How to validate isolators used for sterile product manufacturing
What are isolators?
Isolators are self-contained devices that perform automated functions and provide controlled environments with little to no microorganism exposure. These isolators remove the need for human contact and are made of surfaces that can be easily decontaminated, like plastics, glass, and stainless steel. Most sterility testing that follows United States Pharmacopeia (USP) guidelines utilizes isolators. HEPA air filtration is used in isolator systems. Air filtration systems are quickly decontaminated using sterilization-in-place decontamination processes. Sterilization-in-place processes decontaminate other isolator surfaces with steam and chemical treatments to prevent microbial growth. Isolator systems are either “open” or “closed.” Closed isolators do not have a direct opening to the external environment. Instead, closed isolators use rapid-transfer ports to move materials in and out of the closed system. In contrast, open isolators allow materials to enter the isolator chamber through a defined opening protected with air overpressure. Regardless of the isolator type (i.e., open or closed), materials entering or leaving isolators are transported aseptically. As isolators eliminate direct contact between human operators and products, any aseptic manipulations within the isolator are made with half-suits. Half-suits are glove and sleeves systems that allow the operator to manipulate items within the isolator.
How are isolator systems validated?
Every isolator must be validated before use in product testing, manufacturing, filling, or packaging. Isolator validations have three phases: installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ). Each validation phase builds off the other.
Isolator Installation Qualification (IQ) Evalution
The first validation phase is the IQ phase. Installations cover the physical components of an isolator system, e.g., system dimensions, internal layout, construction materials, and transfer systems. All isolator elements are evaluated during IQ, including air supply, vacuum, external exhaust, temperature controls, and humidity controls. During IQ, equipment manuals, process drawings, and instrumentation diagrams are cataloged and stored. IQ serves as an initial quality benchmark for isolator system performance. Further, initial process-control or equipment problems are identified and documented during IQ failure-mode and hazard analyses. All IQ data are summarized in a final IQ report. Isolator IQ evaluations for equipment, construction materials, instruments, utility specifications, filters certifications, and computer software are detailed below.
Equipment
During IQ, all isolator equipment is listed. Each listed item is checked for its design specifications, followed by professional installation.
Construction Materials
All isolator construction materials are checked for compatibility and compliance with decontamination method design.
Instruments
For IQ, all isolator instruments are listed with their calibration status and calibration dates.
Utility Specifications
All utilities, e.g., electricity and water, are checked for installation and compliance with design specifications.
Filter Certifications
HEPA and microbial retentive filters are installed, tested, and certified. Test results and certificates are provided in the final IQ report.
Computer Software
Isolator computer software is installed and listed with its name, size, and file revision number. Backup master computer disks are stored securely.
Isolator Operational Qualification (OQ) Evaluation
Operational qualifications ensure that the isolator system operates appropriately. The OQ process for isolators involves an operational performance check, isolator integrity check, and decontamination cycle verification.
Operational Performance Check
Operational performance evaluates isolator alert and alarm functions, setpoints, and adjustable parameters.
Isolator Integrity Check
A leak test is performed to verify isolator system integrity. Air pressure setpoints must be validated during leak testing to ensure that positive pressure gradients are maintained during normal isolator operation.
Decontamination Cycle Verification
One of the most critical features of an isolator is its ability to decontaminate itself. Note that any transfer isolators linked to the main isolator also undergo decontamination cycle verification during OQ. During OQ, verification that the decontamination cycle performs seamlessly with the isolator’s other functions is confirmed. Multiple sterilization methods can be used to kill microbes and decontaminate isolators. Vapor chemicals like peracetic acid, hydrogen peroxide, and chlorine dioxide are common in conjunction with the use of steam. For cycles involving humidity, relative humidity control must be verified during OQ. Additionally, the concentration and distribution of decontamination chemicals are verified using chemical indicators, spectroscopic methods, or electronic sensors. Gas and vapor sterilization methods use fans or unidirectional airflow systems to distribute the chemical through the isolator evenly. OQ processes ensure that the location and orientation of these fans or airflow systems optimize air distribution. Once utilized, any decontamination agents are removed from the isolator and replaced with fresh air. This aeration process happens in an open or a closed loop. In an open loop, the gas is exhausted through a vent to the atmosphere. In contrast, the chemical agent is removed and destroyed (or deactivated) by the decontamination equipment in a closed-loop system. OQ processes evaluate the aeration systems for appropriate functions as part of decontamination cycle verification. OQ completes with a distribution check. In a distribution check, the isolator is fully loaded with equipment and supplies. Then the supply set-up is documented for optimal orientation and loading patterns into the isolator.
Performance Qualifications (PQ)
Performance qualifications check that the isolator system can repeatedly perform the desired manufacturing or testing functions and self-decontamination. Performance qualification data are archived after assessment and approval.
Cleaning Verification
Cleaning is of primary importance to clear out residual products during multiproduct testing. Isolator cleaning method, frequency, equipment, and materials are demonstrated and documented for PQ.
Decontamination Validation
When the OQ is completed, decontamination cycle development begins. Decontamination development establishes parameters for controlling and monitoring each decontamination process. Decontamination cycles are validated through various approaches, including bioburden, fractional cycle, and overkill methods. For a decontamination cycle to be validated, the decontamination methods must demonstrate a three-log reduction against biological indicators in three consecutive validation studies. These validation studies are verified by the fraction negative or total kill analysis methods. Total kill analysis studies require biological indicators (Bis) with a thousand spores per unit, while fraction negative studies have BIs with a population of one-hundred thousand spores or greater. Many BI’s are required to verify decontamination cycles for isolators heavily loaded with equipment and materials. Finally, each isolator is given a frequency for re-decontamination. Depending on the sterility maintenance protocols and amount of use, the re-decontamination frequency may be as short as a few days or as long as several weeks.
Summary
Overall, isolators are self-contained devices that perform automated functions and provide controlled environments with little to no microorganism exposure. Most sterility testing that follows United States Pharmacopeia (USP) guidelines utilizes isolators. Every isolator must be validated before use in product testing, manufacturing, filling, or packaging. Isolator validations have three phases: installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ). Each validation phase builds off each other, with the IQ phase being first and the PQ phase being last. All in all, when outsourcing regulatory testing, ensure you choose a contract testing organization that can support you with appropriate equipment for the sterility testing of your unique medical devices or products.
Ethide Labs is a contract testing organization specializing in Sterilization Validations and Sterility Testing. Ethide Labs also offers Microbiology Testing, Bioburden Testing, EO Residual Testing, Bacterial Endotoxin Testing, Cytotoxicity Testing, Environmental Monitoring & Package Integrity Testing services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility.
References
Michael J. Akers. Sterile Drug Products Formulation, Packaging, Manufacture, and Quality. Drugs and the Pharmaceutical Sciences. Informa Healthcare. 2010.
United States Pharmacopeial Convention. <1208> Sterility Testing—Validation Of Isolator Systems. Rockville, MD, USA. 2021. (USPC <1208>).
