Integration of Multianalyte Sensing Functions on a Capillary-Assembled Microchip:  Simultaneous Determination of Ion Concentrations and Enzymatic Activities by a “Drop-and-Sip” Technique

Abstract

A general and simple implementation of simultaneous multiparametric sensing in a single microchip is presented by using a capillary-assembled microchip (CAs-CHIP) integrated with the plural different reagent-release capillaries (RRCs), acting as various biochemical sensors. A novel "drop-and-sip" technique of fluid handling is performed with a microliter droplet of a model sample solution containing proteases (trypsin, chymotrypsin, thrombin, elastase) and divalent cations (Ca2+, Zn2+, Mg2+) that passes through the microchannel with the aid of a micropipette as a vacuum pump, concurrently filling each RRC via capillary force. To avert the evaporation of the nanoliter sample volume in each capillary, PDMS oil is dropped on the outlet hole of the CAs-CHIP exploiting the capillary force that results in spontaneous sealing of all the RRCs. In addition, this high-speed sample introduction alleviates the possibility of protein adsorption and capillary cross-contamination, allowing a reliable and multianalyte determination of a sample containing many different proteases and divalent cations by using the fluorescence image analysis. Presented results suggested the possible application of this microchip in the field of drug discovery and systems biology.

Nanocellulose-Based Biosensors: Design, Preparation, and Activity of Peptide-Linked Cotton Cellulose Nanocrystals Having Fluorimetric and Colorimetric Elastase Detection Sensitivity

“…The molecular basis of some of these sensor motifs include peptide cross-linked dextran hydrogels with a tunable quartz crystal microbalance detection [51], chromogenic peptide substrates tethered to collagen, polyamide polyesters, silica gel [52], ethoxyacrylate resin [53], and cellulose [54], and DNA-based aptasensors [55]. A variety of sensor design motifs have also been employed, and these include: 1) a microchip integrated with reagent-release capillaries is reported as a "drop-and-sip" technique, which utilizes a single microliter droplet of HNE-containing solution with fluorescence image analysis of the hydrolyzed substrate product [56]; 2) fluorometric detection of HNE activity with synthetic supramolecular pore sensors [57,58] the covalent immobilization of HNE on biosensor chips having surface plasma resonance capability has been employed for analysis of HNE inhibitors [59]; 3) a microdialysis sampling assay of HNE activity where the substrate is delivered through the microdialysis probe to external solutions containing HNE, and the product, pNA, is recovered back into the probe [60].…”

Advancements in Capillary-Assembled Microchip (CAs-CHIP) Development for Multiple Analyte Sensing and Microchip Electrophoresis

“…In this technique, a microliter droplet of sample solution is dropped on the inlet hole and sipped onto the other hole through simple pipetting (active fluid actuation). 36,37 The fluid enters the main PDMS microchannel, which passes through the edges of different hydrophilic sensing glass capillaries, and a nanoliter volume of sample solution is spontaneously distributed into each of the reagent-release capillaries (RRC) through capillary action (passive fluid actuation) (Fig. 3).…”

“…To address this, we have developed an ionsensing capillary based on a dry-reagent technique that has been termed as an RRC. 36,37 The RRC is fabricated by introducing the ion-specific fluorescent reagent with polyethylene glycol (PEG) into the bare square glass capillary using a syringe pump. The PEG acts as a scaffold that holds the reagent on the four corners of the capillary.…”

“…The molecular probe is cleaved by the enzyme present in the sample solution, liberating the fluorescent dye molecule. 36 Enzyme activity-sensing capillaries have been implemented to analyze the effect of doxorubicin drug on HeLa cell lysate. In this CAs-CHIP system, two different sample solutions, untreated and doxorubicin-treated HeLa cell lysates, were analyzed simultaneously, with 2 sets of 10 different enzyme activitysensing capillaries that were designed to interrogate and investigate the drugs' effect on cell death or apoptosis (Fig.…”

Fast and Single-step Fluorescence-based Competitive Bioassay Microdevice Combined PDMS Microchannel Arrays Separately Immobilizing Graphene Oxide-Analyte Conjugates and Fluorescently-labelled Receptor Proteins

“…[5][6][7][8] However, simultaneously solving these problems is still challenging. Recently, we proposed designing "singlestep" microdevices based on square glass capillaries [9][10][11][12][13] or polymer capillaries. [14][15][16] For these approaches, the inner capillary wall is functionalized by physical adsorption or covalent bonding of analytical reagents or by coating the wall with reagent-containing films.…”