Fluorescent organic nanoparticles based on branched small molecule: preparation and ion detection in lithium-ion battery

Recent Advances in Functional Nanomaterials for Diagnostic and Sensing Using Self-Assembled Monolayers

Functional nanomaterials have attracted attention by producing different structures in any field. These materials have several potential applications, including medicine, electronics, and energy, which provide many unique properties. These nanostructures can be synthesized using various methods, including self-assembly, which can be used for the same applications. This unique nanomaterial is increasingly being used for biological detection due to its unique optical, electrical, and mechanical properties, which provide sensitive and specific sensors for detecting biomolecules such as DNA, RNA, and proteins. This review highlights recent advances in the field and discusses the fabrication and characterization of the corresponding materials, which can be further applied in optical, magnetic, electronic, and sensor fields.

Relay detection of Cu2+ and bovine serum albumin by a dansyl derivative-based fluorescent probe

A dansyl derivative-based fluorescent probe, namely, DGly, was developed for relay detection of Cu²⁺ and bovine serum albumin (BSA) with high selectivity and sensitivity. The fluorescence intensity of DGly at 540 nm displayed "on-off-on" phenomenonafter Cu²⁺ and BSA were added in sequence. Correspondingly, the solution color changed from yellow to dark and then to yellowish white under 365 nm UV light irradiation; thus, the solution could be detected by the naked eye. The association constant of DGly-Cu²⁺ was stronger than that of DGly-BSA and DGly-Cu²⁺-BSA. Hence, BSA was detected after a complex was formed between DGly and Cu²⁺. The relay detection of Cu²⁺ and BSA was not influenced by other competitive interferents, and the detection limits of Cu²⁺ and BSA were 1.32 and 0.26 μM, respectively. Analysis of Cu²⁺ in real water samples validated the detection performance of the method proposed herein; it achieved satisfactory recovery and relative standard deviation values. This work demonstrated that introducing metal ions can be an effective way to improve the sensitivity of BSA detection.

A nano sensor for sensitive and selective detection of Cu2+ based on fluorescein: Cell imaging and drinking water analysis

A fluorescein-based nano probe was designed and synthesized for ultra-sensitive detection of Cu²⁺ in aqueous solution. The formation of fluorescent organic nanoparticles confirmed by using particle size analysis and scanning electron microscopy. UV-Vis. absorption and fluorescence spectroscopy displays excellent photophysical properties of prepared nanoparticles as compared to parent molecule i.e. N-(3',6'-dihydroxy-3-oxo-3,3a-dihydrospiro[isoindole-1,9'-xanthene]-2(7aH)-yl)-1-naphthamide (FNH) in acetone. A series of 18 metal ion was examined with FNH nanoparticles (FNHNPs) to examine the change in fluorescence response. Pleasingly, only copper ion (Cu²⁺) shows selective and sensitive fluorescence enhancement effect, which discussed on chelation-enhanced fluorescence phenomenon. Other competing metal ions does not affect the FNHNPs fluorescence enhancement induced by Cu²⁺ ion. The excited state complexation through chelation-enhanced fluorescence of FNHNPs was further supported by UV-Vis. absorption and fluorescence decay titration of FNHNPs with and without the addition of Cu²⁺. The present investigation approach serves extremely low detection limit of 1.62 ng/mL (0.024 μM) for Cu²⁺ in aqueous solution. In addition, benefit of present study includes practical application for the quantitative estimation of Cu²⁺ in drinking water sample and intracellular cell imaging for Cu²⁺.

Fluorescent organic nanoparticles (FONs) as convenient probes for metal ion detection in aqueous medium

Fluorescent organic nanoparticle (FON)-based chemosensors are emerging as a valuable tool for the fast and accurate detection of metal ions in aqueous media. In this review, we highlight the recent developments in this field.

A new red fluorophore with aggregation enhanced emission by an unexpected “One-step” protocol

In this work, a triphenylamine-benzothiadiazole-based new fluorophore is obtained from a facile “one-step” protocol. A possible reduction mechanism is proposed, and an amine containing α-H plays a key role in the reduction reaction. The resultant product A1H2 exhibits bright red emission in solid state, with an absolute quantum yield of 44.5%. Aggregation induced emission enhancement of A1H2 is also observed with the increased water fraction in THF-H₂O mixture. The nanoparticles of A1H2 reveal good stability and biocompatibility, which are successfully applied in cellular cytoplasm imaging.

Compound A1H2 was synthesized via the reductive Knoevenagel alkylation, whose nanoparticles exhibit bright red emission in aqueous solution.

Continuous Fluorescence Imaging of Intracellular Calcium by Use of Ion-Selective Nanospheres with Adjustable Spectra

Continuous fluorescence imaging of intracellular ions in various spectral ranges is important for biological studies. In this paper, fluorescent calcium-selective nanospheres, including calix[4]arene-functionalized bodipy (CBDP) or 9-(diethylamino)-5-[(2-octyldecyl)imino]benzo[a]phenoxazine (ETH 5350) as the chromoionophore, were prepared to demonstrate intracellular calcium imaging in visible or near-IR regions, respectively. The fluorescence of the nanospheres was controlled by the chromoionophore, and thus the spectral range for detection was adjustable by choosing the proper chromoionophore. The response time of the nanospheres to calcium was typically 1 s, which allowed accurate measurement of intracellular calcium. These nanospheres were loaded into cells through free endocytosis and exhibited fluorescence for 24 h, and their intensity was correlated with the elevation of intracellular calcium upon stimulation. The successful demonstration of calcium imaging by use of ion-selective nanospheres within two spectral ranges in 24 h supported that these nanospheres could be applied for continuous imaging of intracellular ions with adjustable spectra.

Self-Assembly of Fluorescent Organic Nanoparticles for Iron(III) Sensing and Cellular Imaging

Fluorescent organic nanoparticles have attracted increasing attentions for chemical or biological sensing and imaging due to their low-toxicity, facile fabrication and surface functionalization. In this work, we report novel fluorescent organic nanoparticles via facile self-assembly method in aqueous solution. First, the designed water-soluble fluorophore shows a weak and negligible intrinsic fluorescence in water. Upon binding with adenosine-5'-triphosphate (ATP), fluorescent nanoparticles were formed immediately with strongly enhanced fluorescence. These fluorescent nanoparticles exhibit high sensitivity and selectivity toward Fe(3+) sensing with detection limit of 0.1 nM. In addition, after incubation with HeLa cells, the fluorophore shows excellent imaging performance by interaction with entogenous ATP in cells. Finally, this fluorescent system is also demonstrated to be capable of Fe(3+) sensing via fluorescence quenching in cellular environment.

Facile Synthesis of Biocompatible Fluorescent Nanoparticles for Cellular Imaging and Targeted Detection of Cancer Cells

In this work, we report the facile synthesis of functional core-shell structured nanoparticles with fluorescence enhancement, which show specific targeting of cancer cells. Biopolymer poly-l-lysine was used to coat the silver core with various shell thicknesses. Then, the nanoparticles were functionalized with folic acid as a targeting agent for folic acid receptor. The metal-enhanced fluorescence effect was observed when the fluorophore (5-(and-6)-carboxyfluorescein-succinimidyl ester) was conjugated to the modified nanoparticle surface. Cellular imaging assay of the nanoparticles in folic acid receptor-positive cancer cells showed their excellent biocompatibility and selectivity. The as-prepared functional nanoparticles demonstrate the efficiency of the metal-enhanced fluorescence effect and provide an alternative approach for the cellular imaging and targeting of cancer cells.

Fluorescence resonance energy transfer in a binary organic nanoparticle system and its application

Fluorescent organic nanoparticles have a much better photostability than molecule-based probes. Here, we report a simple strategy to detect chemicals and biomolecules by a binary nanoparticle system based on fluorescence resonance energy transfer (FRET). Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO, energy donor) and poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, energy acceptor) are utilized to prepare the binary nanoparticle system through a reprecipitation method. Since the FRET process is strongly distance-dependent, a change in the interparticle distance between the two kinds of nanoparticles after introduction of analytes will alter the FRET efficiency. The response of the binary nanoparticle system to cationic polyelectrolytes was investigated by monitoring the FRET efficiency from PFO to MEH-PPV nanoparticles and the fluorescence color of the nanoparticle solutions. Furthermore, the cationic polyelectrolyte pretreated binary nanoparticle system can be used to detect DNA by desorption of nanoparticles from the polyelectrolyte's chains and the detection concentration can go down to 10(-14) M. Thus, the binary nanoparticle system shows great promise for applications in chemical sensing or biosensing.

A novel graphene oxide-based fluorescent nanosensor for selective detection of Fe(3+) with a wide linear concentration and its application in logic gate

A graphene oxide-based fluorescent nanosensor AGO has been designed and synthesized by covalent grafting allylamine onto GO surface. In aqueous media, AGO displays a highly selective and sensitive discrimination of Fe(3+) from Fe(2+) and other metal ions through electron transfer-induced fluorescence quenching. The quenching of AGO fluorescence is linearly proportional to Fe(3+) concentration in a wide range of 0-120 μM (correlation coefficient R(2)=0.9994). Moreover, AGO can be used to construct a combinational three-input logic gate to discriminate Fe(3+) and Fe(2+). The logic gate works well in intracellular fluorescence imaging, which shows a potential as a promising platform for biosensing analysis.

A catalytic chemodosimetric approach for detection of nanomolar cyanide ions in water, blood serum and live cell imaging

The nano-molar detection of cyanide in live cell imaging and blood serum has been achieved through cyanide catalysed fluorescence enhancement with a TON between 70 and 360.

Nanoparticles made of π-conjugated compounds targeted for chemical and biological applications

This feature article summarizes the recent applications of nanoparticles made of π-conjugated compounds in bio/chemo-sensing, disease therapy, and photoacoustic imaging.

Fluorescent organic nanoparticles with enhanced fluorescence by self-aggregation and their application to cellular imaging

We report a simple strategy to prepare organic biocompatible fluorescent nanoparticles with enhanced fluorescence. A significant fluorescence enhancement was realized by designing a fluorescent small molecule, 4,4'-(2,7-bis[4-{1,2,2-triphenylvinyl}phenyl]-9H-fluorene-9,9-diyl)bis(N,N,N-trimethylbutan-1-aminum)bromide (TPEFN), with aggregation-induced emission enhancement (AIEE) effect. Nanoparticles of TPEFN can be formed through molecular self-aggregation by gradually increasing the water fraction in TPEFN mixed solution (methanol/water). Fluorescence enhancement by about 120-fold was observed after nanoparticle formation. By addition of the biomolecule adenosine triphosphate (ATP), larger nanoparticles of TPEFN are formed and further fluorescence enhancement can be achieved, yielding a total fluorescence enhancement of 420-fold compared with the TPEFN molecular solution. Both of these nanoparticles show very good biocompatibility. Ultrabright spots present in the confocal laser scanning microscopy image again proved the formation of nanoparticles. Positively charged side chains of TPEFN endow these nanoparticles cationic surfaces. The size of the prepared TPEFN nanoparticles and their cationic surface allow them to be rapidly internalized into cells. Cell viability assays prove that the TPEFN nanoparticles have high biocompatibility. These organic fluorescent nanoparticles show great promise for applications in cellular imaging or biotechnology.

Hybrid silver nanoparticle/conjugated polyelectrolyte nanocomposites exhibiting controllable metal-enhanced fluorescence

Metal-enhanced fluorescence of conjugated polyelectrolytes (CPs) is realized using a simple, green hybrid Ag nanocomposite film. Ag nanoparticles (Ag NPs) are pre-prepared by sodium citrate reduction and incorporated into agarose by mixing to form an Ag-containing agarose film (Ag@agarose). Through variation of the amount of Ag NPs in the Ag@agarose film as well as the thickness of the interlayer between CPs and the Ag@agarose film prepared of layer-by-layer assembly of chitosan and sodium alginate, a maximum 8.5-fold increase in the fluorescence of CPs is obtained. After introducing tyrosinase, this system also can be used to detect phenolic compounds with high sensitivity and good visualization under ultraviolet light.

Citrate-induced aggregation of conjugated polyelectrolytes for Al(3+)-ion-sensing assays

This work shows the sodium citrate induced efficient interpolymer π-stacking aggregation of the planar cationic conjugated polyelectrolyte poly[{9,9-bis[6'-(N,N-trimethylamino)hexyl]-2,7-fluorenyleneethynylene}-alt-co-(1,4-phenylene)] dibromide (PFE) in aqueous solution, which results in the self-quenching of fluorescence. Using the citrate-induced aggregation properties of PFE and the strong chelation ability of citrate with aluminum ions (Al(3+)), a sensitive and selective Al(3+)-ion detection assay in aqueous solution was developed through monitoring of the fluorescence recovery of PFE. The fluorescence intensity recovery of PFE depends on the concentration of Al(3+) ions, and linear fluorescence recovery was observed in the range of 0.5-9 μM. The limit of detection of this assay is 0.37 μM. Its simplicity and rapidity mean this assay shows promise for the real-time detection of Al(3+).