Gamma rays are high energy photons with extremely short wavelengths that can pass through cell membrane and damage DNA via destroying the helix directly, thereby damaging the deoxyribose or disrupting the covalent bonds within the DNA. Sterilization by radiation, primarily Cobalt-60 gamma rays or electron accelerators, is used as the technique for achieving required sterility assurance for some 50% of single-use medical devices, with gamma irradiation being most widely used technology.
Cobalt-60 (Co-60) is a synthetic isotope produced in 20 nuclear reactors. The word Cobalt originates from the German word Kobald; Kobald means goblin or mischievous spirit. Over 200 commercial scale gamma irradiators operate worldwide with an estimate of 80% of their capacity used for sterilization, equivalent to about one-third of single-use devices. When sterilizing medical devices, the radiation dose is entirely dependent on the bioburden of the device. Ethylene (EtO) Oxide "gas" sterilization is likely too expensive for a $200-$600 tattoo pen and would require a considerable investment in pens for turnaround times. Your tattoo artist is more than likely using chemical solvents, which do not work or Gamma Ray Radiation as tattoo pens fragile digital internal computers cannot tolerate the rigorous steam and pressure of an autoclave. Even if the pens could undergo a autoclave there is a standard three step sterilization process which pens cannot undergo and even that process is vulnerable to disease like prions. With complex reusable digital instruments such as a tattoo pens there is substantial uncertainty of the required sterility assurance in any case scenario except single-use. Gamma Ray treatment is best used for the sterilization of single-use medical products rather than reusable tattoo pens. Some standard, stainless-steel reusable medical instruments such as scissors and forceps are being sterilized uniformly using gamma irradiation. Instruments such as tattoo pens will degrade overtime using gamma irradiation sterilization with different reactions occurring depending on the type of polymer.
Silicone rubber are radio-sensitive polymers and the sterilization by a standard dose of gamma radiation (25 kGy) induces irreversible structural changes in these materials. Cosmetics and toiletries also undergo Gamma Ray Sterilization to ensure consumer safety and product integrity. There are no FDA-cleared ionizing radiation sterilization processes for use in healthcare facilities. Gamma Irradiation sterilization using Cobalt-60 takes several hours. Cobalt-60 is stored in a water storage pool to prevent contamination of the facility and personnel. Gamma irradiation is able to be applied using a terminal sterilization method, such as tattoo ink sealed in a bottle from the manufacturing facility and sterilized from the outside-in, completely sealed, for single-use or a sterile in-house distribution method without exposure to contaminates.
The effects of ionizing radiation on bacteria are generally evaluated from the dose-dependent survival ratio, which is determined by colony-forming ability and mutation rate. The mutagenic damage to cellular DNA induced by radiation has been extensively investigated; however, the effects of irradiation on the cellular machinery in-situ remain uncovered. Generic risks of using ionizing radiation sterilization for reusable instruments, especially ones involved in applying incisions such as tattoo pens is multi-fold; the bioburden of microscopic germs, mold, and spores decree specific differential levels of ionizing radiation and uniform application using dosimeters strategically placed throughout the load to ensure uniform dose distribution to establish the appropriate dose of radiation necessary to achieve the desired Sterility Assurance Level (SAL); and if a parthenogen survives ionizing radiation, likely with the capability to repair single strand breaks, due to the activity of their DNA repair enzyme, there is a very high chance that particular pathogenic microorganism, quite benefits from ionizing radiation and will continue to build and mutate and can create stronger so-called super-bugs with each application and could source new mutations from samples of contaminated medical equipment if the necessary health safety standards are not kept intact.
After a short incubation period the fragmented genomic DNA converts to larger molecular weight species, similar to the DNA of unirradiated controls. This results in mutagenic but nondetrimental gap repair and provides an effective mechanism for generating genetic variation in bacteria adapting to environmental stress. Requirements of radiation validations and quarterly dose audits are provided in the ANSI/AAMI/ISO 11137 standard series. The dose to product depends — at a constant energy — on beam current I, beam width SW and the speed of the product V (conveyor speed) as it moves through the irradiation zone. This relationship can be expressed as: Dose = k (I/(SW × V)
Saccharomyces cerevisiae (Brewer's Yeast) displays DNA postreplication repair (PRR). Viruses are more resistant to radiation than bacterial spores, bacterial spores are more resilient than vegetative bacteria, yeasts and molds. Parasites and helmints are more radio-resistant then bacteria: high doses of radiation (4-6kGy) have to be used for their elimination. If a pathogen survives from an incision during a medical procedure through ionizing irradiation sterilization, the pathogen will likely continue to survive any further forms of ionizing radiation sterilization procedures. The pathogen mutates from one medical application, to the next medical application and can even spread to other instruments in the radiation chamber if not properly packaged and handled. The pathogen can mutate into what is effectively an ionizing radiation resistant mutant variant whose evolution will be exemplified by successful transmission within the sterilization chamber. The pathogen, unaffected, could effectively utilize the sterilization chamber as a transmissible host. Whether or not a mutant variant pathogen contaminate within the sterilization chamber is contained at the industrial level or not, relies on the assurity of thousands pieces of packaging material a day, each about the density of a postcard.
Pre-irradiation Preparation:
Medical devices undergo a thorough cleaning and
visual inspection. This is done to remove contaminants.
The devices are sorted and grouped based
on their material composition and intended function.
Packaging Requirements:
Devices to be sterilized are packaged in materials which allow gamma rays to penetrate while
maintaining the seal of sterility of the contents.
This packaging must be sound in order to
withstand the sterilization process. Iradiation is conducted without compromising the integrity of the
medical devices.
Irradiation Process and Dosimetry:
Packaged devices
are deposited in a sterilization chamber, where the medical devices are exposed to gamma rays produced
by the deterioration of Cobalt-60. Dosimetry is the measurement of the radiation dose received during
the sterilizations process. It is vital to ensure the appropriate dose of radiation is administered to
achieve required sterility assurance. This process is controlled to ensure uniform exposure.
Post-irradiation Handling:
Gamma ray sterilization machine helps to remove devices from the radiation chamber.
Devices undergo further inspection to ensure each packaging remains intact and sterile. The sterilized
products are then labeled and prepared for distribution.
References:
https://link.springer.com/article/10.2478/s11535-014-0332-z
https://www.sciencedirect.com/science/article/pii/S109727650080129X
https://www.sciencedirect.com/science/article/pii/S0969806X23001603
https://www.sciencedirect.com/science/article/abs/pii/S092187770100091X
https://www.cdc.gov/infection-control/hcp/disinfection-sterilization/other-sterilization-methods.html
https://ebeammachine.com/how-the-use-of-gamma-rays-to-sterilize-medical-instruments-supports-mass-production
https://www.mddionline.com/sterilization/gamma-irradiation-a-sustainable-future-for-medical-device-sterilization
