3D-Printed Microfluidic Chip for Real-Time Glucose Monitoring in Liquid Analytes

Abstract

The connection of macrosystems with microsystems for in-line measurements is important in different biotechnological processes as it enables precise and accurate monitoring of process parameters at a small scale, which can provide valuable insights into the process, and ultimately lead to improved process control and optimization. Additionally, it allows continuous monitoring without the need for manual sampling and analysis, leading to more efficient and cost-effective production. In this paper, a 3D printed microfluidic (MF) chip for glucose (Glc) sensing in a liquid analyte is proposed. The chip made in Poly(methyl methacrylate) (PMMA) contains integrated serpentine-based micromixers realized via stereolithography with a slot for USB-like integration of commercial DropSens electrodes. After adjusting the sample's pH in the first micromixer, small volumes of the sample and enzyme are mixed in the second micromixer and lead to a sensing chamber where the Glc concentration is measured via chronoamperometry. The sensing potential was examined for Glc concentrations in acetate buffer in the range of 0.1-100 mg/mL and afterward tested for Glc sensing in a cell culturing medium. The proposed chip showed great potential for connection with macrosystems, such as bioreactors, for direct in-line monitoring of a quality parameter in a liquid sample.

Keywords: 3D printing; PMMA; SLA; electrochemical sensor; glucose; lab-on-a-chip; microfluidics.

Figure 1

Schematics of the proposed glucose detection concept.

Figure 2

(a) Design of serpentine-based micromixer with Probes used in simulations. Dimensions are in mm. (b) Mixing index values for different flow rates with ratio 0.33. (c) Comparison between simulation results and mixing of color dyes in the microfluidic mixer for flow rate equal to 67 µL/min at inlets, after first serpentine and at outlet.

Figure 3

(a) Multilayer structure of the proposed LOC. (b) Three-dimensional profile of the SLA printed MF channel. (c) Realized LOC with integrated DropSens sensor.

Figure 4

Results of electrochemical Glc detection in the proposed LOC. (a) Examining the potential of H₂O₂ oxidation peak. Scans 1–2 in acetate buffer. Scans 3–4 added droplet of GOx. Scans 5–6 added droplet of fructose. Scans 7–8 added droplet of Glc. (b) Intensity of oxidation peaks from Figure 4a at 0.9 V vs. Ag/AgCl. (c) Results of chronoamperometry for Glc prepared in acetate buffer. (d) Calibration curve of Glc detection in acetate buffer. The signal is presented as a relative change versus acetate buffer response. $\delta (\%)=100\times \left(I_{cc}-I_{buffer}\right)/I_{buffer}$.

Figure 5

(a) Results of chronoamperometry for different concentrations of Glc in cell medium Inset: Calibration curve of Glc detection for medium diluted with acetic acid and enzyme. (b) Calibration curve of Glc detection in the cell medium for Glc concentrations at inlet of LOC. The real concentration is calculated by multiplying the measured concentration with the flow rate factor and factor 2 which presents dilution with enzyme mixing. The signal is presented as a relative change versus acetate buffer response: $\delta (\%)=100\times \left(I_{cc}-I_{buffer}\right)/I_{buffer}$.