Biology

A new micropatterning method of soft substrates reveals that different tumorigenic signals can promote or reduce cell contraction levels

Abstract

In tissues, cell microenvironment geometry and mechanics strongly impact on cell physiology. Surface micropatterning allows the control of geometry while deformable substrates of tunable stiffness are well suited for the control of the mechanics. We developed a new method to micropattern extracellular matrix proteins on poly-acrylamide gels in order to simultaneously control cell geometry and mechanics. Microenvironment geometry and mechanics impinge on cell functions by regulating the development of intra-cellular forces. We measured these forces in micropatterned cells. Micropattern geometry was streamlined to orient forces and place cells in comparable conditions. Thereby force measurement method could be simplified and applied to large-scale experiment on chip. We applied this method to mammary epithelial cells with traction force measurements in various conditions to mimic tumoral transformation. We found that, contrary to the current view, all transformation phenotypes were not always associated to an increased level of cell contractility.

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A new micropatterning method of soft substrates reveals that different tumorigenic signals can promote or reduce cell contraction levels

Microcontact printing for co-patterning cells and viruses for spatially controlled substrate-mediated gene delivery

Abstract

Spatial organization of gene expression is a crucial element in the development of complex native tissues, and the capacity to achieve spatially controlled gene expression profiles in a tissue engineering construct is still a considerable challenge. To give tissue engineers the ability to design specific, spatially organized gene expression profiles in an engineered construct, we have investigated the use of microcontact printing to pattern recombinant adeno-associated virus (AAV) vectors on a two dimensional surface as a first proof-of-concept study. AAV is a highly safe, versatile, stable, and easy-to-use gene delivery vector, making it an ideal choice for this application. We tested the suitability of four chemical surfaces (–CH3, –COOH, –NH2, and –OH) to mediate localized substrate-mediated gene delivery. First, polydimethylsiloxane stamps were used to create microscale patterns of various self-assembled monolayers on gold-coated glass substrates. Next, AAV particles carrying genes of interest and human fibronectin (HFN) were immobilized on the patterned substrates, creating a spatially organized arrangement of gene delivery vectors. Immunostaining studies reveal that –CH3 and –NH2 surfaces result in the most successful adsorption of both AAV and HFN. Lastly, HeLa cells were used to analyze viral transduction and spatial localization of gene expression. We find that –CH3, –COOH, and –NH2 surfaces support complete uniform cell coverage with high gene expression. Notably, we observe a synergistic effect between HFN and AAV for substrate-mediated gene delivery. Our flexible platform should allow for the specific patterning of various gene and shRNA cassettes, resulting in spatially defined gene expression profiles that may enable the generation of highly functional tissue.

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Microcontact printing for co-patterning cells and viruses for spatially controlled substrate-mediated gene delivery

Improving Protein Transfer Efficiency and Selectivity in Affinity Contact Printing by Using UV-Modified Surfaces

Abstract

Affinity contact printing (αCP) is a technique that allows the selective capture of a target protein from solutions to a polymeric stamp decorated with an antibody, and then the target protein is printed onto a solid surface. The success of αCP critically relies on the precise control of protein−surface interactions. Here, we report a study on the effect of UV on the protein−surface interactions between protein and polydimethylsiloxane stamps and between protein and glass slides decorated with N,N-dimethyl-n-octadecyl-3-aminopropyltrimethoxysilyl chloride (DMOAP). Our results show that UV-modified surfaces can be used to improve the transfer efficiency and selectivity of proteins during αCP. For example, the protein transfer efficiency of human IgG onto a DMOAP-coated slide increases from 7.2% to 45.1% after the UV treatment. On the basis of these results, UV-modified surfaces were employed to develop a αCP system for protein detection. The detection limit of anti-IgG in this system is around 10 ng/mL, and the dynamic range is 4 orders of magnitude.

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Improving Protein Transfer Efficiency and Selectivity in Affinity Contact Printing by Using UV-Modified Surfaces

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