Aptamer–Gadolinium Conjugates for Targeted Magnetic Resonance Imaging of Early-Stage Bladder Cancer

Bladder cancer (BCa) poses a significant threat to human health, with early-stage diagnosis being particularly valuable yet challenging due to the limited availability of highly efficient targeted contrast agents. In this study, we have developed a novel aptamer–gadolinium conjugate (Apt-Gd) designed as a targeted contrast agent for the magnetic resonance imaging (MRI) of early-stage BCa. The synthesis of Apt-Gd involved the direct conjugation of aptamers with chelating agents through a bioorthogonal reaction, followed by gadolinium chelation. Notably, Apt-Gd exhibited high longitudinal relaxivity, exceptional BCa specificity, and good biocompatibility. Furthermore, our research revealed that intravesical instillation of Apt-Gd effectively enhanced the stability of aptamers and boosted the local contrast enhancement in BCa-bearing mice. The utilization of Apt-Gd yielded a satisfactory signal-to-noise ratio during BCa imaging and significantly prolonged the imaging time window. On the whole, the accurate detection of early-stage BCa using Apt-Gd was achieved for the first time, making a breakthrough in BCa diagnosis with promising potential for practical clinical applications.