Functionalized alginate-based bioinks for microscale electrohydrodynamic bioprinting of living tissue constructs with improved cellular spreading and alignment

Bioprinting has been widely investigated for tissue engineering and regenerative medicine applications.However,it is still difficult to reconstruct the complex native cell arrangement due to the limited printing resolution of conventional bioprinting techniques such as extrusion-and inkjet-based printing.Recently,an electrohydrodynamic(EHD)bioprinting strategy was reported for the precise deposition of well-organized cell-laden constructs with microscale filament size,whereas few studies have been devoted to developing bioinks that can be applied for EHD bioprinting and simultaneously support cell spreading.This study describes functionalized alginate-based bioinks for microscale EHD bioprinting using peptide grafting and fibrin incorporation,which leads to high cell viability(>90%)and cell spreading.The printed filaments can be further refined to as small as 30μm by incorporating polyoxyethylene and remained stable over one week when exposed to an aqueous environment.By utilizing the presented alginate-based bioinks,layer-specific cell alignment along the printing struts could be observed inside the EHD-printed microscale filaments,which allows fabricating living constructs with cell-scale filament resolution for guided cellular orientation.

A numerical method to predict the membrane tension distribution of spreading cells based on the reconstruction of focal adhesions

Changes in membrane tension significantly affect the physiological functions of cells in various ways.However,directly measuring the spatial distribution of membrane tension remains an ongoing issue.In this study,an algorithm is proposed to determine the membrane tension inversely by executing a particle-based method and searching for the minimum deformation energy based on the cell images and focal adhesions.A standard spreading cell model is established using 3D reconstructions with images from structured illumination microscopy as the reference cell shape.The membrane tension distribution,forces across focal adhesions,and profile of the spread cell are obtained using this method,until the cell deformation energy function optimization converges.Qualitative and quantitative comparisons with previous experimental results validated the reliability of this method.The results show that in the standard spreading cell model,the membrane tension decreases from the bottom to the top of the membrane.This method can be applied to predict the membrane tension distribution of cells freely spreading into different shapes,which could improve the quantitative analysis of cellular membrane tension in various studies for cell mechanics.

RNA silencing movement in plants

Multicellular organisms, like higher plants, need to coordinate their growth and development and to cope with environmental cues. To achieve this, various signal molecules are transported between neighboring cells and distant organs to control the fate of the recipient cells and organs. RNA silencing produces cell non-autonomous signal molecules that can move over short or long distances leading to the sequence specific silencing of a target gene in a well defined area of cells or throughout the entire plant,respectively. The nature of these signal molecules, the route of silencing spread, and the genes involved in their production, movement and reception are discussed in this review. Additionally, a short section on features of silencing spread in animal models is presented at the end of this review.