The primary purpose of a Biological Safety Cabinet is to serve as the primary means to protect the laboratory worker and the surrounding environment from pathogens. All exhaust air is HEPA-filtered as it exits the biosafety cabinet, removing harmful bacteria and viruses. This is in contrast to a laminar flow clean bench, which blows unfiltered exhaust air towards the user and is not safe for work with pathogenic agents. Neither are most Biological Safety Cabinets safe for use as fume hoods. Likewise, a fume hood fails to provide the environmental protection that HEPA filtration in a Biological Safety Cabinet would provide. However, most classes of Biological Safety Cabinets have a secondary purpose to maintain the sterility of materials inside.
A laminar flow cabinet or laminar flow closet or tissue culture hood is a carefully enclosed bench designed to prevent contamination of semiconductor wafers, biological samples, or any particle sensitive device. Air is drawn through a HEPA filter and blown in a very smooth, laminar flow towards the user. The cabinet is usually made of stainless steel with no gaps or joints where spores might collect.
Laminar flow, sometimes known as streamline flow, occurs when a fluid flows in parallel layers, with no disruption between the layers.
In biology, an incubator is a device used to grow and maintain microbiological cultures or cell cultures. The incubator maintains optimal temperature, humidity and other conditions such as the carbon dioxide (CO2) and oxygen content of the atmosphere inside. Incubators are essential for a lot of experimental work in cell biology, microbiology and molecular biology and are used to culture both bacterial as well as eukaryotic cells.
An autoclave is a device used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents.
Culture Media is a liquid or gelatinous substance containing nutrients in which microorganisms or tissues are cultivated for scientific purposes.
Tissue culture is the growth of tissues or cells separate from the organism. This is typically facilitated via use of a liquid, semi-solid, or solid growth medium, such as broth or agar. Tissue culture commonly refers to the culture of animal cells and tissues, while the more specific term plant tissue culture is being named for the plants.
Reverse Osmosis (RO) is the most economical method of removing up to 99% of your feed water’s contaminants. It is a percentage rejection technology. The resulting product water is therefore dependent on the quality of the incoming water. Osmotic pressure is a colligative property driven by chemical potential. During natural osmosis, water flows from a less concentrated solution through a semi-permeable membrane to a more concentrated solution until concentration and pressure on both sides of the membrane are equal. In reverse osmosis, external pressure is applied to feed water to reverse the natural osmotic flow. Pure water passes through the membrane removing up to 99% of contaminants that are directed to drain (the concentrate). The purified water passing through the membrane is referred to as the permeate. This is collected in a reservoir and can be further processed. RO removes particles larger than 0.1 nm to produce a permeate of higher purity than ultra-filtered water. The pores in an RO membrane can be 0.0001 micron or 500,000 times smaller than the diameter of a human hair. In RO membranes, a layer of asymmetric membrane or an interfacial polymerized layer within a thin-film-composite membrane provides a particularly dense layer within the matrix where separation of ionic solutes occurs under pressure. Unlike membrane filtration which relies on size exclusion and can theoretically achieve perfect efficiency, RO also involves diffusion and is therefore dependent on pressure, flow rate and temperature. Most RO systems will need a reservoir to store the purified water as the flow rate is usually less than the peak demand.
Deionisation uses synthetic ion-exchange resins to chemically remove ions from feed water. As the water passes through the ion exchange resin beads, hydrogen and hydroxide ions are chemically exchanged with dissolved minerals to form water. Deionisation resin beds or columns are made from cation-exchange resins and anion-exchange resins either in separate beds or packaged together. Different technologies are referred to as co-current, counter-current and mixed bed. Most commercial resins are made of polystyrene sulphonate and oppositely charged ion exchanging sites are introduced after polymerisation. Cation-exchange media use sulphonic acid groups to exchange a hydrogen ion for any cations they encounter (e.g. Na+, Ca++, Al+++) and anion-exchange resins use quaternary amino groups such as polyAPTAC to exchange a hydroxyl for any anions (e.g. Cl-, NO3 - , SO4 -- ). When the hydrogen ion from the cation exchanger unites with the hydroxyl ion of the anion exchanger pure water is formed. Once all of the ion exchange sites on the resin have been filled by contaminants in the water, the resin will become exhausted. Resins may be regenerated by chemically rinsing in strong acids and bases to recharge the beads. Regeneration may be carried out when large cylinders of resin are used in industrial applications. In laboratory water systems, cartridges are discarded once exhausted. Choosing a water system with high capacity, longer lasting deionisation packs will impact greatly on running costs. Deionisation is the only technology which produces the resistivity requirement for Type 1 ultrapure reagent grade water. The electrical resistivity of ultrapure water is 18.2 M‑-cm. This low conductivity can only be achieved with water dissociation equilibrium which requires the production of H+ and OH− ions in the presence of dissolved monatomic gases.
Electrodeionisation (EDI) is a technology that combines electrodialysis and ion exchange. Water is pushed through one of two cells, each with an anion-permeable membrane on one side and a cation-permeable membrane on the other. The chambers contain loosely packed ion exchange resin. The ions will be attracted to the oppositely charged electrode and are flushed away before they reach it, effectively removing them from the water.
Typical UV disinfection systems involve the flow of water through a vessel containing a UV lamp. As the water passes through, microorganisms are exposed to intense ultraviolet light energy which causes damage to genetic molecules (i.e. nucleic acids: DNA or RNA) needed for reproductive functions. This damage prevents the microorganism from multiplying or replicating in a human or animal host. Because the microorganism cannot multiply, no infection can occur. Disinfection of water is achieved when UV light causes microbial inactivation.
Typical Utrafiltration is used to remove pyrogens (bacterial endotoxins) and nucleases. This process is critical when producing water for use in tissue or cell culture and media preparation. Ultrafilters use size exclusion to remove particles and macromolecules. The filter may also be charged to help attract contaminants. Particles are captured on the surface of the membrane and flushed to drain via a reject stream. Ultrafilters are usually employed at the end of the system to ensure near total removal of macromolecular impurities like pyrogens, nucleases and particulates.