Self-assembly of chitosan (CS) particles and poly(L-glutamic acid)-b-poly(propylene oxide)-b-poly(L-glutamic acid) (GPG) triblock copolymer micelles was investigated.The CS particles are cationic hydrogels

while the GPG micelles have anionic poly(L-glutamic acid) shells.Therefore

the two kinds of polyelectrolyte particles can electrostatic self-assemble into microscopic CS/GPG conjugates.The CS/GPG ratio range for the CS particles and GPG micelles to electrostatic self-assemble into a sustained CS/GPG conjugates solution was established.The CS/GPG conjugates were prepared by dropping CS particle solution into GPG micelle solution under stirring

with the CS/GPG ratio of 0.25/10

0.5/10

0.75/10

1.0/10

1.25/10

1.5/10

1.75/10 and 2/10.The CS/GPG conjugates are stable in water when the CS/GPG ratio is equal or less than 1.5/10.The particle size distribution of GPG micelles

CS particles

and CS/GPG conjugates were determined by the dynamic light scattering.GPG micelles show a narrow distribution with the average Rh of 59 nm

while the CS particles and CS/GPG conjugates show much broaden distributions with the Rh of 177 nm and 364 nm respectively.Zeta potential tests show that the GPG micelles exhibit surface negative charge of -52 mV and the CS particles exhibit surface positive charge of 22 mV.The surface charge of CS/GPG conjugates are negative and the average absolute value of the surface charge decreases with increasing CS amount.In vitro drug release behaviors of the Aspirin (Asp)-loaded CS particles

Doxorubicin (DOX)-loaded GPG micelles

and the Asp-CS/DOX-GPG conjugates (CS/GPG=1.5/10) were studied as a function of pH value.Both Asp and DOX show pH sensitive release behaviors in all the three drug-loaded systems.Moreover

the release rate of Asp shows a dramatic decrease in the Asp-CS/DOX-GPG system

as compared with the Asp-CS nanoparticles.