obtained previously for MIP1, MIP2, and MIP3, where it was observed that the hydrophobic

interactions play a significant role in the binding. Nevertheless, as the amount of carboxylic acids

in the molecularly imprinted nanoparticles is increased, the uptake is significantly increased as

well (partition coefficient values in captions of Figure 7-7), contrary to the non-imprinted

nanoparticles. This clearly indicates that, although polar interactions alone are obviously weaker

than hydrophobic interactions in aqueous solutions, the presence of specific and shape-persistent

amitriptyline recognition sites formed from the weak electrostatic/hydrogen bonding interactions

between MAA and amitriptyline during the imprinting stage significantly increases the uptake,

and consequently the nanocapsules binding specificity. Prior to carrying out the binding studies

and as indicated in the experimental section, the nanoparticles were extensively washed at least

five times with tetrahydrofuran (THF) until no residual amitriptyline could be detected by UV-

vis spectroscopy in the centrifugation supernatants. Nevertheless, it should be noticed that traces

of amitriptyline probably remained after nanoparticle synthesis and template extraction in MIP4,

MIPS, and MIP6 aS shown by the slightly lower uptake (and partition coefficient value) of MIP4

compared to MIP1.

 80

 60 -


 ~4 1- MI P,
 S201 MI P,


 0 5 10 15
 Nanoparticle amount (mg)

Figure 7-7. Uptake of amitriptyline by the nanoparticles molecularly imprinted with
 amitriptyline: MIP4 (K, ~ 1200), MIPS (K, ~ 1800), and MIP6 (K, ~ 2700). The lines
 are provided to highlight the trends.