Quantitative and noninvasive measurement of protease activities has remained an imaging challenge in deep tissues such as the lungs. Here, we designed a dual-radiolabeled probe for reporting the activities of proteases such as matrix metalloproteinases (MMPs) with multispectral single photon emission computed tomography (SPECT) imaging. A gold nanoparticle (NP) was radiolabeled with 125I and 111In and functionalized with an MMP9-cleavable peptide to form a multispectral SPECT imaging contrast agent. In another design, incorporation of 199Au radionuclide into the metal crystal structure of gold NPs provided a superior and stable reference signal in lungs, and 111In was linked to the NP surface via a protease-cleavable substrate, which can serve as an enzyme activity reporter. This work reveals strategies to correlate protease activities with diverse pathologies in a tissue-depth independent manner.
A biomimetic polydopamine (PD)-based strategy was employed for presenting antibodies on gold nanorods (NRs) to target cancer cells for photothermal therapy. PD was polymerized onto NRs, and epidermal growth factor receptor antibodies (anti-EGFR) were immobilized onto the layer. Anti-EGFR-PD-NRs specifically bound to EGFRoverexpressing cells as quantified by optical coherence tomography, and illumination enhanced cell death compared to non-irradiated or antibody-free controls.