| Abstract | ovom doktorskom radu provedena je priprava i karakterizacija ugljikovih kvantnih točaka (CQD) dobivenih iz kore klementine te je ispitana njihova primjenjivost u biomedicinske i analitičke svrhe. Modelni sustav predstavljaju nanočestice CQD dobivene iz limunske kiseline hidrotermalnom sintezom uz dodatak različitih aminokiselina (Ala, Arg, Asn, Gln, Glu, Gly, His, Leu, Lys, Phe, Ser i Trp) kao N-dopanti. Rezultati su pokazali da nanočestice dobivene uporabom limunske kiseline i aminokiselina Ala, Arg, His, Leu, Lys i Trp iskazuju izvrsna fizikalno-kemijska svojstva u rasponu kvantnih prinosa od 12,97 % do 36,43 % pri ispitanom pH = 7, dok je u odnosu na sustav bez dodatka aminokiselina (\(CQD_{CA}\)) dobiven vrlo nizak kvantni prinos od 2,02 %. Na temelju rezultata modelnog sustava, navedene aminokiseline ispitane su u sintezi CQD iz biomase (kore klementine). Istraživanjem je pokazano da kemijski profil različitih prirodnih komponenti koje se nalaze u kori klementine utječu na optička, fizikalna i kemijska svojstva nanočestica, ali i na biološku aktivnost, koju nanočestice dobivene iz limunske kiseline nisu iskazivale. Kako bi se povećao kvantni prinos uzoraka dobivenih iz kore klementine, dodatak manje količine limunske kiseline rezultirao je poboljšanjem i u kvantnom prinosu, ali i u potencijalnoj primjenjivosti čestica s izvrsnom biološkom i farmakološkom aktivnošću (hibridni uzorak \(CQD_{CA+KK+Leu}\)). Primjenom metode odzivnih površina provedena je optimizacija procesa priprave \(CQD_{CA+KK+Leu}\ uzorka te je ispitan utjecaj pojedinih parametara (temperatura i vrijeme) na odziv kvantnog prinosa. U konačnici, tri uzorka s najboljim svojstvima iz svake serije sinteze ispitana su na kemijska (stupanj disperzivnosti), fizikalna (AFM, FTIR, PXRD) i optička svojstva (spektrofluorimetrija, UV-Vis spektroskopija) te na biološku i farmakološku aktivnost. Ispitivanje biološke aktivnosti nanočestica provedeno je spektrofotometrijskim metodama za određivanje antiradikalne aktivnosti (DPPH metoda), inhibicije denaturacije proteina, dok je ispitana i biokompatibilnost/citotoksičnost nanočestica na tumorske stanične linije (HeLa, NCI-H385, CaCo-2 i D54). Dobiveni uzorci \(CQD_{CA+Leu}\) i \(CQD_{CA+KK+Leu}\) pokazali su visoki afinitet prema \(Fe^{3+}\) ionima te su razvijeni modeli za detekciju \(Fe^{3+}\) iona metodom spektrofluorimetrije. Rezultatima je pokazano da su razvijeni modeli pogodni za ispitivanja detekcije \(Fe^{3+}\) iona i na realnim uzorcima bunarske vode. |
| Abstract (english) | In this study, the preparation, charaterization and investigation of the potential application of carbon quantum dots (CQD) derived from Citrus clementina peel was investigated. The prepared nanoparticles from citric acid and amino acids of different complexity (Ala, Arg, Asn, Gln, Glu, Gly, His, Leu, Lys, Phe, Ser i Trp) by hydrothermal synthesis represented a model system. The prepared nanoparticles obtained from citric acid and amino acids Ala, Arg, His, Leu, Lys, and Trp demonstrated great physicochemical properties with calculated quantum yield from 12.97% to 36.43% under investigated pH=7. The sample obtained without the addition of amino acids, referred as (\(CQD_{CA}\)) sample, exhibited low quantum yield of 2.02%. Hence, these amino acids were further used for the fabrication of biomass-derived CQD from Citrus clementina peel. The study has demonstrated that chemical profile has effects on the optical, physical and chemical properties of nanoparticles, as well as on the biological activities, compared to the model systems derived from citric acid. In order to improve quantum yield of biomass-derived CQD, small amounts of citric acid were added to the reaction mixture for the \(CQD_{CA+KK+Leu}\)) preparation which led to the higher quantum yield, but also has broaden applicability of nanoparticles due to the outstanding biological and pharmacological properties. By applying response surface methodology, process optimization for \(CQD_{CA+KK+Leu}\)) was performed and the influence of individual parameter (temperature and time) on the response of quantum yield was also investigated. Furthermore, overall three best-performing samples for each series of synthesis were studied in details regarding chemical (solubility), physical (AFM, FTIR, PXRD), optical (spectrofluorimetry, UV-Vis spectroscopy), biological and pharmacological properties. Biological activities of prepared samples were investigated by spectrophotometric methods of antiradical activity (DPPH method), inhibition of protein denaturation, and biocompatibility/cytotoxicity was investigated on tumor cell lines (HeLa, NCI-H385, CaCo-2, D54). Finally, by investigating the selectivity of samples on different metal ions, \(CQD_{CA+Leu}\) and \(CQD_{CA+KK+Leu}\)) samples have shown high affinity toward \(Fe^{3+}\) ions and models were developed for \(Fe^{3+}\) ion sensing. Developed models were tested for the \(Fe^{3+}\) ion detection in real well-water samples. |
