A novel pH-responsive polymer based on amphiphilic N-acetyl histidine and arginine-grafted chitosan was synthesized using N-acetyl histidine as hydrophobic segment and arginine as hydrophilic segment by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-mediated coupling reactions as anticancer drug delivery system for doxorubicin. The structure of the synthesized polymer was confirmed by Fourier transform infrared and 1H nuclear magnetic resonance analysis. Due to self-association behavior, N-acetyl histidine and arginine-grafted chitosan structured nanoparticles with in size range of 204 nm. N-acetyl histidine and arginine-grafted chitosan with different substitution degree of N-acetyl histidine were initially prepared and characterized. The critical micelle concentration decreased with increasing substitution degree of N-acetyl histidine. Furthermore, N-acetyl histidine and arginine-grafted chitosan nanoparticles exhibited an acidic pH-triggered aggregation and disassembling nature. The doxorubicin-encapsulated nanoparticles based on synthesized conjugate ( N-acetyl histidine and arginine-grafted chitosan/doxorubicin nanoparticles) showed a sustained drug release pattern, which could be hastened under acidic pH conditions but delayed with increasing substitution degree of N-acetyl histidine. Anticancer effects demonstrated that N-acetyl histidine and arginine-grafted chitosan/doxorubicin nanoparticles could suppress both sensitive and resistant human breast tumor cell line (MCF-7) efficiently in a dose- and time-dependent pattern. Confocal microscopy results evidenced increased cellular uptake and enhanced retention of the synthesized nanoparticles in drug-resistant cells demonstrating better efficacy of nanoparticles over native doxorubicin. These results suggest that N-acetyl histidine and arginine-grafted chitosan/doxorubicin nanoparticles might be promising carriers for delivery of hydrophobic drug doxorubicin against drug-resistant tumors.
Keywords: Doxorubicin; N-acetyl histidine; arginine; cellular uptake studies; chitosan; cytotoxicity; drug resistance; nanoparticles; pH sensitive; self-assembled.