Biomedical Engineering Reference
In-Depth Information
of bone or soft tissue, thereby allowing inactivation of embedded pathogens. scCO
2
retains the diffusive
properties of CO
2
gas and thus can rapidly penetrate substrates.
The supercritical form of CO
2
is a more potent biocide than argon, nitrogen, and nitrous oxide used
under similar conditions, suggesting that its potency as a sterilant is derived from its chemical nature
as well as transformation to the supercritical state. In fact, scCO
2
on its own has been used to achieve
high levels of disinfection (Dillow et al., 1999), but to attain the sterility assurance level required for
medical devices (SAL6), a treatment must reduce the probability of contamination to 1 in one million,
when the initial bioburden of an item is ≥106 colony forming units (CFUs) of a bioindicator organism.
NovaSterilis developed NovaKill additive, a peracetic acid-based (PAA) entrainer (White et al., 2006).
Addition of NovaKill to a sterilization cycle using scCO
2
results in a SAL6 reduction in
B. atrophaeus
(standard biological indicator), which meets the definition for sterility. Furthermore, NovaSterilis has
shown that scCO
2
in the presence of Novakill additive can be used to inactive viruses and a host of
organisms including bacteria, molds, and other fungi.
In a recent collaborative preliminary study, Chu et al. have demonstrated that PGA sutures (Dexon)
can be sterilized by scCO
2
without any adverse effect on their tensile and hydrolytic degradation prop-
erties. In addition to achieving SAL6 sterilization on these sutures, we showed that the various tensile
properties (e.g., tensile strain, tensile stress, and Young's modulus) were unchanged between experi-
mental (sterilized) and control groups (Figure 5.16). Furthermore, the data in Figure 5.16 also show that
the scCO
2
sterilization process led to a better retention of Dexon suture mechanical properties than the
standard gas sterilization method (as control in Figure 5.16) upon
in vitro
degradation over a period of
27 days. Whether the NovaSterilis scCO
2
sterilization technology could be applied to other absorbable
polymers, further in-depth study would be required.
Defining Terms
Biodegradation:
Materials that could be broken down by nature either through hydrolytic mecha-
nisms without the help of enzymes and/or enzymatic mechanism. It is loosely associated with
absorbable, erodable, resorbable.
Tissue Engineering:
The ability to regenerate tissue through the help of artificial materials and
devices.
References
Ali, S.A.M., Zhong, S.P., Doherty, P.J., and Williams, D.F., 1993. Mechanisms of polymer degradation in
implantable devices. I. Poly(caprolactone).
Biomaterials
, 14: 648.
Atala, A., Kim, W., Paige, K.T., Vancanti, C.A., and Retil, A., 1994. Endoscopic treatment of vesicoureterall
reflux with a chondrocye-alginate suspension.
J. Urol.
, 152: 641-643.
Babior, B.M., Kipnes R.S., and Cumutte, J.T., 1973. Biological defense mechanisms. The production by
leukocytes of superoxide, a potential bactercidal agent.
J. Clin. Invest.,
52: 741.
Badwey, J.A. and Kamovsky, M.L., 1980. Active oxygen species and the functions of phagocytic leucocytes.
Ann. Rev. Biochem.,
49: 695.
Barrows, T.H., 1986. Degradable implant materials: A review of synthetic absorbable polymers and their
applications.
Clin. Mater.,
1: 233-257.
Barrows, T.H., 1994. Bioabsorbable poly(ester-amides). In:
Biomedical Polymers: Designed-to-Degrade
Systems
, S.W. Shalaby, Ed., New York, Hanser, Chap. 4.
Benedetti, L., Cortivo, R., Berti, T., Berti, A., and Pea, F., 1993. Biocompatibility and biodegradation of dif-
ferent hyaluronan derivatives (Hyaff) ) implanted in rats.
Biomaterials
, 14: 1154-1160.
Bezwada, R.S., Jamiolkowski, D.D., Lee, I.Y., Agarwal, V., Persivale, J., Trenka-Benthin, S., Erneta, M.,
Suryadevara, J., Yang, A., and Liu, S., 1995. Monocryl suture: A new ultra-pliable absorbable mono-
filament suture.
Biomaterials
, 16: 1141-1148.
