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Abstract: Detection in microfluidic systems requires highly sensitive analytical methods, because of the very short optical interaction length, which is usually in the range of 100 μm or shorter. Furthermore, the amounts of analytes in detection volumes are extremely small (femto- or attomoles). Thermal lens spectrometry and particularly thermal lens microscopy (TLM) appear as techniques of choice for detection in microfluidic and lab-on-a-chip systems, since they enable measurements of absorbance’s or absorbance changes as low as 10-7. In addition to ultra-high sensitivity, TLM offers high spatial resolution (≈1 μm) and sufficient temporal resolution (ms range), which is required for studies of processes in microfluidic systems. Recent development of TLM theory and instrumentation lead to experimental confirmations of the effects of microfluidic flows on the TLM signal, which affects the sensitivity. On the other hand, these observations have enabled optimization of TLM instruments [1]. As a result of these advancements, applications of TLM were extended from simple laminar flows [2], to highly complex systems such as Tylor-type flows, where TLM detection provided data for description of diffusion processes in n-octane/methanol binary liquid systems [3]. The major streamline of TLM applications was however focused on the development of vanguard analytical systems [4], which are needed in various fields of chemical analysis, including food safety and quality control, environmental monitoring as well as biomedical research and diagnostics. Such systems are used as sample screening systems (sample filters or selectors) when the information is needed quickly to make immediate decisions in relation to the analytical problem. They provide simplicity (e.g. little or no sample pre-treatment), low cost, rapid and reliable response, and frequently give just binary responses. However, their major weakness is low metrological quality of results. Therefore, uncertainties of up to 5–15% are usually accepted as a toll for rapidity and simplicity, which are essential even though in contradiction with conventional analytical concepts. With the objective of developing new vanguard analytical systems, a relevant goal is to exploit the advantages offered by microfluidic lab-on-a-chip systems on one hand, and TLM detection on the other. In such combinations, the FIA approach simplifies sample handling (e.g. volume measurements) and transport to the detector, while microfluidic lab-on-a-chip technology can facilitate and speed up processes including colorimetric reactions, antigen–antibody or enzyme–substrate interactions in bioanalytical systems, and even extraction and preconcentration steps by introducing continuous flow processing and micro unit operations in chemical analysis [2]. High sensitivity of TLM in such systems offers low limits of detection, which also contribute to low uncertainties that are typically below 10%. An important advantage of microfluidic systems lies in the fact that small dimensions of such systems, which consist of capillaries and micro reactors with dimensions about 10 to 100 μm, significantly reduce the molecular diffusion time, which is inversely proportional to the second power of distance. For example, the time required for completion of an ELISA immunoassay for NGAL a biomarker of acute kidney failure was reduced from four hours to only 30 mins. [5, 6] when transferring the assay into a microfluidic system, while maintaining or even improving the sensitivity. Even more evident improvement in sample throughput (reduction of analysis time from 10 hours to 30 minutes) was achieved for determination of antibodies for human papilloma virus (anti L1 HPV 16) in blood plasma, after immobilizing adequate pseudovirions as antigens on magnetic nanobeads [6]. Other health-related applications include detection of toxins, such as microcystin, or carcinogenic substances such as Cr(VI), which offers improved limits of detection as compared to spectrophotometry as well as sample throughput, which can reach 20 samples/min. [7]. [1] M. Liu and M. Franko, Crit. Rev. Anal. Chem. 44, 328-353 (2014). [2] T. Kitamori, M. Tokeshi, A. Hibara, and K. Sato, Anal. Chem. 76, 52A-60A (2004). [3] M. Lubej, U. Novak, M. Liu, M. Martelanc, M. Franko and I. Plazl, Lab Chip (2015) DOI:10.1039/c4lc01460j. [4] M. Valcárcel and B. Lendl. Trends Anal. Chem. 23, 527-534 (2004). [5] T. Radovanović, M. Liu, P. Likar, M. Klemenc and M. Franko, Int. J. Thermophys. (2014) DOI:10.1007/s10765-014-1699-9. [6] T. Radovanović, Dissertation, University of Nova Gorica (2016). [7] M. Franko, M. Liu, A. Boškin, A. Delneri, and M.A. Proskurnin, Anal. Sci. 32, 23-30 (2016).
Keywords: Spektrometrija TLM, mikrofluidni sistemi, biomarkerji, alergeni, pesticidi, acetilholinesteraza
Published in RUNG: 07.11.2016; Views: 5554; Downloads: 42
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Keywords: pesticidi, diklorvos, ometoat, dimetoat, CSIA
Published in RUNG: 16.06.2016; Views: 4475; Downloads: 19
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Abstract: Škodljive učinke onesnaženja lahko določimo z merjenjem specifičnih odzivov na onesnaženje – z biomarkerji. Izmeril sem aktivnost acetilholinesteraze (odgovor na onesnaženje z organofosfatnimi in karbamatnimi pesticidi) in koncentracije metalotioneinov (odgovor na onesnaženje s težkimi kovinami) v klapavicah, ki so bile nabrane na štirih vzorčnih mestih. Izračunal sem kondicijski in gonadosomatski indeks klapavic ter izmeril okoljske parametre morske vode (temperatura, koncentracija kisika, slanost in pH). Meritve sem opravljal v pomladnem in v jesenskem obdobju leta 2011, da bi ugotovil, ali se vrednosti izmerjenih biomarkerjev razlikujejo med sezonami in med vzorčnimi mesti. Izbrana vzorčna mesta so bila: školjčišče ob Debelem rtiču (vzorčno mesto 00DB), marina v Kopru (vzorčno mesto 00TM) ter školjčišči v Strunjanskem (vzorčno mesto 0024) in Piranskem zalivu (vzorčno mesto 0035). Največjo aktivnost acetilholinesteraze (AChE) sem izmeril v klapavicah iz Strunjanskega zaliva (119 ± 18 μmol min-1 mg-1 v pomladnem vzorčenju in 114 ± 6 μmol min-1 mg-1 v jesenskem vzorčenju) in v klapavicah iz školjčišča ob Debelem rtiču (118 ± 11 μmol min-1 mg-1 v pomladnem vzorčenju in 109 ± 11 μmol min-1 mg-1 v jesenskem vzorčenju). Najnižjo aktivnost AChE sem izmeril v klapavicah z vzorčnega mesta 00TM v Koprskem zalivu: 75 ± 6 μmol min-1 mg-1 v pomladnem vzorčenju in 60 ± 7 μmol min-1 mg-1 v jesenskem vzorčenju. Izmerjena aktivnost AChE v klapavicah z vzorčnega mesta 0035 v Piranskem zalivu je bila 97 ± 12 μmol min-1 mg-1 v pomladnem vzorčenju ter 86 ± 8 μmol min-1 mg-1 v jesenskem vzorčenju. Najvišje koncentracije metalotioneinov (MT) so bile izmerjene v jesenskem vzorčenju, v klapavicah iz vzorčnega mesta 0035 v Piranskem zalivu, in sicer 79 ± 9 µg MT g-1 mokre mase vzorca. Najnižjo vsebnost MT v klapavicah sem izmeril jeseni, v vzorcih iz Koprskega zaliva (vzorčno mesto 00TM): 50 ± 6 µg MT g-1 mokre mase. V jesenskem času so bile koncentracije MT v vzorcih iz Strunjanskega zaliva (vzorčno mesto 0024) 75 ± 7µg MT g-1 mokre mase ter v vzorcih iz školjčišča ob Debelem rtiču (vzorčno mesto 00DB) 67 ± 15 µg MT g-1 mokre mase. Spomladi so bile koncentracije MT med vzorčnimi mesti bolj izenačene: na vzorčnem mestu 00TM je bila koncentracija MT 60 ± 3 µg MT g-1 mokre mase, enako na vzorčnem mestu 0035 v Piranskem zalivu (60 ± 10 µg MT g-1 mokre mase tkiva) ter 65 ± 9 µg MT g-1 mokre mase v vzorcih na vzorčnem mestu 00DB ob Debelem rtiču in 68 ± 10 µg MT g-1 mokre mase v vzorcih na vzorčnem mestu 0024 v Strunjanskem zalivu. Značilno nižjo koncentracijo MT sem izmeril na vzorčnem mestu 00TM v Koprskem zalivu v jesenskem vzorčenju. Razlik v koncentraciji MT med sezonama nisem ugotovil. Sezonskih razlik v aktivnosti AChE med vzorčnimi mesti nisem našel. Ugotovil sem, da je aktivnost AChE v klapavicah z vzorčnega mesta 00TM v Koprskem zalivu in v klapavicah iz Piranskega zaliva (vzorčno mesto 0035), v obeh sezonah značilno nižja, kar kaže na trajno izpostavljenost višjim koncentracijam onesnaževal, ki zavirajo AChE v primerjavi s preostalimi vzorčnimi mesti.
Keywords: Mytilus galloprovincialis, acetilholinesteraza, metalotioneini, težke kovine, organofosfatni pesticidi
Published in RUNG: 01.09.2015; Views: 7427; Downloads: 315
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Keywords: pesticidi, bilirubin, krom, spektroskopija, termične leče, spektrofotometrija
Published in RUNG: 15.10.2013; Views: 5685; Downloads: 369
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Keywords: diplomske naloge, vinogradništvo, ekologija, fotorazgradnja, pesticidi, obstojnost
Published in RUNG: 15.10.2013; Views: 8068; Downloads: 386
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