A novel lab-on-a-chip platform for spheroid metabolism monitoring

Abstract

Sensor-based cellular microphysiometry is a technique that allows non-invasive, label-free, real-time monitoring of living cells that can greatly improve the predictability of toxicology testing by removing the influence of biochemical labels. In this work, the Intelligent Mobile Lab for In Vitro Diagnostics (IMOLA-IVD) was utilized to perform cellular microphysiometry on 3D multicellular spheroids. Using a commercial 3D printer, 3 × 3 microwell arrays were fabricated to maintain nine previously cultured HepG2 spheroids on a single BioChip. Integrated layers above and under the spheroids allowed fluidic contact between spheroids in microwells and BioChip sensors while preventing wash out from medium perfusion. Spheroid culturing protocols were optimized to grow spheroids to a diameter of around 620 μm prior to transfer onto BioChips. An ON/OFF pump cycling protocol was developed to optimize spheroid culture within the designed microwells, intermittently perfuse spheroids with fresh culture medium, and measure the extracellular acidification rate (EAR) and oxygen uptake rate (OUR) with the BioChips of the IMOLA-IVD platform. In a proof-of-concept experiment, spheroids were perfused for 36 h with cell culture medium before being exposed to medium with 1% sodium dodecyl sulphate (SDS) to lyse cells as a positive control. These microphysiometry studies revealed a repeatable pattern of extracellular acidification throughout the experiment, indicating the ability to monitor real-time metabolic activity of spheroids embedded in the newly designed tissue encapsulation. After perfusion for 36 h with medium, SDS exposure resulted in an instant decrease in EAR and OUR signals from 37 mV/h (± 5) to 8 mV/h (± 8) and from 308 mV/h (± 21) to -2 mV/h (± 13), respectively. The presented spheroid monitoring system holds great potential as a method to automate screening and analysis of pharmaceutical agents using 3D multicellular spheroid models.

Spheroids-on-a-chip: Recent advances and design considerations in microfluidic platforms for spheroid formation and culture

“…The measurements were based on the impedance changes of the HDs and spheroids due to their size and the resulting changes in the electrical field. Alexander et al recently fabricated an on-chip platform for the measurement of extracellular acidification, oxygen uptake rate of cell spheroids, temperature and electrical impedance in a µSCC [209]. They pipetted the pre-formed spheroids into a 3D-printed cylindrical microwell in the chip which was confined with two membranes having 120 µm pores from the bottom and above ( Figure 17A).…”

“…The sensor consists of four working platinum electrodes, one platinum counter electrode and an Ag/AgCl reference electrode; (c) the cross-section views A and B clarify the flow in the microchannels and the yellow glass plug-ins on which the sensors are deposited. Reproduced with permission from[207]; (B) A cross-sectional view of the µSCC (a) and the sensor chip (b) designed by Alexander et al[209]; (a) It consists of a fluidic channel in the top, three 1 mm diameter microwells containing the spheroids and a sensor microchip in the bottom of the porous membranes; (b) the sensor chip measures the pH of the microenvironment (pH1 and pH2 sensors), oxygen uptake rate by the cells (pO2 amperometric sensor), temperature (T) and electrical impedance (Imp1 and Imp2) by the electrodes shown in the figure. Reproduced with permission from[209];…”

Three‐Dimensional (3D) cell culture monitoring: Opportunities and challenges for impedance spectroscopy

“…Most of these culture characteristics are measured in the media downstream of cells and they give real‐time information without destruction of the culture or tissue. These sensors are commercially available and are usually incorporated within bioreactor systems that are used to grow and monitor spheroids or cells in suspension over time (Alexander, Eggert, & Wiest, 2018; Weyand et al, 2015). This approach assumes that the media is reflecting the behavior inside the tissue.…”

Inventions and Innovations in Preclinical Platforms for Cancer Research

“…For the real-time on-chip monitoring of the spheroids, several techniques have been developed including the electrode-based biosensors for oxygen [109], glucose and lactate concentration [110] and also pH and electrical impedance [111] measurements. These monitoring techniques alleviate the need for spheroid retrieval from the chip, which effectively reduces the time and cost.…”