Ex Vivo Glucose Detection in Human Blood Serums with Carbon Quantum Dot-Doped Oleic Acid-Treated Chitosan Nanocomposites

Herein, carbon quantum dot (CQD)-doped oleic acid (OL)-treated chitosan (Ch) nanocomposites (Ch-OL/CQD) are prepared by a simple solution technique for nonenzymatic ex vivo detection of glucose in human blood samples. From the architecture of the structure, it is observed that the agglomeration of CQD is restricted by OL-treated Ch polymeric chain, and simultaneously the inhibition in the entanglement of Ch-OL polymeric chains in the matrix is attained by the incorporation of CQD, thereby proving the high stability of the nanocomposite. In vitro detection of glucose is studied by the "Turn ON-OFF" fluorescence technique which is again evidenced by the shining core image of nanocomposites in HRTEM. A highly selective glucose sensing against interfering sugars due to the specific spatial arrangement of the hydroxyl groups of glucose, leading to prominent hydrogen-bonding interaction is established, with a very low limit of detection (LOD) of 1.51 μM, covering a wide linear domain from 0 to 104 μM, R2 = 0.98. Moreover, the calculated glucose levels in real human blood serums by Ch-OL/CQD nanocomposites are compared with a commercial glucometer, with recovery percentages from 95.8 to 107.3%. The clinical potential is supported by studying the stimuli responsiveness of the nanocomposites as a function of pH and ionic strength, encouraging the operation of the sensor in a complex biological scenario. The present work may offer an opportunity for the monitoring of glucose in the blood for successful diabetes management.

Effects of nitrogen/bismuth-doping on the photocatalyst composite of carbon dots/titanium dioxide nanoparticles (CDs/TNP) for enhanced visible light-driven removal of diclofenac

The present work demonstrates the coupling of titanium dioxide, TiO₂ nanoparticles (TNP) with N-doped, Bi-doped, and N-Bi co-doped rice husk-derived carbon dots (CDs) via a facile dispersion method, forming respective photocatalyst composites of CDs/TNP, N-CDs/TNP, Bi-CDs/TNP and N-Bi-CDs/TNP. Characterization analyzes verified the successful incorporation of respective CDs samples into TNP, forming photocatalyst composite with narrowed band gap and quenched photoluminescence intensity. Photocatalytic activity of TNP and the respective composites was investigated for photodegradation of diclofenac (DCF) under both simulated sunlight and natural sunlight irradiation. The as-prepared N-Bi-CDs/TNP composite showed the best photocatalytic performance among all composites, able to completely degrade 5 ppm of DCF within 60 min and 180 min under both types of visible light irradiation, respectively. The N-Bi-CDs/TNP composite also showed a TOC removal efficiency up to 87.63%. N-Bi-CDs, worked as photosensitizer and electron reservoir, contributed to the outstanding photocatalytic activity of N-Bi-CDs/TNP, whereby the recombination was prolonged and light absorption was shifted towards the visible light region. Furthermore, the composite of N-Bi-CDs/TNP also demonstrated good stability and reusability over repeated degradation cycles. The photodegradation of DCF resulted into several intermediates, which were identified from LC-MS analysis. The present work could provide an insight on the application of heteroatoms doped and co-doped carbon dots in semiconductor oxide as high performance photocatalysts.

Advances in preparation, mechanism and applications of graphene quantum dots/semiconductor composite photocatalysts: A review

Due to the low efficiency of single-component nano materials, there are more and more studies on high-efficiency composites. As zero dimensional (0D) non-metallic semiconductor material, the emergence of graphene quantum dots (GQDs) overcomes the shortcomings of traditional photocatalysts (rapid rate of electron-hole recombination and narrow range of optical response). Their uniqueness is that they can combine the advantages of quantum dots (rich functional groups at edge) and sp² carbon materials (large specific surface area). The inherent inert carbon stabilizes chemical and physical properties, and brings new breakthroughs to the development of benchmark photocatalysts. The photocatalytic efficiency of GQDs composite with semiconductor materials (SCs) can be improved by the following three points: (1) accelerating charge transfer, (2) extending light absorption range, (3) increasing active sites. The methods of preparation (bottom-up and top-down), types of heterojunctions, mechanisms of photocatalysis, and applications of GQDs/SCs (wastewater treatment, energy storage, gas sensing, UV detection, antibiosis and biomedicine) are comprehensively discussed. And it is hoped that this review can provide some guidance for the future research on of GQDs/SCs on photocatalysis.

Synthesis and Characterization of Carbon Dots Coated CaCO3 Nanocarrier for Levofloxacin Against Multidrug Resistance Extended-Spectrum Beta-Lactamase Escherichia coli of Urinary Tract Infection Origin

The multidrug resistance (MDR) Escherichia coli having Extended-Spectrum Beta-Lactamase (ESBL) genes and the capacity to create a biofilm acts as a major reduction in the therapeutic effectiveness of antimicrobials. In search of a novel nanocarrier (NC) for targeted delivery of antibiotics, carbon dots (CDs) coated calcium carbonate nanocarriers (CCNC) from organic chicken eggshells conjugated with levofloxacin (Lvx) were synthesized. Our main objectives were to explore the antimicrobial, antibiofilm, and NC potential of CDs coated CaCO₃ Nanocarrier conjugated with levofloxacin (CD-CCNC-Lvx) to combat biofilm-producing MDR ESBL E. coli of urinary tract infection origin. The synthesized NC system was physiochemically characterized, validating the synthesis of CCNC and CD-CCNC-Lvx with a particle size of 56 and 14 nm, respectively. Scanning electron microscopy (SEM) showed rod shape morphology. X-ray diffraction results discovered crystalline and dispersed nanoparticles. In vitro release drug kinetics illustrated sustained release of Lvx. NC system exhibited strong antibacterial and antibiofilm potential against E. coli with a noticeable low minimal inhibitory concentration (MIC). MIC of CCNC was found to be 30 ± 0.1 μg/mL and CD-CCNC-Lvx was 20 ± 0.1 μg/mL for MDR ESBL-producing E. coli. The synergistic effect of NC upon conjugation with Lvx showed incredible activity with 30 mm zone of inhibition and 68% biofilm inhibition. Flow cytometry analysis revealed treated E. coli cells showed 58.69% reduction in cell viability. SEM images of treated bacterial cells showed morphological changes, which were also confirmed by our flow cytometry findings leading to cell membrane damage in E. coli. NC system also downregulated the bla_CTX-M gene in E. coli. The hemolytic analysis proved biocompatibility with human red blood cells (RBCs). It is concluded that CCNC has the potential to be used as NC for target delivery of antibiotics and may combat toxicity of antibiotics as the inhibition of E. coli was noticed at low MIC concentration.