_:b418059142 . . _:b6368100 . . _:b6368101 . _:b6368133 "Such arrangements leave the drug exposed to the solution environment and do not necessarily impart amphiphilic self-assembly of a nanostructures2, >>3<<, 38. In common with other peptide-drug conjugates2, our approach permits control over release (rate, mechanism, in vivo location) via the design of linker chemistry. For example, the linker described here contains an internal, acid-labile" . _:b6368126 "the synthesis of complex terpolymers in which the co-polymerization or attachment of fatty acids or cholesterol to the polymer chain drives its self-assembly33, 34; or (3) the design of sophisticated and complex dendrimer architectures>>3<<. While all of these approaches have their merits, they are far more complicated than the genetically encoded delivery system described herein, as they rely upon complex, multi-step synthesis of polymers, which can be difficult to scale-up." . _:b6368140 . _:b6368102 . _:b6368103 . _:b6368139 . . _:b6368096 . _:b6368125 . _:b6368097 . _:b6368094 _:b6368095 . _:b418059153 . _:b6368098 . _:b6368132 . _:b6368092 _:b6368093 . . _:b6368099 . _:b6368135 . _:b6368097 "Although a number of different nanoscale delivery systems have been proposed for cancer therapy>>5<<, most do not satisfy these criteria, which are critical to move these systems into clinical practice." . . _:b6368108 . _:b418059187 . _:b6368109 . _:b6368122 . _:b418059112 . . _:b6368110 . _:b6368110 . _:b6368111 . _:b6368108 . _:b6368093 . _:b6368104 . _:b6368094 _:b6368124 . _:b6368094 _:b6368125 . _:b6368094 _:b6368126 . _:b6368105 . _:b6368094 _:b6368127 . _:b6368094 _:b6368120 . _:b6368094 _:b6368121 . _:b6368094 _:b6368122 . _:b6368106 . _:b6368094 _:b6368123 . _:b6368094 _:b6368116 . _:b6368094 _:b6368117 . _:b6368094 _:b6368118 . _:b6368107 . _:b418059195 . _:b6368094 _:b6368119 . _:b6368094 _:b6368112 . _:b6368112 . _:b6368111 . _:b6368094 _:b6368113 . _:b6368129 "For example, methods that rely on physical encapsulation and size fractionation of nanoparticles, such as polymer micelles3, liposomes1, and emulsion polymerization>>35<<, are highly multicomponent systems (i.e. drugs, buffers, mixtures of amphiphiles, monomers, solvents, and excipients), which can hinder pharmaceutical viability." . _:b6368094 _:b6368114 . _:b6368094 _:b6368115 . _:b6368116 . _:b6368094 _:b6368108 . _:b6368094 _:b6368109 . _:b418059146 . _:b6368094 _:b6368110 . _:b6368094 _:b6368111 . _:b6368117 . _:b6368094 _:b6368104 . _:b6368094 _:b6368105 . _:b6368094 _:b6368106 . _:b6368094 _:b6368107 . _:b6368118 . _:b6368096 . _:b6368094 _:b6368100 . _:b6368094 _:b6368101 . _:b418059178 . _:b6368094 _:b6368102 . _:b6368094 _:b6368103 . _:b6368119 . _:b6368094 _:b6368096 . _:b6368094 _:b6368097 . _:b6368094 _:b6368098 . _:b6368094 _:b6368099 . _:b6368112 . . _:b6368113 . . _:b6368117 "While numerous genes are involved in DNA repair>>23<<, this analysis identified one particular gene, uracil-DNA glycosylase (Ung), that is down-regulated only by CP-Dox treatment (Fig." . _:b418059118 . _:b6368114 . . _:b418059089 . _:b6368115 . _:b6368129 . . _:b6368124 . _:b418059162 . _:b6368125 . _:b418059093 "4"^^ . _:b6368126 . _:b418059092 "4"^^ . _:b6368101 "led us to hypothesize that the attachment of multiple copies of a hydrophobic agent, such as Dox or other hydrophobic moieties, would impart sufficient amphiphilicity to the polypeptide to drive its self-assembly into nanoparticles9, >>10<<. Second, ELPs are useful biopolymers, being non-toxic11, 12, biodegradable, and displaying good pharmacokinetics13." . _:b6368126 . _:b6368127 . _:b418059095 "4"^^ . _:b6368127 . _:b6368120 . _:b418059094 "4"^^ . _:b418059090 "7"^^ . _:b6368121 . _:b6368122 . _:b418059096 . _:b6368123 . . _:b418059091 "5"^^ . . . _:b6368132 . _:b418059089 "8"^^ . . _:b6368133 . _:b418059101 "3"^^ . _:b6368098 "First, ELPs undergo an inverse phase transition in aqueous solutions at a characteristic transition temperature (Tt), above which they desolvate and phase separate from bulk water>>7<<. For recombinant ELP block copolymers, this phase transition behavior promotes self-assembly into nanostructures, driven by selective desolvation of one block8-10. These observations led us to hypothesize that the attachment of multiple" . _:b418059120 . _:b6368134 . _:b418059100 "3"^^ . _:b418059202 . _:b418059103 "3"^^ . _:b6368135 . _:b418059125 . _:b418059102 "3"^^ . _:b6368128 . _:b418059097 "3"^^ . _:b6368129 . _:b418059096 "3"^^ . _:b6368130 . _:b418059099 "3"^^ . _:b6368131 . _:b6368121 "are monoblock PEG-Dox conjugates that appear to form micelles, but their self-assembly was only explored with a single hydrophobic drug (Dox), so it remains unclear whether this approach will apply to other hydrophobic drugs and polymers>>29<<. Furthermore, in comparison with CP-Dox, the PEG-Dox conjugate displayed limited efficacy in extending survival time and did not produce long-term cures in an animal model." . _:b418059098 "3"^^ . _:b6368140 . . _:b418059109 "3"^^ . . _:b418059136 . . _:b418059108 "3"^^ . . _:b418059094 . _:b6368100 "led us to hypothesize that the attachment of multiple copies of a hydrophobic agent, such as Dox or other hydrophobic moieties, would impart sufficient amphiphilicity to the polypeptide to drive its self-assembly into nanoparticles>>9<<, 10. Second, ELPs are useful biopolymers, being non-toxic11, 12, biodegradable, and displaying good pharmacokinetics13." . _:b418059111 "3"^^ . _:b418059192 . _:b418059110 "3"^^ . _:b6368136 . _:b418059175 . _:b418059105 "3"^^ . _:b6368137 . _:b6368121 . . _:b6368132 "Such arrangements leave the drug exposed to the solution environment and do not necessarily impart amphiphilic self-assembly of a nanostructures>>2<<, 3, 38. In common with other peptide-drug conjugates2, our approach permits control over release (rate, mechanism, in vivo location) via the design of linker chemistry. For example, the linker described here contains an internal," . . _:b6368118 . _:b418059104 "3"^^ . _:b6368138 . . _:b418059107 "3"^^ . _:b6368139 . _:b6368137 . _:b418059106 "3"^^ . . _:b418059117 "2"^^ . . _:b418059116 "2"^^ . . _:b418059119 "2"^^ . . _:b6368092 "methods" . _:b418059130 . _:b418059124 . _:b418059118 "2"^^ . . . _:b418059113 "2"^^ . . _:b418059112 "3"^^ . _:b6368135 "In common with other peptide-drug conjugates>>2<<, our approach permits control over release (rate, mechanism, in vivo location) via the design of linker chemistry." . _:b418059115 "2"^^ . _:b418059128 . _:b418059116 . _:b418059114 "2"^^ . . _:b418059125 "2"^^ . _:b6368104 . _:b418059124 "2"^^ . _:b418059127 "2"^^ . _:b418059131 . . _:b6368115 "The decreased accumulation in the heart is notable, as cardiomyopathy is the dose-limiting side effect of free Dox>>21<<. The increase in tumor exposure and decrease in heart exposure is one mechanism which explains why the MTD of CP-Dox nanoparticles is higher than that of free Dox (Supplementary Fig. 4, Table 4), and suggested that CP-Dox encapsulation" . . _:b6368095 . _:b418059126 "2"^^ . . _:b418059121 "2"^^ . . . _:b6368099 . _:b418059120 "2"^^ . . "PMC0" . . _:b418059193 . _:b418059123 "2"^^ . _:b418059122 "2"^^ . _:b418059133 "2"^^ . _:b418059132 "2"^^ . . _:b6368102 . _:b418059135 "2"^^ . . _:b6368099 . _:b418059115 . _:b6368101 . _:b418059134 "2"^^ . _:b418059129 "2"^^ . . _:b418059128 "2"^^ . . _:b418059131 "2"^^ . _:b418059130 "2"^^ . . _:b418059141 "2"^^ . _:b418059140 "2"^^ . _:b418059100 . _:b418059114 . _:b418059143 "2"^^ . _:b418059142 "2"^^ . _:b6368114 . _:b6368127 "For example, methods that rely on physical encapsulation and size fractionation of nanoparticles, such as polymer micelles>>3<<, liposomes1, and emulsion polymerization35, are highly multicomponent systems (i.e. drugs, buffers, mixtures of amphiphiles, monomers, solvents, and excipients), which can hinder pharmaceutical viability." . _:b418059137 "2"^^ . _:b6368130 "Also, attachment of drug solely at the chain end ensures that the drug is sequestered in the nanoparticles\u2019 core\u2013 unlike other nanoparticle drug carriers, such as dendrimers>>3<<, metal nanoparticles36, or carbon nanotubes37." . _:b418059201 . _:b418059136 "2"^^ . _:b418059196 . . _:b418059139 "2"^^ . . _:b6368116 "Dox intercalates with DNA and freezes topoisomerase-II to the ends of freshly cut DNA, which leads to permanent DNA damage and exit from the cell cycle>>22<<. While numerous genes are involved in DNA repair23, this analysis identified one particular gene, uracil-DNA glycosylase (Ung), that is down-regulated only by CP-Dox treatment (Fig. 6b); furthermore, Ung is associated with resistance to" . _:b418059138 "2"^^ . _:b6368099 "For recombinant ELP block copolymers, this phase transition behavior promotes self-assembly into nanostructures, driven by selective desolvation of one block>>8<<-10. These observations led us to hypothesize that the attachment of multiple copies of a hydrophobic agent, such as Dox or other hydrophobic moieties, would impart sufficient amphiphilicity to the polypeptide to drive its self-assembly" . _:b418059149 "2"^^ . _:b418059148 "2"^^ . _:b418059098 . _:b418059151 "2"^^ . _:b418059150 "2"^^ . _:b418059107 . . _:b418059145 "2"^^ . . _:b6368125 "PEG-based biohybrid block copolymers to encapsulate the drug18, 30-32; (2) the synthesis of complex terpolymers in which the co-polymerization or attachment of fatty acids or cholesterol to the polymer chain drives its self-assembly33, >>34<<; or (3) the design of sophisticated and complex dendrimer architectures3." . _:b6368140 "Similarly, peptide linkers that are substrates for tumor specific proteases (cathepsins and matrix metalloproteases) may enable preferential release in the tumor2, >>39<<. Both approaches can be easily incorporated into a CP via recombinant DNA methodology." . _:b6368095 "Packaging clinically approved drugs into nanoscale delivery vehicles (10-100 nm diameter)>>1<<-3 is of particular interest for cancer therapy, as numerous studies have shown that objects within this size range accumulate within solid tumors due to the enhanced permeability and retention (EPR) effect, which results from" . . _:b418059144 "2"^^ . _:b6368095 . _:b418059147 "2"^^ . _:b418059146 "2"^^ . _:b418059157 "2"^^ . _:b418059151 . . _:b418059156 "2"^^ . _:b418059189 . _:b418059159 "2"^^ . . _:b418059158 "2"^^ . _:b6368094 "text" . _:b418059095 . _:b418059153 "2"^^ . _:b418059152 "2"^^ . _:b6368139 "Similarly, peptide linkers that are substrates for tumor specific proteases (cathepsins and matrix metalloproteases) may enable preferential release in the tumor>>2<<, 39. Both approaches can be easily incorporated into a CP via recombinant DNA methodology." . _:b418059155 "2"^^ . _:b418059154 "2"^^ . _:b6368103 . _:b418059165 "2"^^ . . . _:b418059164 "2"^^ . _:b6368124 "PEG-based biohybrid block copolymers to encapsulate the drug18, 30-32; (2) the synthesis of complex terpolymers in which the co-polymerization or attachment of fatty acids or cholesterol to the polymer chain drives its self-assembly>>33<<, 34; or (3) the design of sophisticated and complex dendrimer architectures3." . _:b418059106 . _:b418059167 "2"^^ . _:b418059190 . _:b418059165 . _:b418059166 "2"^^ . _:b418059121 . _:b418059181 . _:b418059161 "2"^^ . _:b418059160 "2"^^ . _:b418059163 "2"^^ . _:b418059192 . _:b418059193 . _:b418059162 "2"^^ . _:b418059194 . _:b418059195 . _:b418059196 . _:b418059197 . _:b418059198 . _:b418059173 "2"^^ . _:b418059199 . _:b418059184 . _:b418059185 . _:b418059186 . _:b418059172 "2"^^ . _:b418059187 . _:b6368105 . _:b418059188 . _:b418059189 . _:b418059190 . _:b418059175 "2"^^ . _:b418059191 . _:b6368106 . _:b418059176 . _:b418059177 . _:b418059178 . _:b6368104 "Fourth, ELPs can be produced with high yield (~100-200 mg/L) in E. coli, and can be easily and rapidly purified by exploiting their phase transition behavior>>14<<, so that high-purity, clinical grade material is easily and cheaply obtained." . _:b418059174 "2"^^ . _:b418059179 . _:b418059180 . _:b418059181 . _:b418059182 . . _:b418059169 "2"^^ . _:b418059183 . _:b418059168 . _:b418059169 . _:b418059170 . . _:b418059168 "2"^^ . _:b418059092 . _:b418059171 . _:b6368116 . _:b418059172 . . _:b418059173 . _:b418059174 . . _:b418059171 "2"^^ . _:b418059175 . _:b418059160 . _:b418059161 . _:b418059162 . _:b418059170 "2"^^ . _:b418059163 . _:b418059164 . _:b418059165 . . _:b418059166 . . _:b418059181 "2"^^ . _:b418059167 . _:b418059152 . . _:b418059153 . _:b6368120 . _:b418059154 . _:b418059180 "2"^^ . _:b418059155 . _:b418059156 . _:b418059157 . _:b418059148 . _:b418059158 . _:b418059183 "2"^^ . _:b418059159 . _:b418059144 . _:b418059145 . _:b418059146 . _:b418059182 "2"^^ . _:b418059147 . _:b418059148 . _:b418059149 . _:b418059093 . _:b418059150 . _:b418059177 "2"^^ . _:b418059151 . _:b418059136 . _:b418059097 . _:b418059137 . _:b418059092 . . _:b418059176 "2"^^ . _:b418059138 . _:b418059139 . _:b418059140 . _:b418059141 . _:b418059095 . _:b418059142 . _:b418059179 "2"^^ . . _:b418059143 . _:b418059143 . _:b418059094 . _:b418059178 "2"^^ . . _:b418059089 . _:b6368095 . . _:b418059189 "2"^^ . . _:b418059191 . . . _:b418059188 "2"^^ . _:b418059091 . _:b418059191 "2"^^ . _:b418059126 . _:b418059090 . _:b418059190 "2"^^ . _:b418059101 . _:b418059185 "2"^^ . _:b418059100 . . _:b418059184 "2"^^ . _:b418059103 . _:b418059187 "2"^^ . _:b418059102 . _:b6368097 . _:b418059117 . . _:b418059186 "2"^^ . . . _:b418059090 . _:b418059097 . _:b418059197 "2"^^ . _:b418059096 . _:b418059196 "2"^^ . _:b418059166 . _:b418059099 . . _:b418059199 "2"^^ . _:b418059159 . _:b418059098 . . _:b418059198 "2"^^ . _:b418059109 . _:b418059135 . _:b418059193 "2"^^ . _:b418059200 . _:b418059201 . _:b418059154 . _:b418059108 . _:b418059202 . _:b418059192 "2"^^ . _:b418059111 . _:b418059195 "2"^^ . _:b418059186 . _:b418059110 . _:b418059194 "2"^^ . _:b418059105 . _:b418059104 . . . _:b418059107 . _:b418059200 . _:b418059106 . _:b418059117 . _:b6368113 . _:b418059127 . _:b418059201 "2"^^ . _:b418059116 . _:b418059200 "2"^^ . . _:b418059119 . . . . _:b418059140 . . _:b418059118 . _:b418059202 "2"^^ . . . _:b418059113 . _:b418059112 . _:b418059199 . _:b418059115 . _:b6368120 . _:b418059114 . . . _:b418059125 . . "10.1038%2Fnmat2569" . _:b418059124 . _:b418059127 . _:b6368124 . _:b418059128 . _:b418059129 . _:b418059126 . _:b418059130 . _:b418059131 . _:b418059132 . _:b418059133 . _:b6368115 . _:b418059121 . _:b418059134 . _:b6368138 . _:b418059135 . _:b418059120 . _:b418059121 . _:b418059133 . _:b418059120 . _:b418059122 . _:b418059123 . _:b418059124 . _:b418059125 . _:b418059123 . _:b418059126 . . _:b418059127 . _:b418059112 . _:b418059113 . _:b418059122 . _:b418059114 . _:b418059115 . _:b418059116 . _:b418059117 . _:b418059133 . . _:b418059118 . _:b418059119 . _:b418059104 . _:b418059105 . _:b418059132 . _:b418059106 . _:b418059107 . . _:b418059108 . _:b418059109 . . _:b418059135 . _:b418059110 . _:b418059111 . _:b418059096 . _:b418059097 . _:b418059134 . _:b418059098 . _:b418059099 . _:b418059100 . _:b418059101 . _:b418059129 . . _:b418059102 . _:b418059185 . _:b418059103 . _:b418059089 . _:b418059128 . _:b418059090 . _:b418059091 . _:b418059092 . _:b418059093 . _:b418059131 . _:b418059091 . _:b6368138 "For example, the linker described here contains an internal, acid-labile hydrazone bond3, 16, >>17<< that triggers intracellular drug release in endosomes and lysosomes." . _:b418059094 . _:b418059163 . _:b418059095 . _:b418059102 . _:b418059130 . _:b418059141 . _:b418059140 . _:b6368137 "For example, the linker described here contains an internal, acid-labile hydrazone bond3, >>16<<, 17 that triggers intracellular drug release in endosomes and lysosomes." . . _:b418059143 . . _:b418059142 . _:b418059137 . _:b6368106 "1) so that it exhibits high solubility at body temperature, has long plasma circulation as seen by its area under the concentration-time curve (AUC)13, and degrades in serum at the rate of 2.5 weight % day-1 >>13<<. A second, shorter (Gly-Gly-Cys)8 segment was appended at the C-terminal end of the CP to provide drug attachment sites and impart sufficient amphiphilicity to the polymer. This segment provides eight drug attachment points \u2013unique Cys" . _:b418059136 . . _:b418059139 . _:b6368109 . _:b418059160 . _:b6368131 "Also, attachment of drug solely at the chain end ensures that the drug is sequestered in the nanoparticles\u2019 core\u2013 unlike other nanoparticle drug carriers, such as dendrimers3, metal nanoparticles36, or carbon nanotubes>>37<<. The ability to deterministically place the drug molecules at the end of the polymer chain also differentiates this system from many protein and polymer conjugates where the reactive sites are distributed along the polymer chain or" . _:b418059108 . _:b418059138 . . _:b418059171 . _:b418059149 . . _:b6368136 "For example, the linker described here contains an internal, acid-labile hydrazone bond>>3<<, 16, 17 that triggers intracellular drug release in endosomes and lysosomes." . _:b418059148 . _:b418059151 . _:b418059158 . _:b418059150 . _:b6368098 . . _:b418059145 . _:b418059144 . _:b418059111 . _:b418059147 . _:b6368134 "Such arrangements leave the drug exposed to the solution environment and do not necessarily impart amphiphilic self-assembly of a nanostructures2, 3, >>38<<. In common with other peptide-drug conjugates2, our approach permits control over release (rate, mechanism, in vivo location) via the design of linker chemistry. For example, the linker described here contains an internal, acid-labile" . _:b418059156 . _:b418059146 . _:b418059157 . _:b418059156 . _:b418059159 . _:b418059172 . _:b6368117 . _:b418059182 . _:b418059158 . _:b418059113 . _:b418059153 . . _:b418059152 . _:b418059155 . _:b418059137 . _:b418059154 . _:b418059165 . . _:b418059164 . _:b418059167 . . _:b418059166 . _:b418059099 . _:b418059109 . _:b418059161 . _:b418059105 . . _:b418059170 . _:b6368119 . _:b418059160 . _:b418059132 . _:b418059180 . _:b418059163 . . . _:b418059162 . _:b418059188 . _:b418059173 . . _:b418059172 . _:b418059175 . _:b418059174 . _:b6368131 . _:b418059169 . . _:b418059122 . . . _:b6368114 "The AUC for a mouse treated with the same dose of free Dox is only 4.7 \u03BCM hr>>20<<. Based on this significant increase in plasma AUC, these results suggested that CP-Dox nanoparticles are likely to preferentially accumulate in solid tumors as compared to free drug." . _:b418059168 . _:b6368093 "CPs were synthesized by heterologous expression of a plasmid-borne synthetic gene in E. coli as described previously>>14<<. Dox (MW= 580 g mol-1) was covalently linked to cysteine residues on CPs (Supplementary information)." . . _:b418059171 . _:b418059170 . _:b418059181 . _:b418059180 . _:b418059141 . _:b418059183 . _:b418059167 . _:b418059182 . . _:b418059177 . _:b418059176 . _:b418059110 . _:b418059179 . . _:b418059178 . . . _:b418059189 . _:b418059188 . _:b418059191 . . . _:b418059190 . _:b418059185 . . _:b418059184 . _:b418059187 . _:b418059119 . _:b6368111 "~40 nm diameter of these nanoparticles is below the pore size of the permeable vasculature found in many solid tumors, suggesting that CP-Dox nanoparticles should be able to selectively accumulate in a solid tumor via the EPR effect1, 3, >>4<<. In contrast, at pH 5.0, the polydispersity of CP-Dox nanoparticles increased with time, which is suggestive of the release of Dox from the CP-Dox conjugate via acid-catalyzed cleavage of the hydrazone linkages, and subsequent" . _:b418059186 . _:b418059174 . _:b418059198 . _:b418059197 . _:b418059196 . _:b418059199 . _:b418059198 . . _:b418059193 . . _:b418059192 . _:b6368107 "To activate Dox for conjugation, it was reacted with n-\u00DF-maleimidopropionic acid hydrazide tri-fluoroacetic acid to incorporate an internal, acid labile hydrazone moiety with a terminal maleimide>>16<<, 17, and this activated drug was covalently attached to the Cys residues of the CP (Fig." . _:b418059195 . _:b418059150 . _:b418059194 . _:b418059103 . _:b418059177 . . _:b418059138 . _:b418059201 . . . _:b418059173 . _:b6368120 "These data provide mechanistic insights into CP nanoparticle delivery and support the contention that CP nanoparticles may overcome drug resistance, as has been suggested for other drug delivery systems>>26<<-28." . _:b418059200 . . . _:b418059134 . _:b418059145 . _:b418059202 . . . . . . . _:b418059176 . _:b418059144 . _:b6368110 "~40 nm diameter of these nanoparticles is below the pore size of the permeable vasculature found in many solid tumors, suggesting that CP-Dox nanoparticles should be able to selectively accumulate in a solid tumor via the EPR effect1, >>3<<, 4. In contrast, at pH 5.0, the polydispersity of CP-Dox nanoparticles increased with time, which is suggestive of the release of Dox from the CP-Dox conjugate via acid-catalyzed cleavage of the hydrazone linkages, and subsequent" . _:b6368113 "Because CP-Dox conjugates have previously been demonstrated to localize within low pH compartments in cellular uptake assays>>19<<, the pH dependent release of Dox from the CP-Dox conjugate suggests endo-lysosomal release of the drug following cellular uptake of the CP-Dox nanoparticles." . . . . . . . . _:b6368123 . _:b6368128 . _:b6368108 "To activate Dox for conjugation, it was reacted with n-\u00DF-maleimidopropionic acid hydrazide tri-fluoroacetic acid to incorporate an internal, acid labile hydrazone moiety with a terminal maleimide16, >>17<<, and this activated drug was covalently attached to the Cys residues of the CP (Fig." . . _:b418059149 . . _:b6368134 . _:b6368128 "For example, methods that rely on physical encapsulation and size fractionation of nanoparticles, such as polymer micelles3, liposomes>>1<<, and emulsion polymerization35, are highly multicomponent systems (i.e. drugs, buffers, mixtures of amphiphiles, monomers, solvents, and excipients), which can hinder pharmaceutical viability." . _:b418059104 . _:b418059169 . . _:b6368094 _:b6368140 . _:b418059157 . _:b6368094 _:b6368136 . _:b6368094 _:b6368137 . _:b6368094 _:b6368138 . _:b418059123 . _:b6368094 _:b6368139 . _:b6368094 _:b6368132 . _:b6368094 _:b6368133 . _:b6368094 _:b6368134 . _:b6368094 _:b6368135 . _:b6368123 "Other methods to create drug loaded polymer nanoparticles have relied upon: (1) the chemical synthesis of amphiphilic PEG-based biohybrid block copolymers to encapsulate the drug18, >>30<<-32; (2) the synthesis of complex terpolymers in which the co-polymerization or attachment of fatty acids or cholesterol to the polymer chain drives its self-assembly33, 34; or (3) the design of sophisticated and complex dendrimer" . _:b6368094 _:b6368128 . _:b6368094 _:b6368129 . _:b6368094 _:b6368130 . _:b6368094 _:b6368131 . _:b6368109 "the ~40 nm diameter of these nanoparticles is below the pore size of the permeable vasculature found in many solid tumors, suggesting that CP-Dox nanoparticles should be able to selectively accumulate in a solid tumor via the EPR effect>>1<<, 3, 4. In contrast, at pH 5.0, the polydispersity of CP-Dox nanoparticles increased with time, which is suggestive of the release of Dox from the CP-Dox conjugate via acid-catalyzed cleavage of the hydrazone linkages, and subsequent" . _:b6368102 "Second, ELPs are useful biopolymers, being non-toxic>>11<<, 12, biodegradable, and displaying good pharmacokinetics13." . . _:b6368130 . . . _:b418059179 . _:b6368100 . . . _:b6368133 . _:b6368119 "6b); furthermore, Ung is associated with resistance to chemotherapeutics, including Dox24, >>25<<. By down-regulating DNA repair, CP-Dox may directly enhance the antitumor drug effect. These data provide mechanistic insights into CP nanoparticle delivery and support the contention that CP nanoparticles may overcome drug resistance, as" . _:b418059194 . _:b6368099 . . _:b6368136 . _:b418059101 . _:b418059184 . . . . . . _:b418059155 . . . _:b418059161 . _:b6368107 . _:b418059168 . _:b418059147 . _:b6368092 . _:b6368094 . . _:b418059183 . _:b418059139 . _:b418059093 . _:b6368118 "6b); furthermore, Ung is associated with resistance to chemotherapeutics, including Dox>>24<<, 25. By down-regulating DNA repair, CP-Dox may directly enhance the antitumor drug effect. These data provide mechanistic insights into CP nanoparticle delivery and support the contention that CP nanoparticles may overcome drug" . _:b418059129 . _:b6368103 "Second, ELPs are useful biopolymers, being non-toxic11, 12, biodegradable, and displaying good pharmacokinetics>>13<<. Third, because ELPs can be produced via genetic engineering, their composition, MW, and polydispersity can be precisely controlled. Fourth, ELPs can be produced with high yield (~100-200 mg/L) in E. coli, and can be easily and rapidly" . . . . _:b6368096 "as numerous studies have shown that objects within this size range accumulate within solid tumors due to the enhanced permeability and retention (EPR) effect, which results from abnormalities of tumor blood and lymphatic vasculature>>4<<. In our view, drug-loaded nanoparticles for cancer drug delivery should:" . _:b6368122 "Other methods to create drug loaded polymer nanoparticles have relied upon: (1) the chemical synthesis of amphiphilic PEG-based biohybrid block copolymers to encapsulate the drug>>18<<, 30-32; (2) the synthesis of complex terpolymers in which the co-polymerization or attachment of fatty acids or cholesterol to the polymer chain drives its self-assembly33, 34; or (3) the design of sophisticated and complex dendrimer" . _:b6368092 . _:b418059164 . _:b6368093 . _:b6368105 "1) so that it exhibits high solubility at body temperature, has long plasma circulation as seen by its area under the concentration-time curve (AUC)>>13<<, and degrades in serum at the rate of 2.5 weight % day-1 13." . _:b6368094 . _:b6368095 . . _:b418059152 . _:b418059197 . _:b6368112 "was generated with a first order half-life of 4.9 \u00B1 0.5 h (CI 95%) and reached a maximum release of 68 \u00B1 3 % (CI 95%) of the initial amount of Dox (Supplementary Table 1), similar to the levels observed with other polymeric hydrazones>>18<<. These data confirm that the covalent linkage to Dox is exceptionally stable at the pH of blood, but that the linkage cleaves at an appreciable rate at a pH that is relevant to endo-lysosomal trafficking." . .