Device for treatment of biological fluids

Details Device for treatment of biological fluids Device for treatment of biological fluids

2001-03-30

2003-07-01

Lankford, Jr., Leon B. (Department: 1651)

Chemistry: molecular biology and microbiology

Maintaining blood or sperm in a physiologically active state...

C422S024000, C422S186300, C356S426000, C356S427000

Reexamination Certificate

active

06586172

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a national phase filing based on PCT International Application No. PCT/GB99/03082 filed Oct. 4, 1999. This PCT application claims priority to Great Britain Application No. 9821342.4 filed Oct. 2, 1998. The above PCT application was published in the English language as WO 00/20045.
The present invention relates a method of and a device for the UV-irradiation of a biological fluid of high optical density such as those encountered in beverage industries including dairy, distilling and brewing, and water treatment industries including sewerage and purification and, especially to the inactivation micro-organisms and lymphocytes and the like, including viruses, moulds, yeasts and other similar organisms which may be found in human or non-human blood and products derived from blood, as well as various other body fluids such as, for example, milk from transgenic animals, and synthetic fluids manufactured for use as replacements for any such body fluids or components thereof.
Conventionally inactivation of lymphocytes in biological fluids is effected by administration of immune-suppressive drugs to the patient. However this procedure involves serious risks to the patient due to the various adverse and often severe side effects of such drugs. Whilst various procedures for extracorporeal treatment of blood have been previously proposed these do not produce complete inactivation of the lymphocyte population and/or employ apparatus which is relatively cumbersome, expensive and/or impractical to operate.
In the case of contaminating microorganisms such as bacteria and viruses, various treatments have been proposed including for example, extended incubation at high temperatures and microwave irradiation. These treatments are quite often slow (several hours to even days) and generally require relatively expensive apparatus as well as stringent safety precautions to be followed by the operators of the equipment.
It has been found by others that a combination of UV irradiation with the use of chemical additives for example a photosensitiser such as furocoumarins, which may be used to increase the effectiveness (represented as log
10
kill) of the irradiation process. Typical examples of processes of this type can be found in WO94/28120 (MARGOLIS-NUNNO) and WO95/32732 (PARKKINEN).
The addition of photosensitive chemicals such as furocoumarins to the biological fluid has been proposed in order to effect more efficient transfer of energy from the UV radiation source to the target micro-organisms, thereby killing or inactivating the micro-organism without the need for excessive dosages of radiation which can be damaging to the components of the biological fluid. In more detail microorganisms, viral and other contaminants of biological fluids can be photo-dynamically inactivated by the addition of photo-sensitisers to the fluid, which can then be irradiated. The photo-sensitiser can transfer the energy gain from the irradiation to the microorganism by means of, for example, an electron transfer reaction. A second mode of inactivation by photosensitive compounds (most commonly in the presence of nucleic acids) is where the photosensitive compound upon irradiation reacts with nucleic acid residues, typically guanine in DNA. This reaction inactivates the nucleic acid residue and therefore inactivates the microorganism.
The addition of chemicals to the biological fluid has, though, the disadvantage that the chemical and/or its breakdown product(s) are still present within the biological fluid after irradiation. This is generally undesirable in that the chemicals and/or their breakdown products are a source of contamination of the biological fluid. Additionally, the chemicals themselves can be relatively expensive and require the extra step of adding them to the biological fluid, which can be time consuming, and thereby costly in man hours and also introduces a potential source of error in efficient treatment of the biological fluid. To remove or inactivate the chemicals and/or their breakdown products it is necessary to provide one or more further steps in the treatment method and the apparatus thereof for treating the biological fluid, which has obvious cost implications.
The exposure of a biological fluid to UV irradiation can result in damage to various components of the biological fluid, for example enzymes and other functional proteins. Therefore, the UV irradiation source should not be too powerful nor may the fluid be exposed to said UV radiation for too long, if one is to avoid damaging the components of fluid.
To ensure that substantially all of the fluid receives a sufficient dose of radiation, it has been found that intensive mixing of the fluid to be treated during irradiation increases the efficiency of the irradiation process. A device provided with a highly efficient mixer is described in the Applicant's patent GB 2,200,020B. The device of GB 2,200,020B describes a device which inter alia has a static flow mixing means which in use of the device repeatedly divides and mixes the biological fluid as it is irradiated. The principal device of GB 2,200,020B has a plurality of narrow bore (≦2 mm) passageways (see page 5, lines 16 to 19) through which biological fluid flows in use of the device. These narrow passageways ensure that the biological fluid receives an adequate dosage of UV radiation by passing the biological fluid close (i.e. at a distance of less than 1 mm) to UV transparent walls of the device. The biological fluid must pass close to the walls because of the relatively high absorption of UV radiation by many biological fluids, especially fluids with high OD such as blood as well as fluids which are substantially transparent but nevertheless have quite high OD, such as, for example, Human Serum Albumin (HSA) which has OD
280
of 24.5, plasma which typically has OD
280
of 50 to 60, and various immunogamma globulin (IgG) products which can have OD
280
values of 200 or more, which means that the radiation hardly penetrates at all into the body of the biological fluid. The intensity of the UV radiation at a given point in the biological fluid is proportional to the inverse square of the distance of the point from the source of the UV radiation. It is for this reason that the biological fluid, in use of the device described in GB 2,200,020B, is passed through narrow bore passageways. One limitation of a device such as the principal device of GB 2,200,020B is that as a result of passing through such narrow passageways, the biological fluid is susceptible to heat damage from the radiation source which heat(s) the walls of the device such that vital components of the biological fluid are damaged, for example proteins, red blood cells, etc. Heat damage is not desirable and is a limiting factor in the use of more powerful radiation sources and their proximity to the fluid to be treated. In order to reduce the heat-damage, the irradiation chamber of the device can be cooled, for example by air-cooling using a fan, as described in Example 1 of GB 2,200,020B. Nevertheless, as a result of the relatively low flow rates (e.g. 130 ml/min to 1200 ml/min), the biological fluid is in contact with or close proximity to the walls of the device for a relatively long time which results in correspondingly greater risk of heat damage.
Yet another problem that arises in this field is that in order to minimise heat damage and damage from excessive irradiation, it is desirable for the treatment time or residence time in the irradiation zone to be minimised. On the other hand if the residence time is too short, then a safe level of virus inactivation or log kill may not be achieved. Inactivation on a commercial scale can, however, involve treatment of relatively large volumes e.g. hundreds or thousands of liters of precious and scarce materials such as albumin, IgG, plasma and the like, and it is extremely expensive and wasteful of such precious and scarce materials to carry out optimisation of the considerable number of various diffe

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