Upconverting Carbon Nanodots from EDTA as Near-Infrared Activated Phototheranostic Agents

This work describes the synthesis of nitrogen-doped carbon nanodots (CNDs) synthesized from ethylene diamine tetra acetic acid (EDTA) as a precursor and their application as luminescent agents with a dual-mode theranostic role as near-infrared (NIR) triggered imaging and photodynamic therapy agents. Interestingly, these fluorescent CNDs are more rapidly and selectively internalized in tumor cells and exhibit no cytotoxicity until remotely activated with a NIR illumination source. These CNDs are excellent candidates for photo-theranostic purposes, i.e.: simultaneous imaging and therapy can be carried out on cancer cells using their luminescent properties and the in situ generation of reactive oxidative species (ROS) upon excitation in the NIR range. In the presence of CNDs NIR remote activation induces the in vitro killing of U251 MG cells. Through the use of flow imaging cytometry we have been able to successfully map and quantify the different type of cell deaths induced by the presence of intracellular superoxide anions (¿O2-) and hydrogen peroxide (H2O2) ROS species generated in situ upon NIR irradiation

Laser-driven direct synthesis of carbon nanodots and application as sensitizers for visible-light photocatalysis

We present the first successful synthesis of monodisperse carbon nanodots (CNDs) with tunable photoluminescence (PL) carried out by laser pyrolysis of two common volatile organic precursors such as toluene and pyridine. Remarkably, the initial chemical composition of the precursor determines the formation of undoped or N-doped CNDs and their corresponding absorption response in the visible range (expanded for the latter). We demonstrate the control and versatility of this synthesis method to tune the final outcome and its potential to explore a great number of potential solvent candidates. Furthermore, we have successfully exploited these CNDs (both undoped and N-doped) as effective sensitizers of TiO2 nanoparticles in the visible-light driven photo-degradation of a cationic dye selected as model organic pollutant

Pumping Metallic Nanoparticles with Spatial Precision within Magnetic Mesoporous Platforms: 3D Characterization and Catalytic Application

The present work shows an efficient strategy to assemble two types of functional nanoparticles onto mesoporous MCM-41 silica nanospheres with a high degree of spatial precision. In a first stage, magnetite nanoparticles are synthesized with a size larger than the support pores and grafted covalently through a peptide-like bonding onto their external surface. This endowed the silica nanoparticles with a strong superparamagnetic response, while preserving the highly ordered interior space for the encapsulation of other functional guest species. Second, we report the finely controlled pumping of preformed Pt nanoparticles (1.5 nm) within the channels of the magnetic MCM-41 nanospheres to confer an additional catalytic functionality to the multiassembled nanoplatform. The penetration depth of the metallic nanoparticles can be explained as a result of the interplay between the particle-wall electrostatic attraction and the repulsive forces between neighboring Pt nanoparticles. A detailed transmission electron microscopy and a 3D high-resolution high-angle annular dark-field detector electron tomography study were carried out to characterize the material and to explain the assembly mechanism. Finally, the performance of these multifunctional nanohybrids as magnetically recoverable catalysts has been evaluated in the selective hydrogenation of p-nitrophenol, a well-known pollutant and intermediate in multiple industrial processes

Nitrogen-induced transformation of vitamin C into multifunctional up-converting carbon nanodots in the visible-NIR range

Water-soluble, biocompatible, and photoluminescent carbon nanodots have been obtained from the rationalized carbonization of vitamin C, a well-known antioxidant molecule in the presence of an amine co-reactant. Herein, we describe the positive influence of N-doping to induce a unique pH-dependent lifetime decay response that would be potentially attractive in biological backgrounds with intrinsic fluorescence fluctuations. In addition, the selectivity and sensitivity of the N-containing carbon nanoprobes towards the detection of copper ions at ppm levels is critically enhanced in comparison with the un-doped counterpart, especially in the near-infrared (NIR) range. Finally, the up-converting properties have been also successfully applied to image tumor cells in the visible range and remarkably, in the NIR region in which minimal tissue or water absorption and maximum penetration depth are expected

Uniform luminescent carbon nanodots prepared by rapid pyrolysis of organic precursors confined within nanoporous templating structures

Although several methods on the preparation of carbon nanodots (CNDs) emitting throughout the visible have been recently reported, in most of the processes the product suffers from inhomogeneity in size and shape limiting their impact. Here, we report the synthesis of undoped and nitrogen-doped luminescent carbon nanodots by rapid pyrolysis using ordered mesoporous silica nanorods as confining templates. A rapid thermal decomposition (pyrolysis) within the confined dimensions of their pores leads to a highly uniform size distribution of CNDs with average sizes below 4 nm. These CNDs are synthesized in an extremely short time period (5 min of reaction) by immersion in a fluidized-bed reactor that provides heating homogeneity and ensures fast heat transfer. In addition, a rapid release of the homogeneous CNDs can be easily achieved by a simple ultrasonication-filtration step that prevents further chemical action on the mesoporous templates. The emission of both undoped and N-doped CNDs in colloidal and solid state (with an efficiency of 1–5%) originates from a combination of quantum confinement effects and the presence of oxidized surface states; N-doping introduces resonant absorption states which participate in emission. Furthermore, we present a simple model to describe the excitation-dependent/-independent mechanism of carbon nanodots

Safety of hospital discharge before return of bowel function after elective colorectal surgery

Background: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien\u2013Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9\ub72 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4\u20137) and 7 (6\u20138) days respectively (P < 0\ub7001). There were no significant differences in rates of readmission between these groups (6\ub76 versus 8\ub70 per cent; P = 0\ub7499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0\ub790, 95 per cent c.i. 0\ub755 to 1\ub746; P = 0\ub7659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34\ub77 versus 39\ub75 per cent; major 3\ub73 versus 3\ub74 per cent; P = 0\ub7110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients