Pre-wetted wipers clean up in sterile environments

If you had to describe the overriding characteristic of sterile environments in one word, that word might be "uncompromising", as it conveys the inflexibility of sterility requirements in these environments.^1,2

All items introduced into a sterile environment must also be sterile and not introduce unacceptable levels of contaminants, such as particles or residues. These requirements apply equally to contamination control products, such as wipers and cleaning solutions used within the sterile areas. Despite being cleaning products, they are not excused from the inflexible requirements for sterility and purity. Some pharmaceutical and biotechnology manufacturing plants have adopted sterile pre-wetted wipers as the best way to address critical cleaning issues in sterile environments. They have found that these cleaning products allow them to achieve the best results in a cost-effective manner. As the name suggests, sterile pre-wetted wipers are cleanroom wipers that have been pre-wetted with the optimum amount of 0.2µm filtered solvent – typically 70% isopropyl alcohol (IPA) solutions – to accomplish the cleaning task at hand. The wipers are also sterilised by gamma irradiation to a probability of non-sterility (or Sterility Assurance Level) of 10-6. This ensures that only one wiper out of a million will not be sterile. The wipers are generally packaged in sufficient quantities to last just one shift, on the premise that any consumable opened during the shift will not be used in a subsequent shift. This generally translates into 20-50 pre-wetted wipers per pack. The packaging is made from materials that will withstand gamma irradiation at the necessary dosage levels; that can be opened conveniently to withdraw the wipers and then closed or resealed to prevent evaporation of the wetting solution. One of the main advantages of sterile pre-wetted wipers is contamination control. The wipers are delivered ready for use, to wipe down critical surfaces before, during and after production shifts, inside and outside the sterile suite.

Simultaneous action The wipers provide a means of sanitising key surfaces and of simultaneously removing particulate matter that can act as transport vehicles for bacteria. They are particularly useful for wiping down any articles brought into the sterile suite; to sanitise those articles and physically remove endotoxins from surfaces. Sterile pre-wetted wipers have, for example, been used for wiping down gloves to maintain glove sterility during sterile suite activity. This has the advantage of simulta-neously sanitising the glove and physically removing dead bacteria from the glove surface, thereby reducing or eliminating a potential source of endotoxins. Spraying gloves with 70% IPA solution will sanitise the glove, but will not remove the dead bacteria. These wipers have also been found to reduce the incidence of false particle alarms caused by IPA spraying. In addition, the wipers are used to clean surfaces that have been contacted with environmental sampling devices, such as Rodac plates, to remove residual agar. If this is not done, the agar on the sampled surface acts as a culturing medium for opportunistic bacteria. Another benefit is the elimination of squirt bottles. When alcohol is dispensed onto a dry wiper from a squirt bottle, excessive amounts are often used because the operator's gloves prevent tactile feedback to indicate the optimum level of dampness. Since sterile pre-wetted wipers incorporate the optimum amount of 70% IPA for contamination control activities, there is less alcohol used in the facility and there may be an opportunity to eliminate squirt bottles and the transfer of bulk solvent. This can represent savings in solvent costs and in charges for volatile organic compound (VOC) emissions. Furthermore, sterile pre-wetted wipers eliminate fugitive emissions from squirt bottle dispense nozzles and from alcohol transfer operations. The wipers also offer cleanroom opera-tors greater convenience. While it may be difficult, it is not impossible to prepare sterile pre-wetted wipers within the sterile suite, based on the following steps: 1. Bring sterile dry wipers, packaging materials, graduated cylinders and sterile-filtered 70% IPA into the sterile environment. 2. Transfer the required number of wipers into the solvent-resistant packaging. 3. Transfer the required volume of sterile-filtered 70% IPA from the delivery container on to the wipers. 4. Close the packaging to allow the IPA to thoroughly dampen the wipers and prevent the liquid from evaporating. However, all of the process steps would need to be documented and validated to satisfy regulatory audits. Also, this seems like a lot of manual effort, if only 20 to 50 sterile pre-wetted wipers are needed for the shift. Likewise, it would be difficult, but not impossible, to prepare sterile pre-wetted wipers outside of the sterile suite. One could follow the steps outlined above, except that non-sterile wipers would be used. Once the pack of pre-wetted wipers had been formed, the product would then be gamma irradiated and transferred into the sterile suite. (Obviously, one would not autoclave pre-wetted wipers to try to render them sterile, as the high temperatures within the autoclave would volatilise the 70% IPA solution and probably burst the pack.) With this procedure, bioburden measurements, sterility validation and package integrity testing would be needed in addition to the usual documentation requirements. One could argue that if sterile pre-wetted wipers are to be used, they are best purchased rather than made in-house. The vendor of these products takes full responsibility for the necessary bioburden measurements, sterility validation programme, package integrity testing, certificates of compliance and irradiation and the process audit trail. Also, the vendor enjoys the economies of scale to provide a lower-cost product than could be made by the customer. Sterile pre-wetted wipers are useful for the cleaning and maintenance of critical surfaces inside and outside sterile suites and for wiping gloves during sterile manufacturing processes.