An integrated logic system for time-resolved fluorescent "turn-on" detection of cysteine and histidine base on terbium (III) coordination polymer-copper (II) ensemble

Aggregation-induced emission enhancement of gold nanoclusters triggered by sodium heparin and its application in the detection of sodium heparin and alkaline amino acids

This work first reported that sodium heparin could cause the aggregation-induced emission enhancement (AIEE) effect of GSH-AuNCs (Glutathione functionalized gold nanoclusters). While it was interestingly found that the addition of alkaline amino acids would greatly weaken this effect. Thus, fluorescent system was designed for the quantitative detection of sodium heparin and alkaline amino acids. Negatively charged sodium heparin would connect with GSH-AuNCs through electrostatic attraction, leading to a significant AIEE effect. Then alkaline amino acids would competitively bind with sodium heparin, causing this effect to almost disappear. The reasons were as follows: (I) The hydrogen bonding between sodium heparin and alkaline amino acids was much stronger than electrostatic force, causing GSH-AuNCs to be competitively replaced. (II) Alkaline amino acids and GSH-AuNCs were both positively charged and repelled each other. The presence of alkaline amino acids would hinder the AIEE effect. (III) AIEE effect was confirmed to have a close relationship with the pH value which could be greatly affected by alkaline amino acids. (Ⅳ) Not only the hydrogen bonding, the electrostatic force also existed between the alkaline amino acids and sodium heparin. All the above reasons worked together to weaken the AIEE effect of GSH-AuNCs triggered by sodium heparin. Finally, both sodium heparin and alkaline amino acids were accurately detected, showing good correlation coefficients of 0.99 with the LODs of 0.0100 mg/mL (sodium heparin), 1.05 μM (histidine), 3.38 μM (arginine) and 6.16 μM (lysine), respectively.

BSA Capped gold Nanoclusters Modulated by Copper ion for Sensitive and Selective Detection of Histidine in Biological Fluid

This research proposed a sample and environmentally sustainable technique for the synthesis of bovine serum albumin capped gold nanoclusters (BSA-AuNCs) with outstanding fluorescence. The synthesized BSA-AuNCs were investigated using various ways before being combined with Cu2+ to produce a fluorescent switch probe (BSA-AuNCs-Cu2+) for histidine determination. After adding Cu2+, the fluorescence of the BSA-AuNCs was quenched, the fluorescence intensity was enhanced after adding histidine due to good coordination between Cu2+ and histidine. The significant chelation of histidine with Cu2+ demonstrated the viability of developing a selective "switch on" probe for histidine detecting over other amino acids. Unlike existing fluorescent nanomaterial-based approaches for detecting histidine, this study promises good selectivity, high efficiency, and the avoiding of chemical solvents. The designed BSA-AuNCs-Cu2+ fluorescent probe demonstrated an acceptable linear detection range of 0 to 240 µM under optimum circumstances, with a detection limit of 0.9 µM. The BSA-AuNCs-Cu2+ system was investigated in rat serum and human urine, with recoveries ranging from 97.2 to 108.2%, demonstrating its potential applicability for histidine detection with favorable results.

A neutral mononuclear rhenium(I) complex with a rare in situ-generated triazolyl ligand for the luminescence "turn-on" detection of histidine

A rare in situ-generated mononuclear rhenium complex [Re(bpt)(CO)₃(NH₃)] (1, bpt = 3,5-bis(2-pyridyl)-1,2,4-triazolate) can be used as a "turn-on" luminescent probe for selectively sensing L-histidine against other amino acids. Compound 1 was prepared by reacting Re₂(CO)₁₀, 2-cyanopyridine and hydrazine with an in situ formed bpt ligand through cyclization via C-N and N-N couplings with its single-side chelating mode arrayed with respect to the Re center. Compound 1 was highly stable and showed a green light MLCT emission in DMF solution at 507 nm upon excitation at 360 nm. Interestingly, the emission from 1 could be quenched by the addition of metal ions such as Ni²⁺ and Cu²⁺ but the emission efficiently recovered with the introduction of histidine. However, histidine could only be selectively detected when a combination of compound 1 and Ni²⁺ was used. Therefore, the luminescence response of the Ni²⁺-modified compound 1 could be utilized as a "turn-on" probe for the selective detection of histidine. This work provides a simple method for developing new sensing platforms of a discrete metal complex based on rare in situ generation.

Stable bifunctional ZnII-based sensor toward acetylacetone and L-histidine by fluorescence red shift and turn-on effect

A new coordination polymer [Zn(bbip)(NH2-BDC)]n (JXUST-15, bbip = 2,6-bis(benzimidazol-1-yl)pyridine and NH2-H2BDC = 2-aminoterephthalic acid) has been synthesized by mixed ligand strategy. The structure analysis shows that JXUST-15 takes a two-dimensional...

Histidine-Tagged Folate-Targeted Gold Nanoparticles for Enhanced Transgene Expression in Breast Cancer Cells In Vitro

Nanotechnology has emerged as a promising treatment strategy in gene therapy, especially against diseases such as cancer. Gold nanoparticles (AuNPs) are regarded as favorable gene delivery vehicles due to their low toxicity, ease of synthesis and ability to be functionalized. This study aimed to prepare functionalized AuNPs (FAuNPs) and evaluate their folate-targeted and nontargeted pCMV-Luc-DNA delivery in breast cancer cells in vitro. CS was added to induce stability and positive charges to the AuNPs (Au-CS), histidine (Au-CS-His) to enhance endosomal escape and folic acid for folate-receptor targeting (Au-CS-FA-His). The FAuNP:pDNA nanocomplexes possessed favorable sizes (<135 nm) and zeta potentials (<-20 mV), strong compaction efficiency and were capable of pDNA protection against nuclease degradation. These nanocomplexes showed minimal cytotoxicity (>73% cell viability) and enhanced transgene activity. The influence of His was notable in the HER2 overexpressing SKBR3 cells, which produced higher gene expression. Furthermore, the FA-targeted nanocomplexes enhanced receptor-mediated endocytosis, especially in MCF-7 cells, as confirmed by the receptor competition assay. While the role of His may need further optimization, the results achieved suggest that these FAuNPs may be suitable gene delivery vehicles for breast cancer therapeutics.

Metal-Bridged Graphene-Protein Supraparticles for Analog and Digital Nitric Oxide Sensing

Self-limited nanoassemblies, such as supraparticles (SPs), can be made from virtually any nanoscale components, but SPs from nanocarbons including graphene quantum dots (GQDs), are hardly known because of the weak van der Waals attraction between them. Here it is shown that highly uniform SPs from GQDs can be successfully assembled when the components are bridged by Tb³⁺ ions supplementing van der Waals interactions. Furthermore, they can be coassembled with superoxide dismutase, which also has weak attraction to GQDs. Tight structural integration of multilevel components into SPs enables efficient transfer of excitonic energy from GQDs and protein to Tb³⁺ . This mechanism is activated when Cu²⁺ is reduced to Cu¹⁺ by nitric oxide (NO)-an important biomarker for viral pulmonary infections and Alzheimer's disease. Due to multipronged fluorescence enhancement, the limit of NO detection improves 200 times reaching 10 × 10^-12 m. Furthermore, the uniform size of SPs enables digitization of the NO detection using the single particle detection format resulting in confident registration of as few as 600 molecules mL^-1 . The practicality of the SP-based assay is demonstrated by the successful monitoring of NO in human breath. The biocompatible SPs combining proteins, carbonaceous nanostructures, and ionic components provide a general path for engineering uniquely sensitive assays for noninvasive tracking of infections and other diseases.

Simple fluorescence optosensing probe for spermine based on ciprofloxacin-Tb3+ complexation

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2-180 μM with a low limit of detection of 0.17 μM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results.

Rapid microwave-assisted green synthesis of guanine-derived carbon dots for highly selective detection of Ag+ in aqueous solution

In this work, a simple and green synthetic approach of novel guanine decorated carbon dots (G-CDs) using guanosine 5'-monophosphate and ethylenediamine through a domestic microwave oven was established for the first time. The as-prepared fluorescent G-CDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and fluorescence spectroscopy. The obtained fluorescent G-CDs with a uniform morphology had desirable functional groups and excellent optical performances. Furthermore, the fluorescence intensity of G-CDs was remarkably quenched by Ag⁺ than that of other nucleotides-derived CDs. The density functional theory calculations were performed to confirm that the strong interaction of guanine-Ag⁺ was responsible for the remarkable fluorescence response of G-CDs towards Ag⁺. In addition, as a label-free fluorescence probe, the G-CDs displayed a good linear detection for highly selective Ag⁺ sensing over the range of 0-80 μM with the low detection limit of 90 nM. Therefore, the proposed G-CDs had the capacity for Ag⁺ detection in the real samples.

Bioinspired pyrimidine-containing cationic polymers as effective nanocarriers for DNA and protein delivery

Cationic polymers have shown great potential in the delivery of nucleic acids and proteins. In this study, a series of pyrimidine-based cationic polymers were synthesized via the Michael addition reaction from pyrimidine-based linkages and low molecular weight polyethyleneimine (PEI). The structure-activity relationship (SAR) of these materials in DNA and protein delivery was investigated. These materials could condense both DNA and protein into nanoparticles with proper sizes and zeta-potentials. In vitro experiments indicated that such polymers were efficient in transporting DNA and proteins into cells. Furthermore, the bioactivity of the genes and proteins encapsulated in these polymers were maintained during the delivery processes. Among the polymers, U-PEI600 synthesized from a uracil-containing linker and PEI 600 Da mediated comparable gene expression to PEI 25 kDa. Moreover, the activities of β-galactosidase delivered by U-PEI600 were well maintained after entering the cells. Evaluation using an immune response assay showed that the U-PEI600/OVA polyplex could stimulate greater production of immune factors with low cytotoxicity. Our study provides a strategy for the construction of cationic polymeric gene and cytosolic protein vectors with high efficiency and low toxicity.

Spiropyran-modified upconversion nanocomposite as a fluorescent sensor for diagnosis of histidinemia

Histidinemia is a congenital metabolic disorder where the histidine (His) metabolism is blocked, resulting in increased concentrations of His in blood and urine. The disease causes an abnormal development of the patient's nervous system, which leads to many serious illnesses. Therefore, it is very important to diagnose early. In this study, we developed a novel fluorescent nanosensor NaGdF₄:Yb³⁺, Er³⁺@SiO₂–spiropyran (UCNP@SiO₂–SP). The nanosensor displayed a “turn-off” fluorescence response towards His. When His was mixed with UCNP@SiO₂–SP, His could specifically bind to SP, which could cause the isomerization of SP. The structure of SP was changed from spiroform into merocyanine form. The luminescence of the sensor was overlapped with the absorption of the merocyanine form. As a result, His will lead to fluorescence quenching of the sensor based on inner filter effects (IFE), which can be used to detect His. Importantly, as the first report of a UCNP@SiO₂–SP nanosensor for detecting His, this method exhibits good selectivity and anti-interference capability. The detection limit is 4.4 μM. In addition, the amount of His in urine was also measured, suggesting the applicability of this sensor for histidinemia diagnosis.

A novel sensor based on upconversion fluorescent nanoparticles was developed and used to diagnose histidinemia.

Coordination polymers of Tb3+/Nucleotide as smart chemical nose/tongue toward pattern-recognition-based and time-resolved fluorescence sensing

The abundant functional groups on guanosine monophosphate (GMP) make it possible to interact with various metal ions. The subtle difference in the structure of GMP and deoxy-guanosine monophosphate (dGMP) coupled with Tb3+ can be readily exploited to form two coordination polymers, which have been unveiled as two time-resolved fluorescence (TRF) sensing reporters (Tb-GMP and Tb-dGMP) in our study. Based on this finding, herein, we have proposed a novel TRF orthogonal sensing array (Tb-GMP/dGMP) for pattern-recognition-based sensing of various metal ions. In addition, upon integration of some thiol-affinity metal ions, Tb-GMP/dGMP can be further extended to construct two metal ion-involved pattern-recognition-based sensor arrays (Tb-GMP/dGMP-Cu, Tb-GMP/dGMP-Ag) for the TRF sensing different levels of disease-relevant biothiols in biofluids, illustrating the powerful and multifunctional capabilities of the Tb-GMP/dGMP system and would inspire simpler and more widespread designs of chemical nose/tongue-based applications.

Fluorescence assay for alkaline phosphatase activity based on energy transfer from terbium to europium in lanthanide coordination polymer nanoparticles

An effective fluorescence assay alkaline phosphatase (ALP) method was developed by using bimetallic lanthanide coordination polymer nanoparticles (Tb-GMP-Eu CPNs).

Aggregation-induced emission of luminol: a novel strategy for fluorescence ratiometric detection of ALP and As(v) with high sensitivity and selectivity

Luminol is introduced as a ligand for Tb³⁺ which, combined with GMP, leads to a sensor which is more robust, sensitive, and efficient.

Nucleobases, nucleosides, and nucleotides: versatile biomolecules for generating functional nanomaterials

The incorporation of biomolecules into nanomaterials generates functional nanosystems with novel and advanced properties, presenting great potential for applications in various fields. Nucleobases, nucleosides and nucleotides, as building blocks of nucleic acids and biological coenzymes, constitute necessary components of the foundation of life. In recent years, as versatile biomolecules for the construction or regulation of functional nanomaterials, they have stimulated interest in researchers, due to their unique properties such as structural diversity, multiplex binding sites, self-assembly ability, stability, biocompatibility, and chirality. In this review, strategies for the synthesis of nanomaterials and the regulation of their morphologies and functions using nucleobases, nucleosides, and nucleotides as building blocks, templates or modulators are summarized alongside selected applications. The diverse applications range from sensing, bioimaging, and drug delivery to mimicking light-harvesting antenna, the construction of logic gates, and beyond. Furthermore, some perspectives and challenges in this emerging field are proposed. This review is directed toward the broader scientific community interested in biomolecule-based functional nanomaterials.

Terbium (III) coordination polymer-copper (II) compound as fluorescent probe for time-resolved fluorescence 'turn-on' detection of hydrogen sulfide

With recognition of the biological importance of hydrogen sulfide (H₂ S), we present a simple and effective fluorescent probe for H₂ S using a Tb³⁺ coordination polymer-Cu²⁺ compound (DPA/Tb/G-Cu²⁺ ). Dipicolinic acid (DPA) and guanosine (G) can coordinate with Tb³⁺ to form a macromolecular coordination polymer (DPA/Tb/G). DPA/Tb/G specifically binds to Cu²⁺ in the presence of coexisting cations, and obvious fluorescence quenching is observed. The quenched fluorescence can be exclusively recovered upon the addition of sulfide, which is measured in the mode of time-resolved fluorescence. The fluorescence intensities of the DPA/Tb/G-Cu²⁺ compound enhance linearly with increasing sulfide concentrations from 1 to 30 μM. The detection limit for sulfide in aqueous solution is estimated to be 0.3 μM (at 3σ). The DPA/Tb/G-Cu²⁺ compound was successfully applied to sense H₂ S in human serum samples and exhibited a satisfactory result. It displays some desirable properties, such as fast detection procedure, high selectivity and excellent sensitivity. This method is very promising to be utilized for practical detection of H₂ S in biological and environmental samples.

Acriflavine-immobilized eggshell membrane as a new solid-state biosensor for Sudan I-IV detection based on fluorescence resonance energy transfer

A novel solid-surface fluorescence biosensor for rapid detection of Sudan I-IV was proposed based on fluorescence resonance energy transfer (FRET). The biosensor was fabricated by immobilizing acriflavine (AY) on the eggshell membrane (ESM) with glutaraldehyde as cross-linking agent. FRET mechanism was demonstrated by using AY and Sudan dyes as donor and acceptor respectively, an efficient energy transfer in the present system was indicated by the sufficient spectral overlap integral (J) and proper Förster critical distance (R₀). Under optimum conditions, the fluorescence of the AY-ESM could be efficiently quenched by Sudan I-IV and the corresponding linear range was 0.5-60μM with the detection limits (3σ/slope) of 0.16, 0.26, 0.21 and 0.17μM respectively. Compared to the detection of Sudan dyes in solution-state, the membrane biosensor exhibited advantages of low detection limits, high sensitivity and selectivity, as well as excellent stability. Recovery tests in spiked real samples also achieved satisfactory results.

Ratiometric fluorescence monitoring of cerebral Cu2+ based on coumarin-labeled DNA coupled with the Cu2+-induced oxidation of o-phenylenediamine

A novel ratiometric fluorescence assay for cerebral Cu²⁺ has been developed based on coumarin-labeled single-stranded DNA coupled with the Cu²⁺-induced oxidation of o-phenylenediamine.

Lanthanide coordination polymer nanoparticles as a turn-on fluorescence sensing platform for simultaneous detection of histidine and cysteine

A turn-on fluorescent sensor for simultaneous detection of histidine and cysteine based on lanthanide coordination polymer nanoparticles.