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Rahul K Das

Indian Institute of Technology Bombay, Metallurgical Engineering & Material Science, Post-Doc

National Institute of Technology Rourkela, Chemistry, Graduate Student

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Enthusiastic about constructing and analyzing fluorescence based biomolecule nanosensor, targeted drug delivery systems and multifunctional porous nanostructures for application in cancer therapy.
Phone: +916371915834

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El-Sayed Sherif

King Saud University

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University of the Witwatersrand

University of Bath

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Shiraz University

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Papers by Rahul K Das

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

Analytica Chimica Acta, 2019

A simple fluorescence turn on sensor for the detection of fluoride ion in totally aqueous medium ... more 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 Ftowards 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.

Rapid “turn-on” detection of atrazine using highly luminescent N-doped carbon quantum dot

Sensors and Actuators B: Chemical, 2018

Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for ... more Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for the detection of herbicide atrazine. Nitrogen doped carbon quantum dot with PLQY 28% has been prepared from hydrothermal treatment of orthophenylene diamine. The turn-on fluorescence of the probe on addition of atrazine is attributed to aggregation induced fluorescence enhancement of amine functionalized carbon dot. The hydrogen bonding interaction of surface amine groups of carbon dot probe and atrazine makes the probe selective and ultrasensitive towards atrazine even in presence of other pesticides and metal ions. The limit of detection for atrazine sensing was found to be 3 pM, which is the lowest among all reported methods for the detection of atrazine. Due to low detection limit the utility of the developed sensor has also been explored in real agricultural samples. Owing to the excellent luminescence property and photostability this fluorescent probe can also be utilised to detect atrazine in bacterial cell by imaging.

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

Langmuir : the ACS journal of surfaces and colloids, May 8, 2018

Construction of a theranostic agent which integrates multiple modalities with different functions... more 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 Lewis (SL) enables targeted drug release and excellent fluorescence imaging of SL overexpressed HePG2 cancer cells. The r and r relaxivities of the material are found to be 10 and 165 mM s which is comparable to commercially available m...

Enhanced Photodegradation of Organic Pollutants by Carbon Quantum Dot (CQD) Deposited Fe3O4@mTiO2 Nano-Pom-Pom Balls

Industrial & Engineering Chemistry Research, 2016

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

Langmuir, 2016

Judicious combination of fluorescence and magnetic properties along with ample drug loading capac... more 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 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 resorcinol-formaldehyde precursor. The mesoporous matrix shows control release of 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-1S-1. The multicolour-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.

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

Langmuir, 2019

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

J. Mater. Chem. B, 2017

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

Langmuir : American Chemical Society , 2019

Use of nanomaterials blessed with both therapeutic and diagnostic properties is a proficient stra... more 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 λ ex = 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

Langmuir : American Chemical Society , 2018

Construction of a theranostic agent which integrates multiple modalities with different functions... more 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 Lewis a (SL a) enables targeted drug release and excellent fluorescence imaging of SL a overexpressed HePG2 cancer cells. The r 1 and r 2 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 luminescent, heteroatom-doped carbon quantum dots for ultrasensitive sensing of glucosamine and targeted imaging of liver cancer cells

Journal of Materials Chemistry B : Royal Society , 2017

A novel fluorescent boronate nanoprobe has been synthesized by judiciously doping boron, nitrogen... more 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 mM. The developed nanoprobe shows very low cytotoxicity. More interestingly, boronic acid located on the surface of BNSCQD offers molecular recognition sites for the sialyl Lewis a 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. Fluorescence sensing has been emerging as an efficient detection method because of its high sensitivity and spatiotemporal resolution. 1-5 The effectiveness of boronic acid as a receptor in chemosensors for a wide range of biologically important species has been extensively reported. The reversible covalent interaction of boronic acid with cis 1,2 or 1,3 diols to form five or six membered cyclic esters, respectively, has proven to be sufficiently strong and enables the binding of saccharides at mM or sub mM levels. 6,7 Based on this binding principle, a number of fluorescence sensors have been designed for detecting sugars, 8,9 aminosugars, 10,11 cell surface glycans, 12-14 etc. However, organic fluorescence sensors are expensive, involve a multistep synthesis process and are normally unworthy for practical promotion and application. By virtue of favorable optical properties and surface functionality, carbon nanomaterial-based sensing systems have been successfully applied for glucose sensing. 15 For instance, Qiu et al. have reported a fluorescence sensor constituting a combination of anionic graphene quantum dots and bipyridinum salts for detection of sugars and other saccharides. 16 This method offers a simple mix-and-detect protocol for rapid detection of glucose and other saccharides, but it lacks selectivity. Later, two different protocols were published where boronic acid functio-nalized carbon dot and graphene quantum dots have been used for selective sensing of glucose. 17,18 Although boronic acid is well-known to bind diol readily to act as a carbohydrate receptor, several boronic acid-based sensors failed to recognize D-glucosamine, other aminosugars, glycans, etc. due to their low selectivities. On the other hand, glucosamine, an aminosugar, has been used over the years as a dietary supplement for the treatment of osteoarthritis in spite of its indistinct pharmacokinetics and pharmacodynamics. 19-21 In addition to its chondroprotective action, glucosamine has been believed to exert anticancer action for more than five decades. It shows growth inhibitory activity in cancer cells via affecting proteasomal activity. 22 There are also numerous contradictory findings on the efficiency of D-glucosamine in treating rheumatoid arthritis and gastric ulcers. 23-26 The development of luminescent quantum dot-based D-glucosamine sensors with a high sensitivity and selectivity will provide novel approaches for early clinical diagnosis of most D-glucosamine related diseases. Thus, it is of both biological and biomedical significance to construct sensing devices for probing D-glucosamine at normal cellular concentrations (1-2 mM). To date, very few fluorescence sensors have been reported for D-glucosamine, including monoaza-18-crown-6 ether and boronic acid as the receptor units, 27 metal complexes, 28 graphene oxide,

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

Analytica Chimica Acta : Elsevier , 2019

h i g h l i g h t s g r a p h i c a l a b s t r a c t A simple design of a carbon quantum dot bas... more h i g h l i g h t s g r a p h i c a l a b s t r a c t A simple design of a carbon quantum dot based fluorescence sensor for the detection of fluoride ion has been developed by integrating boronic acid functionalized carbon quantum dot and dopamine. This sensor works in total aqueous medium with a limit of detection 0.7 pM which is lowest among reported values. The applicability of our sensing protocol has also been explored in real samples like tap water, soda water and 3 human serum samples. Due to low detection limit this sensor is able detect fluoride in intracellular environment. Keywords: Fluorescence Carbon quantum dot Photo electron transfer Boron-fluoride interaction a b s t r a c t 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 dopa-mine. 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 À is achieved due to high reactivity of F À 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.

Enhanced Photodegradation of Organic Pollutants by Carbon Quantum Dot (CQD) Deposited Fe 3 O 4 @mTiO 2 Nano-Pom-Pom Balls

Industrial & Engineering Chemistry Research : American Chemical Society , 2016

Highly water dispersible, superparamagnetic carbon quantum dot (CQD) deposited Fe 3 O 4 @mTiO 2 p... more Highly water dispersible, superparamagnetic carbon quantum dot (CQD) deposited Fe 3 O 4 @mTiO 2 pom-pom balls have been prepared by a simple hydrothermal method. The effective deposition of carbon dots expands the light absorption of mTiO 2 from the UV to visible region. The results of photocurrent measurement reveal that an optimum deposition of C-dot at 20 wt % significantly increases the photocurrent density. High surface area and extended conjugation of carbon dots enhance the adsorption of organic pollutants. The active species generated in the photocatalytic system were also detected through trapping of radicals and holes in the presence of various scavengers. In a comparison with a conventional photocatalyst such as Degussa P25, the developed heterojunction shows much higher degradation efficiency for ciprofloxacin, methylene blue, quinalphos, and 4-nitrophenol under visible light. The light upconversion properties of uniformly deposited carbon quantum dots could be a reason for higher visible light catalytic activity of the synthesized magnetically recoverable hybrid photocatalyst.

Rapid "turn-on" detection of atrazine using highly luminescent N-doped carbon quantum dot

Sensors and Actuators B : Elsevier , 2018

Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for ... more Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for the detection of herbicide atrazine. Nitrogen doped carbon quantum dot with PLQY 28% has been prepared from hydrothermal treatment of orthophenylene diamine. The turn-on fluorescence of the probe on addition of atrazine is attributed to aggregation induced fluorescence enhancement of amine functionalized carbon dot. The hydrogen bonding interaction of surface amine groups of carbon dot probe and atrazine makes the probe selective and ultrasensitive towards atrazine even in presence of other pesticides and metal ions. The limit of detection for atrazine sensing was found to be 3 pM, which is the lowest among all reported methods for the detection of atrazine. Due to low detection limit the utility of the developed sensor has also been explored in real agricultural samples. Owing to the excellent luminescence property and photostability this fluorescent probe can also be utilised to detect atrazine in bacterial cell by imaging.

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

Langmuir: American Chemical Society , 2016

Judicious combination of fluorescence and magnetic properties along with ample drug loading capac... more 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 (r 2) 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. ■ INTRODUCTION Development of intelligent stimuli responsive theranostic system that can detect and treat cancer at its early stage is an emerging area in the field of nanobiotechnology. 1 In this regard synthesis of multifunctional particulate drug delivery agents combined with bimodal MRI/optical bioimaging detection is significant. 2,3 Particularly, composite nanoparticles combining fluorescence and magnetic components have received much attention because they ally the high sensitivity of the fluorescence phenomenon to the high spatial resolution of MRI. 4−7 For example, the strong superparamagnetism of magnetic nanoparticles allows the visualization of target diseased tissue in any part of the body using T 2-weighted magnetic resonance imaging. 8 Additionally, the quantum confinement effect exhibited by semiconductor quantum dots allows ultrasensitive and multiplexed fluorescence imaging both in vitro and in vivo, providing new tools to understand cellular processes related to cancer development. 9 On the other hand, nanosystems can carry small payloads of anticancer drugs and deliver them directly to a tumor. These multiple components can be combined perceptively into a single matrix system to administer therapeutic and diagnostic functions in a single dose. In this regard mesoporous silica is extensively investigated as a matrix system which can sustain a number of payloads like imaging agents (e.g., organic dyes, quantum dots [QDs], upconversion particles [UCNPs], MRI contrast agents, CT contrast agents, etc.) and therapeutic agents (anticancer drugs, DNA, small interfering RNA [siRNA], proteins, hyperthermia-inducing nanoparticles, ROS-generating agents, etc.). 10−12 Mesoporous silica based nanoparticles have been explored as stimuli-responsive nanosystems using different capping strategies such as varieties of nanovalves, thermosensitive polymers to block the pores. The opening of mesopores and subsequent release of therapeutic cargoes are finely controlled by external stimuli such as pH and temperature. 13−15 However, this tedious post-synthetic capping, incorporation of therapeutic cargoes and surface modification processes, limit the industrial translation of the protocol. Alternatively, carbon nanomaterials such as carbon nanotubes, 16 fullerene, 17 graphene oxide, 18 and carbon dots 19 are leading theranostic materials due to their larger surface area and low toxicity. The intrinsic luminescent property of these materials has been unanimously explored in bioimaging and monitoring curative responses. 20 At the same time, high anisotropy of nanosized cobalt ferrite nanoparticles resulting in high proton relaxivity allows the visualization of target diseased tissue using T 2-weighted magnetic resonance

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

Analytica Chimica Acta, 2019

A simple fluorescence turn on sensor for the detection of fluoride ion in totally aqueous medium ... more 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 Ftowards 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.

Rapid “turn-on” detection of atrazine using highly luminescent N-doped carbon quantum dot

Sensors and Actuators B: Chemical, 2018

Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for ... more Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for the detection of herbicide atrazine. Nitrogen doped carbon quantum dot with PLQY 28% has been prepared from hydrothermal treatment of orthophenylene diamine. The turn-on fluorescence of the probe on addition of atrazine is attributed to aggregation induced fluorescence enhancement of amine functionalized carbon dot. The hydrogen bonding interaction of surface amine groups of carbon dot probe and atrazine makes the probe selective and ultrasensitive towards atrazine even in presence of other pesticides and metal ions. The limit of detection for atrazine sensing was found to be 3 pM, which is the lowest among all reported methods for the detection of atrazine. Due to low detection limit the utility of the developed sensor has also been explored in real agricultural samples. Owing to the excellent luminescence property and photostability this fluorescent probe can also be utilised to detect atrazine in bacterial cell by imaging.

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

Langmuir : the ACS journal of surfaces and colloids, May 8, 2018

Construction of a theranostic agent which integrates multiple modalities with different functions... more 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 Lewis (SL) enables targeted drug release and excellent fluorescence imaging of SL overexpressed HePG2 cancer cells. The r and r relaxivities of the material are found to be 10 and 165 mM s which is comparable to commercially available m...

Enhanced Photodegradation of Organic Pollutants by Carbon Quantum Dot (CQD) Deposited Fe3O4@mTiO2 Nano-Pom-Pom Balls

Industrial & Engineering Chemistry Research, 2016

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

Langmuir, 2016

Judicious combination of fluorescence and magnetic properties along with ample drug loading capac... more 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 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 resorcinol-formaldehyde precursor. The mesoporous matrix shows control release of 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-1S-1. The multicolour-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.

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

Langmuir, 2019

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

J. Mater. Chem. B, 2017

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

Langmuir : American Chemical Society , 2019

Use of nanomaterials blessed with both therapeutic and diagnostic properties is a proficient stra... more 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 λ ex = 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

Langmuir : American Chemical Society , 2018

Construction of a theranostic agent which integrates multiple modalities with different functions... more 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 Lewis a (SL a) enables targeted drug release and excellent fluorescence imaging of SL a overexpressed HePG2 cancer cells. The r 1 and r 2 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 luminescent, heteroatom-doped carbon quantum dots for ultrasensitive sensing of glucosamine and targeted imaging of liver cancer cells

Journal of Materials Chemistry B : Royal Society , 2017

A novel fluorescent boronate nanoprobe has been synthesized by judiciously doping boron, nitrogen... more 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 mM. The developed nanoprobe shows very low cytotoxicity. More interestingly, boronic acid located on the surface of BNSCQD offers molecular recognition sites for the sialyl Lewis a 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. Fluorescence sensing has been emerging as an efficient detection method because of its high sensitivity and spatiotemporal resolution. 1-5 The effectiveness of boronic acid as a receptor in chemosensors for a wide range of biologically important species has been extensively reported. The reversible covalent interaction of boronic acid with cis 1,2 or 1,3 diols to form five or six membered cyclic esters, respectively, has proven to be sufficiently strong and enables the binding of saccharides at mM or sub mM levels. 6,7 Based on this binding principle, a number of fluorescence sensors have been designed for detecting sugars, 8,9 aminosugars, 10,11 cell surface glycans, 12-14 etc. However, organic fluorescence sensors are expensive, involve a multistep synthesis process and are normally unworthy for practical promotion and application. By virtue of favorable optical properties and surface functionality, carbon nanomaterial-based sensing systems have been successfully applied for glucose sensing. 15 For instance, Qiu et al. have reported a fluorescence sensor constituting a combination of anionic graphene quantum dots and bipyridinum salts for detection of sugars and other saccharides. 16 This method offers a simple mix-and-detect protocol for rapid detection of glucose and other saccharides, but it lacks selectivity. Later, two different protocols were published where boronic acid functio-nalized carbon dot and graphene quantum dots have been used for selective sensing of glucose. 17,18 Although boronic acid is well-known to bind diol readily to act as a carbohydrate receptor, several boronic acid-based sensors failed to recognize D-glucosamine, other aminosugars, glycans, etc. due to their low selectivities. On the other hand, glucosamine, an aminosugar, has been used over the years as a dietary supplement for the treatment of osteoarthritis in spite of its indistinct pharmacokinetics and pharmacodynamics. 19-21 In addition to its chondroprotective action, glucosamine has been believed to exert anticancer action for more than five decades. It shows growth inhibitory activity in cancer cells via affecting proteasomal activity. 22 There are also numerous contradictory findings on the efficiency of D-glucosamine in treating rheumatoid arthritis and gastric ulcers. 23-26 The development of luminescent quantum dot-based D-glucosamine sensors with a high sensitivity and selectivity will provide novel approaches for early clinical diagnosis of most D-glucosamine related diseases. Thus, it is of both biological and biomedical significance to construct sensing devices for probing D-glucosamine at normal cellular concentrations (1-2 mM). To date, very few fluorescence sensors have been reported for D-glucosamine, including monoaza-18-crown-6 ether and boronic acid as the receptor units, 27 metal complexes, 28 graphene oxide,

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

Analytica Chimica Acta : Elsevier , 2019

h i g h l i g h t s g r a p h i c a l a b s t r a c t A simple design of a carbon quantum dot bas... more h i g h l i g h t s g r a p h i c a l a b s t r a c t A simple design of a carbon quantum dot based fluorescence sensor for the detection of fluoride ion has been developed by integrating boronic acid functionalized carbon quantum dot and dopamine. This sensor works in total aqueous medium with a limit of detection 0.7 pM which is lowest among reported values. The applicability of our sensing protocol has also been explored in real samples like tap water, soda water and 3 human serum samples. Due to low detection limit this sensor is able detect fluoride in intracellular environment. Keywords: Fluorescence Carbon quantum dot Photo electron transfer Boron-fluoride interaction a b s t r a c t 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 dopa-mine. 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 À is achieved due to high reactivity of F À 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.

Enhanced Photodegradation of Organic Pollutants by Carbon Quantum Dot (CQD) Deposited Fe 3 O 4 @mTiO 2 Nano-Pom-Pom Balls

Industrial & Engineering Chemistry Research : American Chemical Society , 2016

Highly water dispersible, superparamagnetic carbon quantum dot (CQD) deposited Fe 3 O 4 @mTiO 2 p... more Highly water dispersible, superparamagnetic carbon quantum dot (CQD) deposited Fe 3 O 4 @mTiO 2 pom-pom balls have been prepared by a simple hydrothermal method. The effective deposition of carbon dots expands the light absorption of mTiO 2 from the UV to visible region. The results of photocurrent measurement reveal that an optimum deposition of C-dot at 20 wt % significantly increases the photocurrent density. High surface area and extended conjugation of carbon dots enhance the adsorption of organic pollutants. The active species generated in the photocatalytic system were also detected through trapping of radicals and holes in the presence of various scavengers. In a comparison with a conventional photocatalyst such as Degussa P25, the developed heterojunction shows much higher degradation efficiency for ciprofloxacin, methylene blue, quinalphos, and 4-nitrophenol under visible light. The light upconversion properties of uniformly deposited carbon quantum dots could be a reason for higher visible light catalytic activity of the synthesized magnetically recoverable hybrid photocatalyst.

Rapid "turn-on" detection of atrazine using highly luminescent N-doped carbon quantum dot

Sensors and Actuators B : Elsevier , 2018

Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for ... more Nitrogen doped carbon quantum dot based highly selective luminescent probe has been designed for the detection of herbicide atrazine. Nitrogen doped carbon quantum dot with PLQY 28% has been prepared from hydrothermal treatment of orthophenylene diamine. The turn-on fluorescence of the probe on addition of atrazine is attributed to aggregation induced fluorescence enhancement of amine functionalized carbon dot. The hydrogen bonding interaction of surface amine groups of carbon dot probe and atrazine makes the probe selective and ultrasensitive towards atrazine even in presence of other pesticides and metal ions. The limit of detection for atrazine sensing was found to be 3 pM, which is the lowest among all reported methods for the detection of atrazine. Due to low detection limit the utility of the developed sensor has also been explored in real agricultural samples. Owing to the excellent luminescence property and photostability this fluorescent probe can also be utilised to detect atrazine in bacterial cell by imaging.

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

Langmuir: American Chemical Society , 2016

Judicious combination of fluorescence and magnetic properties along with ample drug loading capac... more 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 (r 2) 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. ■ INTRODUCTION Development of intelligent stimuli responsive theranostic system that can detect and treat cancer at its early stage is an emerging area in the field of nanobiotechnology. 1 In this regard synthesis of multifunctional particulate drug delivery agents combined with bimodal MRI/optical bioimaging detection is significant. 2,3 Particularly, composite nanoparticles combining fluorescence and magnetic components have received much attention because they ally the high sensitivity of the fluorescence phenomenon to the high spatial resolution of MRI. 4−7 For example, the strong superparamagnetism of magnetic nanoparticles allows the visualization of target diseased tissue in any part of the body using T 2-weighted magnetic resonance imaging. 8 Additionally, the quantum confinement effect exhibited by semiconductor quantum dots allows ultrasensitive and multiplexed fluorescence imaging both in vitro and in vivo, providing new tools to understand cellular processes related to cancer development. 9 On the other hand, nanosystems can carry small payloads of anticancer drugs and deliver them directly to a tumor. These multiple components can be combined perceptively into a single matrix system to administer therapeutic and diagnostic functions in a single dose. In this regard mesoporous silica is extensively investigated as a matrix system which can sustain a number of payloads like imaging agents (e.g., organic dyes, quantum dots [QDs], upconversion particles [UCNPs], MRI contrast agents, CT contrast agents, etc.) and therapeutic agents (anticancer drugs, DNA, small interfering RNA [siRNA], proteins, hyperthermia-inducing nanoparticles, ROS-generating agents, etc.). 10−12 Mesoporous silica based nanoparticles have been explored as stimuli-responsive nanosystems using different capping strategies such as varieties of nanovalves, thermosensitive polymers to block the pores. The opening of mesopores and subsequent release of therapeutic cargoes are finely controlled by external stimuli such as pH and temperature. 13−15 However, this tedious post-synthetic capping, incorporation of therapeutic cargoes and surface modification processes, limit the industrial translation of the protocol. Alternatively, carbon nanomaterials such as carbon nanotubes, 16 fullerene, 17 graphene oxide, 18 and carbon dots 19 are leading theranostic materials due to their larger surface area and low toxicity. The intrinsic luminescent property of these materials has been unanimously explored in bioimaging and monitoring curative responses. 20 At the same time, high anisotropy of nanosized cobalt ferrite nanoparticles resulting in high proton relaxivity allows the visualization of target diseased tissue using T 2-weighted magnetic resonance