Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Reexamination Certificate
1998-12-04
2002-10-15
Till, Terrence R. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
C422S020000, C422S021000, C422S024000, C422S044000, C422S046000, C250S438000, C250S455110
Reexamination Certificate
active
06464936
ABSTRACT:
The present invention relates to the treatment of biological fluids, especially body fluids, and fractions thereof to inactivate selected components, e.g. lymphocytes, and microorganisms, including viruses and the like, in human blood and in particular to a device suitable for use in such a procedure.
Large amounts of body fluids such as blood and plasma and various fractions thereof are used in the treatment of patients suffering from a variety of conditions. Contamination of such fluids with various viruses and other microorganisms; however, can give rise to serious new conditions in the patients receiving these fluids and may even result in their death.
Although it has been known for some time that ultra-violet (UV) irradiation can inactivate lymphocytes and viruses, this was not a practical procedure because of the very low UV transmissibility of blood and hence the difficulty of ensuring a complete irradiation and inactivation. More recently we have considerably reduced this problem in our Patent No. GB 2200020 with the use of static mixers which provided a very thorough mixing of the fluid during irradiation thereby permitting a substantially even irradiation of the whole of the fluid.
We have now found, that fluids containing fibrinogen are susceptible to activation and formation of more or less large particles of polymeric fibrin. Such particles can moreover form around viruses and other microorganisms and thus screen them from the UV radiation thereby preventing inactivation thereof, and thus seriously risking the health of the recipient of the treated fluid. This fibrinogen activation can be readily triggered by mechanical stress e.g. shear forces present in mixing and by heat which can readily occur locally during irradiation. Insoluble particles of material can also be formed by thermal and/or mechanical denaturation of other proteinaceous components.
Such problems also arise with conventional sterilization of human blood products which generally involves incubation thereof at a temperature of the order of 78° C. for an extended period of time of perhaps 48 to 72 hours. This procedure further has the disadvantages of being relative time consuming and occupying substantial amounts of relatively large scale apparatus and may result in substantial loss of potency.
It is an object of the present invention to avoid or minimize one or more of the above disadvantages.
We have now found that by carefully controlling the temperature of the fluid and preventing any localized heating thereof, formation of particles which can screen viruses and other microorganisms from inactivating radiation, can be substantially prevented.
In one aspect the present invention provides a device suitable for use in use in the sterilization of a fluid, which is a biological fluid or a fraction thereof, containing lymphocytes and/or micro-organisms, which device comprises a vessel having an inlet and an outlet and a passage means extending substantially directly and non-tortuously therebetween, said passage means having a heat exchange device with a heat exchange surface in substantially direct thermal contact with the interior of the passage means, and a temperature control means formed and arranged for maintaining the temperature of fluid in the passage below a temperature at which fluid components may form insoluble particles during irradiation, and said passage means having wall means substantially transparent to a lymphocyte and/or microorganism inactivating radiation, said passage means containing a static mixer device formed and arranged for thoroughly mixing the fluid in use of the device, so as to bring substantially the whole of the fluid into an irradiation zone extending along and in substantially direct proximity to said wall means during passage between said inlet and said outlet and into contact with said heat exchange surface, whereby in use of the device substantially the whole of a body of said fluid passed through said vessel may be exposed to a similar substantial level of irradiation whilst maintaining it at a safe temperature.
Thus with a device of the present invention a particularly uniform treatment of the fluid with respect to both irradiation and temperature thereof may be achieved thereby avoiding on the one hand under-exposure to inactivating radiation whether as a result of screening by an excessive depth of soluble fluid components or by enveloping insoluble material formed by more or less direct thermal denaturation of fluid components or as a result of thermally and/or mechanically triggered reactions (such as fibrinogen activation), as well as avoiding localized overheating induced by the irradiation which can result in reduced inactivation and/or increased degradation, thereby on the one hand maximizing inactivation of lymphocytes (where required) and/or undesirable microorganisms and on the other hand minimizing denaturation and degradation of useful fluid components.
It will be appreciated that various forms of heat exchange device may be used including solid state devices such as Peltier effect devices. Conveniently though there is used a heat exchange device wherein is circulated a heat exchange fluid (e.g. gas, liquid, or liquid mixed with gas and/or frozen liquid) as this generally facilitates more precise control of the biological fluid temperature.
Conveniently there is used an annular form of vessel with an outer wall substantially transparent to lymphocyte and/or microorganism inactivating radiation and an inner wall constituting said heat exchange surface, the latter preferably being of a generally inert physiologically compatible material with high thermal conductivity e.g. stainless steel. Any suitable heat exchange fluid may be used e.g. water. Where a heat exchange fluid is used then the temperature of this may be controlled in various ways remotely from said heat exchange surface in the vessel e.g. using a solid state heat exchanger such as a Peltier-effect heat pump or a refrigeration coil etc.
Various forms of temperature control means may be used. In general there is used a variable rate cooling device provided with a controller for varying the cooling rate according to an input from a temperature sensor means disposed in thermal connection with at least one of the fluid passage means, the heat exchange surface, and a heat exchange fluid passage in said heat exchange device.
It will be appreciated that the “safe” temperature limits for avoiding denaturation and/or other thermally triggered reaction may vary from one biological fluid or fraction thereof to another, and also depending on the application of the fluid, and conveniently there is used a temperature control means which allows for the fluid temperature to be maintained at a plurality of different values as required. In general for any body fluids containing fibrinogen the temperature is desirably maintained at not more than 37° C., preferably from −5 to 37° C., advantageously from −5 to 19° C.
In a preferred aspect of the invention the device includes at least one microorganism inactivating radiation source mounted in more or less closely spaced proximity to said transparent wall means (for the avoidance of doubt it should be noted that references to the transparent wall means merely indicates substantial transmission of the inactivating radiation which may or may not be accompanied by significant transparency at other wavelengths e.g. visible light). The mounting of the radiation source is generally arranged to minimize undesired heating of the transparent wall means and biological fluid in contact therewith whilst maximizing the radiation intensity in the irradiation zone. Depending on the source used this generally positioned at from 1.5 to 5 mm from the transparent wall.
Various lymphocyte and/or microorganism inactivating radiations may be used, though UV is generally preferred, especially UV radiation having a wavelength range from 100 to 400 nm preferably from 200 to 350 nm, for example UVA at approximately 320 to 500 nm. UVB at approximately 310 nm and UVC at appr
Cameron Ian David
Gunn Andrew
Mowat David McIvor
Alston & Bird LLP
Iatros Limited
Soubra Imad
Till Terrence R.
LandOfFree
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