in the following detailed description , reference is made to the accompanying drawings , which form a part thereof . the illustrative embodiments described in the detailed description , drawings and claims are not meant to be limiting . other embodiments may be utilized , and other changes may be made , without departing from the spirit or scope of the subject matter presented here . the present technology is also illustrated by the examples herein , which should not be construed as limiting in any way . a . isolation of aβ - single - domain antibody 1a ( aβ - sdab 1a , structure 1 in fig2 ) all animals ( llamas ) were treated following nih guidelines . first , the animals were given a complete physical examination by our veterinarian , dr . linda byer , who also drew some pre - immunization blood . immunization was then started with aβ 1 - 35 synthetic peptide ( 200 ug ) in gerbu pharma adjuvant ( 1 ml ). one month after the initial priming injection , six biweekly boosters were administered at 200 ug / injection . after the fourth booster , about 20 ml blood was drawn and serum examined for antibody titer with antigen coated 96 - well elisa plate . after immunization , ˜ 200 ml blood was drawn from the animal . half of the blood was used to isolate single - domain aβ - antibody ( polyclonal ) with the methods below in sections a . 2 - 4 . the second half of the blood was used to isolate peripheral blood lymphocytes ( pbls ) to prepare total rna followed by its reverse transcription to cdna , which was then ligated into the phage vector to generate phage - display cdna library ( section d ). after immunization , 100 ml from each blood sample drawn was processed to fractionate sdabs ( mw : ˜ 90 kda ) from the classical antibodies ( mw : ˜ 160 kda ). briefly , the serum (˜ 50 ml ) was concentrated on an millipore - amicon ultra - 15 concentrator , molecular weight cutoff 50 kda , by spinning the device at 4000 g , until most of the low molecular weight species passed through the membrane . the thick viscous yellow retentate (˜ 25 ml ) was extracted with chloroform ( 3 × 25 ml ) to remove fatty substances , which had contributed to the viscosity of the retentate . the resulting crude product ( 2 × 10 ml ) was size fractionated on superdex - 200 ( 2 . 5 cm × 100 cm ) using 1 × pbs as eluant . the fractions were monitored by reading od 280 on a beckman du - 640 spectrophotometer . after examining the fractions on a 12 % sds - page gel , the fractions whose products correspond to the molecular weight of ˜ 90 kda were pooled , concentrated and the protein concentration was measured by checking its od 280 . 10 mg of immunogen aβ1 - 35 , dissolved in 5 ml of conjugation buffer , 0 . 1 m nahco 3 / 0 . 15m nacl , ph 8 . 5 , was conjugated with cyanogen - bromide activated sepharose ( 2 gm ), which had been washed with 200 ml of ice - cold 1 mm hcl . the reaction was allowed to proceed for 2 hours while the resin was allowed to gently rock on a rocker . after centrifugation , the supernatant of the reaction mixture was examined by its od 280 reading , which indicated that essentially all of the immunogen had been consumed . the resin was then washed with ph 8 . 5 conjugation buffer ( 3 × 20 ml ), and then blocked with 1 m tris . hcl , ph 8 . 3 ( 10 ml ), room temperature for 2 hours . after washing the resin with 0 . 1 m nahco 3 / 0 . 5m nacl , ph 8 . 5 , the resin was washed with 0 . 1 m sodium citrate ( 50 ml ), ph 2 . 8 and equilibrated with 20 mm sodium phosphate buffer , ph 7 . 0 , before using the resin for affinity purification . the crude mixture of sdabs obtained after size fractionation on superdex - 200 , which was more than 98 % free of full - length conventional iggs , was allowed to incubate with the affinity column in 1 × pbs , at room temperature for one hour . after one hour , the unbound material was allowed to drain through the column and the column washed with pbs until all the unbound proteins had been washed off the column . the bound aβ - sdab was eluted off the column with ph 2 . 8 buffer ( 0 . 1 m sodium citrate , 0 . 2 um filtered ). the eluant was adjusted to ph 7 . 2 by adding 1 m tris . hcl , ph 9 . 0 , and concentrated on millipore - amicon ultra - 15 concentrators ( 30 kda molecular weight cutoff ). the retentate was buffer exchanged to 1 × pbs and stored at − 20 ° c . to obtain 1 . 65 mg of aβ - sdab 1a ( fig2 , structure 1 , table 1 , variant : r = 1 ). its protein concentration was determined using pierce &# 39 ; s bca protein assay kit . the sds - page analysis of the affinity purified aβ - sdab 1a is in fig3 . about 10 ug of the aβ - sdab 1a after each step was electrophoressed on 12 % sds - page gel after loading in sds - loading buffer . the electrophoresis was performed at 100 volts for one hour , the gel was stained in 0 . 04 % coomassie blue stain for 30 minutes at room temperature ( rt ). coomassie blue stained sds - page ( 12 %) protein gel of sequentially purified aβ - sdab 1a , panel d : 1 st and 2 nd purifications were on superdex - 200 ; 3 rd purification was done by affinity chromatography . b . synthesis of single - chain aβ - sdab 2a and epitope mapping of peptide composition 2a 1 . 0 mg of aβ - sd - ab 1a was dissolved in 400 ul of ph 7 . 4 pbs . to this solution was added 100 ul of 100 mm triethoxy carboxyl - phospine ( tcep ) in pbs to obtain a final concentration of 20 mm . the reaction mixture was incubated at 4 ° c . for 12 - 15 hours when gel electrophoresis ( 10 % sds - page ) showed a low molecular weight species with molecular weight of ˜ 50 kda . this product peptide composition 2a ( single chain of aβ - sdab 1a ) was isolated by gel filtration and tested by western and elisa . 96 - well microplates ( a1 - a12 through g1 - 12 wells ) were coated in triplicate with 600 ng per well of the following synthetic amyloid - peptide segments of aβ1 - 42 peptide in table 7 . after coating the plate at 4 ° c . for 12 hours , the antigens were discarded and the wells washed with deionized water ( 3 ×). the plate was blocked with 1 % bsa in 50 mm tris / 150 mm nacl , ph 7 . 5 for one hour . at the end of one hour , single - chain aβ - sdab , 2a , 1 . 0 ug diluted to 2500 ul with 1 % bsa / tris buffer was added to the top row ( 100 ul per well in triplicates ). after serial dilution all the way to 1 : 320000 ul , the plate was incubated with gentle shaking at room - temperature for 2 hours . at the end of 2 hour incubation , the plate was washed three times , 250 ul per well , with 0 . 05 % tween - 20 / pbs . after washing , the wells were incubated with 100 ul per well of goat - anti - llama - igg - hrp conjugate ( bethyl labs , texas ) 1 . 0 ug diluted to 10 ml of 1 % bsa in pbs . after one hour incubation , the plate was washed with 0 . 05 % tween as above . the washed well were treated with 100 ul of tmb substrate and the plate read at 370 nm . the highest antibody titer was detected with the peptide 1 - 16 amino acid long . subsequently , two synthetic peptide were synthesized : the 1 - 8 and 9 - 16 peptides from the amyloid beta peptide and the above elisa was again repeated with the plate coated with 600 ng of each of the peptide in triplicates . this time the peptide of the 9 - 16 amino acids gave the highest antibody titer , and no reaction took place with the sequence 1 - 8 mer . the epitope is between 9 to 16 amino acids with the following sequence : g y e v h h q k ( seq id no : 14 ). 1 . protease digestion of single - chain aβ - sdab 2a to obtain aβ - vab - hr ( aβ - vab with l1 or l2 linker variant ) generation of sepharose - endoproteinase glu - c conjugate . endoproteinase glu - c ( worthington biochemical corporation ), 4 mg , was conjugated to 250 mg of cnbr - activated sepaharose ( ge healthcare , catalogue # 17 - 0430 - 1 ) in ph 8 . 5 0 . 1 m nahco 3 / 0 . 5m nacl in 1 × 10 cm long spin fitted with a medium fritted disc , as described in section a . 3 : generation of an affinity column for enrichmant of aβ - sdab 1a . after conjugation , any unbound glu - c proteinase was removed by extensive washing of sepharose and the column was stored in 0 . 1 % nan 3 / pbs until used . the sepharose had swollen to about an 0 . 8 ml volume . digestion of single - chain aβ - sdab 2a and isolation of aβ - vab - hr . aβ - sdab 2a ( 1 mg , ˜ 11 nmols ) was dissolved in 1 . 0 ml of ph 7 . 5 0 . 1 m nahco 3 and added to the 0 . 8 ml of sepharose - glu - c conjugate . the reaction mixture was gently rocked on a rocker for 4 hours and the contents were collected by draining the column and washing it with 4 ml of the conjugation buffer , 0 . 1 m nahco 3 , ph 7 . 5 . the combined flowthrough was passed through aβ 1 - 35 - affinity column generated in section a . 3 . after washing off the unbound material , the bound aβ - vab - hr ( hr = hinge region ) from single - chain aβ - sdab 2a was eluted with ph 2 . 8 0 . 1 m sodium citrate and the product buffer exchanged to 1 × pbs , ph 7 . 4 . it was tested by elisa . general method for expression of engineered human antibody constant domains , ch1 , ch2 and ch3 . expression of engineered human constant domains ch1 , ch2 and ch3 was accomplished by buying the commercially available plasmid , pfuse - chig ( invitrogen : pfuse - chig - hg1 , pfuse - chig - hg2 , or pfuse - chig - hg3 ), and using them each for transformation of e . coli strain hb2151 cells . the cultures were grown in sb media at 37 ° c . until an optical density of ˜ 0 . 7 was obtained . expression was then induced with 1 mm iptg ( isopropyl - 1 - thio - b - d - galactopyranoside ) at 37 ° c . for 15 - 16 hours . the bacterial cells were harvested and resuspended in a culture medium containing 10 % of 50 mm tris . hcl , 450 mm nacl , ph 8 . 0 . polymyxin b sulfate ( pms ) was added to the culture medium , 1 : 1000 volume of pms : culture volume . after centrifuging the cell lysate at 15000 rpm for 45 minutes at 4 ° c ., the supernatant was purified by hitrap ni - nta column and tested for the respective expressed human constant domain by sds - page and western blot . general method for native chemical ligation of aβ - vab - hr to human constant domain . for native chemical ligation ( fig4 ), an unprotected peptide - alpha - carboxy thioester ( peptide 1 ) was reacted with a second peptide ( peptide 2 ) containing an n - terminal cysteine residue to form a natural peptide linkage between aβ - vab - hr and constant domain ch1 or ch2 or ch3 . aβ - vab - hr can be modified to be peptide 1 or peptide 2 . the ch1 ch2 , or ch3 domain is then modified to be the recipricol peptide 2 or peptide 1 . after the reaction , the aβ - vab - peg - human ch1 , ch2 , or ch3 was purified by size exclusion chromatography . general method for maleimido - thiol conjugation chemical linkage of aβ - vab - hr to human constant domain . for the maleimido - thiol conjugation reaction ( fig5 ), a thiolated peptide 2 conjugates to a maleimido - derivativized peptide 1 to create aliphatic linker between aβ - vab - hr and a ch1 , ch2 , or ch3 domain . aβ - vab - hr can be modified to be peptide 1 or peptide 2 . the ch1 , ch2 , or ch3 domain is then modified to be the recipricol peptide 2 or peptide 1 . peptide 1 was converted into a maleimido peptide by reacting in with 20 - fold excess of commercial nhs - peg - mal ( mw : 3000 da ) in ph 7 . 0 mops buffer ( 0 . 1 m mops / 0 . 15 m nacl ) for one hour at room temperature . after the reaction , excess pegreagent was removed by dialysis on vivaspin - 20 column with a mwco : 10 kda . to generate compatible reacting group , peptide 2 was thiolated with commercial traut &# 39 ; s reagent to obtain thiolated peptide 2 . 1 . 2 molar equivalent of thiolated peptide 2 which was reacted with maleimido derivatized peptide 1 at ph 6 . 8 at room temperature for 2 hours . after the reaction , the aβ - vab - peg - human ch1 , ch2 , or ch3 was purified by size exclusion chromatography . 1 . cloning of cdna encoding the aβ - sdab 1a : mrna isolation and reverse transcription the isolation of total rna from peripheral blood lymphocytes ( pbls ) from 100 ml blood samples from immunized animals and subsequent reverse transcription to cdna was done using commercial kits , such as paxgene blood rna tubes and blood rna kit system ( qiagen , mississauga , on ). amplification of cdna was done using pcr with primers seq id no : 1 and seq id no : 2 . the second round of pcr amplification was done using primers with built - in restriction enzyme sites ( seq id no : 3 and seq id no : 4 ) for insertion into phen4 phagemid , which was used to transform bacterial cells ( wk6 e . coli ). the clones were sequenced by the dideoxy sequencing method . sequences were then translated so that they can be assigned to well defined domains of the sdab . the bacterial cells containing the proper plasmids were grown , and expression of the recombinant proteins induced with 1 mm isopropyl - β - d - thiogalactopyranoside ( iptg ). the periplasmic proteins were extracted by osmotic shock in the presence of protease inhibitors [( 4 -( 2 - aminoethyl ) benzenesulfonyl fluoride ( aebsf ) and leupeptin )], and recombinant protein purified by immobilized metal affinity chromatography ( ni - nta superflow , qiagen ). the maldi - tof mass spectrometry of aβ - sdab 1a in sinapinic acid displayed a molecular ion at m / e 84873 . 5842 . the molecular weight was validated by sds - page and western blot . the purified aβ - sdab 1a was further characterized by elisa and immunohistochemical staining of tissues from transgenic mice and human patients . fig6 depicts the results of elisa performed in pierce &# 39 ; s maxisorp plate , which had been coated with 500 ng / well of aβ - 42 peptide at ph 9 . 5 overnight at room temperature . after washing the plate with water , the antigen coated wells were blocked with 1 % bsa and subsequently treated with identical concentrations of aβ - sdab 1a and mouse - aβ - mab for the same length of time and temperature ( 2 hours at rt ). detection was done using hrp labeled secondary antibody and tmb as a substrate . the blue color generated by hrp reaction was quenched with 1 . 0 m hcl and od450 recorded on molecular devices spectramax plus plate reader . fig6 is the plot of od450 readings of the chromogenic yellow color generated by the reaction of the substrate with the hrp - enzyme . the single - domain antibody 1a clearly outperformed the commercial aβ - mouse - mab . e . ex - vivo and in - vivo results of peptide compositions 1a and 2a in alzheimer &# 39 ; s disease models 1 . detection of amyloid plaque in transgenic mouse and human alzheimer &# 39 ; s patients with peptide composition 2a in ex - vivo experiments the specificity of aβ - sdab for aβ was tested by immunohistochemical ( ihc ) staining of paraffin embedded brain tissues from the app transgenic mouse ( fig7 a upper two frames ) and alzheimer &# 39 ; s patient ( fig7 a lower two frames ), with and without primary aβ - sdab . the same tissues were stained with thioflavin - s dye ( fig7 b ). paraffin tissues were cut in a microtome to the thickness of 5 microns , mounted on apes coated slides , dried at room temperature ( rt ) for 24 hours , and then deparaffinized using xylene and ethanol . washed slides were blocked in 10 % normal serum with 1 % bsa ( 2 hours at rt ), and treated with single - chain aβ - sdab 2a in pbs containing 1 % bsa ( 1 : 100 dilution , overnight at 4 ° c .). after washing slides with 0 . 1 % triton x - 100 , endogenous peroxidase activity was blocked with 0 . 3 % hydrogen peroxide , followed by treatment with biotinylated goat - anti - llama - igg . detection was done with streptavidin - hrp and diaminobenzidine as hrp substrate . 2 . demonstration of bbb permeability of aβ - vab peptide compositions 1a and 2a in alzheimer &# 39 ; s - like transgenic mice we tested the bbb permeability of aβ - sdab 1a and single - chain aβ - sdab 2a . the single - chain aβ - sdab 2a had been prepared by the tcep ( triethoxy - phosphine ) reduction of aβ - sdab 1a above in section b . 1 . to demonstrate bbb penetration , 60 ug of aβ - sdab 1a or single - chain aβ - sdab 2a was injected in the tail vein ( fig8 ) of the live transgenic mice ( j9 strain : pdgf - app - sw - ind ; app : amyloid precursor protein ; sw and ind stand for swedish and indiana mutations in app ), according to the protocol outlined below ( table 8 ). the commercial mouse - aβ - mab was also used for comparative purposes . non - transgenic mice were used as negative controls . mice were sacrificed 4 hours and 24 hours after the injection and their brains serially sectioned . the two hemispheres were separated ; the left hemisphere was rapidly snap frozen on dry ice ( 2 to 5 min ) and stored at − 80 ° c . ; the right hemisphere was immersed in a cold 4 % paraformaldhehyde fixative solution . the fixed half brain was serially sectioned sagitally with the vibratome at 40 um and stored at − 20 ° c . in cryoprotective medium . sections were immunostained with biotinylated anti - llama - igg1 and detected with streptavidin - hrp using an enzyme substrate , followed by imaging with the laser confocal microscope ( fig9 ). co - localization studies between llama igg and aβ - protein were also performed by staining the tissues with thioflavin - s dye . digital images were analyzed with the imagequant program to assess numbers of lesions . all six transgenic mice analyzed 24 hours after a single low dose injection of 60 ug amyloid sd - antibody displayed labeling of amyloid - plaque in their central nervous system . the data shown in fig9 represents data obtained only with single - chain aβ - sdab 2a . binding of peptide compositions 1a and 2a to amyloid plaque was only detected in the app transgenic mice , not in non - transgenic mice . more importantly , aβ - sd - antibodies 1a and 2a labeled both the soluble / diffusible plaque and insoluble plaque , while thioflavin - s dye labeled primarily the insoluble plaque . soluble plaque is the one responsible for cognitive decline from alzheimer &# 39 ; s disease , not the insoluble plaque , which is labeled by other neuroimaging agents such as pittsburgh compound b and 18 f - flutemetmol . the single - chain sdab 2a stained about 10 % of all the soluble and insoluble plaque in the mouse brain , while aβ - sdab 1a labeled about 3 . 6 % of the total plaque in the same amount of time . 5 . pharmacokinetics study of single - chain aβ - sdab 2a for alzheimer &# 39 ; s disease in mice a pharmacokinetics ( pk ) study of the single - chain aβ - sdab 2a was conducted in collaboration with biotox sciences , san diego . in this study , three groups of mice ( average weight : ˜ 25 g ) were injected in the tail vein with 60 ug of single - chain aβ - sdab 2a in 200 ul of pbs buffer . at a predetermined timepoint , blood was drawn from the animals the the serum was analyzed for the concentration of the single - chain aβ - sdab 2a by elisa . all three sets of animals showed identical clearance of the single - chain aβ - sdab 2a from the blood ( fig1 ). fig1 is a graph of the serum retention time of the single - chain aβ - sdab 2a in aβ - mice . the x - axis represents time in hours and the y - axis concentration of single - chain aβ - sdab 2a per ml of serum . the two broken lines indicate non - linearity in the x - axis . clearance of amyloid - plaque by binding to mouse - aβ - mab and subsequent phagocytosis has been reported in the literature [ wang , y - j , et al ., clearance of amyloid - beta in alzheimer &# 39 ; s disease : progress , problems and perspectives , drug discovery today , 11 , 931 ( 2006 )]. although at 24 h the serum concentration of 2a in fig1 dropped to about half compared to what it was at 0 . 5 hour , its levels stayed at ˜ 40 % for 7 days , suggesting that the single - chain aβ - sdab 2a has a serum life of at least 7 days and , therefore , a remarkable potential for developing diagnostic and long - acting therapeutic agents . the slow decrease in serum concentrations of the single - chain aβ - sdab 2a in the first 24 h could be attributed to its binding with the amyloid - peptide . f . synthesis of antibody - coated nano - particles with peptide compositions 1 and 2 from fig2 to overcome the shortcomings of the prior art , this invention describes the synthesis of biodegradable polyalkylcyanoacrylate nanoparticles coated with aminated dextran and peptide compositions 1 and 2 in fig2 . the synthetic steps are outlined in fig1 - 14 . to a stirring solution of aminated dextran 4 ( 1 . 0 gm ) in 100 ml of 10 mm hcl ( ph 2 . 5 ) was slowly added 1 ml of butylcyanoacrylate ( bca ) ( fig1 and fig1 ). the reaction mixture was allowed to stir at rt for 4 hours to obtain a white colloidal suspension , which was carefully neutralized with 0 . 1 m nahco 3 solution to ph 7 . 0 . this colloidal suspension was filtered through 100 um glass - fiber filter to remove large particles . the filtrate was split into 50 ml centrifuge tubes and spun at 10 , 000 rpm for 45 minutes . after discarding the supernantant , the particles were washed several times with deionized water , centrifuging the particles and discarding the supernatant until no more white residue was seen in the supernatant . the resulting pbca particles , 5 , were stored in 0 . 01 % nan 3 / pbs at 4 ° c . ( fig1 and fig1 ). pbca particles 5 were washed with 50 mm mops buffer , ph 7 . 0 , to remove nan 3 . the particles were then treated 50 mm traut &# 39 ; s regeant in mops buffer for one hour to synthesize thiolated pbca nanoparticles 6 ( fig1 and fig1 ). the particles were then repeatedly washed to remove the unreacted traut &# 39 ; s reagent . purified peptide composition 1a ( 1 mg , 12 . 5 nm ) was dissolved in 50 mm mops buffer , ph 7 . 0 . it was treated with nhs - peg - mal ( mw : 3000 da ) ( 250 nm ) at rt for 1 hour ( fig1 ). the reaction was concentrated on amicon - centricon concentrators ( mw cutoff : 30 kda ) to remove hydrolyzed and unconjugated excess nhs - peg - mal . the purified pegylated derivative 8 was characterized by maldi - ms and 12 % sds - page gel . a similar process can be used to convert peptide composition 2 in fig2 into the pegylated derivative 3 ( fig1 ). 4 . synthesis of covalently conjugated peptide composition nanoparticles 7 and 9 the conjugation of maleimido - aβ - sdab 8 with thiolated pbca nanoparticles 6 was carried out at ph 7 . 0 in 50 mm mops buffer in the presence of 5 mm edta for 4 hours at rt ( fig1 ). the resulting pbca nanoparticles 9 were purified by washing off ( 5 × 50 ml deionized water ) the unreacted maleimido antibody 3 . the particles were stored in deionized water at 4 ° c . until used . a similar process can be used to convert pegylated derivative 3 and thiolated pbca nanoparticles 6 into pbca nanoparticles 7 ( fig1 ). the present disclosure is not to be limited in terms of the particular embodiments described in this application . many modifications and variations can be made without departing from its spirit and scope , as will be apparent to those skilled in the art . functionally equivalent methods , processes and compositions within the scope of the disclosure , in addition to those enumerated herein , will be apparent to those skilled in the art from the foregoing descriptions . such modifications and variations are intended to fall within the scope of the appended claims . the present disclosure is to be limited only by the terms of the appended claims , along with the full scope of equivalents to which such claims are entitled . it is to be understood that this disclosure is not limited to particular methods , processes , reagents , compounds compositions or biological systems , which can of course vary . it is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only , and is not intended to be limiting . all publications , patent applications , issued patents , and other documents referred to in this specification are herein incorporated by reference as if each individual publication , patent application , issued patent , or other document was specifically and individually indicated to be incorporated by reference in its entirety . definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure . while certain embodiments have been illustrated and described , it should be understood that changes and modifications could be made therein in accordance with ordinary skill in the art without departing from the technology in its broader aspects as defined in the following claims .
blood - brain barrier permeable peptide compositions that contain variable antigen binding domains from camelid and / or shark heavy - chain only single - domain antibodies are described . the variable antigen binding domains of the peptide compositions bind to therapeutic and diagnostic biomarkers in the central nervous system , such as the amyloid - beta peptide biomarker for alzheimer &# 39 ; s disease . the peptide compositions contain constant domains from human igg , camelid igg , and / or shark ignar . the peptide compositions include heavy - chain only single - domain antibodies and compositions with one or more variable antigen binding domain bound to one or more constant domains .