Microfluidic gradient generator for drug testing on a colorectal tumor-on-a-chip disease model

Statement of Purpose: Colorectal cancer is the third most common cancer and its incidence increases with ageing. Understanding the mechanisms of tumour growth rely in further advances to unveil cancer-causing agents, drug screening and in the development of personalized therapies. Standard 2D in vitro models and in vivo animal models have undoubtedly contributed to the development of anti-cancer drug candidates. Yet their translation into successful clinical trials is critically low, which reinforces the need of a deeper understanding of tumorigenesis (1). Therefore, 3D models integrating tissue engineering (TE) strategies with microfluidic technology have sparked the expectation on physiologically relevant microfluidic in vitro models (2). The aim of this work is to establish a 3D microfluidic model that enables the reconstitution of physiological functions of microvascular tissue that emulates the human colorectal tumor microenvironment. This model will be established via a microfluidic device with an encapsulating hydrogel compartment comprising a co-culture system of HCT-116 colorectal cancer cells and human intestinal microvascular endothelial cells

A One‐Step Biofunctionalization Strategy of Electrospun Scaffolds Enables Spatially Selective Presentation of Biological Cues

To recapitulate the heterogeneous complexity of tissues in the human body with synthetic mimics of the extracellular matrix (ECM), it is important to develop methods that can easily allow the selective functionalization of defined spatial domains. Here, a facile method is introduced to functionalize microfibrillar meshes with different reactive groups able to bind biological moieties in a one‐step reaction. The resulting scaffolds prove to selectively support a differential neurite growth after being seeded with dorsal root ganglia. Considering the general principles behind the method developed, this is a promising strategy to realize enhanced biomimicry of native ECM for different regenerative medicine applications

Microfluidic collagen patterning for tendon regeneration

We present a microfluidic approach to align collagen fibers for tendon regeneration. Collagen fibers with a specific orientation were patterned in a microfluidic channel by introducing collagen solution through integrated microstructures. The fluid flow in the pillar array was evaluated by computational modeling, and the aligned collagen fibers were analyzed quantitatively. Then, primary rat tenocytes were cultured on oriented and not-oriented collagen micropatterns, and their phenotypical commitment was evaluated. We believe that such a platform would be useful to replicate in vivo microenvironment for the study of regenerative processes

From fiber curls to mesh waves:a platform for the fabrication of hierarchically structured nanofibers mimicking natural tissue formation

\u3cp\u3eBioinstructive scaffolds for regenerative medicine are characterized by intrinsic properties capable of directing cell response and promoting wound healing. The design of such scaffolds requires the incorporation of well-defined physical properties that mimic the native extracellular matrix (ECM). Here, inspired by epithelial tissue morphogenesis, we present a novel approach to code nanofiber materials with controlled hierarchical wavy structures resembling the configurations of native EMC fibers through using thermally shrinking materials as substrates onto which the fibers are deposited. This approach could serve as a platform for fabricating functional scaffolds mimicking various tissues such as trachea, iris, artery wall and ciliary body. Modeling affirms that the mechanical properties of the fabricated wavy fibers could be regulated through varying their wavy patterns. The nanofibrous scaffolds coded with wavy patterns show an enhanced cellular infiltration. In addition, we further investigated whether the wavy patterns could regulate transforming growth factor-beta (TGF-β) production, a key signalling pathway involved in connective tissue development. Our results demonstrated that nanofibrous scaffolds coded with wavy patterns could induce TGF-β expression without the addition of a soluble growth factor. Our new approach could open up new avenues for fabricating bioinstructive scaffolds for regenerative medicine.\u3c/p\u3

PSC-derived intestinal organoids with apical-out orientation as a tool to study nutrient uptake, drug absorption and metabolism

Intestinal organoids recapitulate many features of the in vivo gastrointestinal tract and have revolutionized in vitro studies of intestinal function and disease. However, the restricted accessibility of the apical surface of the organoids facing the central lumen (apical-in) limits studies related to nutrient uptake and drug absorption and metabolism. Here, we demonstrate that pluripotent stem cell (PSC)-derived intestinal organoids with reversed epithelial polarity (apical-out) can successfully recapitulate tissue-specific functions. In particular, these apical-out organoids show strong epithelial barrier formation with all the major junctional complexes, nutrient transport and active lipid metabolism. Furthermore, the organoids express drug-metabolizing enzymes and relevant apical and basolateral transporters. The scalable and robust generation of functional, apical-out intestinal organoids lays the foundation for a completely new range of organoid-based high-throughput/high-content in vitro applications in the fields of nutrition, metabolism and drug discovery

The Galapagos Chip Platform for High-Throughput Screening of Cell Adhesive Chemical Micropatterns

In vivo cells reside in a complex extracellular matrix (ECM) that presents spatially distributed biochemical and ‑physical cues at the nano- to micrometer scales. Chemical micropatterning is successfully used to generate adhesive islands to control where and how cells attach and restore cues of the ECM in vitro. Although chemical micropatterning has become a powerful tool to study cell–material interactions, only a fraction of the possible micropattern designs was covered so far, leaving many other possible designs still unexplored. Here, a high-throughput screening platform called “Galapagos chip” is developed. It contains a library of 2176 distinct subcellular chemical patterns created using mathematical algorithms and a straightforward UV-induced two-step surface modification. This approach enables the immobilization of ligands in geometrically defined regions onto cell culture substrates. To validate the system, binary RGD/polyethylene glycol patterns are prepared on which human mesenchymal stem cells are cultured, and the authors observe how different patterns affect cell and organelle morphology. As proof of concept, the cells are stained for the mechanosensitive YAP protein, and, using a machine-learning algorithm, it is demonstrated that cell shape and YAP nuclear translocation correlate. It is concluded that the Galapagos chip is a versatile platform to screen geometrical aspects of cell–ECM interaction

Fabrication of cell container arrays with overlaid surface topographies

This paper presents cell culture substrates in the form of microcontainer arrays with overlaid surface topographies, and a technology for their fabrication. The new fabrication technology is based on microscale thermoforming of thin polymer films whose surfaces are topographically prepatterned on a micro- or nanoscale. For microthermoforming, we apply a new process on the basis of temporary back moulding of polymer films and use the novel concept of a perforated-sheet-like mould. Thermal micro- or nanoimprinting is applied for prepatterning. The novel cell container arrays are fabricated from polylactic acid (PLA) films. The thin-walled microcontainer structures have the shape of a spherical calotte merging into a hexagonal shape at their upper circumferential edges. In the arrays, the cell containers are arranged densely packed in honeycomb fashion. The inner surfaces of the highly curved container walls are provided with various topographical micro- and nanopatterns. For a first validation of the microcontainer arrays as in vitro cell culture substrates, C2C12 mouse premyoblasts are cultured in containers with microgrooved surfaces and shown to align along the grooves in the three-dimensional film substrates. In future stem-cell-biological and tissue engineering applications, microcontainers fabricated using the proposed technology may act as geometrically defined artificial microenvironments or niches

Integrated 3D Acid Fracturing Model for Carbonate Reservoir Stimulation

Acid fracturing is one of the stimulation methods used in carbonate formations and has been proved effective and economical. Because of the stochastic nature of acidizing in carbonate formation, designing and optimizing acid fracture treatment today still remain challenging. In the past, a simple acid fracture conductivity correlation was usually considered sufficient to estimate the overall average fracture conductivity in the formation, leading to the computation of the productivity index for fractured well performance. However, the nature of heterogeneity could not be included in the modeling. Understanding the important role of heterogeneity to stimulation performance becomes a crucial step in design and optimization of acid fracture jobs. In order to study the effect of this stochastic nature on acid fracturing, a fully 3D acid reaction model was developed based on the geostatistical parameters of the formation. It is possible to describe local conductivity distribution related to acid transport and reaction process. In this study, we have developed a new interactive workflow allowing the model of the fracture propagation process, the acid etching process and the well production interactively. This thesis presents the novel approach in integrating fracture propagation, acid transport and dissolution, and well performance models in a seamless fashion for acid fracturing design. In this new approach, the fracture geometry data of a hydraulic fracture is first obtained from commercial models of hydraulic fracture propagation, and then the 3D acid fracture model simulates acid etching and transport from the fracture propagation model using the width distribution as the initial condition. We then calculate the fracture conductivity distribution along the created fracture considering the geostatistical parameters such as permeability correlation length and standard deviation in permeability of the formation. The final step of the approach is to predict well performance after stimulation with a reservoir flow simulator. The significant improvements of the new approach are two folds: (1) capturing the geostatistical effect of the formation; and (2) modeling the acid etching and transport more accurately. The thesis explains the methodology and illustrates the application of the approach with examples. The results from this study show that the new model can successfully design and optimize acid fracturing treatments