You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
a 85:15 , 120 kd copolymer of d , l - lactide and glycolide ( plg ) ( alkermes , cambridge , ma ) was utilized in a gas - foaming process to form macroporous plg matrices22 .
plg microspheres encapsulating gm - csf were made using standard double emulsion35 . to incorporate tumor lysates , biopsies of b16-f10 tumors that had grown subcutaneously in the backs of c57bl/6j mice ( jackson laboratory , bar harbor maine ) ,
were digested in collagenase ( 250 u / ml ) ( worthington , lakewood , nj ) , and subjected to 4 cycles of rapid freeze in liquid nitrogen and thaw ( 37c ) and then centrifuged at 400 rpm for 10 min . the supernatant containing tumor lysates was collected and lyophilized with the plg microspheres and the resulting mixture was used to make plg scaffold - based cancer vaccines . to incorporate cpg - odns into plg scaffolds , cpg - odn 1826 , 5-tcc atg acg ttc ctg acg tt-3 , ( invivogen , san diego , ca )
was first condensed with poly(ethylenimine ) ( pei , mw 25,000 g mol1 , sigma aldrich ) molecules by dropping odn-1826 solutions into pei solution , while vortexing the mixture25 . the charge ratio between pei and cpg - odn ( nh3+:po4- )
pei - cpg - odn condensate solutions were then vortexed with 60 l of 50% ( wt / vol ) sucrose solution , lyophilized and mixed with dry sucrose to a final weight of 150 mg .
the sucrose containing condensates was then mixed with blank , gm - csf and/or tumor lysate loaded plg microspheres to make plg cancer vaccines . to determine the efficiency of gm - csf incorporation and the kinetics of gm - csf release from plg scaffolds , i - labeled hr - gm - csf ( perkin elmer )
was utilized as a tracer , and standard release studies were performed ( details provided in supplemental materials ) .
similarly , the amount of melanoma protein incorporated into scaffolds and released into pbs media was assessed by a protein assay ( biorad laboratories , hercules , ca ) .
the amount of cpg - odn incorporated into plg scaffolds and released into pbs was determine by absorbance readings ( 260/280 and 260/230 ratios calculated at 0.2 mm pathlength ) using a nanodrop instrument , nd1000 ( nanodrop technologies , wilmington , de ) . to determine gm - csf concentrations at the scaffold implant site
, adjacent tissue was excised and digested with tissue protein extraction reagent ( pierce ) .
the gm - csf concentration in the tissue was then analyzed with elisa ( r&d systems ) , according to the manufacturer s instructions .
blank scaffolds and scaffolds containing gm - csf with or without 10 g pei - odn control ( 5- tcc atg agc ttc ctg agc tt -3 ) or 10
g pei - cpg - odn condensate loaded scaffolds were implanted into subcutaneous pockets on the back of 7 - 9 week old male c57bl/6j mice . for histological examination scaffolds
were excised , paraffin - embedded , and stained with hematoxylin and eosin . to analyze dc recruitment isolated cells
were counted using a z2 coulter counter ( beckman coulter ) , and subsets of the total cell population were then stained with primary antibodies ( bd pharmingen , san diego , ca ) conjugated to fluorescent markers to allow for analysis by flow cytometry . to track dc emigration from the implant site fitc
plg scaffolds with melanoma tumor lysates and various dosages of gm - csf and/or various quantities pei - cpg - odn condensates were implanted subcutaneously into the lower left flank of c57bl/6j mice .
animals were challenged 14 days later with a subcutaneous injection of 10 b16-f10 melanoma cells ( atcc , manassas , nj ) in the back of the neck .
animals were monitored for the onset of tumor growth ( approximately 1 mm ) and sacrificed for humane reasons when tumors grew to 20 - 25 mm ( longest diameter ) . for histological examination
, tumors were biopsied at days 20 - 25 after injection and fixed in z - fix ( anatech , battle creek , mi ) and paraffin - embedded . to examine tumor tissue for t - cell infiltration
, immunoperoxidase staining was performed using the avidin - biotinperoxidase vectastain elite abc kit ( vector laboratories ) . to determine the il-12 and ifn- concentration at the matrix implant site
, adjacent tissue was excised and digested with tissue protein extraction reagent ( pierce ) .
the il-12 and ifn concentration in the tissue was then analyzed with elisa ( r&d systems ) , according to the manufacturer s instructions . to determine the generation of trp-2-specific , cytotoxic t lymphocytes ,
single cell suspensions were prepared from the spleens of both nave mice and mice immunized with plg infection mimics ( antigen+3000ng gm - csf+ 10g cpg ) for 30 days .
these cells were initially stained with apc - h-2kb / trp2 pentamers ( proimmune , , oxford science park , uk ) , and subsequently stained with pe - anti - cd8 mab ( mab ( bd pharmingen , san diego ) .
plg cancer vaccines were compared to a common cell - based vaccine using b16-f10 melanoma cells that were genetically modified to express gm - csf , and subsequently irradiated ( 3500rad ) , as described previously16 . the irradiated tumor cells ( 510 cells )
were then injected subcutaneously into c57bl/6j mice that were challenged 14 days later with 10 b16-f10 melanoma cells .
a 85:15 , 120 kd copolymer of d , l - lactide and glycolide ( plg ) ( alkermes , cambridge , ma ) was utilized in a gas - foaming process to form macroporous plg matrices22 .
plg microspheres encapsulating gm - csf were made using standard double emulsion35 . to incorporate tumor lysates , biopsies of b16-f10 tumors that had grown subcutaneously in the backs of c57bl/6j mice ( jackson laboratory , bar harbor maine ) ,
were digested in collagenase ( 250 u / ml ) ( worthington , lakewood , nj ) , and subjected to 4 cycles of rapid freeze in liquid nitrogen and thaw ( 37c ) and then centrifuged at 400 rpm for 10 min . the supernatant containing tumor lysates was collected and lyophilized with the plg microspheres and the resulting mixture was used to make plg scaffold - based cancer vaccines . to incorporate cpg - odns into plg scaffolds , cpg - odn 1826 , 5-tcc atg acg ttc ctg acg tt-3 , ( invivogen , san diego , ca )
was first condensed with poly(ethylenimine ) ( pei , mw 25,000 g mol1 , sigma aldrich ) molecules by dropping odn-1826 solutions into pei solution , while vortexing the mixture25 . the charge ratio between pei and cpg - odn ( nh3+:po4- )
pei - cpg - odn condensate solutions were then vortexed with 60 l of 50% ( wt / vol ) sucrose solution , lyophilized and mixed with dry sucrose to a final weight of 150 mg .
the sucrose containing condensates was then mixed with blank , gm - csf and/or tumor lysate loaded plg microspheres to make plg cancer vaccines . to determine the efficiency of gm - csf incorporation and the kinetics of gm - csf release from plg scaffolds , i - labeled hr - gm - csf ( perkin elmer )
was utilized as a tracer , and standard release studies were performed ( details provided in supplemental materials ) .
similarly , the amount of melanoma protein incorporated into scaffolds and released into pbs media was assessed by a protein assay ( biorad laboratories , hercules , ca ) .
the amount of cpg - odn incorporated into plg scaffolds and released into pbs was determine by absorbance readings ( 260/280 and 260/230 ratios calculated at 0.2 mm pathlength ) using a nanodrop instrument , nd1000 ( nanodrop technologies , wilmington , de ) . to determine gm - csf concentrations at the scaffold implant site
, adjacent tissue was excised and digested with tissue protein extraction reagent ( pierce ) .
the gm - csf concentration in the tissue was then analyzed with elisa ( r&d systems ) , according to the manufacturer s instructions .
blank scaffolds and scaffolds containing gm - csf with or without 10 g pei - odn control ( 5- tcc atg agc ttc ctg agc tt -3 ) or 10 g pei - cpg - odn condensate loaded scaffolds were implanted into subcutaneous pockets on the back of 7 - 9 week old male c57bl/6j mice . for histological examination scaffolds
were excised , paraffin - embedded , and stained with hematoxylin and eosin . to analyze dc recruitment isolated cells
were counted using a z2 coulter counter ( beckman coulter ) , and subsets of the total cell population were then stained with primary antibodies ( bd pharmingen , san diego , ca ) conjugated to fluorescent markers to allow for analysis by flow cytometry . to track dc emigration from the implant site fitc
plg scaffolds with melanoma tumor lysates and various dosages of gm - csf and/or various quantities pei - cpg - odn condensates were implanted subcutaneously into the lower left flank of c57bl/6j mice .
animals were challenged 14 days later with a subcutaneous injection of 10 b16-f10 melanoma cells ( atcc , manassas , nj ) in the back of the neck .
animals were monitored for the onset of tumor growth ( approximately 1 mm ) and sacrificed for humane reasons when tumors grew to 20 - 25 mm ( longest diameter ) . for histological examination
, tumors were biopsied at days 20 - 25 after injection and fixed in z - fix ( anatech , battle creek , mi ) and paraffin - embedded . to examine tumor tissue for t - cell infiltration
, immunoperoxidase staining was performed using the avidin - biotinperoxidase vectastain elite abc kit ( vector laboratories ) . to determine the il-12 and ifn- concentration at the matrix implant site ,
the il-12 and ifn concentration in the tissue was then analyzed with elisa ( r&d systems ) , according to the manufacturer s instructions . to determine the generation of trp-2-specific , cytotoxic t lymphocytes ,
single cell suspensions were prepared from the spleens of both nave mice and mice immunized with plg infection mimics ( antigen+3000ng gm - csf+ 10g cpg ) for 30 days .
these cells were initially stained with apc - h-2kb / trp2 pentamers ( proimmune , , oxford science park , uk ) , and subsequently stained with pe - anti - cd8 mab ( mab ( bd pharmingen , san diego ) .
plg cancer vaccines were compared to a common cell - based vaccine using b16-f10 melanoma cells that were genetically modified to express gm - csf , and subsequently irradiated ( 3500rad ) , as described previously16 . the irradiated tumor cells ( 510 cells )
were then injected subcutaneously into c57bl/6j mice that were challenged 14 days later with 10 b16-f10 melanoma cells .
cancer vaccines typically depend on cumbersome and expensive manipulation of cells in the laboratory , and subsequent cell transplantation leads to poor lymph node homing and limited efficacy . 
 we propose that materials mimicking key aspects of bacterial infection may instead be used to directly control immune cell trafficking and activation in the body . 
 it is demonstrated that polymers can be designed to first release a cytokine to recruit and house host dendritic cells ( dcs ) , and subsequently present cancer antigens and danger signals to activate the resident dcs and dramatically enhance their homing to lymph nodes . specific and protective anti - tumor immunity was generated with these materials , as 90% survival was achieved in animals that otherwise die from cancer within 25 days . 
 these materials show promise as cancer vaccines , and more broadly suggest that polymers may be designed to program and control the trafficking of a variety of cell types in the body .