<sup>99m</sup>Tc-Labeled D‑Type PTP as a Plectin-Targeting\nSingle-Photon Emission Computed Tomography Probe for Hepatocellular\nCarcinoma Imaging

Plectin,\na scaffolding protein overexpressed in tumor\ncells, plays\na significant role in hepatocellular carcinoma (HCC) proliferation,\ninvasion, and migration. However, the use of L-type peptides for targeting\nplectin is hindered by their limited stability and retention. We designed\na D-type plectin-targeting peptide (<sup>D</sup>PTP) and developed\na novel single-photon emission computed tomography (SPECT) probe for\nHCC imaging. The <sup>D</sup>PTP targeting ability was evaluated <i>in vitro</i> using flow cytometry and <i>ex vivo</i> fluorescence imaging. <sup>99m</sup>Tc radiolabeling was performed\nusing tricine and ethylenediamine-<i>N</i>,<i>N</i>′-diacetic acid (EDDA) as coligands after modification with\n6-hydrazino nicotinamide (HYNIC) at the N termini of <sup>D</sup>PTP.\nThe radiochemical purity (RCP), <i>in vitro</i> stability,\nand binding affinity of the prepared <sup>99m</sup>Tc-HYNIC-<sup>D</sup>PTP were analyzed. Tumor uptake, metabolic stability, biodistribution,\nand pharmacokinetics of <sup>99m</sup>Tc-HYNIC-<sup>D</sup>PTP were\ninvestigated and compared with those of <sup>99m</sup>Tc-labeled L-type\nPTP (<sup>99m</sup>Tc-HYNIC-PTP) in HCC tumor-bearing mice. <sup>D</sup>PTP could be efficiently radiolabeled with <sup>99m</sup>Tc using\nthe HYNIC/tricine/EDDA system with a high RCP and good <i>in\nvitro</i> stability. Compared with the L-type PTP, <sup>D</sup>PTP exhibited improved targeting ability, and <sup>99m</sup>Tc-HYNIC-<sup>D</sup>PTP displayed higher tumor uptake, better metabolic stability,\nlonger blood circulation time, and lower kidney retention, resulting\nin superior imaging performance and biodistribution <i>in vivo</i>. <sup>99m</sup>Tc-HYNIC-<sup>D</sup>PTP has great potential as a\nnovel SPECT probe for diagnosing HCC.