Tips for Aseptic Technique in the Laboratory – Biosafety Cabinets (Part 4 of 4)

Cara N. Wilder, Ph.D.

When working with hazardous or sterile materials, it is recommended that all associated procedures are performed in a biosafety cabinet. These apparatuses are enclosed, ventilated workspaces designed to protect laboratory personnel and materials from cross contamination during routine procedures. Generally, work spaces within the biosafety cabinet are protected through the use of a high-efficiency particulate air (HEPA) filtration method, which removes harmful microbes from the air.

There are three types of biological safety cabinets: Class I, Class II, and Class III.

Class I: These biological safety cabinets are open-front negative pressure systems with HEPA filtration systems. These biosafety cabinets provide protection for laboratory personnel and the environment, but will not provide product protection. These cabinets are often used to enclose specific equipment or procedures that may generate potentially hazardous aerosols.

Class II: These biological safety cabinets are open-front, ventilated, laminar-flow cabinets. These provide HEPA-filtered, recirculated airflow within the work space. Class II cabinets provide protection to laboratory personnel, the environment, and to products by drawing a curtain of sterile air over the products that are being handled. These cabinets are commonly used in microbiology laboratories working with non-infectious agents (Biosafety Level 1 or 2) as they protect the contained materials from extraneous airborne contaminants.

Class III: These biological safety cabinets are totally enclosed, ventilated systems with gas-tight construction. These cabinets are used through attached rubber gloves. Generally, the air supply is drawn into the cabinet through HEPA filters, and the exhaust air is filtered by two HEPA filters installed in a series. This biosafety cabinet system is commonly used with high-risk infectious agents (Biosafety Level 3, 4, or 5) to prevent the escape of aerosols.

Below, we describe some tips on how to properly use a Class I or Class II biosafety cabinet when working with non-infectious materials.

Keeping a Biosafety Cabinet Safe

·         Certify all biosafety cabinets upon installation

·         Routinely test the quality of airflow

·         Ensure the integrity of filters

·         Biosafety cabinets should be approved by the resident Biosafety officer

·         Ensure that all biosafety cabinets are routinely recertified

Biosafety Cabinet Sanitation

·         Clean work surfaces with 70% ethanol before and after use. When using 70% ethanol, ensure that there are no open flames nearby.

·         If the biosafety cabinet is equipped with germicidal UV lights, decontaminate work surfaces before and after use by turning on the UV light for at least 15 minutes. Never use the UV light while the biosafety cabinet is in use.

·         Routinely remove any biohazard waste from the biosafety cabinet.

·         Using an appropriate disinfectant, such as 70 % ethanol, wipe down the outer surface of all pipettes, pipette tip boxes, media, materials, etc. prior to placing them in the biosafety cabinet.

·         Always wear a clean lab coat and sterile gloves when working in a biosafety cabinet.

Proper use of a Biosafety Cabinet

·         Turn on the biosafety cabinet 15 minutes prior to use.

·         Only raise the biosafety cabinet sash to the recommended level, this will reduce disruption to the air flow as well as assist in the prevention of airborne contaminant entry.

·         When using a biosafety cabinet, limit the amount of movement in the cabinet and do not remove your arms. Additionally, limit the access to the area around the biosafety cabinet. This will reduce disruption to the airflow.

·         Do not use open flames within a biosafety cabinet. The resulting heat from the flame can disrupt the air flow provided by the biosafety cabinet, increasing the risk for contamination. Additionally, gas leaks associated with Bunsen burners or the use of an alcohol-based disinfectant near an open flame can result in fire or injury.

Stay clean, and happy culturing!

Using the pathogenic prowess of viruses to benefit the medical field

Cara N. Wilder, Ph.D.

For over a century, viruses have captivated scientific minds. These agents of destruction are often considered the border between biochemistry and biology, not truly alive in the classical sense nor are they unorganized amalgamations of protein and DNA. In actuality, viruses are metabolically inert, ultramicroscopic organisms with the inherent ability to cause disease by invading host cells and hijacking replicative machinery. It is this natural infection process that not only fascinates contemporary scientists but has allowed them to develop exciting viral-based technologies, including novel drug delivery methods and vectored vaccines, for the advancement of disease treatment and prevention.

When creating viral nanoparticles, the genomic material is
removed from the viral head and replaced with drugs.
Photo: CDC/ Doug Jordan

Viral nanoparticles are viruses whose genomic material has been removed and replaced with therapeutic drugs. Because viruses have naturally evolved the ability to cross the host membrane, they are an ideal candidate for drug packaging and the targeted delivery to cancer cells. To minimize toxic side effects, infection, and induced immune response, human viruses are not used in the production of viral nanoparticles. Rather, these drug delivery systems are engineered from plant, insect, and animal viruses. Plant viruses, such as the Cowpea mosaic virus, are ideal candidates for nanotechnology as they are easy to produce in large quantities, can self-assemble around a nanoparticle, and hold a substantial volume of drugs.

One of the major benefits to using viral nanoparticles for drug delivery is that targeting molecules can be easily attached to the viral surface, allowing for the directed binding to cancer cells. This specific binding prevents the harm or death of surrounding healthy cells, thus reducing possible side effects. Though viral nanoparticles have the potential to be a beneficial treatment, there are several complications associated with their use as a drug delivery system including immune rejection and potential toxicity. Regardless, viral nanoparticles have the capability to revolutionize the treatment of disease, creating a safe and specific form of drug delivery.

In addition to functioning as a drug delivery method, viruses can also be employed as vectors for vaccines. Generally, vaccines are the most effective and inexpensive prophylactic tool for the prevention of disease. Viral-based vaccines are traditionally employed as live attenuated viruses or as chemically inactivated viruses. Though these types of preparations have been shown to induce protective immunity in animal models, mutations in attenuated viruses or incomplete viral inactivation poses a serious risk to those who are vaccinated. Recombinant vectored vaccines, however, offer a live-vaccine approach that does not employ the complete pathogen. Instead, genetic material from the microbial target strain is inserted into the genome of harmless viral strains, allowing for the safe expression of microbial antigens.

Vectored vaccines can constructed to protect against a
wide variety of microbial diseases.
Photo: CDC/ Doug Jordan

Newcastle disease virus (NDV), a negative-sense avian virus, is a common template used for the development of recombinant vectored vaccines. Not only does NDV grow to high titers in many cell lines and eggs, it can elicit a strong immune response in vivo, is harmless to humans, and is commercially available. Additionally, NDV replicates in the cytoplasm of infected cells, thus eliminating the problem of genetic integration. To create a viral vaccine vector from NDV, genes encoding foreign target proteins are inserted into the NDV genome through recombination. Upon vaccination with the live virus, the foreign target protein is expressed within the host cell cytoplasm where it is then available for processing by the cellular antigen-processing machinery for immune presentation. As a result, cellular immunity is activated and neutralizing antibodies are generated.

Overall, the ability of viruses to cause devastating epidemics has left them greatly feared by the human population. However, with contemporary technologies such as viral-based drug delivery systems and vectored vaccines, viruses can now be regarded as tools in disease treatment and prevention. Perhaps with further advancement in viral-based technologies and applications, scientists will be able to harness the full benefit of these organisms, improving life where there was once death.