Processable conducting graphene/chitosan hydrogels for tissue engineering.

Composites of graphene in a chitosan-lactic acid matrix were prepared to create conductive hydrogels that are processable, exhibit tunable swelling properties and show excellent biocompatibility. The addition of graphene to the polymer matrix also resulted in significant improvements to the mechanical strength of the hydrogels, with the addition of just 3 wt% graphene resulting in tensile strengths increasing by over 200%. The composites could be easily processed into three-dimensional scaffolds with finely controlled dimensions using additive fabrication techniques and fibroblast cells demonstrate good adhesion and growth on their surfaces. These chitosan-graphene composites show great promise for use as conducting substrates for the growth of electro-responsive cells in tissue engineering.

Growth, copper-tolerant cells, and extracellular protein production in copper-stressed chemostat cultures of Vibrio alginolyticus.

The influence of elevated copper concentrations on cell numbers and extracellular protein production was investigated in chemostat cultures of Vibrio alginolyticus. High (20 microM) copper in the medium reservoir resulted in a dramatic drop in cell numbers which was overcome with time. The copper-stressed cultures established a new equilibrium cell concentration slightly (ca. 20%) lower than control cultures. Copper-stressed chemostat populations contained an increased number of copper-resistant cells, but these averaged only 26% of the copper-adapted population. Previously copper-stressed populations exhibited resistance to a second challenge with copper. Proteins with properties identical to those of copper-induced, copper-binding proteins (CuBPs) observed in batch cultures of V. alginolyticus were observed in the supernatants of copper-stressed chemostat cultures and not in controls. CuBPs from batch and chemostat cultures were identical in terms of their induction by copper, molecular weight, and retention volumes on both immobilized copper ion-affinity chromatography and reverse-phase high-performance liquid chromatography columns. The concentration of CuBP in the chemostat was dependent on copper concentration in the medium reservoir. Either one or two forms of CuBP were observed in various analyses from both batch and chemostat cultures. Gel-to-gel variability was implicated as a factor determining whether one or two forms were resolved in a given analysis.(ABSTRACT TRUNCATED AT 250 WORDS)