Ultrabright Dibenzofluoran-Based Polymer Dots with NIR-IIa Emission Maxima and Unusual Large Stokes Shifts for 3D Rotational Stereo Imaging.

Emerging organic molecules with emissions in the second near-infrared (NIR-II) region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR-IIa (1300 nm) region faces challenges due to the intrinsic energy gap law. Up to the current stage, all reported organic NIR-IIa emitters belong to polymethine-based dyes with small Stokes shifts (<50 nm) and low quantum yield (QY; ≤0.015%). However, such polymethines have proved to cause self-absorption with constrained emission brightness, limiting advanced development in deep-tissue imaging. Here a new NIR-IIa scaffold based on rigid and highly conjugated dibenzofluoran core terminated by amino-containing moieties that reveal emission peaks of 1230-1305 nm is designed. The QY is at least 10 times higher than all synthesized or reported NIR-IIa polymethines with extraordinarily large Stokes shifts of 370-446 nm. DBF-BJ is further prepared as a polymer dot to demonstrate its in vivo 3D stereo imaging of mouse vasculature with a 1400 nm long-pass filter.

Effect of carbon spacer length on the antibacterial properties of zwitterionic poly(sulfobetaine) type copolymeric brushes and their application in wound healing.

Creating infection resistant polymer brushes possessing antiadhesive, bactericidal and cell-compatible features can be regarded as a promising approach to prevent biomaterial-associated infections. In this work, polysulfobetaine type zwitterionic homo- and copolymer brushes with varying spacer lengths (charge separation distance between zwitterions, n = 3, 6 or 12) were allowed to grow onto a tartaric acid based aliphatic polyester substrate using surface initiated atom transfer radical polymerization. All of the brush modified surfaces were thoroughly characterized and assessed for their anti-infective performances in vitro. Strikingly, a suitable copolymer composition, i.e., polyZ6-co-Z12 (50/50 copolymer of polysulfobetaine methacrylates with 6 and 12 spacer lengths), was observed to inhibit bacterial growth completely and its activity was sustained for a long time (>3 months). Surprisingly, its antibacterial effect was found to be bactericidal, as is evident from live-dead staining of residual dead bacterial cells that can be easily released by exposing the surface to salt solution, thereby regenerating the surface. However, all of the other copolymer as well as homopolymer brushes exhibited bacteriostatic behavior. An attempt was made to understand the peculiar behavior of this particular brush composition. Nevertheless, the biocidal and also protein repellent brush did not display any cytotoxicity towards human cells, making it an ideal substrate to be used as an infection resistant biomedical implant. Animal studies further confirmed that this particular copolymeric brush modified scaffold can be a promising anti-infective wound dressing material with rapid wound healing effects as compared to the unmodified scaffold.

Development of Stereo NIR-II Fluorescence Imaging System for 3D Tumor Vasculature in Small Animals.

Near-infrared-II (NIR-II, 1000-1700 nm) fluorescence imaging boasts high spatial resolution and deep tissue penetration due to low light scattering, reduced photon absorption, and low tissue autofluorescence. NIR-II biological imaging is applied mainly in the noninvasive visualization of blood vessels and tumors in deep tissue. In the study, a stereo NIR-II fluorescence imaging system was developed for acquiring three-dimension (3D) images on tumor vasculature in real-time, on top of the development of fluorescent semiconducting polymer dots (IR-TPE Pdots) with ultra-bright NIR-II fluorescence (1000-1400 nm) and high stability to perform long-term fluorescence imaging. The NIR-II imaging system only consists of one InGaAs camera and a moving stage to simulate left-eye view and right-eye view for the construction of 3D in-depth blood vessel images. The system was validated with blood vessel phantom of tumor-bearing mice and was applied successfully in obtaining 3D blood vessel images with 0.6 mm- and 5 mm-depth resolution and 0.15 mm spatial resolution. The NIR-II stereo vision provides precise 3D information on the tumor microenvironment and blood vessel path.

Molecular Design of Ultrabright Semiconducting Polymer Dots with High NIR-II Fluorescence for 3D Tumor Mapping.

Fluorescence probes emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with the ability for deep-tissue imaging in mammals herald a new era in surgical methodology. However, the brightness of these NIR-II probes is still far from satisfactory due to their low fluorescence quantum yields (QYs), preventing the observation of high-resolution images such as whole-organ vascular networks in real time. Described here is the molecular engineering of a series of semiconducting polymer dots (Pdots) incorporated with aggregation-induced emission moieties to exhibit the QYs as high as 14% in the NIR-II window. Benefiting from the ultrahigh brightness, a 1400 nm long-pass filter is utilized to realize in vivo 3D tumor mapping in mice. To further understand how the geometrical and electron structures of the semiconducting polymers affect their optical properties, the in-depth and thorough density-functional theory calculations are performed to interpret the experimental results. This study lays the groundwork for further molecular design of highly bright NIR-II Pdots.