Zn-CD@Eu Ratiometric Fluorescent Probe for the Detection of Dipicolinic Acid, Uric Acid, and Ex Vivo Uric Acid Imaging.

Development of reliable methods for the detection of potential biomarkers is of the utmost importance for an early diagnosis of critical diseases and disorders. In this study, a novel lanthanide-functionalized carbon dot-based fluorescent probe Zn-CD@Eu is reported for the ratiometric detection of dipicolinic acid (DPA) and uric acid (UA). The Zn-CD@Eu nanoprobe was obtained from a simple room-temperature reaction of zinc-doped carbon dots (Zn-CD) and the EDTA-Eu lanthanide complex. Under optimal conditions, a good linear response was obtained for DPA in two concentration ranges of 0-55 and 55-100 µM with a limit of detection of 0.53 and 2.2 µM respectively, which is significantly below the infectious dosage of anthrax (∼55 µM). Furthermore, the Zn-CD@Eu/DPA system was employed for the detection of UA with a detection limit of 0.36 µM in the linear range of 0-100 µM. The fluorescent probe was successfully implemented for determining DPA and UA in human blood serum, sweat, and natural water bodies with considerable recovery rates. In addition, the potential of the nanoprobe for ex vivo visualization of UA was demonstrated in fruit fly (Drosophila melanogaster) as a model organism.

Photothermal-Photocatalytic CSG@ZFG Evaporator for Synergistic Salt Rejection and VOC Removal during Solar-Driven Water Distillation.

Sunlight-driven interfacial photothermal evaporation has been considered as a promising strategy for addressing global water crisis. Herein, we fabricated a self-floating porous triple-layer (CSG@ZFG) evaporator using porous fibrous carbon derived from Saccharum spontaneum (CS) as a photothermal material. The middle layer of the evaporator is composed of hydrophilic sodium alginate crosslinked by carboxymethyl cellulose and zinc ferrite (ZFG), whereas the top hydrophobic layer consists of fibrous (CS) integrated benzaldehyde-modified chitosan gel (CSG). Water is transported to the middle layer through the bottom elastic polyethylene foam using natural jute fiber. Such a strategically designed three-layered evaporator exhibits a broad-band light absorbance (96%), excellent hydrophobicity (120.5°), a high evaporation rate of 1.56 kg m-2 h-1, an energy efficiency of 86%, and outstanding salt mitigation ability under the simulated sunlight of intensity 1 sun. Adding ZnFe2O4 nanoparticle as a photocatalyst has been proved to be capable of restricting the evaporation of volatile organic contaminants (VOCs) like phenol, 4-nitrophenol, and nitrobenzene to ensure the purity of evaporated water. Such an innovatively designed evaporator offers a promising approach for the production of drinking water from wastewater and seawater.

Reusable Floating Spherical Hydrogel Evaporator for Solar Desalination with Salt Mitigation and Contaminant Elimination.

The generation of clean and drinkable fresh water from seawater and contaminated water holds great potential to mitigate water scarcity. Herein, a floating spherical hydrogel evaporator (SHE) is designed to achieve sunlight-driven desalination, self-salt cleaning, and removal of environmental contaminants. The spherical lightweight polystyrene is coated with a porous carbon-embedded sodium alginate/PVA/CMC photothermal hydrogel to generate a spherical hydrogel evaporator (SHE) that floats naturally. The SHE is very sensitive to the weight imbalance (500 mg) and can respond quickly to the accumulation of salt by rotation to the fresh evaporation surface, realizing excellent antisalt fouling performance. Remarkably, with energy localization by porous carbon, the spherical floating evaporator achieved a high evaporation rate of 2.65 kg m-2 h-1 with an evaporation efficiency of 98%. At the same time, SHE is also capable of adsorbing both organic contaminants and heavy metal ions through functional groups of the hydrogel, attaining 99% removal efficiency. Overall, this low-cost spherical floating evaporator may offer solution for eco-friendly and sustainable production of fresh water on a large scale.

Selective and sensitive fluorescence turn-on detection of bilirubin using resorcinol-sucrose derived carbon dot.

Carbon dots have been prepared from resorcinol and sucrose (rsCDs) hydrothermally, which show green emission at 525 nm with a fluorescence quantum yield (PLQY) of 17.2%. The intense emission of rsCDs is quenched upon the addition of Cu2+. In the presence of bilirubin (BR), the emission intensity is enhanced due to the competitive binding of Cu2+ with bilirubin and hence releasing rsCDs to the sensing medium. It is the first time report on turn-on fluorescence sensing towards BR with a detection limit of 85 nM. Even in the presence of other comparable biomolecules, the sensor is selective and ultrasensitive to bilirubin. A cellulose paper-based sensor strip has also been designed for the naked-eye detection of BR in blood serum. Due to the specific recognition of this rsCDs towards BR, it can be applied to detect BR in practical human serum samples.

N-Doped Carbon Quantum Dot (NCQD)-Deposited Carbon Capsules for Synergistic Fluorescence Imaging and Photothermal Therapy of Oral Cancer.

Use of nanomaterials blessed with both therapeutic and diagnostic properties is a proficient strategy in the treatment of cancer in its early stage. In this context, our paper reports the synthesis of uniform size N-rich mesoporous carbon nanospheres of size 65-70 nm from pyrrole and aniline precursors using Triton-X as a structure-directing agent. Transmission electron microscopy reveals that these carbons spheres contain void spaces in which ultrasmall nitrogen-doped quantum dots (NCQD) are captured within the matrix. These mesoporous hollow NCQD captured carbon spheres (NCQD-HCS) show fluorescence quantum yield up to 14.6% under λex = 340 nm. Interestingly, samples calcined at >800 °C clearly absorb in the wavelength range 700-1000 nm and shows light-to-heat conversion efficiency up to 52%. In vitro experiments in human oral cancer cells (FaDu) show that NCQD-HCS are internalized by the cells and induce a substantial thermal ablation effect in FaDu cells when exposed under a 980 nm near-infrared laser.

Magnetic Mesoporous Silica Gated with Doped Carbon Dot for Site-Specific Drug Delivery, Fluorescence, and MR Imaging.

Construction of a theranostic agent which integrates multiple modalities with different functions into one entity is challenging from a molecular design and synthesis perspective. In this context, the present paper reports the fabrication of a novel type of multifunctional hybrid nanoparticle composed of magnetic gadolinium oxide-iron oxide core, mesoporous silica shell gated with boronic acid functionalized highly luminescent carbon quantum dot (BNSCQD). The porous silica shell acts as an excellent reservoir for anticancer drug 5-fluorouracil, whereas the BNSCQD cap impressively controls the drug transport under simulated intracellular environment. Furthermore, recognition and fluorescence turn on response of BNSCQD toward cell surface glycan sialyl Lewisa (SLa) enables targeted drug release and excellent fluorescence imaging of SLa overexpressed HePG2 cancer cells. The r1 and r2 relaxivities of the material are found to be 10 and 165 mM-1 s-1 which is comparable to commercially available magnetic resonance imaging contrast agents. Benefiting from the combined advantages of dual stimuli-responsive drug release, excellent optical imaging, and MR imaging, this novel construct can be a promising theranostic material.

Highly Hydrophilic Luminescent Magnetic Mesoporous Carbon Nanospheres for Controlled Release of Anticancer Drug and Multimodal Imaging.

Judicious combination of fluorescence and magnetic properties along with ample drug loading capacity and control release property remains a key challenge in the design of nanotheranostic agents. This paper reports the synthesis of highly hydrophilic optically traceable mesoporous carbon nanospheres which can sustain payloads of the anticancer drug doxorubicin and T2 contrast agent such as cobalt ferrite nanoparticles. The luminescent magnetic hybrid system has been prepared on a mesoporous silica template using a resorcinol-formaldehyde precursor. The mesoporous matrix shows controlled release of the aromatic drug doxorubicin due to disruption of supramolecular π-π interaction at acidic pH. The particles show MR contrast behavior by affecting the proton relaxation with transverse relaxivity (r2) 380 mM(-1) S(-1). The multicolored emission and upconversion luminescence property of our sample are advantageous in bioimaging. In vitro cell experiments shows that the hybrid nanoparticles are endocyted by the tumor cells through passive targeting. The pH-responsive release of doxorubicin presents chemotherapeutic inhibition of cell growth through induction of apoptosis.

Design of Fe3O4@SiO2@Carbon Quantum Dot Based Nanostructure for Fluorescence Sensing, Magnetic Separation, and Live Cell Imaging of Fluoride Ion.

A robust reusable fluoride sensor comprised of a receptor in charge of the chemical recognition and a fluorophore responsible for signal recognition has been designed. Highly fluorescent carbon quantum dot (CD) and magnetically separable nickel ethylenediaminetetraacetic acid (EDTA) complex bound-silica coated magnetite nanoparticle (Fe3O4@SiO2-EDTA-Ni) have been used as fluorophore and fluoride ion receptor, respectively. The assay is based on the exchange reaction between the CD and F(-), which persuades the binding of fluoride to magnetic receptor. This method is highly sensitive, fast, and selective for fluoride ion in aqueous solution. The linear response range of fluoride (R(2) = 0.992) was found to be 1-20 µM with a minimum detection limit of 0.06 µM. Excellent magnetic property and superparamagnetic nature of the receptor are advantageous for the removal and well quantification of fluoride ion. The practical utility of the method is well tested with tap water. Because of high sensitivity, reusability, effectivity, and biocompatibility, it exhibits great promise as a fluorescent probe for intracellular detection of fluoride.

Synthesis of a carbon-dot-based photoluminescent probe for selective and ultrasensitive detection of Hg(2+) in water and living cells.

A nitrogen and sulphur co-doped carbon dot (NSCD) based highly selective photoluminescent probe for mercury detection has been designed. The NSCDs with a PL quantum yield of 69% are easily prepared from a single polymeric molecular precursor. The turn on-off fluorescence change upon mercury addition is attributed to the nonradiative electron transfer from the excited state to the d-orbital of the metal ion. The soft-soft acid-base interaction between the sulphur part of the NSCD and Hg(2+) makes the fluorescence probe more specific and selective towards Hg(2+) in contrast to other metal ions. The limit of detection of mercury ions is found to be 0.05 nM. Due to their high photostability, low toxicity and low detection limit, these carbon dots are demonstrated to be excellent probes for the detection of Hg(2+) in the living cell.

Ca@Cu-CD nanoprobe for dual detection of glycine and ex vivo glycine imaging.

Hydrothermally prepared copper-doped carbon dots (Cu-CDs) were modified with Ca2+, which serve as an excellent platform for the recognition of glycine. The feeble emission of Ca@Cu-CD increases substantially in the presence of glycine due to aggregation-induced emission. At the same time, there was a 5-fold increase in the current response of the Ca@Cu-CD modified electrode as compared to the control. The exceptional combination of fluorescence and conducting properties, along with Ca-glycine interaction, establishes our probe as a dual sensor for the detection of glycine in real serum samples. The limit of detection for this nonenzymatic fluorescence and electrochemical sensing are 17.2 and 4.1 nM, respectively. Furthermore, an extensive evaluation of the toxicity and bioimaging properties in fruit fly Drosophila melanogaster shows that the Ca@Cu-CD probe is not cytotoxic and can be applied for ex vivo imaging of glycine.

A smartphone-assisted ultrasensitive detection of acrylamide in thermally processed snacks using CQD@Au NP integrated FRET sensor.

Selective, sensitive, and accurate detection of acrylamide (AA) in thermally processed food is a great challenge for food safety. This paper describes a "turn-on" fluorescence strategy to detect AA in real samples. Herein, the fluorescence intensity of glutathione-modified carbon quantum dots (GSHCQDs) was quenched initially upon the addition of gold nanoparticles (Au NPs) via fluorescence resonance electron transfer (FRET) to form a quenched GSHCQD-Au nanoprobe. When AA was introduced to the quenched GSHCQD-Au nanoprobe, the strong thiol-ene Michael addition (M-A) reaction among the -SH group of GSHCQD and AA occurred which releases GSHCQD to the medium and FL intensity at 520 nm is regained. The GSHCQD-Au nanoprobe can detect the AA in a normal aqueous solution (pH 7) selectively over a short response time of 5 min. Under the optimized conditions, the detection limit of AA was obtained to be 0.12 pM, over a wide linear range of 0-200 nM. Especially, this FRET-based sensing method was utilized successfully for the sensitive detection of AA using an RGB app installed on a smartphone, opening a new approach for the smart sensing of food contaminants.

Near-Infrared-Induced NO-Releasing Photothermal Adhesive Hydrogel with Enhanced Antibacterial Properties.

Bacterial infection and the development of antibiotic-resistant bacteria have decreased the effectiveness of traditional antibiotic treatments for wound healing. The design of a multifunctional adhesive hydrogel with antibacterial activity, self-healing properties, and on-demand removability to promote wound healing is highly desirable. In this work, a photothermal cyclodextrin with a NO-releasing moiety has been incorporated within an oxidized sodium alginate conjugated polyacrylamide (OS@PA) hydrogel to get a photothermal NO-releasing GSNOCD-OS@PA hydrogel. Such a multifunctional hydrogel has the unique feature of combined antibacterial activity as a result of a controlled photothermal effect and NO gas release under an 808 near-infrared laser. Because of oxidized sodium alginate (OSA), the hydrogel matrix easily adheres to the skin under twisted and bent states. In vitro cytotoxicity analysis against 3T3 cells showed that the hydrogels OS@PA and GSNOCD-OS@PA are noncytotoxic under laser exposure. The temperature-induced NO release by GSNOCD-OS@PA reached 31.7 mg/L when irradiated with an 808 nm laser for 10 min. The combined photothermal therapy and NO release from GSNOCD-OS@PA effectively reduced viability of both Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) to 3 and 5%, respectively. Importantly, the phototherapeutic NO-releasing platform displayed effective fibroblast proliferation in a cell scratch assay.

DSPE-PEG-Coated Uniform Nitrogen-Doped Carbon Capsules for NIR-Mediated Synergistic Chemophototherapy of Skin Cancer.

Uniform monodispersed nitrogen-doped carbon spheres have been emerging as an exciting platform for multipurpose medical applications like photothermal therapy and photoacoustic imaging and as carriers for aromatic anticancer drugs. However, synthesis of uniform N-doped mesoporous carbon of size less than 100 nm with reasonable photothermal and photodynamic activities is a challenging task. In this connection, the present paper reports synthesis of nitrogen-doped mesoporous carbon spheres (NMCSs) from five different copolymers of pyrrole and substituted aniline (-H, o-NH2, m-NH2, p-NH2, and m-NO2) using a soft template approach. It has been found that NMCSs synthesized from poly(pyrrole-co-m-nitroaniline) show uniform mesoporous particles of size 80 nm, a photothermal conversion efficiency η of 52.7%, and an average 1O2 quantum yield of 20% under exposure of a 980 nm NIR laser. With a high η of 52%, a multifunctional nanodrug has been formulated by loading 5-Fu in NMCS. The overall drug-loaded NMC was encapsulated by thermosensitive DSPE-PEG to improve translocation of the particle in the cell and thermosensitive drug release. A reliable release of anticancer drug 5-Fu (78%) has been achieved in 50 h in lysosomal conditions under 980 nm laser exposure. This NMC-5-Fu-DSPE-PEG nanodrug produces reactive oxygen species and enhances the therapeutic effect in comparison with free drug under an NIR laser as verified in B16F0 melanoma cells.

PEG-PEI-modified gated N-doped mesoporous carbon nanospheres for pH/NIR light-triggered drug release and cancer phototherapy.

A novel hybrid drug carrier has been designed, taking N-doped mesoporous carbon (NMCS) as the core and PEG-PEI as the outer shell. NMCS was functionalized with a photocleavable nitrobenzyl-based linker following a click reaction. Gemcitabine was loaded into NMCS prior to the functionalization via π-π stacking interactions. NIR and the pH-responsive behavior of NMCS-linker-PEG-PEI bestow the multifunctional drug carrier with the controlled release of gemcitabine triggered by dual stimuli. The NMCS core upconverts NIR light to UV, which is absorbed by a photosensitive molecular gate and results in its cleavage and drug release. Further, NMCS converts NIR to heat, which deforms the outside polymer shell, thus triggering the drug release process. The release can be promptly arrested if the NIR source is switched off. A promising gemcitabine release of 75% has been achieved within 24 h under the dual stimuli of pH and temperature. NMCS-linker-PEG-PEI produced reactive oxygen species (ROS), which were verified in FaDu cells using flow cytometry. In vitro experiments showed that the NMCS-linker-PEG-PEI-GEM hybrid particle can induce synergistic therapeutic effects in FADU cells when exposed to the NIR light.

Dopamine integrated B, N, S doped CQD nanoprobe for rapid and selective detection of fluoride ion.

A simple fluorescence turn on sensor for the detection of fluoride ion in totally aqueous medium has been developed by integrating boronic acid functionalized carbon quantum dot (BNSCQD) and dopamine. The intense emission of BNSCQD is quenched due to photoelectron transfer (PET) from BNSCQD to dopamine. A remarkable enhancement of emission intensity in presence of F- is achieved due to high reactivity of F- towards boron centre of the BNSCQD-dopamine complex and hence restricting PET between BNSCQD and dopamine. The LOD of our sensor is 0.7 pM. The sensor is not cytotoxic and could be utilised to trace fluoride level changes in human serum as well as in living cells.

Design of superparamagnetic iron oxide nanoparticle for purification of recombinant proteins.

This article reports the synthesis, characterization and also the use of surface modified iron oxide nanoparticles in affinity separation of his-tagged protein. Magnetite particles were prepared by simple coprecipitation of Fe3+/Fe2+ in aqueous medium and then subsequently coated with silica following a sol-gel route. Iminodiacetate was immobilized on them through a silane-coupling agent and charged with Ni2+. These Ni2+ charged magnetic silica nanoparticles have been shown as an efficient carrier, binder and anchor to obtain his-tagged protein directly from total cell lysate. The structural characteristics of the powders were studied by XRD. Magnetic silica particles with 12 nm and aggregate size 90 nm containing inverse spinel magnetite core were observed by transmission electron micrograph and dynamic light scattering. The presence of surface-iminodiacetate groups was shown by FTIR and X-ray photoelectron spectra. The immobilization of Ni2+ through the surface chelating iminodiacetate groups was also studied by XPS. VSM measurement shows these iminodiacetate functionalized magnetic carriers have saturation magnetization 56 e.m.u./g at room temperature. Due to its high efficiency, cost-effectiveness, biocompatibility, and versatility, this magnetic nano-adsorbent may be used as a novel purification system for 6xHis-Tagged recombinant proteins.

Highly luminescent, heteroatom-doped carbon quantum dots for ultrasensitive sensing of glucosamine and targeted imaging of liver cancer cells.

A novel fluorescent boronate nanoprobe has been synthesized by judiciously doping boron, nitrogen, and sulphur in carbon quantum dots (BNSCQD). Specifically, the synergistic presence of nitrogen and sulphur along with boronic acid provides excellent luminescence properties and offers recognition sites for specific sensing of glucosamine. Fluorescence intensity enhances in the presence of glucosamine because of agglomeration of luminescent centers, and thus restricts nonradiative emission channels. The detection limit of this turn on fluorescence for glucosamine is 0.7 nM in PBS. Following this protocol, for the first time, a paper based sensor strip has been prepared for naked eye detection of glucosamine with an LOD of 2.5 µM. The developed nanoprobe shows very low cytotoxicity. More interestingly, boronic acid located on the surface of BNSCQD offers molecular recognition sites for the sialyl Lewisa receptor, which is overexpressed on the surface of liver cancer cells (HepG2). The selective uptake of the BNSCQD nanoprobe in HepG2 cells compared to L929, 3T3 and PC3 cells shows its cell targeting capability.

Synthesis and characterization of ultrafine poly(vinylalcohol phosphate) coated magnetite nanoparticles.

Nanosized magnetite (Fe3O4) particles showing superparamagnetism at room temperature have been prepared by controlled coprecipitation of Fe2+ and Fe3+ in presence of highly hydrophilic poly(vinylalcohol phosphate)(PVAP). The impact of polymer concentration on particle size, size distribution, colloidal stability, and magnetic property has been extensively studied. The aqueous suspension of magnetite, prepared using 1% PVAP solution is stable for four weeks at pH 5-8. X-ray diffractograms show the formation of nanocrystalline inverse spinel phase magnetite. Transmission Electron Microscopy confirmed well dispersed cubic magnetite particles of size of about 5.8 nm. Dynamic Light Scattering measurement shows narrow distribution of hydrodynamic size of particle aggregates. Infrared spectra of samples show strong Fe--O--P bond on the oxide surface. UV-visible studies show aqueous dispersion of magnetite formed by using 1% PVAP solution is stable at least for four weeks without any detoriation of particle size. Magnetization measurements at room temperature show superparamagnetic nature of polymer coated magnetite nanoparticles.

Multifunctional mesoporous hollow silica nanocapsules for targeted co-delivery of cisplatin-pemetrexed and MR imaging.

The development of theranostic mesoporous hollow silica nanospheres having therapeutic and diagnostic functions has been achieved. The exterior surface of the hollow mesoporous silica nanosphere was selectively acid functionalized and utilised to conjugate the anticancer drug cisplatin, the marker molecule folic acid (FA), and rhodamine isothiocyanate (RITC), whereas the interior space was utilised to encapsulate superparamagnetic CoFe2O4 nanoparticles as well as the hydrophobic anticancer drug pemetrexed. The hydrodynamic size of the synthesized multidrug loaded hollow particles is 130 nm in physiological pH and it is consistent over a long period. To the best of our knowledge this is the first report on fluorescent magnetic hollow spheres loaded with multiple therapeutic cargoes as well as a magnetic resonance imaging (MRI) contrast agent. The as prepared hollow spheres are biocompatible. The internalization efficiency of the drug loaded particle has been evaluated on folate receptor overexpressed (FR+ve) HeLa, FR-ve HaCat and 3T3 cells. These drug loaded nanospheres exhibit enhanced cytotoxicity as compared to individual drugs. Such a strategy in the simultaneous administration of pemetrexed and platin drugs may open up opportunities for the treatment of lung cancer at its early stage.