Ratiometric luminescence detection of H2O2 in food samples using a terbium coordination polymer sensitized with 3-carboxyphenylboronic acid

A ratiometric luminescent probe was fabricated using adenosine monophosphate (AMP) as a bridging ligand and 3-carboxyphenylboronic acid (3-CPBA) as the sensitizer and functional ligand that allowed the probe to recognize hydrogen peroxide (H2O2). The probe was labeled AMP-Tb/3-CPBA. Adding H2O2 caused the nonluminescent 3-CPBA to be converted into 3-hydroxybenzoic acid, which strongly luminesces at 401 nm. This meant that adding H2O2 decreased the AMP-Tb/3-CPBA luminescence intensity at 544 nm and caused luminescence at 401 nm. The 401 and 544 nm luminescence intensity ratio (I401/I544) was strongly associated with the H2O2 concentration between 0.1 and 60.0 μM, and the detection limit was 0.23 μM. Dual emission reverse-change ratio luminescence sensing using the probe allowed environmental effects to be excluded and the assay to be very selective. We believe that the results pave the way for the development of new functionalized lanthanide coordination polymers for use in luminescence assays.

Surface Bio-engineered Polymeric Nanoparticles

Surface bio-engineering of polymeric nanoparticles (PNPs) has emerged as a cornerstone in contemporary biomedical research, presenting a transformative avenue that can revolutionize diagnostics, therapies, and drug delivery systems. The approach involves integrating bioactive elements on the surfaces of PNPs, aiming to provide them with functionalities to enable precise, targeted, and favorable interactions with biological components within cellular environments. However, the full potential of surface bio-engineered PNPs in biomedicine is hampered by obstacles, including precise control over surface modifications, stability in biological environments, and lasting targeted interactions with cells or tissues. Concerns like scalability, reproducibility, and long-term safety also impede translation to clinical practice. In this review, these challenges in the context of recent breakthroughs in developing surface-biofunctionalized PNPs for various applications, from biosensing and bioimaging to targeted delivery of therapeutics are discussed. Particular attention is given to bonding mechanisms that underlie the attachment of bioactive moieties to PNP surfaces. The stability and efficacy of surface-bioengineered PNPs are critically reviewed in disease detection, diagnostics, and treatment, both in vitro and in vivo settings. Insights into existing challenges and limitations impeding progress are provided, and a forward-looking discussion on the field's future is presented. The paper concludes with recommendations to accelerate the clinical translation of surface bio-engineered PNPs.

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

Highlights of the development and application of luminescent lanthanide based coordination polymers, MOFs and functional nanomaterials

The development of lanthanide based coordination polymer and metal-organic framework (CPs and MOFs) nanomaterials as novel functional (e.g. luminescent and magnetic) materials has attracted significant attention in recent times. This is in part due to the wide, but yet unique coordination requirements that the f-metal ions possess, as well as their attractive physical properties, which are often transferred to the bulk material. Hence, there is no surprise, that the design, synthesis and characterisation of lanthanide based CP/MOF materials (featuring either 'pure' lanthanides, or a mixture of both f- and d-metal ions) for applications in gas and small molecule absorption, storage, conversion/catalysis, chemical sensing, bio-imaging, drug delivery, etc. has been a prominent feature in the scientific literature. In this review, we give a selected overview of some of the recent developments in the area of Ln CP/MOF based nanomaterials for sensing, optical materials and bio-medicine research, as well as making reference to some more established examples, with the view of introducing, particularly to new researchers to the field, the powerful and attractive features of lanthanide based materials.

Time-Resolved Fluorescence Detection of Superoxide Anions Based on an Enzyme-Integrated Lanthanide Coordination Polymer Composite

In this work, we proposed a new strategy of fabricating time-resolved fluorescent nanoprobes by using an enzyme-integrated lanthanide coordination polymer (CP) composite for the detection of superoxide anions (O₂^•-). This CP composite was constructed with terbium ions (Tb³⁺) as a metal node, adenosine triphosphate (ATP) as a bridge ligand, and carboxyphenylboronic acid (CPBA) as a sensitizer in which superoxide dismutase (SOD) was encapsulated by a self-adaptive inclusion process. The as-prepared SOD@ATP/Tb-CPBA displays both catalytic and fluorescence properties. Benefiting from the shielding effect of ATP/Tb CP, greatly enhanced catalytic activity and stability against harsh environments can be obtained in the loaded SOD. Meanwhile, the loaded SOD can remove the water molecules on the coordination sphere of Tb³⁺, leading to a significant increase in the fluorescence intensity and lifetime of SOD@ATP/Tb-CPBA. However, upon the addition of O₂^•-, the fluorescence of SOD@ATP/Tb-CPBA was quenched significantly. This is because SOD can convert O₂^•- into H₂O₂ to induce the deboronation of CPBA, resulting in an intramolecular charge transfer process. On this basis, by taking advantage of Tb³⁺ in long lifetime emission, a time-resolved fluorescence method was developed for the detection of O₂^•-, and satisfactory results have been achieved in both buffered aqueous solutions and serum samples. We believe that the presented study will open up a new avenue to develop enzyme-involved fluorescent nanoprobes.

A MnO2–[Ru(dpp)3]Cl2 system for colorimetric and fluorimetric dual-readout detection of H2O2

Two-dimensional (2D) MnO₂ nanosheets were synthesized by a template-free and one-step route, and the dye [Ru(dpp)₃]Cl₂ was linked onto the MnO₂ nanosheet surface via electrostatic interaction. The formed MnO₂–[Ru(dpp)₃]Cl₂ hybrid was used for a dual optical detection for H₂O₂, an important reactive oxygen species (ROS). Upon addition of H₂O₂, the reaction of MnO₂ with H₂O₂ results in the dissolution of MnO₂ nanosheets and simultaneous generation of O₂. The fading of the solution and simultaneous fluorescence change of [Ru(dpp)₃]Cl₂, sensitive to O₂, enables colorimetric and fluorimetric dual-mode detection of H₂O₂. The dual-output assay in a single probe provides a good sensitivity with a detection limit of 0.18 μM H₂O₂. The dual-signal strategy can efficiently overcome the shortcoming of the single detection mode, and improve the detection accuracy by an additional correction of output signals from each other. Moreover, the successful determination of H₂O₂ in the serum samples demonstrates the potential applicability of the MnO₂–[Ru(dpp)₃]Cl₂ based probe in biosensing and bioanalysis.

The MnO₂ nanosheets with anchored [Ru(dpp)₃]Cl₂ were prepared for colorimetric and fluorimetric dual-mode detection of H₂O₂.

A Specific Turn-On Fluorescent Sensing for Ultrasensitive and Selective Detection of Phosphate in Environmental Samples Based on Antenna Effect-Improved FRET by Surfactant

Phosphate is not only an important indicator for aquatic ecosystems, but also plays vital roles in biosystems. A new strategy for ultrasensitive and selective detection of phosphate is fabricated based on a new insight found in this paper, in which a lower concentration of surfactant sodium dodecylbenzenesulfonate (SDBS) can greatly induce fluorescence resonance energy transfer (FRET) from ciprofloxacin (CIP) to Eu³⁺ in the CIP-Eu³⁺ complex. Surfactant SDBS does not act as a sensitizer for enhancing the fluorescence intensity of the system, but acts as a sensitizer of FRET and makes the native fluorescence of CIP quenched completely (switch off). Eu³⁺ ions can coordinate with the oxygen-donor atoms of phosphate, which weakens FRET from CIP to Eu³⁺ and results in the fluorescence recovery of CIP (turn on). The multicomplex of the CIP-Eu³⁺-phosphate has more sensitive fluorescent response than that of the reported coordination nanoparticle-based fluorescent probes. The LOD (S/N = 3) of this sensing system can attain 4.3 nM. The possible interferential substances existing in environmental samples, such as 17 common metal ions, 11 anions, and fulvic acid investigated, do not interfere with the phosphate detection. This sensing system has been successfully applied for phosphate detection in environmental samples such as wastewater, surface water, and atmospheric particulates. This work not only develops a fluorescent probe for the phosphate detection, but also provides a new strategy for designing fluorescent probes based on FRET or coordination nanoparticles.

Fluorescence probe based carboxymethyl cellulose/Tb(III) nanocomposites for detection of Mn2+ with simpleness, rapidness and high sensitivity

A novel, rapid, high selective and sensitive probe, carboxymethyl cellulose (CMC)/Tb(III) with green fluorescence, for detecting Mn²⁺ in aqueous solution during pH = 4-10 was proposed in this work. The probe's synthesis had benefits of mild reaction condition, organic solvent-free and facile operation. A linear relationship between the fluorescence intensity of CMC/Tb(III) probe at 544 nm with 0.046 μM detection limitation and the concentration of Mn²⁺ in the range of 0.1-100 μM was obtained. The probe was also used to detected Mn²⁺ in tap water and the recoveries were between 97.10% and 101.61%, and the relative standard deviations (RSD, n = 5) of all samples were less than 2.04%. The results by UV absorption spectrum and fluorescence quenching suggested that there might be a dynamic quenching occurred to the fluorescence of CMC/Tb(III) probe when Mn²⁺ was involved.

Enzyme-Mimetic Antioxidant Luminescent Nanoparticles for Highly Sensitive Hydrogen Peroxide Biosensing

Hydrogen peroxide (H₂O₂) is an abundant molecule associated with biological functions and reacts with natural enzymes, such as catalase. Even though direct H₂O₂ measurement can be used to diagnose pathological conditions, such as infection and inflammation, H₂O₂ quantification further enables the detection of disease biomarkers in enzyme-linked assays (e.g., ELISA) in which enzymatic reactions may generate or consume H₂O₂. Such a quantification is often measured optically with organic dyes in biological media that suffer, however, from poor stability. Currently, the optical H₂O₂ biosensing without organic-dyes in biological media and at low, submicromolar, concentrations has yet to be achieved. Herein, we rationally design biomimetic artificial enzymes based on antioxidant CeO₂ nanoparticles that become luminescent upon their Eu³⁺ doping. We vary systematically their diameter from 4 to 16 nm and study their catalase-mimetic antioxidant activity, manifested as catalytic H₂O₂ decomposition in aqueous solutions, revealing a strong nanoparticle surface area dependency. The interaction with H₂O₂ influences distinctly the particle luminescence rendering them highly sensitive H₂O₂ biosensors down to 0.15 μM (5.2 ppb) in solutions for biological assays. Our results link two, so far, unrelated research domains, the CeO₂ nanoparticle antioxidant activity and luminescence by rare-earth doping. When these enzyme-mimetic nanoparticles are coupled with alcohol oxidase, biosensing can be extended to ethanol exemplifying how their detection potential can be broadened to additional biologically relevant metabolites. The enzyme-mimetic nanomaterial developed here could serve as a starting point of sophisticated in vitro assays toward the highly sensitive detection of disease biomarkers.

A highly zinc-selective ratiometric fluorescent probe based on AIE luminogen functionalized coordination polymer nanoparticles

A highly zinc-selective ratiometric fluorescent probe was developed based on the cation exchange process of Tb-HDBB-CPNs with Zn²⁺.

Lanthanide/nucleotide coordination polymers: an excellent host platform for encapsulating enzymes and fluorescent nanoparticles to enhance ratiometric sensing

The co-encapsulation of GOx and CDs endows the resulting composite with excellent catalytic and fluorescence activities and enhanced sensing performances.

A turn-on coordination nanoparticle-based fluorescent probe for phosphate in human serum

Coordination nanoparticles (CNPs) are becoming attractive platforms for chemical sensing applications because their unique adjustable properties offer the opportunity to design various luminescent nanoprobes. Here, we present a CNP-based fluorescent nanoprobe, in which fluorophores (rhodamine B, RB) and quenchers (methylene blue, MB) were spontaneously enfolded by coordination networks self-assembled of adenine, biphenyl-4,4'-dicarboxylic acid (BDA) and zinc ions. The aggregation of fluorophores and quenchers in CNPs resulted in a quenched state fluorescence of RB. RB and MB could be released from CNPs in the presence of phosphate, which triggered the fluorescence of RB. On the basis of recognition-driven disassembly principle, a novel turn-on fluorescent probe for the determination of PO4(3-) with a wide response range (0.5-50 μM) has been successfully applied in the detection of phosphate in human serum samples. This work not only develops a probe for phosphate but also provides a general strategy for designing nanoprobes or nanocarriers towards various targets by altering organic linkers or metal ions.

Synthesis of Ag nanoparticle–carbon nanotube–reduced graphene oxide hybrids for highly sensitive non-enzymatic hydrogen peroxide detection

AgNP–CNT–rGO hybrids were successfully prepared and such hybrids exhibited good sensing performance for electrochemical non-enzymatic detection of hydrogen peroxide.

Surfactant-mediated morphology and fluorescent properties of amino acids-based lanthanide coordination polymers

The morphologies and fluorescent properties of Phe/Tb CPs can be mediated by surfactants with different characteristics.