Conjugation Of Carbon Dots Research Articles

Carbon Dots–TiO2 Nanocomposites for the Enhanced Visible‐Light Driven Photodegradation of Methylene Blue

AbstractHerein, the conjugation of carbon dots (CDs) with TiO2 nanoparticles is reported to prepare a photocatalytic nanocomposite for an enhanced visible‐light‐driven photodegradation of methylene blue (MB). CDs are prepared from citric acid (CA) and ethylenediamine (EDA) via hydrothermal treatment. Using MB as a model pollutant, it is observed that, under visible‐light irradiation, the nanocomposite presents an increment of the catalytic performance of 367% when compared to bare TiO2. This is achieved because the addition of CDs leads to increased visible‐light absorption and hinders the recombination of photogenerated charge carriers. Thus, CDs are capable of bridging some of the limitations posed by TiO2. Tests using reactive species scavengers indicate that the main active species involved in the photodegradation by the nanocomposites are superoxide radicals followed by hydroxyl radicals, which differs from bare TiO2. Lastly, a life cycle assessment (LCA) study shows that, when accounting for performance, the nanocomposites have lower relative environmental impacts than bare TiO2. In addition, the safety of the produced CDs is shown by in vitro assays. In summary, due to conjugation with CDs, a relevant increment in the catalytic performance of TiO2 is achieved; providing an important step toward the sustainable rational design of active visible‐light‐driven photocatalysts.

Carbon Dots for Improving Water and Oil Absorption of Sponges

An oil spill is one of the hazardous problems in the ocean. Cleaning the oil spill requires expensive and specific technologies. Nowadays, advanced techniques such as skimmers, oil dispersion agents, in-situ burning and solar-heated oil-absorbent are frequently used to solve the problem. For oil-absorbent materials, further, development is still required to enhance oil dan water absorption. Carbon dots is one of the promising nanoparticles that can be used to improve oil absorption. In this work, we conjugated carbon dots made of pencil leads into several types of sponges. The purpose of this work was to improve oil and water absorption. Our experiment results showed that 2 to 5 nanometres size of ethanol soluble carbon dots were successfully synthesized using a simple electrochemical process. UV-Vis absorption and FTIR spectra showed clear energy transition and functional groups in carbon dots. We used six different sponges with various mass densities from 9 to 174 mg/cm3. Conjugation of carbon dots into the sponge was simply done by immersing the sponge in carbon dot solution and drying it. The conjugation made the mass of the sponge increase. We examined the water and oil absorption capacity of each sponge. Oil absorption capacities were different for each sponge. In general, the addition of carbon dots in sponges increased the mass density of sponge water twice. Furthermore, one type of sponge decreased oil absorption capacity after carbon dots conjugation. Other types of sponges showed an improvement of oil absorption capacity by 60% after carbon dot conjugation. We believe that this work can be further improved to get higher water and oil absorption.

Carbon Dots and Tumor Antigen Conjugates as Nanovaccines for Elevated Cancer Immunotherapy.

Cancer immunotherapy has become one of the current research hotspots. However, the deficiencies including restricted immunogenicity, insufficient antigen presentation, and low responsive rate limited their therapeutic applications. Own to the small size and excellent biocompatibility, carbon dots (CDs) can serve as nanovectors to improve the efficacy of cancer immunotherapy. Herein, a tumor antigen-based nanovaccines (GMal+B16F10-Ag and GMal+CT26-Ag) by the conjugation of CDs with the tumor cell-derived antigens (B16F10-Ag and CT26-Ag) is constructed. These nanovaccines can be effectively taken up by dendritic cells (DC2.4), promote DC cell maturation, cross-present the antigen to T cells, specifically target B16F10 melanoma or CT26 colon cancers, and inhibit tumor growth distinctly. This work illustrates the promise of CDs acting as versatile carriers for antigen delivery to achieve the optimal immunotherapeutic outcomes.

Versatile drug nanocarrier assembly via conjugation of distinct carbon dots

With constant emergencies and severe consequences of various central nervous system (CNS)-related diseases, drug delivery gradually reveals its significance in the modern medicine. The biggest challenge of drug delivery resides in the selection of appropriate drug delivery carrier. 21 th century witnessed the prosperous development of diverse nanomaterials. Due to many excellent properties revealed in nanoscale, nanomaterials have been widely investigated as drug nanocarriers. As a new family member of carbon-based nanomaterials, carbon dots (CDs) have proved to be promising drug nanocarriers. They have been successfully conjugated with various therapeutic agents for targeted drug delivery. However, considering the limitation of single CD preparation in drug delivery, in this study, two distinct CD preparations (G-CDs and Y-CDs) were conjugated to compensate for each other’s deficiencies. Different dialysis bags were employed to purify the CD conjugate (G-Y CDs) and reveal the difference between small and large-conjugated systems. After a series of physicochemical characterizations, G-Y CDs exhibited many nanocarrier-favored properties such as excitation-dependent photoluminescence (PL), diversified surface functionality, controlled morphology and versatile amphiphilicity. To further analyze the formation mechanism of G-Y CDs, self-conjugation was separately surveyed with G-CDs and Y-CDs, which showed that self-conjugation was able to occur between Y-CDs. Eventually, to evaluate the capacity of G-Y CDs as drug nanocarriers for future CNS-related diseases, G-Y CDs were intravascularly injected into the heart of zebrafish. The fluorescence signal in the spinal cord suggested the capability of G-Y CDs to cross the blood-brain barrier (BBB). Therefore, this study reveals a novel strategy to assemble versatile drug nanocarriers through conjugation of distinct CDs.

Direct conjugation of distinct carbon dots as Lego-like building blocks for the assembly of versatile drug nanocarriers

As a promising drug nanocarrier, carbon dots (CDs) have exhibited many excellent properties. However, some properties such as bone targeting and crossing the blood–brain barrier (BBB) only apply to a certain CD preparation with limited drug loading capacity. Therefore, it is significant to conjugate distinct CDs to centralize many unique properties on the novel drug nanocarrier. Considering that CDs have abundant and tunable surface functionalities, in this study, a direct conjugation was initiated between two distinct CD models, black CDs (B-CDs) and gel-like CDs (G-CDs) via an amidation reaction. As a result of conjugation at a mass ratio of 5:3 (B-CDs to G-CDs) and a two-step purification process, the conjugate, black-gel CDs (B-G CDs) (5:3) inherited functionalities from both CDs and obtained an enhanced thermostability, aqueous stability, red-shifted photoluminescence (PL) emission, and a figure-eight shape with a width and length of 3 and 6 nm, respectively. In addition, the necessity of high surface primary amine (NH2) content in the CD conjugation was highlighted by replacing G-CDs with other CDs with lower surface NH2 content. Meanwhile, the carboxyl groups (COOH) on G-CDs were not enough to trigger self-conjugation between G-CDs. Moreover, the drug loading capacity was enhanced by 54.5% from B-CDs to B-G CDs (5:3). Furthermore, when the mass ratio of B-CDs to G-CDs was decreased from 5:30, 5:100 to 5:300, the obtained nanostructures revealed a great potential of CDs as Lego-like building blocks. Also, bioimaging of zebrafish demonstrated that various B-G CDs exhibited properties of both bone targeting and crossing the BBB, which are specific properties of B-CDs and G-CDs, respectively.

Conjugated ternary doped carbon dots from vitamin B derivative: Multispectral nanoprobes for targeted melanoma bioimaging and photosensitization

Multi-color emissive carbon dots (CDs) with intrinsic ternary doping were synthesized by a hydrothermal process from a single precursor, vitamin B1 derivative, thiamine pyrophosphate or ThPP. The origin of the multi-color photoluminescence was ascribed to the hybrid doping (N, S, P) in a carbon framework. The subsequent conjugation of CDs with folic acid (FA) enabled targeted bioimaging and photosensitization of the human melanoma cancer cells, SK-MEL28. The unique excitation-dependent multi-color emission of CD-FA probes allowed wide spectral resolution and targeting for amplified whole cell bioimaging including the nucleus. The photosensitization of cancer cells in the multi-color window was accomplished in a deep tissue cell culture setting. The synthesized CD-FAs showed excellent biocompatibility, photostability, and notably, their cellular targeting with enhanced uptake by folate receptor positive (FR+) cancer cells, SK-MEL28 over folate receptor negative (FR-), HEK293T ones in a co-culture model having both diseased and normal cells. The results demonstrate excellent potential for melanoma diagnostic, mapping and phototherapeutic applications with multi-spectral sensitivity.

Conjugation of Carbon Dots with β-Galactosidase Enzyme: Surface Chemistry and Use in Biosensing

Nanoparticles have been conjugated to biological systems for numerous applications such as self-assembly, sensing, imaging, and therapy. Development of more reliable and robust biosensors that exhibit high response rate, increased detection limit, and enhanced useful lifetime is in high demand. We have developed a sensing platform by the conjugation of β-galactosidase, a crucial enzyme, with lab-synthesized gel-like carbon dots (CDs) which have high luminescence, photostability, and easy surface functionalization. We found that the conjugated enzyme exhibited higher stability towards temperature and pH changes in comparison to the native enzyme. This enriched property of the enzyme was distinctly used to develop a stable, reliable, robust biosensor. The detection limit of the biosensor was found to be 2.9 × 10−4 M, whereas its sensitivity was 0.81 µA·mmol−1·cm−2. Further, we used the Langmuir monolayer technique to understand the surface properties of the conjugated enzyme. It was found that the conjugate was highly stable at the air/subphase interface which additionally reinforces the suitability of the use of the conjugated enzyme for the biosensing applications.

Creation of Linear Carbon Dot Array with Improved Optical Properties through Controlled Covalent Conjugation with DNA.

Controlled conjugation of fluorescent carbon dots (CDs) with DNA and subsequent fabrication of the CDs into an array through hybridization mediated self-assembly in the solution phase is reported. Covalent conjugation of CD with DNA and the subsequent array formation change the mobility of the CD-DNA array in gel electrophoresis and HPLC significantly. Interspatial distance in the CD-DNA array is tuned by the DNA sequence length and maintained at ∼8 ± 0.3 nm as revealed by electron microscopy studies. An increase in fluorescence lifetime by ∼2 ns was observed for the CD-DNA array compared to a solitary CD, vis-á-vis better imaging prospects of HEK293 cells by the former. Thus, the array displays improved fluorescence and unhindered cell penetration.

Carbon dot – Unique reinforcing filler for polymer with special reference to physico-mechanical properties

This work reports the reinforcing efficiency of carbon dots (CDs) in carboxylated acrylonitrile butadiene (XNBR) latex at very low concentration. Amine and carboxyl functionalized CDs have been synthesized from citric acid and glycine. The CDs are covalently conjugated to XNBR latex using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC.HCl) and N-hydroxysuccinimide (NHS) as coupling agents. The covalent conjugation of CDs with XNBR latex has been confirmed by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and X-ray photoelectron spectroscopy (XPS). The optical properties of CDs and XNBR-CDs conjugate have been characterized by ultraviolet (UV) - visible, fluorescence spectroscopy, time-resolved fluorescence spectrophotometer and haze meter. The tensile stress-strain properties of XNBR latex dramatically increases by the addition of CDs to XNBR latex. The maximum tensile stress of 2 phr of CDs loaded XNBR latex is nearly 215% higher than the maximum tensile stress of neat XNBR latex. There is a concomitant decrease in the tan δ peak height and increase in the tan δ peak temperature of XNBR latex with the incorporation of CDs to XNBR latex. In addition, the storage modulus (G′) value of sample containing 2 phr of CDs is 161% higher than the storage modulus value (G′) of neat XNBR latex. The onset of degradation temperature (Ti) value of sample containing 4 phr of CDs is 40 °C higher than the Ti value of neat XNBR latex. On the other hand, the maximum degradation temperature (Tmax) of XNBR latex containing 1 phr of CDs is 11 °C higher than the Tmax value of neat XNBR latex. Morphology of pristine CDs and XNBR-CDs conjugate has been analyzed using transmission electron microscopy (TEM). To the best of our knowledge, this is the first report which analyzes the effect of CDs on the physico-mechanical properties of elastomer contrary to the other novel fillers of carbon family.