39. Knop K, Hoogenboom R, Fischer D, Schubert US (2010) Poly(ethylene glycol) in drug
delivery: pros and cons as well as potential alternatives. Angew Chem Int Ed 49:6288–6308
40. Yamaoka T, Tabata Y, Ikada Y (1994) Distribution and tissue uptake of poly(ethylene glycol)
with different molecular weights after intravenous administration to mice. J Pharm Sci
83:601–606
41. Pasut G, Veronese FM (2007) Polymer-drug conjugation, recent achievements and general
strategies: polymers in Biomedical Applications. Prog Polym Sci 32:933–961
42. Filpula D, Zhao H (2008) Releasable PEGylation of proteins with customized linkers. Adv
Drug Del Rev 60:29–49
43. Boomer JA, Thompson DH (1999) Synthesis of acid-labile diplasmenyl lipids for drug and
gene delivery applications. Chem Phys Lipids 99:145–153
44. Guo X, Szoka FC (2001) Steric stabilization of fusogenic liposomes by a low-pH sensitive
PEG-diortho ester-lipid conjugate. Bioconjugate Chem 12:291–300
45. Boomer JA, Inerowicz HD, Zhang Z-Y, Bergstrand N, Edwards K, Kim J-M, Thompson DH
(2003) Acid-triggered release from sterically stabilized fusogenic liposomes via a hydrolytic
dPEGylation strategy. Langmuir 19:6408–6415
46. Masson C, Garinot M, Mignet N, Wetzer B, Mailhe P, Scherman D, Bessodes M (2004)
pH-sensitive PEG lipids containing orthoester linkers: new potential tools for nonviral gene
delivery. J Contr Release 99:423–434
47. Hatakeyama H, Akita H, Kogure K, Oishi M, Nagasaki Y, Kihira Y, Ueno M, Kobayashi H,
Kikuchi H, Harashima H (2006) Development of a novel systemic gene delivery system for
cancer therapy with a tumor-specific cleavable PEG-lipid. Gene Ther 14:68–77
48. Sawant RM, Hurley JP, Salmaso S, Kale A, Tolcheva E, Levchenko TS, Torchilin VP (2006)
"SMART" drug delivery systems: double-targeted pH-responsive pharmaceutical
nanocarriers. Bioconjugate Chem 17:943–949
49. Xu H, Deng Y, Chen D, Hong W, Lu Y, Dong X (2008) Esterase-catalyzed dePEGylation of
pH-sensitive vesicles modified with cleavable PEG-lipid derivatives. J Contr Release
130:238–245
50. Boomer JA, Qualls MM, Inerowicz HD, Haynes RH, Patri VS, Kim J-M, Thompson DH
(2009) Cytoplasmic delivery of liposomal contents mediated by an acid-labile cholesterolvinyl ether-PEG conjugate. Bioconjugate Chem 20:47–59
51. Kuai R, Yuan W, Qin Y, Chen H, Tang J, Yuan M, Zhang Z, He Q (2010) Efficient delivery
of payload into tumor cells in a controlled manner by TAT and thiolytic cleavable PEG
co-modified liposomes. Mol Pharm 7:1816–1826
52. Chen D, Jiang X, Huang Y, Zhang C, Ping Q (2010) pH-sensitive mPEG-Hz-cholesterol
conjugates as a liposome delivery system. J Bioact Compat Polym 25:527–542
53. Tomlinson R, Klee M, Garrett S, Heller J, Duncan R, Brocchini S (2002) Pendent chain
functionalized polyacetals that display pH-dependent degradation: a platform for the development of novel polymer therapeutics. Macromolecules 35:473–480
54. Cheng J, Khin KT, Jensen GS, Liu A, Davis ME (2003) Synthesis of linear, β-cyclodextrinbased polymers and their camptothecin conjugates. Bioconjugate Chem 14:1007–1017
55. Tomlinson R, Heller J, Brocchini S, Duncan R (2003) Polyacetal-doxorubicin conjugates
designed for pH-dependent degradation. Bioconjugate Chem 14:1096–1106
56. Vicent MJ, Tomlinson R, Brocchini S, Duncan R (2004) Polyacetal-diethylstilboestrol: a
polymeric drug designed for pH-triggered activation. J Drug Target 12:491–501
57. Rickerby J, Prabhakar R, Ali M, Knowles J, Brocchini S (2005) Water-soluble polyacetals
derived from diphenols. J Mater Chem 15:1849–1856
58. Kaihara S, Matsumura S, Fisher JP (2007) Synthesis and properties of poly[poly(ethylene
glycol)-co-cyclic acetal] based hydrogels. Macromolecules 40:7625–7632
59. Knorr V, Allmendinger L, Walker GF, Paintner FF, Wagner E (2007) An acetal-based
PEGylation reagent for pH-sensitive shielding of DNA polyplexes. Bioconjugate Chem
18:1218–1225
From Biocompatible to Biodegradable: Poly(Ethylene Glycol)s with. . .
185
delivery: pros and cons as well as potential alternatives. Angew Chem Int Ed 49:6288–6308
40. Yamaoka T, Tabata Y, Ikada Y (1994) Distribution and tissue uptake of poly(ethylene glycol)
with different molecular weights after intravenous administration to mice. J Pharm Sci
83:601–606
41. Pasut G, Veronese FM (2007) Polymer-drug conjugation, recent achievements and general
strategies: polymers in Biomedical Applications. Prog Polym Sci 32:933–961
42. Filpula D, Zhao H (2008) Releasable PEGylation of proteins with customized linkers. Adv
Drug Del Rev 60:29–49
43. Boomer JA, Thompson DH (1999) Synthesis of acid-labile diplasmenyl lipids for drug and
gene delivery applications. Chem Phys Lipids 99:145–153
44. Guo X, Szoka FC (2001) Steric stabilization of fusogenic liposomes by a low-pH sensitive
PEG-diortho ester-lipid conjugate. Bioconjugate Chem 12:291–300
45. Boomer JA, Inerowicz HD, Zhang Z-Y, Bergstrand N, Edwards K, Kim J-M, Thompson DH
(2003) Acid-triggered release from sterically stabilized fusogenic liposomes via a hydrolytic
dPEGylation strategy. Langmuir 19:6408–6415
46. Masson C, Garinot M, Mignet N, Wetzer B, Mailhe P, Scherman D, Bessodes M (2004)
pH-sensitive PEG lipids containing orthoester linkers: new potential tools for nonviral gene
delivery. J Contr Release 99:423–434
47. Hatakeyama H, Akita H, Kogure K, Oishi M, Nagasaki Y, Kihira Y, Ueno M, Kobayashi H,
Kikuchi H, Harashima H (2006) Development of a novel systemic gene delivery system for
cancer therapy with a tumor-specific cleavable PEG-lipid. Gene Ther 14:68–77
48. Sawant RM, Hurley JP, Salmaso S, Kale A, Tolcheva E, Levchenko TS, Torchilin VP (2006)
"SMART" drug delivery systems: double-targeted pH-responsive pharmaceutical
nanocarriers. Bioconjugate Chem 17:943–949
49. Xu H, Deng Y, Chen D, Hong W, Lu Y, Dong X (2008) Esterase-catalyzed dePEGylation of
pH-sensitive vesicles modified with cleavable PEG-lipid derivatives. J Contr Release
130:238–245
50. Boomer JA, Qualls MM, Inerowicz HD, Haynes RH, Patri VS, Kim J-M, Thompson DH
(2009) Cytoplasmic delivery of liposomal contents mediated by an acid-labile cholesterolvinyl ether-PEG conjugate. Bioconjugate Chem 20:47–59
51. Kuai R, Yuan W, Qin Y, Chen H, Tang J, Yuan M, Zhang Z, He Q (2010) Efficient delivery
of payload into tumor cells in a controlled manner by TAT and thiolytic cleavable PEG
co-modified liposomes. Mol Pharm 7:1816–1826
52. Chen D, Jiang X, Huang Y, Zhang C, Ping Q (2010) pH-sensitive mPEG-Hz-cholesterol
conjugates as a liposome delivery system. J Bioact Compat Polym 25:527–542
53. Tomlinson R, Klee M, Garrett S, Heller J, Duncan R, Brocchini S (2002) Pendent chain
functionalized polyacetals that display pH-dependent degradation: a platform for the development of novel polymer therapeutics. Macromolecules 35:473–480
54. Cheng J, Khin KT, Jensen GS, Liu A, Davis ME (2003) Synthesis of linear, β-cyclodextrinbased polymers and their camptothecin conjugates. Bioconjugate Chem 14:1007–1017
55. Tomlinson R, Heller J, Brocchini S, Duncan R (2003) Polyacetal-doxorubicin conjugates
designed for pH-dependent degradation. Bioconjugate Chem 14:1096–1106
56. Vicent MJ, Tomlinson R, Brocchini S, Duncan R (2004) Polyacetal-diethylstilboestrol: a
polymeric drug designed for pH-triggered activation. J Drug Target 12:491–501
57. Rickerby J, Prabhakar R, Ali M, Knowles J, Brocchini S (2005) Water-soluble polyacetals
derived from diphenols. J Mater Chem 15:1849–1856
58. Kaihara S, Matsumura S, Fisher JP (2007) Synthesis and properties of poly[poly(ethylene
glycol)-co-cyclic acetal] based hydrogels. Macromolecules 40:7625–7632
59. Knorr V, Allmendinger L, Walker GF, Paintner FF, Wagner E (2007) An acetal-based
PEGylation reagent for pH-sensitive shielding of DNA polyplexes. Bioconjugate Chem
18:1218–1225
From Biocompatible to Biodegradable: Poly(Ethylene Glycol)s with. . .
185