A microfluidic gradient generator to simulate the oxygen microenvironment in cancer cell culture

Abstract

Standard cancer lab models lack many attributes of the in-vivo cancer microenvironment. Oxygen levels for example are not commonly controlled in 2D cell-culture well plate experiments. However, low O2 (hypoxia) in particular is common in cancerous tissue due to high proliferation rates of cancer cells and inadequate vasculature. Hypoxia is also associated with cancer recurrence and drug resistance. We report a microfluidic system capable of exposing a 2D cell-culture to a dissolved oxygen gradient ranging from hypoxia (<1 mg/L) to hyperoxia (40 mg/L) for over 30 minutes, measurable in real-time using an integrated sensor film. The film incorporates a photostable, non-cytotoxic oxygen-sensitive fluorescent dye, which exhibits a linear response and high contrast (I0 /I100 = 12) within the range of interest, was integrated onto glass substrates as a cell culture substrate. To demonstrate the applicability of the platform, Ishikawa cancer cells were cultured on the platform and exposed to linear cross-stream oxygen gradients. The platform provides a valuable tool for the culture of cancer cells in an in-vivo like microenvironment and will enable more accurate screening of new anti-cancer drugs.

Colorectal tumor-on-a-chip system: A 3D tool for precision onco-nanomedicine

“…This low cell death level is in agreement with previous studies, corroborating the fact that 3D cultures usually show a reduced sensitivity to anticancer drugs ( 36 ). This can be due to various factors, including matrix stiffness, which was reported to be closely related to tumor chemoresistance ( 6 ), decreased penetration of anticancer drugs, increased prosurvival signaling, and/or up-regulation of genes conferring drug resistance ( 7 ).…”

“…Microfluidics is by definition the science and technology of systems that process and manipulate small (10 −9 to 10 −18 liters) amounts of fluids by using channels with dimensions from tens to hundreds of micrometers ( 5 ). Microfluidic technology offers new opportunities for cell-based sensors and multifunctional platforms for biochemical and biomedical functions under physiologically relevant conditions ( 6 , 7 ).…”

“…In the in vivo scenario, chemical microenvironment includes nutrients and oxygen, delivered to cells and tissues through a network of vasculature that creates important biomolecular gradients within the tissue. The successful development of 3D microengineered gradients set the stage for physiologically relevant in vitro models, comprising, for instance, oxygen, chemokines, and drug gradients ( 6 , 12 , 14 ). Another important aspect of our model is the microvasculature.…”

Microfluidic-Based Oxygen (O2) Sensors for On-Chip Monitoring of Cell, Tissue and Organ Metabolism

“…Due to the longer lifetime of their excitement, their quenching efficacy is high. Therefore, they have high O 2 sensing sensitivity [39,44,55,56]. Few examples of the most used dyes are Platinum(II) tetrakis(pentafluorophenyl)porphyrin (PtTFPP) [57], Platinium (II) octaethylporphyrin (PtOEP) [42], Platinum (II)-meso-tetra(4fluorophenyl)tetrabenzoporphyrin (PtTPTBPF) [43], Ruthenium-tris(4,7-diphenyl-1,10phenanthroline) dichloride (Ru(dpp)) [55], and Singlet O 2 sensor green (SOSG) [56].…”

“…The layers are developed by directly mixing or dissolving the dyes into the solvent or polymer and then forming a film layer inside or at the top of the microfluidic channels and chambers [ 59 ]. Impregnated polymers are then patterned into the cell chambers using spin coating [ 44 ], knife coating [ 60 ], and preheated coating dye solution [ 41 ]. Dyes are excited by either light-emitting diode (LEDs) or optical fibers.…”