Double-exclusive liquid repellency (double-ELR): an enabling technology for rare phenotype analysis

Abstract

Double-exclusive liquid repellency (double-ELR) is an extreme wettability phenomenon in which adjacent regions selectively and completely repel immiscible liquids with different surface chemistries on a non-textured substrate (i.e., a substrate in absence of micro/nano-structures). Under double-ELR conditions, each liquid exhibits no physical contact (contact angle of 180°) with its non-preferred surface chemistry, thus enabling complete partitioning of adjacent fluidic volumes (e.g., between water and oil). This enables a new type of cell culture-based assay, where cell loss from common failure modes (e.g., biofouling from inadvertent cell adhesion, detrimental moisture loss/gain, and liquid handling dead volumes) is significantly mitigated. Importantly, the principles of double-ELR were leveraged to achieve underoil sweep patterning, a no-loss, robust and high-throughput distribution of sub-microliter volumes of aqueous media (and cells). In addition to high-efficiency distribution via sweep patterning, double-ELR can be used to construct "modular" (i.e., easily implemented and/or linked together with spatial and temporal control) higher-order architectures for in vitro imitation of physiologically relevant microenvironments that are of particular interest within the cell assay community, including multi-phenotype cultures with excellent spatial and temporal control, three-dimensional layered multi-phenotype cultures, cultures with selective mechanical cues of extracellular matrix (i.e., collagen fiber alignment), and spheroid cultures. Together, these features of double-ELR uniquely facilitate culture and high content analysis of limited cellular samples (e.g., a few hundred to a few thousand cells).

Under oil open-channel microfluidics empowered by exclusive liquid repellency

“…5 and Materials and Methods). Earlier, a reconfigurable liquid bridge (i.e., a droplet of fluid connecting two separated spots) enabled by double ELR was introduced for spatiotemporal control of cell coculture under oil (19). By simply adding volume to or removing volume from the liquid bridge, connection or disconnection can be achieved reversibly.…”

“…The same media (unless otherwise specified) was used in preparation of all of the solution and suspension used in this study. An antistatic gun (Zerostat 3 Milty, EMS 60610) was used to generate perturbation during sweep and to facilitate the displacement of oil by media (19).…”

“…Under oil sweep is accomplished by simply dragging an aqueous fluid (e.g., cell culture media) across the patterned surface under oil, resulting in a specific volume of media (with or without cells) being spontaneously dispensed onto the patterned areas (i.e., microchannels or spots) and leaving the background clean with minimal sample loss and device fouling ( Fig. 1A, III, and movie S1) (19). In this study, we exploit double ELR and under oil sweep to prepare open microchannels under oil with high lateral resolution (~30 m in both width and spacing), low profiles (~1 m in height) capable of selective cell trapping, enhanced upper limit of flow rate, steady flow with passive pumping, and fully reversible antibiofouling fluidic valves.…”

Prostate cancer research: The next generation; report from the 2019 Coffey‐Holden Prostate Cancer Academy Meeting

“…Additional stacking with patient-matched M2 macrophages inhibited the migration of T cells, indicating the potential for functional assessment of a patient's tumor-microenvironment interaction (Lang et al, unpublished). [140][141][142] Pushing 3D culture systems to the next level, Lang et al have now begun to utilize exclusive and/or finite liquid repellency (ELR and FLR, respectively) [143][144][145] platforms to investigate tumor cell interactions with immune cells at the single-cell level. ELR/FLR enables the culture of single cells in microbubbles submerged in oil.…”

“…145 Further, the application of FLR allowed for successful single-cell culturing of human C4-2B prostate cancer cells, which demonstrated contrasting abilities of individual cells to proliferate, indicated by differential gene expression profiles. 144,145 ELR-based coculture experiments of human tumor-associated neutrophils with C4-2B tumoroids demonstrated heterogeneous interactions between tumoroid and neutrophil populations, including induction of tumor invasion versus apoptosis. 144,145 These studies and technologies will improve our ability to observe and understand exact tumor-microenvironment interactions and tumor potential for metastatic progression and/or response to therapy.…”