Background: Geobacter metallireducens was the first organism that can be grown in pure culture to completely oxidize organic compounds with Fe(III) oxide serving as electron acceptor. Geobacter species, including G. sulfurreducens and G. metallireducens, are used for bioremediation and electricity generation from waste organic matter and renewable biomass. The constraint-based modeling approach enables the development of genomescale in silico models that can predict the behavior of complex biological systems and their responses to the environments. Such a modeling approach was applied to provide physiological and ecological insights on the metabolism of G. metallireducens.

Cell microencapsulation holds significant promise as a strategy for cellular therapies; however, inadequate survival and functionality of the enclosed cells limit its application in hemophilia treatment. Here, we evaluated the use of alginate-based microcapsules to enhance the viability and transgene secretion of human cord blood–derived mesenchymal stem cells in three-dimensional cultures. Given the positive effects of extracellular matrix molecules on mesenchymal stem cell growth, we tested whether fibrinogen-supplemented alginate microcapsules can improve the efficiency of encapsulated factor IX–engineered mesenchymal stem cells as a treatment of hemophilia B. We found that fibrinogen-supplemented alginate microcapsules (a) significantly enhanced the viability and proliferation of factor IX–engineered mesenchymal stem cells and (b) increased factor IX secretion by mesenchymal stem cells compared to mesenchymal stem cells in nonsupplemented microcapsules. Moreover, we observed the osteogenic, but not chondrogenic or adipogenic, differentiation capability of factor IX–engineered cord blood mesenchymal stem cells and their efficient factor IX secretion while encapsulated in fibrinogen-supplemented alginate microcapsules. Thus, the use of engineered mesenchymal stem cells encapsulated in fibrinogen-modified microcapsules may have potential application in the treatment of hemophilia or other protein deficiency diseases.

This article describes the formation of cross-linked 10-200-nm-thick polymer hydrogel films by alternating the spin-coating of two mutually reactive polymers from organic solutions, followed by hydrolysis of the resulting multilayer film in aqueous buffer. Poly(methyl vinyl ether-alt-maleic anhydride) (PMM) was deposited from acetonitrile solution, and poly(N-3-aminopropylmethacrylamide-co-N-2-hydroxypropylmethacrylamide) (PAPMx, where x corresponds to the 3-aminopropylmethacrylamide content ranging from 10 to 100%) was deposited from methanol. Multilayer films were formed in up to 20 deposition cycles. The films cross-linked during formation by reaction between the amine groups of PAPMx and the anhydride groups of PMM. The resulting multilayer films were covalently postfunctionalized by exposure to fluoresceinamine, decylamine, d-glucamine, or fluorescently labeled PAPMx solutions prior to the hydrolysis of residual anhydride in aqueous PBS buffer. This allowed tuning the hydrophobicity of the film to give static water contact angles ranging from about 5 to 90°. Increasing the APM content in PAPMx from 10 to 100% led to apparent Young's moduli from 300 to 700 kPa while retaining sufficient anhydride groups to allow postfunctionalization of the films. This allowed the resulting (PMM/PAPMx) multilayer films to be turned into adhesion-promoting or antifouling surfaces for C2C12 mouse myoblasts and MCF 10A premalignant human mammary epithelial cells.

The success of cell microencapsulation technology in tissue engineering and protein delivery applications depends on the viability and functionality of the encapsulated cells, which in turn are dependent upon cell/matrix interactions. In this work, we compared the viability of cord blood-derived mesenchymal stromal cells (CB MSCs), engineered to secrete factor IX (FIX) for hemophilia treatment, and encapsulated in arginine-glycine-aspartate (RGD)-alginate versus fibrinogen-alginate microcapsules. We evaluated the effect of the biomimetic matrix on cell attachment, proliferation, and secretion of FIX. Compared with nonsupplemented alginate matrix, RGD-alginate significantly enhanced the viability of the encapsulated MSCs. Further, cells in RGD-alginate displayed distinct attachment morphology, thus suggesting that RGD-alginate can potentially be used for the encapsulation of MSCs in tissue engineering applications that require enhanced cell attachment and viability. However, our data also showed that RGD-alginate microcapsules, in contrast to fibrinogen-alginate microcapsules, did not significantly improve cell proliferation of or FIX secretion by encapsulated MSCs. Our findings suggest that evidence of cell attachment alone may not accurately predict the functionality of cells in biomimetic microcapsules.

Continuous delivery of proteins by engineered cells encapsu-lated in biocompatible polymeric microcapsules is of considerable therapeutic potential. However, this technology has not lived up to expectations due to inadequate cell--matrix interactions and subsequent cell death. In this study we hypoth-esize that the presence of fibronectin in an alginate matrix may enhance the viability and functionality of encapsulated human cord blood-derived mesenchymal stromal cells (MSCs) expressing the human Factor IX (FIX) gene. MSCs were encapsulated in alginate-PLL microcapsules containing 10, 100, or 500 μg/ml fibronectin to ameliorate cell survival. MSCs in microcapsules with 100 and 500 μg/ml fibronectin demonstrated improved cell viability and proliferation and higher FIX secretion compared to MSCs in non-supplemented microcapsules. In contrast, 10 μg/ml fibronectin did not significantly affect the viability and protein secretion from the encapsulated cells. Differentiation studies demonstrated osteogenic (but not chondrogenic or adipogenic) differentiation capability and efficient FIX secretion of the enclosed MSCs in the fibronectin-alginate suspension culture. Thus, the use of recombinant MSCs encapsulated in fibronectin-alginate microcapsules in basal or osteogenic cultures may be of practical use in the treatment of hemophilia B.