All-in-one strategy for the nano-engineering of paper-based bifunctional fluorescent platform for robustly-integrated real-time monitoring of food and drinking-water safety.

Cu2+ contamination and food spoilage raise food and drinking water safety issues, posing a serious threat to human health. Besides, Cu2+ and H2S levels indicate excess Cu2+-caused diseases and protein-containing food spoilage. Herein, a coumarin-containing bifunctional paper-based fluorescent platform integrated with a straightforward smartphone color recognition app is developed by an all-in-one strategy. The proposed fluorescent materials can simultaneously detect Cu2+ and H2S for on-demand food and drinking water safety monitoring at home. Specifically, a coumarin-derived fluorescence sensor (referred to as CMIA) with a low detection limit (0.430 µM) and high-selectivity/-sensitivity for Cu2+ is synthesized through a simple one-step route and then loaded onto commercially used cellulose fiber filter paper to engineer a biomass-based fluorescent material (CMIA-FP). The CMIA-FP offers user-friendly, high-precision, fast-responsive, and real-time visual monitoring of Cu2+. Moreover, CMIA forms a chemically stable complex with Cu2+, loaded onto filter paper to prepare another biomass-based fluorescent platform (CMIA-CU-FP) for visual real-time monitoring of H2S. Based on the exquisite composition design, the proposed dual-function paper-based fluorescent materials equipped with a smartphone color recognition program concurrently realize fast, accurate, and easy real-time monitoring of Cu2+ in drinking water and H2S in chicken breast-/shrimp-spoilage, demonstrating an effective detection strategy for the Cu2+ and H2S monitoring and presenting the new type of biomass-based platforms for concentrated reflection of drinking water and food safety.

Converting commonly-used paper into nano-engineered fluorescent biomass-based platform for rapid ClO- quantitative detection in living cells and water sources.

Hypochlorous acid (HClO) and derivative ionic form (ClO-) are significant components of reactive oxygen species, and thus various diseases are correlatively related to the concentration of ClO-. Recently, paper-based indicators have been confirmed to be efficient strategy for sensing hazardous and noxious substances. However, most of these materials can only achieve qualitative detection of the substrates. Herein, an extremely simple manufacturing strategy was proposed to convert commonly-used paper into nano-engineered fluorescent biomass-based platform (CMJL-FP) integrated with on-demand self-assembled colorimetric and ratiometric fluorescence sensor (CMJL) for rapid ClO- quantitative detection in organisms or water sources using smartphones. The CMJL exhibited a highly selective and sensitive ratiometric response to ClO- at a low detection limit (LOD = 92.6 nM). The associating interactions between the fluorescence nano-particles and micro-nano fibers of CMJL-FP ensure good-stability during ClO- detection. It has been experimentally demonstrated that CMJL-FP allows one to realize the rapid quantitative detection of ClO- ions in living cells and large-scale water sources by using color recognition software as part of a simple smartphone. Therefore, integrating the proposed fluorescent paper with smartphones provides an effective, sustainable, cheap and conceptual strategy for quantitative detection of hazardous and noxious substances in organisms and environments.

Nature-Skin-Derived e-Skin as Versatile "Wound Therapy-Health Monitoring" Bioelectronic Skin-Scaffolds: Skin to Bio-e-Skin.

Electronic skins (e-skins) have the potential to turn into breakthroughs in biomedical applications. Herein, a novel acellular dermal matrix (ADM)-based bioelectronic skin (e-ADM) is used to fabricate versatile "wound therapy-health monitoring" tissue-nanoengineered skin scaffolds via a facile "one-pot" bio-compositing strategy to incorporate the conductive carbon nanotubes and self-assembled micro-copper oxide microspheres with a cicada-wing-like rough surface and nanocone microstructure. The e-ADM exhibits robust tensile strength (22 MPa), flexibility, biodegradability, electroactivity, and antibacterial properties. Interestingly, e-ADM exhibits the pH-responsive ability for intelligent command between sterilization and wound repair . Additionally, e-ADM enables accurate real-time monitoring of human activities, providing a novel flexible e-skin sensor to record injury and motions. In vitro and in vivo experiments show that with electrical stimulation, e-ADM could prominently facilitate cell growth and proliferation and further promote full-thickness skin wound healing, providing a comprehensive therapeutic strategy for smart sensing and tissue repair, guiding the development of high-performance "wound therapy-health monitoring" bioelectronic skin-scaffolds.

A Review of Recent Progress on Collagen-Based Biomaterials.

Since the 2010s, the demand for healthcare models has exceeded the prevailing resources available due to the rapid increase in the aging population in China. However, a significant gap in development of biomedical materials remains, especially between China and the western developed countries. Collagen is the major protein of the extracellular matrix (ECM) and has been extensively applied in medical fields. Collagen-based biomaterials (CBBs) are used to prepare dressings and dermal substitutes, surgical sutures, plasma substitutes, tissue-engineered scaffolds, and drug delivery systems; this is attributed to their exceptional biocompatibility, biodegradability, hypoimmunogenicity, and coordination between collagen hosts and tissues. This review provides thorough strides in CBB structures, crosslinking and forming technologies, and real-world applications. First, the natural origin and specific structures of animal-derived collagen and non-animal-derived collagen are introduced and compared. Second, crosslinking methods and forming technologies of CBBs across the board are discussed. Third, several examples are considered to demonstrate the practical biomedical use of CBBs and highlight cautionary notes. Finally, the underlying development directions of CBBs from an interdisciplinary perspective are outlined. This review aims to provide comprehensive mechanisms by which collagen can be uniquely and practically used as advanced biomaterial, hence providing options for augmenting its development in China.

Fly-antennae-inspired biomass-based fluorescent platform for NH3 quantitative detection and visual real-time monitoring of seafood spoilage.

Traditional strategies for quantitative detection of NH3 and monitoring of seafood spoilage still have some pervasive issues of cumbersome operation, time-consuming, high-cost, and inefficient real-time monitoring, and visualization. Integration of biomass-based materials and aggregation-induced emission (AIE) fluorescence probes exhibit conceivable potential in seafood detection and environmental monitoring. Herein, a fly-antennae-inspired biomass-based solid-state fluorescent platform (PAA-FP) with effective, easy-to-use, reusable, low-cost and highly sensitive characteristics is nanoengineered for NH3 quantitative detection (detection limit = 0.5 ppm) and visual real-time monitoring of seafood spoilage using smartphones. The PAA-FP possesses an anticipative "fly-antennae-like" microstructure and offers selective recognition of NH3 by naked eyes in daylight with excellent solid-state fluorescence properties. Moreover, PAA-FP is simply reused at least 5 times after AcOH fumigation. Comprehensive application experiments substantiate that PAA-FP successfully achieves quantitative detection of NH3 and realizes the visual real-time daylight monitoring of food spoilage using a simple color recognizing smartphone software. The present study demonstrates an effective fabrication strategy to explore various multifunctional biomass-based materials for sensing hazardous and noxious substances.

A Schiff-based AIE fluorescent probe for Zn2+ detection and its application as "fluorescence paper-based indicator".

A Schiff-based aggregation induced emission (AIE) fluorescent probe with excited intramolecular proton transfer (ESIPT) mechanism was synthesized by grafting 2-hydrazinobenzothiazole onto 2,6-diformyl-4-methylphenol. The probe recognizes Zn2+ selectively and sensitively, accompanied by a significant fluorescence emission increasement change from light yellow-green to strong green. Additionally, a stabilization time of at least 30 min was kept in the recognition process. Besides, a linear relationship was observed between the concentration of Zn2+ and the fluorescence intensity at 525 nm (0.05-10 µM). And thus, the probe can detect Zn2+ quantitatively in aqueous solution with a low detection limit of 1.9 × 10-8 M. Based on the AIE property and the selective recognition of Zn2+, SCH was strategically loaded on the filter paper to develop a novel paper-based indicator for on-site and high-efficiency detection of Zn2+. The results showed that the paper-based indicator could be conveniently applied to the visual inspection of Zn2+ as expected and SCH in the paper-based indicators fortunately exhibited a better stability. Furthermore, our comprehensive application evaluations have confirmed that SCH was capable of detecting Zn2+ in real water samples and imaging Zn2+ in living cells roundly.

A novel chemosensor for the distinguishable detections of Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-visible absorption.

A novel dual-functional chemosensor, derived from the conjugation of rhodamine B with a quinoline derivative (RHQ), was firstly synthesized with high efficiency and cost-effectiveness for the distinguishable detections of Cu2+ and Hg2+ via ring-opening and ring-forming mechanism. The chemosensor exhibits highly selective and distinguishable responses for Cu2+ and Hg2+ in CH3CN-H2O (4:1, v/v) with off-on fluorescence and ratiometric ultraviolet-visible (UV-Vis) absorption changes. Additionally, Cu2+ is identified by opening a rhodamine spirocycle with a UV-Vis absorption band, at around 560 nm and fluorescence turn-on. Interestingly, Hg2+ is discerned by opening the rhodamine spirocycle and by generating a new special cycle for the quinoline unit. Resultantly, there were two UV-Vis absorption bands at around 365 nm and 560 nm, which were accompanied by fluorescence turn-on. Moreover, the chemosensor can quantitatively detect Cu2+ and Hg2+ by off-on fluorescence and ratiometric UV-Vis absorption changes, respectively. Furthermore, the chemosensor with low cytotoxicity could be successfully administered to monitor Cu2+ and Hg2+ in living cells. This work may pay the way for the development of dual-functional chemosensor for quantificationally detecting metal ions in environmental and biological systems.

A dual-channel chemosensor based on 8-hydroxyquinoline for fluorescent detection of Hg2+ and colorimetric recognition of Cu2.

A novel dual-channel chemosensor, 7-allylquinolin-8-ol (AQ), was synthesized based on 8-hydroxyquinoline for selective fluorescence detection of Hg2+ and colorimetric recognition of Cu2+. The chemosensor reacted with Hg2+ and generated a new Hg-containing compound with significantly enhanced fluorescence, which turned from faint blue to strong green. Further experiments indicated that AQ could be used to quantitatively detect Hg2+ via fluorescence spectroscopy with a low detection limit (2.1 nM). The good reversibility of the synthesized chemosensor was also demonstrated using NaBH4. Moreover, AQ was successfully used for the detection of Cu2+ through the formation of a stable coordination compound, which exhibited an ultraviolet-visible (UV-Vis) ratiometric change, while its color changed from colorless to pale yellow under natural light. Additional experiments using various Cu2+ concentrations showed that the developed chemosensor could be further employed for the quantitative ratiometric estimation of Cu2+ by UV-Vis.

Development of a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial with a biomimetic 3D microstructure for efficient hemostasis and tissue repair.

Hemostatic materials based on collagen and chitin are commonly assessed with regard to their topical absorbability and bioactivity. However, their clinical application faces challenges such as relatively long hemostatic and wound healing times, single function, as well as wound bleeding in patients with blood diseases. Herein, a novel bio-inspired "cotton-like" collagen aggregate/chitin based biomaterial for rapid hemostatic and tissue repair (V-3D-Ag-col) was fabricated by a specific gradient-removal solvent approach. Significantly, for the first time, an advanced collagen aggregate (Ag-col) composed of typical D-periodic cross-striated collagen fibrils and thick collagen fiber bundles was used instead of traditional collagen molecules (Col) to construct a hemostatic material. The target material showed a biomimetic 3D microstructure and "cotton-like" appearance, as expected, which were conducive to platelet adhesion and aggregation. The fabricated V-3D-Ag-col exhibited superior thermo-stability, hemostatic activity and biodegradability. More importantly, V-3D-Ag-col could significantly promote cell growth and proliferation. Further, V-3D-Ag-col could accelerate the wound healing process better than the same material based on conventional collagen (V-3D-Col). In consequence, V-3D-Ag-col has the potential to become a new generation of collagen-absorbable functional hemostatic materials. Furthermore, Ag-col can replace the currently available conventional collagen materials as raw materials for the new generation of collagen-based biomedical materials.

Feasibility Study of Tissue Transglutaminase for Self-Catalytic Cross-Linking of Self-Assembled Collagen Fibril Hydrogel and Its Promising Application in Wound Healing Promotion.

Collagen-based bio-hydrogels are undoubtedly a hot spot in the development of biological dressings for wound healing promotion. Herein, glutamine transaminase (TGase), a biological nontoxic cross-linker with high specific activity and reaction rate under mild conditions, was utilized for the self-catalytic cross-linking of the regenerated collagen (COL) fibril hydrogel fabricated through a molecular self-assembly method. The results showed that the natural triple helical conformation of COL remained completely integrated after self-catalytic cross-linking TGase, which was definitively the fundamental for maintaining its superior bioactivity. It was worth noting that TGase could promote the self-assembly process of COL building blocks into a higher order D-period cross-striated structure. Also, the reconstructed TGase cross-linked COL fibrils exhibited a higher degree of interfiber entanglements with more straight and longer fibrils. Meanwhile, the thermal stability of COL was significantly improved after introducing TGase. Besides, the cytocompatibility analysis suggested that the regenerated COL fibril hydrogel showed excellent cell growth activity and proliferation ability when the dosage of TGase is less than 40 U/g. Further, animal experiments indicated that the targeted COL fibril hydrogel could significantly promote skin wound healing, exhibiting better capacity of skin tissue for regeneration than the COL hydrogel untreated as expected. Therefore, the reconstructed TGase cross-linked COL fibril hydrogel could serve as a novel soft material for wound healing promotion.

Recent advances of collagen-based biomaterials: Multi-hierarchical structure, modification and biomedical applications.

Collagen is the most abundant structural protein of connective tissues including skin, tendon, bone and cartilage in mammals. The complicated biosynthesis of nature collagen in vivo, involving numerous intracellular and extracellular steps, causes it to have a multi-hierarchical fibrous architecture. The bioactivity of collagen is mostly depended on its tertiary structure or above. In the past decades, collagen biomaterials have received many attentions in biological applications due to its excellent properties, such as low immunogenicity, biodegradable, biocompatibility, hydrophilicity, easy processing, etc. However, collagen is also suffering from the poor physical and chemical properties (mechanical strength, thermostability, resistance to enzyme and so on). Therefore, the modification of collagen in preparation process is necessary. This review will shed light on the crosslinking methods and the recent advances of collagen-based materials in biomedical applications including skin substitute, bone repair, tendon repair, cartilage repair, neural repair and delivery system.

Photostable Ratiometric Two-Photon Fluorescent Probe for Visualizing Hydrogen Polysulfide in Mitochondria and Its Application.

Hydrogen polysulfide (H2Sn) has currently attracted much research interest because it not only plays an important physiological function in many biological and health-related events, but also is considered as a newfound potent signal transducer. Small-molecule-based ratiometric fluorescent probes have advantages in sensitivity and biodetection, but such approaches that are intentionally developed for H2Sn detection and expected to be mitochondria-accessible are still lacking. In this work, because of the triphenylphosphine group introduced into the molecular scaffold of the naphthalimide derivative, Mito-NRT-HP was successfully applied to visualize intracellular H2Sn in mitochondria with excellent aqueous solubility, super photobleaching resistance, favorable cellular membrane permeability, and good biocompatibility. This one- and two-photon fluorescent probe with high selectivity and sensitivity (limit of detection, LOD = 0.01 µM) evinced a 70-fold enhancement of the fluorescence ratio (I546nm/I478nm) in the presence of H2Sn over other reactive sulfur species (RSS). The experimental results also give Mito-NRT-HP the potential for mapping the H2Sn distribution in mitochondria and evaluating the H2Sn roles in more biological processes, and they demonstrated the practical application possibility of Mito-NRT-HP in the early diagnosis of lipopolysaccharide-induced (LPS-induced) acute organ injury.

A water-stable lanthanide coordination polymer as a multiresponsive luminescent sensor for Fe3+, Cr(vi) and 4-nitrophenol.

Constructing water stable lanthanide coordination polymers (Ln-CPs) is of great importance for practical applications in biological and environmental areas and necessary for systematic research on the relationship between the properties of Ln-CPs and structures of linker ligands. A two-dimensional (2D) Eu coordination polymer (Eu-CP) {[Eu(L)(HCOO)]·H2O}n (H2L = isomer of 5-((pyridin-3-yloxy)methyl)isophthalic acid) is synthesized by the reaction of Eu(NO3)3·6H2O and H2L and heating at 140 °C. Single crystal X-ray diffraction analysis indicates that the Eu-CP presents a 2D network structure formed by binuclear metal clusters and bridged linkers COO- and HCOO-. The luminescence properties of the Eu-CP are explored at room temperature in the solid-state. The Eu-CP emits bright and stable red light due to the antenna effect from the ligand to the metal ion. The characteristic emission peaks of Eu3+ can be observed in its spectra. The luminescence intensity of the Eu-CP can be sensitively quenched by inorganic ions Fe3+, CrO42-, and Cr2O72- and the organic molecule 4-nitrophenol (4-NP). The Eu-CP can be a multiresponsive luminescent sensor in the water phase. Solvent luminescence investigation and PXRD data demonstrate that the Eu-CP exhibits excellent water stability. Therefore, all the sensing experiments are carried out in the water system. This multi-responsive luminescent sensor can detect Fe3+, Cr(vi) or 4-NP with high sensitivity and low detection limits in aqueous solution. Furthermore, the mechanism for the selective sensing of Fe3+, Cr(vi) or 4-NP is also explored which can mainly be explained by energy competition between the absorption of the analytes and the excitation of the Eu-CP.

Lightweight, compressible and electrically conductive polyurethane sponges coated with synergistic multiwalled carbon nanotubes and graphene for piezoresistive sensors.

Lightweight, compressible and highly sensitive pressure/strain sensing materials are highly desirable for the development of health monitoring, wearable devices and artificial intelligence. Herein, a very simple, low-cost and solution-based approach is presented to fabricate versatile piezoresistive sensors based on conductive polyurethane (PU) sponges coated with synergistic multiwalled carbon nanotubes (MWCNTs) and graphene. These sensor materials are fabricated by convenient dip-coating layer-by-layer (LBL) electrostatic assembly followed by in situ reduction without using any complicated microfabrication processes. The resultant conductive MWCNT/RGO@PU sponges exhibit very low densities (0.027-0.064 g cm-3), outstanding compressibility (up to 75%) and high electrical conductivity benefiting from the porous PU sponges and synergistic conductive MWCNT/RGO structures. In addition, the MWCNT/RGO@PU sponges present larger relative resistance changes and superior sensing performances under external applied pressures (0-5.6 kPa) and a wide range of strains (0-75%) compared with the RGO@PU and MWCNT@PU sponges, due to the synergistic effect of multiple mechanisms: "disconnect-connect" transition of nanogaps, microcracks and fractured skeletons at low compression strain and compressive contact of the conductive skeletons at high compression strain. The electrical and piezoresistive properties of MWCNT/RGO@PU sponges are strongly associated with the dip-coating cycle, suspension concentration, and the applied pressure and strain. Fully functional applications of MWCNT/RGO@PU sponge-based piezoresistive sensors in lighting LED lamps and detecting human body movements are demonstrated, indicating their excellent potential for emerging applications such as health monitoring, wearable devices and artificial intelligence.

A resumable two-photon fluorescent probe for Cu2+ and S2- based on magnetic silica core-shell Fe3O4@SiO2 nanoparticles and its application in bioimaging.

A two-photon fluorescent probe for Cu2+ and S2- has been strategically prepared with naphthalimide derivative platform (NPE) covalently grafted onto the surface of magnetic core-shell Fe3O4@SiO2 nanoparticles. The probe (NPE-Fe3O4@SiO2) exhibits selective response to Cu2+ with enhanced fluorescence and efficient separation of Cu2+ with external magnetic field. The consequent product NPE-Fe3O4@SiO2-Cu of NPE-Fe3O4@SiO2 and Cu2+ can work as an excellent sensor for S2- by removing Cu2+ from the complex with fluorescence decreased, recovering the fluorescence of the probe. Therefore, the constituted Off-On-Off type fluorescence monitoring system means the probe is resumable. Moreover, the probe has been used to quantitatively detect Cu2+ and S2- with low detection limits, which are 0.28 µM and 0.12 µM, respectively. Furthermore, the probe shows low cytotoxicity and excellent membrane permeability, which has been successfully applied for monitoring Cu2+ and S2- in living cells and imaging Cu2+ in deep-tissue with two-photon excited fluorescence.

Near-infrared emissive lanthanide hybridized nanofibrillated cellulose nanopaper as ultraviolet filter.

The lanthanide complexes [Yb(fac)3(H2O)2, Yb(tta)3(H2O)2, Nd(tta)3(H2O)2] functionalized nanofibrillated cellulose (Ln-NFC) nanopapers with near-infrared (NIR) luminescence and high transparency are rapidly fabricated after solvent exchange using a simple suction filtration film-making method. The effects of NFC and lanthanide complexes content on their photophysical properties of Ln-NFC nanopapers and their mechanism of UV filters are fully investigated. With increasing lanthanide complexes content in the Ln-NFC nanopaper, their transmittances are gradually decreased while their NIR luminescences are obviously increased. Yb-fac NFC nanopaper has high UVB block rate at 298 nm, whereas the high UVA block ratio of Ln-tta NFC nanopaper is observed at 345 nm. Ln-NFC nanopapers show a much higher photostability without decomposition under UV irradiation at 365 nm over 5 h. The emission spectra of the Ln-NFC nanopaper process the NIR luminescence of the corresponding lanthanide ions through the efficient triplet-triplet energy transfer process. Ln-NFC nanopapers can bring a brilliant future for UV filters, labeling fields and marking soft materials application.

A reversible ratiometric two-photon lysosome-targeted probe for real-time monitoring of pH changes in living cells.

Lysosome pH is known to be acidic (4.5-5.5) and has emerged as a critical physiological factor for lysosome activities and functions. Herein, we designed a novel ratiometric lysosome-targeted fluorescence resonance energy transfer (FRET) pH probe, which was fabricated by integrating the coumarin moiety (donor) with the naphthalimide moiety (acceptor). The sensing mechanism was essentially an integration of ICT and FRET processes, leading to the simultaneous intensity enhancement of coumarin and naphthalimide with a pH increase. Furthermore, morpholine was introduced as a lysosome-targeted group. Moreover, the probe could respond to pH in a proportional relationship at very broad range from pH 4.5 to 11.0 and showed remarkable advantages, including rapid response, high sensitivity and selectivity, suitable pKa of 5.62, and good reversibility. Furthermore, the probe was successfully used as a ratiometric TP lysosome-targeted fluorescence probe, not only for imaging of lysosomal pH, but also for visualizing chloroquine-induced changes of intracellular pH in real time in living cells with low cytotoxicity and autofluorescence. These proof-of concept studies demonstrate the practical application of the probe in biological systems.

A reusable ratiometric two-photon chemodosimeter for Hg2+ detection based on ESIPT and its application in bioimaging.

A novel ratiometric fluorescent chemodosimeter has been developed for reusable detection of Hg2+. The chemodosimeter responds to Hg2+ sensitively and selectively with a remarkable fluorescence change from green to blue through hampering the excited state intramolecular proton transfer (ESIPT) process. This recyclable chemodosimeter can remove Hg2+ from water by forming a unique mercury-containing compound, which could be reused in the presence of NaBH4. Moreover, the chemodosimeter exhibits a ratiometric fluorescence response to Hg2+ with a very low detection limit (1.0 ppb), and it can be used to detect Hg2+ in drinking water. Furthermore, the ratiometric chemodosimeter has been successfully used for imaging Hg2+ in living cells and tissues using two-photon fluorescence microscopy due to the remarkable emission change from green to blue. This provides a novel testing method for detecting Hg2+ in living cells and tissues with low cytotoxicity and autofluorescence.

A sensitive colorimetric and ratiometric fluorescent probe for mercury species in aqueous solution and living cells.

A highly sensitive and selective fluorescent probe for inorganic and organic mercury species displays colorimetric and ratiometric response in a buffer solution via mercury promoted cleavage reaction. The probe is demonstrated to detect CH(3)HgCl in living cells.

A colorimetric and ratiometric fluorescent probe for palladium.

A colorimetric and ratiometric fluorescent probe for the palladium species has been developed based on the Pd(0)-catalyzed cleavage of an allyoxycarbonyl group of amines under mild conditions. The probe displays a highly sensitive and selective response with significant changes in both color (from colorless to jade-green) and fluorescence (from blue to green), through the ICT process.