For the monitoring of PCa relapse, the PSA level in the serum usually decreases to ∼1 pg mL–1 after radical prostatectomy, and a serial increase in the PSA level indicates the recurrence or metastasis of PCa.3 Thus, ultrasensitive detection of PSA featuring a large linear range from ∼1 pg mL–1 to >4 ng mL–1 is crucial for the theranostics of PCa. Here, KLK3 is linked to posterior cortical atrophy.