High-performance affinity capture-removal of bacterial pyrogen from solutions

Transcription

1 Journl of Chromtogrphy B, 759 (2001) locte/ chromb High-performnce ffinity cpture-removl of bcteril pyrogen from solutions Jek Ling Ding *, Yong Zhu, Bow Ho, b Deprtment of Biologicl Sciences, Fculty of Science, Ntionl University of Singpore, 10Kent Ridge Rod, Singpore , Singpore b Deprtment of Microbiology, Fculty of Medicine, Ntionl University of Singpore, 10Kent Ridge Rod, Singpore , Singpore Received 3 Jnury 2001; received in revised form 26 Mrch 2001; ccepted 20 April 2001 Abstrct Synthetic peptide S3D hs high ffinity for bcteril endotoxin or lipopolyscchride (LPS). Under tested conditions of ph nd M NCl, the ffinity constnt, KD rnged from 2?10 to 2?10 M. A novel ffinity mtrix bsed on peptide S3D ws developed for removl of LPS from solutions such s: wter; buffers with wide rnge of ionic strength nd ph; medium for cell culture; nd protein solutions under optimized conditions. At strting LPS of 100 EU/ml, post-purifiction level below EU/ ml ws chieved Elsevier Science B.V. All rights reserved. Keywords: Affinity dsorption; Pyrogen; Lipopolyscchrides; Endotoxins 1. Introduction e.g., glucose, slts, chemotherpeutics, ntibiotics nd rdiophrmceuticls. Other pproches include Endotoxin or lipopolyscchride (LPS) is n integ- two-phse extrction nd different kinds of dsorprl component of the outer cell wll of grm-negtive tion methods for protein solutions [3]. For removl bcteri. It cuses pyrogenic nd endotoxic shock of LPSs from solutions of cell products, especilly rections in mmmls [1,2]. Development of tech- proteins, dsorption methods hve proven to be the niques nd mterils for decontmintion of endo- most effective [4]. Different dsorbents hve been toxin from phrmceuticl nd prenterl fluids is developed with vrying success. These re () nion therefore crucil for helth cre products, nd hs exchngers such s diethylminoethne (DEAE), (b) remined trget of much reserch effort. Vrious ffinity mtrix using polymyxin B-immobilized methods hve been developed to chieve this im for Sephrose, histidine-immobilized Sephrose, polydifferent trget solutions [3]. These methods involve (ethyleneimine) (PEI), poly-l-lysine (PLL), poly-lultrfiltrtion for decontmintion of wter nd solu- histidine (PLH) nd minted poly(g-methyl L-gluttions contining products of low moleculr mss, mte) (PMLG), nd (c) immunoffinity mtrix [3,5]. However, mny of these dsorbents, prticulrly, the *Corresponding uthor. Tel.: ; fx: ion exchngers, re not menble to opertions under 486. wide rnge of ph nd ionic strength. Furthermore, E-mil ddress: dbsdjl@nus.edu.sg (J.L. Ding). there is compromise to the efficiency of LPS / 01/ $ see front mtter 2001 Elsevier Science B.V. All rights reserved. PII: S (01)

2 238 J.L. Ding et l. / J. Chromtogr. B 759 (2001) removl over protein recovery. This problem is rtionle for choosing DADPA-immobilized grose excerbted by poor clernce fctor of LPS when mtrix is bsed on the considertions of lrge pore the feed concentrtion is low, which is common size nd hydrophilicity of grose, to minimize nonproblemtic endotoxin contmintion level [3]. specific binding nd llow fst perfusion. Further- In this work, we hve developed novel nd more, the extended DADPA spcer rm of 12 toms specific endotoxin dsorbent using synthetic m- is useful for immobilizing smll peptides which my phipthic ctionic peptide, S3D, which is derived otherwise be stericlly hindered upon immobilizfrom one of the LPS binding domins of horseshoe tion. This llows more spce for the peptide LPS crb Fctor C [6 8]. Fctor C is highly sensitive to interction. EDC ws used to couple the C-terminl trce levels of LPS. LPS-induced ctivtion of Fctor crboxyl of the S3D peptide to the mine group of C triggers cogultion cscde in the limulus DADPA, forming very stble mide bonds. For moebocyte lyste [9 11]. At lest two highly comprison of efficiency of LPS removl, Detoxispecific LPS binding sushi domins in Fctor C hve Gel (Pierce) ws used. been chrcterized [12], nd four peptides with high The LAL Kinetic-QCL ssy kit ws from ffinity for LPS [13] nd ntimicrobil ctivity [14] BioWhittker, USA. LPS (from Escherichi coli hve been designed bsed on the sequences of the 055:B5), lipid A in 1,49-diphosphoryl form (from E. core LPS binding regions of these domins, of which coli F-583) nd sodium deoxycholte (DOC) were S3D is one exmple. S3D lso binds lipid A, the from Sigm. Fluorescein isothiocynte (FITC)- toxic portion of LPS, in simple, stoichiometric nd lbeled LPS (from E. coli 055:B5) ws purchsed non-coopertive wy with Hill s coefficient of 0.91 from List Biologicl Lbs., USA. Bovine serum [13]. This peptide is non-cytotoxic nd non- lbumin (BSA), ovlbumin nd chymotrypsinogen A hemolytic. A detiled profile of binding ffinity of were purchsed from Phrmci Biotech. Insect cell S3D for LPS under vrious ph nd ionic strength culture medium Sf-900 II SFM ws from Gibco conditions is presented in this study. As potentil BRL, USA. All other chemicls were of nlyticlcndidte dsorbent in selective binding nd removl regent grde from Sigm. Pyrogen-free wter used of endotoxin from fluids nd biologicl preprtions, for buffer preprtions ws from Bxter Helthcre, S3D ws covlently conjugted to diminodipro- Austrli. pylmine (DADPA) immobilized grose to develop specific nd selective ffinity mtrix. The cpbility of the resulting ffinity mtrix to remove LPS 2.2. Mesurement of the binding ffinity of S3D from liquid solutions ws tested under vrious ph peptide with lipid A under different conditions nd ionic strength. The efficcy of this mtrix in endotoxin removl ws compred with other reported Surfce plsmon resonnce (SPR) sensorgrms dsorbents. were recorded to monitor the binding between S3D nd lipid A under different conditions, in rel time mode on BIAcore 2000 biosensor instrument. Lipid A t 1.0 mg/ml in pyrogen-free wter ws immobil- 2. Experimentl ized on HPA sensor chip (Phrmci, Sweden) ccording to the mnufcturer s specifiction. Stock 2.1. Mterils solution of S3D t1mm in pyrogen-free wter ws diluted with different buffers to series of con- S3D (NH2-HAEHKVKIKVKQKYGQFPQGTEV- centrtions, nd injected into the flow cell t rte of TYTCSGNYFLM-COOH) ws synthesized nd 30 ml/ min, using the diluent s running buffer. The purified by Genemed Synthesis, USA. An endotoxin- binding response ws mesured s function of removing ffinity mtrix ws developed by using time, nd kinetic constnts were clculted from the 1 - ethyl (3 - dimethylminopropyl)crbodiimide sensorgrms using BIA evlution softwre version (EDC) s coupling gent to link S3D to DADPA- 3.1 (Bicore, Sweden). For regenertion of the chip immobilized grose gel (Pierce, USA). The surfce, the bound peptide ws removed by injection

3 J.L. Ding et l. / J. Chromtogr. B 759 (2001) of 100 mm of NOH solution for 1 min or in 1 min room temperture. The mixtures were then cenpulses until bseline SPR ws chieved. trifuged t 100 g for 1 min to pellet the beds. The superntnts were re-centrifuged t g for Covlent conjugtion of S3D to DADPA- min to fully pellet residul beds. LPS concenimmobilized grose beds trtions of the solutions before nd fter incubtion with beds were mesured to clculte the removl DADPA-immobilized grose ws used to prepre efficiencies. When proteins were involved in the the S3D-ffinity mtrix. S3D ws dissolved t 2 dsorption ssy, the protein concentrtions before mg/ ml in conjugtion buffer [0.1 M 2-(N-morpho- nd fter incubtion were lso mesured to clculte lino)ethnesulfonic cid (MES), 0.9% NCl, ph 4.7] the protein recovery. nd used for conjugtion by EDC with DADPAgrose in column, following the procedure of the 2.6. Quntifiction of LPS nd proteins supplier. After 3 h t room temperture, the column ws drined nd the flowthrough nd subsequent LPS ws quntified either by the LAL ssy, eluent frctions of 1 ml ech were collected. The which involved chromogenic kinetic test using bsorbnce t 280 nm (A 280 nm) ws mesured to pyrogen-free 96-well microssy plte [12], or by clculte the totl mount of peptide immobilized to fluorometry with luminescence spectrometer LSthe mtrix. After regenertion with 5 column vol- 50B (Perkin-Elmer) when FITC-lbeled LPS ws umes of 1% DOC nd wshing with pyrogen-free used. In fluorometry, smples in microssy plte wter, the column or beds were redy for use. When were excited t 490 nm with slit of 2.5 nm, nd the not in use, the peptide-conjugted beds were stored fluorescence intensity t 525 nm ws mesured t t 48C with 0.02% of sodium zide. emission slit of 2.5 nm; 515 nm filter ws used to reduce bckground emission. The protein concen Fluorescence microscope observtion of LPS trtion in smple solutions ws determined by bbinding sorbnce t 280 nm with spectrophotometer DU 650 (Beckmn). The binding of FITC-lbeled LPS to S3D conjugted ffinity beds ws observed under fluorescence microscopy. A System Microscope BX60 (Olympus, 3. Results Jpn) connected with video cmer JVC KY- F55BE (JVC, Jpn) to personl computer instlled 3.1. Affinity of S3D for lipid A mesured by rel with imge softwre AcQuis (Syncroscope, UK), time interction on the BIAcore 2000 ws used for the FITC fluorescence observtion nd digitlized picture tking. Blue light ws used for S3D is bsic (isoelectric point, pi 9.6) nd excittion with the filter cut-off t 380 nm. All mphipthic peptide [12]. The binding ffinity of digitl pictures were recorded t sme equipment S3D-peptide with lipid A, ws mesured under settings. vrious conditions of ph nd ionic strength by SPR technology in rel time mode on the BIAcore LPS dsorption ssy Fig. 1 shows series of sensorgrms obtined by injecting the peptide t different concentrtions into After equilibrtion in the pproprite buffer, the the flow cell which ws coted with lipid A, while LPS-binding cpcity of S3D coupled beds ws 0.4 M NCl ws used for both the solvent of the tested btchwise, under different conditions of ionic peptide nd running buffer. Sensorgrms under vristrength nd ph. An liquot of 500 ml of stndrd ous buffer conditions were obtined in n identicl LPS or FITC-LPS solution, in the bsence or pres- wy (dt not shown). Kinetic constnts (Tble 1) ence of 0.5 mg/ml of protein (either BSA, ovl- were clculted from the sensorgrms by fitting with bumin, or chymotrypsinogen A), ws incubted with 1:1 Lngmuir model [12]. 50 ml of wet ffinity beds, in rottion for 2 3 h t In the low slt buffers, t identicl ionic strength,

4 240 J.L. Ding et l. / J. Chromtogr. B 759 (2001) ph significntly ffects the ffinity, which rnges NOAc, ph 5.0. Even the highest KD of 5.6?10 M 29 from the lowest KD of 2.3?10 M t ph 5.0 to the t ph 9.1 (Tble 1), is still comprble to ntibody 26 highest KD of 5.6?10 M t ph 9.1. Increse in ph ntigen ffinity. This high ffinity results from decreses the binding rte constnt k (from the synergism between electrosttic nd hydrophobic highest 1.4?10 M s t ph 5.0 to the lowest 22 interctions [4] nd possibly, lso the structurl M s t ph 9.1), with concomitnt increse in dpttion of peptides upon binding with LPS [13] the dissocition rte (from the slowest 3.2?10 s t ph 5.0 to the fstest 1.2?10 s t ph 9.1). This 3.2. LPS ffinity mtrix preprtion nd shows tht the initil driving force for the binding is regenertion vi electrosttic interction, which is strengthened by lowering of ph becuse of increse in the ctionicity Bsed on the verstility of S3D in binding lipid A of S3D. However, while incresing the ionic strength under vrious ph nd ionic strength, its ppliction (from 0 to 0.4 M NCl), only n insignificnt hlf in LPS removl from solution hs led us to prepre order of mgnitude difference in KD ws observed, S3D conjugted ffinity mtrix for LPS. Using 2 27 between the lowest K (4.3?10 M, t 50 mm mg/ ml of peptides, coupling efficiency of 50 70% D 26 NCl) nd the highest K D (2.1?10 M, t 400 mm). ws routinely chieved. The ffinity beds strongly Also there is no correltion between the increse of dsorb FITC-lbeled LPS in wter (Fig. 2), reionic strength with the chnge of the rte constnts sulting in lmost 100% of LPS-free solution. The (k, k d). Since electrosttic nd hydrophobic interc- beds used cn be efficiently regenerted by mild tions re the mjor forces tht influence the ffinity conditions of 1% DOC (Fig. 2b) or 2 M NCl (Fig. of LPS nd peptide, this indictes significnt 2c). There ws virtully complete dissocition of contribution of hydrophobic interction, which com- FITC-LPS from ffinity beds. penstes for the wekening of electrosttic inter- In btchwise ssy, FITC-LPS bound to beds t ction due to slt, nd further stbilizes the binding the concentrtion of 5 mg/ml cn be removed t 75% of S3D with lipid A. The importnce of hydrophobic efficiency from beds by using 10 volumes of 1% interctions between the cyl chins of LPS nd DOC in single incubtion, for 1 2 h t room endotoxin-binding peptide hs been verified by temperture. Using 10 volumes of 2 M NCl, 80% Frecer et l. [15]. regenertion efficiency ws chieved. The regener- Hence, peptide S3D, which is designed ccording ted ffinity beds were tested for its repeted usge to the LPS binding domin of Fctor C, hs high in LPS binding. Under the sme condition of 20 mm ffinity for lipid A, over wide ph nd ionic strength. Tris, ph 6.8, 50 mm NCl, the beds tht were used Under our tested conditions, the lowest dissocition once t the loding mount of 5 mg/ml of FITCconstnt, K 29 of 2.3?10 M ws observed in 20 mm LPS, were compred with the freshly prepred beds. D 26 Tble 1 Affinity of S3D for lipid A t different ph nd ionic strength Solvent condition k (M s ) k d (s ) K A (M ) K D (M) Wter 4.1?10 2.4?10 1.7?10 5.9?10 50 mm NCl 1.8?10 7.8?10 2.3?10 4.3? mm NCl 3.7?10 4.0?10 9.3?10 1.1? mm NCl 3.3?10 6.8?10 4.9?10 2.1?10 20 mm NAc, ph ?10 3.2?10 4.4?10 2.3?10 20 mm Tris HCl, ph ?10 7.2?10 9.0?10 1.1?10 20 mm Tris HCl, ph ?10 1.8?10 5.6? Binding of peptide S3D with diphosphoryl lipid A (E. coli F-583) immobilized on HPA chip surfce ws monitored in rel time mode on BIAcore Affinity constnts were clculted from the sensorgrms using 1:1 (Lngmuir) binding model to fit with BIA evlution 3.1 (k nd k re rte constnts; K nd K re equilibrium constnts). d A D

5 J.L. Ding et l. / J. Chromtogr. B 759 (2001) Fig. 1. SPR sensorgrms obtined on the BIAcore 2000 using lipid A (E. coli F-583)-coted HPA chip show the rel time biointerction between S3D nd lipid A in the presence of 0.4 M NCl. S3D t series of indicted concentrtions ws injected into the flow cell t flow-rte of 30 ml/min for 2 min. In both cses, n LPS removl efficiency of 80% ws mintined Chrcteristics of LPS binding by S3D ffinity beds Since SPR nlysis showed tht S3D exhibited high ffinity for lipid A under wide ph nd ionic strength, the robustness of LPS binding of the ffinity beds ws tested under vrious ionic strength nd ph. Fig. 3 shows tht, the LPS binding bility of S3D decreses with increse in ionic strength of the buffer, gin indicting tht the initil interction of LPS with the peptide is minly driven by electrosttic interction between the negtively chrged phosphte groups of lipid A moiety nd positively chrged lysine residues of S3D. From 50 to 400 mm NCl, the LPS removl efficiency ws reduced by mere 25%. This indictes significnt contribution of the hydrophobic interction between LPS nd peptides, s proven by BIAcore experiments using lipid A, thus suggesting the potentil of S3D to mke n ffinity mtrix which would be less dependent on low slt condition thn other trditionl nion exchnger like DEAE [3]. As shown in Fig. 3b, incresing the ph from 4 to 9.1 did not significntly lter the LPS binding efficiency. This indictes wide ph tolernce of the peptide ffinity beds. From ph 4 to 6.8, which is below pk2 of 8.2 of the lipid A phosphte group settings. Fig. 2. Fluorescence microscopy shows the binding of LPS to S3D ffinity beds followed by its dissocition from the beds by 1% of DOC or 2 M of NCl. Blue light (cut-off t 380 nm) ws used for excittion. () Beds with bound FITC-LPS; (b) beds fter tretment with 1% DOC; nd (c) beds fter tretment with 2 M NCl. All digitl pictures were tken t the sme equipment

6 242 J.L. Ding et l. / J. Chromtogr. B 759 (2001) Selective removl of LPS from protein solutions While the electrosttic nd hydrophobic interctions between proteins nd LPS my complicte the removl of LPS from protein solutions, nd different solvent conditions my render further complexity, the ctul output would be difficult to predict. Different process conditions need to be tested for optimiztion of trget protein solution, often t the expense of compromising protein recovery nd LPS removl efficiency [3]. In this work, 0.5 mg/ml of BSA (pi 4.7), ovlbumin (pi 4.6) nd chymotryp- Fig. 3. LPS binding by peptide S3D ffinity beds under different () ph nd (b) ionic strength. Aliquots of 0.5 ml of 5 mg/ml of sinogen A (pi 9.5) spiked with FITC-lbeled LPS t 4 FITC-LPS in buffer t indicted ph (either 20 mm sodium 5 mg/ml (5?10 EU) were used to test the bility of cette, ph 4.0 nd 5.0, contining 50 mm NCl or 20 mm S3D conjugted grose beds for selective removl Tris HCl, ph 6.8 nd 9.1 contining 50 mm NCl), or ionic of LPS from protein solutions. strength (20 mm Tris HCl, ph 6.8, contining indicted con- As shown in Fig. 4, when ph ws fixed t 6.8, the centrtions of NCl), were incubted with 50 ml of ffinity beds in rottion for 2 3 h. Fluorescence intensities of the smples LPS removl efficiency from ll three protein solu- before nd fter tretment with beds were mesured to clculte tions consistently decresed with increse in slt the LPS binding efficiencies. concentrtion. While the recovery efficiency of bsic protein, chymotrypsinogen A, ws mintined t 90% over the chnge of ionic strength, tht of cidic BSA nd ovlbumin drsticlly dropped with the decrese of slt concentrtion. For chymotryp- [16], the net negtive chrge of LPS would not sinogen A, low slt concentrtion of 50 mm NCl chnge while the net positive chrge of peptide enbled 80% LPS removl while chieving conwould be reduced from 6.28 to 3.24 (clculted using comitnt protein recovery of 90%. Thus, the lower DNAMAN version 4.15 from Lynnon BioSoft). The the ionic strength, the more efficient is the LPS increse in ph would expectedly led to the weken- removl from chymotrypsinogen solution. For BSA ing of electrosttic interction between the negtively nd ovlbumin, compromise hs to be mde with chrged phosphte groups of LPS nd the positively neutrl ph conditions nd 200 mm NCl to chieve chrged peptides, nd hence decreses the LPS optimum removl of LPS while mintining 70% binding cpcity of the peptide. However, this ws recovery of protein. not observed, nd it strongly indictes tht the Using fixed slt concentrtion of 50 mm, while hydrophobic interction between LPS nd peptide chnging the ph, the LPS removl efficiency from contributes significntly to the binding. From ph 6.8 ll protein solutions did not chnge significntly to 9.1, the phosphte group in lipid A would increse long the ph shifts (Fig. 5). This trend is similr to one net negtive chrge, nd the positive chrge of removl of LPS in Tris buffer (see Fig. 3), where the peptide S3D would further reduce from 3.24 to 80% removl of LPS ws chieved. While the We observed significnt increse by 15% in recovery efficiency of bsic protein, chymotrypsino- LPS removl when ph ws shifted from 6.8 to 9.1. gen A ws mintined t 90% long the chnge of This is ttributble to the enhnced repulsive force ph, tht of cidic BSA nd ovlbumin dropped between phosphte groups, thus reducing the ggre- drsticlly with the incresing ph. At ph 4 which is gtion of LPS. Bsed on our results, the S3D ffinity ner the pi of BSA nd ovlbumin, 80 90% of beds cn be efficiently employed for LPS removl protein recovery cn be reched without significnt over wide ph rnge. loss in LPS removl efficiency ( 80%). Considering

7 J.L. Ding et l. / J. Chromtogr. B 759 (2001) Fig. 4. LPS removl nd protein recoveries from protein solutions under different ionic strength: () BSA, (b) ovlbumin nd (c) chymotrypsinogen A. Aliquots of 0.5 ml of protein solutions t 0.5 mg/ml contining 5 mg/ml of FITC-LPS in 20 mm Tris HCl, ph 6.8 with indicted concentrtions of NCl were incubted with 50 ml of ffinity beds in rottion for 2 3 h. A 280 nm nd fluorescence intensities of the smples before nd fter tretment with beds were mesured to clculte the LPS removl efficiencies nd protein recoveries, respectively. the intrinsic sticky property of BSA s universl crrier molecule, this level of LPS removl is respectble. This efficiency cn be further improved by the use of EDTA (see Section 3.5) Removl of low problemtic concentrtions of LPS from vrious solutions The pilot results presented bove demonstrte tht Fig. 5. LPS removl nd protein recoveries from protein solutions under different ph conditions: () BSA, (b) ovlbumin nd (c) chymotrypsinogen A. Aliquots of 0.5 ml of protein solutions t 0.5 mg/ml contining 5 mg/ml of FITC-LPS in buffer t indicted ph were incubted with 50 ml of ffinity beds in rottion for 2 3 h. A 280 nm nd fluorescence intensities of the smples before nd fter tretment with beds were mesured to clculte the LPS removl efficiencies nd protein recoveries, respectively. The buffers used were 20 mm sodium cette t ph 4.0 nd 5.0, nd 20 mm Tris HCl t ph 6.8 nd ph 9.1. All buffers were supplemented with 50 mm NCl.

8 244 J.L. Ding et l. / J. Chromtogr. B 759 (2001) S3D peptide ffinity mtrix cn remove LPS from For the cell culture medium (Sf-900 II SFM), both wter nd protein solutions, with good protein re- spiked levels of 10 nd 1000 EU/ ml were reduced to covery, nd it is less dependent on low ionic below the detection limit EU/ ml, with no strength. Subsequently, we tested its performnce t pprecible loss of medium components. removing LPS t the usul problemtic contmintion level, which is reported to be up to 100 EU/ ml 3.6. Comprison with commercilly vilble gel for vrious biologicl preprtions fter the initil mtrix for endotoxin removl steps of purifiction [3]. Thus, we further tested buffers, protein solutions nd cell culture medium A comprison of LPS removl efficiency between (Tble 2). S3D peptide-ffinity mtrix nd the commercilly For 20 mm Tris, ph 6.8 contining 50 mm NCl vilble endotoxin removing gel, with which polynd LPS rnging from 0.1 to 100 EU/ml, the LPS myxin B is immobilized, ws crried out by minilevel ws reduced to below the detection limit of column chromtogrphy. Tble 3 shows tht while EU/ml from strting LPS level of 0.1, 1 nd both gels exhibit similr protein recovery of 90%, 10 EU/ml, nd to 0.01 EU/ml from 100 EU/ml, in the S3D peptide-ffinity mtrix displyed superior 4 which cse clernce fctor (CF) greter thn 10 LPS removl efficiency. Purifiction through S3D ws chieved. 4 peptide-ffinity column yielded CF of 10 for the For 0.5 mg/ml of BSA nd chymotrypsinogen A, culture medium Sf-900 II SFM which contined spiked with 10 EU/ ml of LPS, the LPS removl spiked level of 1000 EU/ ml LPS. When spiked t 10 efficiencies were t CF of 2.7 nd 59, respectively. EU/ ml, LPS ws removed to below the detection However, in the presence of 5 mm EDTA the limit. Using btchwise incubtion with S3D peptideperformnce ws improved by 10-fold for BSA nd ffinity gel, purifiction of Sf-900 II SFM spiked threefold for chymotrypsinogen A, where LPS levels with 1000 EU/ ml LPS ws further improved to were reduced to 0.3 nd 0.06 EU/ ml, respectively. below detection limit of EU/ ml. In com- The enhncement by EDTA is ttributble to its prison, Detoxi-Gel showed much poorer perform- solubiliztion effect on protein-bound LPS [3]. nce. Tble 2 Removl of LPS from vrious solutions with problemtic low levels of LPS contmintion b b b b Tris buffer BSA Chym. A Medium Before tretment (EU/ ml) , 1, After tretment (EU/ ml),0.01, ,0.005,0.005 d (1EDTA) d (1EDTA) c c c Clernce fctor (CF).104 N/A N/A N/A LPS dsorption experiments were crried out in btchwise mnner. Aliquots of 0.5 ml of ech smple solution contining LPS t indicted concentrtions were treted with 50 ml of wet ffinity beds in rottion for 2 3 h. LPS concentrtion of smples before nd fter tretment ws mesured by LAL chromogenic ssy. A 280 nm ws lso mesured to evlute the recovery of components in the medium. b Tris buffer: 20 mm Tris HCl, ph 6.8 contining 50 mm NCl; BSA: BSA in 20 mm Tris HCl, ph 4.0 contining 50 mm NCl; Chym. A: chymotrypsinogen A, in 20 mm Tris HCl, ph 9.1 contining 50 mm NCl; medium: Sf-900 II SFM for insect cell culture, ph 6.5. c EU/ml is the detection limit of LAL chromogenic ssy. d EDTA t stock concentrtion of 0.5 M (ph 8.0) ws dded to the protein LPS bed mixture to chieve finl concentrtion of 5 mm before incubtion.

9 J.L. Ding et l. / J. Chromtogr. B 759 (2001) Tble 3 Comprison of LPS removl from cell culture medium Sf-900 II SFM by S3D peptide-ffinity gel nd Detoxi-Gel Strting level of LPS After S3D peptide-ffinity column After Detoxi-Gel column (EU/ml) (EU/ml) (EU/ml) , A column of 1 ml of S3D peptide-ffinity gel with exctly the sme dimensions s tht of Detoxi-Gel endotoxin removing column ws pcked. After wshing with 5 ml of 1% DOC nd three times with 5 ml of wter, the columns were loded with 10 ml of cell culture medium Sf-900 II SFM contining 10 or 1000 EU/ml of LPS. After flowing twice through the respective columns by grvity, LPS concentrtion ws mesured by LAL chromogenic ssy. A ws lso mesured to evlute the recovery of components in the medium. 280 nm 4. Discussion The bility of S3D peptide dsorbent to selectively dsorb LPS is ttributble to its specific high ffinity Owing to the pyrogenic effect of endotoxin, mny for LPS, with KD rnge from 10 to 10 M phrmceuticl preprtions hve to meet threshold under tested rnge of ph nd ionic strength. This of endotoxin contmintion level, which is usully selective mtrix is prticulrly superior t the low very low. For exmple, it is essentil to eliminte problemtic LPS contmintion levels. LPS to t lest concentrtion lower thn 100 pg/ ml Although some published reports hve docu- ( 1 EU/ ml) from fluids used for intrvenous in- mented dsorbents tht cn remove LPS with CF up jection [5,17]. To dte, there is no single generl 5 to 10 t the loding level of mg/ ml, t the low nd method vilble for the removl of endotoxin from problemtic LPS contmintion level (,100 EU/ solutions. Methods used for decontmintion of ml), the S3D ffinity dsorbent displyed more wter, such s ultrfiltrtion, hve little effect on superior performnce. Furthermore, hving no reendotoxin levels in protein solutions [3]. Vrious quirement for low ionic strength nd yet, wide ph techniques described in the ptent literture re tolernce, mke S3D-peptide ffinity mtrix n extilored to meet specific product requirements nd cellent novel LPS removl dsorbent with high not brodly pplicble. selectivity nd specificity. Unlike other reported Generlly, the high endotoxin concentrtions in dsorbents which re often toxic, S3D lcks cytotoxthe strting mterils used for the production of icity nd it is non-hemolytic [12], thus further phrmceuticls cn be reduced to bout 100 EU/ ml supporting its ppliction in the pyrogen clen-up or even lower by product purifiction steps without industry. specil tretment [3]. Even much lower remining endotoxin contents my be relized. Bischoff et l. [18] purified recombinnt 1-ntitrypsin in three- Acknowledgements step procedure, employing ultrfiltrtion, nion-exchnge nd immobilized metl chelte ffinity chro- We thnk Ntionl Science nd Technology Bord mtogrphy. As reviewed by Petsch nd Anspch for finncil support (NSTB/ LS/ 99/ 004). [3], most of those reported dsorbents cn remove 3 5 LPS with clernce fctor from 10 to 10 t the mg/ ml of LPS feed level, but t the lower feed References levels, the performnce is usully not stisfctory, with either low clernce fctor (5 200), or severe [1] S.I. Morse, Adv. Appl. Microbiol. 20 (1976) 9. protein loss. [2] D. Fumerol, Cell. Immunol. 58 (1981) 216. We hve demonstrted tht S3D ffinity mtrix [3] D. Petsch, F.B. Anspch, J. Biotechnol. 76 (2000) 97. [4] S. Minobe, T. Wtnbe, T. Sto, T. Tos, J. Chibt, J. cn be used s n efficient nd re-usble selective Chromtogr. 248 (1982) 401. dsorbent for the removl of endotoxin from wter, [5] C. Hirym, M. Skt, M. Nkmur, H. Ihr, M. buffers, protein solutions nd cell culture medium. Kunitk, M. Todokoro, J. Chromtogr. B 721 (1999) 187.

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