
Description
Numeroustechniqueshavebeendevelopedtoprepareimmunoliposomesbasedonthenucleophilicreactivityoffreeaminegroupsofproteinsorpeptides.OneofthemostpopularandcommonlyusedmethodsistocovalentlycouplefreecarboxylicgroupstoprimaryaminesthroughactivationofthecarboxylgroupswithEDC(1-ethyl-3-[3-dimethylaminopropyl]carbodiimide).EDC,whichisaso-calledzero-lengthcrosslinkingagent,reactswiththecarboxyltoformanaminereactiveintermediate(O-acylisourea).TheproducedO-acylisoureacanbeeasilydisplacedbynucleophilicattackfromtheprimaryaminogroupsinthereactionmixture.However,thisintermediateisunstableandhydrolyzedinaqueoussolutions.Inordertopreventtheintermediatehydrolysis,sulfo-NHS(N-hydroxysulfosuccinimide)isaddedtoEDCtoproduceasignificantlymorestableandmoresolubleactiveintermediate(NHSester).
Consequently,theimmunoliposomesarepreparedbyatwo-stepcouplingprocedure:first,activatingthefreecarboxylgroupofthelinkerlipidincorporatedintheliposomeswithEDCandsulfo-NHS,andthencovalentlyconjugatingtheantibodiestothelipidsthroughdisplacementofsulfo-NHSgroupsbyantibodyamines,asdepictedbelow.EDC/sulfo-NHScouplingreactionsarehighlyselectiveandhighlyefficient,andtheBIOLOGicalactivityoftheproteinorpeptideispreserved.

Immunosome®-Donecanylisanon-PEGylatedproduct.Forotheraminereactive(PEGylatedandnon-PEGyalatedproducts)andalsoImmunosome®productssuitableforothertypesconjugationmethodsseehere.
FormulationInformation
Immunosome®-Dodecanyl(Non-PEGylated)
LipidComposition | Concentration(mg/ml) | Concentration(mM) | MolarRatioPercentage |
---|---|---|---|
Total | 14.82mg/ml | 22.45mM | 100 |
L-alpha-Phosphatidylcholine | 12 | 15.5 | 69 |
Cholesterol | 2.6 | 6.73 | 30 |
1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine-N-(dodecanyl)![]() | 0.22 | 0.22 | 1 |
BuffersandLiposomeSize | Specification |
---|---|
Buffer | PhosphateBufferedSaline |
pH | 6* |
LiposomeSize | 100nm |
*InordertohaveahighlyefficientactivationreactionwithEDCandSulfo-NHS,pHofPBSbufferwasadjustedto6. |
ConjugationProtocol
MaterialsandEquipment
Inordertoconjugatetheamineonyourantibody, proteinorpeptidetoImmunosome®-Dodecanyl(Non-PEGylated)liposomesyouwillneed:
- EDC(1-ethyl-3-(3-dimethylaminopropyl)carbodiimidehydrochloride).Thesolutionshouldbemadefreshmomentsbeforeuse.
- Sulfo-NHS(N-hydroxysulfosuccinimide).Thesolutionshouldbemadefreshmomentsbeforeuse.
- Sephadex®spincolumn.SephadexsizeexclusionspincolumncanbeusedforseparationofliposomesformfreeEDC(MW:191.70).SinceEDCisbeingseparatedfromlargeliposomeparticlesthenanysizesofSephadex®spincolumnsuchasG-10,G-15,G-25,G50canbeused.However,keepinmindthatyouwilllosealargepercentageofyourliposomesonthespincolumn.Alternatively,insteadofremovingtheEDCbyspincolumnyoucanquenchitbyusing2-mercaptoethanol.
- 2-Mercaptoethanol.ToquenchtheunreactedEDC,2-mercaptoethanolisaddedtoformastablecomplexwiththeremainingcarbodiimide.The2-mercaptoethanolmightnotbenecessaryifyouprefertocleanupyourliposomefromfreeEDCusingaspincolumn.
- Float-A-Lyzer®withaproperMWCOthateasilyallowsthecleanupofyourliposomeconjugatedligandfromfreeandnon-conjugatedprotein,peptideorantibody.YouneedtomakesurethattheMWCOisbelow1,000,000dalton.At1,000,000daltontheporesizeonthedialysismembranegetscloseto100nmandthereforeyourliposomescanbedialyzedout.Youcannotusedialysiscassettesblindly.Pleaseunderstandthetechniquebeforeusingeitherspincolumnordialysiscassette.IfyoudonotusethecorrectMWCOyoucanloseyourentireprep.Forthisprotocol,werecommendMWCOof300,000dalton.
PreparationMethod
Thetwo-stepprotocolincludestheactivationofcarboxylgroup-containingliposomeswithEDC/sulfo-NHS,andsubsequentconjugationwiththeaminegroupontheproteins,peptidesorantibodies:
- Inordertoactivatethecarboxylgroupsontheliposomes,EDCandsulfo-NHSshouldbeaddedtotheliposomes.ThetotallipidconcentrationinImmunosome®-Dodecanyl(Non-PEGylated)is22.45mM.1%molofthelipidinliposomescontainsCOOHgroupandonlyhalfofthemareexposedtotheoutsideoftheliposomes,whichisequalto0.11mMofreactiveconjugablelipid.For2mlvolumeliposome,thisisequalto2.20×10-7molandfor5mlvolumeliposome,thisisequalof5.50×10-7molofCOOH.Add10-foldmolarexcessofEDCand25-foldmolarexcessofsulfo-NHStoImmunosome®-Dodecanyl(Non-PEGylated).Toaidinaliquotingthecorrectamountofthesereagents,theymaybequicklydissolvedinthePBSbufferatahigherconcentration,andthenapropervolumeimmediatelyPipettedintotheproteinsolutiontoobtainthepropermolarquantities.
- Mixwellandallowthereactiontoproceedfor15minatroomtemperature.
- Beforeaddingtheprotein,peptideorantibody,removetheexcessEDCeitherusingasizeexclusionspincolumn,suchasSephadex®spincolumnorthroughquenchingby2-mercaptoethanolata20mMfinalconcentration.Additionof2-mercaptoethanolwillnotimpacttheliposomes.
- Dissolvetheprotein,peptideorantibodyat1-10mg/ml,dependingontheantibody,proteinorpeptide,inPBSorotheramine-free,carboxylatefreebuffer,pH7-8.
- Addtheprotein,peptideorantibodytotheEDC/Sulfo-NHSactivatedImmunosome®-Dodecanyl(Non-PEGylated)liposomes.Themolarratioofthereactivecarboxyllipidtoprotein,peptideorantibodyispreferredtobearound10:1.Thetotallipidconcentrationinourliposomesis22.45mM.1%molofthelipidinliposomescontainsCOOHgroupandonlyhalfofthemareexposedtotheoutsideoftheliposomes,whichisequalto0.11mMofreactiveconjugablelipid.For2mlvolumeliposomes,thisisequalto2.20×10-7molandfor5mlvolumeliposomes,thisisequalof5.50×10-7molofCOOH.Youwillneedtocalculatethetotalmolesofyourpeptide,proteinorligandinyoursolutionandadd1:10molarratioofligandtolipid.
- Mixwellandallowtoreactfor2hatroomtemperature.
- Removethenon-conjugatedprotein,peptideorantibodyfromtheimmunoliposomesbydialysis.Wepreferdialysistosizeexclusioncolumns.Dialysisisamuchslowerprocessbuttherewillbeminimumlossofimmunoliposomesaftertheprepiscleanedfromnon-conjugatedprotein/peptide/ligand.Spincolumnsaremuchfaster;however,youcaneasilyloseover50%oftheliposomesonthespincolumn.WerecommendusingFloat-A-Lyzer® dialysiscassettefromSpectrumLabs.YouwillneedtochooseacassettewithproperMWCOdependingontheMWofyourprotein,peptide,antibodyorantibodyfragment.NOTE:Ifyoudecidetouseadialysiscassette,youwillneedtomakesurethattheMWCOisbelow1,000,000dalton.At1,000,000dalton,theporesizeonthedialysismembranegetscloseto100nmandtherefore,yourliposomescanbedialyzedout.Youcannotusedialysiscassettesandspincolumnsblindly.Theycomeinvarioussizesandyouneedtochoosethecorrectsizewisely.Dialyzetheimmunoliposomesolutionin1literofPBSatpH7.4for8hours.Changethedialysisbufferwithafresh1literofPBSandletisdialyzeforanother8hours.Afterthisstep,yourcleanedupimmunoliposomeisreadytobeused.
LiposomeParticleCalculator
Immunosomesareunilamellarliposomesandsizedto100nm.Themolarconcentrationofliposomeis22.45mM.Byhaving liposomediameter(nm)andlipidconcentration(µM),youcancalculatethetotalnumberofthelipidsinoneliposomeandthenumberoftheliposomesinonemilliliteroftheliposomesolution.Tousethecalculatorclick here.
TechnicalNotes
- EDCandsulfo-NHSshouldbepreparedimmediatelybeforeuseandkeptatroomtemperature.
- TheactivationreactionwithEDCandSulfo-NHSismostefficientatpH4.5-7.2,andEDCreactionsareoftenperformedinatpH4.7-6.0.Forthisreason,wehaveformulatedtheliposomesinPBSbufferandadjustedthepHto6.
- ReactionofSulfo-NHS-activatedmoleculeswithprimaryaminesismostefficientatpH7-8,andSulfo-NHS-esterreactionsareusuallyperformedinphosphate-bufferedsaline(PBS)atpH7.2-7.5.
- Trisbuffershouldneverbeusedinanystepoftheprocesssinceitcontainsamine.
- IfyouareusingaligandorpeptidethatishydrophobicthenitisrecommendedtosolubilizeitinDMSOorDMFandthenaddthebuffertoit.Itisrecommendednottousemorethan5%volumeofDMSOorDMFinthesolution.DMFandDMSOarebothcompatIBLewithliposomesandtheyarealsomiscibleinwater.Otherorganicsolventsuchasethanolandchloroformarenotcompatiblewithliposomesandwillcausetheliposomestolyse.IfyouendupusingDMSOorDMFthenaftertheconjugationreactionisdone,youneedtoremoveDMSOandDMFfromtheliposomes.InordertodothatyouneedtouseadialysiscassettethatismadefromREGENERATEDCELLULOSEMEMBRANE.NOTE:NotallmembranesarecompatiblewithDMFandDMSO.WerecommendusingaSlide-A-Lyzer™MINIDialysisDevicewithMWCOof2KmadefromregeneratedcellulosemembranemanufacturedbyThermofisher.AfterDMSOorDMFisremoved,youcanuseFloat-A-Lyzer®dialysisdeviceforthefinalstepofcleaninguptheprep.
- Liposomesshouldbekeptat4°CandNEVERbefrozen.
Database
Directlinktothedatabasepageforeasynavigation:ImmunoliposomesConjugationDatabase
Appearance
Immunosome®-Dodecanylisawhitetranslucentliquidmadeofnanosizeunilamellarliposomes.Usuallyduetothesmallsizeofliposomesnosettlingwilloccurinthebottomofthevial.Theliposomesarepackagedinanambervial.
Ordering/ShippingInformation
- Allliposomebasedformulationsareshippedonblueiceat4°Cininsulatedpackagesusingovernightshippingorinternationalexpressshipping.
- LiposomesshouldNEVERbefrozen.Icecrystalsthatforminthelipidmembranecanrupturethemembrane,changethesizeoftheliposomesandcausetheencapsulateddrugtoleakout.Liposomesinliquidformshouldalwaysbekeptintherefrigerator.
- ClientswhoorderfromoutsideoftheUnitedStatesofAmericaareresponsiblefortheirgovernmentimporttaxesandcustomspaperwork.EncapsulaNanoSciencesisNOTresponsibleforimportationfeestocountriesoutsideoftheUnitedStatesofAmerica.
- WestronglyencouragetheclientsinJapan,Korea,TaiwanandChinatoorderviaadistributor.Toughcustomsclearanceregulationsinthesecountrieswillcausedelayincustomclearanceoftheseperishableformulationsifordereddirectlythroughus.Distributorscaneasilyclearthepackagesfromcustoms.Toseethelistofthedistributorsclickhere.
- ClientsorderingfromuniversitiesandresearchinstitutesinAustraliashouldkeepinmindthattheliposomeformulationsaremadefromsyntheticmaterialandtheformulationsdonotrequirea“permittoimportquarantinematerial”.LiposomesareNOTbiologicalproducts.
- Ifyouwouldlikeyourinstitute’sFedExorDHLaccounttobechargedforshipping,thenpleaseprovidetheaccountnumberatthetimeofordering.
- EncapsulaNanoScienceshasnocontroloverdelaysduetoinclementweatherorcustomsclearancedelays.YouwillreceiveaFedExorDHLtrackingnumberonceyourorderisconfirmed.ContactFedExorDHLinadvanceandmakesurethatthepaperworkforcustomsisdoneontime. AllsubsequentshippinginquiriesshouldbedirectedtoFederalExpressorDHL.
StorageandShelfLife
Storage
Immunosome®productsshouldalwaysbestoredatinthedarkat4°C,exceptwhenbroughttoroomtemperatureforbriefperiodspriortoanimaldosing.DONOTFREEZE.IfthesUSPensionisfrozen,theencapsulateddrugcanbereleasedfromtheliposomesthuslimitingitseffectiveness.Inaddition,thesizeoftheliposomeswillalsochangeuponfreezingandthawing.
ShelfLife
Immunosome®-Dodecanylismadeondailybasis.Thebatchthatisshippedismanufacturedonthesameday.Itisadvisedtousetheproductswithin4monthsofthemanufacturingdate.
ReferencesandbackgroundreADIng
1.HermansonGT.Bioconjugatetechniques.Academicpress;2013Jul25.
2.TorchilinV,WeissigV,editors.Liposomes:apracticalapproach.OxfordUniversityPress;2003Jun5.
3.GrabarekZ,GergelyJ.Zero-lengthcrosslinkingprocedurewiththeuseofactiveesters.Analyticalbiochemistry.1990Feb15;185(1):131-5.
4.YanL,CraytonSH,ThawaniJP,AmirshaghaghiA,TsourkasA,ChengZ.ApH‐ResponsiveDrug‐DeliveryPlatformBasedonGlycolChitosan–CoatedLiposomes.Small.2015Oct1;11(37):4870-4.
5. Silva-LópezEI,EdensLE,BardenAO,KellerDJ,BrozikJA.ConditionsforliposomeadsorptionandbilayerformationonBSApassivatedsolidsupports.Chemistryandphysicsoflipids.2014Oct31;183:91-9.
6.HazraM,SinghSK,andRayS.SurfaceModificationofLiposomalVaccinesbyPeptideConjugation.JournalofPharmaSciTech,2011;1(1):41-47.
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1、直接竞争,标记抗原,与检测样品中的抗原竞争抗体。
2、间接竞争,标记抗体,固相抗原与液相抗原(样品)竞争标记抗体。
3、定义
间接竞争法的模型:包被抗原,用HRP-抗体与样本一起加入。样本中的Ag与Solid-Ag竞争HRP-Ab,固相吸附的HRP-Ab与样本中的Ag浓度成反比。
直接竞争法的模型:包被抗体,用HRP-抗原与样本一起加入。样本中的Ag与HRP-Ag竞争Solid-Ab,固相吸附的HRP-Ag与样本中的Ag浓度成反比。
4、竞争法的理论基础:是限量抗体。只有在限量抗体基础上,两种抗原才会形成竞争关系。
5、、间接竞争法具备较高灵敏度原因。
直接竞争法里,标记抗原与待测抗原均是液相,与抗体的结合机会是一样的,例如有1份标记抗原与1份待测抗原竞争1份抗体,那么有50%的标记抗原能与抗体结合,所以标记抗原的相对结合率为50%。间接法里,固相抗原与抗体的接触面积较小,固相抗原与待测抗原的结合抗体机会是不平等的,接近顺序饱和法,即只有与待测抗原结合剩余的抗体才会与固相抗原结合,同样有1份固相抗原与1份待测抗原竞争1份抗体时,基本上抗体会被待测抗原中和掉,与固相抗原结合的抗体非常少。固相抗原的相对结合率为0%。因此,间接法的抑制曲线斜率会大于竞争法。
因为抑制率越大则斜率越大,从而灵敏度越大。(假设零管变异5%,以两倍SD为灵敏度限,则为90%相对结合率,则间接法可以在较低的待测抗原浓度达到这一相对结合率,因此灵敏度要高。)
在进行系统放大时,间接法一般可以使用酶标二抗。因为二抗可以针对抗体的多个部位,所以存在放大效应,从而能提高间接法的灵敏度。直接法一般难以进行放大,常用的有生物 素化抗原与酶标亲和素,但模式上似乎不存在放大效应。
6、间接法的高灵敏度难以实现的原因:
双抗体 夹心的免放(IRMA)模式刚出现时,也被模型证明灵敏度优于竞争法的放免(RIA),原因也是较大的斜率,但是IRMA的高灵敏度一直到单抗发展后才得以实现。
采用抗-HBe抗体包被反应板,加入校准品及被测样本,同时加入定量HBeAg中和抗原,经过振荡孵育,洗板后再加入铕标记的抗-HBe,若标本中抗-HBe浓度高,HBeAg将被大量中和,使最后形成的抗-HBe-HBeAg-铕标记抗-HBe复合物减少。增强液(β-NTA)将标记在抗体上的Eu3+解离到溶液中,Eu3+和增强液中的有效成分形成高荧光强度的螯合物,荧光强度和样本中的抗-HBe浓度成反比。