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

Gamma irradiation as a tool for modification of graphene oxide-silver nanowires composites

Graphene oxide (GO) was produced using the Hummers' method while silver nanowires (AgNWs) were obtained by polyol synthesis. Composite was produced by simple mixing of GO and AgNWs dispersions. The composite was produced in a form of free/standing films by vacuum filtration and exposed to gamma irradiation in an oxygen-free atmosphere. After irradiation, without any additional cleaning, the structure, morphology and electrical properties were investigated. Gamma irradiation was shown to be an efficient tool to induce a chemical reduction of GO, and it was able to improve the electrical conductivity of produced composites. Due to avoiding the usage of reagents and solvents, this method belongs to green chemical approaches

The influence of tip sonication on structural and morphological properties of graphene

Although ultrasound is frequently used to disperse carbon nanomaterials in suitable solvents, the propagation of high-amplitude ultrasonic vibrations from the tip sonicator was found to be aggressive and has the potential to break down graphene sheets. Here, the effects of tip sonication time on structural and morphological properties of two types of graphene (graphene oxide and electrochemically exfoliated graphene) was investigated by UV-vis spectroscopy and Atomic Force Microscopy. It was found that the structural composition of the graphene was not affected by ultrasounds emitted from the tip sonicator even for the prolonged period of sonication (60 min). Microscopy analysis showed an increased portion of smaller graphene sheets in the sonicated samples for both types of graphene as a result of graphene sheet fragmentation caused by tip sonication

Using straw-bales for energy saving

Savremeno društvo se suočava sa novim i drugačijim izazovima. Obnovljivih resursa je sve manje. Životna sredina je zagađena. Potrebe savremenog čoveka su sve veće i njihovo zadovoljenje zahteva sve više energije i materijalnih resursa. Proizvodnja materijala koji se koriste za izgradnju objekata zahteva prirodne resurse i veliku količinu energije. U eksploataciji objekata postoji potreba za grejanjem i hlađenjem, za šta je takođe neophodna energija. Moguće rešenje je upotreba prirodnih materijala koji su tradicionalno bili primenjivani vekovima, a koji su potisnuti razvojem industrije i širokom primenom betona i čelika. Slama, kao materijal, postoji više od 2000 godina i predstavlja nusproizvod pri uzgajanju pšenice, raži, pirinča. Proizvodnja slame ne zahteva primarnu energiju. Karakteristike balirane slame su takve da nije potrebna dodatna termička i zvučna izolacija. Primenom balirane slame moguće je materijalom, koji je gotovo besplatan, postići značajne uštede energije i pomoći u očuvanju životne sredine.Modern society is faced with new challenges. Renewable resources are disappearing. The environment is polluted. The production of materials for construction requires natural resources and a great amount of energy. In the exploitation of buildings a lot of energy is used for heating and cooling. Possible solution lies in the application of natural materials that were traditionally used for centuries and were suppressed by the industry’s development and the extended use of concrete and steel. Straw, as a material, exists for more than 2000 years. It is a by-product in the growing of wheat, rye, and rice. The production of straw doesn’t need primary energy. The characteristics of straw-bales are such that no additional thermal and sound insulation is needed. With the application of straw-bales, a material that is almost free, it is possible to achieve significant savings in energy and to help preserve the environment

Antibacterial and Antibiofouling Activities of Carbon Polymerized Dots/Polyurethane and C60/Polyurethane Composite Films

The cost of treatment of antibiotic-resistant pathogens is on the level of tens of billions of dollars at the moment. It is of special interest to reduce or solve this problem using antimicrobial coatings, especially in hospitals or other healthcare facilities. The bacteria can transfer from medical staff or contaminated surfaces to patients. In this paper, we focused our attention on the antibacterial and antibiofouling activities of two types of photodynamic polyurethane composite films doped with carbon polymerized dots (CPDs) and fullerene C60. Detailed atomic force, electrostatic force and viscoelastic microscopy revealed topology, nanoelectrical and nanomechanical properties of used fillers and composites. A relationship between the electronic structure of the nanocarbon fillers and the antibacterial and antibiofouling activities of the composites was established. Thorough spectroscopic analysis of reactive oxygen species (ROS) generation was conducted for both composite films, and it was found that both of them were potent antibacterial agents against nosocomial bacteria (Klebsiela pneumoniae, Proteus mirabilis, Salmonela enterica, Enterococcus faecalis, Enterococcus epidermis and Pseudomonas aeruginosa). Antibiofouling testing of composite films indicated that the CPDs/PU composite films eradicated almost completely the biofilms of Pseudomonas aeruginosa and Staphylococcus aureus and about 50% of Escherichia coli biofilms

A review of energy analysis simulation tools

Sustainable design is the philosophy of designing physical objects, built environment, and services to comply with the principles of social, economic, and ecological sustainability. The most widespread method for achieving this goal is the use of energy analysis simulation tools. The paper presents comparison between software tools regarding their use in BIM environment and gives advice on most usable application

The Influence of Tip Sonication on Structural and Morphological Properties of Graphene

Although ultrasound is frequently used to disperse carbon nanomaterials in suitable solvents, the propagation of high-amplitude ultrasonic vibrations from the tip sonicator was found to be aggressive and has the potential to break down graphene sheets. Here, the effects of tip sonication time on structural and morphological properties of two types of graphene (graphene oxide and electrochemically exfoliated graphene) was investigated by UV-vis spectroscopy and Atomic Force Microscopy. It was found that the structural composition of the graphene was not affected by ultrasounds emitted from the tip sonicator even for the prolonged period of sonication (60 min). Microscopy analysis showed an increased portion of smaller graphene sheets in the sonicated samples for both types of graphene as a result of graphene sheet fragmentation caused by tip sonication.28th International Symposium on Analytical and Environmental Problems : Proceedings; November 14-15, 2022; Szeged, Hungary

Microwave synthesis of N-CQDs : effect of wavelength on degradation of organic pollution in water

Industries today realis high amounts of different hazards into the environment without any pre– treatment, which is why the remediation from organic pollution still represents one of the most important issues in waste water treatment. Organic dyes from textile industry are one of the extremely geno‒toxic and cyto‒toxic pollutants. Thus, finding the appropriate photocatalyst for the treatment of contaminated water under sunlight is still a challenging work from economical and green chemistry approach. Here we present a microwave assisted synthesis of nitrogen doped carbon quantum dots with high efficiency in degradation of Rose Bengal organic dye from water under visible, blue, green and red light irradiation in batch system. The effect of microwave irradiation power and time on size and photocatalytic activity of synthesized dots were also investigated

Morphology, distribution, and histochemistry of trichomes of Thymus lykae Degen & Jav. (Lamiaceae)

Micromorphology, distribution, and histochemistry of the trichomes of Thymus lykae were studied using scanning electron microscopy (SEM)and confocal laser scanning electron microscopy (CLSM). The leaves, stem, and calyx bear numerous glandular and non-glandular trichomes. Two types of glandular trichomes are identified - peltate and capitate. Results of histochemical tests showed positive reactions to polysaccharides, proteins, and lipids. Yellow autofluorescence of secreted material was noticed in peltate and capitate trichomes. Strong reddish-yellow autofluorescence of the lipophilic and hydrophilic secreted material was observed with CLSM.Mikromorfologija, distribucija i histohemijska analiza trihoma kod vrste Thymus lykae urađena je korišćenjem skening elektronskog mikroskopa i konfokalnog laserskog skening mikroskopa. Nežlezdane, negranate i dva tipa žlezdanih trihoma - peltatne i kapitatne opisane suuovom radu. Brojne nežlezdane i žlezdane trihome nalazile suse kako na listovima (i na licu i na naličju)tako i na stablu i na čašici. Rezultati histohemijskih istraživanja pokazala supozitivne reakcije na polisaharide, lipide i proteine. Sekretorni produkti unutar peltatnih trihoma imali sujako žutu autofluorescenciju, dok je u kapitatnim trihomama zapažena slabija autofluorescencija. Korišćenjem CLSM uočena je jarko crveno-žuta autofluorescencija lipofilnih i hidrofilnih sekretornih materija u žlezdanim trihomama.Projekat ministarstva br. 14304

Development of novel gamma radiation dosimeter based on metallophthalocyanine

In this study, zinc phthalocyanine was evaluated as a possible chemical dosimeter for gamma rays at low-medium dose ranges in solution form and PVA film. The zinc phthalocyanine was successfully synthesized with a high yield under microwave irradiation at 200 °C. The calibration curves of absorbance versus dose of gamma irradiation show excellent linearity over a wider dose range (1 - 25kGy). After being irradiated, the samples' color changed from blue to yellow