Early detection of gastrointestinal cancers faces significant challenges, mainly including the invasiveness of wired endoscopes, the limited tissue penetration depth of white light capsule endoscopy (CE), and the low signal-to-noise ratio (SNR) and contrast caused by excitation light interference in traditional fluorescence imaging CE. Herein, we developed a near-infrared-IIb (NIR-IIb) window-excited fluorescence imaging capsule endoscope (FICE) for the high-contrast diagnosis of early-stage gastrointestinal cancers. The FICE employs a 1550-nm central wavelength NIR-IIb laser diode to precisely shape the excitation beam for selective activation of upconversion nanoprobes (UCNPs) aggregates in lesion tissues, stimulating them to emit 540 nm green fluorescence-the most sensitive wavelength for CMOS imaging chips. Utilizing 1550 nm excitation light facilitates enhanced penetration into biological tissues and the detection method with an excitation-emission spectral separation of more than 1000 nm effectively eliminates background interference, thereby yielding diagnostic images with ultrahigh SNR and superior contrast. Proof-of-concept experiments in nude mice demonstrated that this FICE achieved specific fluorescence detection of subcutaneous and colonic mucosal tumors with a penetration depth of up to 6 mm and fluorescence-to-background contrast ratios exceeding 90%. Ex vivo validation in porcine tissues confirmed the FICE's imaging capability within realistic anatomical environments. Furthermore, we designed a wireless power supply and posture control system to provide continuous energy and precise motion control for the FICE. To our knowledge, this paper presents the first NIR-IIb-excited FICE, offering a non-invasive, high-contrast and high-SNR diagnostic tool for early gastrointestinal cancer detection and demonstrating remarkable clinical potential.
Wang et al. (Sat,) studied this question.