doctoral dissertation
Tinkara Mastnak (Avtor), Aleksandra Lobnik (Mentor), Matjaž Finšgar (Komentor)

Povzetek

Občutljiva in selektivna detekcija biotiolov je v zadnjih letih deležna vse večje pozornosti, saj so spremembe njihove koncentracije v krvi, plazmi in urinu povezane z različnimi obolenji. Ker ima vsaka od standardnih tehnik za njihovo detekcijo osnovne omejitve v zvezi s kompleksnostjo, pripravo vzorca, časom trajanja analize in stroški, so nove metode izjemno zaželene. Biogeni amini so vključeni v pomembne presnovne in fiziološke funkcije in so lahko naravno prisotni v hrani in pijači. Visoke vsebnosti biogenih aminov v živilih so posledica intenzivne mikrobne aktivnosti zaradi fermentacije ali kvarjenja. Tako nadzor nad biogenimi amini postaja vse pomembnejši za spremljanje procesov proizvodnje živil, za preverjanje njihove kakovosti in svežosti ter za spremljanje njihove varnosti. Podatki o prisotnosti biogenih aminov v prehrambenih izdelkih niso dosledni, ker je njihova koncentracija odvisna od vsebnosti vlage, maščob, beljakovin in pH. Te lastnosti zagotavljajo okolje za razvoj mikroorganizmov in biokemičnih reakcij, zaradi česar so živila med predelavo in skladiščenjem pokvarljiva. Določanje biogenih aminov v živilih je dolgotrajno in zahteva drage analizne instrumente. Kolorimetrična detekcija v nadprostoru tako ponuja elegantno rešitev, saj se lahko podatki povežejo s številom mikroorganizmov, s čimer posledično določimo raven svežosti ali pokvarjenosti hrane. Doktorska disertacija predstavlja lastnosti in uporabnost 4-N,N-dioktilamino-4'-dicianovinilazobenzena (CR-528) in 4-N,N-dioktilamino-2'-nitro-4'-dicianovinilazobenzena (CR-555) za zaznavanje biotiolov in biogenih aminov. Senzorne lastnosti CR-528 in CR-555 so bile najprej preizkušene v raztopini etanola. Dodajanje žveplo-vsebujočih analitov (2 merkaptoetanola (2-ME), hidrosulfida (SH─)) in določenih biogenih aminov (spermina (SP), spermidina (SPD), etanolamina (EA)) je povzročilo koncentracijsko odvisne spektralne spremembe, ki so jih spremljale vidne spremembe barve iz rožnate/vijolične do bledo rumene/oranžno-rumene. Ker detekcija omenjenih analitov v etanolu nima velike uporabne vrednosti, smo CR-528 in CR-555 imobilizirali v dve različni polimerni osnovi – hidrofilni poliuretanski hidrogel (PHD4) in hidrofobni kopolimer na osnovi etilena in vinil acetata (EVA), s čimer smo pridobili optične senzorske receptorje v obliki indikatorskih plasti. Tem smo najprej raziskali detekcijske lastnostih za zaznavanje žveplo-vsebujočih analitov (celokupnih sulfidov in 2-ME) v pufru s fiziološkim pH (7.4). Rezultati so pokazali, da je za dosego diagnostično relevantnih koncentracijskih območij potrebno močno izboljšati občutljivost indikatorskih plasti. Izkazalo se je tudi, da so samo optični senzorski receptorji na osnovi EVA dovolj stabilni, da jih je smiselno nadalje raziskati kot kolorimetrične naprave za detekcijo hlapov biogenih aminov. Reakcija CR-528/EVA in CR-555/EVA s hlapi izopentilamina (IPA) je povzročila očitno spremembo barve iz rožnate/vijolične do rumene/oranžno-rumene. CR 555/EVA optični senzorski receptor se je odzval tudi na izpostavljenost kadaverinu (CAD). Spremembe barv so bile analizirane z UV/VIS molekulsko absorpcijsko spektroskopijo, pri čemer je bila metoda delno validirana. Določili smo mejo zaznavnosti, občutljivost, linearno koncentracijsko območje, točnost in natančnost. Najnižje meje zaznavnosti so bile dosežene z CR-555/EVA (0,40 ppm za IPA in 1,80 ppm za CAD) optičnimi senzorskimi receptorji. Na zadnje smo ugotovili, da zaradi visoke reaktivnosti, neobstojnosti v raztopini v daljšem časovnem obdobju, občutljivosti na pH in na povišane temperature, barvili nista primerni za imobilizacijo v silicijeve delce.

Ključne besede

azo dyes;biogenic amines;biothiols;optical sensor receptors;polyurethane hydrogel;ethylene-vinyl acetate copolymer;

Podatki

Jezik: Angleški jezik
Leto izida:
Tipologija: 2.08 - Doktorska disertacija
Organizacija: UM FKKT - Fakulteta za kemijo in kemijsko tehnologijo
Založnik: [T. Mastnak]
UDK: 577.354(043.3)
COBISS: 22315798 Povezava se bo odprla v novem oknu
Št. ogledov: 1374
Št. prenosov: 196
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Slovenski jezik
Sekundarni naslov: Optical sensor receptors based on azo dyes
Sekundarni povzetek: Sensitive and selective detection of biothiols has received growing attention in recent years as changes in their levels in blood, plasma and urine have been correlated to a variety of medical disorders. Since each of the standard techniques for the analysis of biothiols has basic limitations with regard to complexity, sample preparation, run times, and cost, new methods are greatly needed. Biogenic amines are involved in important metabolic and physiological functions and may occur naturally in foods and beverages. Their high levels in foods are a consequence of intensive microbial activity due to fermentation or spoilage. For this reason, the control over biogenic amines is gaining importance in order to monitor food production processes, to ascertain the quality and freshness of food, and to monitor food safety. There is no consistency in the data about the presence of biogenic amines in foods because their concentration depends on the intrinsic properties, such as the content of moisture, fat, protein, and the pH value. These provide environment for the development of microorganisms and biochemical reactions, making the foods perishable during processing and storage. The determination of biogenic amines in food matrices is time consuming and requires expensive analytical instrumentation, whereas their colorimetric detection in the headspace offers an elegant solution, because the data can be correlated with the microbial count to determine the level of food freshness or spoilage. The doctoral dissertation presents properties and applicability of 4-N,N-dioctylamino-4'-dicyanovinylazobenzene (CR-528) and 4-N,N-dioctylamino-2'-nitro-4'-dicyanovinylazobenzene (CR-555) for the detection of biothiols and biogenic amines. The sensing principle of CR-528 and CR-555 was first tested in ethanol solution. The addition of sulfur-containing analytes (2-mercaptoethanol (2-ME), bisulfide (SH─)), and certain biogenic amines (spermine (SP), spermidine (SPD), ethanolamine (EA)) resulted in concentration-dependant spectral changes accompanied with significant colour changes from pink/purple to pale yellow/orange-yellow. Since sensing in ethanol has limited applicability, CR 528 and CR-555 were immobilized in two different polymer matrixes–hydrophilic Polyurethane HydroMed™ D4 (PHD4) and hydrophobic Ethylene-Vinyl Acetate Copolymer (EVA) to obtain optical sensor receptors in the form of indicator layers. These were first tested for the detection of sulfur-containing analytes (total sulfides and 2 ME) in HEPES buffer at physiological pH (7.4). The results showed that the sensitivity of optical sensor receptors should be greatly improved in order to reach diagnostically relevant concentration ranges. Furthermore, only EVA-based optical sensor receptors were stable enough to be further explored as colorimetric devices for the detection of vaporous biogenic amines. The reaction of CR-528/EVA and CR-555/EVA with isopentylamine (IPA) vapours caused a vivid colour change from pink/purple to yellow/orange-yellow. Additionally, CR-555/EVA showed colour changes upon exposure to cadaverine (CAD). The colour changes were analysed by UV/VIS molecular absorption spectroscopy for amine quantification, and the method was partially validated for the detection limit, sensitivity, linear concentration range, accuracy and precision. The lowest detection limits were reached with CR-555/EVA indicator layers (0.40 ppm for IPA and 1.80 ppm for CAD). Finally, several attempts were made to incorporate CR-528 and CR-555 into silica particles. The dyes proved unsuitable for this purpose due to high reactivity, instability in solution for longer periods of time, sensitivity to pH and elevated temperatures.
Sekundarne ključne besede: azo barvila;trajnbiogeni;biotioli;soptični senzorski receptorji;poliuretanski hidrogel;kopolimer etilena;vinil acetat;
URN: URN:SI:UM:
Vrsta dela (COBISS): Doktorsko delo/naloga
Komentar na gradivo: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Strani: XVI, 119 str.
ID: 11047539