Chiral Fluorescence Research Articles

A chemoselective and enantioselective fluorescent probe for D-Histidine in aqueous solution and living cells

D-Histidine (D-His) holds clinical relevance in the pathogenesis of various diseases, including neurological disorders and chronic kidney disease. The specific detection of D-His within biological systems holds profound significance for the early diagnosis of associated ailments. However, the design of probes targeting D-His is inherently challenging due to the presence of its enantiomers. Herein, we introduce a novel D-His fluorescence probe, designated as (S)-1, based on the 1,1’-bi-2-naphthol (BINOL) framework. Remarkably, (S)-1 demonstrates exceptional chemoselectivity and enantioselectivity towards D-His, achieving a remarkable detection limit of 4.896 nM. Moreover, the low cytotoxicity and superior biocompatibility of (S)-1 facilitate fluorescence imaging of D-His within living cellular environments. NMR analysis and theoretical calculations have substantiated the reaction products and elucidated the recognition mechanism. To our knowledge, (S)-1 stands as the inaugural BINOL-based fluorescence probe for the specific detection of D-His among the 20 common amino acids. These findings provide pivotal groundwork for the development of chiral fluorescence probes targeting amino acids.

Chiral Assembly of Perovskite Nanocrystals: Sensitive Discrimination of Amino Acid Enantiomers.

Chirality is a widespread phenomenon in nature and in living organisms and plays an important role in living systems. The sensitive discrimination of chiral molecular enantiomers remains a challenge in the fields of chemistry and biology. Establishing a simple, fast, and efficient strategy to discriminate the spatial configuration of chiral molecular enantiomers is of great significance. Chiral perovskite nanocrystals (PNCs) have attracted much attention because of their excellent optical activity. However, it is a challenge to prepare perovskites with both chiral and fluorescence properties for chiral sensing. In this work, we synthesized two chiral fluorescent perovskite nanocrystal assembly (PNA) enantiomers by using l- or d-phenylalanine (Phe) as chiral ligands. PNA exhibited good fluorescence recognition for l- and d-proline (Pro). Homochiral interaction led to fluorescence enhancement, while heterochiral interaction led to fluorescence quenching, and there is a good linear relationship between the fluorescence changing rate and l- or d-Pro concentration. Mechanism studies show that homochiral interaction-induced fluorescence enhancement is attributed to the disassembly of chiral PNA, while no disassembly of chiral PNA was found in heterochiral interaction-induced fluorescence quenching, which is attributed to the substitution of Phe on the surface of chiral PNA by heterochiral Pro. This work suggests that chiral perovskite can be used for chiral fluorescence sensing; it will inspire the development of chiral nanomaterials and chiral optical sensors.

Biomimetic chiral hydrogen-bonded organic-inorganic frameworks

Assembly ubiquitously occurs in nature and gives birth to numerous functional biomaterials and sophisticated organisms. In this work, chiral hydrogen-bonded organic-inorganic frameworks (HOIFs) are synthesized via biomimicking the self-assembly process from amino acids to proteins. Enjoying the homohelical configurations analogous to α-helix, the HOIFs exhibit remarkable chiroptical activity including the chiral fluorescence (glum = 1.7 × 10−3) that is untouched among the previously reported hydrogen-bonded frameworks. Benefitting from the dynamic feature of hydrogen bonding, HOIFs enable enantio-discrimination of chiral aliphatic substrates with imperceivable steric discrepancy based on fluorescent change. Moreover, the disassembled HOIFs after recognition applications are capable of being facilely regenerated and self-purified via aprotic solvent-induced reassembly, leading to at least three consecutive cycles without losing the enantioselectivity. The underlying mechanism of chirality bias is decoded by the experimental isothermal titration calorimetry together with theoretic simulation.

Self-assembled bamboo-like carbon nanotubes based on chiral H8BINOL sensors to recognize cinchonidine efficiently by diastereoisomer complexes.

Fluorescence recognition for the antimalarial cinchonidine could be achieved efficiently and rapidly through bamboo-like carbon nanotubes based on chiral conjugated H8BINOL derivatives. Herein, it was proved that the chiral fluorescence probe H8BINOL exhibited excellent fluorescence identification ability for cinchonidine. The structure and size of the S-1 (S-(3,3'-phenyl)-5,5'6,6',7',8,8'-octahydro-[1,1'-dinaphthalene]-2,2'-diol) and R-1 (R-(3,3'-phenyl)-5,5'6,6',7',8,8'-octahydro-[1,1'-dinaphthalene]-2,2'-diol) were studied by using the DLS, TEM, and SEM spectra, which exhibited a self-assembled bamboo-like carbon nanotube structure. In the CD (circular dichroism) test, cinchonidine was added to a pair of enantiomers of H8BINOL derivatives. The different configurations of H8BINOL derivatives showed significantly different Cotton effects for cinchonidine, indicating that cinchonidine formed diastereoisomer π-π complexes with different configurations of H8BINOL derivatives. From the AFM tests, it was revealed that cinchonidine could effectively quench the fluorescent spot of the probes quickly. The fluorescence titration tests demonstrated that 6.4 × 10-7 mol of cinchonidine could completely quench the fluorescence sensor of S-1 (2 × 10-5 M, 2 mL) through the formation of a 1 : 1 complex. The limit of detection (LOD) of S-1 was calculated to be 6.08 × 10-10, which indicates that S-1 has a high sensitivity and can be applied effectively to the practice of identifying cinchonidine. Meanwhile, the fluorescence sensor R-1 also exhibited the same sensibility with a low limit of detection (7.60 × 10-10).

Enhancing enantioselectivity in chiral metal organic framework fluorescent sensors

Zn(ii) chiral MOFs with BINOL and d-camphoric acid exhibit exceptional enantioselectivity as chiral fluorescence sensors.

High solid-state CPL active materials based on chiral BINOL-dicyanodistyrylbenzene

Herein, we synthesized a pair of aggregation-induced emission (AIE) chiral fluorescence materials (R/S-BIN-Cyn enantiomers). The enantiomers were constructed by connecting a typical AIE molecule to a chiral 1,1′-bi-2-naphthol (BINOL) with ether linkages. The obtained enantiomers exhibited excellent AIE properties and unique state circularly polarized luminescence (CPL) behavior. Specifically, the enantiomers were CPL-active in the solid film with a high glum value of −1.1 × 10−1/+1.2 × 10−1. The CPL and circular dichroism (CD) spectra showed that chirality transfer was achieved from the chiral BINOL to the achiral AIE molecule. The present study is expected to provide a new perspective for preparing chiral luminescent devices with solid-state CPL active.

Enantioselective Labeling of Zebrafish for D-Phenylalanine Based on Graphene-Based Nanoplatform.

Enantioselective labeling of important bioactive molecules in complex biological environments by artificial receptors has drawn great interest. From both the slight difference of enantiomers' physicochemical properties and inherently complexity in living organism point of view, it is still a contemporary challenge for preparing practical chiral device that could be employed in the model animal due to diverse biological interference. Herein, we introduce γ-cyclodextrin onto graphene oxide for fabricating γ-cyclodextrin and graphene oxide assemblies, which provided an efficient nanoplatform for chiral labelling of D-phenylalanine with higher chiral discrimination ratio of KD/KL = 8.21. Significantly, the chiral fluorescence quenching effect of this γ-CD-GO nanoplatform for D-phenylalanine enantiomer in zebrafish was 7.0-fold higher than L-isomer, which exhibiting real promise for producing practical enantio-differentiating graphene-based systems in a complex biological sample.

Fluorescence Filter Nanoarchitectonics with Polydiacetylene‐Based Supramolecular Chiral Gel for Generating Tunable Circularly Polarized Luminescence

AbstractCircularly polarized luminescence (CPL) can be generated from chiral luminescent materials. It can also be achieved from achiral emissive dyes by selectively filtering their fluorescence with chiroptical active materials. In this work, a novel polydiacetylene‐based supramolecular chiral gel is fabricated as a handedness‐selective fluorescence filter for generating CPL. The gelator consists of a diacetylene alkyl chain and a chiral histidine (His) head group (HisDA). It can self‐assemble into nanoribbon and turn into the blue phase, purple phase and red phase polydiacetylene‐His (HisPDA) upon photopolymerization. The resulting L/D‐HisPDA gels show variable circular dichroism (CD) with the change in color. Furthermore, multiple CPL signals are achieved after fluorescence excited with achiral dyes D1–D3 passing through HisPDA gel. The intensity of CPL increases gradually in both D1 and D3 dye systems along with the change of the HisPDA gel from blue phase to red phase, while the CPL signal is inverted for the D2 dye system. The handedness of the CPL signal is opposite to the CD signal of HisPDA gel in all the cases, demonstrating that CPL is originated through a handedness‐selective fluorescence adsorption mechanism. This study offers a new strategy for obtaining tunable CPL via adjustable chiral fluorescence filters.

Chiral amino acid recognition in water: A BINOL-based fluorescent probe

A novel BINOL-based fluorescence probe (S)-6 featuring a sodium sulfonate fragment at the 2′-position was designed and synthesized via simple synthetic procedures under mild reaction conditions. The water-soluble probe (S)-6 displays excellent enantioselective recognition toward 15 common amino acids, and it can be used for enantiomeric excess determination of amino acids. The fluorescence intensity of (S)-6 treated with amino acids reaches the maximum after standing for only 30 min at room temperature and remains stable in the following 5.5 h, which has great potential in the application of chiral fluorescence analysis due to its timeliness and outstanding fluorescent stability.

Enantioselective Recognition of L-Lysine by ICT Effect with a Novel Binaphthyl-Based Complex.

A novel triazole fluorescent sensor was efficiently synthesized using binaphthol as the starting substrate with 85% total end product yield. This chiral fluorescence sensor was proved to have high specific enantioselectivity for lysine. The fluorescence intensity of R-1 was found to increase linearly when the equivalent amount of L-lysine (0-100 eq.) was gradually increased in the system. The fluorescence intensity of L-lysine to R-1 was significantly enhanced, accompanied by the red-shift of emission wavelength (389 nm to 411 nm), which was attributed to the enhanced electron transfer within the molecular structure, resulting in an ICT effect, while the fluorescence response of D-lysine showed a decreasing trend. The enantioselective fluorescence enhancement ratio for the maximum fluorescence intensity was 31.27 [ef = |(IL - I0)/(ID - I0)|, 20 eq. Lys], thus it can be seen that this fluorescent probe can be used to identify and distinguish between different configurations of lysine.

Simultaneous optical tuning of reflection and fluorescence in a self-organized simple 3D cubic structure by α-cyanodiarylethene-based chiral fluorescence photoswitches

A novel optically-tunable BPLC system enabled by an α-cyanodiarylethene fluorescence photoswitch is reported, in which the phototuning of both reflection and fluorescence of BPII with a self-organized simple 3D cubic structure is demonstrated.

Biomimetic Self-Assembled Chiral Inorganic Nanomaterials: A New Strategy for Solving Medical Problems.

The rapid expansion of the study of chiral inorganic structures has led to the extension of the functional boundaries of inorganic materials. Nature-inspired self-assembled chiral inorganic structures exhibit diverse morphologies due to their high assembly efficiency and controlled assembly process, and they exhibit superior inherent properties such as mechanical properties, chiral optical activity, and chiral fluorescence. Although chiral self-assembled inorganic structures are becoming more mature in chiral catalysis and chiral optical regulation, biomedical research is still in its infancy. In this paper, various forms of chiral self-assembled inorganic structures are summarized, which provides a structural starting point for various applications of chiral self-assembly inorganic structures in biomedical fields. Based on the few existing research statuses and mechanism discussions on the chiral self-assembled materials-mediated regulation of cell behavior, molecular probes, and tumor therapy, this paper provides guidance for future chiral self-assembled structures to solve the same or similar medical problems. In the field of chiral photonics, chiral self-assembled structures exhibit a chirality-induced selection effect, while selectivity is exhibited by chiral isomers in the medical field. It is worth considering whether there is some correspondence or juxtaposition between these phenomena. Future chiral self-assembled structures in medicine will focus on the precise treatment of tumors, induction of soft and hard tissue regeneration, explanation of the biochemical mechanisms and processes of its medical effects, and improvement of related theories.

Chiral Fluorescence Recognition by Anthracene Fluorescent Dyes ⊂ Water-Soluble Pillar[5] arene containing Phosphonic Acid Group (PWP[5]).

Chirality plays a pivotal role in drugs, agrochemicals and food additives et al. The enantiomers of a chiral molecule often show huge difference in bioactivity, metabolism, and toxicity et al. thereby, the recognition of chiral molecules shows an increasingly important priority. In this paper, a novel method for chiral fluorescence recognition based on anthracene fluorescent dyes (AD) ⊂ water-soluble pillar[5] arene containing phosphonic acid group (PWP[5]) is developed. The AD as guest molecule can complex with PWP [5] to form 1:1 AD ⊂ PWP[5] assembly, and this assembly can be further used as a fluorescent probe to identify D/L-phenylalanine and D/L-phenylalaninol by fluorescent titration. The fluorescence intensity of the assembly was significantly reduced for D-phenylalanine and D-phenylalaninol, while L-phenylalanine or L-phenylalaninol was added to AD ⊂ PWP[5] assembly, the fluorescence intensity of the assembly almost unchanged. Hence, the chiral recognition based on assembly between the achiral fused ring fluorescent dye and achiral PWP[5] was developed.

A novel chiral fluorescence probe based on carbon dots-copper(II) system for ratio fluorescence detection of gatifloxacin

Up to now, compared to the well-developed researches on chiral nanomaterials, there are relatively few studies focused on chiral Carbon Dots (CDs). The chiral fluorescent probes have properties of high sensitivity and good selectivity, which have attracted extensive attention. Herein, we constructed a chiral fluorescent probe based on a chiral CDs-Copper (II) system, having high photostability and sensitivity, which had the fast dual response of ratiometric fluorescence and enhanced circular dichroism (CD) to gatifloxacin (GAT). This method displayed a linear range of 0.01877–105.1 μg mL−1 with the detection limit of 0.04995 μg mL−1 for GAT under the optimized parameters. It has advantages of good selectivity, wide linear range, convenience and speediness. It was successfully applied to the detection of GAT in serum with satisfactory results. At the same time, the interaction of the chiral probes with chiral or achiral substrates indicates that the chiral CDs as new chiral functional materials have great application potential.

A chiral binaphthyl-based coordination polymer as an enantioselective fluorescence sensor.

A fluorescent, chiral coordination polymer (CP) with a novel topology has been synthesised using a dipyridyl ligand derived from 1,1'-bi-2-naphthol (BINOL). Enantioselectivity ratios up to 2.61 were obtained in fluorescence sensing studies with chiral analytes.

Chiral pillar[n]arenes: Conformation inversion, material preparation and applications

Chiral pillar[n]arenes have shown great research value and application prospect in construction of chiral materials and chiral applications, due to their inherent planar chiral configurations, chiral recognition ability, easy modification and highly symmetric hydrophobic cavity. This review systematically summarized the conformation inversion factors of planar chiral pillar[5]arenes (pR/pS), such as solvents, temperature, substituent size, alkyl chains, chiral and achiral guest molecules. We firstly introduced the applications of chiral pillar[n]arenes for constructing chiral materials and pointed out that planar conformation inversion showed a great potential role in constructing chiral materials. Then, we mainly concluded the chiral applications of chiral and planar chiral pillar[n]arenes like chiral enantiomer analysis by circular dichroism, electrochemistry or chiral fluorescence sensing. From this review, we found that the inherent planar chiral conformation of chiral pillar[n]arenes have played a very important role in chiral field in the future.

A 1,2,3-triazole-based Chiral Fluorescence Sensor for the Sensitive Recognition of Ferric Ion

A chiral fluorescent sensor containing (S)-BINOL and 1, 2, 3-triazole moieties was synthesized via through a nucleophilic substitution reaction and a click reaction with high total yield. The fluorescence responses of chiral compounds W1 and ferric ion were investigated by a fluorescence spectra. The fluorescence emission intensity of W1 at λ = 390 nm (λex = 300 nm) was quenched quickly upon the coordination with a ferric ion while other metal ions had no obvious change.

Circularly Polarized Luminescence of Achiral Metal-Organic Colloids and Guest Molecules in a Vortex Field.

Recently, scientists have reported a range of chiral fluorescence materials or chiral composites that can emit circularly polarized luminescence. Herein, two achiral metal-organic colloidal solutions were studied, showing active circularly polarized luminescence, which is observed in vortex stirring. The absolute values for glum are 0.05 and 0.03 and the plus or minus sign of glum depends on the colloidal structure and stirring direction, which make the property easy to manipulate. Further, the host-guest interaction study suggests both electrostatic interactions and coordination bonding may influence the chiroptical property from the colloidal solution to the guest molecule. Rhodamine 6G and its carboxylic acid derivative exhibit good quantum yields and acceptable glum values in the colloidal solution.

The Progress of Circularly Polarized Luminescence in Chiral Purely Organic Materials

Purely organic circularly polarized luminescent (CPL) materials have attracted much attention owing to their fascinating photophysical properties and potential applications in the fields of optical data storage, smart sensors/probers, high‐resolution 3D display, and so on. With the development of photophysical science, the emergence of some novel emission phenomena, such as thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP), have become hot topics and enriched CPL materials. However, there is no systematic review that summarizes the recent development of chiral small organic molecules (SOMs) with TADF and RTP characters. In this minireview, the progress of purely organic CPL materials in the last 5 years is reviewed by categorizing into chiral fluorescence molecules, chiral TADF molecules, and chiral RTP molecules. Furthermore, the design strategy of chiral TADF emitters is discussed and the correlation between chirality and RTP properties is concluded.

Photoluminescence-enhanced cholesteric films: Coassembling copper nanoclusters with cellulose nanocrystals

Iridescent and luminescent composite films were fabricated through a coassembly strategy, in which glutathione-stabilized copper nanoclusters (GSH-CuNCs) were incorporated into chiral nematic structures of a cellulose nanocrystal (CNC) film. Through variations in the helical pitch, these composite films exhibited broadband reflection. The fluorescence emission spectrum of the composite film exhibited peaks at 439 and 600 nm, corresponding to crystallization-induced emission from CNCs and assembly-induced emission from CuNCs. The enhanced luminescence and prolonged lifetime of the composite film were attributed to the confinement effect of solid layers and attendant intermolecular interactions. By tuning the reaction time, temperature, and pH of the solution, the emission color and intensity of the CuNCs could be changed. At appropriate GSH and Cu2+ concentrations, the chiral organization of GSH-CuNCs enabled the composite CNC film to exhibit right-handed chiral fluorescence with an asymmetry factor of −0.16. Luminescent composite films were employed to fabricate LEDs with custom colors and patterns.