the present invention relates to biocompatible and biodegradable stimuli - sensitive polymeric nanoparticles , which were formed by ion - ion interaction in aqueous media . synthetic and biological macromolecules with ionizable functional groups are capable of forming nanoparticles whose size and surface properties are sensitive to environmental influences such as ph , temperature and salt concentration . nanodevices are designed for therapeutic applications as drug and nucleic acid carriers , and / or for mri diagnosis as contrast agents . these nanodevices are designed for therapeutic applications as targeted drug carriers . additionally , they can be used as contrast agents for mri diagnosis . these nanosystems are also potential carriers for delivery of active ingredients as dna , rna , short interfering rna , antisense oligonucleotides , and triple helix forming oligonucleotides etc . for pharmaceutical applications . their adjustable size offers yet another advantage .