-MOF-enzyme) composite has been first prepared via a surface attachment strategy between Eu³⁺@UMOF and glucose oxidase (GOx). Here, the Eu³⁺@UMOF can be used as a support for GOx immobilization and also a responsive fluorescent center towards glucose (Glu). The resulting material not only exhibits fascinating luminescence properties based on the ⁵D₀→⁷F₂ transition of Eu³⁺ and the catalytic performance of enzymes, but also some advantages of MOF-enzyme composites, including better stability, and great fluorescence selectivity and sensitivity towards Glu (detection limit = 0.2 μM). Besides, the composite exhibited an excellent selectivity and sensitivity towards Glu in serum and urine under room temperature and neutral conditions, which breaks the limitation of specific catalytic conditions of enzymes. Taking all the advantages of the L-MOF-enzyme composite, a point-of care (POC) diagnostics logic detector which can be used for the fluorescence detection of Glu in urine is designed. From the three outputs of the logic detector (L, M and H), we can intuitively realize the self-diagnosis of the three ranges of Glu concentrations that act as the inputs of the detector (0.1 μM-10 μM, 10 μM-10 mM, >10 mM) by the naked eye. The logic detector allows us, especially diabetics, to instantly detect glucose levels in the urine without going to the hospital for complicated inspections. This is the first attempt using L-MOFs combined with GOx to construct a POC diagnostics logic detector for fluorescence detection of Glu.

A Versatile Naphthalimide-Sulfonamide-Coated Tetraphenylethene: Aggregation-Induced Emission Behavior, Mechanochromism, and Tracking Glutathione in Living Cells

A tetraphenylethene (TPE) derivative substituted with a sulfonyl-based naphthalimide unit (TPE-Np) was designed and synthesized. Its optical properties in solution and in the solid state were investigated. Photophysical properties indicated that the target molecule, TPE-Np, possessed aggregation-induced emission (AIE) behavior, although the linkage between TPE and the naphthalimide unit was nonconjugated. Additionally, it exhibited an unexpected, highly reversible mechanochromism in the solid state, which was attributed to the change in manner of aggregation between crystalline and amorphous states. On the other hand, a solution of TPE-Np in a mixture of dimethyl sulfoxide/phosphate-buffered saline was capable of efficiently distinguishing glutathione (GSH) from cysteine and homocysteine in the presence of cetyltrimethylammonium bromide. Furthermore, the strategy of using poly(ethylene glycol)-polyethylenimine (PEG-PEI) nanogel as a carrier to cross-link TPE-Np to obtain a water-soluble PEG-PEI/TPE-Np nanoprobe greatly improved the biocompatibility, and this nanoprobe could be successfully applied in the visualization of GSH levels in living cells.

An enzyme-activatable probe liberating AIEgens: on-site sensing and long-term tracking of β-galactosidase in ovarian cancer cells

Development of fluorescent probes for on-site sensing and long-term tracking of specific biomarkers is particularly desirable for the early detection of diseases. However, available small-molecule probes tend to facilely diffuse across the cell membrane or remain at the activation site but always suffer from the aggregation-caused quenching (ACQ) effect. Here we report an enzyme-activatable aggregation-induced emission (AIE) probe QM-βgal, which is composed of a hydrophilic β-galactosidase (β-gal)-triggered galactose moiety and a hydrophobic AIE-active fluorophore QM-OH. The probe is virtually non-emissive in aqueous media, but when activated by β-gal, specific enzymatic turnover would liberate hydrophobic AIE luminogen (AIEgen) QM-OH, and then highly fluorescent nanoaggregates are in situ generated as a result of the AIE process, allowing for on-site sensing of endogenous β-gal activity in living cells. Notably, taking advantage of the improved intracellular retention of nanoaggregates, we further exemplify QM-βgal for long-term (∼12 h) visualization of β-gal-overexpressing ovarian cancer cells with high fidelity, which is essential for biomedicine and diagnostics. Thus, this enzyme-activatable AIE probe not only is a potent tool for elucidating the roles of β-gal in biological systems, but also offers an enzyme-regulated liberation strategy to exploit multifunctional probes for preclinical applications.

Molecularly precise self-assembly of theranostic nanoprobes within a single-molecular framework for in vivo tracking of tumor-specific chemotherapy

Structural heterogeneity and the lack of in vivo real-time tracking of drug release are the utmost barriers for nanocarrier-mediated prodrugs in targeted therapy. Herein, we describe the strategy of molecularly precise self-assembly of monodisperse nanotheranostics for BP n -DCM-S-CPT (n = 0, 5 and 20) with fixed drug loadings (36%, 23% and 16%) and constant release capacities, permitting in vivo real-time targeted therapy. We focus on regulating the hydrophilic fragment length to construct stable, well-defined nanostructured assemblies. Taking the bis-condensed dicyanomethylene-4H-pyran (DCM) derivative as the activatable near-infrared (NIR) fluorophore, it makes full use of two terminal conjunctions: the hydrophobic disulfide-bridged anticancer prodrug camptothecin (CPT) and the hydrophilic oligomer-bridged biotin segment serving as an active targeting unit. From the rational design, only BP20-DCM-S-CPT forms uniform and highly stable self-assemblies (ca. 80 nm, critical micelle concentration = 1.52 μM) with several advantages, such as structural homogeneity, fixed drug loading efficiency, real-time drug release tracking and synergistic targeting (passive, active and activatable ability). More importantly, in vitro and in vivo experiments verify that the surface-grafted biotins of nanoassemblies are directly exposed to receptors on cancer cells, thus markedly facilitating cellular internalization. Notably, through synergistic targeting, BP20-DCM-S-CPT displays excellent tumor-specific drug release performance in HeLa tumor-bearing nude mice, which has significantly enhanced in vivo antitumor activity and nearly eradicates the tumor (IRT = 99.7%) with few side effects. For the first time, the specific molecularly precise self-assembly of BP20-DCM-S-CPT within a single-molecular framework has successfully achieved a single reproducible entity for real-time reporting of drug release and cancer therapeutic efficacy in living animals, providing a new insight into amphiphilic nanotheranostics for clinical translation.

Multicomponent reactions provide key molecules for secret communication

A convenient and inherently more secure communication channel for encoding messages via specifically designed molecular keys is introduced by combining advanced encryption standard cryptography with molecular steganography. The necessary molecular keys require large structural diversity, thus suggesting the application of multicomponent reactions. Herein, the Ugi four-component reaction of perfluorinated acids is utilized to establish an exemplary database consisting of 130 commercially available components. Considering all permutations, this combinatorial approach can unambiguously provide 500,000 molecular keys in only one synthetic procedure per key. The molecular keys are transferred nondigitally and concealed by either adsorption onto paper, coffee, tea or sugar as well as by dissolution in a perfume or in blood. Re-isolation and purification from these disguises is simplified by the perfluorinated sidechains of the molecular keys. High resolution tandem mass spectrometry can unequivocally determine the molecular structure and thus the identity of the key for a subsequent decryption of an encoded message.

Molecules for security measures: from keypad locks to advanced communication protocols

The idea of using molecules in the context of information security has sparked the interest of researchers from many scientific disciplines. This is clearly manifested in the diversity of the molecular platforms and the analytical techniques used for this purpose, some of which we highlight in this Tutorial Review. Moreover, those molecular systems can be used to emulate a broad spectrum of security measures. For a long time, molecular keypad locks enjoyed a clear preference and the review starts off with a description of how these devices developed. In the last few years, however, the field has evolved into something larger. Examples include more complex authentication protocols (multi-factor authentication and one-time passwords), the recognition of erroneous procedures in data transmission (parity devices), as well as steganographic and cryptographic protection.

Digital logic circuit based on two component molecular systems of BSA and salen

A new fluorescent molecular probe 1 was designed and constructed by combining bovine serum albumin (BSA) and N,N'-bis(salicylidene)ethylenediamine (salen). Stimulated by Zn²⁺, tris, or EDTAH₂Na₂, the distance between BSA and salen was regulated, which was accompanied by an obvious change in the fluorescence intensity at 350 or 445nm based on Förster resonance energy transfer. Moreover, based on the encoding binary digits in these inputs and outputs applying positive logic conventions, a monomolecular circuit integrating one OR, three NOT, and three YES gates, was successfully achieved.

Dual-channel near-infrared fluorescent probe for real-time tracking of endogenous γ-glutamyl transpeptidase activity

We developed a curcuminoid difluoroboron-based fluorescent probe for tracking endogenous GGT activity with dual-channel light-up near-infrared (NIR) imaging.

Boolean Logic Tree of Label-Free Dual-Signal Electrochemical Aptasensor System for Biosensing, Three-State Logic Computation, and Keypad Lock Security Operation

The most serious and yet unsolved problems of molecular logic computing consist in how to connect molecular events in complex systems into a usable device with specific functions and how to selectively control branchy logic processes from the cascading logic systems. This report demonstrates that a Boolean logic tree is utilized to organize and connect "plug and play" chemical events DNA, nanomaterials, organic dye, biomolecule, and denaturant for developing the dual-signal electrochemical evolution aptasensor system with good resettability for amplification detection of thrombin, controllable and selectable three-state logic computation, and keypad lock security operation. The aptasensor system combines the merits of DNA-functionalized nanoamplification architecture and simple dual-signal electroactive dye brilliant cresyl blue for sensitive and selective detection of thrombin with a wide linear response range of 0.02-100 nM and a detection limit of 1.92 pM. By using these aforementioned chemical events as inputs and the differential pulse voltammetry current changes at different voltages as dual outputs, a resettable three-input biomolecular keypad lock based on sequential logic is established. Moreover, the first example of controllable and selectable three-state molecular logic computation with active-high and active-low logic functions can be implemented and allows the output ports to assume a high impediment or nothing (Z) state in addition to the 0 and 1 logic levels, effectively controlling subsequent branchy logic computation processes. Our approach is helpful in developing the advanced controllable and selectable logic computing and sensing system in large-scale integration circuits for application in biomedical engineering, intelligent sensing, and control.

Co-Registered Molecular Logic Gate with a CO-Releasing Molecule Triggered by Light and Peroxide

Co-registered molecular logic gates combine two different inputs and outputs, such as light and matter. We introduce a biocompatible CO-releasing molecule (CORM, A) as Mn(I) tricarbonyl complex with the ligand 5-(dimethylamino)-N, N-bis(pyridin-2-ylmethyl) naphthalene-1-sulfonamide (L). CO release is chaperoned by turn-on fluorescence and can be triggered by light (405 nm) as well as with hydrogen peroxide in aqueous phosphate buffer. Complex A behaves as a logic "OR" gate via co-registering the inputs of irradiation (light) and peroxide (matter) into the concomitant outputs fluorescence (light) and CO (matter). Cell viability assays confirm the low toxicity of A toward different human cell lines. The CORM has been used to track the inclusion of A into cancer cells.

Message in a molecule

Since ancient times, steganography, the art of concealing information, has largely relied on secret inks as a tool for hiding messages. However, as the methods for detecting these inks improved, the use of simple and accessible chemicals as a means to secure communication was practically abolished. Here, we describe a method that enables one to conceal multiple different messages within the emission spectra of a unimolecular fluorescent sensor. Similar to secret inks, this molecular-scale messaging sensor (m-SMS) can be hidden on regular paper and the messages can be encoded or decoded within seconds using common chemicals, including commercial ingredients that can be obtained in grocery stores or pharmacies. Unlike with invisible inks, however, uncovering these messages by an unauthorized user is almost impossible because they are protected by three different defence mechanisms: steganography, cryptography and by entering a password, which are used to hide, encrypt or prevent access to the information, respectively.

Although historically common chemicals were frequently used as secret inks, the ease of readout could not prevent unauthorized reading. Here, the authors report a multi-analyte sensor that can conceal and encrypt messages by responding to simple chemicals, demonstrating a chemical means to secure communication.

A sulfur-free iridium(III) complex for highly selective and multi-signaling mercury(II)-chemosensors

A sulfur-free iridium(III) complex (pbi)2Ir(mtpy) (1) was successfully prepared and adopted as a Hg(II)-chemosensor with high selectivity and sensitivity. Multi-signaling responses towards Hg(II) ions were observed by UV-vis absorption, phosphorescence and electrochemistry measurements. With addition of Hg(II) ions, complex 1 presented quenched emission in its phosphorescence spectrum and the detection limit was as low as 2.5 × 10(-7) M. Additionally, its redox peak currents showed a broad linear relationship with the concentration of Hg(II) ions ranging from 0 to 500 μM, which was beneficial for the quantitative detection. Based on the (1)H NMR and ESI-MS analyses, the probing mechanism was tentatively supposed to be the Hg(2+)-induced changes in the local environment of complex 1. Such a response process was useful for achieving simple and effective detection of Hg(II) ions as well as developing more chemosensors.

A multi-addressable diarylethene for the selective detection of Al3+ and the construction of a logic circuit

A multi-addressable diarylethene was designed and synthesized, which not only acted as a fluorescent sensor for Al³⁺ with high selectivity, but was also used to construct a combinational logic circuit.

A rhodamine embedded bio-compatible smart molecule mimicking a combinatorial logic circuit and ‘key-pad lock’ memory device for defending against information risk

A rhodamine-based chemosensor LC with a colorimetric response towards Al³⁺ and Cu²⁺ and only a fluorescence response to Al³⁺ enables us to fabricate a ‘key-pad-logic’ function.

Rational design of novel near-infrared fluorescent DCM derivatives and their application in bioimaging

Tailoring the wavelength to NIR emission was realized by replacing the strong electron-withdrawing groups or extending the π-conjugated system based on the DCM chromophore, along with beneficial characteristics such as bright NIR fluorescence, large Stokes shift and low photo-bleaching.

A supramolecular keypad lock

The reversible photoswitching between an anthracene derivative and its [4+4] dimer, using the template effect of the CB8 macrocycle, was demonstrated. This example of supramolecular chemistry in water was harnessed to demonstrate the operation of a keypad lock device that is driven by means of light and chemicals as inputs.

A single fluorophore to address multiple logic gates

Logic gates with different radixes have been constructed using a biologically active molecule, 2-(4′-N,N-dimethylaminophenyl)imidazo[4,5-b]pyridine (DMAPIP-b).