Non-Traditional Intrinsic Luminescence (NTIL): Dynamic Quenching Demonstrates the Presence of Two Distinct Fluorophore Types Associated with NTIL Behavior in Pyrrolidone-Terminated PAMAM Dendrimers

Abstract

Historically, poly(amidoamine) (PAMAM) dendrimers were the first macromolecular structures reported to exhibit “non-traditional intrinsic luminescence” (NTIL) properties. Initially this unique intrinsic luminescent property suggested the possibility of dendrimer based biological imaging without the need for conjugating external labels. Unfortunately, low NTIL intensity levels exhibited by most simple surface modified PAMAMs presented a serious barrier to progress in that area. Unexpectedly, a simple surface modification of amine terminated PAMAM dendrimers with N-(4-carbomethoxy)pyrrolidone groups (4-CMP) was found to dramatically increase NTIL fluorescence intensity (i.e., >50 fold) while substantially enhancing biocompatibility and reducing cytotoxicity/complement activation properties. This current study focuses on the use of conventional and time-resolved spectroscopic measurements to characterize the NTIL behavior of 4-CMP PAMAM dendrimers over four generation levels (i.e., G2-G5). We describe and di...