Oxidation And Coordination Responsive Selenium/tellurium-containing Polymer Assemblies

Stimuli-responsive polymers are defined as polymers that can undergo physical or chemical changes in response to environmental changes.Stimuli-responsive polymers can be designed in structures and programmed in functions,therefore they have been developed greatly in recent years as a result of their perspective use in drug release,gene delivery,disease diagnosis,smart devices et al.Although progresses have been made in the application of stimuli-responsive polymers for controlled release systems,there are still some challenges remained.One is due to the very low concentration of biological signals or the biomarkers in physilogical environemnts,which makes it difficult to fabricate smart systems with sensitive response to such stimuli.The thesis is focused on addressing two questions existed in the controlled release systems: how to achieve response to ultra-low-concentration chemical signals and how to modulate drug release kinetics using biomolecules in physiological environments.Based on selenium/tellurium containing polymers,detailed studies of their application as oxidation and coordination responsive release systems were carried out.The work includes three parts as follows:1)A ?-ray stimuli-responsive selenium-containing polymer hydrogel was demonstrated to provide a promising way to combine chemo-and radio-therapies.The hydrogel was designed and prepared by combining a diselenide-containing polymer with a peptide amphiphile.The ?-radiation could be used to control the degradation of hydrogel components,yielding a smart gel-sol transition.The reason of the response was ascribed to the diselenide-containing polymer being broken by the reactive oxygen species generated upon irradiation.The diselenide-containing polymer hydrogel could be used for programmable responsive systems for combined chemo-and radiotherapies.2)Tellurium-containing polymer self-assemblies were reported for the first time as ultra-sensitive oxidation responsive aggregates.Tellurium was introduced to water soluble polymers,which enabled the smart response to reactive oxygen species of biologically relevant concentration.Further studies revealed that the tellurium-containing polymer could respond to ?-radiation of clinical dosage 2 Gy.Therefore,the tellurium-containing polymer could work as a new platform for combined chemo-and radio-therapies with enhanced ?-radiation sensitivity.3)Novel competitive coordination responsive systems were fabricated on the basis of selenium/tellurium containing polymers for tuning the release kinetics.The coordination chemistry between selenium/tellurium and platinum was designed to enable the load of platinum based drugs.Through the competitive coordination of biomolecules,the drugs could be released in a controlled manner.Furthermore,the release kinetics could be modulated by the competitive ligands due to their different coordination abilities.The competitive coordination responsive mechanism is versatile and may be used for the design and preparation of future responsive biomedical nanomaterials.