Generation of tumor spheroids using a droplet-based microfluidic device for photothermal therapy

Abstract

Despite their simplicity, monolayer cell cultures are not able to accurately predict drug behavior in vivo due to their inability to accurately mimic cell-cell and cell-matrix interactions. In contrast, cell spheroids are able to reproduce these interactions and thus would be a viable tool for testing drug behavior. However, the generation of homogenous and reproducible cell spheroids on a large scale is a labor intensive and slow process compared to monolayer cell cultures. Here, we present a droplet-based microfluidic device for the automated, large-scale generation of homogenous cell spheroids in a uniform manner. Using the microfluidic system, the size of the spheroids can be tuned to between 100 and 130 μm with generation frequencies of 70 Hz. We demonstrated the photothermal therapy (PTT) application of brain tumor spheroids generated by the microfluidic device using a reduced graphene oxide-branched polyethyleneimine-polyethylene glycol (rGO-BPEI-PEG) nanocomposite as the PTT agent. Furthermore, we generated uniformly sized neural stem cell (NSC)-derived neurospheres in the droplet-based microfluidic device. We also confirmed that the neurites were regulated by neurotoxins. Therefore, this droplet-based microfluidic device could be a powerful tool for photothermal therapy and drug screening applications.

Using Spheroids as Building Blocks Towards 3D Bioprinting of Tumor Microenvironment

“…Through adjustments to the flow rate of immiscible fluids, this method enables generation of highly monodispersed droplets with a production speed spanning from 10-1000 droplets per second[ 89 ]. Typically, there are 3 types of microfluidic configurations for passive droplet generation: cross-flowing/T junction[ 90 , 91 ], flow-focusing[ 92 - 95 ], and co-flowing droplet formation[ 96 ]. Flow-focusing with single-, double-, and multiple-emulsion designs have been extensively utilized ( Figure 2A - f )[ 97 - 99 ].…”

Glioma-on-a-Chip Models

“…Lee et al used a droplet-based microfluidic system to form 3D tumor spheroids (100–130 μm in diameter) including U87 GBM cells for photothermal therapy ( Figure 2 A–E) [ 35 ]. The size of spheroids could be controlled either by manipulating droplet volumes depending on the flow rate in the junction, or by altering the cell concentration.…”

“…Therefore, the droplet-based chip system is appropriate for neurological disease drug studies. Moreover, the viability of the tumor spheroids, after treatment by rGO-BPEI-PEG nanocomposites, declined from 91% to 55% following near-infrared (NIR) laser irradiation which proved that rGO-BPEI-PEG nanocomposites are a potential photothermal therapy (PTT) agent for 3D tumor spheroids acquired from droplets [ 35 ].…”

“…( D ) Results of NIR laser irradiation on the cell viability of U87MG brain tumors after being treated with rGO-BPEI-PEG nanocomposites (red bars) and control experiments without the addition of rGO-BPEI-PEG nanocomposites (black bars). ( E ) Correlation of oil flow rate in the junction to the concentration of encapsulated cells in a single droplet [ 35 ]. Reproduced with permission from [ 35 ].…”

“…( E ) Correlation of oil flow rate in the junction to the concentration of encapsulated cells in a single droplet [ 35 ]. Reproduced with permission from [ 35 ]. ( F ) Schematic view of hydrogel microfluidic co-culture device.…”