Enhancement of the chemiluminescence of two isoluminol derivatives by nanoencapsulation with natural cyclodextrins.

The chemiluminescence (CL) yield of two isoluminol derivatives, N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), is remarkably increased in the presence of natural cyclodextrins (CDs). The most notable effect is produced by the addition of gamma-CD that produces enhancements up to 15-fold in the light emission of both compounds. Although proton nuclear magnetic resonance ((1)H NMR) measurements prove the encapsulation of these luminescent reagents in the CDs, with more stable associations by decreasing the width of the CD cavity, the improvement in the light emission of ABEI and AHEI is mainly due to the topology of the complexes. Evaluation of the rotating frame Overhauser effect spectroscopy (ROESY) spectra cross-peaks combined with semirigid-docking simulations has been used to gather information about the spatial conformation of the guest molecules into the CDs. These calculations have shown that a deeper inclusion in the CD cavity of the heterocyclic moiety of the luminescent molecules is directly related with a higher enhancement in the CL. The augment of the CL by natural CDs is of interest for increasing the detection limit in biochemical assays or liquid chromatography, for example, in which the CL of these compounds serves to quantify other molecular species that may take part, direct or indirectly, in the luminescent reaction.