# Anti-Cancer Drug Screening with Microfluidic Technology
## 2 Monodrug Screening on a Microscale Sample
### Three-Dimensional Cell Cultures  
[PERSON] et al. developed a droplet-based microfluidic system for anti-cancer drug screening on alginate beads with entrapped breast tumor cells [42]. Multicellular aggregates create a three-dimensional environment to encapsulate cells for on-chip incubation. The authors tested the drug response of spheroids originated from LCC6/Her-2 breast tumor cells at four concentrations of doxorubicin. Utilizing this platform with the precise positioning of beads, they showed that multicellular resistance is higher than standard monolayer culture. [PERSON] et al. reported a 3D microenvironment with microcirculation consisting of three PDMS layers to monitor the dynamic responses of potential or clinical anti-cancer drugs (Tarceva, Staurosporine, and TNF-\(\alpha\) with cycloheximide) [43]. The bottom layer has microchambers with cancer cells (human ductal breast epithelial tumor cell line (T47D), human non-small cell lung cancer cell line (PC9), and adult human dermal blood microvascular endothelial cells (HMVEC)) encapsulated in a hydrogel, the middle layer is a permeable membrane, and the upper layer has microchannels with seeded endothelial cells. The advantage of this platform over previous microfluidics without a 3D extracellular matrix is that the cells are not in direct contact with the flow, and diffusion is the primary transport mechanism. [PERSON] et al. manufactured a 3D cell culture micropillar/microwell chip made of poly (styrene-co-maleic anhydride) which is ideally suited for drug testing on hydrogels of primary cancer cells [34]. The therapeutic efficacy of 24 anti-cancer drugs on a U251 brain cancer cell line and three primary brain cancer cells was measured and well correlated with previous in vivo results of a mouse xenograft model with the three primary brain cancer cells. [PERSON] et al. developed a microfluidic chip to form homogeneous spheroids from either cell lines or human primary cells by a sedimentation trap in the microwells [44]. Chemosensitivity tests with cisplatin were performed on primary spheroids cultured as monoculture with epithelial cells and co-culture using epithelial cells and pericytes. The comparison of chemoresistance showed that pericytes protect lung cancer epithelial cells against the chemotherapeutical drug. Thus, this microfluidic device can be used for chemosensitivity tests for personalized medicine. [PERSON] et al. developed a 3D cell culture microwell chip for anti-cancer drug screening [45]. They used several human cancer cell lines (colon cancer cells HCT116, breast cancer cells T47D, and hepatocellular carcinoma cells HepG2) to form multicellular tumor spheroids for mimicking the ex vivo tumor micro-tissue model for drug screening research. After spheroids formation, two anti-cancer drugs (doxorubicin and paclitaxel) with desired gradient concentrations were injected into the microchannels. They have not reported the specifications of their applied concentration gradient generation. However, their results show that only a three-drug dosage was tested. [PERSON] et al. developed pneumatic microfluidics for high-throughput anti-cancer drug screening [46]. The advantage of the recyclable microfluidics over a conventional 3D tumor culture system is its cell trapping and its production of similarly sized 3D tumor spheroids from human glioma U251 cells. This single-cell array provides the analysis of different response dynamics and apoptotic signals during chemotherapy with two clinically used anti-cancer drugs (vincristine and bleomycin). [PERSON] et al. described a paper-based microfluidic with Hela cells, a human epithelial cell line derived from cervical carcinoma cultured with collagen hydrogel as a 3D scaffold and incubated in the device reservoirs [47]. They studied the cell response to a discrete concentration gradient of doxorubicin as a model anti-cancer drug.