SPOTLIGHT

& A Competitive Edge in MembraneChromatography

Membrane chromatography which combines the advantages of

membrane technology and chromatography has great potential for

application in the biopharmaceutical industry. However, currently

available chromatographic membranes are expensive and some

show a biofouling tendency. The competitive edge of membrane

chromatography could therefore be further enhanced by addres-

sing these issues. A group of researchers at McMaster University led

by Professor Ghosh and Professor Pelton have developed filter

paper-based chromatographic membranes which can be manu-

factured economically and show less tendency to foul due to their

open structure. In their current work, Yu and co-workers discuss

the preparation of polyethylene glycol (PEG)-grafted filter paper as

an inexpensive alternative to currently available adsorptive

membranes; use of the grafted filter paper for hydrophobic

interaction membrane chromatography (HIMC)-based purifica-

tion of a humanized monoclonal antibody is also described.

Page 1434

DOI: 10.1002/bit.21858

& Expediting the Adaptation Process

In recognition of the issues associated with the use of animal-

derived serum to propagate mammalian cells in culture,

procedures have been developed to adapt cells to grow without

serum. However, these procedures are lengthy and cells often

undergo some physiological changes. In this work, Jaluria and co-

workers applied bioinformatics tools, including DNA microarrays,

to correlate the transcriptome of Human Embryonic Kidney cells

(HEK-293)-gradually adapted to serum free media-with the

physiological responses associated with serum withdrawal. Using

this information, cells were engineered to determine the feasibility

of expediting the adaptation process through targeted gene

modification. Data analysis detected a few genes with expression

patterns correlated to decreasing serum levels. Two of these genes,

early growth response 1 (egr1) and growth arrest specific 6 (gas6),

were found to improve growth rates and viabilities when over-

expressed as compared to the wild-type cells. Such cell engineering

approaches may facilitate cellular adaptation to new environments.

Page 1443

DOI: 10.1002/bit.21859

& Stable Mammalian Cell Reporter Gene Assaysin Lipophilic Chemical Screening

With recent concerns on the effects of lipophilic chemicals or

hormones on human health, the establishment of various nuclear

receptor-based evaluation methods is required. Among these

methods, mammalian cell reporter gene assays have shown high

popularity as lipophilic chemicals are sensed, evaluated, and

analyzed directly through a reporter gene within a whole cell.

Recent work from the Matsunaga group has established a novel

stable reporter cell line via site-specific genomic recombination by

integrating a human glucocorticoid receptor (hGR) gene, its

response element and a luciferase reporter gene into the genome of

a host HeLa cell line. The reporter cell established showed high

sensitivity, selectivity, stability, and specificity against receptor-

specific lipophilic chemicals. The platform technology which is

designed based on recombinase-mediated cassette exchange

(RMCE), is simple, reproducible, and shows great potential in

the future development of stable reporter gene assays of various

nuclear receptors in a specific host cell type. Page 1453

DOI: 10.1002/bit.21860

& Improving Cell Performance by EngineeringOxygen Transport

Of the range of configurations used in creating tissue equivalents,

packed bed systems-consisting of cells embedded within either

extracellular matrix (ECM) or synthetic polymeric systems-

represent one 3D option. Unfortunately the limited transport

distance of oxygen through the cellular space of such systems has

been a key challenge to scaling them up for higher functional

outputs. To address this, the Coger group previously reported a

novel technique to create micropathways for enhanced oxygen

transport by dispersing microspheres throughout the ECM. The

strength of the technique is its simplicity and adaptability. In their

current offering, they demonstrate how the technique can be tailor-

ed to extend the oxygen transport distance to over 400 microns. An

added benefit of the technique is that it is also effective in protecting

the packed cells from exposure to severe hypoxia and hyperoxia.

Page 1502

DOI: 10.1002/bit.21817

Published online in Wiley InterScience

(www.interscience.wiley.com).

� 2008 Wiley Periodicals, Inc. Biotechnology and Bioengineering, Vol. 99, No. 6, April 15, 2008