A high-throughput, open-space and reusable microfluidic chip for combinational drug screening on tumor spheroids

Surface Deformation of Biocompatible Materials: Recent Advances in Biological Applications

The surface topography of substrates is a crucial factor that determines the interaction with biological materials in bioengineering research. Therefore, it is important to appropriately modify the surface topography according to the research purpose. Surface topography can be fabricated in various forms, such as wrinkles, creases, and ridges using surface deformation techniques, which can contribute to the performance enhancement of cell chips, organ chips, and biosensors. This review provides a comprehensive overview of the characteristics of soft, hard, and hybrid substrates used in the bioengineering field and the surface deformation techniques applied to the substrates. Furthermore, this review summarizes the cases of cell-based research and other applications, such as biosensor research, that utilize surface deformation techniques. In cell-based research, various studies have reported optimized cell behavior and differentiation through surface deformation, while, in the biosensor and biofilm fields, performance improvement cases due to surface deformation have been reported. Through these studies, we confirm the contribution of surface deformation techniques to the advancement of the bioengineering field. In the future, it is expected that the application of surface deformation techniques to the real-time interaction analysis between biological materials and dynamically deformable substrates will increase the utilization and importance of these techniques in various fields, including cell research and biosensors.

Microfluidics in High-Throughput Drug Screening: Organ-on-a-Chip and C. elegans-Based Innovations

The development of therapeutic interventions for diseases necessitates a crucial step known as drug screening, wherein potential substances with medicinal properties are rigorously evaluated. This process has undergone a transformative evolution, driven by the imperative need for more efficient, rapid, and high-throughput screening platforms. Among these, microfluidic systems have emerged as the epitome of efficiency, enabling the screening of drug candidates with unprecedented speed and minimal sample consumption. This review paper explores the cutting-edge landscape of microfluidic-based drug screening platforms, with a specific emphasis on two pioneering approaches: organ-on-a-chip and C. elegans-based chips. Organ-on-a-chip technology harnesses human-derived cells to recreate the physiological functions of human organs, offering an invaluable tool for assessing drug efficacy and toxicity. In parallel, C. elegans-based chips, boasting up to 60% genetic homology with humans and a remarkable affinity for microfluidic systems, have proven to be robust models for drug screening. Our comprehensive review endeavors to provide readers with a profound understanding of the fundamental principles, advantages, and challenges associated with these innovative drug screening platforms. We delve into the latest breakthroughs and practical applications in this burgeoning field, illuminating the pivotal role these platforms play in expediting drug discovery and development. Furthermore, we engage in a forward-looking discussion to delineate the future directions and untapped potential inherent in these transformative technologies. Through this review, we aim to contribute to the collective knowledge base in the realm of drug screening, providing valuable insights to researchers, clinicians, and stakeholders alike. We invite readers to embark on a journey into the realm of microfluidic-based drug screening platforms, fostering a deeper appreciation for their significance and promising avenues yet to be explored.

A magnetically controlled microfluidic device for concentration dependent in vitro testing of anticancer drug

Compartmentalizing magnetically controlled drug molecules is critical in several bioanalytical trials and tests, such as drug screening, digital PCR, magnetic hyperthermia, and controlled magnetic drug targeting (MDT). However, several studies have focused on diluting the nonmagnetic drug using various passive devices based on traditional microfabrication and 3D printing techniques, leading to the requirement of sterilized cleanroom facilities and expensive equipment, respectively. This work develops a strategically designed and straightforward lithography-free process to fabricate a magnetic microfluidic device using a multilayered PMMA substrate for concentration-dependent compartmentalization of a magnetically controlled anticancer drug. The device contains an array of outlet chamber wells connected to five primary separation microfluidic channels for collecting different drug concentrations. The microfluidic design geometry, magnet configuration, and fluid flow rate are optimized using FEM (Finite Element Method) simulations to attain a systematic concentration gradient region within the microfluidic channel. A stair-step-like patterned magnet creates an attenuating magnetic force between 0.01-0.24 pN on magnetic nanoparticles, capable of generating the concentration gradient for the clinically acceptable flow range of Q = 0.6-1.1 μL min-1. The chamber well of the device is designed to adapt different cell cultures and simultaneously expose five different concentrations by introducing a predefined concentration from the inlet. As a result, this innovative design provides a predictable concentration control in each well through a single injection port to minimize drug loading errors. The concentration gradient generation of the drug and exposure to cell culture chambers are controlled using the magnetic and drag forces capable of running a time-varying dose screening experiment. The concentration range of the compartmentalized drug sample in the device is determined as 10-480 μg mL-1 using inductively coupled plasma mass spectrometry (ICPMS) measurement and fluorescence intensity. The cytotoxicity test of MCF7 and NIH3T3 cells using the device was consistent with the results obtained with the manual dilution method, resulting in the reusability of the device.

3D vascularized microphysiological system for investigation of tumor-endothelial crosstalk in anti-cancer drug resistance

Despite the advantages of microfluidic system in drug screening, vascular systems responsible for the transport of drugs and nutrients have been hardly considered in the microfluidic-based chemotherapeutic screening. Considering the physiological characteristics of highly vascularized urinary tumors, we here investigated the chemotherapeutic response of bladder tumor cells using a vascularized tumor on a chip. The microfluidic chip was designed to have open-top region for tumor sample introduction and hydrophilic rail for spontaneous hydrogel patterning, which contributed to the construction of tumor-hydrogel-endothelium interfaces in a spatiotemporal on-demand manner. Utilizing the chip where intravascularly injected cisplatin diffuse across the endothelium and transport into tumor samples, chemotherapeutic responses of cisplatin-resistant or -susceptible bladder tumor cells were evaluated, showing the preservation of cellular drug resistance even within the chip. The open-top structure also enabled the direct harvest of tumor samples and post analysis in terms of secretome and gene expressions. Comparing the cisplatin efficacy of the cisplatin-resistant tumor cells in the presence or absence of endothelium, we found that the proliferation rates of tumor cells were increased in the vasculature-incorporated chip. These have suggested that our vascularized tumor chip allows the establishment of vascular-gel-tumor interfaces in spatiotemporal manners and further enables investigations of chemotherapeutic screening.

Microfluidic Devices: A Tool for Nanoparticle Synthesis and Performance Evaluation

The use of nanoparticles (NPs) in nanomedicine holds great promise for the treatment of diseases for which conventional therapies present serious limitations. Additionally, NPs can drastically improve early diagnosis and follow-up of many disorders. However, to harness their full capabilities, they must be precisely designed, produced, and tested in relevant models. Microfluidic systems can simulate dynamic fluid flows, gradients, specific microenvironments, and multiorgan complexes, providing an efficient and cost-effective approach for both NPs synthesis and screening. Microfluidic technologies allow for the synthesis of NPs under controlled conditions, enhancing batch-to-batch reproducibility. Moreover, due to the versatility of microfluidic devices, it is possible to generate and customize endless platforms for rapid and efficient in vitro and in vivo screening of NPs' performance. Indeed, microfluidic devices show great potential as advanced systems for small organism manipulation and immobilization. In this review, first we summarize the major microfluidic platforms that allow for controlled NPs synthesis. Next, we will discuss the most innovative microfluidic platforms that enable mimicking in vitro environments as well as give insights into organism-on-a-chip and their promising application for NPs screening. We conclude this review with a critical assessment of the current challenges and possible future directions of microfluidic systems in NPs synthesis and screening to impact the field of nanomedicine.

Convenient tumor 3D spheroid arrays manufacturing via acoustic excited bubbles for in situ drug screening

The quick and convenient fabrication of in vitro tumor spheroids models has been pursued for clinical drug discovery and personalized therapy. Here, uniform three-dimensional (3D) tumor spheroids are quickly constructed by acoustically excited bubble arrays in a microfluidic chip and performed drug response testing in situ. In detail, bubble oscillation excited by acoustic waves induces second radiation force, resulting in the cells rotating and aggregating into tumor spheroids, which obtain controllable sizes ranging from 30 to 300 μm. These spherical tumor models are located in microfluidic networks, where drug solutions with gradient concentrations are generated from 0 to 18 mg mL^-1, so that the cell spheroids response to drugs can be monitored conveniently and efficiently. This one-step tumor spheroids manufacturing method significantly reduces the model construction time to less than 15 s and increases efficiency by eliminating additional transfer processes. These significant advantages of convenience and high-throughput manufacturing make the tumor models promising for use in tumor treatment and point-of-care diagnosis.

Pressure-Free Assembling of Poly(methyl methacrylate) Microdevices via Microwave-Assisted Solvent Bonding and Its Biomedical Applications

Poly(methyl methacrylate) (PMMA) has become an appealing material for manufacturing microfluidic chips, particularly for biomedical applications, because of its transparency and biocompatibility, making the development of an appropriate bonding strategy critical. In our research, we used acetic acid as a solvent to create a pressure-free assembly of PMMA microdevices. The acetic acid applied between the PMMA slabs was activated by microwave using a household microwave oven to tightly merge the substrates without external pressure such as clamps. The bonding performance was tested and a superior bond strength of 14.95 ± 0.77 MPa was achieved when 70% acetic acid was used. Over a long period, the assembled PMMA device with microchannels did not show any leakage. PMMA microdevices were also built as a serpentine 2D passive micromixer and cell culture platform to demonstrate their applicability. The results demonstrated that the bonding scheme allows for the easy assembly of PMMAs with a low risk of clogging and is highly biocompatible. This method provides for a simple but robust assembly of PMMA microdevices in a short time without requiring expensive instruments.