Biology subjects

Wilhelm, C.

Publications and source records attributed to Wilhelm, C..

5 recordsLinked to original sources

bioRxiv2023

Imaging membrane damage in ferroptosis and necrosis by wash-free fluorogenic chemical probes

Selectively labelling cells with damaged membranes is needed in contexts as simple as identifying dead cells in culture, or as complex as imaging membrane barrier functionality in vivo. The commonly used dyes are permanently coloured/fluorescent dyes that are simply excluded by intact membranes, but to achieve good image contrast therefore requires removing their extracellular signal by washing or background subtraction, which are not possible in vivo. Here, we develop fluorogenic probes which sensitively and selectively reveal damaged cells, without needing washing steps since their fluorescence turns on from near-zero background. From a set of novel fluorogenic probes impermeabilised by sulfonations along different vectors, we identify a specific disulfonated fluorogenic scaffold that enters cells only upon membrane damage, where it is enzymatically activated to mark them. The esterase probe iPS-FS2 is a reliable tool to reveal live cells that have been permeabilised by biological, biochemical, or physical membrane damage; and it can be used in multicolour microscopy. We confirm the modularity of this approach by also adapting it for redox-unmasked cell-excluded probes with improved hydrolytic stability. This scaffold-based design thus provides tools for wash-free in vivo imaging of membrane damage, which is relevant across many pathologies. The insightss gained from these probes should also be translatable to damage-targeted prodrugs, for selective therapy of membrane-compromised cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/543437v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1594016org.highwire.dtl.DTLVardef@7e7053org.highwire.dtl.DTLVardef@1008cb0org.highwire.dtl.DTLVardef@1148bd7_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Simple droplet microfluidics platform for drug screening on cancer spheroids

3D in vitro biological systems are progressively replacing 2D systems to increase the physiological relevance of cellular studies. Microfluidics-based approaches can be powerful tools towards such biomimetic systems, but often require high-end complicated and expensive processes and equipments for microfabrication. Herein, a drug screening platform is proposed, minimizing technicality and manufacturing steps. It provides an alternate way of spheroid generation in droplets in tubes. Droplets microfluidics then elicit multiple droplets merging events at programmable times, to submit sequentially the spheroids to chemotherapy and to reagents for cytotoxicity screening. After a comprehensive study of tumorigenesis within the droplets, the system is validated for drug screening (IC50) with chemotherapies in cancer cell lines as well as cells from patient-derived-xenografts (PDX). As compared to microtiter plates methods, our sytem reduces the initial amout of cell up to 10 times and opens new avenues towards primary tumors drug screening approaches.

cancer biology↗

bioRxiv2022

Magnetic bioprinting of stem-cell based tissues

An attractive approach in cell therapies and medically oriented nanotechnologies is to interface magnetic nanoparticles with cells. This will supply the cells with sufficient magnetization for theranostic applications and for external magnetic field manipulation. In tissue engineering, one challenge is to produce tissue analogues that are large, precisely organized, and responsive to stimuli, preferably without the need for an artificial supporting scaffold. One powerful tool for such biofabrication is certainly the bioprinting technology. In magnetic tissue engineering, it appears possible to use magnetic forces to manipulate cells, both individually and within aggregates, and thereby to produce three-dimensional artificial tissues with inherent capacities for further physical stimulation, a possibility that bioprinting does not offer yet. We here introduce the feasibility of using magnetic forces created by external (micro)magnets to form 3D tissue-like scaffold-free structures. Because stem cells are essential in tissue engineering, such magnetic technologies were developed with magnetized stem cells, and applied for instance to vascular or cartilage tissue engineering. One precondition to this approach, which lies in the magnetization of (stem) cells endowed through internalization of iron oxide magnetic nanoparticles, is to ensure the safety of magnetic nanoparticles with respect to cellular functions, which is initially discussed. Finally, we introduce a magnetic tissue stretcher which, in a single step, allows to create a tissue composed of any type of component cell, then to mature it, stimulate it by compression or stretching at any desired frequency, e.g. cyclically, opening new possibilities in the cardiac muscle tissue engineering field.

bioengineering↗

bioRxiv2022

Surface tension drives neuronal sorting in magnetically engineered brain-like tissue

Engineered 3D brain-like models have advanced the understanding of neurological mechanisms and disease, yet their mechanical signature, while fundamental for brain function, remains understudied. The surface tension for instance controls brain development and is a marker of cell-cell interactions. Here, we engineered 3D magnetic brain-like tissue spheroids composed of intermixed primary glial and neuronal cells at different ratios. Remarkably, the two cell types self-assemble into a functional tissue, with the sorting of the neuronal cells towards the periphery of the spheroids, whereas the glial cells constitute the core. The magnetic fingerprint of the spheroids then allows their deformation when placed under a magnetic field gradient, at a force equivalent to a 70 g increased gravity at the spheroid level. The tissue surface tension and elasticity can be directly inferred from the resulting deformation, revealing a transitional dependence on the glia/neuron ratio, with the surface tension of neuronal tissue being much lower. This provides the underlying mechanical explanation for the exclusion of the neurons towards the outer spheroid region, and depicts the glia/neuron organization as a surface tension-driven sophisticated mechanism that should in turn influence brain development and homeostasis.

bioengineering↗

bioRxiv2021

Multiparameters dependance of tissue shape maintenance in myoblasts multicellular aggregates: the role of intermediate filaments.

Liquid and elastic behavior of tissues drives their morphology and their response to the environment. They appear as the first insight on tissue mechanics. We explore the role of individual cell properties on spheroids of mouse muscle precursor cells by developing a fully automated surface tension and Youngs modulus measurement system. Flattening multicellular aggregates under magnetic constraint, we show that rigidity and surface tension act as highly sensitive macroscopic reporters closely related to microscopic local tension and effective adhesion. Shedding light on the major contributions of acto-myosin contractility, actin organization and intercellular adhesions, we reveal the role of desmin organization on the macroscopic mechanics of this tissue model.

biophysics↗