Biomedical Engineering Reference
In-Depth Information
There is a wide choice available from 1 L to 3,500 L bags with a variety of
shapes, volume, available ports, tubing, in-line filters, and any other custom
feature besides the standard offering by these manufacturers. Generally, it
would be advisable to use an off-the-shelf item even though the generic man-
ufacturers offer custom bags readily: the reason for this choice is that there
is likely to be a larger volume of data available on off-the-shelf bags, and also
they are likely to be available on an as-needed basis.
The typical applications in bioprocessing use tank liners and 2D and
3D bags.
Tank Liners
Tank liners are simple, disposable bags used to line containers and transporta-
tion systems. In most cases, they are not gamma sterilized since these are used
in open systems most of the time, such as in the preparation of buffer solutions
and culture media at the first stage of preparation. The container within which
the liner is inserted is there only to provide mechanical support.
Commercially available overhead mixers can readily be integrated because
these systems are open. A broad choice of low-density polyethylene liners
are available from vendors that supply to several industries reducing the cost
of liners. Disposable equipment suppliers also offer these choices. For exam-
ple, Thermo Scientific's HyClone tank liners are designed for use with com-
mercially available overhead mixers. The chamber is constructed of CX3-9
film with dimensions optimized for Thermo Scientific HyClone standard
drums and commonly used industry standard cylindrical tanks. Top-entry
standard products for maximum recovery using industry standard connec-
tion systems in unit volumes of 50, 100, and 200 L. Tanks are supplied sterile
to minimize bioburden. A dolly is available to provide mobility of volumes
up to 500 L.
The hard-walled containers are necessary in the preparation of buffers and
media as this offers the cheapest alternative; however, these containers do not
contact any formulation component and, as a result, the cheapest containers
should be used. The most likely choice would be a plastic off-the-shelf drum,
such as a 55-gallon drum. Several major equipment suppliers provide a com-
plete line of mixing systems and, while these do offer an advantage in han-
dling large volumes consistently, one can readily put together a system from
off-the-shelf components at a substantially lower cost. It is noteworthy that
the more expensive systems come with programming elements that might
make the Process Analytic Technology (PAT) work easier but, at the stage of
buffer and media preparation, the challenges are few and readily overcome
by implementing the simplest and cheapest systems. This is what is intended
in the max-dispo concept—to use only what adds value.
