Franco Tasselli

Human hepatocyte functions in a crossed hollow fiber membrane bioreactor.

An important challenge in liver tissue engineering is the development of bioartificial systems that are able to favour the liver reconstruction and to modulate liver cell behaviour. A crossed hollow fiber membrane bioreactor was developed to support the long-term maintenance and differentiation of human hepatocytes. The bioreactor consists of two types of hollow fiber (HF) membranes with different molecular weight cut-off (MWCO) and physico-chemical properties cross-assembled in alternating manner: modified polyetheretherketone (PEEK-WC) and polyethersulfone (PES), used for the medium inflow and outflow, respectively. The combination of these two fiber set produces an extracapillary network for the adhesion of cells and a high mass exchange through the cross-flow of culture medium. The transport of liver specific products such as albumin and urea together with the transport of drug such as diazepam was modelled and compared with the experimental metabolic data. The theoretical metabolite concentration differed 7.5% for albumin and 5% for urea with respect to experimental data. The optimised perfusion conditions of the bioreactor allowed the maintenance of liver functions in terms of urea synthesis, albumin secretion and diazepam biotransformation up to 18 days of culture. In particular the good performance of the bioreactor was confirmed by the high rate of urea synthesis (28.7 microg/h 10(6) cells) and diazepam biotransformation. In the bioreactor human hepatocytes expressed at high levels the individual cytochrome P450 isoenzymes involved in the diazepam metabolism. The results demonstrated that crossed HF membrane bioreactor is able to support the maintenance of primary human hepatocytes preserving their liver specific functions for all investigated period. This device may be a potential tool in the liver tissue engineering for drug metabolism/toxicity testing and study of disease pathogenesis alternatively to animal experimentation.

Physicochemical characterization of solute retention in solvent resistant nanofiltration: the effect of solute size, polarity, dipole moment, and solubility parameter.

Growing interest in nanofiltration for solvent purification requires a fundamental understanding of the physicochemical mechanisms of solute retention in organic solvent nanofiltration. In this study, the retention of a similar series of azo dyes with approximately similar molar mass (around 350 Da) by four nanofiltration membranes was studied. The membranes used are commercially available polymeric nanofiltration membranes with molecular weight cutoff between 150 and 300 Da (DuraMem150, StarMem122, NF270 and Desal-Dk). In order to correlate the retention with the size of the molecules, which is assumed to be one of the main factors that determines the retention, use was made of different parameters for the molecular size: molar mass, the Stokes diameter, the equivalent molar diameter, and the cavity surface in methanol and ethanol. All parameters were calculated by using molecular dynamics simulations. For each size parameter, the correlation with retention in nanofiltration experiments was calculated. For the StarMem122 membrane, zero retentions were observed due to the swelling of the membrane and pore size enlargement in methanol and ethanol. For the three other membranes, a fairly good correlation of the retention with the size could only be observed if the size difference between compounds is sufficiently large. Two other factors were studied by using molecular dynamics, i.e., the polarity of the molecule and the electron density of the molecule. The importance of these factors depends on the structure of the molecule as well as the functional groups of the polymer. A very good correlation has been observed for retention of dyes versus their dipole moment. Finally, the effect of solubility parameters of dyes on their retention did not show any significant effect.

PAN hollow fiber membranes elicit functional hippocampal neuronal network.

This study focuses on the development of an advanced in vitro biohybrid culture model system based on the use of hollow fibre membranes (HFMs) and hippocampal neurons in order to promote the formation of a high density neuronal network. Polyacrylonitrile (PAN) and modified polyetheretherketone (PEEK-WC) membranes were prepared in hollow fibre configuration. The morphological and metabolic behaviour of hippocampal neurons cultured on PAN HF membranes were compared with those cultured on PEEK-WC HF. The differences of cell behaviour between HFMs were evidenced by the morphometric analysis in terms of axon length and also by the investigation of metabolic activity in terms of neurotrophin secretion. These findings suggested that PAN HFMs induced the in vitro reconstruction of very highly functional and complex neuronal networks. Thus, these biomaterials could potentially be used for the in vitro realization of a functional hippocampal tissue analogue for the study of neurobiological functions and/or neurodegenerative diseases.

Flat and tubular membrane systems for the reconstruction of hippocampal neuronal network.

The selection of appropriate biomaterials that promote cellular adhesion and growth is particularly important for the in vitro reconstruction of neuronal network. This study focused on the development of new polymeric membranes in flat and tubular (hollow‐fibre) configurations as novel biomaterials for neuronal outgrowth. Two membrane systems constituted by modified polyetheretherketone (PEEK‐WC) and polyacrylonitrile (PAN) membranes were developed and used for the culture of hamster hippocampal neurons. We demonstrated that all investigated membranes supported the adhesion and growth of hippocampal neurons enhancing neuronal differentiation and neurite alignment. The differences in cell behaviours between cells cultured on flat and hollow‐fibre (HF) membranes were highlighted by the quantitative analysis of neuronal marker fluorescence intensity, morphometric analysis, RT–PCR analysis and also by metabolic activity measurements. In particular, the PAN HF membranes showed ideal growth culture conditions, guaranteeing adequate levels of metabolic features. Primary hippocampal cells cultured on PAN HF membranes were able to recreate in vitro a 3D neural tissue‐like structure that, mimicking the hippocampal tissue, could be used as a tool for the study of natural and pathological neurobiological events. Copyright