Oksidacija i adsorpcija nepafenaka na površini elektrode modificirane različitim nanomaterijalima

master's thesis

• Title (english): Oxidation and adsorption of nepafenac on nanomaterial-modified electrode surfaces
• Author: Edvin Brusač
• Mentor: Biljana Nigović (mentor)
• Committee member: Biljana Nigović (predsjednik povjerenstva)
• Committee member: Ana Mornar Turk (član povjerenstva)
• Committee member: Sandra Jurić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Pharmacy and Biochemistry; (Department of pharmaceutical analysis); Zagreb
• Defense date and country: 2018-05-04, Croatia
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Pharmacy; Pharmacy

Abstract

Nepafenak je noviji nesteroidni protuupalni analgetik, inhibitor ciklooksigenaze. Indikacije za ovaj lijek su prevencija i liječenje postoperativne boli i upale povezane s operacijom katarakte te smanjenje rizika od postoperativnog makularnog edema povezanog s operacijom katarakte kod bolesnika s dijabetesom.
U ovom radu ispitivana su elektrokemijska svojstva nepafenaka uporabom tehnika cikličke i pravokutnovalne voltametrije u elektrolitima različitih pH te na različitim elektrodama uz modifikaciju površina elektroda nanomaterijalima. Cilj rada bio je proučiti elektrokemijsko ponašanje nepafenaka na različitim elektrodama i utvrditi mogu li dobiveni rezultati poslužiti za razvoj analitičke metode za određivanje spoja.
Snimanjem cikličkih voltamograma utvrđeno je kako je pH 6 osnovnog elektrolita, tj. BR pufera najpovoljniji za intenzitet oksidacijskog pika nepafenaka, koji se javlja na potencijalu oko 0,80 V. Također je utvrđeno kako je proces oksidacije ireverzibilan. Od različitih elektroda, najveću osjetljivost uz najmanji utjecaj pozadinske struje pokazala je elektroda od staklastog ugljika promjera 3 mm. Modifikacijom površine elektrode od staklastog ugljika suspenzijama različitih nanomaterijala u 0,3%-tnoj etanolnoj otopini Nafiona postiže se veći intenzitet pika lijeka, što znači veću osjetljivost metode. Pik oksidacije nepafenaka porastao je 3 puta u odnosu na nemodificiranu elektrodu u slučaju ugljikovih nanovlakana i grafen nanopločica, dok je kod grafen oksida porast bio nešto manji.
Snimanjem pravokutnovalnih voltamograma zamijećena je adsorpcija lijeka te njegovog produkta oksidacije na elektrodi modificiranoj nanomaterijalima. Pik oksidacijskog produkta javlja se na potencijalu od 0,15 V i nakon snimanja u puferu, što upućuje na jaku adsorpciju ili potencijalnu kemijsku reakciju s površinom elektrode. Adsorpcija lijeka se javlja u slučaju sva tri nanomaterijala, no adsorpcija oksidacijskog produkta značajno je manja u slučaju grafen nanopločica. Ispitivanjem kinetike adsorpcije utvrđeno je kako se adsorpcijsko-desorpcijska ravnoteža brže uspostavlja na elektrodi modificiranoj grafen nanopločicama nego onoj modificiranoj ugljikovim nanovlaknima.

Abstract (english)

Nepafenac is a novel non-steroidal anti-inflammatory analgesic, cyclooxygenase inhibitor. Its therapeutic indications are prevention and treatment of postoperative pain and inflammation associated with cataract surgery and reduction in the risk of postoperative macular oedema associated with cataract surgery in diabetic patients.
In this thesis, the electrochemical properties of nepafenac in electrolytes of various pH and on various electrodes with nanomaterial-modified surfaces were investigated by the use of cyclic and square-wave voltammetry. The goal of this thesis was to look into the electrochemical behaviour of nepafenac on various electrodes and to ascertain if the gathered results might prove useful in the development of an analytical method for the identification and quantification of the drug.
Cyclic voltammetry measurements have established that the pH of 6 of the supporting electrolyte, that is, BR buffer, is the most efficient for the nepafenac oxidation peak intensity, which is seen at the potential of 0,80 V. Moreover, it has been proven that the oxidation process is irreversible. Out of various electrodes, a 3 mm-diameter glassy carbon electrode has shown the highest sensitivity with the least impact of the background current. By modifying the surface of the glassy carbon electrode with suspensions of various nanomaterials in 0,3% ethanolic solution of Nafion, higher drug peak intensity is achieved, which leads to higher sensitivity of the method. By using carbon nanofibers and graphene nanoplatelets, the nepafenac oxidation peak increases threefold compared to the nonmodified electrode, whereas by using graphene oxide there is less increase compared to the other two nanomaterials.
Square-wave voltammetry scans have shown adsorption of the drug and its oxidation product on the surface of the nanomaterial-modified electrodes. The peak of the oxidation product is observed on the potential of 0,15 V even after scanning the electrode in the buffer, which implies strong adsorption or a possible chemical reaction with the surface of the electrode. Adsorption of the drug occurs in all three nanomaterials, but the adsorption of the oxidation product is significantly lesser on graphene nanoplatelets. In regard to adsorption kinetics, the adsorption-desorption equilibrium is established more rapidly on the electrode modified with graphene nanoplatelets than on the one modified with carbon nanofibers.

• Keywords: nepafenak; ciklička voltametrija; pravokutnovalna voltametrija; elektroda modificirana nanomaterijalima
• Keywords (english): nepafenac; cyclic voltammetry; square-wave voltammetry; nanomaterial-modified electrode
• Language: croatian
• URN:NBN: urn:nbn:hr:163:608087
• Study programme: Title: Pharmacy; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra farmacije (magistar/magistra farmacije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-01-16 14:35:27