Nanoliter Centrifugal Liquid Dispenser Coupled with Superhydrophobic Microwell Array Chips for High-Throughput Cell Assays

An Automated High-Throughput Screening (HTS) Spotter for 3D Tumor Spheroid Formation

Three-dimensional (3D) culture platforms have been adopted in a high-throughput screening (HTS) system to mimic in vivo physiological microenvironments. The automated dispenser has been established commercially to enable spotting or distributing non-viscous or viscous biomaterials onto microplates. However, there are still challenges to the precise and accurate dispensation of cells embedded in hydrogels such as Alginate- and Matrigel-extracellular matrices. We developed and improved an automated contact-free dispensing machine, the ASFA SPOTTER (V5 and V6), which is compatible with 96- and 384-pillar/well plates and 330- and 532-micropillar/well chips for the support of 3D spheroid/organoid models using bioprinting techniques. This enables the distribution of non-viscous and viscous biosamples, including chemical drugs and cancer cells, for large-scale drug screening at high speed and small volumes (20 to 4000 nanoliters) with no damage to cells. The ASFA SPOTTER (V5 and V6) utilizes a contact-free method that minimizes cross-contamination for the dispensation of encapsulated tissue cells with highly viscous scaffolds (over 70%). In particular, the SPOTTER V6 does not require a washing process and offers the advantage of almost no dead volume (defined as additional required sample volume, including a pre-shot and flushing shot for dispensing). It can be successfully applied for the achievement of an organoid culture in automation, with rapid and easy operation, as well as miniaturization for high-throughput screening. In this study, we report the advantages of the ASFA SPOTTER, which distributes standard-sized cell spots with hydrogels onto a 384-pillar/well plate with a fast dispensing speed, small-scale volume, accuracy, and precision.

Artificial Intelligence-Controlled Microfluidic Device for Fluid Automation and Bubble Removal of Immunoassay Operated by a Smartphone

There have been tremendous innovations in microfluidic clinical diagnostics to facilitate novel point-of-care testing (POCT) over the past decades. However, the automatic operation of microfluidic devices that minimize user intervention still lacks reliability and repeatability because microfluidic errors such as bubbles and incomplete filling pose a major bottleneck in commercializing the microfluidic devices for clinical testing. In this work, for the first time, various states of microfluid were recognized to control immunodiagnostics by artificial intelligence (AI) technology. The developed AI-controlled microfluidic platform was operated via an Android smartphone, along with a low-cost polymer device to effectuate enzyme-linked immunosorbent assay (ELISA). To overcome the limited machine-learning capability of smartphones, the region-of-interest (ROI) cascading and conditional activation algorithms were utilized herein. The developed microfluidic chip was incorporated with a bubble trap to remove any bubbles detected by AI, which helps in preventing false signals during immunoassay, as well as controlling the reagents' movement with an on-chip micropump and valve. Subsequently, the developed immunosensing platform was tested for conducting real ELISA using a single microplate from the 96-well to detect the Human Cardiac Troponin I (cTnI) biomarker, with a detection limit as low as 0.98 pg/mL. As a result, the developed platform can be envisaged as an AI-based revolution in microfluidics for point-of-care clinical diagnosis.

Grouped-seq for integrated phenotypic and transcriptomic screening of patient-derived tumor organoids

Patient-derived tumor organoids (PDOs) have emerged as a reliable in vitro model for drug discovery. However, RNA sequencing-based analysis of PDOs treated with drugs has not been realized in a high-throughput format due to the limited quantity of organoids. Here, we translated a newly developed pooled RNA-seq methodology onto a superhydrophobic microwell array chip to realize an assay of genome-wide RNA output unified with phenotypic data (Grouped-seq). Over 10-fold reduction of sample and reagent consumption together with a new ligation-based barcode synthesis method lowers the cost to ∼$2 per RNA-seq sample. Patient-derived colorectal cancer (CRC) organoids with a number of 10 organoids per microwell were treated with four anti-CRC drugs across eight doses and analyzed by the Grouped-seq. Using a phenotype-assisted pathway enrichment analysis (PAPEA) method, the mechanism of actions of the drugs were correctly derived, illustrating the great potential of Grouped-seq for pharmacological screening with tumor organoids.

In Situ Vitrification of Lung Cancer Organoids on a Microwell Array

Three-dimensional cultured patient-derived cancer organoids (PDOs) represent a powerful tool for anti-cancer drug development due to their similarity to the in vivo tumor tissues. However, the culture and manipulation of PDOs is more difficult than 2D cultured cell lines due to the presence of the culture matrix and the 3D feature of the organoids. In our other study, we established a method for lung cancer organoid (LCO)-based drug sensitivity tests on the superhydrophobic microwell array chip (SMAR-chip). Here, we describe a novel in situ cryopreservation technology on the SMAR-chip to preserve the viability of the organoids for future drug sensitivity tests. We compared two cryopreservation approaches (slow freezing and vitrification) and demonstrated that vitrification performed better at preserving the viability of LCOs. Next, we developed a simple procedure for in situ cryopreservation and thawing of the LCOs on the SMAR-chip. We proved that the on-chip cryopreserved organoids can be recovered successfully and, more importantly, showing similar responses to anti-cancer drugs as the unfrozen controls. This in situ vitrification technology eliminated the harvesting and centrifugation steps in conventional cryopreservation, making the whole freeze–thaw process easier to perform and the preserved LCOs ready to be used for the subsequent drug sensitivity test.

Nanoliter-scale liquid metering and droplet generation based on a capillary array for high throughput screening

Herein, we developed a simple approach for quantitative metering of nanoliter-scale liquids in parallel based on a capillary array and applied it in high throughput screening protein crystallization conditions. The quantitative metering of liquids was achieved by using capillary force to spontaneously introduce the liquids into short capillaries with fixed length and inner diameter, and the nanoliter-scale droplets were generated by using a pneumatic pump to deliver liquids out from the capillary channels. We adopted measures of sharpening the capillary tips and performing a hydrophobic treatment on the tip surface to significantly reduce the capillary residues during the liquid aspirating and dispensing process, and thus improved the precision to 0.2%-3.5% relative standard deviations (RSD, n = 3) in metering droplets in the range of 280 pL-90 nL. We evaluated the performance of the system in metering liquids of different surface tensions and viscosity. On the basis of this approach, we built a capillary array system with 12 capillaries, by which parallel generation of 12 nL droplets of 12 samples could be achieved in 40 s with a relative standard deviation (RSD) of 1.2%. We applied the system in the screening of lysozyme crystallization conditions of 48 precipitants with 7.5 nL precipitant and 7.5 nL protein solutions in each crystallization droplet reactor, to demonstrate its potentials in large-scale high-throughput screening and analysis with different samples.

Centrifugal Generation of Droplet-Based 3D Cell Cultures

Quickly and easily producing uniform populations of microsphere-based 3D cell cultures using droplet-based templating methods has the potential to enable widespread use of such platforms in drug discovery or cancer research. Here, we advance the design of centrifuge-based droplet generation devices, describe the use of this platform for droplet generation with controlled cell occupancy, and demonstrate weeklong culture duration. Using simple-to-construct devices and easily implemented protocols, the initial concentration of encapsulated cells is adjustable up to hundreds of cells per microsphere. This work demonstrates the first instance of using centrifugal droplet-generating devices to produce large numbers of cell-encapsulating microspheres. Applications of this versatile methodology include the rapid formation of templated 3D cell culture populations suitable for suspension culture or large batch bioreactor studies that require uniform populations.

High-Throughput Platform for Efficient Chemical Transfection, Virus Packaging, and Transduction

Intracellular gene delivery is normally required to study gene functions. A versatile platform able to perform both chemical transfection and viral transduction to achieve efficient gene modification in most cell types is needed. Here we demonstrated that high throughput chemical transfection, virus packaging, and transduction can be conducted efficiently on our previously developed superhydrophobic microwell array chip (SMAR-chip). A total of 169 chemical transfections were successfully performed on the chip in physically separated microwells through a few simple steps, contributing to the convenience of DNA delivery and media change on the SMAR-chip. Efficiencies comparable to the traditional transfection in multi-well plates (~65%) were achieved while the manual operations were largely reduced. Two transfection procedures, the dry method amenable for the long term storage of the transfection material and the wet method for higher efficiencies were developed. Multiple transfections in a scheduled manner were performed to further increase the transfection efficiencies or deliver multiple genes at different time points. In addition, high throughput virus packaging integrated with target cell transduction were also proved which resulted in a transgene expression efficiency of >70% in NIH 3T3 cells. In summary, the SMAR-chip based high throughput gene delivery is efficient and versatile, which can be used for large scale genetic modifications in a variety of cell types.

One-Step Preparation of Durable Super-Hydrophobic MSR/SiO₂ Coatings by Suspension Air Spraying

In this study, we develop a facial one-step approach to prepare durable super-hydrophobic coatings on glass surfaces. The hydrophobic characteristics, corrosive liquid resistance, and mechanical durability of the super-hydrophobic surface are presented. The as-prepared super-hydrophobic surface exhibits a water contact angle (WCA) of 157.2° and contact angle hysteresis of 2.3°. Mico/nano hierarchical structures and elements of silicon and fluorine is observed on super-hydrophobic surfaces. The adhesion strength and hardness of the surface are determined to be 1st level and 4H, respectively. The coating is, thus, capable of maintaining super-hydrophobic state after sand grinding with a load of 200 g and wear distances of 700 mm. The rough surface retained after severe mechanical abrasion observed by atomic force microscope (AFM) microscopically proves the durable origin of the super-hydrophobic coating. Results demonstrate the feasibility of production of the durable super-hydrophobic coating via enhancing its adhesion strength and surface hardness.