Multiscale Self-Assembly of a Phenyl-Flanked Diketopyrrolopyrrole Derivative: A Solution-Processable Building Block for π-Conjugated Supramolecular Polymers.

We report a solution-processable π-conjugated molecular building block (denoted as PhDPP) consisting of a rigid and planar core of phenyl-flanked diketopyrrolopyrrole and "soft" branched alkoxy chains that endow the solubility in a variety of organic solvents. Intermolecular hydrogen bonding in PhDPP was revealed in nonpolar solvents above a threshold of concentration and below a critical point of temperature. The strong intermolecular interaction mainly contributed by the hydrogen-bonding and π-π interaction between PhDPP molecules promoted the formation of supramolecular polymeric structures in both solution and solid states and at interfaces. The supramolecular polymeric properties enabled solution-based processing of PhDPP under a variety of conditions into different structures including fibers and uniform thin films. The structure-property relationship that we established in the present system of PhDPP from the molecular to supramolecular level will be important to solution-process this type of H-bonding π-conjugated molecules for a variety of applications such as optoelectronic devices.

Photoconductive Micro/Nanoscale Interfaces of a Semiconducting Polymer for Wireless Stimulation of Neuron-Like Cells.

We report multiscale structured fibers and patterned films based on a semiconducting polymer, poly(3-hexylthiophene) (P3HT), as photoconductive biointerfaces to promote neuronal stimulation upon light irradiation. The micro/nanoscale structures of P3HT used for neuronal interfacing and stimulation include nanofibers with an average diameter of 100 nm, microfibers with an average diameter of about 1 µm, and lithographically patterned stripes with width of 3, 25, and 50 µm, respectively. The photoconductive effect of P3HT upon light irradiation provides electrical stimulation for neuronal differentiation and directed growth. Our results demonstrate that neurons on P3HT nanofibers showed a significantly higher total number of branches, while neurons grown on P3HT microfibers had longer and thinner neurites. Such a combination strategy of topographical and photoconductive stimulation can be applied to further enhance neuronal differentiation and directed growth. These photoconductive polymeric micro/nanostructures demonstrated their great potential for neural engineering and development of novel neural regenerative devices.

Theranostic Colloidal Nanoparticles of Pyrrolopyrrole Cyanine Derivatives for Simultaneous Near-Infrared Fluorescence Cancer Imaging and Photothermal Therapy.

Theranostic agents incorporating diagnostic and therapeutic agents together play crucial roles in clinical cancer treatment. On the one hand, near-infrared (NIR) fluorescence imaging strategies are expected to provide high-resolution real-time structural and molecular information with deep penetration to biological tissues in vivo. On the other hand, photothermal therapy (PTT) offers a highly efficient treatment to cancer with negligible safety concerns. To combine the strengths of both NIR fluorescence imaging and PTT for simultaneous cancer imaging and therapy, we report a type of NIR fluorescent nanoparticles (NPs) composed of pyrrolopyrrole cyanines (PPCys) with a strong absorbance in the NIR optical window. These NPs as effective theranostic agents show strong NIR fluorescence and photothermal effect for simultaneous cancer imaging and therapy at both in vitro and in vivo levels. The in vivo imaging and therapy results in nude mice demonstrate the promising potential of these NIR NPs for preclinical and clinical cancer imaging and therapy applications.