Thermal inkjet printing technology has been applied successfully to cell printing. However, there are concerns that printing process may cause cell damages or death. We conducted a comprehensive study of thermal inkjet printed Chinese hamster ovary (CHO) cells by evaluating cell viability and apoptosis, and possible cell membrane damages. Additionally, we studied the cell concentration of bio-ink and found optimum printing of concentrations around 8 million cells per mL. Printed cell viability was 89% and only 3.5% apoptotic cells were observed after printing. Transient pores were developed in the cell membrane of printed cells. Cells were able to repair these pores within 2 h after printing. Green fluorescent protein (GFP) DNA plasmids were delivered to CHO-S cells by co-printing. The transfection efficiency is above 30%. We conclude that thermal inkjet printing technology can be used for precise cell seeding with minor effects and damages to the printed mammalian cells. The printing process causes transient pores in cell membranes, a process which has promising applications for gene and macroparticles delivery to induce the biocompatibility or growth of engineered tissues.
Chondrocytes are influenced by mechanical forces to remodel cartilage extracellular matrix. Previous studies have demonstrated the effects of mechanical forces on changes in biosynthesis and mRNA levels of particular extracellular matrix molecules, and have identified certain signaling pathways that may be involved. However, the broad extent and kinetics of mechano-regulation of gene transcription has not been studied in depth. We applied static compressive strains to bovine cartilage explants for periods between 1 and 24 h and measured the response of 28 genes using real time PCR. Compression time courses were also performed in the presence of an intracellular calcium chelator or an inhibitor of cyclic AMP-activated protein kinase A. Cluster analysis of the data revealed four main expression patterns: two groups containing either transiently up-regulated or duration-enhanced expression profiles could each be subdivided into genes that did or did not require intracellular calcium release and cyclic AMP-activated protein kinase A for their mechano-regulation. Transcription levels for aggrecan, type II collagen, and link protein were up-regulated ϳ2-3-fold during the first 8 h of 50% compression and subsequently down-regulated to levels below that of free-swelling controls by 24 h. Transcription levels of matrix metalloproteinases-3, -9, and -13, aggrecanase-1, and the matrix protease regulator cyclooxygenase-2 increased with the duration of 50% compression 2-16-fold by 24 h. Thus, transcription of proteins involved in matrix remodeling and catabolism dominated over anabolic matrix proteins as the duration of static compression increased. Immediate early genes c-fos and c-jun were dramatically up-regulated 6 -30-fold, respectively, during the first 8 h of 50% compression and remained up-regulated after 24 h. Articular cartilage is responsible for the smooth articulation of synovial joints during locomotion. Chondrocytes within cartilage constantly remodel the extracellular matrix (ECM) 1 of the tissue throughout life. The major load-bearing constituents of the ECM are type II collagen and aggregates of the proteoglycan, aggrecan, which provide the tensile and compressive stiffness of the tissue, respectively. Also present in the ECM are families of matrix proteinases, tissue inhibitors of matrix metalloproteinases (TIMPs), growth factors, and cytokines that together regulate ECM remodeling and turnover in health and disease (1). It is known that mechanical exercise of the knee joint in vivo increases the density of aggrecan in cartilage (2), whereas knee joint inactivity results in decreased aggrecan deposition (3, 4). Traumatic injury to cartilage diminishes mechanical strength and leads to excessive catabolism of the ECM, increasing the risk of osteoarthritis later in life (5).A number of model systems have been developed to simulate various aspects of the mechanical loading forces experienced by articular cartilage in vivo. Compressive and shear forces have been applied to cartilage explants and chondrocyte cul...
Intermolecular repulsion forces between negatively charged glycosaminoglycan (CS-GAG) macromolecules are a major determinant of cartilage biomechanical properties. It is thought that the electrostatic component of the total intermolecular interaction is responsible for 50-75% of the equilibrium elastic modulus of cartilage in compression, while other forces (e.g., steric, hydration, van der Waals, etc.) may also play a role. To investigate these forces, radiolabeled CS-GAG polymer chains, with a fully extended contour length of 35 nm, were chemically end-grafted to a planar surface to form model biomimetic polyelectrolyte "brush" layers whose environment (e.g., ionic strength, pH) was varied to mimic physiological conditions. The total intersurface force (enN) between the CS-GAG brushes and chemically modified probe tips (SO 3 -and OH) was measured as a function of tip-substrate separation distance in aqueous solution using the technique of high-resolution force spectroscopy (HRFS). These experiments showed long-range, nonlinear, purely repulsive forces that decreased in magnitude and range with increasing ionic strength and decreasing pH. To estimate the contribution of the electrostatic component to the total intersurface force, the data were compared to a theoretical model of electrical double layer repulsion based on the Poisson-Boltzmann formulation. The CS-GAG brush layer was approximated as either a flat surface charge density or a smoothed volume of known fixed charge density and the probe tip was modeled as a smooth hemisphere of constant surface charge density. Modeling the CS-GAG brush as a volume charge yielded theoretical fits much closer to the experimental data and is a good first step toward deconvolution of the force components.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.