Microfluidic Platform for Studying Chemotaxis of Adhesive Cells Revealed a Gradient-Dependent Migration and Acceleration of Cancer Stem Cells

The progressive trend of modeling and drug screening systems of breast cancer bone metastasis

Bone metastasis is considered as a considerable challenge for breast cancer patients. Various in vitro and in vivo models have been developed to examine this occurrence. In vitro models are employed to simulate the intricate tumor microenvironment, investigate the interplay between cells and their adjacent microenvironment, and evaluate the effectiveness of therapeutic interventions for tumors. The endeavor to replicate the latency period of bone metastasis in animal models has presented a challenge, primarily due to the necessity of primary tumor removal and the presence of multiple potential metastatic sites.The utilization of novel bone metastasis models, including three-dimensional (3D) models, has been proposed as a promising approach to overcome the constraints associated with conventional 2D and animal models. However, existing 3D models are limited by various factors, such as irregular cellular proliferation, autofluorescence, and changes in genetic and epigenetic expression. The imperative for the advancement of future applications of 3D models lies in their standardization and automation. The utilization of artificial intelligence exhibits the capability to predict cellular behavior through the examination of substrate materials' chemical composition, geometry, and mechanical performance. The implementation of these algorithms possesses the capability to predict the progression and proliferation of cancer. This paper reviewed the mechanisms of bone metastasis following primary breast cancer. Current models of breast cancer bone metastasis, along with their challenges, as well as the future perspectives of using these models for translational drug development, were discussed.

Maximum Emission Peak Over 1500 nm of Organic Assembly for Blood-Brain Barrier-Crossing NIR-IIb Phototheranostics of Orthotopic Glioblastoma

The development of blood-brain barrier (BBB)-crossing phototheranostic agents in second near-infrared window (NIR-II), especially in the range of 1500-1700 nm (NIR-IIb), affords great opportunities for glioblastoma (GBM) management. Herein, an organic assembly (denoted as LET-12) with the maximum absorption peak at 1400 nm and emission peak at 1512 nm with trailing over 1700 nm through the self-assembly of organic small molecule IR-1064 is designed and subsequently decorated with choline and acetylcholine analogs. The LET-12 can effectively cross BBB through the brain's choline-like receptors-mediated transcytosis and accumulated in tumor tissues, thus achieving fluorescence/photoacoustic (FL/PA) duplex imaging of orthotopic GBM with ≈3.0 mm depth and a superior tumor-to-normal tissue signal ratio (20.93 ± 0.59 for FL imaging and 32.63 ± 1.16 for PA imaging, respectively). Owing to its good photothermal conversion ability, the LET-12 also can serve as a photothermal conversion agent, achieving obvious tumor repression of orthotopic murine GBM model after once treatment. The findings indicate that the LET-12 holds great potential for BBB-crossing NIR-IIb phototheranostics of orthotopic GBM. This self-assembly strategy of organic small molecules opens a new avenue for the construction of NIR-IIb phototheranostics.

Biosensors integrated 3D organoid/organ-on-a-chip system: A real-time biomechanical, biophysical, and biochemical monitoring and characterization

As a full-fidelity simulation of human cells, tissues, organs, and even systems at the microscopic scale, Organ-on-a-Chip (OOC) has significant ethical advantages and development potential compared to animal experiments. The need for the design of new drug high-throughput screening platforms and the mechanistic study of human tissues/organs under pathological conditions, the evolving advances in 3D cell biology and engineering, etc., have promoted the updating of technologies in this field, such as the iteration of chip materials and 3D printing, which in turn facilitate the connection of complex multi-organs-on-chips for simulation and the further development of technology-composite new drug high-throughput screening platforms. As the most critical part of organ-on-a-chip design and practical application, verifying the success of organ model modeling, i.e., evaluating various biochemical and physical parameters in OOC devices, is crucial. Therefore, this paper provides a logical and comprehensive review and discussion of the advances in organ-on-a-chip detection and evaluation technologies from a broad perspective, covering the directions of tissue engineering scaffolds, microenvironment, single/multi-organ function, and stimulus-based evaluation, and provides a more comprehensive review of the progress in the significant organ-on-a-chip research areas in the physiological state.

Constructing 3D In Vitro Models of Heterocellular Solid Tumors and Stromal Tissues Using Extrusion-Based Bioprinting

Malignant tumor tissues exhibit inter- and intratumoral heterogeneities, aberrant development, dynamic stromal composition, diverse tissue phenotypes, and cell populations growing within localized mechanical stresses in hypoxic conditions. Experimental tumor models employing engineered systems that isolate and study these complex variables using in vitro techniques are under development as complementary methods to preclinical in vivo models. Here, advances in extrusion bioprinting as an enabling technology to recreate the three-dimensional tumor milieu and its complex heterogeneous characteristics are reviewed. Extrusion bioprinting allows for the deposition of multiple materials, or selected cell types and concentrations, into models based upon physiological features of the tumor. This affords the creation of complex samples with representative extracellular or stromal compositions that replicate the biology of patient tissue. Biomaterial engineering of printable materials that replicate specific features of the tumor microenvironment offer experimental reproducibility, throughput, and physiological relevance compared to animal models. In this review, we describe the potential of extrusion-based bioprinting to recreate the tumor microenvironment within in vitro models.

Biofabrication approaches and regulatory framework of metastatic tumor-on-a-chip models for precision oncology

The complexity of the tumor microenvironment (TME) together with the development of the metastatic process are the main reasons for the failure of conventional anticancer treatment. In recent years, there is an increasing need to advance toward advanced in vitro models of cancer mimicking TME and simulating metastasis to understand the associated mechanisms that are still unknown, and to be able to develop personalized therapy. In this review, the commonly used alternatives and latest advances in biofabrication of tumor‐on‐chips, which allow the generation of the most sophisticated and optimized models for recapitulating the tumor process, are presented. In addition, the advances that have allowed these new models in the area of metastasis, cancer stem cells, and angiogenesis are summarized, as well as the recent integration of multiorgan‐on‐a‐chip systems to recapitulate natural metastasis and pharmacological screening against it. We also analyze, for the first time in the literature, the normative and regulatory framework in which these models could potentially be found, as well as the requirements and processes that must be fulfilled to be commercially implemented as in vitro study model. Moreover, we are focused on the possible regulatory pathways for their clinical application in precision medicine and decision making through the generation of personalized models with patient samples. In conclusion, this review highlights the synergistic combination of three‐dimensional bioprinting systems with the novel tumor/metastasis/multiorgan‐on‐a‐chip systems to generate models for both basic research and clinical applications to have devices useful for personalized oncology.

Uniform Tumor Spheroids on Surface-Optimized Microfluidic Biochips for Reproducible Drug Screening and Personalized Medicine

Spheroids are recognized for resembling the important characteristics of natural tumors in cancer research. However, the lack of controllability of the spheroid size, form, and density in conventional spheroid culture methods reduces the reproducibility and precision of bioassay results and the assessment of drug-dose responses in spheroids. Nonetheless, the accurate prediction of cellular responses to drug compounds is crucial for developing new efficient therapeutic agents and optimizing existing therapeutic strategies for personalized medicine. We developed a surface-optimized PDMS microfluidic biochip to produce uniform and homogenous multicellular spheroids in a reproducible manner. This platform is surface optimized with 10% bovine serum albumin (BSA) to provide cell-repellent properties. Therefore, weak cell-surface interactions lead to the promotion of cell self-aggregations and the production of compact and uniform spheroids. We used a lung cancer cell line (A549), a co-culture model of lung cancer cells (A549) with (primary human osteoblasts, and patient-derived spine metastases cells (BML, bone metastasis secondary to lung). We observed that the behavior of cells cultured in three-dimensional (3D) spheroids within this biochip platform more closely reflects in vivo-like cellular responses to a chemotherapeutic drug, Doxorubicin, rather than on 24-well plates (two-dimensional (2D) model). It was also observed that the co-culture and patient-derived spheroids exhibited resistance to anti-cancer drugs more than the mono-culture spheroids. The repeatability of drug test results in this optimized platform is the hallmark of the reproducibility of uniform spheroids on a chip. This surface-optimized biochip can be a reliable platform to generate homogenous and uniform spheroids to study and monitor the tumor microenvironment and for drug screening.

Strategies for developing complex multi-component in vitro tumor models: Highlights in glioblastoma

In recent years, many research groups have begun to utilize bioengineered in vitro models of cancer to study mechanisms of disease progression, test drug candidates, and develop platforms to advance personalized drug treatment options. Due to advances in cell and tissue engineering over the last few decades, there are now a myriad of tools that can be used to create such in vitro systems. In this review, we describe the considerations one must take when developing model systems that accurately mimic the in vivo tumor microenvironment (TME) and can be used to answer specific scientific questions. We will summarize the importance of cell sourcing in models with one or multiple cell types and outline the importance of choosing biomaterials that accurately mimic the native extracellular matrix (ECM) of the tumor or tissue that is being modeled. We then provide examples of how these two components can be used in concert in a variety of model form factors and conclude by discussing how biofabrication techniques such as bioprinting and organ-on-a-chip fabrication can be used to create highly reproducible complex in vitro models. Since this topic has a broad range of applications, we use the final section of the review to dive deeper into one type of cancer, glioblastoma, to illustrate how these components come together to further our knowledge of cancer biology and move us closer to developing novel drugs and systems that improve patient outcomes.

Cancer Stem Cells in Tumor Modeling: Challenges and Future Directions

Microfluidic tumors-on-chips models have revolutionized anticancer therapeutic research by creating an ideal microenvironment for cancer cells. The tumor microenvironment (TME) includes various cell types and cancer stem cells (CSCs), which are postulated to regulate the growth, invasion, and migratory behavior of tumor cells. In this review, the biological niches of the TME and cancer cell behavior focusing on the behavior of CSCs are summarized. Conventional cancer models such as three-dimensional cultures and organoid models are reviewed. Opportunities for the incorporation of CSCs with tumors-on-chips are then discussed for creating tumor invasion models. Such models will represent a paradigm shift in the cancer community by allowing oncologists and clinicians to predict better which cancer patients will benefit from chemotherapy treatments.

Inhibition of Glioma Cells' Proliferation by Doxorubicin-Loaded Exosomes via Microfluidics

Background

Malignant glioma is a fatal brain cancer. Accumulated evidence has demonstrated that exosomes can cross the blood–brain barrier (BBB), suggesting their potential use as drug delivery vehicles to glioma. Therefore, various loading methods of anticancer agents into exosomes have been developed. However, the loading efficiency of anticancer drugs, such as doxorubicin (DOX) and paclitaxel (PTX), into exosomes is relatively low, thus challenging to improve the drug delivery efficiency to glioma cells (GMs) via exosomes.

Methods

To improve the loading efficiency of doxorubicin into exosomes, a microfluidic device (Exo-Load) was developed. Next, to increase the exosomal delivery of doxorubicin to GMs, autologous exosomes were used for its loading via Exo-Load. Briefly, exosomes from SF7761 stem cells-like- and U251-GMs were isolated and characterized by nano-tracking analysis (NTA), transmission electron microscopy (TEM), and immunogold EM. Finally, doxorubicin was successfully loaded into exosomes with saponin by Exo-Load, and the uptake and functionality of doxorubicin-loaded exosomes for parent GMs were evaluated.

Results

The loading efficiency of DOX into SF7761 stem cells-like- and U251-GMs-derived-exosomes were 19.7% and 7.86% via Exo-Load at the injection flow rate of 50 µL/min, respectively. Interestingly, the loading efficiency of DOX into U251 GMs-derived exosomes was significantly improved to 31.98% by a sigmoid type of Exo-Load at the injection flow rate of 12.5 µL/min. Importantly, DOX-loaded GMs-derived exosomes via Exo-Load inhibited parent GMs’ proliferation more than heterologous GMs, supporting exosomes’ homing effect.

Conclusion

This study revealed that DOX and PTX could be loaded in exosomes via Exo-Load, demonstrating that Exo-Load could be a potential drug-loading device into exosomes with further optimization. This study also demonstrated that the delivery of DOX to SF7761 GMs via their daughter exosomes was much more efficient rather than U251 GMs-derived exosomes, supporting that the use of autologous exosomes could be better for glioma drug targeting.

Tumor-on-a-chip for integrating a 3D tumor microenvironment: chemical and mechanical factors

Tumor progression, including metastasis, is significantly influenced by factors in the tumor microenvironment (TME) such as mechanical force, shear stress, chemotaxis, and hypoxia. At present, most cancer studies investigate tumor metastasis by conventional cell culture methods and animal models, which are limited in data interpretation. Although patient tissue analysis, such as human patient-derived xenografts (PDX), can provide important clinical relevant information, they may not be feasible for functional studies as they are costly and time-consuming. Thus, in vitro three-dimensional (3D) models are rapidly being developed that mimic TME and allow functional investigations of metastatic mechanisms and drug responses. One of those new 3D models is tumor-on-a-chip technology that provides a powerful in vitro platform for cancer research, with the ability to mimic the complex physiological architecture and precise spatiotemporal control. Tumor-on-a-chip technology can provide integrated features including 3D scaffolding, multicellular culture, and a vasculature system to simulate dynamic flow in vivo. Here, we review a select set of recent achievements in tumor-on-a-chip approaches and present potential directions for tumor-on-a-chip systems in the future for areas including mechanical and chemical mimetic systems. We also discuss challenges and perspectives in both biological factors and engineering methods for tumor-on-a-chip progress. These approaches will allow in the future for the tumor-on-a-chip systems to test therapeutic approaches for individuals through using their cancerous cells gathered through approaches like biopsies, which then will contribute toward personalized medicine treatments for improving their outcomes.

Microfluidics for studying metastatic patterns of lung cancer

The incidence of lung cancer continues to rise worldwide. Because the aggressive metastasis of lung cancer cells is the major drawback of successful therapies, the crucial challenge of modern nanomedicine is to develop diagnostic tools to map the molecular mechanisms of metastasis in lung cancer patients. In recent years, microfluidic platforms have been given much attention as tools for novel point-of-care diagnostic, an important aspect being the reconstruction of the body organs and tissues mimicking the in vivo conditions in one simple microdevice. Herein, we present the first comprehensive overview of the microfluidic systems used as innovative tools in the studies of lung cancer metastasis including single cancer cell analysis, endothelial transmigration, distant niches migration and finally neoangiogenesis. The application of the microfluidic systems to study the intercellular crosstalk between lung cancer cells and surrounding tumor microenvironment and the connection with multiple molecular signals coming from the external cellular matrix are discussed. We also focus on recent breakthrough technologies regarding lab-on-chip devices that serve as tools for detecting circulating lung cancer cells. The superiority of microfluidic systems over traditional in vitro cell-based assays with regard to modern nanosafety studies and new cancer drug design and discovery is also addressed. Finally, the current progress and future challenges regarding printable and paper-based microfluidic devices for personalized nanomedicine are summarized.

Enabling cell recovery from 3D cell culture microfluidic devices for tumour microenvironment biomarker profiling

The tumour microenvironment (TME) has recently drawn much attention due to its profound impact on tumour development, drug resistance and patient outcome. There is an increasing interest in new therapies that target the TME. Nonetheless, most established in vitro models fail to include essential cues of the TME. Microfluidics can be used to reproduce the TME in vitro and hence provide valuable insight on tumour evolution and drug sensitivity. However, microfluidics remains far from well-established mainstream molecular and cell biology methods. Therefore, we have developed a quick and straightforward collagenase-based enzymatic method to recover cells embedded in a 3D hydrogel in a microfluidic device with no impact on cell viability. We demonstrate the validity of this method on two different cell lines in a TME microfluidic model. Cells were successfully retrieved with high viability, and we characterised the different cell death mechanisms via AMNIS image cytometry in our model.

Pretumor microenvironment of hepatocellular carcinoma: Cancerization or anticancerization?

BACKGROUND

Tumor microenvironment (TM) has been deeply concerned. However, the pretumor microenvironment (PTM) was poorly understood. The purpose in this study was to explore the possible pathophysiological features of PTM before hepatocellular carcinoma (HCC) appearance.

METHODS

Mouse livers with no swelling but with tumors present elsewhere in the body after subcutaneous injection of H22 in the fore underarm were considered a PTM, HCC tumors presenting far away from the PTM were regarded as a TM, and the healthy livers of mice without injection of H22 were regarded as a physiological microenvironment (PM). The transcriptomes of samples were generated using RNA-seq and validated using RT-qPCR.

RESULTS

Overall, 4483 differentially expressed genes (DEGs) were found in the TM compared with the PTM (TM/PTM), but only 194 were altered in the PTM compared with the PM (PTM/PM). Among those 194 DEGs, 104 displayed upregulation and 90 downregulation. Some of these DEGs could promote the ability to resist cancerization or facilitate cancer metastasis, while others indicated liver impairment. The DEGs were involved in 16 relevant pathways. Additionally, the frequency of alternative splicing (AS) in the DEGs in various samples was positively related to the expression of those DEGs.

CONCLUSIONS

The PTM initiatively armed itself to combat cancerization when its indications appeared although the PTM did not manifest any tissue swelling. However, the cancer cells were negatively influencing immunity to prevent clearance and positively promoting transformation to construct a suitable environment. During transformation by cancer cells, some genes with acquired AS participated in the construction of the PTM. This alteration created an invadable space and an appropriate environment for cancer cells.

Multi-Organs-on-Chips: Towards Long-Term Biomedical Investigations

With advantageous features such as minimizing the cost, time, and sample size requirements, organ-on-a-chip (OOC) systems have garnered enormous interest from researchers for their ability for real-time monitoring of physical parameters by mimicking the in vivo microenvironment and the precise responses of xenobiotics, i.e., drug efficacy and toxicity over conventional two-dimensional (2D) and three-dimensional (3D) cell cultures, as well as animal models. Recent advancements of OOC systems have evidenced the fabrication of 'multi-organ-on-chip' (MOC) models, which connect separated organ chambers together to resemble an ideal pharmacokinetic and pharmacodynamic (PK-PD) model for monitoring the complex interactions between multiple organs and the resultant dynamic responses of multiple organs to pharmaceutical compounds. Numerous varieties of MOC systems have been proposed, mainly focusing on the construction of these multi-organ models, while there are only few studies on how to realize continual, automated, and stable testing, which still remains a significant challenge in the development process of MOCs. Herein, this review emphasizes the recent advancements in realizing long-term testing of MOCs to promote their capability for real-time monitoring of multi-organ interactions and chronic cellular reactions more accurately and steadily over the available chip models. Efforts in this field are still ongoing for better performance in the assessment of preclinical attributes for a new chemical entity. Further, we give a brief overview on the various biomedical applications of long-term testing in MOCs, including several proposed applications and their potential utilization in the future. Finally, we summarize with perspectives.

Microfluidic modelling of the tumor microenvironment for anti-cancer drug development

Cancer is the leading cause of death worldwide. The complex and disorganized tumor microenvironment makes it very difficult to treat this disease. The most common in vitro drug screening method now is based on 2D culture models which poorly represent actual tumors. Therefore, many 3D tumor models which are more physiologically relevant have been developed to conduct in vitro drug screening and alleviate this situation. Among all these models, the microfluidic tumor model has the unique advantage of recapitulating the tumor microenvironment in a comparatively easier and representative fashion. While there are many review papers available on the related topic of microfluidic tumor models, in this review we aim to focus more on the possibility of generating "clinically actionable information" from these microfluidic systems, besides scientific insight. Our topics cover the tumor microenvironment, conventional 2D and 3D cultures, animal models, and microfluidic tumor models, emphasizing their link to anti-cancer drug discovery and personalized medicine.

A PDMS Device Coupled with Culture Dish for In Vitro Cell Migration Assay

Cell migration and invasion are important factors during tumor progression and metastasis. Wound-healing assay and the Boyden chamber assay are efficient tools to investigate tumor development because both of them could be applied to measure cell migration rate. Therefore, a simple and integrated polydimethylsiloxane (PDMS) device was developed for cell migration assay, which could perform quantitative evaluation of cell migration behaviors, especially for the wound-healing assay. The integrated device was composed of three units, which included cell culture dish, PDMS chamber, and wound generation mold. The PDMS chamber was integrated with cell culture chamber and could perform six experiments under different conditions of stimuli simultaneously. To verify the function of this device, it was utilized to explore the tumor cell migration behaviors under different concentrations of fetal bovine serum (FBS) and transforming growth factor (TGF-β) at different time points. This device has the unique capability to create the "wound" area in parallel during cell migration assay and provides a simple and efficient platform for investigating cell migration assay in biomedical application.

3D cellular invasion platforms: how do paper-based cultures stack up?

Cellular invasion is the gateway to metastasis, which is the leading cause of cancer-related deaths. Invasion is driven by a number of chemical and mechanical stresses that arise in the tumor microenvironment. In vitro assays are needed for the systematic study of cancer progress. To be truly predictive, these assays must generate tissue-like environments that can be experimentally controlled and manipulated. While two-dimensional (2D) monolayer cultures are easily assembled and evaluated, they lack the extracellular components needed to assess invasion. Three-dimensional (3D) cultures are better suited for invasion studies because they generate cellular phenotypes that are more representative of those found in vivo. This feature article provides an overview of four invasion platforms. We focus on paper-based cultures, an emerging 3D culture platform capable of generating tissue-like structures and quantifying cellular invasion. Paper-based cultures are as easily assembled and analyzed as monolayers, but provide an experimentally powerful platform capable of supporting: co-cultures and representative extracellular environments; experimentally controlled gradients; readouts capable of quantifying, discerning, and separating cells based on their invasiveness. With a series of examples we highlight the potential of paper-based cultures, and discuss how they stack up against other invasion platforms.

Microfluidic platform for probing cancer cells migration property under periodic mechanical confinement

Cancer cell migration and invasion, which are involved in tumour metastasis, are hard to predict and control. Numerous studies have demonstrated that physical cues influence cancer cell migration and affect tumour metastasis. In this study, we proposed the use of a microchannel chip equipped with a number of vertical constrictions to produce periodic compression forces on cells passing through narrow channels. The chip with repeated vertical confinement was applied on adherent MHCC-97L liver cancer cells and suspended OCI-AML leukaemia cells to determine the migration ability of these cancer cells. Given the stimulation of the periodic mechanical confinement on-chip, the migration ability of cancer cells was promoted. Moreover, the migration speed increased as the stimulation was enhanced. Both AFM nanoindentation and optical stretching tests on cancer cells were performed to measure their mechanical property. After confinement stimulation, the cancer cells possessed higher deformability and lower stiffness than non-stimulating cells. The confinement stimulation altered the cell cytoskeleton, which governs the migration speed. This phenomenon was determined through gene expression analysis. The proposed on-chip cell migration assays will help characterise the migration property of cancer cells and benefit the development of new therapeutic strategies for metastasis.

Cell migration in microengineered tumor environments

Recent advances in microengineered cell migration platforms are discussed critically with a focus on how cell migration is influenced by engineered tumor microenvironments, the medical relevance being to understand how tumor microenvironments may promote or suppress the progression of cancer. We first introduce key findings in cancer cell migration under the influence of the physical environment, which is systematically controlled by microengineering technology, followed by multi-cues of physico-chemical factors, which represent the complexity of the tumor environment. Recognizing that cancer cells constantly communicate not only with each other but also with tumor-associated cells such as vascular, fibroblast, and immune cells, and also with non-cellular components, it follows that cell motility in tumor microenvironments, especially metastasis via the invasion of cancer cells into the extracellular matrix and other tissues, is closely related to the malignancy of cancer-related mortality. Medical relevance of forefront research realized in microfabricated devices, such as single cell sorting based on the analysis of cell migration behavior, may assist personalized theragnostics based on the cell migration phenotype. Furthermore, we urge development of theory and numerical understanding of single or collective cell migration in microengineered platforms to gain new insights in cancer metastasis and in therapeutic strategies.

Development of a shear stress-free microfluidic gradient generator capable of quantitatively analyzing single-cell morphology

Microfluidics, the science of engineering fluid streams at the micrometer scale, offers unique tools for creating and controlling gradients of soluble compounds. Gradient generation can be used to recreate complex physiological microenvironments, but is also useful for screening purposes. For example, in a single experiment, adherent cells can be exposed to a range of concentrations of the compound of interest, enabling high-content analysis of cell behaviour and enhancing throughput. In this study, we present the development of a microfluidic screening platform where, by means of diffusion, gradients of soluble compounds can be generated and sustained. This platform enables the culture of adherent cells under shear stress-free conditions, and their exposure to a soluble compound in a concentration gradient-wise manner. The platform consists of five serial cell culture chambers, all coupled to two lateral fluid supply channels that are used for gradient generation through a source-sink mechanism. Furthermore, an additional inlet and outlet are used for cell seeding inside the chambers. Finite element modeling was used for the optimization of the design of the platform and for validation of the dynamics of gradient generation. Then, as a proof-of-concept, human osteosarcoma MG-63 cells were cultured inside the platform and exposed to a gradient of Cytochalasin D, an actin polymerization inhibitor. This set-up allowed us to analyze cell morphological changes over time, including cell area and eccentricity measurements, as a function of Cytochalasin D concentration by using fluorescence image-based cytometry.

Integrated Microfluidic Platform with Multiple Functions To Probe Tumor-Endothelial Cell Interaction

Interaction between tumor and endothelial cells could affect tumor growth and progression and induce drug resistance during cancer therapy. Investigation of tumor-endothelial cell interaction involves cell coculture, protein detection, and analysis of drug metabolites, which are complicated and time-consuming. In this work, we present an integrated microfluidic device with three individual components (cell coculture component, protein detection component, and pretreatment component for drug metabolites) to probe the interaction between tumor and endothelial cells. Cocultured cervical carcinoma cells (CaSki cells) and human umbilical vein endothelial cells (HUVECs) show higher resistance to chemotherapeutic agents than single-cultured cells, indicated by higher cell viability, increased expression of angiogenic proteins, and elevated level of paclitaxel metabolites under coculture conditions. This integrated microfluidic platform with multiple functions facilitates understanding of the interaction between tumor and endothelial cells, and it may become a promising tool for drug screening within an engineered tumor microenvironment.

An integrated method for cell isolation and migration on a chip

Tumour cell migration has an important impact on tumour metastasis. Magnetic manipulation is an ascendant method for guiding and patterning cells. Here, a unique miniaturized microfluidic chip integrating cell isolation and migration assay was designed to isolate and investigate cell migration. The chip was fabricated and composed of a magnet adapter, a polytetrafluoroethylene(PDMS) microfluidic chip and six magnetic rings. This device was used to isolate MCF-7 cells from MDA-MB-231-RFP cells and evaluate the effects of TGF-β on MCF-7 cells. First, the two cell types were mixed and incubated with magnetic beads modified with an anti-EpCAM antibody. Then, they were slowly introduced into the chip. MCF-7 cells bond to the magnetic beads in a ring-shaped pattern, while MDA-MB-231-RFP cells were washed away by PBS. Cell viability was examined during culturing in the micro-channel. The effects of TGF-β on MCF-7 cells were evaluated by migration distance and protein expression. The integrated method presented here is novel, low-cost and easy for performing cell isolation and migration assay. The method could be beneficial for developing microfluidic device applications for cancer metastasis research and could provide a new method for biological experimentation.

Transparent and Gas-Permeable Liquid Marbles for Culturing and Drug Sensitivity Test of Tumor Spheroids

Transparent nanoparticle-based liquid marbles with high gas-permeability are prepared to culture tumor spheroids in 3D without the need of supplementary growth factor. The culturing process of spheroids from a population of cancer cells or a single cell in the transparent liquid marbles can be optically recorded continuously. Compared to monolayer cells and spheroids generated in multiwell plate, tumor spheroids cultured in the liquid marbles show enhanced viability under the treatment of chemotherapeutic drugs and small interfering RNA.

Chemoresistant lung cancer stem cells display high DNA repair capability to remove cisplatin-induced DNA damage

BACKGROUND AND PURPOSE

The persistence of lung cancer stem cells (LCSCs) has been proposed to be the main factor responsible for the recurrence of lung cancer as they are highly resistant to conventional chemotherapy. However, the underlying mechanisms are still unclear.

EXPERIMENTAL APPROACH

We examined the cellular response of a human LCSC line to treatment with cisplatin, a DNA-damaging anticancer drug that is used extensively in the clinic. We compared the response to cisplatin of LCSCs and differentiated LCSCs (dLCSCs) by determining the viability of these cells, and their ability to accumulate cisplatin and to implement genomic and transcription-coupled DNA repair. We also investigated the transcription profiles of genes related to drug transport and DNA repair.

KEY RESULTS

LCSCs were found to be more stem-like, and more resistant to cisplatin-induced cytotoxicity than dLCSCs, confirming their drug resistance properties. LCSCs accumulated less cisplatin intracellularly than dLCSCs and showed less DNA damage, potentially due to their ability to down-regulate AQP2 and CTR1. The results of the transcription-coupled repair of cisplatin-DNA cross-links indicated a higher level of repair of DNA damage in LCSCs than in dLCSCs. In addition, LCSCs showed a greater ability to repair cisplatin-DNA interstrand cross-links than dLCSCs; this involved the activation of various DNA repair pathways.

CONCLUSIONS AND IMPLICATIONS

Our results further clarify the mechanism of cisplatin resistance in LCSCs in terms of reduced cisplatin uptake and enhanced ability to implement DNA repairs. These findings may aid in the design of the next-generation of platinum-based anticancer drugs.

PDMS-based microfluidic devices using commoditized PCBs as masters with no specialized equipment required

A simple, convenient and reliable approach used to prepare general polymer PDMS-based microfluidic devices with a minimal requirement for equipment.

Cell migration microfluidics for electrotaxis-based heterogeneity study of lung cancer cells

Tumor metastasis involves the migration of cells from primary site to a distant location. Recently, it was established that cancer cells from the same tumor were heterogeneous in migratory ability. Numerous studies have demonstrated that cancer cells undergo reorientation and migration directionally under physiological electric field (EF), which has potential implications in metastasis. Microfluidic devices with channel structures of defined dimensions provide controllable microenvironments to enable real-time observation of cell migration. In this study, we developed two polydimethylsiloxane (PDMS)-based microfluidic devices for long-term electrotaxis study. In the first chip, three different intensities of EFs were generated in a single channel to study cell electrotactic behavior with high efficiency. We observed that the lung adenocarcinoma H1975 cells underwent cathodal migration with changing cellular orientation. To address the issue of cell electrotactic heterogeneity, we also developed a cell isolation device integrating cell immobilization structure, stable EF generator and cell retrieval module in one microfluidic chip to sort out different cell subpopulations based on electrotactic ability. High electrotactic and low electrotactic cells were harvested separately for colony formation assay and transcriptional analysis of migration-related genes. The results showed that H1975 cell motility was related to EGFR expression in the absence of EF stimulation, while in the presence of EF it was associated with PTEN expression. Up-regulation of RhoA was observed in cells with high motility, regardless of EF. The easy cell manipulation and precise field control of the microfluidic devices may enable further study of tumor heterogeneity in complex electrotactic environments.

Microfluidic partition with in situ biofabricated semipermeable biopolymer membranes for static gradient generation

We report an in situ biofabrication strategy that conveniently partitions microfluidic networks into physically separated while chemically communicating microchannels with semipermeable biopolymer membranes, which enable the facile generation of static gradients for biomedical applications. The biofabrication of parallel biopolymer membranes was initiated with the dissipation of trapped air bubbles in parallel apertures in polydimethylsiloxane (PDMS) microfluidic devices, followed by tunable membrane growth with precise temporal and spatial control to the desired thickness. Static gradients were generated within minutes and well maintained over time by pure diffusion of molecules through the biofabricated semipermeable membranes. As an example application, the static gradient of alpha factor was generated to study the development of the "shmoo" morphology of yeast over time. The in situ biofabrication provides a simple approach to generate static gradients and an ideal platform for biological applications where flow-free static gradients are indispensable.

Microfluidic Organ/Body-on-a-Chip Devices at the Convergence of Biology and Microengineering

Recent advances in biomedical technologies are mostly related to the convergence of biology with microengineering. For instance, microfluidic devices are now commonly found in most research centers, clinics and hospitals, contributing to more accurate studies and therapies as powerful tools for drug delivery, monitoring of specific analytes, and medical diagnostics. Most remarkably, integration of cellularized constructs within microengineered platforms has enabled the recapitulation of the physiological and pathological conditions of complex tissues and organs. The so-called “organ-on-a-chip” technology, which represents a new avenue in the field of advanced in vitro models, with the potential to revolutionize current approaches to drug screening and toxicology studies. This review aims to highlight recent advances of microfluidic-based devices towards a body-on-a-chip concept, exploring their technology and broad applications in the biomedical field.