Hyperbranched Polymer Dots with Strong Absorption and High Fluorescence Quantum Yield for In Vivo NIR-II Imaging.

In order to improve the fluorescence quantum yield (QY) of NIR-II-emitting nanoparticles, D-A-D fluorophores are typically linked to intramolecular rotatable units to reduce aggregation-induced quenching. However, incorporating such units often leads to a twisted molecular backbone, which affects the coupling within the D-A-D unit and, as a result, lowers the absorption. Here, we overcome this limitation by cross-linking the NIR-II fluorophores to form a 2D polymer network, which simultaneously achieves a high QY by well-controlled fluorophore separation and strong absorption by restricting intramolecular distortion. Using the strategy, we developed polymer dots with the highest NIR-II single-particle brightness among reported D-A-D-based nanoparticles and applied them for imaging of hindlimb vasculatures and tumors as well as fluorescence-guided tumor resection. The high brightness of the polymer dots offered exceptional image quality and excellent surgical results, showing a promising performance for these applications.

Fluorescent Polymer Dot-Based Multicolor Stimulated Emission Depletion Nanoscopy with a Single Laser Beam Pair for Cellular Tracking.

Stimulated emission depletion (STED) nanoscopy provides subdiffraction resolution while preserving the benefits of fluorescence confocal microscopy in live-cell imaging. However, there are several challenges for multicolor STED nanoscopy, including sophisticated microscopy architectures, fast photobleaching, and cross talk of fluorescent probes. Here, we introduce two types of nanoscale fluorescent semiconducting polymer dots (Pdots) with different emission wavelengths: CNPPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-(1-cyanovinylene-1,4-phenylene)]) Pdots and PDFDP (poly[{9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorene}-alt-co-{2,5-bis (N,N'-diphenylamino)-1,4-phenylene}]) Pdots, for dual-color STED bioimaging and cellular tracking. Besides bright fluorescence, strong photostability, and easy bioconjugation, these Pdots have large Stokes shifts, which make it possible to share both excitation and depletion beams, thus requiring only a single pair of laser beams for the dual-color STED imaging. Long-term tracking of cellular organelles by the Pdots has been achieved in living cells, and the dynamic interaction of endosomes derived from clathrin-mediated and caveolae-mediated endocytic pathways has been monitored for the first time to propose their interaction models. These results demonstrate the promise of Pdots as excellent probes for live-cell multicolor STED nanoscopy.

Hypoxia-Activated PEGylated Conditional Aptamer/Antibody for Cancer Imaging with Improved Specificity.

Aptamers and antibodies, as molecular recognition probes, play critical roles in cancer diagnosis and therapy. However, their recognition ability is based on target overexpression in disease cells, not target exclusivity, which can cause on-target off-tumor effects. To address the limitation, we herein report a novel strategy to develop a conditional aptamer conjugate which recognizes its cell surface target, but only after selective activation, as determined by characteristics of the disease microenvironment, which, in our model, involve tumor hypoxia. This conditional aptamer is the result of conjugating the aptamer with PEG5000-azobenzene-NHS, which is responsive to hypoxia, here acting as a caging moiety of conditional recognition. More specifically, the caging moiety is unresponsive in the intact conjugate and prevents target recognition. However, in the presence of sodium dithionite or hypoxia (<0.1% O2) or in the tumor microenvironment, the caging moiety responds by allowing conditional recognition of the cell-surface target, thereby reducing the chance of on-target off-tumor effects. It is also confirmed that the strategy can be used for developing a conditional antibody. Therefore, this study demonstrates an efficient strategy by which to develop aptamer/antibody-based diagnostic probes and therapeutic drugs for cancers with a unique hypoxic microenvironment.

Elasticity of cardiac cells on the polymer substrates with different stiffness: an atomic force microscopy study.

Influences of substrate stiffness on mechanical properties of cardiac myocytes and fibroblasts were investigated by cell elasticity measurement with atomic force microscopy. The cells were cultured on collagen-coated polyacrylamide substrates with gradient rigidity. While cardiac myocytes showed no evident change in cell elasticity on different substrates, cardiac fibroblasts displayed the non-monotonic dependence on substrate stiffness with a maximum elastic modulus. Moreover, the elasticity change of cardiac fibroblasts with substrates stiffness was found to be regulated by actin filaments. Study of the effect of substrate stiffness on cell elasticity for different cardiac cells provides new information for the better understanding of cardiac physiology and pathology.

Gold nanorod-embedded electrospun fibrous membrane as a photothermal therapy platform.

A strategy of using a gold nanorod (GNR)-loaded electrospun membrane as a photothermal therapy platform of cancer is reported. The strategy takes both the advantages of the excellent photothermal properties of GNRs to selectively kill the cancerous cells, and the widely used biodegradable electrospun membrane to serve as GNR-carrier and surgical recovery material. PEG modified GNRs were embedded into the electrospun fibrous membrane which was composed of PLGA and PLA-b-PEG with an 85:15 ratio. After incubation with the cells in the cell culture medium, the PEG-GNRs were released from the membrane and taken up by cancer cells, allowing the generation of heat upon NIR irradiation to induce cancer cell death. We have demonstrated that the use of PEG-GNR-embedded membrane selectively killed the cancerous cells and effectively inhibited cancer cell proliferation though in vitro experiments. The PEG-GNRs-loaded membrane is a promising material for postsurgical recovery of cancer.

High-purity prostate circulating tumor cell isolation by a polymer nanofiber-embedded microchip for whole exome sequencing.

Handpick single cancer cells: a modified NanoVelcro Chip is coupled with ArcturusXT laser capture microdissection (LCM) technology to enable the detection and isolation of single circulating tumor cells (CTCs) from patients with prostate cancer (PC). This new approach paves the way for conducting next-generation sequencing (NGS) on single CTCs.