Biomedical Engineering Reference
In-Depth Information
LuerLok syringe. A dynamic seal inside the valve guarantees that the sample
is not taken until the syringe is connected, thereby ensuring the sample only
comes in contact with the inner, aseptic parts of the valve. However, the sam-
ples drawn do not remain sterile.
Manifolds consisting of sampling bags, sampling flasks, or syringes are
appropriate for taking aseptic samples in disposable systems. These mani-
folds can be connected to the systems via aseptic connectors or tube weld-
ing. Sampling manifolds allow multiple sampling for quality purposes over
a given period of time. The main feature of the manifold is that the number
of manipulations in a process is significantly reduced. The manifold systems
are delivered ready for process use, preassembled, and sterile. Only one con-
nection has to be made to allow several bags to be filled.
Also used for sampling are manifold systems where sample containers of
a manifold are arranged in parallel whereby the last one is used as a waste
container. Through using Y-, T-, or X-hose barbs and tube clamps, the initial
flow and the subsequent sample are guided to the appropriate containers.
SIP connections, of course, also allow the connection of manifold systems to
conventional stainless steel processing equipment.
Conclusion
The complexity of bioprocessing makes it difficult to design systems with-
out any weak links; contamination is indeed the most significant risk, which
requires that all connectors, tubing, and implements joining various steps
of a process and performing sampling remain patent. Disposable connec-
tors and tubing were one of the first components that went disposable. Still,
in hard-walled systems, SIP systems are in use only because there is steam
for CIP/SIP operations. Even then, the risk of contamination remains. Since
much of the disposable technology in these applications has come from
the biomedical field, the device industry had always been ahead of the
regulatory requirements. Biocompatibility issues have long been resolved
and vendors are able to provide detailed information on their devices that
might be needed by regulatory agencies. Since the manufacturing of these
devices is complex, it is unlikely for a user to request custom devices; how-
ever, the diversity of choices available today is enough to modify any sys-
tem that would be able to use an off-the-shelf item. As before, the emphasis
on the importance of an off-the-shelf item over custom designs remains.
The tube connectors and sealers are a newer entry as disposable bags for
mixing, and bioreactors have becoming more popular; still, there is a limited
choice of suppliers, mainly GE and Sartorius-Stedim. The cost of this equip-
ment is still high, but then the alternative comes down to using expensive
