A noninvasive MR/CT/NIR fluorescence (NIRF) trimodal contrast agent made up of Au and gadolinium coupled to prostate-specific membrane ligand 1 (PSMA1) (AG-Gd@PSMA1 NPs, AGGP) was developed to detect and quantify the prostate-specific membrane antigen (PSMA) expression in prostate cancer (PCa) lesions. Here, PSMA1 is linked to prostate cancer.