Living Biomaterials to Engineer Hematopoietic Stem Cell Niches.

Living biointerfaces are a new class of biomaterials combining living cells and polymeric matrices that can act as biologically active and instructive materials that host and provide signals to surrounding cells. Here, living biomaterials based on Lactococcus lactis to control hematopoietic stem cells in 2D surfaces and 3D hydrogels are introduced. L. lactis is modified to express C-X-C motif chemokine ligand 12 (CXCL12), thrombopoietin (TPO), vascular cell adhesion protein 1 (VCAM1), and the 7th-10th type III domains of human plasma fibronectin (FN III7-10 ), in an attempt to mimic ex vivo the conditions of the human bone marrow. These results suggest that living biomaterials that incorporate bacteria expressing recombinant CXCL12, TPO, VCAM1, and FN in both 2D systems direct hematopoietic stem and progenitor cells (HSPCs)-bacteria interaction, and in 3D using hydrogels functionalized with full-length human plasma fibronectin allow for a notable expansion of the CD34+ /CD38- /CD90+ HSPC population compared to the initial population. These results provide a strong evidence based on data that suggest the possibility of using living materials based on genetically engineered bacteria for the ex-vivo expansion of HSPC with eventual practical clinical applications in HSPCs transplantation for hematological disorders.

Bacteria-Based Materials for Stem Cell Engineering.

Materials can be engineered to deliver specific biological cues that control stem cell growth and differentiation. However, current materials are still limited for stem cell engineering as stem cells are regulated by a complex biological milieu that requires spatiotemporal control. Here a new approach of using materials that incorporate designed bacteria as units that can be engineered to control human mesenchymal stem cells (hMSCs), in a highly dynamic-temporal manner, is presented. Engineered Lactococcus lactis spontaneously colonizes a variety of material surfaces (e.g., polymers, metals, and ceramics) and is able to maintain growth and induce differentiation of hMSCs in 2D/3D surfaces and hydrogels. Controlled, dynamic, expression of fibronectin fragments supports stem cell growth, whereas inducible-temporal regulation of secreted bone morphogenetic protein-2 drives osteogenesis in an on-demand manner. This approach enables stem cell technologies using material systems that host symbiotic interactions between eukaryotic and prokaryotic cells.

Effects of Fluorodeoxyglucose Conjugated and Unconjugated Iron Oxide Magnetic Nanoparticles on Macrophages: a Pilot Study

Abstract The effects of fluorodeoxyglucose conjugated iron oxide magnetic nanoparticles (FDGMNP) on macrophages are presented using a yeast substrate. Iron oxide magnetic nanoparticles (MNP) were synthesized by partially reducing FeCl3, then conjugated with (3-aminopropyl) triethoxysilane (APTES) after silication with tetraethyl orthosilicate. Silanated MMP nanoparticles were combined with fluorodeoxyglucose (FDG). Fluorodeoxyglucose iron oxide magnetic nanoparticles (FDGMNP) and its unconjugated control (MNP) were added (1mL) to the cells from the murine macrophage-like, Abelson murine leukemia virus transformed cell line RAW 264.7 (American Type Culture Collection number TIB-71) cell culture wells at different concentrations from 90-3.6 μg/mL. Cells were placed on the magnet plate for 30 min before incubating at 37°C, 5% CO2 overnight. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium) assay was performed to measure cell viability. Our results demonstrate that iron based nanoparticles can be linked to macrophages (elements of the immune system that attack bacteria) without the function of the macrophages being affected, ie no detrimental effects to the macrophages were evident in these experiments. We conclude that neither FDGMNP nor MNP had a detrimental effect on macrophage function.