Chronic kidney disease (CKD) is characterized by a gradual decline in renal function that progresses toward end-stage renal disease (ESRD). Podocytes are highly specialized glomerular epithelial cells, which form with the glomerular basement membrane (GBM) and capillary endothelium, the glomerular filtration barrier (GFB). GBM is an extracellular matrix (ECM) that acts as a mechanical support and provides biophysical signals that control normal podocytes behavior in the process of glomerular filtration. Thus the modulus of elasticity E or stiffness of “ECM” represents an essential characteristic that controls podocyte functions. The biophysical properties of hydrolyzed Polyacrylamide (PAAm) gels resemble to in vivo ECM and thus provide an opportunity to be applied as ECM-like membranes to study cellular behaviors. Therefore, hydrolyzed PAAm hydrogels were investigated for their potential use as new ECM-like constructs to engineer a basement membrane that form with cultured human podocytes a functional glomerular-like filtration barrier. Such ECM-like polyacrylamide hydrogel construct will provide the unique opportunity of understanding in an in vivo-like setting podocyte cells biological responses by controlling the physical properties of the PAAm membranes. In this work, several PAAm hydrogel layers were prepared by changing the crosslinker concentration. The macromolecular microstructure and stiffness were evaluated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) techniques respectively. Accordingly, the mechanical properties and the polymeric network porosity can be effectively controlled by modulating the crosslinker concentration as well as the swelling degree. Moreover, modulating gel stiffness significantly influenced podocyte behavior including morphology, actin cytoskeleton reorganization. In conclusion, podocytes response to the variation of the mechanical properties of the membranes correlated with the hydrogels stiffness. This work addresses the complexity of podocytes behavior which will further enhance our knowledge to develop a kidney-on-chip model much needed to study kidney function in both health and disease states.

Microgels specific structural and functional features are attracting high research interest in several appli- cations such as bioactives and drug delivery or functional food ingredients. Whey protein microgels (WPM) are obtained by heat treatment of whey protein isolate (WPI) in order to promote intramolecular cross-linking. In the present work, atomic force microscopy (AFM) was used in contact mode and in liquid to investigate WPM particles topography and mechanical properties at the nanoscale at native pH (6.5) and acid pH (5.5 and 3.0). Prior to AFM, WPM particles were captured on a gold substrate via low energy interactions by means of specific monoclonal antibodies. AFM images clearly showed an increase in the size of WPM particles induced by pH decrease. AFM in force spectroscopy mode was employed to monitor the elasticity of WPMs. The obtained effective Young’s modulus data showed a significant increase in stiffness at pH 5.5 and pH 3.0, over 15-fold compared to native pH. These findings indicate that the mechanical profile of the WPM network varied with the pH decrease. The WPM topographic and nanome- chanical changes induced by acidification were most likely due to substantial changes in the shape and inner structure of WPM particles. Our results suggest that internally cross-linked structures, modified by acidification could display interesting functional properties when used as a food ingredient.

Chronic kidney disease is characterized by a gradual decline in renal function that progresses toward end-stage renal disease.Podocytes are highly specialized glomerular epithelial cells which form with the glomerular basement membrane (GBM) and capillaryendothelium the glomerular filtration barrier. GBM is an extracellular matrix (ECM) that acts as a mechanical support and providesbiophysical signals that control normal podocytes behavior in the process of glomerular filtration. Thus, the ECM stiffness represents anessential characteristic that controls podocyte function. Hydrolyzed Polyacrylamide (PAAm) hydrogels are smart polyelectrolytes materials.Their biophysical properties can be tuned as desired to mimic the in natural ECM. Therefore, these hydrogels are investigated as new ECM-like constructs to engineer a podocyte-like basement membrane that forms with cultured human podocytes a functional glomerular-like filtration barrier. Such ECM-like PAAm hydrogel construct will provide unique opportunity to reveal podocyte cell biological responses in an in vivo-like setting by controlling the physical properties of the PAAm membranes. In this work, Hydrolyzed PAAm scaffolds having different stiffness ranging between 0.6− 44 kPa are prepared. The correlation between the hydrogel structural and mechanical properties and Podocytes morphology, elasticity, cytoskeleton reorganization, and podocin expression is evaluated. Results show that hydrolyzed PAAm hydrogels promote good cell adhesion and growth and are suitable materials for the development of future 3D smart scaffolds. In addition, the hydrogel properties can be easily modulated over a wide physiological range by controlling the cross-linker concentration. Finally, tuning the hydrogel properties is an effective strategy to control the cells function. This work addressed the complexity of podocytes behavior which will further enhance our knowledge to develop a kidney-on-chip model much needed in kidney function studies on both healthy and diseased states.

Extensive use of porous silicon (PSi) for tissue engineering is due to its convenient properties as it is both non-toxic and bioresorbable. Moreover, PSi surface modification is an important step to enhance cell adhesion and proliferation. In this work, a combination of optical and electrochemical studies is performed to elaborate a suitable PSi multilayer substrate for cell culture. For this study, we modified PSi surface by silanization and antibody grafting (APTES-anti STRO1), the 12-mer specific peptide to silicon p+type coating and the peptide modified with the antibody recognition sequence. Electrochemical characterization of PSi multilayers is performed to investigate its electrical behavior, determine the optimal measuring conditions and reveal the most stable PSi surfaces. Then, the behavior of dental pulp stem cells (DPSC) was investigated on various modified PSi surfaces. An electrochemical method was applied for the first time monitoring the electrical behavior of stem cell adhesion. The cells electrochemical behavior depends on the nature of the surface coating and the peptide-anti STRO1 improved adhesion and cell spreading onto the PSi surface compared to bare surface and the one coated with the peptide. Fluorescent microscopy revealed that all surface modi cation methods enhance cell adhesion compared to the bare PSi surface. An increased cell number is observed on APTES-anti STRO1, peptide and peptide-anti STRO1 coated PSi. The peptide-anti STRO1 provided the best cell proliferation results suggesting the improved accessibility of the recognition fragment of the antibody anti-STRO1.