Biomedical Engineering Reference
In-Depth Information
Fluoropolymer Bags
Fluorinated polymers such as Teflon (polytetrafluoroethylene) do not con-
tain any extractables or leachables and will ideally be the choice for mak-
ing disposable bags. While the science to do this is available today, the
disposable bags industry remains locked in with traditional polyethylene
bags with its chemical additives, mainly because they have already made
huge investments in the equipment to make these bags and partly because
of the ease how standard plastic bags are made. For example, a tempera-
ture of 400°F is sufficient to seal plastic bags, and a temperature of 800°F
is need to handle Teflon: the current manufacturing technology would
require a total revamp to accommodate Teflon bags. Other problems in
the use of fluoropolymer compounds are their permeability to gases, and
one form of Teflon, Gore-Tex, even allows moisture to escape but retains
water inside. To overcome these problems, MayaBio (
www.mayabio.com
)
has established a proof of principle of using a “double bagging” system
whereby a Teflon bag is inserted inside a plastic bag and the culture media
comes in contact with Teflon only. Studies are needed to confirm that the
surface characteristics of Teflon will not adversely affect the growth of cul-
ture media. However, the basic principle has been earlier proven using
animal cells and using Teflon bags to produce working culture. If Teflon or
Telfon-coating plastic becomes readily available, this would eliminate one
of the most significant hurdles in the acceptance of disposable bioreactors
as the regulatory requirements of proving the safety of contact materials
would be removed.
Protein Capture
Target protein-specific resins will be developed that will allow fewer
steps in downstream purification. The example of Protein A as a capture
resin for monoclonal antibodies will be extended to other types of res-
ins, and affinity chromatography would become the most widely used
method for downstream processing. U.S. Patent (xx) reports a new kind of
bioreactor that captures the target molecules as they are produced using
an electro-deionization step. Other recent filings with the U.S. Patent and
Trademark Office show that it will be possible in the future to remove
target proteins directly from the bioreactor and even perform purification
using the bioreactor as the downstream column. Details are available at
