Abstract
Here, we present a miniaturized lab-on-a-chip detecting system for an all-electric and label-free analysis of the emulsion droplets incorporating the nanoscopic silicon nanowires-based field-effect transistors (FETs). We specifically focus on the analysis of β-galactosidase e.g., activity, which is an important enzyme of the glycolysis metabolic pathway. Furthermore, the efficiency of the synthesis and action of β-galactosidase can be one of the markers for several diseases, e.g., cancer, hyper/hypoglycemia, cell senescence, or other disruptions in cell functioning. We measure the reaction and reaction kinetics-associated shift of the source-to-drain current Isd in the system, which is caused by the change of the ionic strength of the microenvironment. With these results, we demonstrate that the ion-sensitive FETs are able to sense the interior of the aqueous reactors; thus, the conjunction of miniature nanosensors and droplet-based microfluidic systems conceptually opens a new route toward a sensitive, optics-less analysis of biochemical processes.
Highlights
The interest of the scientific community on the miniaturized lab-on-a-chip systems and on the label-free sensors has been dramatically growing during last two decades, due to the great promise of the technology to be efficiently used for a wide range of applications, e.g., molecular biology, proteomics, cell biology,chemistry, and even in everyday medical practice [1,2,3]
Implementing them in a potentiometric system (e.g., field-effect transistors (FETs)) would be of extreme advantage for accessing a new information channel in the assay. This was demonstrated for the first time using silicon nanowires (SiNWs) as the semiconductor material of the FETs, with the preliminary monitoring of pH changes caused by enzymatic glucose oxidation activity [27]
When the enzyme amount was kept constant at 1 U (Figure S3b), saturation was observed after 10 min for the smallest ONPG concentration (0.5 mM)
Summary
The interest of the scientific community on the miniaturized lab-on-a-chip systems and on the label-free sensors has been dramatically growing during last two decades, due to the great promise of the technology to be efficiently used for a wide range of applications, e.g., molecular biology, proteomics, cell biology, (bio)chemistry, and even in everyday medical practice [1,2,3]. It has been demonstrated that the nanomaterial-based FET sensors, integrated into microfluidic channels [25], represent an efficient asset to the diagnostic platform Such sensors help to achieve chemical information (ionic, pH), reaction kinetics, or chemical process dynamics through associated changes of the surface potential at the transducer. Implementing them in a potentiometric system (e.g., FET) would be of extreme advantage for accessing a new information channel in the assay (e.g., ionic, pH) This was demonstrated for the first time using silicon nanowires (SiNWs) as the semiconductor material of the FETs, with the preliminary monitoring of pH changes caused by enzymatic glucose oxidation activity [27]. Aca3rr0i0erμsmthwatidreesapnodnd15wμitmh hinicgrheapsoinlygdcimurerethnyt lusiplooxnane (PaDpMplSy)incghaanngerlowwainsgprpoodsuitcievde ugsaitnegvtholetasgoeft (listeheogFrigapuhrey t2ebc)h. nAiqu3e00(seμemSIw) aidned manodun1t5edμomn thhieghchip (Fpigoulyrdei2mae)tbhyylpsillaosxmanaeb(oPnDdMinSg) (cZheapnntoe,l DwiaesneprroEdleuccterdonuiscisn,gEbthheausosfetnl,itGhoergmraapnhyy) twecihthnitqiguhet(sseeealSinI)g to praenvdenmt uounndteesdiraobnlethseolcuhtiiopn(Fleiagkuarege2oa)r ebvyapploarsamtiaonb,opnadritnicgle(Zcoenpttaom, Diniaetnieorn,Ealencdtrloiqnuicisd, vEibbhraautisoenn,due toGaeirrmflaonwy)[4w8]i.th tight sealing to prevent undesirable solution leakage or evaporation, particle contamination, and liquid vibration due to air flow [48]
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