冻干显微镜下的冻干工艺 英国凯文.沃德博士.pptx

1、Formulation Design and Characterisation for Successful Freeze-Drying Cycle Development,冻干显微镜下的冻干工艺Dr.Kevin Ward,MRSC凯文.沃德博士Director of R&D,Biopharma Technology Ltd.,Winchester UK英国Biopharma 技术有限责任公司研发总监 Chair of Pharmaceutical&Healthcare Sciences Society Freeze-Drying Special Interest Group,Synopsis

2、 of Presentation,2,Some general rules for formulation development and a few very basic rules for cycle developmentMethods of formulation characterisationFreeze-Drying Microscopy(FDM)DTA/electrical impedance analysis(Zsin)Residual moisture analysis in the lyophilised product,The Ideal Formulation?,3,

3、In some respects,the active ingredient/material alone is the best formulation:Lowest solute density(therefore,lower resistance to vapour flow)No excipient(in)compatibility issuesLower cost of manufactureHowever,the active ingredient may need to be stabilised prior to and during freeze-drying,Formula

4、tion Issues(1),4,It should be remembered that:FREEZING involves CONCENTRATION“Freezing is in itself a form of dehydration”(Felix Franks)Drying may risk the removal of water involved in maintaining the structure of the API(especially for proteins),Formulation Issues(2),5,Low volume of higher concentr

5、ation should freeze-dry faster than larger volume of a lower concentrationMany proteins lose activity when freeze-dried from low concentrationsHowever,some materials(especially organisms)are difficult or impossible to concentrate them without damage,Formulation Issues(3),6,Additionally,some products

6、 are not stable in solution,thereby requiring pH buffering and/or other stabilisation even before freeze-drying startsHowever,remember that pH buffers are designed to work in solution there are no guarantees for the frozen or dried state!,API characteristics,7,Crystalline or amorphous?Teu/Tg/TcBulk

7、characteristics when freeze-driedSolubilityConcentration required prior to FDpH-stability plotIEP&aggregation issues for proteins,What are we formulating to prevent for the API?,8,Destabilisation in liquid stateDamage by the freezing processLoss of activity during dryingDegradation during storageThe

8、refore,need excipients that are chemically compatible with the API during all the above stages,Formulation for freeze-drying involves the use of excipients to,9,provide mechanical strength(bulk)afford thermal stability(a high Tcritical)during lyophilisation and in the dried productprotect the active

9、 ingredient(s)from damage before,during and after processinggive correct pH,and tonicity where required(sometimes achieved by reconstituting medium rather than starting solution),Common Excipients:pros&cons,10,*fulfil the basic requirement of remaining amorphous but protective ability depends on API

10、*PEG often provides cryoprotection but not necessarily lyoprotection as it can crystallise,“Lyo-friendly”buffers,11,CitrateTrisGlycine/HistidinePhosphate often best avoided due to pH shifts on freezing,resulting from di-sodium salt crystallising outOther buffers such as acetate,HEPES,borate,phthalat

11、e,are less well studied for freeze-drying but may be suitable,Other issues in formulating for freeze-drying,12,Mixing amorphous and“crystallising”components together:Phase separation(ice+glass+crystals)Unpredictable“critical temperature”Possible microcollapse/micromeltingInhibition of crystallisatio

12、nResulting metastable components could change over time in dry state,“Extrascientific”issues affecting excipient selection,13,Ethical acceptability in target marketPrevious acceptance by regulatory bodies(FDA,MHRA etc.)for each mode of use(e.g.in-vitro,PO,SC,ID,IP,IM,IV)Grade of purity availableCost

13、Supply chain reliability,Vials of freeze-dried product,GoodOK,Poor,Poor,The product in the“Poor”vials has become soft and dense during freeze-drying,because it has become warmer than its“Critical Temperature”!,14,“What is the Critical Temperature for our product?”,15,The“Critical Temperature”will be

14、:The eutectic temperature(Teu)for crystalline materialsThe collapse temperature(Tc)for amorphous materials(somewhere at or above the glass transition temperature)The lower of the above temperatures for mixed systems(depending on whether micro-collapse is acceptable),We can analyse the critical tempe

15、rature of a formulation before freeze-drying it,for example using:Freeze-Drying Microscopy(FDM)Impedance(Zsin)and Thermal Analysis,Freeze-drying microscopy(FDM),FDM is the study of freeze-drying at the microscopic levelFDM allows determination of collapse,melting and“qualitative phenomena”such as sk

16、in formation,16,What is a Freeze-Drying Microscope?,Effectively a micro freeze-dryer where the freeze-drying of a small sample may be observedFirst designs in the mid-1960sNow manufactured commercially,17,Sample Preparation for FDM,Sample holder,Block,Sample loading takes about 60 seconds.Routine an

17、alysis usually takes 30 90 minutes,Side Doo18 r,Sample Format in Lyostat2,Temperature-Controlled Block,Light Source(from below),Aperture,Quartz cover slip(16 mm dia.),2l of sample,Objective Lens(usually 10 x)Glass cover slip(13 mm dia.)Metal Spacer(70m thick),19,Ideally the raw formulation is usedSo

18、metimes necessary to use samples that have previously been frozen or lyophilisedAfter loading the sample,the Lyostat2 is set to cool to the desired temperature,The sample is allowed to cool and freeze(Note:for eutectic materials,there will be more than one freezing event!),Sample Loading and Cooling

19、,20,When sample reaches the holding temperature and has been observed to freeze,vacuum pump is switched on and drying begins.,Sublimation interface can be seen moving through the frozen sample.,Frozen sample,Dried sample,Sublimation front,On-line plot,Temp/time table,INITIAL FDM IMAGE,21,Increasing

20、or decreasing the temperature of the sample allows you to view its freeze-drying characteristics.,By examining the freeze-dried structure behind the interface,the collapse temperature of the material can be determined.,The temperature may be cycled in order to evaluate Tc more closely,Frozen sample,

21、Sublimation front,Collapsed material,INTERPRETATION OF EVENTS,22,Sample structure lost when collapse temperature was exceeded.,Structure regained as sample was re-cooled to below its collapse temperature.,Frozen sample,Collapsed sample,Regained structure,Sublimation front,INTERPRETATION OF EVENTS,23

22、,100%structure has been regained by lowering the sample temperature.,Sample temperature was again increased to above its collapse temperature,causing the sample to collapse.,Dried sample with structure,Collapsing again on reheating,Frozen sample,Sublimation front,INTERPRETATION OF EVENTS,24,Micro-co

23、llapse(see e.g.Wang,2004),Below Tc of amorphous phase,Above Tc of amorphous phase,A similar effect may also be observed due to the melting of crystalline component(s)onto a rigid amorphous structure(depending on which has the lower critical temperature),Macroscopically similar but is it:Wetter?Less

24、stable?More difficult to reconstitute?,25,FDM image of an aqueous solution of 2%Mannitol+1%Glucose,Frozen material(Drying front),Regions with good dried structure.Just mannitol?,Regions of(micro)collapse.Just glucose?,-41oC,around Tc for glucose.Possible evidence of visible micro-collapse26,So,what

25、else can FDM tell us?,27,Eutectic melting temperature,NaCl Below Eutectic Temperature,Frozen,28,Dry,NaCl Above Eutectic Temperature,Note changes in appearance of frozen structure,Eutectic liquid,29,So,what else can FDM tell us?,30,Eutectic melting temperatureMay give some indication of skin(crust)fo

26、rmation potential of a formulation,Layer of concentrated solute at edge of sample,Crust formation(1),31,Crust Formation(2),Drying only occurs through breaks in the crust,32,So,what else can FDM tell us?,33,Eutectic melting temperatureMay give some indication of skin(crust)formation potential of a fo

27、rmulationWhether heat-annealing may be of benefitTo increase ice crystal size and what conditions are required for this(above Tg?)To encourage some components to crystallise,Effect of annealing on ice crystal size,Sample cooled to-40C,then warmed to-10C,Same sample after a further 15 minutes at-10C,

28、Experiments can be carried out to compare rates of change at different temperatures,in order to establish what annealing temperature might b,most efficient to use in the freeze-dryer.,34,SamplePolariser,FDM setup with polarised lightCamera Analyser,35,Effect of annealing on solute behaviour:FDM with

29、 polarised light function,Sample quench cooled below-40CNo sign of crystals(no light rotation),Same Sample now drying at-18CPolariser shows presence of crystals(white areas),36,Further applications of FDM,37,It is possible to examine differences in relative drying rates:For different formulationsFor

30、 a specific formulation at different temperaturesRef:Zhai,S.,Taylor,R.,Sanches,R.and N.K.H.Slater(2003).Measurement of Lyophilisation primary drying rates by freeze-drying microscopy.Chem.Eng.Sci.58,2313-2323,DTA and Electrical Impedance analysis(Zsin)of Frozen Formulations,38,Differential Thermal A

31、nalysis(DTA),39,Effective yet simple and inexpensive method of analysing frozen solutionsGives exothermic and endothermic events,which can indicate:Glass transitions(amorphous)Eutectic melts(crystalline)Crystallisations(amorphous to crystalline)At Biopharma,we use this in combination with electrical

32、 impedance(Zsin)analysis to give a more complete picture,Electrical Impedance(Zsin)Analysis,40,This is a more sophisticated version of electrical resistance(R)analysisImpedance(Z)is a combination of Resistance+Inductance+CapacitanceLooking at Z(or more specifically Zsin)can give more detailed inform

33、ation about frozen solute mobility(Rey,1999).,Investigating Zsin Methods(1),We have developed a device(Lyotherm2)in collaboration with Prof.Louis Rey,which is capable of analysing Impedance at a frequency of 1000Hz,Lyotherm2 allows both DTA and Impedance(Zsin)analysis to be carried out on a sample in the frozen state large sample volume to give stronger signal,41,Investigating Zsin Methods(2),Appr