mostly deprotonated. The results in Figure 7-6 clearly show that the uptake is not driven by

electrostatic interactions between the positively charged amine of amitriptyline and the

deprotonated and negatively charged carboxylic acid groups of the nanoparticles. In the case of

non-imprinted nanoparticles, the uptake is driven by non-specific hydrophobic interactions

between the nanoparticles and the hydrophobic aromatic rings and aliphatic carbon chain of

amitriptyline, which is likely adsorbed on the pore walls through its non-polar moiety with the

protonated amine group facing the aqueous solution. The uptake being driven by hydrophobic

interactions instead of hydrogen bondings or electrostatic interactions in water is well known and

has already been described for other molecularly imprinted polymers used for molecular

recognition in aqueous conditions.267 This is not the case when binding studies are carried out in

less polar organic solvents such as dichloromethane268 Or toluene,269 Since their dielectric

constants are not as high as for water and do not significantly break polar host-guest interactions.


 80

 ~60


 I ~I~ M IP,
 S20 1 M IP,


 0 5 10 15
 Nanoparticle amount (mg)

Figure 7-6. Uptake of amitriptyline by the non-molecularly imprinted nanoparticles MIP1 (K,~
 1600), MIP2 (K, ~ 1000), and MIP3 (K, ~ 1100). The lines are provided to highlight
 the trends.

 Similar binding experiments of amitriptyline were carried out for the molecularly

imprinted nanoparticle samples MIP4, MIPS, and MIP6 (Figure 7-7). MIP6 that does not contain

any polar carboxylic acid groups has a high affinity for amitriptyline, so this confirms the results