De­vel­op­ment of a novel low-tem­per­a­ture ster­il­iza­tion pro­ce­dure using su­per­crit­i­cal car­bon diox­ide and of com­pat­i­ble nanocom­pos­ites for med­i­cal de­vices


Ther­mo­la­bile med­i­cal de­vices which are sur­gi­cal­ly in­sert­ed, such as flex­i­ble en­do­scopes that are ap­plied in the asep­tic vis­cer­al cav­i­ty, are clas­si­fied as “crit­i­cal C”-de­vices with re­gard to re­pro­cess­ing. These de­vices are ster­il­ized using spe­cial low-tem­per­a­ture pro­ce­dures. Con­ven­tion­al low-tem­per­a­ture pro­ce­dures relay on toxic chem­i­cal agents like e.g. ethy­lene oxide or on the ap­pli­ca­tion of ion­iz­ing ra­di­a­tion (60Co). Other pro­ce­dures are under dis­pute with re­gard to pro­cess per­for­mance when ap­plied to ge­o­met­ri­cal­ly com­plex de­vices. Aim of the pro­ject was the de­vel­op­ment of a novel low-tem­per­a­ture pro­ce­dure (< 40 °C) using high­ly com­pressed su­per­crit­i­cal car­bon diox­ide (SCCO2) al­low­ing ster­il­iza­tion of ther­mo­la­bile, ge­o­met­ri­cal­ly com­plex med­i­cal de­vices such as e.g. flex­i­ble en­do­scopes. This re­search work was per­formed by the wfk – Clean­ing Tech­nol­o­gy In­sti­tute (Ger­many). Suit­able pro­cess chal­lenge de­vices (PCDs) were de­vel­oped and ap­plied with dif­fer­ent mi­croor­gan­isms in SCCO2 pro­cess­es to quan­ti­fy the an­timi­cro­bial ef­fect. An ap­pro­pri­ate ad­di­tive com­bi­na­tion was de­vel­oped and used to en­hance the an­timi­cro­bial ef­fect. Var­i­ous ster­ile bar­ri­er sys­tems were in­ves­ti­gat­ed for their com­pat­i­bil­i­ty with the de­vel­oped SCCO2 method and a suit­able sys­tem based on Tyvek®/film was cho­sen. Re­sults showed that phase-tran­si­tion-cy­cles (su­per­crit­i­cal CO2 ➝ liq­uid CO2) and rel­a­tive move­ment of SCCO2 have a con­sid­er­able pos­i­tive ef­fect on the in­ac­ti­va­tion of mi­croor­gan­isms in par­tic­u­lar when ap­plied on com­plex PCDs. The ef­fi­ca­cy of the SCCO2 pro­cess was con­firmed on com­plex tubu­lar PCDs. In prac­tice, based on the char­ac­ter­ized pa­ram­e­ters, the pro­cess has to be adapt­ed de­pend­ing on the med­i­cal de­vices to be ster­il­ized.

In par­al­lel Mon­ta­nuni­ver­sität Leoben (Aus­tria) de­vel­oped novel poly­mer ma­te­ri­als with com­pat­i­bil­i­ty against SCCO2 ster­il­iza­tion pro­ce­dures to be avail­able for the man­u­fac­tur­ing of med­i­cal de­vices such as e.g. flex­i­ble en­do­scopes. By in­cor­po­ra­tion of nanopar­ti­cles (e.g. cel­lu­lose or ze­o­lite) as filler sub­stances these poly­mers ex­hib­it­ed im­proved bar­ri­er/dif­fu­sion prop­er­ties and com­pat­i­bil­i­ty against SCCO2. The ap­pli­ca­tion of 2-5 % nanoscaled fillers showed most im­proved re­sults re­gard­ing min­i­miza­tion of CO2 up­take (re­duced by up to 90 %) and me­chan­i­cal prop­er­ties. Four ma­te­ri­als which showed ex­cel­lent com­pat­i­bil­i­ty against SCCO2 were de­vel­oped and are now ready for the de­vel­op­ment of fu­ture gen­er­a­tions of med­i­cal de­vices.

Re­pro­cess­ing ser­vice providers/cen­tral ster­il­i­sa­tion ser­vice staff, op­er­a­tors of de­vices, physi­cians as well as pa­tients of the 30,000 hos­pi­tals and count­less doc­tor´s of­fices with­in the EU ben­e­fit from the pro­ject re­sults. Fur­ther ben­e­fi­cia­ries are man­u­fac­tur­ers of high pres­sure de­vices and ster­il­i­sa­tion de­vices. The de­vel­op­ment of new nanocom­pos­ites will be prof­itable for sev­er­al thou­sand medtech com­pa­nies for the evo­lu­tion of a new gen­er­a­tion of med­i­cal de­vices.

The research report is available on request from FRT.

The IGF-pro­ject IGF 98 EN of the re­search as­so­ci­a­tion Europäische Forschungs­ge­mein­schaft Reini­gungs- und Hy­gien­etech­nolo­gie e.V., Cam­pus Ficht­en­hain 11, 47807 Krefeld, was sup­port­ed via the AiF with­in the fund­ing pro­gram „In­dus­trielle Gemein­schafts­forschung und -en­twick­lung (IGF)“ by the Fed­er­al Min­istry of Eco­nom­ic Af­fairs and Cli­mate Ac­tion due to a de­ci­sion of the Ger­man Par­lia­ment.