Hybrid-integrated devices for mimicking malignant brain tumors ("tumor-on-a-chip") for in vitro development of targeted drug delivery and personalized therapy approaches

Abstract

Acute and requiring attention problem of oncotheranostics is a necessity for the urgent development of operative and precise diagnostics methods, followed by efficient therapy, to significantly reduce disability and mortality of citizens. A perspective way to achieve efficient personalized treatment is to use methods for operative evaluation of the individual drug load, properties of specific tumors and the effectiveness of selected therapy, and other actual features of pathology. Among the vast diversity of tumor types-brain tumors are the most invasive and malignant in humans with poor survival after diagnosis. Among brain tumors glioblastoma shows exceptionally high mortality. More studies are urgently needed to understand the risk factors and improve therapy approaches. One of the actively developing approaches is the tumor-on-a-chip (ToC) concept. This review examines the achievements of recent years in the field of ToC system developments. The basics of microfluidic chips technologies are considered in the context of their applications in solving oncological problems. Then the basic principles of tumors cultivation are considered to evaluate the main challengers in implementation of microfluidic devices, for growing cell cultures and possibilities of their treatment and observation. The main achievements in the culture types diversity approaches and their advantages are being analyzed. The modeling of angiogenesis and blood-brain barrier (BBB) on a chip, being a principally important elements of the life system, were considered in detail. The most interesting examples and achievements in the field of tumor-on-a-chip developments have been presented.

Keywords: blood-brain barrier; brain tumor; microfluidic devices; organ-on-a-chip; tumor-on-a-chip.

Figure 1

Classification of organ-on-a-chip models for mimicking brain tumors according to various criteria.

Figure 2

Comparison of the most common materials for the ToCs fabrication.

Figure 3

Comparison of common technologies for ToC fabrication.

Figure 4

Tumor microenvironment. Tumor cells hijack different cellular and non-cellular non-malignant components of TME to promote their own growth and survival under hostile conditions. Meanwhile, the mediators for such contacts can be soluble factors (chemokines/cytokines/growth factors, etc.), or those that enable horizontal genetic/biomaterial transfer including cfDNA, apoptotic bodies, CTCs, and exosomes. Reprinted from Baghban et al. (106), license CC BY 4.0.

Figure 5

Schematic cross-sectional view of main tumor cultivation chambers integrated in microfluidic systems for cultivation of 2D culture (A), spheroids (B), and 3D heterogeneous co-culture (C). 1—substrate (polymer, glass, silicon, etc.), 2—profile for nutrient flow arrangement, 3—porous support, 4—protein layer, 5—gas delivery channel, 6—casing, 7—tumor cells, 8—growth medium, 9—gas inlet, 10—pharmaceutical compounds inlet, and 11—liquid nutrient inlet.

Figure 6

ToC consists of channels that can be loaded with media and cells and can support perfusion culture. Reprinted from Jeong et al. (142), license CC BY 4.0.

Figure 7

Setup of microfluidic cartridge and miniaturized incubator microscope platform. (a) SEM image of microcavity with micro hole array membrane (1.6 mm x 1.6 mm). (b) SEM image of micro hole array with hole distance 10 μm. (c) Microfluidic cartridge with connected tubing and cables for impedance measurement. This cartridge is integrated in the miniaturized incubator microscope. (d) Incubator microscope with inserted microfluidic cartridge and lid, for bright field imaging and cell cultivation under controlled temperature. (e) Schematic illustration of the microfluidic cartridge. The electrodes (yellow) are positioned in the two fluidic channels. The electric current flows between the electrodes through the pores in the membrane (dashed line). (f) Schematics of experimental setup with two platform modules for parallel or serial operation. Reprinted from Kohl et al. (164), license CC BY 4.0.

Figure 8

Samples sliced and seeded in the microfluidic device; (A, B) top view. (C) Side view. The bar is 100 μm. Reprinted from Chong et al. (108), license CC BY 4.0.

Figure 9

Testing of how NETs production outside the collagen region induces tumor invasion within a TIME, by separate stimulated of the neutrophils in the microchannel with 500 nM PMA. (A) Schematic illustration of the different steps shows that the TIME-on-Chip easily enables on-demand attachment and detachment of the components to initially induce the neutrophils in the microchannel to produce NETs, add the conditioned media to the spheroids, and re-attach the device to enable NETs-spheroid co-culture for analysis. (B) More than 60% of the neutrophils in the microchannel NETosed upon PMA stimulation for 6 h. But even after 24 h of co-culture, the spheroids do not appear significantly distorted as seen in the brightfield images (scale bars represent 150 μm). (C) No significant difference was observed in the distortion of the spheroids with the PMA-stimulated NETs present in the channel or with direct stimulation of the spheroids with PMA (data collected for n = 3 spheroids, mean ± SEM, t-test, ns, not significant). Reprinted from Surendran et al. (168), license CC BY 4.0.

Figure 10

In vitro tumoroid invasion platform. (A) Single cell suspension seeded through the loading zone of a self-filling microwell array. (B) Tumoroids were formed after 4 days of culture and were transferred into the tumor-on-a-chip platform. (C) The platform was capable of growing tumoroids in four different chambers, each addressed separately, with an inlet and outlet for collagenase treatment. (D) Tumoroids embedded in bovine fibril collagen hydrogel were loaded into the open surface tumoroid-on-a-chip platform and their growth and invasion were monitored over time. Reprinted from Amereh et al. (169), license CC BY 4.0.

Figure 11

Schematic presentation of tissue types and indication of main sensor.

Figure 12

A diaphragm structure of a piezoresistive pressure sensor with a combination of a four-petal membrane, four narrow beams and a central boss (PMNBCB) for low-pressure ranges. General outlook (A), and cross-section (B). The finite element method (FEM) was used to estimate the stress distribution and analyze the inherent structure's deflection for different parameters. Reprinted from Tran et al. (178), license CC BY 4.0.

Figure 13

Design concept of ref-OECT-based E-AB sensor. (A) Schematic image of the ref-OECT-based E-AB sensor. (B) Sensing mechanism of the ref-OECT-based E-AB sensor for TGF-β1. Without the existence of TGF-β1, the methylene blue (MB) redox reporter is closer to the gate electrode surface, which results in a high gate current (IG) as well as a larger channel current modulation (IDS). In the presence of TGF-β1, a conformational change occurs in the aptamer, and the MB redox reporter moves further from the gate electrode surface, which results in low gate current and smaller channel current modulation. Reprinted from Ji et al. (191), license CC BY 4.0.

Figure 14

Schematic representation of the biosensor device: the integrated optical Mach–Zehnder interferometer (MZI) for sensing the analyte (1), the microfluidic apparatus (syringe pump, tubes, PDMS microchannel) for fluid sample providing (2), the signal processing unit, namely a photomultiplier tubes (PMT) detector (3) with an oscilloscope (4), the microheater structure for bias point tuning (5). The working principle of the device is also presented: the evanescent field detection is based on the phase difference in the propagating light of the measuring arm (yellow waves) compared to the ones of the reference arm (red waves) (6). Phase difference can be induced by the binding of the target spike protein S1 subunit to the antibody-covered surface of the measuring arm. Reprinted from Petrovszki et al. (196), license CC BY 4.0.

Figure 15

Schematic of the microfluidic system used to mimic the stepwise endothelial-pericyte interaction. (A) The microfluidic device is composed of a central vessel channel, two adjoining media channels, and the outermost fibroblast channel. The vascular network covered by the pericytes was formed in the central channel with assistance from the lateral fibroblasts. (B) The experimental scheme of the stepwise angiogenic process. ECs and pericytes were mixed and attached to the left side of the vessel channel. ECs sprout through the fibrin gel to establish a blood vessel network, and pericytes follow behind the vessel. (C, D) Confocal images show EC patterning prior to pericyte association during the first 3 days (C), and matured pericytes covered the perfusable EC network on day 6 (D). Scale bars, 100 μm. Reprinted from Kim et al. (216), license CC BY 4.0.

Figure 16

Endothelial cell coating of conduits to mimic blood-tissue barrier function. For optimized coating of inner channel linings, a programmable 3D orbital shaker was developed that halts rotation at distinct positions for defined times to achieve optimized endothelial cell adhesion (A). Compared to manual flipping of the fluidic chips [(B), top panels], the inner surfaces of shaker-incubated tissues are homogenously coated with green fluorescent endothelial cells (HUVEC/hTERT-EYFP) as imaged by confocal microscopy [(B), bottom panels, scale bar 50 μm]. Tissue chips with fibroblasts (HFF/hTERT-ECFP) in the hydrogel matrix and hollow channels with or without endothelial cells (HUVEC/hTERT-EYFP) were perfused with red fluorescent 70 kDa dextran rhodamine B conjugate (0.25 mg ml⁻¹) to assess diffusion into the hydrogel matrix within 30 min (C). Left panels: fibroblast containing hydrogels with uncoated channels. Right panels: endothelial cell coating using orbital shaker procedure. Size marker 200 μm. Red fluorescence in the matrix after 30 min corresponds to the diffusion distance of dextran beads and thus to the endothelial barrier function. Graph shows comparison in red fluorescence between non-coated channels and channels covered with endothelial cells (D). Shown is the mean of three independent experiments. Reprinted from Nothdurfter et al. (217), license CC BY 4.0. Statistical significance was assessed with student's t-test (^**p < 0.01).

Figure 17

A scheme showing the application of various BBB models in drug development and pharmaceutical research. Reprinted from Augustine et al. (251), license CC BY 4.0.