Exploring Novel Sensor Design Ideas through Concentration-Induced Conformational Changes in PEG Single Chains

Polyethylene glycol (PEG) is an artificial polymer with good biocompatibility and a low cost, which has a wide range of applications. In this study, the dynamic response of PEG single chains to different ion concentrations was investigated from a microscopic point of view based on single-molecule force spectroscopy, revealing unique interactions that go beyond the traditional sensor-design paradigm. Under low concentrations of potassium chloride, PEG single chains exhibit a gradual reduction in rigidity, while, conversely, high concentrations induce a progressive increase in rigidity. This dichotomy serves as the cornerstone for a profound understanding of PEG conformational dynamics under diverse ion environments. Capitalizing on the remarkable sensitivity of PEG single chains to ion concentration shifts, we introduce innovative sensor-design ideas. Rooted in the adaptive nature of PEG single chains, these sensor designs extend beyond the traditional applications, promising advancements in environmental monitoring, healthcare, and materials science.

BODIPY-GO nanocomposites decorated with a biocompatible branched ethylene glycol moiety for targeted PDT

The properties of graphene oxide (GO) have received much attention and been applied to the exploration of potential applications in disease-related diagnostics and non-invasive therapy. One application, photodynamic therapy (PDT), involves the killing of cancer cells where singlet oxygen is generated with light irradiation of the appropriate wavelength. In this work, three new BODIPY derivatives (13-15), decorated with carbohydrate moieties for active targeting and branched ethylene glycol for biocompatibility, and their GO based nanocarriers were designed to study the singlet oxygen production and PDT efficiency. First, BODIPYs were prepared, followed by the fabrication of GO layers with BODIPY dyes via a non-covalent method. Detailed characterizations of the materials were carried out with mass spectrometry, FT-IR spectroscopy, ¹H NMR, ¹³C NMR, elemental analysis, Raman spectroscopies, EDX analysis and TEM and AFM microscopies. The efficiency of singlet oxygen generation in organic and water-based solutions was determined by photobleaching with 1,3-diphenylisobenzofuran (DPBF) and 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA), respectively. The results in in vitro PDT analysis against K562 human cancer cells indicate the prepared materials are highly promising in PDT anticancer therapy and the IC₅₀ values of GO loaded BODIPY derivatives bearing heavy atoms, GO-14 and GO-15, were calculated as 40.59 nM and 39.21 nM, respectively.

Bioluminescence Color-Tuning Firefly Luciferases: Engineering and Prospects for Real-Time Intracellular pH Imaging and Heavy Metal Biosensing

Firefly luciferases catalyze the efficient production of yellow-green light under normal physiological conditions, having been extensively used for bioanalytical purposes for over 5 decades. Under acidic conditions, high temperatures and the presence of heavy metals, they produce red light, a property that is called pH-sensitivity or pH-dependency. Despite the demand for physiological intracellular biosensors for pH and heavy metals, firefly luciferase pH and metal sensitivities were considered drawbacks in analytical assays. We first demonstrated that firefly luciferases and their pH and metal sensitivities can be harnessed to estimate intracellular pH variations and toxic metal concentrations through ratiometric analysis. Using Macrolampis sp2 firefly luciferase, the intracellular pH could be ratiometrically estimated in bacteria and then in mammalian cells. The luciferases of Macrolampis sp2 and Cratomorphus distinctus fireflies were also harnessed to ratiometrically estimate zinc, mercury and other toxic metal concentrations in the micromolar range. The temperature was also ratiometrically estimated using firefly luciferases. The identification and engineering of metal-binding sites have allowed the development of novel luciferases that are more specific to certain metals. The luciferase of the Amydetes viviani firefly was selected for its special sensitivity to cadmium and mercury, and for its stability at higher temperatures. These color-tuning luciferases can potentially be used with smartphones for hands-on field analysis of water contamination and biochemistry teaching assays. Thus, firefly luciferases are novel color-tuning sensors for intracellular pH and toxic metals. Furthermore, a single luciferase gene is potentially useful as a dual bioluminescent reporter to simultaneously report intracellular ATP and/or luciferase concentrations luminometrically, and pH or metal concentrations ratiometrically, providing a useful tool for real-time imaging of intracellular dynamics and stress.

Fluorescent chitosan-BODIPY macromolecular chemosensors for detection and removal of Hg2+ and Fe3+ ions

The detection of heavy metals, such as Hg2+ and Fe3+, is of great significance. In this work, fluorescent small-molecule BODIPY (BY-3) bearing CC group was synthesized firstly. And then, the chitosan-based polymer sensor CY-1 was synthesized through the spontaneous NH2/C≡C click reaction. The synthesized CY-1 can effectively bind and recognize Hg2+/Hg+ by the -C=N groups formed in the click reaction. Moreover, the macromolecular sensors CS-1 and CS-2 were synthesized by incorporating another recognition sites to CY-1. These synthesized macromolecular sensors can not only recognize Hg2+/Hg+, but also effectively recognize Fe3+/Fe2+. All of them exhibited significant quenching effect, visible to the naked eye under UV irradiation. The detection limit of CY-1 for Hg2+ was 1.51 × 10-6 mol/L, and the detection limit of CS-2 for Fe3+ was 2.30 × 10-6 mol/L. The BODIPY-chitosan sensors synthesized in this work have the functions of removing heavy metal ions besides the identifying ability. The maximum adsorption capacity of 1 g chitosan to Hg2+ was 108 mg as the best one. This article provides a new method to prepare macromolecular sensors for the detection and removal of heavy metal ions. As a useful natural polymer, chitosan's application scope was enlarged.

An efficient chemodosimeter for the detection of Hg(II) via diselenide oxidation

Mercury ions are toxic and exhibit hazardous effects on the environment and biological systems, and thus demand for the selective and sensitive detection of mercury has become considerably an important issue. Here, we have developed a diselenide containing coumarin-based probe 3 for the selective detection of Hg(II) with a "turn-on" response (a 48 fold increase in fluorescence intensity) at 438 nm. The probe could quantitatively detect Hg(II) with a detection limit of 1.32 μM in PBS solution. Moreover, the probe has operable efficiency over the physiological range with an increase in the quantum yield from 1.2% to 57.3%. The reaction of the probe with Hg(II) yielded a novel monoselenide based coumarin 4via diselenide oxidation, which was confirmed by single crystal XRD. Furthermore, the biological use of the probe for the detection of Hg(II) was confirmed in the MCF-7 cell line. To the best of our knowledge, this is the first reaction-based probe for Hg(II) via diselenide oxidation.

Boron dipyrromethene (BODIPY) in polymer chemistry

The present review provides both a summary and outlook on the exciting field of BODIPYs in polymer chemistry.

Advances on Water Quality Detection by UV-Vis Spectroscopy

Water resources are closely linked to human productivity and life. Owing to the deteriorating water resources environment, accurate and rapid determination of the main water quality parameters has become a current research hotspot. Ultraviolet-visible (UV-Vis) spectroscopy offers an effective tool for qualitative analysis and quantitative detection of contaminants in a water environment. In this review, the principle and application of UV-Vis technology in water quality detection were studied. The principle of UV-Vis spectroscopy for detecting water quality parameters and the method of modeling and analysis of spectral data were presented. Various UV-Vis technologies for water quality detection were reviewed according to the types of pollutants, such as chemical oxygen demand, heavy metal ions, nitrate nitrogen, and dissolved organic carbon. Finally, the future development of UV-Vis spectroscopy for the determination of water quality was discussed.

Recent developments in dipyrrin based metal complexes: Self-assembled nanoarchitectures and materials applications

While dipyrrin-boron complexes (BODIPYs) and their derivatives have attracted much attention, dipyrrin-based metal complexes recently appeared as a novel luminescent material. So far, dipyrrin-metal complexes have been regarded as non-luminescent or weakly luminescent. Interestingly, introduction of steric hindrance at the meso-position and the development of heteroleptic complexes with proper frontier orbital ordering are two recent strategies that have been developed to improve their luminescent ability. Compared with BODIPYs, one of the distinctive advantages of dipyrrin-metal complexes is that they can form a series of self-assembled supramolecules and polymer assemblies via facile coordination reactions. In recent times, several supramolecular, coordination polymers and Metal-Organic Frameworks (MOFs) have been developed, [Formula: see text] by spontaneous coordination reactions between dipyrrin ligands and metal ions. As a novel luminescent material, dipyrrin-metal complexes have been applied in many fields. This review article summarizes recent developments in dipyrrin-metal complexes from the viewpoint of the improvement of luminescent ability, the formation of supramolecular and coordination polymers and their potential applications.

Syntheses, characterization, multi-acid fluorescence sensing and electroluminescence properties of Cr(ii)-based metallopolymers

Cr(ii)-Based multifunctional fluorescent metallopolymers with different degrees of backbone rigidity were synthesized and applied as multi-acid sensors and electroluminescent ON–OFF switches.

Long-Wavelength Fluorescent Chemosensors for Hg2+ based on Pyrene

A novel long-wavelength turn-on fluorescent chemosensor CS based on pyrene was synthesized to detect Hg²⁺. In the presence of other metal ions, CS could effectively recognize Hg²⁺ and produce the turn-on fluorescent emission at 607 nm. Also, the absorption spectrum exhibited red-shift. Meanwhile, the change of the solution color from yellow to orange was directly observed by the naked eye. The interaction between CS and Hg²⁺ was confirmed by the Job's plot, electrospray ionization mass spectrometry, scanning electron microscopy, and density functional theory calculations. It was found that the fluorescence of CS could be reversible when I^- was added into the solution of CS and Hg²⁺. CS illustrated high selectivity and good sensitivity for Hg²⁺ with the limit of detection of 36 nm. Moreover, CS could be utilized as test strips and silica gel plates to identify Hg²⁺.

BODIPY-Derived Polymeric Chemosensor Appended with Thiosemicarbazone Units for the Simultaneous Detection and Separation of Hg(II) Ions in Pure Aqueous Media

Developing a simple and cheap analytical method for the selective detection and quantitative separation of toxic ions present in aqueous media is the biggest challenge faced by the chemosensing research community. Here, a 5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-derived water-soluble polymer integrated with thiosemicarbazone units was rationally designed and synthesized for the simultaneous detection and separation of Hg(II) ions in pure aqueous solution. The water-soluble polymer scaffold poly( N, N'-dimethyl acrylamide- co-5,5-difluoro-1,3,7,9-tetramethyl-10-phenyl-5 H-dipyrrolo-diazaborinine-2-carbaldehyde) was synthesized by reversible addition-fragmentation chain transfer polymerization, followed by post-polymerization modification with thiosemicarbazide, leading to the formation of the target probe, P1. The nonemitting P1 exhibited bright yellow emission upon exposure to Hg(II) ions, with a limit of detection as low as 0.37 μM. This turn-on emission behavior triggered by Hg(II) ions might originate from the suppression of isomerization around the C═N bond of the thiosemicarbazone moiety caused by the formation of a coordination complex between P1 and Hg(II) ions. In addition, P1 displayed excellent selectivity toward Hg(II) ions over other metal cations. Finally, the selective removal of Hg(II) ions from an aqueous solution containing various metal ions was achieved by precipitation, which is probably caused by the fact that coordination complexes whereby Hg(II) ions acted as bridgeheads between P1 molecules had formed.

A Highly Selective Turn-on and Reversible Fluorescent Chemosensor for Al3+ Detection Based on Novel Salicylidene Schiff Base-Terminated PEG in Pure Aqueous Solution

The development of highly selective and sensitive chemosensors for Al³⁺ detection in pure aqueous solution is still a significant challenge. In this work, a novel water-soluble polymer PEGBAB based on salicylidene Schiff base has been designed and synthesized as a turn-on fluorescent chemosensor for the detection of Al³⁺ in 100% aqueous solution. PEGBAB exhibited high sensitivity and selectivity to Al³⁺ over other competitive metal ions with the detection limit as low as 4.05 × 10⁻⁹ M. PEGBAB displayed high selectivity to Al³⁺ in the pH range of 5–10. The fluorescence response of PEGBAB to Al³⁺ was reversible in the presence of ethylenediaminetetraacetic acid (EDTA). Based on the fluorescence response, an INHIBIT logic gate was constructed with Al³⁺ and EDTA as two inputs. Moreover, test strips based on PEGBAB were fabricated facilely for convenient on-site detection of Al³⁺.

A dual chemosensor for Cu2+ and Hg2+ based on a rhodamine-terminated water-soluble polymer in 100% aqueous solution

A novel water-soluble polymer bearing a rhodamine receptor (PEGSRh) was synthesized as a dual chemosensor for the recognition of Cu2+ and Hg2+ in 100% aqueous solution. PEGSRh not only exhibited a sensitive colorimetric response towards Cu2+ and Hg2+ but also showed a selective turn-on fluorescence response towards Hg2+ over other metal ions. The binding stoichiometry for the complexation of PEGSRh with Cu2+ and Hg2+ was confirmed to be 1 : 1 by Job plot analysis. The low detection limits were found to be 5.92 × 10-7 M for Cu2+ and 2.85 × 10-6 M for Hg2+. The responses of PEGSRh to Cu2+ and Hg2+ were both stable over wide pH ranges. In addition, the fluorescence intensity changes of PEGSRh solution by the inputs of Hg2+, Cu2+ and EDTA have been used to construct a combinational logic gate. Again, an INHIBIT logic gate was also obtained by employing Cu2+ and EDTA as the chemical inputs and the absorbance signal as the output. Moreover, test papers were prepared facilely using PEGSRh for practical on-site detection of Cu2+ and Hg2+.

Raposo MM, Sancenón F. A dual channel sulphur-containing a macrocycle functionalised BODIPY probe for the detection of Hg(ii) in a mixed aqueous solution

Probe 1, containing a BODIPY fluorophore, was able to selectively detect Hg(ii) in water–acetonitrile 95 : 5 solutions by marked colour changes and emission enhancement.

Bodipy-based chemosensors for highly sensitive and selective detection of Hg2+ ions

Small molecular chemo-sensors with strong fluorescence were designed and synthesized. Then, corresponding macromolecular sensors were synthesized by introducing the as-prepared small molecular sensors. The macromolecular chemo-sensors not only retained their sensing ability, but also enhanced the sensing ability dramatically.

A biomimetic fluorescent chemosensor for highly sensitive zinc(ii) detection and its application for cell imaging

To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging. A series tests with various metal ions verified the specific fluorescence response behavior. This novel biomimetic fluorescent chemosensor exhibits excellent selectivity for Zn²⁺ ions over a wide range of tested metal ions in an aqueous solution. Moreover, cytotoxicity and bio-imaging tests were conducted to study the potential bio-application of the chemosensor. Owing to the biomimetic portion (phosphorylcholine), this copolymer possesses outstanding biocompatibility and could clearly image cells. The results indicated that PSaAEMA-co-PMPC has great potential for application in zinc(ii) detection and cell imaging.

To fabricate a novel biomimetic fluorescent chemosensor, PSaAEMA-co-PMPC was synthesized via atom transfer radical polymerization, and this copolymer could be used for the detection of zinc(ii) and cell imaging.

Non-conjugated polyurethane polymer dots based on crosslink enhanced emission (CEE) and application in Fe3+ sensing

A novel non-conjugated polymer dot sensor is developed for Fe³⁺ detection based on crosslink enhanced emission.