Apparatus sterilization

Fig. 1.2 Pasteur s apparatus if the oven is not switched on, the microorganisms in the air enter the sterile culture solution and multiply. If the oven is switched on, they are killed by the heat. After Conaut (1953)...

Fig. S.—Emil Fischer s fermentations on a semi-micro scale using an apparatus of the size shown, (a) —70 mg sugar, 0.35 ml water, 0.35 ml sterilized yeast extract, and 13 mg yeast species (b) S-trap for evolved C02 (c) aqueous barium hydroxide.

One factor in the reduction of healthcare expenditure is home medical care, which involves adaptations of the methods of care. These uses dictate particular requirements for sterility, safety, reliability, weight and facility of use. Plastics can bring solutions in the fields of single-use products, unbreakable equipment and weight reduction, for example, in the syringes, tubes and pumps for drug injections and apparatus for ambulatory dialysis. 

Sterile Spinner flasks (200 ml and 1 litre), spinner apparatus... 

Aseptically prepared collection plates are placed in the sampling apparatus. Petri dishes used must be sterilized prior to filling. Verify the adequacy of petri dish dimensions so that the operational characteristics are maintained according to the manufacturers specifications. Plastic petri dishes are not recommended because static changes are likely to be present in plastic that will reduce the collection efficiency. 

How must the filtering apparatus be sterilized to carry out the aseptic processing effectively ... 

Figure 7.5 Apparatus for testing the microbial retention characteristics of membrane filters. The whole apparatus is sterilized, and initially the flask contains 140 mL of double-strength culture medium. The culture to be tested (100 mL) is passed through the filter with clamp 1 open and clamp 2 closed. The sides of the filter apparatus are washed with two 20 mL portions of sterile broth. Clamp 2 is then opened, the vacuum released, and clamp 1 closed. The filter apparatus is replaced by a sterile rubber stopper and the flask incubated. Absence of turbidity in the flask indicates that the filter has retained the test organism. From Brock [4]. Courtesy of Thomas D. Brock...

The apparatus is re-usable and, although initially costly, does not require vast continuous expenditure. However, it puts the onus on the user to prepare the apparatus in a clean and sterile manner. 

A number of commercial machines are available and cuvettes may be bought or constructed from disposable spectrophotometer cuvettes into which aluminium electrodes are glued. They can be sterilised with 70% ethanol and then washed with sterile PBS. (This is also true for the disposable commercial cuvettes.) The same apparatus can also be used for cell fusion (electrofusion) (see 13.7.3 and Glassy, 1988). 

RNAs are denatured by formaldehyde/heat treatment. All of the stock solutions for RNA slot blots are made using sterile diethyl pyrocarbonate (DEPC)-treated water. RNAs are diluted as necessary from stock solutions with water, and 3 volumes of 6.15 Mformaldehyde in 10X standard saline citrate (SSC) is added to give a final RNA concentration of 10-100pg/ml. The RNA dilutions are heated to 65° for 15 min and quick-chilled on ice. The denatured stock is further diluted with 4.16 M formaldehyde in 7.5 X SSC such that the desired concentration of RNA may be applied to each slot in a total volume of 400 pi. The nylon membrane is piewet in water and then soaked in 10X SSC for 20 min. Slot blots are performed using a commercially available apparatus hooked to a vacuum source. After the samples are blotted through, each well is washed with 400 pi of 10 X SSC. The membrane is removed from the apparatus and baked in a vacuum oven at 80° for 2 hr. 

We can use the effects of radiation for good as well as evil. Radioactive isotopes of elements can be used in specific apparatus to focus their radiation on unwanted body material and cancerous cells. Often the gamma rays from the 60 isotope of cobalt (27C0) are used to produce these penetrating rays to kill cancer cells. This same isotope is also used to produce the gamma rays to sterilize medical instruments. It kills the germs but the instruments remain unaffected. 

Enzyme solution. Powdered invertase obtained from yeast is available from mai r biochemical supply houses, such as Sigma Chemical Co., P.O. Box 14508, St. Louis, MO 63178. A sterile solution of invertase must be prepared with great care. All apparatus used to make up this solution must be sterilized prior to use. More than 1 L of distilled water is boiled for 10 min, covered with aluminum foil, and chilled in an ice bath. Then add a precisely weighed amount of invertase (approx. 5-10 mg) to water in a 1-L volumetric flask and make up to the mark. The enzyme solution should be kept tightly stoppered and chilled at all times. The correct invertase concentration is very sensitive to the specific activity of the enzyme as purchased it is necessary to carry out the standard assay and adjust the solution to an appropriate final concentration. 

The syringe of the lacrimal irrigation apparatus is filled with sterile saline. 

Care has to be taken when switching the inlet tube through different solutions not to let air bubbles in. Best way is to switch off the pump, reset the flow and move the tube to the next solution. When more than one mouse is used, the perfusion apparatus has to be rinsed between mice with at least 100 ml of sterile GBSS. 

---