Contrast agents temperature-sensitive

The term responsive (elsewhere indicated as smart ) refers to diagnostic agents whose contrasting properties are sensitive to a given physicochemical variable that characterizes the microenvironment in which the probe is distributed (116-117). Typical parameters of primary diagnostic relevance include pH, temperature, enzymatic activity, redox potential and the concentration of specific ions, and low-weight metabolites. 

Temperature dependence proton relaxivity 188 relaxation rate 144-5 Temperature-sensitive contrast agents 218-19 Th -" 368 Ti "" 347 Tilt angle 242 Time constant 14 Time correlation functions 76 Time-dependent mechanism 14 Time-dependent perturbation methods 23 Time-dependent perturbation theory 45-8 Titanium(III) 115,134-5,161 TPEN 224 TPPS 219... 

Gadolinium encapsulated liposomes are under development (Fossheim et al. 2000). The idea is to develop liposomes that undergo gel to liquid phase transition at a particular temperature i.e. they would behave as an on-off messenger, switched on when a particular temperature has been reached. Different liposomes would be sensitive to different temperatures so a specific liposome would be specific to an application either ablation or hyperthermia. Other contrast agents in development are necrosis avid agents (Ni et al. 2002). These are injected i.v. and taken up within areas of necrosis over a period of several hours and then persist for a few days. Correlation with histopathology shows that these agents can provide same day assessment but not same-session of treatment efficacy. 

Several biological environments were successfully detected by rare earth complexes. Since their MRI contrast profiles were significantly controlled by the dynamics of the coordinated water molecules and molecular tumbling, several external stimuli such as pH, Pqj, and temperature can be sensitively sensed. Further sophisticated contrast agents specific for certain damaged tissues can be developed by bottom-up synthesis of rare earth complexes. 

The application of ethoxy(trimethylsilyl)acetylene as a dehydrating agent was also extended to polyanhydride synthesis (eq 5). In contrast to traditional methods, this was carried out at low temperature (20 0 °C) by the electrophilic addition-elimination reaction of ethoxy(trimethylsilyl)acetylene, avoiding decomposition due to heating of sensitive monomers and polymers. ... 

---