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In spite of tremendous advances made in the comprehension of mechanotransduction, implementation of mechanobiology assays remains challenging for the broad community of cell biologists. Hydrogel substrates with tunable stiffness are essential tool in mechanobiology, allowing to investigate the effects of mechanical signals on cell behavior. A bottleneck that slows down the popularization of hydrogel formulations for mechanobiology is the assessment of their stiffness, typically requiring expensive and sophisticated methodologies in the domain of material science. Here we overcome such barriers offering the reader protocols to set-up and interpret two straightforward, low cost and high-throughput tools to measure hydrogel stiffness: static macroindentation and micropipette aspiration. We advanced on how to build up these tools and on the underlying theoretical modeling. Specifically, we validated our tools by comparing them with leading techniques used for measuring hydrogel stiffness (atomic force microscopy, uniaxial compression and rheometric analysis) with consistent results on PAA hydrogels or their modification. In so doing, we also took advantage of YAP/TAZ nuclear localization as biologically validated and sensitive readers of mechanosensing, all in all presenting a suite of biologically and theoretically proven protocols to be implemented in most biological laboratories to approach mechanobiology.

We report a rapid and cost-effective system to analyze morphological properties and 3D alignment positions of human white blood cell in a viscoelastic induced microfluidic flow. Measurements have been performed in physiological conditions using light scattering for the investigation of the individu-al cell properties and digital holography for the accurate tracking of the cell position in 3D. Our re-sults confirm the possibility to obtain sub-micrometric individual cell details as dimension and refrac-tive index, together with detailed cell location in continuous measurement flows inside of a rectangular shaped channel.

We show that seeing an erythrocyte-ensemble as microlens-array, detection of abnormal cells can be made rapidly and efficiently without recurring to subjective shape analysis of image by the doctor or by sophisticated image processing tools, but rather by exploiting their abnormal shape alterations affecting the lens-focusing properties. Demonstration of how aberrations affect the focusing properties of the RBCs is given by Harthman-Shark approach and Zernike polynomial-fitting, as occurs for wavefront aberration correction in adaptive modern astronomic telescopes. The results show how the concept of biological lens could be addressed for revolutionary integration between photonics and biology and that a fast blood pre-screening can be performed by the proposed approach.

Angiogenin (ANG) promotes cell growth and survival. Under growth conditions, ANG undergoes nuclear translocation and accumulates in the nucleolus where it stimulates rRNA transcription. When cells are stressed, ANG mediates the production of tRNA-derived stress-induced small RNA (tiRNA), which reprograms protein translation into a survival mechanism. The ribonucleolytic activity of ANG is essential for both processes but how this activity is regulated is unknown. We report here that ribonuclease/angiogenin inhibitor 1 (RNH1) controls both the localization and activity of ANG. Under growth conditions, ANG is located in the nucleus and is not associated with RNH1 so that the ribonucleolytic activity is retained to ensure rRNA transcription. Cytoplasmic ANG is associated with and inhibited by RNH1 so that random cleavage of cellular RNA is prevented. Under stress conditions, ANG is localized to the cytoplasm and is concentrated in stress granules where it is not associated with RNH1 and thus remains enzymatically active for tiRNA production. By contrast, nuclear ANG is associated with RNH1 in stressed cells to ensure that the enzymatic activity is inhibited and no unnecessary rRNA is produced to save anabolic energy. Knockdown of RNH1 abolished stress-induced relocalization of ANG and decreased cell growth and survival.

Introduction: An attractive alternative to synthetic scaffolds is represented by reconstituted collagen gels populated by cells. Such devices possess noteworthy advantages since the collagen is one of the most important mammalian protein and the collagen gel itself constitutes an environment to host cells which is closer to the native one. Cell populated collagen gels have been successfully employed in tissue engineering applications, as well as model to study cell-collagen interaction in 3D constructs. However, in order to improve the physical/biological performance of the gels and to better understand cell/collagen interactions, quantitative relationships must be developed between the cell constructs and their mechanical properties. Aim of this work is to develop an experimental model to evaluate how cell reconfigure collagen gel and modify its mechanical behaviour.

The non-specific adhesion of spherical micro- and nano-particles to a cell substrate is investigated in a parallel plate flow chamber. Differently from prior in-vitro analyses, the total volume of the particles injected into the flow chamber is kept fixed whilst the particle diameter is changed in the range 0.5-10 microm. It is shown that: (i) the absolute number of particles adherent to the cell layer per unit surface decreases with the size of the particle as d(-1.7); (ii) the volume of the particles adherent per unit surface increases with the size of the particles as d(+1.3). From these results and considering solely non-specific particles, the following hypothesis are generated (i) use the smallest possible particles in biomedical imaging and (ii) use the largest possible particles in drug delivery.

The extracellular matrix (ECM) may contribute to the drug resistance of a solid tumor by preventing the penetration of therapeutic agents. We measured differences in interstitial resistance to macromolecule (IgG) motion in four tumor types and found an unexpected correspondence between transport resistance and the mechanical stiffness. The interstitial diffusion coefficient of IgG was measured in situ by fluorescence redistribution after photobleaching. Tissue elastic modulus and hydraulic conductivity were measured by confined compression of excised tissue. In apparent contradiction to an existing paradigm, these functional properties are correlated with total tissue content of collagen, not glycosaminoglycan. An extended collagen network was observed in the more penetration-resistant tumors. Collagenase treatment of the more penetration-resistant tumors significantly increased the IgG interstitial diffusion rate. We conclude that collagen influences the tissue resistance to macromolecule transport, possibly by binding and stabilizing the glycosaminoglycan component of the ECM. These findings suggest a new method to screen tumors for potential resistance to macromolecule-based therapy. Moreover, collagen and collagen-proteoglycan bonds are identified as potential targets of treatment to improve macromolecule delivery.

In this work, we developed an innovative gut-liver-on-chip system useful to predict oral drug administration and first pass metabolism. The two main organs involved in the first pass metabolism are the liver and the intestine. First-pass effects consist mainly in the reduction of bioavailability of drugs and xenobiotics. The prediction of this mechanism is important both for the development of new substances, but also for toxicity testing. For this purpose, we designed a microfluidic device which interconnect 3D human intestinal equivalent (3D-HIE) and HepG2-microtissues, recapitulating the intestinal and hepatic firstpass effect mechanism of ethanol. 3D-HIE were obtained by bottom up approach, using intestinal microtissues moulded into a maturation chamber and HepG2-μTPs were obtained by dynamic cell seeding of Hepg2 and gelatin porous microsphere in a spinner flask bioreactor.