MXPA00005123A - Preservation of sensitive biological samples by vitrification - Google Patents

Abstract

This invention discloses methods for the long-term preservation of industrial scale biological solutions and suspensions containing biologically active molecules, cells and small multicellular specimens at ambient temperatures by dehydration in amorphous very viscous liquid or glass state. The scale up method comprises the primary drying step of boiling under vacuum to form a mechanically-stable foam and a secondary drying step to increase the stability. Vitrification can subsequently be achieved by cooling the dried material to the storage temperature which is lower than the glass transition temperature.

Description

PRESERVATION OF SENSITIVE BIOLOGICAL SAMPLES THROUGH VITRIFICATION BACKGROUND OF THE INVENTION This invention relates to methods for preserving 'solutions and suspensions containing biologically active molecules, viruses (vaccines), cells and small multicellular specimens. More particularly, the invention relates to methods for the long-term storage of these biological materials labile at ambient temperatures in highly viscous, dehydrated amorphous liquid or glassy state. The preservation and storage of solutions or suspensions of biologically active materials, viruses, cells and small multicellular specimens is important for the food and microbiological industries and for agricultural, medical and research purposes. The storage of dehydrated biologically active materials brings enormous benefits. The dehydrated cells, materials and reagents have a low weight and require a small space for storage, despite their increased stability. Suggestions in the prior art for providing improved stability preparations of labile biological materials in dehydrated form include freeze drying and air or vacuum desiccation. Although freezing methods are scalable to industrial quantities, materials dried by such methods can not be stored at ambient temperatures for long periods of time. In addition, the freezing stage of lyophilization is very damaging to many sensitive biological materials. Alternatively, air and vacuum drying methods do not allow preparations of biological materials that are scalable to industrial quantities and stable for extended periods of time at ambient temperatures, because destructive chemical reactions can continue to proceed in such dried preparations. Some of the problems associated with preservation by freezing and drying have been addressed by the addition of protective molecules, especially carbohydrates, which have been found to stabilize biological materials against freezing and drying stresses. However, in spite of the presence of protectors, long-term stability may still require storage at low temperature, in order to inhibit diffusion-dependent chemical reactions. In this way, additional innovations have been sought to provide long-term storage of biological materials labile at ambient temperatures. Storage of dried materials at ambient temperatures would be cost effective when compared to low temperature storage options. In addition, storage at room temperature of biological materials such as vaccines and hormones would be extremely valuable in getting modern medical treatments to third world countries where refrigeration is often not available. As many preservation benefits on the shelves of biological specimens have been appreciated, researchers have sought to take advantage of protection as a means of protecting biological materials against degrading processes during their long-term storage. Consequently, this technology to achieve the "vitreous" state, has been anticipated to emerge as a main preservation technique for the future. The vitreous is an amorphous solid state that can be obtained by substantial subfusion of a material that was initially in the liquid state. The diffusion in vitrified or vitreous materials occurs at extremely low proportions (for example, microns / year). Consequently, chemical or biological changes that require the interaction of more than one residue are practically completely inhibited. The vitreous state normally appear as brittle, transparent, homogeneous solids, which can be ground or crushed into a powder. Above a temperature known as the vitreous transition temperature (Tg), the viscosity drops rapidly and the vitreous becomes deformable and the material becomes a fluid at even higher temperatures. The optimal benefits of long-term par-storage vitrification can only be ensured under conditions where the Tg is greater than the storage temperature. The Tg depends directly on the amount of water present and therefore can be modified by controlling the level of hydration; while less water greater Tg.

Unfortunately, the advantages of vitrification technology as a means to confer long-term stability to biological materials labile at ambient temperatures have not been fully utilized. The current methods of preservation at room temperature by drying are designed for laboratory processing of very small amounts of materials. Consequently, such methods are not compatible with large-scale commercial operations. Other technical problems related to vitreous transition temperature monitoring have also presented obstacles to commercial development. Thus, although drying and vitrification technologies are potentially attractive as scalable methods for the long-term storage of biological materials, there are problems to be overcome before the storage advantages in the glassy state can be exploited commercially. SUMMARY OF THE INVENTION A method is described for preserving industrial quantities of solutions and suspensions containing sensitive biological materials comprising, drying the samples by vacuum boiling in a temperature range of -15 ° C to 70 ° C. A mechanically stable foam is formed, consisting of thin amorphous films of concentrated solutes. Such foams will not dissolve for at least one hour at -20 ° C when stored under vacuum. To increase the stability, the foams can be further dried for at least 12 more hours under vacuum at temperatures ranging from 0 ° C to 100 ° C, where the drying temperature is higher than the desired storage temperature, selected within the range from 0 ° C to 70 ° C. To provide long-term preservation of suspensions and biological solutions in the vitreous state, mechanically stable foams can be subjected to secondary vacuum drying in the range of 0 ° C to 100 ° C for a sufficient period of time to increase the temperature of vitreous transition to a point above the selected storage temperature within the range of 0 ° C to 70 ° C. Finally, a composition for protecting cells and viruses during the aforementioned desiccation and vitrification processes is described, which comprises an unreduced monosaccharide, a disaccharide (such as sucrose) and a biological polymer.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents a DSC scan of a mixture of sucrose and raffinose (AyB) and Ficoll (CyD). Figure 2 is a graph that represents the relationship between the Tg and the dehydration time at three different temperatures. Figure 3 is a graph showing the survival of dry E.Coli as a function of storage time at room temperature. DETAILED DESCRIPTION OF THE INVENTION In attempting to develop vitrification as a means of preserving biological materials at ambient or higher temperatures, the Applicant discovered that certain theoretical limitations that underlie vitrification processes have not been fully appreciated. As a result, many vitrification methods claimed in the prior art incorporate technical defects that have obstructed or misplaced the efforts directed to take advantage of the advantages of vitrification in the industries, biomedical and pharmaceutical. There are several potential reasons for the defects in many vitrification methods of the prior art.

First, although the standard method for determining Tg, differential scanning calorimetry ("DSC"), is reliable for simple sugars and mixtures thereof, it is not reliable for solutions of polymeric substances, such as Ficoll and hydroxyethyl starch, which they are frequently used to stabilize biological samples. Indeed, the applicant recently presented evidence at the meeting of the Society of Cryobiology of 1997, that the changes in specific heat are very small (undetectable by DSC) in concentrated solutions of hydroxyethyl starch., which occur over a wide temperature range in dried samples. Consequently, for practical purposes, the phase change in polymeric materials is not detected by DSC. Figure 1 shows a comparison of DSC scans (conducted at 2 ° / min) for a mixture of sucrose and raffinose 1: 1 (left panels) after secondary drying for 5 days at room temperature (A) and 70 ° C (B) ) with those DSC results obtained for Ficoll (right panels), dried for 5 days at room temperature (C) and 70 ° C (D). The Tg for sucrose-raffinose was determined by reference to the point of inflection, which is clearly discernible. The Tg for sucrose-raffinose increased dramatically with the drying temperature from 1.86 ° C followed by drying at room temperature at 59.71 ° C followed by desiccation at 70 ° C. In contrast, there is no clearly discernable inflection point for Ficoll, shown in Figure 1 (CyD). In this way, the estimation of Tg by DSC in dehydrated biological samples in the presence of polymeric protectors, such as Ficoll, is not reliable. Another technical limitation in vitrification methods, which seems not to have been widely appreciated, is that dehydration is a process limited by the diffusion of water molecules. As the sample dries out, diffusion and consequent dehydration decrease as the sample becomes more viscous and virtually stop as the transition in the glassy state approaches. According to the above, additional dehydration is not possible. Similarly, since the Tg depends on the level of dehydration achieved, an additional increase in Tg is not possible. It is therefore technically impossible at constant hydrostatic pressure to achieve a Tg higher than the dehydration temperature. Consequently, the glassy state can only be introduced in the subsequent cooling. Thus, references in the prior art describing desiccation at X ° C to obtain a Tg greater than X ° C are impossible and are probably based on erroneous measurements of Tg by DSC. Although many methods of the prior art have appeared to achieve the glassy state at ambient storage temperatures (ie Tg >; 20 ° C-30 ° C), it is evident from the relatively short dehydration periods and low dehydration temperatures that such descriptions, in fact, incorporate defects in empirical methods and theoretical reasoning that avoid true vitrification. In the best case, these methods achieve a very viscous liquid state, but a vitreous state could never arise. To illustrate the inoperability of the methods of the prior art, Figure 2 represents the dependence of the Tg on secondary drying time at three different temperatures. The solutions (10 ul) of a mixture of sucrose and raffinose 1: 1 were initially dried under vacuum overnight at room temperature, followed by secondary drying at the indicated temperatures; Tg was determined by DSC, which is reliable for sugar mixtures. Because Ficoll is a sucrose polymer, it is reasonable to infer that the conditions required to raise Tg in sucrose would be similar in a Ficoll solution having an equivalent sucrose concentration. Clearly, the Tg is never higher than the drying temperature. For example, the secondary drying times must be greater than 12 hours, even at 70 ° C, in order that the Tg approaches the ambient temperature (Figure 2). Another technical limitation generally not appreciated, but of critical importance for the commercial exploitation of vitrification, is that the drying time is inversely proportional to the water diffusion coefficient and proportional to the square of the sample size. Consequently, dehydration of a 10 microliter drop of a sucrose-raffinose mixture at 70 ° C required more than 12 hours to achieve a Tg greater than 25 ° C (see Figure 2). However, it would take more than 55 hours for a 100 microliter sample and 258 hours for a 1 ml sample at 70 ° C to reach the same Tg. Similarly, dehydration of a 10 microliter sample of sucrose-raffinose at 50 ° C required more than 2 days to raise the Tg above room temperature. But it would take more than 9 days for a 100 microliter sample and 43 days for a 1 ml sample. In this way, limitations in the sample size have tended to impede the large-scale commercial development of vitrification technology. Among commercial attempts to take advantage of vitrification, Walker et al. (U.S. Patent No. 5,565,318) discloses a method for making a semi-spherical reagent comprising at least one biologically active reagent and a glassy filler, such as carbohydrates, carbohydrate derivatives, mixtures of sugars and proteins, preferably Ficoll polymer. A "porous, vitreous composition" apparent is achieved by the dehydration of emulsion droplets under reduced atmosphere at temperatures of 10 ° C to 50 ° C for periods of time from 1 to 4 hours, preferably 1 hour at 10 ° C, 300 Torr. Although, Walker stipulates that other drying profiles (time and temperature ranges) can be used since a Tg between 30 ° C and 45 ° C is achieved, the method is inoperable because a Tg of 30 ° C could never be achieved with dehydration at 10 ° C (see Figure 2); the erroneously elevated Tg was determined in Walker by means of DSC in dried samples in a storage medium based on Ficoll. In this way, although Walker describes the storage of biological samples in a vitrified state, this reference failed to recognize or overcome the theoretical restrictions and technical difficulties of the vitrification processes. Similarly, Jolly et al. (U.S. Patent No. 5,250,429) claims a specific application of vitrification technology for the preservation of restriction enzymes. This method for making the vitrified composition comprising a carbohydrate stabilizer, preferably Ficoll and a restriction enzyme includes vacuum dehydration, overnight at room temperature, followed by drying for an additional 2 hours at 50 ° C. The final "vitrified" composition has a preferred Tg of at least 30 ° C and a storage temperature of 20 ° C. Here again, the brief incubation at 50 ° C described by this reference would be insufficient to raise the Tg above room temperature. Franks et al. (U.S. Patent No. 5,098,893) discloses a vitrification method to make stable the storage of biological materials at room temperature. An apparent "amorphous vitreous state" is produced by dehydrating a mixture comprising a carbohydrate carrier substance and at least one material to be stored. Various vitrification procedures are described. Preferably, an initial desiccation incubation is conducted under vacuum at temperatures between 20 ° C and 30 ° C for 24 to 36 hours. Subsequently, after the Tg has risen sufficiently (determined by DSC to be above 30 ° C), a second evaporation is carried out at 40 ° C to 70 ° C for 2 hours. The Tg of at least 30 ° C is sufficient to allow stable storage at room temperature (20 ° C). Unfortunately, Franks et al, as Jolly et al. were deceived by DSC measurements of dried polymers and significantly underestimated the amount of drying time at elevated temperatures sufficient to produce a Tg above room temperature (see Figure 2).

The vitrification method of the present invention, used in preserving biological specimens, comprises a first stage of desiccation, a second stage of desiccation, whereby the resulting dehydration at temperatures above the selected storage temperature is sufficient to increase the Tg a a point above the desired storage temperature and cool the dried material to the storage temperature to achieve vitrification. The addition of an initial stage to form a mechanically stable porous structure, upon boiling the sample under a reduced atmosphere of less than about 4 Torr, facilitates an increased scale of the preservation method to process large volumes of biological materials. In addition, the application of the Thermally Stimulated Deporalization Current ("TSDC") technique designed for Tg measurements in polymeric materials allows reliable monitoring of vitrification processes in biological materials stabilized using sugar polymers. In this way, the method of this invention produces biological materials dried in the glassy state, having Tg 's above the selected storage temperatures, thus allowing the preservation in long term shelves of these labile materials. Biologically active materials that can be preserved by the present methods include, without limitation, suspensions and biological solutions containing peptides, proteins, antibodies, enzymes, co-enzymes, vitamins, sera, vaccines, viruses, liposomes, cells and certain small multicellular specimens. . Dehydration of biological specimens at elevated temperatures can be very harmful, for example, if the temperatures used are higher than the applicable protein denaturation temperature. To protect the samples from the damage associated with the rise in temperature, the dehydration process can be executed in stages. Primary dehydration should be performed at temperatures that are low enough to allow dehydration without loss of biological activity. If dehydration is preferred at subzero temperatures, one can apply dehydration from a partially frozen state under vacuum. Alternatively, if the samples are stable at higher temperatures, then air or vacuum drying techniques could be employed. A variety of polyols and polymers are known in the art and can serve as protectants since. they increase the capacity of the biologically active material to support drying and storage and not interfere with the particular biological activity. Indeed, protective molecules provide other advantages during preservation (see below, as an aid for foaming) as well as stabilizing biological materials during dehydration. These include, without limitation, simple sugars, such as glucose, maltose, sucrose, xylulose, ribose, mannose, fructose, raffinose and trehalose, carbohydrate derivatives, such as sorbitol, synthetic polymers, such as polyethylene glycol, hydroxyethyl starch, pyrrolidone. of polyvinyl, polyacrylamide, polyethylamine and sugar copolymers, such as Ficoll and Dextran and combinations thereof. Proteins can also serve as protectors. In one embodiment of the present invention, wherein the cells or viruses are preserved, the protective l-composition can further comprise mixtures of: a low molecular weight sugar, a disaccharide and a high molecular weight biological polymer. Low molecular weight sugar is used to penetrate and protect the intracellular structures during dehydration. Low molecular weight, permeation sugars can be selected from a variety of ketoses, which are unreduced at neutral or higher pH or methylated monosaccharides. Unreduced ketoses include: six-carbon, fructose, sorbose and piscosa sugars; the sugars of five carbons, ribulose and xylulose; the four-carbon sugar, erythrulose; and the three-carbon sugar, 1,3-dihydroxydimethexetone. Among the methylated monosaccharides, there are methylated alpha and beta forms of gluco, hand and galactopyranoside. Among the compounds of five methylated carbons are the alpha and beta forms of arabino and xyl pyranosides. Disaccharides such as sucrose are known to be effective protectants during desiccation because they replace the water of hydration on the surface of macromolecules and biological membranes. In addition, the Applicant found that when vacuum dried, sucrose can be effectively transformed into a stable form, composed of thin amorphous films of concentrated sugar. The Applicant also found that the combination of a low molecular weight reduced sugar, such as fructose, with disaccharides, such as sucrose, effectively prevents crystallization of the disaccharide during dehydration. Finally, a polymer is employed to increase the glass transition temperature of the mixture, which can be reduced by the inclusion of the low molecular weight monosaccharides. All biological polymers that are highly soluble in concentrated sugar solutions will work. For example, polysaccharides, such as Ficoll and Dextran and synthetic polymers, such as hydroxyethyl starch, polyethylene glycol, polyvinyl pyrrolidone, polyacrylamide as well as highly soluble synthetic and natural biopolymers (eg, proteins), will help to stabilize biological membranes and increase the Tg. To facilitate the increased scale of the drying and vitrification methods, the first drying stage preferably includes the formation of a mechanically stable porous structure by vacuum boiling. This mechanically stable porous structure or "foam" consists of thin amorphous films of concentrated sugars. Such foams will not dissolve for at least 1 hour while kept at -20 ° C in vacuum. More preferably, mechanically stable foams will not dissolve for at least 3 days when stored at temperatures up to 70 ° C under vacuum. Foaming is particularly well suited for the efficient desiccation of large sample volumes, prior to vitrification and as an aid in preparing a readily divisible dried product suitable for commercial use. Preferably, before boiling under vacuum, the diluted material is concentrated by partially removing the water to form a viscous liquid. This concentration can be carried out by evaporation from the partially frozen or liquid state, reverse osmosis, other membrane technologies or any other method of concentration known in the art. Alternatively, some samples may be sufficiently viscous after the addition of the sugar protectants. Subsequently, the reduced / viscous liquid is further subjected to high vacuum, to make it boil during further drying at temperatures substantially below 100 ° C. In other words, the reduced pressure is applied to suspensions or viscous solutions of biologically active materials to cause the solutions or suspensions to foam during boiling and during the foaming process the removal of the additional solvent makes the final production of a porous foam of closed cell or mechanically stable open cell. Although low vacuum pressures (in the range of 0.90-0.1 atm) can be applied to facilitate initial evaporation to produce a viscous, concentrated solution, much higher vacuum pressures (0-24 Torr) are used to cause boiling. The vacuum for the boiling step is preferably 0-10 Torr and more preferably less than about 4 Torr. Boiling in this context means the nucleation and growth of bubbles that contain water vapor, without air and other gases. In fact, in some solutions, it may be advantageous to debug dissolved gases by applying low vacuum at room temperature. Such "degassing" can help prevent the solution from leaving the drying vessel. Once the solution is sufficiently concentrated and viscous, high vacuum can be applied to cause foaming or controlled boiling. The concentration of the protective molecules cited above, in the range of 5-70% by weight, during the initial evaporation helps to avoid freezing at subsequent high vacuum and aids in viscosity, thus facilitating foaming but discouraging uncontrolled eruptions. Rapid increases in pressure or temperature can cause a foam to dissolve. In this case, to increase the mechanical stability of the porous structures, surfactants can be added since those additives do not interfere with the biological activity of the solute proposed for conversion to dry form. In addition, the drying of the protective polymers also contributes to the mechanical stability of the porous structures. The foams prepared according to the present invention can be stored under vacuum, dry gas, as N2 atmosphere and / or chemical desiccant, before secondary desiccation or subsequent vitrification or before being subdivided or ground or rehydrated in order to restore their original biological activity. Once the invention of combining the drying processes with boiling at reduced pressure is appreciated, it can be seen that in its simplest forms the inventive apparatus is a novel combination of a vacuum pump with a temperature controlled dewatering device. The optional features of such a combination include detectors for temperature and hydrostatic pressure measurements, heat and vacuum controls (in the range of 0-24 Torr), as well as microprocessors to calculate other process parameters based on the data collected from these and other detectors, etc. Such a device allows the implementation of a new two-dimensional process at vacuum and temperature for drying. The following working examples illustrate the formation of the mechanically stable porous foam: (1) An aqueous solution of 50% glycerol isocitrate dehydrogenase from Sigma Chemical Co. containing 59.4 units of activity per ml, dialyzed for 5 hours in 0.1 M TRIS HCl buffer (pH 7.4). The activity of isocitrate dehydrogenase in 0.1 M TRIS HCl solution after dialysis was 26 + _ 1.8 units per ml. The decrease in activity was associated with a decrease in enzyme concentration due to dilution during dialysis. One hundred (100) ul of the mixture containing 50 ul of 50% by weight of sucrose solution and 50 ul of the suspension of isocitrate dehydrogenase in 0.1 M TRIS HCl buffer (pH 7.4), were placed in plastic tubes of 1.5 ml and preserved by drying at room temperature. First, the samples were dried for 4 hours under low vacuum (0.2 atm). Second, the samples were boiled for 4 hours at high vacuum (<0.01 atm). During this stage, a mechanically stable dry foam was formed in the tubes. Third, the samples were stored for 8 days on DRIERITE under vacuum at room temperature. After 8 days, the samples were rehydrated with 500 ul of water. The rehydration of the samples containing dry foams was an easy process that was completed within several seconds. The reconstituted sample was analyzed for its activity when analyzing the ability to reduce NADP, measured spectrophotometrically at 340 nm. The reaction mixture included: 2 ml 0.1 M TRIS HCl buffer, pH 7.4; 10 ul 0.5% by weight of NADP +; 10 ul of 10 mm of MnSO4; 10 ul of 50 Mm 1 - isocitrate; and 10 ul of an isocitrate dehydrogenase solution. The activity was 2.6 + _ 0.2 units / ml, which means that there was no loss of activity during desiccation and subsequent storage at room temperature. (2) A mixture (100 ul) containing 50 ul of 50% by weight of sucrose and 50 ul of a bacterial suspension in ice nucleation, (INB) of Pseudomonas Syringae ATCC 53543, was placed in 1.5 ml plastic tubes and it was preserved by drying at room temperature. First, the samples were dried for 4 hours 1 low vacuum (0.2) atm. Second, the samples were boiled for 4 hours at high vacuum (<0.01 atm). After boiling at high vacuum, a mechanically stable porous structure was formed. Third, the samples were stored for 8 days on DRIERITE under vacuum at room temperature. After 8 days, the samples were rehydrated with 500 ul of water. The rehydration of the samples containing the dry foams was an easy process that was completed within several seconds. Then, the samples were analyzed for their nucleation activity on ice as compared to the control samples. It was then found that there was no significant difference between the ice nucleation activity per 1,000 bacteria in the samples preserved by the present method against the control samples. (3) A sample containing a 1: 1 mixture of concentrated bacterial suspension in ice nucleation (INB) of Pseudomonas Syringae ATCC 5354-3 and sucrose was used. The sample was mixed until all the sucrose crystals dissolved, so that the final suspension contained 50% by weight of sucrose. The suspension was placed in 20 ml vials. 2 g of the suspension was placed inside each vial. The vials were dried inside the vacuum chamber. The vials were placed on the surface of a stainless steel shelf inside the chamber. The shelf temperature was controlled by circulating glycol / water antifreeze at a controlled temperature inside the shelf. Before the vacuum was applied, the shelf temperature was reduced to 5 ° C. -After, the hydrostatic pressure inside the chamber was reduced to 0.3 Torr. Under these conditions the suspension boiled for 30 min. The shelf temperature increased slowly (for 30 min.) To 25 ° C. Under these experimental conditions, dry, visually stable foams were formed within the vials for 3 hours. After this, the samples were kept under vacuum at room temperature for one more day. The ice nucleation activity of preserved INB was measured after rehydration of the sample with 10 ml 0.01 M phosphate buffer. Ice nucleation activity was measured as a concentration of ice nucleation centers that can nucleate an ice crystal in a 10 ul drop of regulator for 5 min. at -5 ° C. The results of the analyzes show nucleation activity on ice in the fresh controls of preserved samples. (4) A suspension of concentrated INB was frozen at -76 ° C for future use. 6 g of the frozen suspension was melted at 4 ° C and mixed with 4 g of a mixture of sucrose: mal trina 9: 1. The sample was mixed until the sugars dissolved completely, from such that the final suspension contained 35 wt.% sucrose and 4 wt.% maltrin. The suspension was placed in 20 ml vials. 2 g of the suspension was placed inside each vial. The vials were dried in a vacuum chamber. The vials were placed on the surface of the stainless steel shelf inside the chamber. The shelf temperature was controlled by circulating ethylene glycol / water antifreeze at a controlled temperature inside the shelf. Before the vacuum was applied, the shelf temperature was reduced to 5 ° C. -The hydrostatic pressure inside the chamber was reduced to 0.5 Torr. Under these conditions the suspension boiled for 30 min. The shelf temperature increased slowly (for 30 min.) To 25 ° C. Visually, the formation of stable dry foams within the vials under these experimental conditions was completed for 2.5 hours. Several vials were removed from the chamber under vacuum and the chamber was again evacuated. After that, the temperature was increased to 50 ° C and the remaining samples were kept under vacuum for 7 days: Preserved INB ice nucleation activity was measured after rehydration of the sample with 10 ml 0.01 M regulator. phosphate. The nucleation activity on ice was measured as a concentration of ice nucleation centers that nucleate an ice crystal in a drop of 10 ul of buffer for 5 min. at 5 ° C. It was found that the ice nucleation activity of the samples that were removed from the chamber under vacuum after drying at 25 ° C was approximately 50% from the initial activity of frozen-thawed INB. (The relative standard error in the measurement of nucleation activity on ice is less than 20%). Because it is known that the freezing of INB does not significantly reduce ice nucleation activity, the 50% decrease in activity observed in this experiment is probably due to the fact that the additional freezing step increases the sensitivity of INB for its preservation by drying. At the same time, we observed no further decrease in INB activity after further drying for 7 days at 50 ° C in vacuum (5) 1 ml of 60% by weight of sucrose solution was conducted in 20 ml vials within a vacuum chamber. The vials were placed on the surface of a stainless steel shelf inside the chamber. The shelf temperature was controlled by circulating glycol / water antifreeze at a controlled temperature inside the shelf. The shelf temperature in this experiment was maintained at 20 ° C. The hydrostatic pressure inside the chamber remained equal to 0.3 Torr. Under such conditions the solution boiled slowly forming a foam consisting of thin films containing concentrated sucrose in the amorphous state. It takes 2 to 3 hours to form visually stable dry foams inside the vials under these experimental conditions. (6) The lyophilized samples of Urokinase were rehydrated with 2 ml of 40% by weight of sucrose. The solutions were then transferred to sterile 20 ml glass vials for future preservation by drying. Before drying, the vials were covered with gray plugs of grooved rubber. The vials were dried in a vacuum chamber. The vials were placed on the surface of a stainless steel shelf inside the chamber. The shelf temperature was controlled by circulating ethylene glycol / water antifreeze at a controlled temperature inside the shelf. Before the vacuum was applied, the shelf temperature was reduced to 5 ° C. Afterwards, the hydrostatic pressure inside the chamber was reduced to 0.5 Torr. Under such conditions the suspension boiled for 30 min. The shelf temperature was slowly increased to 25 ° C for 30 min. Visually, stable dry foams were formed for 3 hours in the vials under these experimental conditions. After an additional 12 hours of drying at room temperature the temperature was increased to 45 ° C for a further 24 hours. After the chamber was filled with the dry N2 gas, the rubber plugs were pushed down and the vials were sealed with folded aluminum seal. The samples were analyzed immediately after desiccation and after 30 days of storage at 40 ° C. After draining Urokinase, the activity was 93% of the initial activity. This decrease was associated with the loss of Urokinase during the transformation of the initial vials to the vials in which Urokinase was dried. After 30 days of storage at 40 ° C, the activity was 90%. In other words, no further significant decrease in Urokinase activity was observed during one month of storage at 40 ° C. (7) The lyophilized samples of Amfoitericin B were rehydrated with 5 ml of 40% by weight of sucrose per vial. Then, the solutions were transferred to 50 ml sterile glass vials for future preservation by drying. Before drying, the vials were covered with gray plugs of grooved butyl rubber. The vials were dried in a vacuum chamber. The vials were placed on the surface of a stainless steel shelf inside the chamber. The shelf temperature was controlled by circulating ethylene glycol antifreeze / water at a controlled temperature inside the shelf. Before the vacuum was applied, the shelf temperature was reduced to 5 ° C. The hydrostatic pressure inside the chamber was reduced to 0.5 Torr. Under such conditions the suspension boiled for 30 min. The shelf temperature was then increased slowly (for 30 min) to 25 ° C. Visually, stable dry foams within the vials were formed after 3 hours under these experimental conditions. After an additional 12 hours of drying at room temperature, the chamber was filled with dry N2 gas and the rubber plugs in a portion of the vials were pushed down. The vials were removed from the chamber and subsequently sealed with aluminum folded seal. The samples were analyzed immediately after desiccation and after 30 days of storage at 27.5 ° and 40 ° C. The results are shown in Table 1, together with the results obtained in the following experiment. Another set of lyophilized samples of Amphotericin B was rehydrated with 50 ml of 40 wt% sucrose per vial. The solutions were then transferred into sterile glass vials for future preservation by drying similar to that described above with additional drying at 45 ° C for a further 24 hours. After that, the chamber was again filled with the dry N2 gas, the rubber plugs were pushed down and the vials were sealed. The samples were analyzed immediately after desiccation and after 30 days of storage at 27.5 ° C and 40 ° C. The results are shown in Table 1. Table 1 Potency of Amphotericin (%) After After 30 days After 30 days from storage of storage to 27.5 ° C dried 40 ° C Td = 25 ° C 108 114 95 Td = 45 ° C 103 102 104 Cont rol 126 N / AN / A Lyophilised Where Td is the maximum temperature during drying. The decrease in Amphotericin activity immediately after desiccation was associated with the loss of Amphotericin during the transformation of the initial vials to the vials in which Amphotericin was dried. The results of the analyzes (Table 1) showed that the power loss was only detected in the samples with maximum temperature during the desiccation at 25 ° C while it was stored at 40 ° C which is in accordance with our claims. (8) A 1.5 ml tube containing a frozen suspension (-76 ° C) of E. coli (Epicurian Coli XL10-GOLD) from Stratagene was dissolved in an ice bath. An aliquot of 100 ul was transferred to 50 ml of NZYM broth (Casien digested yeast extract medium) and incubated at 37 ° C on an orbital shaker overnight. After 14 hours of growth, 10 ml of this growth culture was inoculated in 100 ml of sterile NZYM broth to continue growth of the culture at 37 ° C. During the growth of the culture, the optical density (OD @ 62 Onm) was measured every hour to determine the end of the logarithmic bacterial growth. When the transition phase was reached (OD 1 to 1.06), the cells were ready to be cultured. 5 ml of the culture was intubated in a centrifugation tube and centrifuged for 10 minutes, then the supernatant was poured and the weight of the granules was measured to determine the approximate concentration of the cells. The cells were resuspended with 5 ml of NZYM broth or preservation solution consisting of 25% sucrose and 25% fructose in MRS broth. The re-suspended cells with NZYM broth were used as a control, 1 ml of resuspended cells with 25% sucrose and 25% fructose in MRS broth were placed in 20 ml glass vials and dried in vacuum similar to the INB dries in example # 2. After that, the samples were kept under vacuum for 24 days at room temperature. The dried samples were analyzed at selected time intervals. The survival of the preserved cells was measured after rehydration with 0.1% peptone solution in water at room temperature. To determine the concentration of viable cells, the suspensions were emptied into Petri dishes to the appropriate solution on LB Mi11er agar followed by incubation at 37 ° C for 36-48 hours. It was found that 25 + 10% of the control cells survived after drying and one day of storage under vacuum. It was also found that this same portion of these cells that survived was not reduced during the subsequent 24 days of vacuum storage at room temperature (Figure 3). Partially dehydrated samples or mechanically stable foams, already stabilized by primary drying, may undergo secondary desiccation at increased temperatures. Since the Tg depends on the water content of the sample and since the Tg is increased with increased dehydration, different secondary drying procedures can be applied depending on the desired storage temperature, to generate a Tg consistent with the vitrification in the cooling to this storage temperature. However, because dehydration of the materials is practically impossible once they have entered the vitreous state, the key to vitrification according to the present invention, where storage at ambient temperatures may be desirable, is to lead to dehydration. at a temperature significantly higher than the ambient temperature. The storage temperatures are preferably within the range of 0o-70 ° C. More preferably, the common storage temperature selections are greater than or equal to 0 °, 4 °, 20 °, 40 ° and 50 ° C. The implementation of the vitrification procedure in some cases, where refrigerated storage is selected, it may only require dehydration at room temperature followed by cooling below room temperature for refrigerated storage. However, in other cases, where stability at ambient temperatures is desired, dehydration at a temperature above ambient temperature should be employed, followed by cooling to room temperature. For any given specimen to be preserved, the nature and stability characteristics of the specimen will determine the maximum temperature it can withstand during the primary desiccation stage. In the case of preservation of the enzyme, it was shown that after primary drying at room temperature, the temperature of the secondary desiccation can be increased up to 50 ° C without loss of enzymatic activity. Afterwards, the dehydration process can be continued during secondary drying at a higher temperature. In this way, by the successive or continuous simultaneous increase of the degree of dehydration and dehydration temperature, the labile proteins can be placed in a state of thermal stability at temperatures well above their denaturation temperature. In addition to conducting the secondary desiccation at a temperature above the selected storage temperature, it is critical that its desiccation be carried out for a sufficient period of time to actually raise the Tg above the storage temperature. Based on the empirical results using sucrose-raffinose mixture (Figure 2), it was demonstrated that more than 12 hours of secondary desiccation were required at temperatures above 70 ° C, to raise the Tg above 25 ° C. The primary drying in these experiments was for 12 hours at room temperature (20 ° C). The results suggest that prolonged secondary drying times (more than 12 hours at 70 ° C and more than 36 hours at 50 ° C) may be required to effect increases in Tg above room temperature. For some biological materials that are not heat labile, primary drying at higher temperatures would reduce the secondary drying time at elevated temperatures necessary to increase the Tg to above the selected storage temperature. To ensure that the Tg is actually greater than the storage temperature, at least two methods for estimating the Tg by thermal analysis are known. Differential scanning calorimetry (DSC) is the most commonly used technique. However, the DSC is not reliable for measuring Tg in samples containing polymers (Figure 1). Alternatively, the Thermally Stimulated Depolarization Current (TSDC) methods are adapted specifically for polymer analysis. The TSDC method is preferred because of its reliability for all samples, although it requires slightly larger sample volumes. Although vitrification can increase the dissolution time in water or rehydration solution, which in itself can cause some damage to some specimens in some cases, this undesired effect can be minimized by judicious heating of the rehydration solution before its application to the vitrified specimen. Warming is judicious when controlled within the limits that minimize sample damage. However, some samples can obtain increased stability by rehydration at lower temperatures. Although the invention has been described in detail for purposes of illustration, it is understood that such detail is only for this purpose and variations may be made therein, by those skilled in the art without departing from the spirit and scope of the invention being defined. by the following claims.

Claims (33)

1. CLAIMS 1. A method for the preservation on an industrial scale of a biological or pharmaceutical sample having a volume of at least 1 ml and having a viability or biological activity that is sensitive to degradation during desiccation or storage, comprising: selecting a protective and boiling parameters comprising a temperature, a pressure and a time, in such a way that the sample will boil without freezing and without uncontrolled eruptions and will maintain at least 25% of its viability or biological activity after preservation, - add the protector to the sample to form a solution or suspension; boiling the solution or suspension to the selected boiling parameters until a mechanically stable foam is formed; selecting secondary drying parameters, comprising a temperature and a time, such that after secondary drying, the glass transition temperature of the sample is greater than a selected storage temperature; the secondary desiccation of the mechanically stable foam to the selected secondary drying parameters, wherein the secondary drying temperature is higher than the selected storage temperature; and cooling the mechanically stable foam to the selected storage temperature.
2. 2. The method according to claim 1, wherein the secondary drying is at a temperature greater than 50 ° C.
3. 3. The method according to claim 1, wherein the secondary drying is at a temperature greater than 70 ° C.
4. 4. The method according to claim 1, wherein the secondary drying is for a period of time greater than or equal to 24 hours.
5. 5. The method according to claim 1, wherein the secondary drying is for a period of time greater than or equal to 36 hours.
6. 6. The method according to the claim 1, wherein the mechanically stable foam is stored under vacuum after secondary drying.
7. The method according to claim 1, wherein the mechanically stable foam is stored under dry air or N2 after secondary drying.
8. The method according to claim 1, wherein the protector comprises a monosaccharide, a disaccharide and a polymer.
9. 9. The method according to claim 8, wherein the monosaccharide is a ketose.
10. The method according to claim 8, wherein the monosaccharide is a methylated monosaccharide.
11. 11. The method according to claim 8, wherein the disaccharide is sucrose.
12. The method according to claim 8, wherein the polymer is selected from the group consisting of hydroxyethyl starch, polyethylene glycol, polyvinyl pyrrolidone, Ficoll, Dextran and soluble natural and synthetic biopolymers.
13. The method according to claim 1, wherein after a storage period the dry biologically active material is rehydrated with water or aqueous solution.
14. The method according to claim 13, wherein the biologically active material is rehydrated with water or aqueous solution having a temperature higher than the storage temperature of the sample.
15. 15. The method according to the claim 13, wherein the biologically active material is rehydrated with water or aqueous solution having a temperature below the storage temperature of the sample.
16. 16. The method according to claim 1, wherein the protector comprises a methylated monosaccharide and a disaccharide.
17. 17. The method according to the claim 9, wherein the ketose is selected from the group consisting of fructose, sorbose, piscosa, ribulose, xylulose, erythrulose and 1,3-dihydroxydimethexetone. 1"8.
18. The method according to the claim 10, wherein the methylated monosaccharide is selected from the group consisting of methyl-alpha-D-glucopyranoside, tnet il -bet to-D-glycopyranoside, methyl-alpha-D-mannospyranoside, met il-beta-D-palmitoranoside, met il-alpha-D-galacto pyranoside, met il-beta-D-galacto pyranoside, met il -alpha-D-arabino pyranoside, methyl-beta-D-arabino pyranoside, met il -alpha-D-xyl pyranoside and met il -beta-D-xyl pyranoside.
19. The method according to claim 1, wherein the primary drying stage is carried out at a temperature in the range of about -15 ° C to about 70 ° C.
20. 20. The method according to claim 1, wherein prior to secondary drying, the method further comprises a step of raising the temperature of the mechanically stable foam to a secondary drying temperature, wherein the temperature is increased to a selected to preserve the biological activity of the sample.
21. The method according to claim 1, wherein the secondary drying step further comprises an increase in the secondary drying temperature of at least a first drying temperature secondary to at least a second secondary drying temperature.
22. 22. The method according to the claim 21, wherein the first secondary drying temperature is in a range of about 5o to 25 ° C and where the second secondary drying temperature is in a range of about 25 ° to 70 ° C.
23. 23. The method according to the claim 21, wherein the secondary drying at the first secondary drying temperature is continued for at least 12 hours.
24. The method according to claim 21, wherein the secondary drying at the second secondary drying temperature is continued for at least 24 more hours.
25. 25. The method according to claim 1, wherein the sample is a cell suspension.
26. 26. The method according to claim 1, wherein the vacuum during primary desiccation is less than about 4 Torr.
27. 27. A storage stable composition of biologically active material protected in a dry state, comprising a mechanically stable foam, wherein the mechanically stable foam comprises a methylated monosaccharide and the biologically active material, maintaining the biologically active material 25% of its original activity after a storage period.
28. 28. The method according to the claim 1, wherein the biological or pharmaceutical sample is selected from the group consisting of peptides, proteins, enzymes, antibodies, co-enzymes, vitamins, sera, vaccines, viruses, liposomes, cells and small multicellular specimens.
29. 29. The method according to claim 1, wherein the sample is boiled at pressures that are selected from a range of between 0 and 24 Torr.
30. 30. The method according to the claim 1, where before the boiling stage, the solution or suspension is concentrated.
31. 31. The method according to claim 1, wherein before the boiling step, the solution or suspension is degassed under reduced atmospheric pressure.
32. 32. The method according to claim 1, wherein the temperature of the sample during boiling is above a freezing point and below a temperature at which the sample is damaged.
33. 33. The method according to claim 1, wherein the vitreous transition temperature is measured by the Thermally Stimulated Polarization technique.