BULK AND SOLUTION PROPERTIES OF PEPTIDE-POLYMER CONJUGATES - Biologically-Responsive Hybrid Biomaterials - page 27

PTHF- b -PLLys 30 )]. This material was further modified with sugar moieties -
either D-gluconolactone or lactobionolactone - and employed as a nano-carrier
for doxorubicin as a model anticancer drug [98].
The diameter of the micelles formed with the ABC triblock copolymer
poly(ethylene glycol)- b -poly( L -lactide)- b -poly( L -glutamic acid) (PEG- b -PLLac-
b -PLGA) was found to depend on the PLGA block length and on the ratio of
water to dimethylformamide (DMF) in solution. The system exhibits a reversible
transition at or below pH 3.2 with spherical micelles shifting to a connected-rod
morphology [99].
Using AFM and light scattering, micelles were observed from a triblock
copolymer containing a central oligopeptide segment sandwiched between
hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(butyl acrylate)
(PBA) blocks [PEO- b -Arg 10 - b -PBA] [100]. The biofunctional arginine segment,
mimicking cell penetrating peptides, is interestingly confined at the hydrophilic
and hydrophobic interface, between micelle core and corona. A recent approach
employed the co-micellization of poly( L -glutamic acid)- b -poly(propylene oxide)-
b -poly( L -glutamic acid) (PLGA- b -PPO- b -PLGA) and poly(ethylene glycol)- b -
poly(propylene oxide) (PEG- b -PPO) in water to produce PPO core blocks
surrounded by poly( L -glutamic acid) and poly(ethylene glycol) mixed corona
chains [101]. DLS showed that micelle radii increased at lowered temperatures
(approaching 20 °C) due to expansion of the PPO core and decreased at acidic

T>LCST

T

51°C 66°C

Fig. 11. Schematic diagram showing effect of temperature increase from 51°C to 66°C on micelles
formed from Jeffamine- b -PLGA 30 . Adapted from [102].