Figure 2.

Optically Based Sensors.

(A) Matrix metalloprotease (MMP)-2/9 detection using a near-IR (NIR-II)-emitting quantum dot (QD) and a quencher (Q). When the enzymes are active, fluorescence (FL) increases and nearby cells are marked. This system was able to detect colon cancer in mouse models. Adapted from [35]. (B) Crown-shaped assembly of 40-nm plasmonic gold nanoparticles bridged by a peptide sequence for Caspase-3/7 detection. Scattered light from the plasmonic assembly is proportional to proteolytic activity, and particles can freely diffuse within the cell after cleavage. Adapted from [36]. (C) Multifunctional nanohybrid comprising Gd-doped CuS nanodisks, a fluorescent probe for MMP-2 activity determination and tumor cell-targeting peptide. After proteolytic cleavage of the activatable probe, tumor margins are determined by FL imaging. Thus, the nanohybrids accumulate on tumor cells allowing MRI with increased spatiotemporal resolution and subsequent photothermal therapy (PTT). Adapted from [46].