Introduction:
To acquire the consistent results in biomedical research, familial stableness is indispensable and it is achieved via cryopreservation technique.
Technique of cryopreservation involves the saving of feasible cells, populating tissues, gametes, embryos, variety meats and besides some beings on chilling at low sub-zero temperatures, characteristically at -196A°C for a drawn-out clip to implement the applications of these biological stuffs over biomedicine, preservation and carnal reproduction ( Mazur. , 1970 ) . Long clip storage is achieved by utilizing this technique ( Pereira and Marques. , 2008 ) .The cryopreservation technique is carried out in two different ways:
Vitrification and 2. Controlled slow chilling ( Frederickson. , 2000 ) .
To continue with these two protocols, several stairss need to be taken and besides we must look its advantages and restrictions. Change in temperature induces chief two amendss – Freezing hurt and chilling hurt and these hurts are reduced greatly by utilizing the cryoprotectant. Detailed analysis of these and its function in both vitrification and decelerate chilling techniques is described below ( Fuller et al. , 2004 ) .
TWO APPROACHES OF CRYOPRESERVATION:
Vitrification:
Preservation of biological stuffs under hypothermic status with devoid of freeze is called as vitrification ( Rall, W. F. and Fahy. , 1985 ) . Vitrification bring on glassy formation alternatively of formation of ice crystal, therefore it is non doing indispensable harm to the life system ( Fuller et al. , 2004 ) .
Slow Cooling:
Continuing cells from room temperature upto the temperatute of liquid N is called as slow chilling. Damage associated with this are reduced utilizing cryoprotectant
( Gao and Critse. , 2004 and Guan et al. , 2008 ) .
Major DAMAGES ASSOCIATED WITH THIS Technique:
During cryopreservation, major hurt that induces harm to the cell endurance is:
Freezing hurt
Chilling hurt. ( Gao and Critser. , ( 2000 ) .
FREEZING INJURY:
To transport out with the important saving at hypothermic temperature, H2O becomes solidify and it causes the cell harm, even to unviability. ( Fuller et al. , 2004 ) .
) At high rate of freeze, ice nucleation provokes. Most cells has thermodynamic stop deading point above -0.5A°C. But the freeze of cell developed merely after making – 5A°C. Unfrozen province of cell and its environment occurs due to the protective solute ‘s ace chilling and stop deading point depression. External medium impetuously bring on ice ‘seeding ‘ formation between – 5A°C and – 15A°C, but composing of cell persist in a super cooled and unfrozen province. Extracellular solution remains in unfrozen fraction and that influences the ice formation in external medium. Concentration of solute in extracellular solution rises in regard to the lessening in temperature. So, ice formation developed and encourages likely instability between the cell and external solution. Water present inside the cell is in super cooled province than extracellular part ; due to the possible instability, H2O migrates to extra cellular part and freezing. Entire event of cell relays over the chilling. Decrease in chilling induces the desiccation of cell and the intracellular freeze is prohibited. Rapid chilling induces intracellular ice formation as a consequence of rapid lessening in excess cellular solution than the H2O spreading out from the cell. Ice formation inside the cell is surely deadly ( Fuller et al. , 2004 ) .
Intracellular Ice nucleation:
Homogeneous nucleation, seeding by extracellular ice and heterogenous nucleation are the possible ways IIF.
When the rate of chilling lessenings, electrolytes concentration on stop deading relate to unfrozen subdivision of H2O. It is classified into intra and extracellular electrolytes.
Cell VOLUME DECREASE:
Volume lessening whilst stop deading induces hurt to cells by minor tonus solution. Decrease in cell volume whilst freezing concerns cell harm.
Dehydration theories ( Meryman ) :
Inability of cell to shrivel osmotically below perspective degree whilst it tries to make osmotic equilibrium. This is called as ‘minimum volume ‘ hypothesis over harm of slow-freezing.
Chilling INJURY:
Different cell type reaches harm upon chilling about 0 A°C without stop deading, i.e without ice formation. Damage occurs irreversibly on chilling temperature. If this happens in sperm cells, it is termed as temperature daze. Direct and indirect cooling hurts are the major two classs of chilling hurt. These hurts are expressed upon lower temperature and it is termed as ‘cold daze ‘ . It depends over the rate of chilling. Indirect chilling hurt occurs on exposure to cut down temperature for a drawn-out clip and it is independent of rate of chilling. It is sometimes hard to separate cold daze and indirect chilling hurt ( Fuller et al. , 2004 ) .
COLD Daze:
Cells become sensitive to cold daze as it quickly cooled at low temperature for long clip. Viability of cell and its badness of hurt are relays over the ”rapid ” or “ slow ” chilling. Besides this cold daze s non depends on warming rate but it depends on rate and continuance of chilling ( Tsai et al. , 2009 ) . Membrane permeableness is injured upon rapid chilling and opportunity of reversibility is available for some instances. Addition of specific compounds and cell former chilling status influences the response of cell. Thermotropic activity of lipid membrane is suspected to place the hurt due to cold daze. Lipid stage passages of cell membrane influence the hurt of cold daze in many species.
INDIRECT CHILLING INJURY:
Long exposure of biological stuffs at low temperature causes indirect chilling hurt and this hurt is chilling rate independent. Lipids and proteins are changed by agencies of its activity and construction. Eg: alterations in enzyme activity and protein denaturation. Besides the metabolic tract and enzyme linked reactions face some changes as the co-ordination is decreased harmonizing to the lessening in temperature rate ( Fuller et al. , 2004 ) .
ROLE OF CRYOPROTECTANT:
Cryoprotectant enhances the desiccation procedure once formation of external ice. The activity of H2O is greatly reduced during the deficiency of H2O loss. By cut downing the consequence of salts, it acts as a protective influence on construction of the cell.
Freezing protocol patterned advance demands consistent method to observe the cell viability ( Fuller et al. , 2004 ) .
Cryopretectant may be a chemical additive that is added to the solution before stop deading to guarantee the high endurance rate after station melt.
Role of cryoprotectant is to back up and protect the endurance of biological stuff upon chilling to hypothermic temperature for long continuance of clip. Property of an effectual cryoprotectant is high solubility with reduced toxicity. Cryoprotectant can be classified harmonizing to chemical category and manner of action. Each categorised cryoprotectant plays a critical function upon dissolving and chilling.
Freezing point depression is promoted by pervading cryoprotectant due to the presence of electrolytes. Non-permeating cryoprotectant promotes decreased formation of ice crystal upon freeze by anterior desiccation of biological stuff.
Reduced divergence of volumes and solutes harm concentration is enhanced by the cryoprotectant. Eg: DMSO ( Fuller et al. , 2004 ) .
Cell protection is besides achieved by fluctuating formation of ice crystal into harmless form and size during dissolving and freeze.
It is necessary to look the toxicity of cryoprotectant over cells and its permeableness. High concentration of cryoprotectant itself injured. Direct exposure of cryoprotectant with membranes and proteins induce ionic pumps break over trans membrane and besides causes enzyme inactivation. But more sum of cryoprotectant in vitrification ensures syrupy and formless medium. The possible attack to get the better of this job is achieved by utilizing mixture of cryoprotectant at definite concentration ( Tsai et al. , 2008 and Fuller et al. , 2004 ) .
SIMILARITY AND DIFFERENCES OF VITRFICATION AND CONTROLLED SLOW Cooling: -ADVANTAGES AND DISADVANTEGES:
Effective vitrification demands tremendous sample chilling and solute with high concentration with combination of cryoprotectant ( Bielanski, and Lalonde. , 2009 ) .
Successful vitrification was enhanced in 1985 to cryopreserve the mouse embryo and this technique is besides efficaciously applied to continue the blood cells, tissues, embryo and oocyte of Drosophila melanogaster, Asparagus officinalis works every bit good as embryos of legion mammalians. Cryopreservation of mammalian system study entails the success achieved through the technique of controlled freeze. However in the instance of fruit fly, vitrification occupies a success where the controlled freeze failed. Efficient vitrification technique relays on an optimisation of some specific stairss that includes appropriate composing and concentration of provided vitrification solution with specific cooling/warming environments. Besides this technique induces equilibration of life cells present and to thin the cells present in the vitrification solution ( Fuller et al. , 2004 ) .
The usage of slow chilling includes several scopes of rates of chilling when we compared vitrification with rapid and extremist rapid chilling. The ultimate end of both techniques is to bring forth a glass like province of cells to forestall the harm caused by formation of ice crystal upon chilling ( El-Danasouri, and Selman. , 2005 ) . At first, vitrification process involves drawn-out pre-equilibrium process. Currently, combination of perforating and non-penetrating solutes is used with non-toxic belongings with several scopes of chilling rates. Both the technique consequence in successful cryopreservation of embryos and oocytes of worlds ( Borini, and Coticchio. , 2009 ) . Even these processs resulted good, slow chilling technique applied for cryopreservation of oocytes shows really less consecutive rates when compared to vitrification. Vitrification acts as a promising technique in many countries in generative engineering, even though its positive rates need to set up farther.
Vitrification is an easy process and that consumes less clip continuance. Besides this vitrification technique is safer and cheaper when compared to command slow chilling. ( A Kuleshova, L.L. and Lopata, A. , 2002 )
Cryopreservation of cell faces comparative harm due to chilling and dissolving. Largely damage occurs whilst hive awaying the cells at hypothermic conditions. Keeping healthier cells for farther usage are really indispensable and we need to forestall it from familial impetus and taint. To halt the biological action of the cell and to keep that in its preserved province is the function of cryostorage. In fluid system, molecular gesture is achieved via temperature ( Fuller et al. , 2004 ) .
The molecular gesture get cut down harmonizing to the lessening in temperature.
Biological species are designed to be feasible and active at maximum temperature but it lost its activity at hypothermic status. At that case, lipid stage passage, structural and enzymatic harm and de-polymerization occurs ( Kiefer et al. , 2005 ) . Major damaging phenomenons upon chilling are: Intracellular ice crystallization and osmotic harm. Chilling sensitiveness or cold daze leads the cell to decease at the temperature below 0A°C. These effects differ from one cell type to another. Bacteria and some viruses can prolong in – 60 grade but the keeping temperature for most of the biological sample is below -130A°C ( Fuller et al. , 2004 ) .
Conventional cryopreservation method is established to get the better of the formation of ice whilst chilling. Formation of ice crystals are avoided by vitrification via its use of concentrated solution and rapid chilling. This vitrification method contains a possible advantage as it is rapid and this technique does non necessitate rate chilling equipment. Vitrification consequences in good endurance rate of preserved oocytes and embryos. Cryopreservation widely applicable to retain familial resources and protect the endemic species ( Tsai et al. , 2010 ) . Vitrification acts as an alternate method to decelerate chilling. This provides higher endurance of gestation scope and embryo viability. This vitrification acts as a suited process in sterility clinics. In this, cryopreservation of legion embryos is maintained within short period and therefore it acts as a simple method. Still, less figure of controlled surveies and childbearings are concerned over vitrification technique. Multiple gestation hazard associated with stop deading utilizing controlled slow chilling is restricted utilizing vitrification. Besides it works with high efficaciousness ( Kuc et al. , 2010 and Trounson and Mohr.,1983 ) . Vitrification acts as an attractive cryopreservation method when compared with controlled slow chilling technique. In contrast to decelerate chilling method, this vitrification technique is precise and in this each and every measure is visualized. Vitrification reduces the clip continuance of exposure to sub-physiological environments. It requires merely less than 10 proceedingss transporting out while slow chilling takes about two hours. Vitrification is simpler and it does non necessitate dearly-won programmable freezing equipment. In some instances, chilling hurt besides prevented by vitrification ( Fuller et al. , 2004 ) .
Needle immersed vitrification requires less concentrated and minimal volume of vtrification solution. Maximize chilling rate, cut down toxicity of vitrification solution with low volume of less concentration cryopreservation.
In vitrification, upon freeze, merely legion ice crystals are formed and so less mechanical break consequences by ice crystal ( Wang et al. , 2008 ) . Vitrification technique is accompanied without the backdown of more sum of H2O. So, less chemical harm merely exist. But the chemical harm due to cryoprotectant is a complicated affair. ( long ) . Common fluctuation held between vitrification and controlled slow freeze is due to the legion add-ons of cryoprotectants. Execution of maximal equilibration status and dilution are expected from the vitrification media. It is necessary to utilize low toxic agents in the vitrification solution.
To accomplish an efficient vitrification, preparation of 2 things over the vitrification technique are indispensable.
1. physicochemical belongingss: Concentrated vitrification solution bring on glassy solid formation and it helps to devoid of crystallisation whilst chilling.
2. cyoprotectant: utilizing low toxic cryoprotectant with an intrinsic permeableness.
Vitrification protects the cell from ice formation while cryopreservation.Both the vitrification and decelerate chilling are used to continue human oocytes ( Fuller et al. , 2004 ) .
In instance of human ES cell cryopreservation, improved efficiency is noted in vitrification than in traditional cryopreservation ( Zhou et al. 2004 and Peng-Fei et al. , 2006 ) . Analysis of settlements after vitrification outputs rapid growing and distinction when compared with slow freeze technique. Vitrification acts as a promising attack to cryopreserve the multi cellular tissue. Even, vitrification achieved certain virtues ; it is associated with several jobs. In the province of glassy, ‘glass ‘ is susceptible to checking. Care is indispensable on warming to pretermit the formation of ice. Heat transportation rate happening during vitrification procedure may change depends on device.Vitrification include the rapid chilling protocol and it is hard to keep at certain temperature with the available equipment. Very rapid and even rewarming requires avoid of devitrification.
During slow chilling, increase solute concentration to glaze passage demands while prevent by chilling slow plenty to let the cells to desiccate to protect intracellular supercooling ( Youssry et al. , 2008 ) .
Vitrification requires higher and potentially cytotoxic concentration of cryoprotective agents for one hr before its submergence into liquid N at specific temperature. To cut down its toxicity, pre equilibrium performed at 4A°C. It allows the direct visualizaton of cell by the operator ( El-Danasouri, and Selman. , 2005 )
Eventhough this vitrification entails with meritful attacks, this technique still been experimental. Besides, it requires more additives to make and it is potentially cytotoxic. This technique extremely depends on operator. Clocking takes to cover all the stairss and it is critical. In contrast to decelerate freeze, this vitrification needs adequate degree of preparation.
If the glassy solution stars to devitrify, ( crystalise into ice ) , viability will be lost. This happens when dissolving or drawn-out clip of storage persists ( Fuller et al. , 2004 ) .
Viability of glassy samples is non certain for drawn-out period of clip but in instance of slow chilling, preserved cells can be feasible for many old ages, even to 1000s of old ages.
Direct exposure of cryogen can be achieved by fast chilling. As it is so, this procedure may transport possible taint of being from the liquid N. So, this procedure can non be applicable for curative cells.
Vitrification technique is applied merely to chill cell suspensions in minor measures. This method is non projected to use in big measures like cryovials, matrix tubings, bags, microtitre home bases etc. Quality control measuring via this vitrification technique is made to be impossible as we need to take experiments for all straws. ( Fahy et al. , 2004 )
Normally the slow chilling process is used in sterility centres. But it is associated with documented restrictions. Besides sometimes, it amendss sensitive parts of the cell ( eg- zona pellucida ) and it bring on biological alterations. Because of these alterations, we will acquire a low results. To get the better of this, Modifying cryopreservation process is attained- freeze and melt by polymers. This besides enhanced with altering the clip continuance of the chilling protocol and it is looked every bit same as the way to simplify and fast up cryobanking processs to acquire good consequences. As the vitrification technique connected with some jobs, it acts as a challenging technique for generative medical specialty. The slow freeze technique serves as an effectual method for worlds excessively ( Mandelbaum, J. , 2000 ) . An alternate method for cryopreservation was developed and it is called as vitrification.
Comparative survey has been taken between controlled slow chilling and vitrification techniques with patients set abouting controlled ovarian stimulation in GnRH agonist to find efficaciousness. The rate of gestation after vitrification reveals more than higher consecutive rate than consequence achieved via slow chilling. Efficacy of vitrification outputs ( 50.4 % ) , and decelerate chilling consequences in ( 25.9 % ) consecutive rates.Human ovarian tissue besides cryopreserved ( Noriko et al 2009 )
Both cryopreservation every bit good as cryostorage contains budding advantages, particularly in invitro fertilisation. Ultimate end of cryopreservation is to accomplish maximal continuity rate and sustainability of biological system after dissolving. In slow chilling process, clinically satisfactory consequence has non been attained. Slow chilling process needs dearly-won equipment and besides it is clip devouring.
One of a important advantage of vitrification procedure is its inclination to organize any ice crystals during both chilling and warming. In contrast, its restriction held in toxic effects due to add-on of cryoprotectants and taint via liquid N.
In slow chilling technique, toxicity of cryoprotectant is comparatively less. But many research results supports the vitrification procedure instead than decelerate chilling in birthrate intervention ( Tsai et al. , 2010 ) . Blastocyst cells can be preserved by both the cryopreservation techniques. Among these, vitrification promotes increasing opportunity for future development. A dependable promotion is needed for vitrification to heighten the saving of excess blastodermic vessicles. Unsatisfactory consequences have been produced for the blastodermic vessicle saving through slow freeze method. Vitrification acts as an alternate rule which is allied with capableness of bring oning more gestation rate and increased endurance of embryo upon cryopreservation ( Trounson and Mohr. , 1983 and Fuller et al. , 2004 ) .
Decision:
Approch taken by Kolibianakis et al consequences in the comparative analysis of both vitrification and controlled slow chilling. And its result provides similar consequences are given by both of these techniques. But relatively, station melt endurance frequence is better in vitrification than slow chilling. Finally, they suggested that the there is no nexus between the vitrification procedure in giving high rate of gestation but it displays the successful station melt endurance both in the cleavage phase and in the blastodermic vessicle phase ( Youssry et al. , 2008 and Porcu et al 2000 ) .
Harmonizing to Balaban et Al ( 5 ) endurance rate of human 3 twenty-four hours embryo saving reported the per centum of endurance rate by vitrication as 94.8 % whereas slow chilling provides 88.7 % . ( Kuc et al. , 2010 ) .
Vitrification survey over the embryo in cleavage phase testified 80 % of survival rate and 22-35 % of gestation rate. These consequences are more important than the slow chilling process. Although the two chief attacks of cryopreservation contains signficant consequences, Vitrification additions more positive results. Even in both the instances, restrictions persist. All of its restrictions can be ever overcomed by its positive side.
