Figure 3.

Non-optical Biosensors.

(A) Real-time detection of HIV-1 protease activity using a nanopore. Here, a molecule crossing through the nanopore induces current modulation events. The cleaved peptide rises in two differently sized fragments, which results in different residence times and amplitudes. Adapted from [47]. (B) MRI detection of proteolytic activity from Caspase-3/7 in real time. Peptide-stabilized iron oxide (Fe₃O₄) nanoparticles lose their colloidal stability and aggregate near apoptotic cells. T₂-weighted images were obtained from subcutaneously xenografted HepG2 tumors in nude mice. Adapted from [48]. (C) Simultaneous detection of matrix metalloprotease (MMP)-9 activity and evaluation of cellular behavior using interdigitated-array microelectrodes (IDAMs). Here, the bottom layer detects the cells’ morphology change by differences in resistance while the upper layer detects the presence of secreted MMP-2/9 by the change in electrode capacitance. Adapted from [49].