Date Published: November 20, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Seo Woo Song, Su Deok Kim, Dong Yoon Oh, Yongju Lee, Amos Chungwon Lee, Yunjin Jeong, Hyung Jong Bae, Daewon Lee, Sumin Lee, Jiyun Kim, Sunghoon Kwon.
Large‐scale screening of sequential drug combinations, wherein the dynamic rewiring of intracellular pathways leads to promising therapeutic effects and improvements in quality of life, is essential for personalized medicine to ensure realistic cost and time requirements and less sample consumption. However, the large‐scale screening requires expensive and complicated liquid handling systems for automation and therefore lowers the accessibility to clinicians or biologists, limiting the full potential of sequential drug combinations in clinical applications and academic investigations. Here, a miniaturized platform for high‐throughput combinatorial drug screening that is “pipetting‐free” and scalable for the screening of sequential drug combinations is presented. The platform uses parallel and bottom‐up formation of a heterogeneous drug‐releasing hydrogel microarray by self‐assembly of drug‐laden hydrogel microparticles. This approach eliminates the need for liquid handling systems and time‐consuming operation in high‐throughput large‐scale screening. In addition, the serial replacement of the drug‐releasing microarray‐on‐a‐chip facilitates different drug exchange in each and every microwell in a simple and highly parallel manner, supporting scalable implementation of multistep combinatorial screening. The proposed strategy can be applied to various forms of combinatorial drug screening with limited amounts of samples and resources, which will broaden the use of the large‐scale screening for precision medicine.
Treating diseases with multiple drugs leads to more complex and elaborate cellular pathway regulation.1 Thus, finding effective drug combinations has been of interest for a long time, and the discovered drug combinations have been applied to cure patients with resistant cancers that were difficult to treat with single‐drug therapy.2, 3 However, the concurrent administration of multiple drugs increases dose exposure in patients at a specific moment and, therefore, has significant potential to result in side effects.4, 5 To address this limitation, sequential treatment with multiple drugs has received much attention.6, 7 Recently, several studies have reported the sequence‐dependency of some drug combinations, which is more powerful than concurrent combinations.8, 9, 10, 11 The underlying principle is the dynamic rewiring of intracellular pathways in which the pretreated drug makes the cell status vulnerable to the post‐treatment drug.12, 13 If such an effective sequential combination can be found for each patient, thus resulting in personalized medicine, it can provide not only a promising therapeutic effect but also help to improve the quality of life by reducing the drug dose given to the patient.4, 5
In this study, we described a large‐scale screening platform to find effective sequential drug combinations. The delivery of encoded drug‐laden microparticles using one‐step pipetting and the self‐assembly of these microparticles to an array of microwells can replace thousands of pipetting operations. For a multistep drug incubation, only a simple exchange of the hydrogel microarray‐on‐a‐chip is required instead of repeating thousands of pipetting operations for every treatment step. Furthermore, since our platform supports the screening of concurrent combinatorial drugs, this technique can apply to the various forms of combination screening. Such a significant decrease in the workload would give hospitals and laboratories with limited resources the opportunity to perform large‐scale, multistep bioassays at an affordable cost and within a reasonable timeframe. Regarding the required number of samples, only 200 cells per microwell were needed, and the uniform seeding of 1600 microwells was possible without a robotic pipette machine through the sealing film‐assisted seeding method. To make this platform usable by other researchers, we designed an easy‐to‐use platform by introducing 3D pillar/hole structures and a multipurpose holder for easy alignment.
Encoded Microparticle Fabrication: Encoded hydrogel microparticles were fabricated via UV photolithography (OmniCure S1500, Excelitas Technology Corp.) with poly(ethylene glycol)‐diacrylate (PEGDA, Mn = 700; Sigma‐Aldrich) and 5 wt% photoinitiator (2‐hydroxy‐2‐methylpropiophenone 97%, Sigma‐Aldrich). To generate different codes for each hydrogel microparticle, different masks (MicroTech, South Korea) with the capacity to generate 15 225 microparticles at once were used. All of the fabricated hydrogel particles were first collected in an ethyl alcohol (EtOH) solution. To prevent the photoinitiator residue of uncured resin from damaging cells, the washing steps with fresh EtOH solution were repeated two times, and then dried. Here, the photomask for making microparticles of a diameter 150 µm was used, but the fabricated microparticle slightly shrinks to 138 µm diameter after drying. However, all of the coding components shrunk at the same rate while maintaining their shape; thus, there was no problem in reading the code.
The authors declare no conflict of interest.