Herein, we evaluated the tumoral low pH targeting characteristics of pH-responsive
polymer micelles in
cancer targeting
therapy. To design the pH-responsive polymeric
micelles, hydrophilic methyl
ether poly(
ethylene glycol) (
MPEG) and pH-responsive/biodegradable
poly(beta-amino ester) (PAE) were copolymerized using a Michael-type step polymerization, resulting in an MEPG-PAE block copolymer. The amphiphilic
MPEG-PAE block copolymer formed polymeric
micelles with nano-sized diameter by self-assembly, which showed a sharp pH-dependant micellization/demicellization transition at the tumoral acidic pH value (pH 6.4). For the
cancer image and
therapy, fluorescence
dye,
tetramethylrhodamine isothiocyanate (
TRITC), or anticancer
drug,
camptothecin (
CPT), was efficiently encapsulated into the pH-responsive polymeric
micelles (pH-PMs) by a simple
solvent casting method. The
TRITC or
CPT encapsulated pH-PMs (
TRITC-pH-PMs or
CPT-pH-PMs) showed rapid release of
TRITC or
CPT in weakly acidic aqueous (pH 6.4) because they still presented a sharp tumoral
acid pH-responsive micellization/demicellization transition. The pH-PMs with 10wt.% of
TRITC could deliver substantially more fluorescence
dyes to the target
tumor tissue in MDA-MB231 human
breast tumor-bearing mice, compared to the control polymeric
micelles of PEG-
poly(l-lactic acid) (PEG-PLLA). Importantly,
CPT-pH-PMs exhibited significantly increased therapeutic efficacy with minimum side effects by other tissues in
breast tumor-bearing mice, compared to free
CPT and
CPT encapsulated PEG-PLLA
micelles. The tumoral acidic pH-responsive polymeric
micelles are highly useful for
cancer targeting
therapy.