Palladium Coordination Polymers Nanosheets: New Strategy for Sensitive Photothermal Detection of H2S

Application of photothermal effects of nanomaterials in food safety detection

Numerous nanomaterials endowed with outstanding light harvesting and photothermal conversion abilities have been extensively applied in various fields, such as photothermal diagnosis and therapy, trace substance detection, and optical imaging. Although photothermal detection methods have been established utilizing the photothermal effect of nanomaterials in recent years, there is a scarcity of reviews regarding their application in food safety detection. Herein, the recent advancements in the photothermal conversion mechanism, photothermal conversion efficiency calculation, and preparation method of photothermal nanomaterials were reviewed. In particular, the application of photothermal nanomaterials in various food hazard analyses and the newly established photothermal detection methods were comprehensively discussed. Moreover, the development and promising future trends of photothermal nanomaterial-based detection methods were discussed, which provide a reference for researchers to propose more effective, sensitive, and accurate detection methods.

Realizing Ultrasensitive and Accurate Point-of-Care Profiling for ATP with a Triple-Mode Strategy Based on the ATP-Induced Reassembly of a Copper Coordination Polymer Nanoflower

New strategies for accurate and reliable detection of adenosine triphosphate (ATP) with portable devices are significant for biochemical analysis, while most recently reported approaches cannot satisfy the detection accuracy and independent of large instruments simultaneously, which are unsuitable for fast, simple, and on-site ATP monitoring. Herein, a unique, convenient, and label-free point-of-care sensing strategy based on novel copper coordination polymer nanoflowers (CuCPNFs) was fabricated for multimode (UV-vis, photothermal, and RGB values) onsite ATP determination with high selectivity, sensitivity, and accuracy. The resulting CuCPNFs with a 3D hierarchical structure exhibit the ATP-triggered decomposition behavior because the competitive coordination between ATP and the copper ions of CuCPNFs can result in the formation of ATP-Cu, which reveals preeminent peroxidase mimics activity and can accelerate the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) to form oxTMB. During this process, the detection system displayed not only color changes but also a strong NIR laser-driven photothermal effect. Thus, the photothermal and color signal variations are easily monitored by a portable thermometer and a smartphone. This multimode point-of-care platform can meet the requirements of onsite, without bulky equipment, accuracy, and reliability all at once, greatly enhancing its application in practice and paving a new way in ATP analysis.

Construction of smartphone-adapted signal visualization platform for dual-mode detection of H2S based on integrated metal-organic framework nanoprobes

Hydrogen sulfide (H2S) is a toxic contaminant and has great influence on many physiological processes. Due to various pathophysiological roles and environmental pollution problems, it is necessary to construct and develop simple and portable monitoring sensors for the precise detection of H2S. Herein, we developed a smartphone-adapted dual-mode detection platform by integrating the colorimetric and photothermal imaging analysis into a metal-organic framework-based chip (ZIF-8/Cu). Due to the nanoconfinement effect of ZIF-8, small-sized plasmonic CuS could be in-situ formed during the detection procedure of H2S and endowed the chips with excellent photothermal properties. By constructing a smartphone-adapted photothermal imager, the metal-organic framework-based chip could achieve a portable photothermal imaging analysis of H2S. Moreover, as the formed CuS was a good peroxidase-like nanozyme, the chips could also be used to trigger the enzymic catalytic reaction toward the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2, thus providing another colorimetric sensing mode by using a smartphone App. In this smartphone-adapted visualization platform, the portable chemosensors could simultaneously achieve double detection modes at one electrode, which provided a new pathway for the accurate detection of H2S and circumvented the false-positive or negative errors during the detection process. Besides, by using the finite difference time domain (FDTD) simulation method, the in-depth mechanism, including the plasmonic effect and spatial electromagnetic field distribution, was explored to provide a possible reason for the excellent sensing performance of the dual-mode visualization platform. This work provides a new insight into the construction of the accurate, portable and smart sensing platform in the visual screening of H2S.

Photothermal hydrogel-integrated paper-based point-of-care platform for visible distance-readout of glucose

BACKGROUND

The accurate detection of glucose and cholesterol plays a pivotal role in disease diagnosis and home care. To this end, biochemical analyzers have become extensively utilized tools for measuring disease biomarkers. Nonetheless, their poor portability and high cost have restricted their accessibility, limiting their use to laboratory settings and hindering the adoption of point-of-care testing (POCT). In contrast, the emergence of portable and affordable paper-based testing platform has revolutionized diagnostic testing by providing distance signals, enhancing intuitiveness and visual accessibility. Consequently, these platforms have become increasingly suitable for POCT.

RESULTS

We have developed a POCT platform that integrated AuNS@Ag, stimulus-responsive hydrogel and test strips, enabling visual distance reading of glucose. The silver-coated AuNS and enzyme were encapsulated within a temperature-responsive N-isopropylacrylamide-acrylamide (NIPAM-AcAm) hydrogel to act as target recognition and reaction units respectively. Glucose can diffuse freely within the hydrogel porous matrix, thereby instigating enzyme-catalyzed reaction that induce alterations in the photothermal effect of the system. This dynamic process ensures efficient and responsive modulation of the system's photothermal properties. By ingeniously capturing distance signals induced by the photothermal effect-mediated water release the visualization and quantification of target substances are achieved, with a linear range spanning from 0 to 30 mM. The consistency between distance-based POCT platform and commercial blood glucose meter demonstrates that the platform provides a portable, affordable and reliable method for visual reading biomarkers.

SIGNIFICANCE

The proposed strategy enables direct, visual quantitative analysis of the target without the need for additional analytical instruments. Particularly, this method holds significant promise as an efficient platform for cholesterol and other disease markers measurement.

Electrochemical sensor for hydrogen sulfide detection using electrocatalysis-assisted amplification and chemical reaction-mediated signal enhancement

An ultrasensitive electrochemical biosensing platform has been designed by combining electrocatalysis-assisted H2S amplification with a chemical reaction-mediated electrochemical signal-boosted system for H2S detection based on Cu-Mn(OH)2 hexagonal nanorings. The signal amplification is initiated by an electrocatalysis reaction that can grasp specific H2S substrates and further highly amplify electrochemical signals. Then, the unique chemical reaction is powered by copper ion and generates a large amount of electroactive CuxS products on the electrode surface, thus achieving the multiple amplification of H2S detection. Finally, the Cu-Mn(OH)2 loaded with plenty of electroactive CuxS can be captured on the electrode for further improving the electrochemical signal thus obtaining ultra-high sensitive determination of H2S. The established electrochemical biosensing platform displays a wide analytical range of 0.1 μM to 265 μM with a low detection limit of 0.096 μM. The satisfactory selectivity allows the electrochemical sensor to distinguish H2S from other interfering substances without any complicated pretreatment, even in complex tumor cell samples. Thus, our designed electrocatalysis-assisted amplification strategy offers a powerful analysis toolkit for the early determination of H2S-related disease in clinical diagnosis.

Pd(II)-based coordination polymer nanosheets for ratiometric colorimetric and photothermal dual-mode assay of serum alkaline phosphatase

Fabrication of a multi-signal readout assay with high sensitivity and selectivity is highly desirable for clinical and biochemical analysis, but remains a challenge due to laborious procedures, large-scale instruments, and inadequate accuracy. Herein, a straightforward, rapid, and portable detection platform based on palladium(II) methylene blue (MB) coordination polymer nanosheets (PdMBCP NSs) was unveiled for the ratiometric dual-mode detection of alkaline phosphatase (ALP) with temperature and colorimetric signal readout properties. The sensing mechanism is the ALP-catalyzed generation of ascorbic acid for competitive binding and etching PdMBCP NSs to release free MB in a quantitive means for detection. Specifically, ALP addition led to the decrease of temperature signal readout from the decomposed PdMBCP NSs under 808 nm laser excitation, and simultaneous increase of the temperature from the generated MB with a 660 nm laser, together with the corresponding absorbance changes at both wavelengths. Notably, this ratiometric nanosensor exhibited a detection limit of 0.013 U/L (colorimetric) and 0.095 U/L (photothermal) within 10 min, respectively. The reliability and satisfactory sensing performance of the developed method were further confirmed by clinic serum samples. Therefore, this study provides a new insight for the development of dual-signal sensing platforms for convenient, universal, and accurate detection of ALP.

Observing hydrogen sulfide in the endoplasmic reticulum of cancer cells and zebrafish by using an activity-based fluorescent probe

A crucial endogenous signaling chemical, hydrogen sulfide, is involved in many physiological actions. In this work, we created the fluorescent probe ER-Nap-NBD using a naphthalimide fluorophore as the signal reporter, a 7-nitro-1,2,3-benzoxadiazole amine as the responsive moiety, and a sulfonamide part for endoplasmic reticulum targeting. ER-Nap-NBD could be detected the H₂S levels in solution and in living systems (cells and zebrafish).

Smartphone-Based Photothermal Lateral Flow Immunoassay Using Rhenium Diselenide Nanosheet

Developing a rapid antibody-based detection method is of great importance for preventing and controlling the spread of coronavirus disease 2019 (COVID-19). Among the antibody-based methods for point-of-care (POC) detection, lateral flow immunoassay (LFIA) is the most widely used. However, LFIA still has the disadvantage of low sensitivity. In this work, an ReSe2 nanosheet with a thickness of 10-20 nm was prepared by liquid exfoliation and applied as the label in a photothermal LFIA due to its high photothermal conversion efficiency and high photothermal stability. An integrated detection device was introduced for rapid, on-site, and highly sensitive assay of the human antisevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Spike (S) protein IgG antibodies. The device mainly included a rhenium diselenide (ReSe2) nanosheet-based photothermal LFIA, a portable laser, and a smartphone with a portable thermal imager, which was used to record and analyze the thermal signal of the LFIA test zone. The human anti-SARS-COV-2 S protein IgG antibodies in buffer solution can be detected in a portable box within 10 min, with a thermal signal detection limit of 0.86 ng mL-1, which was 108-fold lower than that of the colorimetric signal. The integrated device can detect values as low as 2.76 ng mL-1 of the human anti-SARS-COV-2 S protein IgG antibodies in 50% serum. The integrated device showed great potential for rapid and home self-testing diagnosis of COVID-19.

Recent Progress and Applications of Thermal Lens Spectrometry and Photothermal Beam Deflection Techniques in Environmental Sensing

This paper presents recent development and applications of thermal lens microscopy (TLM) and beam deflection spectrometry (BDS) for the analysis of water samples and sea ice. Coupling of TLM detection to a microfluidic system for flow injection analysis (μFIA) enables the detection of microcystin-LR in waters with a four samples/min throughput (in triplicate injections) and provides an LOD of 0.08 µg/L which is 12-times lower than the MCL for microcystin-LR in water. μFIA-TLM was also applied for the determination of total Fe and Fe(II) in 3 µL samples of synthetic cloudwater. The LODs were found to be 100 nM for Fe(II) and 70 nM for total Fe. The application of µFIA-TLM for the determination of ammonium in water resulted in an LOD of 2.3 µM for injection of a 5 µL sample and TLM detection in a 100 µm deep microfluidic channel. For the determination of iron species in sea ice, the BDS was coupled to a diffusive gradient in the thin film technique (DGT). The 2D distribution of Fe(II) and total Fe on DGT gels provided by the BDS (LOD of 50 nM) reflected the distribution of Fe species in sea ice put in contact with DGT gels.

A hydrogen sulphide-responsive and depleting nanoplatform for cancer photodynamic therapy

Hydrogen sulfide (H₂S) as an important biological gasotransmitter plays a pivotal role in many physiological and pathological processes. The sensitive and quantitative detection of H₂S level is therefore crucial for precise diagnosis and prognosis evaluation of various diseases but remains a huge challenge due to the lack of accurate and reliable analytical methods in vivo. In this work, we report a smart, H₂S-responsive and depleting nanoplatform (ZNNPs) for quantitative and real-time imaging of endogenous H₂S for early diagnosis and treatment of H₂S-associated diseases. We show that ZNNPs exhibit unexpected NIR conversion (F₁₀₇₀→ F₇₂₀) and ratiometric photoacoustic (PA₆₈₀/PA₉₀₀) signal responsiveness towards H₂S, allowing for sensitive and quantitative visualization of H₂S in acute hepatotoxicity, cerebral hemorrhage model as well as colorectal tumors in living mice. ZNNPs@FA simultaneously scavenges the mitochondrial H₂S in tumors leading to significant ATP reduction and severe mitochondrial damage, together with the activated photodynamic effect, resulting in efficient suppression of colorectal tumor growth in mice. We believe that this platform may provide a powerful tool for studying the vital impacts of H₂S in related diseases.

A sensitive photothermometric biosensor based on redox reaction-controlled nanoprobe conversion from Prussian blue to Prussian white

As a new low-cost photothermal nanoprobe, Prussian blue nanoparticles (PB NPs) have been demonstrated to have more potential in photothermometric-based point-of-care testing (POCT) application. However, most of the existing PB NP-based photothermometric sensors were constructed mainly relying on in situ generation of PB NPs or their combination with antigens and antibodies, therefore usually suffering from the inherent defects like complicated preparation and cumbersome surface process as well as high-cost modification. To break this limitation of PB NP-based photothermometric POCT, we proposed an ingenious redox reaction-controlled nanoprobe conversion strategy and successfully applied to photothermometric detection of ascorbate oxidase (AAO). In this design, the heat of PB NP photothermal system under 808-nm laser irradiation dramatically decreased with the addition of AA, due to a unique AA-induced Prussian blue to Prussian white (PB-to-PW) conversion. Upon AAO addition, the heat of reaction system increased because of the enzymatic catalytic reaction between AAO and AA, which led to a significant reduction of AA and resultantly inhibited PB-to-PW conversion. Such target-mediated nanoprobe conversion resulted in an obvious temperature change that could be easily detected by a common thermometer and exhibited good linear ranges from 0.25 to 14 mU/mL with a detection limit as low as 0.21 mU/mL for POCT analysis of AAO. This facile, convenient, and portable photothermometric sensing platform provides an innovative route for the design of PB NP nanoprobe-based photothermometric detection methods. A sensitive photothermometric AAO sensor based on a redox reaction-controlled nanoprobe conversion strategy from Prussian blue to Prussian white.

Red-light-responsive coordination polymers nanorods: New strategy for ultrasensitive photothermal detection of targeted cancer cells

The development of highly sensitive and simple detection methods for cancer cells is an important challenge to achieve early cancer diagnosis and effective treatment. In this paper, folic acid (FA)-conjugated platinum (IV) methylene blue (MB) coordination polymers nanorods (denoted as FA-PtCPs NRs) were developed by the photochemical method. The structure of the PtCPs NRs was investigated using the meta-dynamics and genetic algorithms (MTD-GC) method, and it was found that the coordination bond was formed between platinum (IV) and N atoms of MB. The field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) indicated that the morphology of PtCPs NRs was rod-like. The resulting FA-PtCPs NRs was used for the specific and ultra-sensitive temperature detection of cancer cells based on PtCPs NRs as a signal trigger unit and FA as a target recognition tool. After three-step reaction, oxidized 3,3',5,5'-tetramethylbenzidine (ox-TMB) with photothermal effect was obtained. Under 660 nm laser irradiation, such detection platform can convert the molecular recognition signal between FA and folate receptor (FR) of cancer cells into readable temperature value, which can be directly read by an ordinary thermometer, with a detection limit as low as 2 cells/mL. In addition, FA-PtCPs NRs could be used as fluorescent probes for in-situ bioimaging. Therefore, this photothermal sensing platform has a broad prospect in the field of point-of-care detection of cancer cells.

A Fenton-like reaction system with analyte-activated catfish effect as an enhanced colorimetric and photothermal dopamine bioassay

Fenton-like reaction systems have been proven to be efficient as powerful promoters in advanced oxidation processes (AOPs) due to their generated reactive oxygen species (ROS), such as ˙OH and ˙O₂^-, which can further oxidize a specific chromogenic substrate like 3,3',5,5'-tetramethylbenzidine (TMB) to generate sensitive color readout and thereby demonstrate more potential in the colorimetric analysis field. However, the inherent drawback of the low rate-limiting step of Fe³⁺/Fe²⁺ conversion in the Fenton-like reaction and its resultant inefficiency for H₂O₂ decomposition hinder its practical applications. We herein communicate an analyte-activated catfish effect based catalysis strategy to promote the Fenton-like reaction, in which dopamine, like a catfish, was added to activate the Fenton-like reaction. By definition, the conversion rate of Fe³⁺ to Fe²⁺ in the proposed Fenton-like reaction can be significantly accelerated through a specific DA-mediated electron transfer process which further promotes the reaction activity in the Fenton-like reaction to generate more ˙OH and ˙O₂^- radicals. As a result, the produced ˙OH and ˙O₂^- radicals in such a reaction system can significantly oxidize TMB indicator into its oxidation product (TMBox) and therefore indicate the corresponding target-dependent color and photothermal signal readout, enabling the successful fabrication of a more sensitive and stable colorimetric and photothermometric DA sensor. More significantly, this strategy can greatly advance the practical application of Fenton-like reactions in the fields of colorimetric and photothermometric bioassays.

Four-Channel Photothermal Plate Reader for High-Throughput Nanoparticle-Amplified Immunoassay

We enhanced the sample throughput of microplate-based photothermal detection by using a semicylindrical prism to expand a point laser source to a long beam for illuminating multiple wells. Coupled with four epoxy-coated thermocouples in alignment with wells on a 96-well microplate, four parallel immunoassays of C-reaction protein (CRP) with antibody-conjugated gold nanoparticles can be simultaneously performed. The sample throughput is further increased by mounting the Styrofoam-enclosed microplate onto a translational/elevator stage so that immunoassays and thermocouple rinse/drying cycles can be implemented in a programmed fashion. The automated assay with three rinse/drying cycles takes only 34.5 min for four samples or 8.62 min/sample, whereas the manual mode with a single thermocouple and a point light source requires at least 66 min for just one sample. With careful calibration of the energy distribution of the expanded laser beam and controllable immersion of the thermocouples, excellent well-to-well (RSD = 1.3%) and cycle-to-cycle (RSD = 4.0%) reproducibility can be attained. The temperature changes can be correlated with the CRP concentration by the Langmuir isotherm, and the low limit of detection, 0.52 ng/mL or 4.33 pM, is well below the plasma CRP levels of both healthy people (<5 μg/mL) and patients (10-500 μg/mL). The serum CRP concentrations quantified by our plate reader are in excellent agreement with the immunoturbidimetric results, demonstrating that this cost-effective, robust, and high-throughput mode for microplate-based immunoassays is amenable to detecting biomarkers in many clinical samples.

In Situ Generation of Prussian Blue by MIL-53 (Fe) for Point-of-Care Testing of Butyrylcholinesterase Activity Using a Portable High-Throughput Photothermal Device

Butyrylcholinesterase (BuChE), the primary source of serum cholinesterase activity, is an indispensable biochemical marker for clinical diagnosis of liver function and organophosphorus poisoning. The requirement for bulky and expensive instruments represents a huge hindrance for point-of-care testing (POCT) of BuChE, especially in resource-limited settings. Herein, an easy-operated, economic, and portable photothermal (PT) biosensing platform for high-throughput BuChE detection was rationally designed. BuChE could "light up" the PT signal through in situ generation of Prussian blue (PB) by MIL-53 (Fe), which allowed us to translate biological signals into temperature signals. Such temperature change signals could be monitored at high throughput (six samples for a single measurement) by a miniature self-made integrated PT device via combining separable 96-well plates, a three-dimensional (3D) printed sample bracket, 808 nm lasers, and thermometers, satisfying the requirement for rapid on-site detection in a large batch with low cost. In addition, the large specific surface area, 3D network structure, and high porosity of MIL-53 (Fe) offered a beneficial platform for its reaction with enzymatic hydrolysate, resulting in high sensing sensitivity and low detection limit (0.3 U L^-1), which was at least 20 000 times lower than the normal human serum BuChE activity. This facile, affordable, and broad applicability PT sensing platform provides a beneficial reference for the rational design of other disease diagnostic approaches suitable for POCT.

Facile synthesis of ultrahigh fluorescence N,S-self-doped carbon nanodots and their multiple applications for H2S sensing, bioimaging in live cells and zebrafish, and anti-counterfeiting

Green-emissive N,S-self-doped carbon nanodots (N,S-self-CNDs) with an ultrahigh fluorescence (FL) quantum yield (QY) of 60% were synthesized using methyl blue as the only source by a facile hydrothermal approach. The -NH- and -SOx- groups of methyl blue were simultaneously used as nitrogen and sulfur co-dopants to dope into CNDs. The prepared N,S-self-CNDs have an extremely large Stokes shift (∼130 nm) and excitation-independent fluorescence, and are demonstrated to have multiple applications for H2S sensing, bioimaging and anti-counterfeiting. Taking advantage of their excellent optical properties, N,S-self-CNDs could act as a label-free nanoprobe for the detection of H2S. The FL of N,S-self-CNDs could be significantly quenched by H2S because of dynamic quenching, along with excellent selectivity toward H2S from 0.5-15 μM with a detection limit of 46.8 nM. They were successfully employed for the analysis of H2S content in actual samples. Additionally, the nanoprobe was extended to bioimaging in both living PC12 cells and zebrafish, and monitoring H2S in live cells. Furthermore, N,S-self-CNDs have been used to prepare highly fluorescent polymer films by incorporating N,S-self-CNDs in polyvinyl alcohol (PVA). The as-prepared N,S-self-CNDs/PVA films show a prominent dual-mode FL property, implying that they are potential nanomaterials in the anti-counterfeiting field.

Sensitive detection of sulfide ions in red region based on luminescence resonance energy transfer between upconversion nanoparticles and dye-670

Many sulfides are toxic substances that easily harm the respiratory tract, therefore affecting respiratory function or damaging other organs of the body, leading to its failure. Therefore, there is a pressing need to develop methods for sensitive detection of sulfur ions (S^2- ). Based on luminescence resonance energy transfer (LRET) theory, we report the construction of a near-infrared (NIR) excitation luminescence probe using NaGdF₄ :Yb³⁺ ,Er³⁺ @NaYF₄ upconversion nanoparticles (UCNPs) as the donor and dye-670 as the receptor for detection of S^2- . When UCNPs and dye-670 molecules were combined using ligand exchange and electrostatic attraction, LRET occurred and UCNP luminescence was quenched. When S^2- was added to the system, sulfide ions were able to destroy the double bond of the dye, inhibiting LRET and restoring UCNP luminescence. Under optimum condition, the linear range of S^2- detection was 0.65-18.2 μM, and the detection limit was 34.2 nM. This method was applied for determination of S^2- in water with satisfactory results.

Dual mode electrochemical-photoelectrochemical sensing platform for hydrogen sulfide detection based on the inhibition effect of titanium dioxide/bismuth tungstate/silver heterojunction

A novel dual mode sensing platform is constructed for highly selective detection of H₂S, attributing to the efficient electrochemical (EC) and photoelectrochemical (PEC) signal responses of the TiO₂/Bi₂WO₆/Ag heterojunction. On the one hand, TiO₂/Bi₂WO₆/Ag heterojunction with excellent catalytic performance for the reduction of H₂O₂ could be employed act as a probe, providing a remarkable EC response through an amperometric i-t method. On the other hand, this hybrid provides a photoelectric beacon with a favorable energy-band configuration. More interestingly, the EC and PEC responses of the functionalized electrodes are proportionately decreased in response to the generation of Bi₂S₃ and Ag₂S nanoparticles upon exposure to sulfide ions. The decreased EC and PEC signals could be ascribed to the poor catalytic properties and the recombination of photoexcited electron - hole pairs of the Bi₂S₃ and Ag₂S. Under the optimal conditions, the dual mode sensor exhibits a wide linear response in the range from 0.5 μM to 300 μM with a detection limit of 0.08 μM for the detection of H₂S. Enabled by this unique sensitization mechanism, the proposed sensing platform displays an excellent analytical performance with good selectivity, reproducibility and stability, which providing an alternative pathway of H₂S detecting in practical application.

Spatiotemporally controlled O2 and singlet oxygen self-sufficient nanophotosensitizers enable the in vivo high-yield synthesis of drugs and efficient hypoxic tumor therapy

Carrying out the in vivo syntheses of drugs toxic to tumors based on the specific features of the tumor microenvironment is critical for ensuring specific antitumor efficacy. However, achieving in situ high-yield synthetic toxic drugs from non-toxic agents and reducing their drug resistance in hypoxic tumors remain challenges. Herein we created a tumor-microenvironment-responsive porous Pt/Pt(iv) methylene blue coordination polymer nanoshuttle (Pt/PtMBCPNS) photosensitizer with spatiotemporally controlled O2 and singlet oxygen (1O2) self-sufficient for the in vivo high-yield synthesis of drugs and efficient hypoxic tumor therapy. After being endocytosed, the nanophotosensitizer as a cascade catalyst was observed to effectively catalyze the conversion of endogenous H2O2 to O2, and was hence found to play a dual role in the enhanced tumor therapy. PtMBCPNSs, upon being irradiated with red light, efficiently converted O2 into 1O2. Subsequently, 1O2 oxidized non-toxic 1,5-dihydroxynaphthalene to form the anticancer agent juglone with a high yield. In addition, O2 was found to be able to improve the hypoxic microenvironment without light irradiation, thus enhancing the antitumor efficacy of the produced drugs and reducing drug resistance. As a result, by enhancing the synergistic effect of the treatment, this nanophotosensitizer significantly inhibited the growth of tumors and avoided damage to normal tissues/organs. Collectively, this work highlights a robust nanoplatform with the spatiotemporally controlled in vivo high-yield synthesis of drugs and generation of O2 to help overcome the current limitations of chemical-based therapies against hypoxic tumors.

Fluorinated ZnFeIII Hollow Metal-Organic Framework as a 19F NMR Probe for Highly Sensitive and Selective Detection of Hydrogen Sulfide

Hydrogen sulfide (H2S) is considered as a highly toxic environmental pollutant and an important signal transmitter in physiological processes, and the selective and reliable detection of H2S is of great concern and remains challenging. Herein, we report a smart sensitive "off-on" 19F NMR sensor for H2S by partially introducing a fluorinated ligand to construct a hollow dual metal-organic framework (MOF) nanosystem, F-ZnFeIII hMOF, in which the fluorinated ligand acts as the 19F signal source but is initially quenched due to the strong paramagnetic relaxation enhancement (PRE) effect from neighboring Fe3+ nodes. Upon exposure to sulfide ions, reduction of Fe3+ to Fe2+ is specifically triggered, which attenuates PRE efficiency, thus turning on the 19F NMR signal. The unique hollow MOF architecture benefits the mobility of 19F atoms, thereby improving the response sensitivity. Meanwhile, the desirable H2S-sorption feature and appropriate redox potential of Fe3+/Fe2+ account for the favorable selectivity. The increase in the 19F signal is linear with the concentration of sulfide in the range of 20 to 150 μM with a detection limit of 2.8 μM. The probe is well demonstrated by analyzing H2S in complex matrixes such as biological and foodstuff samples.

Selective detection of sulfide in human lung cancer cells with a blue-fluorescent "ON-OFF-ON" benzimidazole-based chemosensor ensemble

A completely water-soluble, high quantum yield blue-fluorescent benzimidazole derivative (AQ), containing a rigid benzimidazole-thiophene structure, was synthesized. Among 21 metal ions, the fluorescence of AQ was selectively turned off by Cu²⁺ to form an AQ-Cu²⁺ ensemble. Thereafter, the fluorescence of the AQ-Cu²⁺ ensemble was turned on by sulfide (S^2-) with high selectivity and sensitivity in pure water solution. In comparison with AQ-Ag⁺ and AQ-Hg²⁺ ensembles, AQ-Cu²⁺ was the only ensemble that was capable of detecting a sulfide anion. Also, the fluorescence intensity of AQ was linearly proportional to the concentration of Cu²⁺ and S^2-. Both Cu²⁺ and S^2- were detected within a minute in vitro. Moreover, AQ worked best in the pH range of 5-10 and had a limit of detection of 50 nM and 354 nM for Cu²⁺ and S^2- respectively. It was employed for the detection of sulfide in human lung cancer A549 cells with low cytotoxicity.

Enhanced Thermometric Sensor for Arsenate Analysis Based on Dual Temperature Readout Signaling Strategy

New methods for portable detection of arsenate are still in urgent need. Herein, we explored a simple but sensitive thermometric strategy for arsenate determination without complex instruments and skilled technicians. Cobalt oxyhydroxide (CoOOH) nanoflakes, can ingeniously decompose hydrogen peroxide into oxygen in a sealed reaction vessel, accompanied by marked pressure and significant temperature increase due to the exothermic reaction effect (ΔH = -98.2 kJ/mol). The increased pressure then compelled a certain amount of H₂O overflowing from the drainage device into another vessel, leading to a significant temperature decrease due to the preloaded ammonium nitrate (NH₄NO₃) and its good dissolution endothermic effect (ΔH = 25.4 kJ/mol). In the presence of arsenate, the catalytic activity of CoOOH nanoflakes for H₂O₂ decomposition was inhibited dramatically, resulting in an obvious decrease of the pressure, weighting water and temperature response. The two temperature responses with increasing and decreasing feature were easily measured through a common thermometer, and exhibited an effective signaling amplification via coupling both "signal-on" and "signal-off" temperature readout elements. The obtained dual superimposing temperature readout exhibits a good linear with the concentration of arsenate with a lower detection limit (51 nM, 3.8 ppb). Compared to the inductively coupled plasma mass spectrometry, this enhanced thermometric strategy provides a simple, rapid, convenient, low cost, and portable platform for sensing arsenate in real environmental water.

Aqueous stable Pd nanoparticles/covalent organic framework nanocomposite: an efficient nanoenzyme for colorimetric detection and multicolor imaging of cancer cells

Accurate, sensitive detection of cancer cells from clinical fluids is helpful for screening and early diagnosis of tumors. Here, we develop a facile approach for in situ growth of palladium nanoparticles in an aqueous stable carboxymethyl cellulose-modified covalent organic framework hydrogel (named Pd NPs/CMC-COF-LZU1). The resulting nanocomposite has been proven to show superior catalytic performance for the transformation of N-butyl-4-NHAlloc-1,8-naphthalimide (NNPH) into N-butyl-4-amido-1,8-naphthalimide (NPH), indicated by significant changes in both color and fluorescence. Based on these features, the designed nanocomposite was used as a signal transducer to develop a colorimetric assay and multicolor imaging for accurate and sensitive detection of cancer cells. The transformation of NNPH into NPH enabled the detection system to perform multicolor imaging of HeLa cells. By using folic acid (FA) as a recognition element, a total of 100 cancer cells (HeLa) can be distinguished in 1 mL culture medium with 10% FBS. We envision that these COF-based composite materials (Pd NPs/CMC-COF-LZU1) have tremendous potential applications in biotechnology and biological sciences.