Simulation of complex transport of nanoparticles around a tumor using tumor-microenvironment-on-chip

Organ-Tumor-on-a-Chip for Chemosensitivity Assay: A Critical Review

With a mortality rate over 580,000 per year, cancer is still one of the leading causes of death worldwide. However, the emerging field of microfluidics can potentially shed light on this puzzling disease. Unique characteristics of microfluidic chips (also known as micro-total analysis system) make them excellent candidates for biological applications. The ex vivo approach of tumor-on-a-chip is becoming an indispensable part of personalized medicine and can replace in vivo animal testing as well as conventional in vitro methods. In tumor-on-a-chip, the complex three-dimensional (3D) nature of malignant tumor is co-cultured on a microfluidic chip and high throughput screening tools to evaluate the efficacy of anticancer drugs are integrated on the same chip. In this article, we critically review the cutting edge advances in this field and mainly categorize each tumor-on-a-chip work based on its primary organ. Specifically, design, fabrication and characterization of tumor microenvironment; cell culture technique; transferring mechanism of cultured cells into the microchip; concentration gradient generators for drug delivery; in vitro screening assays of drug efficacy; and pros and cons of each microfluidic platform used in the recent literature will be discussed separately for the tumor of following organs: (1) Lung; (2) Bone marrow; (3) Brain; (4) Breast; (5) Urinary system (kidney, bladder and prostate); (6) Intestine; and (7) Liver. By comparing these microchips, we intend to demonstrate the unique design considerations of each tumor-on-a-chip based on primary organ, e.g., how microfluidic platform of lung-tumor-on-a-chip may differ from liver-tumor-on-a-chip. In addition, the importance of heart–liver–intestine co-culture with microvasculature in tumor-on-a-chip devices for in vitro chemosensitivity assay will be discussed. Such system would be able to completely evaluate the absorption, distribution, metabolism, excretion and toxicity (ADMET) of anticancer drugs and more realistically recapitulate tumor in vivo-like microenvironment.

Characterization of Cell-Type-Specific Drug Transport and Resistance of Breast Cancers Using Tumor-Microenvironment-on-Chip

Heterogeneous response and resistance of cancer cells to chemotherapeutic drugs pose a significant challenge for successful cancer treatments. In this study, an integrated experimental and theoretical analysis of cellular drug transport was developed. The experimental platform, called tumor-microenvironment-on-chip (T-MOC), is a microfluidic platform where cancer cells were cultured within a three-dimensional extracellular matrix perfused with interstitial fluid. Three types of human breast cancer cell lines (MCF-7, MDA-MB-231, and SUM-159PT) were cultured on this T-MOC platform, and their drug response and resistance to doxorubicin were characterized by time-lapse quantitative fluorescence microscopy. To study the effects of nanoparticle-mediated drug delivery, the transport and action of doxorubicin encapsulated nanoparticles were also examined. Based on the experimental data obtained, a theoretical model was developed to quantify and ultimately predict the cellular transport processes of drugs cell-type specifically. The results demonstrate that the cellular drug transport can be cell-type-specifically quantified by rate constants representing the uptake and efflux of doxorubicin across the cellular membrane.

Chemotaxis-driven assembly of endothelial barrier in a tumor-on-a-chip platform

The integration of three-dimensional micropatterning with microfluidics provides a unique opportunity to create perfusable tissue constructs in vitro. Herein, we have used this approach to create a tumor-on-a-chip with an endothelial barrier. Specifically, we photopatterned a mixture of endothelial cells and cancer spheroids within a gelatin methacrylate (GelMA) hydrogel inside a microfluidic device. The differential motility of endothelial and cancer cells in response to a controlled morphogen gradient across the cell-laden network drove the migration of endothelial cells to the periphery while maintaining the cancer cells within the interior of the hydrogel. The resultant endothelial cell layer forming cell-cell contact via VE-cadherin junctions was found to encompass the entire GelMA hydrogel structure. Furthermore, we have also examined the potential of such a tumor-on-a-chip system as a drug screening platform using doxorubicin, a model cancer drug.

Controlled Drug Release and Chemotherapy Response in a Novel Acoustofluidic 3D Tumor Platform

Overcoming transport barriers to delivery of therapeutic agents in tumors remains a major challenge. Focused ultrasound (FUS), in combination with modern nanomedicine drug formulations, offers the ability to maximize drug transport to tumor tissue while minimizing toxicity to normal tissue. This potential remains unfulfilled due to the limitations of current approaches in accurately assessing and quantifying how FUS modulates drug transport in solid tumors. A novel acoustofluidic platform is developed by integrating a physiologically relevant 3D microfluidic device and a FUS system with a closed-loop controller to study drug transport and assess the response of cancer cells to chemotherapy in real time using live cell microscopy. FUS-induced heating triggers local release of the chemotherapeutic agent doxorubicin from a liposomal carrier and results in higher cellular drug uptake in the FUS focal region. This differential drug uptake induces locally confined DNA damage and glioblastoma cell death in the 3D environment. The capabilities of acoustofluidics for accurate control of drug release and monitoring of localized cell response are demonstrated in a 3D in vitro tumor mode. This has important implications for developing novel strategies to deliver therapeutic agents directly to the tumor tissue while sparing healthy tissue.

Recapitulation of complex transport and action of drugs at the tumor microenvironment using tumor-microenvironment-on-chip

Targeted delivery aims to selectively distribute drugs to targeted tumor tissues but not to healthy tissues. This can address many clinical challenges by maximizing the efficacy but minimizing the toxicity of anti-cancer drugs. However, a complex tumor microenvironment poses various barriers hindering the transport of drugs and drug delivery systems. New tumor models that allow for the systematic study of these complex environments are highly desired to provide reliable test beds to develop drug delivery systems for targeted delivery. Recently, research efforts have yielded new in vitro tumor models, the so called tumor-microenvironment-on-chip, that recapitulate certain characteristics of the tumor microenvironment. These new models show benefits over other conventional tumor models, and have the potential to accelerate drug discovery and enable precision medicine. However, further research is warranted to overcome their limitations and to properly interpret the data obtained from these models. In this article, key features of the in vivo tumor microenvironment that are relevant to drug transport processes for targeted delivery were discussed, and the current status and challenges for developing in vitro transport model systems were reviewed.