Luminescence Changes Research Articles

An AIEgen-based hydrazone-linked covalent organic polymer for solid-state fluorescent materials

The construction of high quantum yield solid-state fluorescent materials is of great importance in preparing organic light-emitting devices. Herein we report an AIEgen-based emissive hydrazone-linked covalent organic polymer (TFBE-TD COP) prepared by a simple solid-state mechanochemical grinding method from 1,1,2,2-tetrakis(4-formyl-(1,1′-biphenyl))ethane (TFBE) and terephthalic tihydrazide (TD) at room temperature. The COP exhibits good emission and very high fluorescence quantum yield (ΦF = 37.7%) in the solid-state because of the synergistic effect of rigid skeleton structure and aggregation induction that restricts the relaxation of tetraphenylethylene (TPE) molecules in the TFBE-TD COP. TFBE-TD COP shows a rapid response and high sensitivity toward trifluoroacetic aid (TFA) gas with significant changes in visual color and luminescence, which could be recovered upon exposure to triethylamine vapor. And the TFBE-TD COP was further coated onto the blue LED to achieve white-light emission. The work provides a general method for preparing AIEgen-based COP and explores its applications in solid-state fluorescent materials for the sensing of toxic gases and the preparation of white LED, offering a new route to the design and application of AIEgen-based COPs.

Controls on luminescence signals in lake sediment cores: A study from Lake Suigetsu, Japan

The luminescence characteristics of sediments are driven by a range of environmental factors and can be used as indicators of both local and regional environmental shifts. Hence, rapid luminescence profiling techniques are increasingly employed during multiproxy analysis of sediment cores, overcoming the practical limitations of traditional (dating) methods. One emerging application of luminescence profiling is in the palaeoenvironmental investigation of lake cores. This study demonstrates the versatility of rapid core profiling using portable optically stimulated luminescence and laboratory profiling techniques for appraising the luminescence characteristics of the Lake Suigetsu (Japan) sediment cores. These techniques were employed across four key time periods, each selected for their unique environmental context and significance on either a local or global scale, in order to identify relationships between down-core luminescence and environmental change. We demonstrate that the luminescence characteristics of the cores are susceptible to a range of environmental perturbations and can therefore act as proxies of past change. Additionally, the quantification of these luminescence signals, alongside an assessment of dose rate variations down-core, supports the notion that future luminescence dating is feasible. The results of this analysis contribute to the wider understanding of the application of luminescence techniques – both profiling and dating – to lake sediment cores. • Rapid down-core profiling techniques are applied to sediment cores from Lake Suigetsu, Japan. • Down-core luminescence signals are sensitive to a range of catchment-scale environmental changes. • Estimates of dose rate are made from elemental concentrations and provide an assessment of chronometric accuracy.

Germanium silicon oxide achieves multi-coloured ultra-long phosphorescence and delayed fluorescence at high temperature

Colour-tuned phosphors are promising for advanced security applications such as multi-modal anti-counterfeiting and data encryption. The practical adoption of colour-tuned phosphors requires these materials to be responsive to multiple stimuli (e.g., excitation wavelength, excitation waveform, and temperature) and exhibit excellent materials stability simultaneously. Here we report germanium silicon oxide (GSO) – a heavy-metal-free inorganic phosphor – that exhibits colour-tuned ultra-long phosphorescence and delayed fluorescence across a broad temperature range (300 – 500 K) in air. We developed a sol-gel processing strategy to prepare amorphous oxides containing homogeneously dispersed Si and Ge atoms. The co-existence of Ge and Si luminescent centres (LC) leads to an excitation-dependent luminescence change across the UV-to-visible region. GSO exhibits Si LC-related ultra-long phosphorescence at room-temperature and thermally activated delayed fluorescence at temperatures as high as 573 K. This long-lived PL is sensitized via the energy transfer from Ge defects to Si LCs, which provides PL lifetime tunability for GSO phosphors. The oxide scaffold of GSO offers 500-day materials stability in air; and 1-week stability in strong acidic and basic solutions. Using GSO/polymer hybrids, we demonstrated colour-tuned security tags whose emission wavelength and lifetime can be controlled via the excitation wavelength, and temperature, indicating promise in security applications.

Development of a NIR iridium(III) complex for self-calibrated and luminogenic detection of boron trifluoride

Boron trifluoride (BF3) is a potential environmental pollutant, and excess exposure to it may cause human diseases. However, the sensitive, rapid and accurate detection of BF3 for on-site purposes is still a challenge. In this work, we developed the first NIR iridium(III)-based probe with dual emission and a Stokes shift of 370 nm for self-calibrated and luminogenic detection of BF3. This probe exhibited a strong luminescence enhancement at around 650 nm to BF3 (0–100 μM) with almost no change in luminescence at 475 nm, displaying a 220-fold I650 nm/I475 nm enhancement at 100 μM of BF3 with a detection limit of 0.35 μM. Moreover, the probe showed a fast response time of less than 5 s to BF3 along with an obvious color change under UV irradiation for visual detection. Importantly, the desirable photophysical properties of the iridium(III)-based probe can be harnessed for time-resolved detection of BF3 in the presence of the fluorescence background. The applicability of the probe was further verified in an organic solvent waste-spiked system and on a glass pane. This work will provide a solid basis for the development of sensitive and on-site BF3 sensing toolkits for environmental monitoring.

Simultaneous Occurrence of Vapochromism and Vapoluminescence in Formaldehyde-Responsive Amino-Functionalized Copper(I) Polymorphic Coordination Polymers

The use of vapor-responsive chromic materials in sensing applications for the detection of harmful volatile organic chemicals is rapidly expanding. Herein, four new amino-functionalized Cu(I) coordination polymers of [CuI(pyt-NH2)]n (1) and (2) and [CuSCN(pyt-NH2)]n (3) and (4) (where pyt-NH2 = 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole) were successfully synthesized. Single-crystal X-ray diffraction analysis reveals that 1 and 2 are iodo-based polymorphs, while 3 and 4 are thiocyanato-based polymorphs. They possess densely diverse crystalline architectures decorated by uncoordinated amino groups as a binding site. Also, 1-4 show a variety of color and luminescence based on the structural diversity. Remarkably, 1 and 2 undergo the change of color and naked-eye solid-state luminescence in response to formaldehyde (FA) vapor, demonstrating simultaneous vapochromism and vapoluminescence. The chromic Cu(I) coordination polymers in this work present for the first time dual-mode vapochromism and vapoluminescence in a highly selective response to FA vapor. The responsive mechanism has been clarified by Fourier transform infrared spectroscopy (FT-IR), electrospray ionization mass spectrometry (ESI-MS), 1H nuclear magnetic resonance (NMR), powder X-ray diffraction (PXRD), and luminescence lifetime measurements, which reveal carbinolamine formation via the specific reaction between FA and the active amino groups of coordinated pyt-NH2. The carbinolamine formation can trigger the structural transformation of 1 and 2, leading to the concurrently selective vapochromism and vapoluminescence induced by FA vapor.

Fluorescence turn on amine detection in a cationic covalent organic framework

Ionic covalent organic frameworks (iCOFs) are new examples of porous materials and have shown great potential for various applications. When functionalized with suitable emission sites, guest uptake via the ionic moieties of iCOFs can cause a significant change in luminescence, making them excellent candidates for chemosensors. In here, we present a luminescence sensor in the form of an ionic covalent organic framework (TGH+•PD) composed of guanidinium and phenanthroline moieties for the detection of ammonia and primary aliphatic amines. TGH+•PD exhibits strong emission enhancement in the presence of selective primary amines due to the suppression of intramolecular charge transfer (ICT) with an ultra-low detection limit of 1.2 × 10‒7 M for ammonia. The presence of ionic moieties makes TGH+•PD highly dispersible in water, while deprotonation of the guanidinium moiety by amines restricts its ICT process and signals their presence by enhanced fluorescence emission. The presence of ordered pore walls introduces size selectivity among analyte molecules, and the iCOF has been successfully used to monitor meat products that release biogenic amine vapors upon decomposition due to improper storage.

A water-soluble luminescent cesium-lead perovskite nanocrystal probe for sensitive detection of penicillamine

In this paper, a water-soluble CsPbBr3 perovskite nanocrystals (PNCs) probe with high photoluminescence was prepared and its analytical application for penicillamine detection was studied after an anion exchange process. The result indicated that the CsPbBr3 PNCs probe after iodide anion exchange (CsPbX3, X = Br/I) had a sensitive optical property that can be changed by penicillamine. The fluorescence intensity of the CsPbX3 PNCs increased and the maximum emission peak of the CsPbX3 blue-shifted in the presence of a lower concentration of penicillamine. By optimizing the degree of anion exchange and the experimental condition, penicillamine in the concentration from 5.0 to 35.0 nM can be linearly detected by the luminescence changes of the CsPbX3 PNCs probe. The color change of the PNCs probe was just right in the red and green bands that can be easily recognized by the naked eyes under 365 nm UV lamps. The mechanism of the phenomenon was further studied and the results indicated the interaction of the sulfhydryl group in the penicillamine with the iodide exchanged in the perovskite is the cause of spectral changes. The CsPbX3 PNCs probe prepared here also had a similar response to other sulfur compounds. Thus, the method proposed here has the potential to establish a universal analytical method for the visualization of sulfur-containing substances in water environments.

Role of PSS-based assemblies in stabilization of Eu and Sm luminescent complexes and their thermoresponsive luminescence

The present work introduces self-assembled polystyrenesulfonate (PSS) molecules as soft nanocapsules for incorporation of Eu3+-Sm3+ complexes by the solvent exchange procedure. The high levels of Eu3+- and Sm3+-luminescence of the complexes derives from the ligand-to-metal energy transfer, in turn, resulted from the complex formation of Eu3+and Sm3+ ions with the three recently synthesized cyclophanic 1,3-diketones. The structural features of the ligands are optimized for the high thermal sensitivity of Eu3+- luminescence in DMF solutions. The PSS-nanocapsules (∼100 nm) provide both colloid and chemical stabilization of the ultrasmall (3–5 nm) nanoprecipitates of the complexes, although their luminescence spectra patterns and excited state lifetimes differ from the values measured for the complexes in DMF solutions. The specific concentration ratio of the Eu3+-Sm3+ complexes in the DMF solutions allows to tune the intensity ratio of the luminescence bands at 612 and 650 nm in the heterometallic Eu3+-Sm3+ colloids. The thermal sensitivity of the Eu3+- and Sm3+-luminescence of the complexes derives from the static quenching both in PSS-colloids and in DMF solutions, while the thermo-induced dynamic quenching of the luminescence is significant only in DMF solutions. The reversibility of thermo-induced luminescence changes of the Eu3+-Sm3+ colloids is demonstrated by six heating-cooling cycles. The DLS measurements before and after the six cycles reveal the invariance of the PSS-based capsule as the prerequisite for the recyclability of the temperature monitoring through the ratio of Eu3+-to- Sm3+ luminescence.

Metal-organic frameworks of rare earth metals embedded side-by-side nanofiber as a switchable luminescent sensor for Fe3+ and Cu2+ in aqueous media

Europium metal-organic frameworks (Eu-MOFs) and terbium metal-organic frameworks (Tb-MOFs) incorporated side-by-side nanofibrous membrane (Eu//Tb SBS NFs) was successfully fabricated by electrospinning. Eu-MOFs or Tb-MOFs emitting red or green light, respectively, were adjusted on each side, and a luminescent sensor with yellow luminescence was prepared by adjusting the ratio of the two MOFs. Eu//Tb SBS NFs have high luminescence efficiency and show sequential changes in luminescence color (yellow-green-gray). To investigate whether it is possible to detect metal ions reliably in aqueous media, we evaluated the wettability of the samples by contact angle measurement and luminescence stability in different pH conditions. Eu//Tb SBS NFs showed selective detection of Fe3+ and Cu2+ in aqueous solutions containing various metal ions. The quenching effect constant (Ksv) for Fe3+ was calculated as 7.62 x 103 M−1 (the limit of detection = 1.6 x 10−7 M), indicating high sensitivity for Fe3+. The luminescence changes of the Eu//Tb SBS NFs resulting from the presence of the metal ions and varying concentrations of the targeted metal ions were confirmed with the naked eye. This is the first report of a nanofibrous membrane with a unique side-by-side structure designed as a luminescence switchable dual sensor for Fe3+ and Cu2+. The superiority of Eu//Tb SBS NFs as luminescent sensors is discussed in this paper.

A copper(I) thiolate coordination polymer with thermochromic and mechanochromic luminescence

A luminescent copper(I) thiolate coordination polymer named [Cu(pot)]n has been synthesized by the employment of the thiol ligand of 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol (Hpot). The maximum emission peak of [Cu(pot)]n at room temperature is located at 609 nm. The compound shows superb luminescent stability toward acidic/alkaline conditions and organic solvents. [Cu(pot)]n exhibits an interesting thermochromic behavior with the luminescence changing from saffron at 77 K to orange at 297 K and yellowish green at 497 K. Meanwhile, its luminescent color changes from orange to red after grinding. Thus, the compound represents a rare example of copper(I) thiolate coordination polymers possessing thermochromic and mechanochromic luminescence simultaneously.

Mechanical properties and recrystallization of quartz in presence of H2O: Combination of cracking, subgrain rotation and dissolution-precipitation processes

Natural quartzite samples, as-is and with 0.1 wt% of added H2O, have been deformed up to ∼30% bulk strain in axial shortening experiments with constant strain rate of ∼10−6 s−1 at 900 °C and 1 GPa, and in strain rate stepping ∼10−5 to ∼10−7 s−1 at 900 °C and 1–1.5 GPa, in order to investigate the role of H2O in deformation and recrystallization of quartz. H2O-added samples showed ∼30 MPa lower mean strengths than as-is samples. Samples weaken slightly after 15% strain with mean flow stresses in the range of 154–227 MPa, and stress exponent (n) values between 1.45 and 2.13. The original quartz grains have been deformed plastically (dislocation glide). Discrete mode I cracks without detectable offset have developed in addition to plastic strain. Deformation was associated with recrystallization of up to 20% of the material in the most deformed parts of the samples. New grains were nucleated by both cracking and subgrain rotation, and were largely reconstituted by H2O-promoted grain boundary migration, related to dissolution-precipitation processes. This reconstitution of material is documented by a change in luminescence to blue, caused by trace elements exchange in quartz structure. The blue luminescence is prominent along healed cracks and high angle grain boundaries while it was not observed along the low angle boundaries formed by subgrain rotation. Compared to the as-is samples, the crack-related recrystallization is more frequent in the H2O-added samples. The low stress exponent values may indicate dissolution-precipitation and grain boundary sliding processes to accommodate incompatibilities at grain boundaries arising from an insufficient number of active slip systems. We suggest that the ubiquitous presence of H2O in nature may promote recrystallization of quartz by combinations of cracking, dislocation glide and creep and dissolution-precipitation processes.

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

A Smart Molecule Showing Spin Crossover Responsive Aggregation-Induced Emission

Rigidity-Tuned Full-Color Emission: Uncommon Luminescence Change from Polymer Free-Volume Variations.

Probing the rigidity change of microenvironments via tracking embedded molecular fluorophore emissions represents a robust approach to monitor various polymer microstructural evolutions and biomolecular events with a high spatiotemporal resolution. However, reported fluorophores exclusively blueshift their emissions (termed as "rigidochromism") or merely alter intensities upon rigidification, suffering from inferior sensitivities, low-contrast outputs, and attenuated biocompatibilities. Here, phenanthridine-fused triazatruxene fluorophores (PTFs) with pronounced bathochromic emission (up to 135nm) toward rigidifying media at a low loading of 5ppm without sacrificing the quantum yields and lifetime are developed. PTFs effectively interact with polymeric matrixes through polar-π interactions and form charge-transfer complexes, resulting to a remarkable fluorescent color change from blue to red-orange over matrix rigidifying. Such a unique anti-rigidochromism enables a highly sensitive rigidity detection (i.e., a subtle polymer molecular-weight change (as low as 1000Da vs up to 10kDa for conventional probes) can result to obvious emission color changes). PTFs are able to noninvasively detect polymerization kinetics and in situ optically report polymer degradations. The broadly (nearly full-spectrum) tunable emission and the efficient coupling between anti-rigidochromism and polymer hierarchical structures/topologies render fluorescence with controlled wavelength and chirality, leading to an unprecedented free-volume-based data encryption and anti-counterfeiting technology with a superhigh security level.

Design of Stimuli-Responsive Phenothiazine Derivatives with Triplet-Related Dual Emission and High-Contrast Mechanochromism Guided by Polymorph Prediction.

The development of high-contrast stimulus-responsive materials with excited triplet emission is of great significance for anti-counterfeiting, sensor and memory applications, but remains a challenge. Here, we report a strategy for the rational design of stimulus-responsive phenothiazine derivatives with triplet-related dual emissions and high-contrast mechanochromism guided by Polymorph Prediction. The designed phenothiazine derivatives have the characters of simple structures, a facile synthetic procedure, and a good crystalline nature. We found that the crystals of those derivatives with the potential to form both quasi-axial (ax) and quasi-equatorial (eq) conformations could undergo conformation transition and show significant emission difference (Δλem >100 nm) under mechanical force. Meanwhile, all these phenothiazine derivatives exhibit aggregation-induced emission and emit room-temperature phosphorescence or thermally activated delayed fluorescence. The significant luminescent change of these materials under different stimuli gives them promise for applications in encryption and anti-counterfeiting.

Structural and luminescence characterization of europium-doped niobium germanate glasses and glass-ceramics: Novel insights from 93Nb solid-state NMR spectroscopy

A thorough understanding of network former roles in optical glasses and glass-ceramics, as well as structural environments of luminescent rare-earth atoms, is paramount to assessing their suitability and effectiveness as components for fully-optical integrated devices. The present contribution sheds light on the overall poorly understood structural role of Nb2O5 in oxide glasses and offers a rationale for the luminescence changes concomitant to the heat-treatment induced glass-to-crystal transition in niobium germanate glasses. To this end, results from 93Nb nuclear magnetic resonance (NMR), Raman, and Eu3+ ion based luminescence spectroscopies as well as 3D micromanufacturing are reported for glasses and glass-ceramics in system (89.9-x)GeO2-xNb2O5-10K2O-0.1Eu2O3. Thanks to very-fast 93Nb magic-angle spinning (MAS) and a novel excitation scheme for Triple-quantum (TQ)MAS solid-state NMR spectroscopy distinct Nb(OGe)6-y(ONb)y species were identified for the first time: at low Nb concentrations structural units with rather low y-values are formed, reaching down to isolated Nb(OGe)6 units – next to units bearing non-bridging oxygen atoms; at intermediate Nb contents and beyond, structural units with increasingly higher y-values up to Nb(ONb)6 are found, resembling the local environments found in crystalline Nb2O5. After the glass-to-crystal transition the Nb local environment maintains a high degree of disorder while some residual glass remains. Moreover, photoluminescence spectroscopy of the europium probes suggests the rare-earth ions are preferentially incorporated into high y-value Nb(OGe)6-y(ONb)y polyhedra based on spectral features such as the phonon sideband, the 5D0 → 7F2/7F1 ratio, and split 4f bands. Finally, femtosecond laser microfabrication of waveguides was successful in the presented europium-doped niobium germanate glasses, making them promising candidates for further studies as photonic devices.

Upconversion luminescence-based aptasensor for the detection of thyroid-stimulating hormone in serum.

Thyroid-stimulating hormone (TSH) plays a crucial physiological and pathological role in humans, and a timely and sensitive detection of TSH is critical for early diagnosis and prevention of thyroid-related diseases. Herein, we developed a simple wash-free biological aptasensor based on luminescence resonance energy transfer (LRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and tetramethylrhodamine (TAMRA) for the detection of TSH with high sensitivity. In this LRET system, UCNPs as donors and TAMRA as receptors were modified with nucleic acid aptamers Apt-1 and Apt-2, respectively. When TSH was present, the two aptamer strands both specifically recognized TSH to form a hairpin-like structure, thereby shortening the space between UCNPs and TAMRA. The LRET occurred under radiation of 980-nm light. By detecting the change of upconversion luminescence (UCL) intensity (I545nm), the activity of TSH was quantified. The resulting detection dynamic range and the limit of detection were 0.1-5.0 mIU·L-1 and 0.065 mIU·L-1, respectively. The aptasensor using UCNPs as LRET donors was capable of effectively eliminating the background interference of a complicated biological environment, and showed good specificity because of the excellent recognition function of aptamers. Due to high sensitivity, easiness of fabrication, operational convenience, and selectivity, the UCL-based aptasensor is a promising candidate for clinical TSH determination. Based on nucleic acid aptamer and the mechanism of luminescence resonance energy transfer (LRET) between upconversion nanoparticles (UCNPs) donor and tetramethylrhodamine (TAMRA) receptor, an aptasensor was constructed for the quantitative analysis of TSH activity in serum by testing the change of I545nm.

A Highly Efficient Luminescent Metal–Organic Framework with Strong Conjugate Unit for Sensing Small Molecules

Comprehensive SummaryLuminescent metal–organic frameworks (LMOFs) have become a promising class of fluorescence sensing materials, however, the multi‐responsive LMOF sensors for organic compounds are rather rare. Herein, a water stable and highly efficient luminescent MOF with the formula of {[Zn(BBZB)(2,6‐NDC)]·solvents}n (JXUST‐10, BBZB = 4,7‐bis(1H‐benzimidazole‐1‐yl)‐2,1,3‐benzothiadiazole and 2,6‐NDC = 2,6‐naphthalenedicarboxylate) was constructed by the incorporation of Zn2+ and two organic ligands (BBZB and 2,6‐NDC) featuring the conjugate system. JXUST‐10 is a three‐dimensional two‐fold interpenetrated framework with good fluorescent property. Based on the luminescent characteristic, JXUST‐10 can be used as a multi‐responsive sensor for detection of three different analytes including tetracycline, benzaldehyde and uric acid via different luminescent change behaviours. Remarkably, fluorescence test paper and LED light devices are used to detect analytes through the visual change of luminescence colour of JXUST‐10 from blue greenish to yellow greenish under ultraviolet light (365 nm) irradiation. Furthermore, the probable sensing mechanisms for three target analytes were also discussed.

Highly emissive coordination polymer derived from tetraphenylethylene-tetrazole chromophore: Synthesis, characterization and piezochromic luminescent behavior

Solid-state materials that exhibit pressure stimulus-response characteristics in a manner of emission signal, known as piezochromic luminescence (PCL), demonstrate great potential in photoelectric devices. The weakened luminescence and insignificant color change in the aggregation state, however, hampers their practical applications. Herein, a highly emissive coordination polymer, [Zn2(H4TTPE)(H2O)4]·H2O (CUST-805), is successfully constructed by employing an AIE-active chromophore as the building block. The structural characterization and photophysical properties are systematically studied. Owing to intrinsic twisted conformation and AIE feature of tetraphenylethylene-tetrazole ligand, CUST-805 achieves the visible and reversible PCL from blue to green switched by different external stimuli. The transformation between crystalline and amorphous states is proved to be the origin of present PCL behavior. Moreover, on basis of electron and energy transfer quenching mechanism, the highly selective and sensitive sensor based on CUST-805 is realized, showing the low detection limit of 0.29 ppm towards 2,4,6-trinitrophenol.

Upconversion Luminescent Humidity Sensors Based on Lanthanide-Doped MOFs

Lanthanide-doped metal-organic frameworks (Y/Yb/Er-MOF) were synthesized by a low-cost solvothermal method. The obtained Y/Yb/Er-MOF shows the cooperative upconversion luminescence of Yb3+ and upconversion luminescence of Er3+ (Yb3+-sensitized) irradiated by a continuous wave 980 nm laser. In order to explore the potential application of Y/Yb/Er-MOF in relative humidity (RH) sensors, the RH responsiveness of Y/Yb/Er-MOF was investigated by measuring the intensity changes of upconversion luminescence. The Y/Yb/Er-MOF possesses two luminescence centers, in which Yb3+ forms emission at 500 nm through the cooperative luminescence effect, and Er3+ achieves 660 nm emission through excited state absorption and successive energy transfer from Yb3+. Hence, the ratio meter luminescence sensor for RH is constructed based on Y/Yb/Er-MOF. The results show that the response of Y/Yb/Er-MOF to RH presents a linear relationship in the range of 11–95%. The cycle stability of Y/Yb/Er-MOF responses to RH was investigated with the intensity changes of upconversion luminescence, and the recovery ratio was more than 93% each time. Therefore, the Y/Yb/Er-MOF is a humidity-sensitive material with great potential for applications such as humidity sensors.

Biomimetic Citrate-Coated Luminescent Apatite Nanoplatforms for Diclofenac Delivery in Inflammatory Environments.

Luminescent nanoparticles are innovative tools for medicine, allowing the imaging of cells and tissues, and, at the same time, carrying and releasing different types of molecules. We explored and compared the loading/release ability of diclofenac (COX-2 antagonist), in both undoped- and luminescent Terbium3+ (Tb3+)-doped citrate-coated carbonated apatite nanoparticles at different temperatures (25, 37, 40 °C) and pHs (7.4, 5.2). The cytocompatibility was evaluated on two osteosarcoma cell lines and primary human osteoblasts. Biological effects of diclofenac-loaded-nanoparticles were monitored in an in vitro osteoblast’s cytokine–induced inflammation model by evaluating COX-2 mRNA expression and production of PGE2. Adsorption isotherms fitted the multilayer Langmuir-Freundlich model. The maximum adsorbed amounts at 37 °C were higher than at 25 °C, and particularly when using the Tb3+ -doped particles. Diclofenac-release efficiencies were higher at pH 5.2, a condition simulating a local inflammation. The luminescence properties of diclofenac-loaded Tb3+ -doped particles were affected by pH, being the relative luminescence intensity higher at pH 5.2 and the luminescence lifetime higher at pH 7.4, but not influenced either by the temperature or by the diclofenac-loaded amount. Both undoped and Tb3+-doped nanoparticles were cytocompatible. In addition, diclofenac release increased COX-2 mRNA expression and decreased PGE2 production in an in vitro inflammation model. These findings evidence the potential of these nanoparticles for osteo-localized delivery of anti-inflammatory drugs and the possibility to localize the inflammation, characterized by a decrease in pH, by changes in luminescence.