transfection efficiency of polyhydroxypropyleneimine ( php ) was initially tested on hela cells using alexa fluor ( af ) 488 - labeled antibody ( goat igg ) as a control protein . different polyanions : dna , sodium polyphosphate ( pp ) and sodium polytungstate ( pw ) were tested as additives aiming to improve complex formation . commercial protein transfection reagents chariot ( ambion ) and project ( pierce ) were used as positive controls . the transfection efficiency was evaluated using three criteria : the percent of af488 positive cells , the percent of dead cells ( toxicity ) and the mean fluorescence intensity ( mfi ). the results show that antibody cannot internalize into the cell on its own ( fig1 ). the amount of af488 - positive cells increased to 65 % when cationic polymer php was used in complex with the antibody . the percent of transfected cells was even higher ( up to 85 - 95 %) when different polyanions ( dna , pp or pw ) were added into the mixture , suggesting that polyanions have positive effect for protein delivery . polyanions alone , on the other hand , have no effect on protein entry into the cell ( fig3 ). comparison of obtained antibody transfection results with two commonly used commercial protein transfection reagents — chariot and project , reveals very similar transfection efficiencies ( 85 % for chariot and 80 % for project ). however , when comparing the mfi values , the polytungstate evidently is more effective and mediates the biggest amount of protein ( mfi ˜ 370 ) being delivered into the cell , which is significantly higher than that shown for chariot or project ( mfi ˜ 100 and 150 , respectively ). to determine cellular localization of transduced proteins , the cells were transfected with β - galactosidase using the same compositions and protocols as described above . the cells were further fractionated using proteojet ™ membrane protein extraction kit ( fermentas ) in order to separate membrane and cytosolic proteins . enzymatic activity of β - galactosidase was estimated in both fractions ( fig2 ). results show that majority of β - gal activity was detected in the cytosolic fraction for all php and project - mediated transfections , while very little or no β - gal activity was detected in the membrane fraction of php - transfected cells , suggesting that cationic polymer ( with or without polyanions ) positions transduced proteins exclusively inside the cell . for project , however , considerable amount of β - gal activity was found in the membrane , indicating that equivalent amount of protein after transfection remains stuck within or on the surface of the cellular membrane . for chariot - mediated transfection , significantly more β - galactosidase was found in the membrane fraction than in the cytosol . in conclusion , php - polyanion mixture facilitates highly efficient protein transduction resulting primarily in cytosolic protein localization inside the cell . to examine if other polyanions contribute to cationic polymer - mediated protein transduction , we tested sodium phosphomolybdate hydrate ( pmop ), ammonium molybdate tetrahydrate ( pmo ), as well as sodium phosphotungstate tribasic hydrate ( pwp ) along with previously used polyanions : dna , pp and pw ( fig3 ). the results show that all analyzed polyanions enhance protein transfection to a similar level of 80 - 95 %. the mfi data , however , singled out polytungstates ( with or without hetero atoms ) as the most potent enhancers ( mfi ˜ 1200 ). the polyoxometalates ( poms ) carrying hetero atom ( pwp and pmop ) apparently performed slightly worse than poms without hetero atom ( pw and pmo ). to further investigate if polyanions have positive effect in combination with other polycations used in protein transfections , a popular cationic polymer — lpei was tested along with php in fluorescently labelled antibody transfections . polyanions — dna , pp and pw were used to assist protein packaging prior to complexation with lpei ( fig4 ). the results show that polyanions enhance lpei - mediated protein transfection as efficiently as php - mediated transfection . the mfi values increase from 10 units ( protein - lpei ) to 25 , 60 and 130 units upon addition of dna , pp or pw , respectively . the results suggest that negatively charged polyanions may interact with positively charged regions of the antibody and consequently facilitate protein - polyanion interaction with the positively charged polycation . to demonstrate that polyanions are able to enhance transfection of any type protein , a number of proteins of different size , pi value or function were chemically conjugated to fitc and examined using the same conditions as those used for antibody transfections described above . successful delivery of 5 kda peptide ( fig5 a ), 12 kda cytochrome c , 18 kda β - lactoglobulin ( fig5 b ), 66 kda bsa , 97 kda amyloglucosidase , as well as earlier tested 116 kda β - galactosidase ( fig2 ) and 150 kda igg ( fig1 , 4 ), confirm that polyanions enhance transfection of any size protein carried by cationic polymer php . the mfi values primarily depend on the size of the protein , i . e . the extent of fitc labelling . smaller proteins had lower number of fitc molecules and , as a result , their fluorescence was weaker . the transfection of proteins bearing different pi ( amyloglucosidase — pi 3 . 5 , β - lactoglobulin pi 5 . 5 , cytochrome c pi 10 . 5 ) gave similar results ( fig5 b ), all three proteins were delivered with ˜ 90 % efficiency . the amount of polyanion used in this case , depended on the pi of the protein : less polyanion was needed for transfection of amyloglucosidase ( 0 . 5 μl ), more for transfection of cytochrome c ( 1 . 0 μl ). overall , the results show , that polyanion - polycation combination enhances the transfection of proteins with ( i ) different size , ( ii ) different pi and ( iii ) different function . for the final evaluation of polyanion exerted effect on the php - mediated protein transfection the experiments were carried on different cell types : primary human lung fibroblasts ( primary cells — usually difficult to transfect ), hela s3 ( loosely adherent cell line ), and jurkat t cell lymphoma cells ( suspension cell line — known to be very difficult to transfect by chemical methods ). the results showed that irrespective of the cell type used , the transfection efficiencies reached 90 % ( fig6 ). the fluorescence level in strongly adherent hlf cells was the highest ( mfi ˜ 1500 ), while in semiadherent or suspension cells , hela s3 and jurkat , the mfi was 350 and 500 , respectively , suggesting that the extent of macromolecule uptake depends on the cell type . cell size in this experiment should be taken into consideration as well , since hlf cells are significantly bigger , can internalize more material than hela s3 or jurkat cells , and thus fluoresce more intensively than smaller cells . in conclusion , the polyanion ( here , pwp ) grouping with protein prior to complexation with polycation ( php ) facilitates efficient protein delivery into the primary , adherent and suspension cell types . evaluation of polyanion - protein - polycation complex formation after different component mixing schedule and its influence on transfection efficiency was carried out in order to determine the best possible way to form protein - php complexes and to ensure the most efficient cargo transport through the cellular membrane . the results apparently were very similar , no matter how the components were mixed together ( fig7 ), the transfection efficiencies ranged from 80 to 95 %. slightly lower mfi values ( 200 units ) suggested that protein should not be the last element added into the mix , but rather mixed with either polycation or polyanion first . transfection of hela ( human cervical carcinoma - derived cell line ) cells was carried out as follows : one day before the transfection experiment , the cells were seeded in a 24 - well tissue culture plate at the density of 5 × 10 4 cells per well in the total volume of 1 ml dmem culture medium supplemented with 10 % fbs . the cells were incubated at 37 ° c . in a co 2 incubator until they reached 70 - 80 % confluency ( usually within 24 h ). on the day of transfection , the growth medium was removed and replaced with 0 . 5 ml of warm serum - free medium . alexa fluor 488 - labeled goat igg antibody ( 1 μg ) was diluted in 100 μl of 0 . 15m nacl solution and mixed with different amounts of polyanions : dna ( 1 μg puc18 ), sodium polyphosphate ( 10 mm pp — 1 μl ) or sodium polytungstate ( 10 mm pw — 3 μl ). cationic polymer php ( 1 μl ) was added into the protein - polyanion mixture and vortexed immediately for few seconds to ensure even distribution of the material . the complexes were allowed to form for 15 - 20 min at room temperature and added to the cell culture in a drop - wise manner . the cells were further incubated for 2 h at 37 ° c . in a co 2 incubator . to remove unincorporated complexes , the cultures were rinsed with pbs , and the cells were analyzed by facs ( fluorescence activated cell sorter ). transfections using chariot ( ambion ) and project ( pierce ) reagents were carried out following manufacturer suggested protocols . hela cell transfection with β - galactosidase ( 1 μg ) was carried out using the same protocol and conditions as described above . the cells were further fractionated using proteojet ™ membrane protein extraction kit ( fermentas ) in order to separate membrane and cytoplasmic proteins . the enzymatic activity of β - galactosidase in both fractions was estimated using colorimetric assay . several different polyanions were tested for their ability to improve labelled - igg transfection . polyanions were grouped as follows : ( i ) phosphates — heterophosphates ( dna ) and homophosphates ( sodium polyphosphate — pp ), ( ii ) poms — without hetero atom ( sodium polytungstate , pw , or ammonium molybdate tetrahydrate , pmo ) and with hetero atom ( sodium phosphotungstate tribasic hydrate , pwp , and sodium phosphomolybdate hydrate , pmop ). hela cells were prepared for transfection essentially as described in example 1 . the amount of each polyanion used was : 3 μl of pw , pwp or pmop , and 2 μl of pmo ( each 10 mm stock concentration ), 0 . 5 μl of pp ( 30 mm stock concentration ), 1 μg of dna . polyanion - antibody - php mixtures were incubated for 15 min and added to the cells in a drop - wise manner . transfection results were processed 2 h later using guava easy cyte plus flow cytometry system ( millipore ). cationic polymer lpei ( exgen 500 ) was tested in alexa fluor 488 - labeled goat igg transfection using polyanions — dna , pp and pw to assist the protein packaging prior to complexation with lpei . chinese hamster ovary cells ( chok1 ) were prepared for transfection essentially the same way as hela cells ( example 1 ). the cells were cultured in rpmi medium supplemented with 10 % fbs , the transfection was carried out in serum free rpmi medium . the complexes were formed the same way as described in example 1 for php , the amount of lpei used — 3 . 3 μl . fitc - labeled proteins — 5 kda peptide , bsa , amyloglucosidase ( pi 3 . 5 ), β - lactoglobulin ( pi 5 . 5 ) and cytochrome - c ( pi 10 . 5 ) were transfected into hela cells following the procedure described in example 1 . the amount of pwp used : 0 . 5 μl for amyloglucosidase and β - lactoglobulin , 1 μl for cytochrome c . analysis of the polyanion effect on difficult to transfect cell lines comparison of protein transfer efficiency using php and polyanions ( pwp ) was tested in suspension cell lines , hela s3 and jurkat ( human t cell lymphoma cell line ), as well as in primary cells hlf ( human lung fibroblasts ). suspension cells were seeded at the density of 2 × 10 5 cells / well , hlf 5 × 10 4 / well 24 hours before the transfection . antibody - php complexes in 0 . 15 m nacl solution were prepared as described earlier . hela cells were prepared for transfection as described in example 1 . the antibody igg ( 1 μg )- pwp ( 1 μl )- php ( 1 μl ) complexes were prepared in 0 . 15 m nacl following different component mixing order : igg + pa + php , pa + igg + php , igg + php + pa , php + igg + pa pa + php + igg , and php + pa + igg . complexes were allowed to form for 15 min and added to the cells in a drop - wise manner .