There have been ongoing efforts to develop more sensitive and fast quantitative screening of cancer markers by use of fluorometric immunochromatographic test strips (ICTS) since the remarkable advances in fluorescent nanomaterials. Semiconducting polymer dots (Pdots) have recently emerged as a new type of biocompatible fluorescent probe with extraordinary brightness which is suitable for biological and clinical use. Here, we developed Pdot-based ICTS for quantitative rapid screening of prostate-specific antigen (PSA), α-fetoprotein (AFP), and carcinoembryonic antigen (CEA) in 10 min. Through use of the ultrahigh fluorescence brightness of Pdots, this immunosensor enabled much better detection sensitivity (2.05, 3.30, and 4.92 pg/mL for PSA, AFP, and CEA, respectively), in which the detection limit is at least 2 orders of magnitude lower than that of conventional fluorometric ICTS. Furthermore, we performed proof-of-concept experiments for simultaneous determination of multiple tumor markers in a single test strip. These results demonstrated that this Pdot-based ICTS platform is a promising candidate for developing new generations of point-of-care diagnostics. To the best of our knowledge, this is the first example of Pdot-based ICTS with multiplexing capability.

This article describes the design and synthesis of donor-bridge-acceptor-based semiconducting polymer dots (Pdots) that exhibit narrow-band emissions, ultrahigh brightness, and large Stokes shifts in the near-infrared (NIR) region. We systematically investigated the effect of π-bridges on the fluorescence quantum yields of the donor-bridge-acceptor-based Pdots. The Pdots could be excited by a 488 or 532 nm laser and have a high fluorescence quantum yield of 33% with a Stokes shift of more than 200 nm. The emission full width at half-maximum of the Pdots can be as narrow as 29 nm, about 2.5 times narrower than that of inorganic quantum dots at the same emission wavelength region. The average per-particle brightness of the Pdots is at least 3 times larger than that of the commercially available quantum dots. The excellent biocompatibility of these Pdots was demonstrated in vivo, and their specific cellular labeling capability was also approved by different cell lines. By taking advantage of the durable brightness and remarkable stability of these NIR fluorescent Pdots, we performed in vivo microangiography imaging on living zebrafish embryos and long-term tumor monitoring on mice. We anticipate these donor-bridge-acceptor-based NIR-fluorescent Pdots with narrow-band emissions to find broad use in a variety of multiplexed biological applications.

Semiconducting polymer dots (Pdots) recently have emerged as a new class of extraordinarily bright fluorescent probes with promising applications in biological imaging and sensing. Herein multicolor semiconducting polymer nanoparticles (Pdots) were designed using benzothiadiazole (BT) as the acceptor, and various types of donors were incorporated to modulate their emission wavelengths. Specific cellular targeting and in vivo biotoxicity as well as microangiography imaging on zebrafish indicated these BTbased Pdots are promising candidates for biological applications.