Модификација угљеничних нанокомпозита електромагнетним зрачењем за биомедицинску примену Modification de nanocomposites de carbone par rayonnement électromagnétique pour des applications biomédicales

Microbial contamination is a very important issue worldwide which affects multiple aspects of our everyday life: health care, water purification systems, food storage, etc. Traditional antibacterial therapies are becoming less efficient because inadequate use and disposal of antibiotics have triggered mutations in bacteria that have resulted in many antibiotic-resistant strains. Therefore, it is of great importance to develop new antibacterial materials that will effectively combat both planktonic bacteria and their biofilms in an innovative manner. In this context, the goal of this thesis was to develop two different carbon/polymer nanocomposites (reduced graphene oxide/polyethylenimine and carbon quantum dots/polyurethane) which exhibit excellent antibacterial properties through two different effects: photothermal and photodynamic. Electromagnetic irradiation was used (near-infrared laser radiation or gamma rays) in these experiments, for the purpose of triggering the photothermal effect and enhancing the photodynamic effect of the nanocomposites. In the first experimental part of this thesis, a simple and efficient strategy for bacteria capture and their eradication through photothermal killing is presented. The developed device consists of a flexible Kapton interface modified with gold nanoholes (Au NH) substrate, coated with reduced graphene oxide-polyethyleneimine thin films (K/Au NH/rGO-PEI). The K/Au NH/rGO–PEI device was efficient in capturing and eliminating both planktonic Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria after 10 min of NIR (980 nm) irradiation. Additionally, the developed device could effectively destroy and eradicate Staphylococcus epidermidis (S. epidermidis) biofilms after 30 min of irradiation. In the second experimental part, the preparation of a hydrophobic carbon quantum dots/polyurethane (hCQD-PU) nanocomposite with improved antibacterial properties caused by gamma-irradiation pre-treatment is presented. Hydrophobic quantum dots (hCQDs), which are able to generate reactive oxygen species (ROS) upon irradiation with low power blue light (470 nm), were incorporated in the polyurethane (PU) polymer matrix to form a photoactive nanocomposite. Different doses of gamma irradiation (1, 10 and 200 kGy) were applied to the formed nanocomposite in order to modify its physical and chemical properties and improve its antibacterial efficiency. The pre-treatment by gamma-irradiation significantly improved antibacterial properties of the nanocomposite, and the best result was achieved for the irradiation dose of 200 kGy. In this sample, total bacteria elimination was achieved after 15 min of irradiation by blue light, for Gram-positive and Gram-negative strains.Контаминација бактеријама је веома распрострањен проблем који утиче на много различитих аспеката свакодневног живота: здравство, системе за пречишћавање воде, чување хране итд. Традиционалне антибактеријске терапије су постале мање ефикасне, услед неадекватне употребе и одлагања неискоришћених антибиотика, што је довело до мутација бактерија и резултовало појавом многобројних антибиотски отпорних врста. Стога је веома важно да се развију нови антибактеријски материјали који би се ефикасно борили како са планктонским бактеријама тако и са њиховим биофилмовима, на иновативан начин. Сходно томе, циљ ове дисертације био је развијање два различита нанокомпозита на бази угљеника и полимера (редуковани графен оксид/полиетиленимин и угљеничне квантне тачке/полиуретан), који испољавају одлична антибактеријска својства кроз два различита ефекта: фотодинамички и фототермални. Електромагнетно зрачење (блиско инфрацрвено и гама зрачење) коришћено је у оба експеримента, у сврху активирања фототермалног и побољшања фотодинамичког ефекта. У првом експерименталном делу ове дисертације представљена је једноставна и ефикасна стратегија за хватање бактерија и њихово искорењивање фототермалним убијањем. Развијени уређај се састоји од флексибилног Каптон интерфејса модификованог са златним наношупљинама (Au NH), који је затим обложен танким слојем редукованог графен оксидполиетиленимина (K/Au NH/rGO–PEI). K/Au NH/rGO–PEI уређај је врло ефикасан у хватању и уклањању планктонских Грам-позитивних Staphylococcus aureus (S. aureus) и Грамнегативних Escherichia coli (E. coli) бактерија након 10 мин зрачења ласером у блиској инфрацрвеној области (980 nm). Поред тога, развијени уређај може ефикасно уништити и искоренити биофилмове Staphylococcus epidermidis (S. epidermidis) након 30 минута озрачивања. У другом експерименталном делу представљена је припрема нанокомпозита који се састоји од хидрофобних угљеничних квантних тачака и полиуретана (hCQD-PU) са побољшаним антибактеријским својствима узрокованим третманом гама зрачењем. Хидрофобне квантне тачке (енг. hydrophobic carbon quantum dots - hCQD), које су способне да стварају реактивне врсте кисеоника (reactive oxygen species – ROS) након зрачења видљивом плавом светлошћу мале снаге (470 nm), уграђене су у полиуретански (PU) полимер матрикс како би формирали фотоактивни нанокомпозит. Формирани нанокомпозит је затим изложен различитим дозама гама зрачења (1, 10 и 200 kGy) како би се изменила његова физичка и хемијска својства и побољшала његова антибактеријска ефикасност. Третман гама зрачењем значајно је побољшао антибактеријска својства нанокомпозита, а најбољи резултат је постигнут за дозу зрачења од 200 kGy. У овом узорку постигнута је потпуна елиминација бактерија након 15 мин зрачења плавом светлошћу, за Грам-позитивне и Грам-негативне сојеве

Synthesis and Characterization of Ag Doped TiO2, CdS, ZnS Nanoparticles for Photocatalytic, Toxic Ions Detection, and Antimicrobial Applications

The progresses of nanoparticles (NPs) research have been passed through several advancements, such as simple spherical NPs to different shapes (anisotropic), hollow, core/shell, doped, movable core/shell or yolk shell, etc. These NPs have more advanced properties in several applications, such as catalysis, biomedical, electronics, solar cells, sensors, and so on because of high surface area to volume ratio, the presence of more loosely bound surface atoms, etc. When the particles are made of multimaterials it’s not only show improved property of the main material but also developed multifunctionality. Because of these reasons the multimaterials NPs are continuously drawing significant research attentions in the recent years. Under the multi-materials nanoparticles category, doped nanoparticles are also considered as an important class. This thesis is focused on synthesis, characterization, properties, and applications of Ag doped semiconductor nanoparticles. More specifically, TiO2, CdS, and ZnS were considered as the host materials and Ag as the dopant to form single, core/shell, hollow, and hollow bi-layer NPs for the applications in visible light induced photocatalytic degradation of organic compounds (nitrobenzene, metronidazole, methylene blue dye), antifungal agent (against Fusarium solani and Venturia inaquaelis), and sensor for the detection of arsenic and fluoride ions in aqueous media. The abstracts of the studied works are organized sequentially in the following paragraphs. Continuous increasing consumption of antibiotics in health care results to increase concentration of these compounds in surface water through wastewater treatment systems, which in turn, cause adverse effects on the aquatic ecosystems of the receiving water bodies, because of the intrinsic biological activity of these compounds. However, there are limited efforts on remediation of water pollution because of antibiotics using an effective and clean technology. In this study, photocatalytic activity of TiO2, CdS, and ZnS semiconductor nanoparticles were employed to degrade the metronidazole antibiotic in visible light irradiation. The particle size of pure TiO2, CdS, and ZnS was 33.39 ± 1.67, 4.06 ± 0.63, and 5.85 ± 0.5 nm, respectively. The particle size of Ag doped TiO2, CdS, and ZnS was 27.6 ± 2.08, 3.44 ± 0.76, and 4.91 ± 0.45 nm, respectively. The maximum degradation efficiencies of the pure TiO2, CdS and ZnS nanoparticles were 80.78, 82.46, and 81.66%, respectively. These particles were also modified by silver doping to improve its degradation efficiency. Doping of silver greatly enhanced the degradation efficiency of these nanoparticles. The particular concentrations of silver dopant were 1.00, 1.5, and 1.25% for TiO2, CdS, and ZnS nanoparticles for achieving the maximum degradation efficiency and the corresponding maximum degradation efficiencies were 94.39, 94.9%, and 95.11%. The basic mechanism of doping and the photocatalytic processes was explored in detail. A kinetic study of the degradation reaction shows first order kinetics fits well for all three cases. The reusability and stability of these photocatalyst were confirmed by the cyclic degradation test. In addition to the antibiotics, contamination of water because of other organic pollutants, especially synthetic dyes, causes severe environmental problems because of its toxic nature to microorganisms, aquatic life, and human beings. In this regard, an effective and clean remediation process for the remediation of dye contaminated effluent waters becomes more demanding to reduce the environmental impact. This section reports the photocatalytic behaviour of methylene blue using pure and silver doped semiconductor heterogeneous nanocatalysts (TiO2, CdS, and ZnS) under visible light. The photodegradation studies show there is a significant enhancement in degradation efficiency of all three nanoparticles after silver doping. For all nanoparticles, there is an optimum doping concentration to get the maximum degradation efficiency, which again depends on the material. The maximum degradation efficiencies for the three Ag doped TiO2, ZnS, and CdS nanoparticles were 95.9, 95.33, and 94.99% for 1.00, 1.25, and 1.50% Ag, respectively. The first order rate constant value of 1.00% Ag doped TiO2, 1.5% Ag doped CdS, and 1.25% Ag doped ZnS is 5.21, 5.72, and 7.71 times higher compared to their respective pure nanoparticles. The maximum degradation efficiency with minimum doping concentration among all three materials studied here was again found for TiO2. Further, silver doped hollow TiO2 (Ag-h-TiO2) nanoparticles were also synthesized by a sacrificial core (AgBr) method to enhance the surface area for higher photocatalytic activity. The Ag doping and the core removal was done simultaneously during the dissolution of the core in (NH4)OH solution. The mean particle size of synthesized Ag-h-TiO2 nanoparticles was 17.76 ± 2.85 nm with the wall thickness ~2.5 nm. The hollow structured nanoparticles have the specific surface area of 198.3 m2/g, where as solid TiO2 nanoparticles have the specific surface area of 95.1 m2/g. The suitability of this synthesized hollow nanoparticles as photocatalyst were tested for the photocatalytic degradation of three important different classes of organic compounds such as nitrobenzene (NB), metronidazole (MTZ) antibiotic, and methylene blue dye (MBD) in aqueous solution under irradiation of visible light. The maximum NB degradation was obtained 95.5%, and the metronidazole degradation efficiency was found to be 96.55 and 94.77% under the irradiation of visible light for the initial MTZ concentration of 15 and 30 mg/L with catalyst dose of 0.5 g/L. Photodegradation studies show there is a significant enhancement of the degradation efficiency of the TiO2 after the hollow structure formation and silver doping. The recycling tests of the catalysts show only ~ 10% decrease in efficiency for NB and MTZ degradation after sixth cycle of reuse. The light emission capacity in terms of quantum yield (QY) is enhanced by 18.7% for Ag-h-TiO2 than that of pure TiO2 nanoparticles. The above mentioned hollow TiO2 NPs were also used as photoinduced antifungal agent. The chemical based pesticides are widely used in agricultural farming to protect crops from insect infestation and diseases. However, the excessive use of highly toxic pesticides causes several human health (neurological, tumour, cancer) and environmental problems. So, nanoparticles based green pesticides are of special importance in recent years. Antifungal activities of the pure and Ag doped (solid and hollow) TiO2 nanoparticles were studied against two potent phytopathogens, Fusarium solani (causing Fusarium wilt disease to potato, tomato etc.) and Venturia inaquaelis (causing apple scab disease) and found hollow nanoparticles are more effective than other two. The antifungal activities of the nanoparticles enhanced further under visible light exposure against these two phytopathogens. Fungicidal effect of the nanoparticles depends on different parameters, , such as particle concentration, and intensity of visible light. The minimum inhibitory dose of the nanoparticles for V.inaquaelis and F.solani are 0.75 and 0.43 mg/plate. Presence of Ag as a dopant helps to the formation of stable Ag-S and di-sulfide bond (R-S-S-R) in cellular protein, which leads to the cell damage. During photocatalysis generated OH radicals loosen the cell wall structure and finally lead to the cell death. The mechanisms of fungicidal effect of nanoparticles against these two phytopathogens are supported by biuret and triphenyl tetrazolium chloride analyses, and field emission electron microscopy. Apart from the fungicidal effect, at very low dose (0.015 mg/plate) the nanoparticles are successfully arrest production of toxic napthoquinone pigment for F.solani which is related to the fungal pathogenecity. The nanoparticles are found to be effective to protect spoiling of potato affected by F.solani or other fungus. The doped nanoparticles can also be used effectively for the easy detection of toxic ions in water. In this regard, fluoride ion detection has taken a considerable research interest in recent years because of its typical nature. It is an essential anion for biological and medical systems, as well as for some industrial applications. But, the fluoride ions above its permissible level can cause different diseases, such as fluorosis, urolithiasis, kidney failure, cancer, and even leading to death. Because of this reason a simple and low cost method is highly desirable for the detection of fluoride ion. In this study a fluorometric method based on Ag-CdS/Ag-ZnS nanoparticle is developed for the fluoride ion detection. The developed nanoparticles were of size range 5.92 ± 0.76 nm with shell layer of 0.75 nm and it showed the quantum yield of 77.57%. The method was tested in aqueous solution at different pH. The selectivity and sensitivity of the fluorescence probe was checked in the presence of other anions (Cl-, Br-, I-, OH-, NO3- SO42-, HCO3-, HPO42-, CH3COO-, H2PO4-). The fluoride ion concentration was varied in the rage 190 – 22,800 μg/L and the lower detection limit was obtained as 99.7 μg/L. Arsenic poisoning from drinking water is also an important global issue in recent years. Because of high level toxicity of arsenic to human health, an easy, inexpensive, and low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for easy fluorometric determination of As(III) ions in aqueous phase. The hollow bi-layer structures are synthesized by a sacrificial core method using AgBr as the sacrificial core and the core is removed by dissolution in ammonium hydroxide solution. The synthesized nanoparticles were characterized by using different instrumental techniques. The particle size of Ag-h-CdS/ZnS nanoparticles is ~ 76.02 ± 2.47 nm with the shell thickness of CdS layer is 1.5 nm and ZnS layer is 1.8 nm. The QY of the Ag-h-CdS/ZnS nanoparticles is 88.14%. A good linear relationship is obtained between fluorescence quenching intensity and the As(III) concentration in the range of 750 – 22500 ng/L at neutral pH with a limit of detection as low as 226 ng/L

Synthesis of fluorescent carbon nanoparticles (CNPs) and their applications in drug delivery

Nanomedicine requires intelligent and non-toxic nanomaterials for real clinical applications. Carbon materials possess interesting properties but with some limitations due to toxic effects. Interest in carbon nanoparticles (CNPs) is increasing because they are considered green materials with tunable optical properties, overcoming the problem of toxicity associated with quantum dots or nanocrystals, and can be utilized as smart drug delivery systems. Using black tea as a raw material, we synthesized CNPs with a narrow size distribution, tunable optical properties covering visible to deep red absorption, non-toxicity and easy synthesis for large-scale production. We utilized these CNPs to label subcellular structures such as exosomes. More importantly, these new CNPs can escape lysosomal sequestration and rapidly distribute themselves in the cytoplasm to release doxorubicin (doxo) with better efficacy than the free drug. The release of doxo from CNPs was optimal at low pH, similar to the tumour microenvironment. These CNPs were non-toxic in mice and reduced the tumour burden when loaded with doxo due to an improved pharmacokinetics profile. In summary, we created a new delivery system that is potentially useful for improving cancer treatments and opening a new window for tagging microvesicles utilized in liquid biopsies

A Novel “Off-On” Fluorescent Probe Based on Carbon Nitride Nanoribbons for the Detection of Citrate Anion and Live Cell Imaging

A novel fluorescent “off-on” probe based on carbon nitride (C3N4) nanoribbons was developed for citrate anion (C6H5O73−) detection. The fluorescence of C3N4 nanoribbons can be quenched by Cu2+ and then recovered by the addition of C6H5O73−, because the chelation between C6H5O73− and Cu2+ blocks the electron transfer between Cu2+ and C3N4 nanoribbons. The turn-on fluorescent sensor using this fluorescent “off-on” probe can detect C6H5O73− rapidly and selectively, showing a wide detection linear range (1~400 μM) and a low detection limit (0.78 μM) in aqueous solutions. Importantly, this C3N4 nanoribbon-based “off-on” probe exhibits good biocompatibility and can be used as fluorescent visualizer for exogenous C6H5O73− in HeLa cells

A Novel “Off-On” Fluorescent Probe Based on Carbon Nitride Nanoribbons for the Detection of Citrate Anion and Live Cell Imaging

A novel fluorescent “off-on” probe based on carbon nitride (C3N4) nanoribbons was developed for citrate anion (C6H5O73−) detection. The fluorescence of C3N4 nanoribbons can be quenched by Cu2+ and then recovered by the addition of C6H5O73−, because the chelation between C6H5O73− and Cu2+ blocks the electron transfer between Cu2+ and C3N4 nanoribbons. The turn-on fluorescent sensor using this fluorescent “off-on” probe can detect C6H5O73− rapidly and selectively, showing a wide detection linear range (1~400 μM) and a low detection limit (0.78 μM) in aqueous solutions. Importantly, this C3N4 nanoribbon-based “off-on” probe exhibits good biocompatibility and can be used as fluorescent visualizer for exogenous C6H5O73− in HeLa cells