Apparatus and methods for culturing biological material

Abstract: A method of providing a substrate with a textured surface comprising the steps of forming a mobile surface studded with a granular material on the substrate, setting the mobile surface and removing the granular material to leave a textured surface on said substrate, and apparatus for use in culturing micro-biological material comprising a substrate produced by such a method.

Description: The present invention relates to vessels having textured surfaces for growing animal cells, plant cells, micro-organisms and the like ('bio-substances') and to methods for their production. Many bio-substances can be propagated in vitro in containers such as so-called 'roller bottles', that is, cylindrical vessels, usually of glass or polystyrene, which are partially filled with a liquid medium comprising the bio-substances. The bottles are arranged to be rotated slowly about their longitudinal axes, promoting aeration, while the liquid medium provides nutrients to the bio-substances as they grow on the inner surfaces of the container. Limitations in the efficiency of conventional procedures have hitherto been due to the relatively small surface area provided by the smooth interior of the container, as well as the fact that such surfaces do not provide optimum characteristics for the growth processes. It is an object of the present invention to eliminate or minimise these disadvantages. Accordingly, in a first aspect of the invention, there is provided apparatus for use in a method of culturing micro-biological material, wherein said apparatus has a rough or uneven growth surface with a plurality of craters or crater-like depressions defined in the inner surface of the apparatus per se or in a coating of an organic polymer formed on the inner surface of the apparatus and, arranged for contact with micro-biological material being cultured. An advantage of the inventive apparatus is that its use can allow cultured material to be grown at enhanced rates. Preferably, the growth surface is rendered rough or uneven by a plurality of craters or crater like depressions, preferably to depths of 1mm or less and more preferably to depths of 0.1-0.5 mm. Preferably, the craters or crater like depressions measure less than 2mm, and more preferably less than 1mm across. Most preferably, the crater or crater like depressions measure less than 0.5mm across. In further embodiments, the growth surface is micro-cupellated. The organic polymer coated on the inner surface of the apparatus is preferably a silicone rubber. In a second aspect, the invention provides a method of culturing a micro-biological material, comprising culturing said material using apparatus in accordance with its first aspect. Advantageously the inventive method allows biological material to be grown at an enhanced rate. In a third aspect, the invention provides a method of providing an apparatus with a rough or uneven growth surface for culturing microbiological material comprising the steps of forming a mobile surface studded with a granular material on a surface of the apparatus, setting the mobile surface and removing the granular material to leave a rough or uneven surface. In a fourth aspect of the invention, there is provided an article having a textured surface that can be obtained by a method according to the invention in its third aspect. Preferably, the article is a tissue or cell culture vessel, such as a roller-bottle. In all aspects of the invention the biological material preferably comprises tissue, cells or like matter, including viral particles or virions. In the invention according to its fourth aspect, the mobile surface is preferably tacky prior to the setting step, so as to promote adherence of the granular material. In a preferred embodiment, a (preferably solvent-less) silicone paint, designed for polymerisation to form silicone rubber, is applied to the interior surface of a glass or polystyrene roller bottle. While the coating is still in liquid form, common salt particles are injected into the container, for example, under pressure, to adhere to the prepared silicone coating, with any excess salt being removed again from the container. The coating is then allowed to polymerise into a solid layer at ambient or elevated temperature, depending on the type of silicone used. When hardened, the salt particles adhering to the coating are removed by dissolution in water, to leave a surface-porous layer exhibiting a cratered or micro-cupellated structure, as well as the special affinity for bio-substances of silicone rubber. The container so prepared is found to result in a greatly increased yield when used for growth processes in the manner described. To promote adhesion of the silicone rubber layer within a glass or polystyrene container, a conventional adhesive, preferably a mineral spirit based primer, can be first applied to the surface prior to deposition of the silicone layer. In embodiments of the invention, it is a pre-requisite that the growth surface should be non-toxic and inert in respect of bio-substances and liquid media. The method of creating such surfaces should not involve any materials, which if remaining on the surface as impurities, could have a deleterious effect on the growth process. In the above described method, various types of particles can be used in place of common salt, such as, for example, sugar, saltpetre and the like; however, common salt, sucrose or potassium nitrate are preferred as being non-toxic and inert in respect of normal media and bio-substances, as well as being soluble in water for subsequent removal. Solubility of the particles in a non-toxic solvent is an important factor in their choice. Attempts have been made to use 'open-porous' silicone rubbers, such as the material 'Immobasil' ('Immobasil' is a registered trade mark); however, the results obtained were not as satisfactory as those achievable using the various aspects of the present invention. The open-porous structure (that is, the presence of inter-connected pores within the body of the silicone rubber) in such known materials leads to difficulties in the subsequent harvesting of the biosubstances from the interstices of the coating on completion of a growth cycle. In an embodiment of the invention, surface pitting or cratering, for example, micro-cupels, can be produced in the inner surfaces of glass or polystyrene containers per se . For this purpose, salt or other suitable particles are injected, for example, pneumatically, into the container while the latter is at elevated temperature, either during its manufacture or on subsequent heating. Upon cooling, the particles are then removed as described above, leaving the interior surface of the glass or polystyrene container with a textured, cratered or micro-cupellated structure, again resulting in enhanced efficiency of the process. In the case of polystyrene containers, prior to use, the standard procedure of plasma treatment of the inner surface can be applied to impart a negative electrical charge to the surface, as required for the growth process. Other types of particle can be used apart from salt, the latter however, being again preferred for the reasons enumerated. It is evident that other methods lying within the ambit of the invention may also be used to derive surface porous, cratered or micro-cupellated textured surfaces of the nature described for growing of bio-substances. The invention can equally be applied to all suitable containers, such as, for example, flasks, tubes, trays, roller bottles, plastic bags and the like. In applications where very large area growth surfaces are required, it is conventional to utilise containers which comprise flat plates, for example, of polystyrene, wetted by the liquid medium, and upon which the bio-substances are made to grow. Such plates can also be provided with coatings of silicone rubber having a cratered or micro-cupellated, porous, surface structure according to the invention, in the manner described above, to result in substantially enhanced productivity. Thus, roller bottles and other containers according to the invention can have a specially textured, cratered or micro-cupellated growth surface, usually an inner surface, suitable for use in the growth of bio-substances as aforesaid. By their nature, these surfaces are more conducive to the adhesion and growth of bio-substances, with resulting improved process efficiency. It is considered that the larger surface areas provided by such growth surfaces is a factor in their enhanced performance. In order that the invention may be better understood, an example thereof will now be described by way of illustration only and with reference to the accompanying drawings, wherein: Figure 1 is a schematic front perspective view of a conventional roller bottle; Figure 2 is a schematic side cross-sectional view of the roller bottle of Figure 1 along the line AA' after partial treatment by the inventive method; Figure 3 is a schematic side cross-sectional view of the roller bottle of Figure 2 after treatment by the inventive method has been completed; and Figure 4 is a schematic scrap view from a point on the axis of the roller bottle showing a portion of the growth surface after treatment by the inventive method has been completed. With reference to Figures 1 to 4, a polystyrene roller bottle 1 is provided with a cratered or micro-cupellated surface according to the inventive method as follows. To the interior surface of bottle 1, a coating 2 of silicone rubber primer SS 4155 (General Electric Co., Connecticut, U.S.A.) is applied by brushing or other means and allowed to dry at 70°C for 15 minutes. A coating 3 of silicone rubber paint RTV 118 (General Electric Co., Connecticut, U.S.A.), approximately 0.05 to 0.2mm in thickness, is applied to primer coating 2 and left to stand for 1 minute. A substantial quantity of common salt 4 is then introduced into bottle 1 until approximately 1/3 full and the latter shaken, so that salt 4 adheres to all of the paint coating 3. The excess salt 4 is removed and coating 3 allowed to cure at 70°C for 30 mins. Bottle 1 is then filled with boiling water and allowed to stand for 10 minutes before the water is removed. This last step is repeated once before bottle 1 is rinsed with isopropyl alcohol and left to dry at 70°C for 30 mins. The resultant roller bottle 1 has a textured interior surface 5 provided by craters or micro-cupels 6 inset in silicone rubber layer 4. The roller bottle 1 can then be inoculated with a biological material, for example cells taken from a commercially available cell line such as Madin Darby Canine Kidney, suspended in an appropriate commercially available nutrient medium, such as Glucose Minimum Essential Medium containing 5% foetal calf serum, selected for its suitability for growing the chosen cells. The roller bottle can then be placed upon conventional equipment designed to gently roll the bottle under conditions conducive to growing cells from the selected line. For example, a common culturing temperature is 37°C. After an appropriate culturing period, the growing cells can be harvested from the roller bottle using conventional techniques, such as trypsination or mechanical scraping.

Claims: Apparatus for use in a method of culturing micro-biological material, wherein said apparatus has a rough or uneven growth surface with a plurality of craters or crater-like depressions defined in the inner surface of the apparatus per se or in a coating of an organic polymer formed on the inner surface of the apparatus, and arranged for contact with micro-biological material being cultured. Apparatus as claimed in claim 1, wherein the organic polymer is a silicone rubber. Apparatus as claimed in either of the preceding claims, wherein the crater or crater-like depressions have a depth of 1mm or less and, preferably, a depth of 0.1-0.5mm. Apparatus as claimed in any of the preceding claims, wherein the craters or crater-like depressions measure less than 2mm, preferably less than 1mm, and more preferably less than 0.5mm across. Apparatus as claimed in any of the preceding claims, wherein the growth surface is micro-cupellated. A method of culturing a micro-biological material, comprising culturing said material using apparatus as claimed in any one of the preceding claims, wherein said material is in contact with the rough or uneven growth surface. A method of providing an apparatus with a rough or uneven growth surface for culturing microbiological material, comprising forming a mobile layer studded with a granular material on a surface of the apparatus, setting the mobile layer and removing the granular material to leave a rough or uneven surface. A method as claimed in claim 7, wherein the mobile layer is tacky prior to setting. A method as claimed in claim 7 or 8, wherein the mobile surface is formed by softening the material of the apparatus and studding the softened material with granular material. A method as claimed in claims 7 or 8, wherein the mobile layer is formed by coating the inner surface of the apparatus with a layer of a surface-forming organic polymer and studding said layer with a granular material. A method as claimed in claims 7 or 8, wherein the mobile layer is formed by coating the inner surface of the apparatus with a layer of a surface-forming organic polymer in admixture with a granular material. A method as claimed in claims 10 or 11, wherein the surface-forming organic polymer is a silicone rubber-forming material. A method as claimed in claims 10, 11 or 12, wherein the inner surface of the apparatus is treated with an adhesive prior to coating with the layer of surface-forming organic polymer. A method as claimed in any one of claims 7-13, wherein the apparatus is made of glass or an organic polymer. A method as claimed in any one of claims 7-14, wherein the granular material is soluble and is removed by dissolution. A method as claimed in claim 15, wherein the granular material is sucrose, salt or potassium nitrate. A method as claimed in any one of claims 7-16, wherein the rough or uneven growth surface is cratered or micro-cupellated. An apparatus for use in culturing microbiological material obtainable by a method as claimed in any one of claims 7-17.

Inventors: FULLER JESS PAUL, FULLER, JESS PAUL
Applicants: ASHBY SCIENT LTD, ASHBY SCIENTIFIC LTD.
Application year: 1996
Main classification: C12M1
IPC codes: C12M1