Molecular Engineering of Conjugated Polymers for Biocompatible Organic Nanoparticles with Highly Efficient Photoacoustic and Photothermal Performance in Cancer Theranostics

Abstract

Conjugated polymer nanoparticles (CP NPs) are emerging candidates of "all-in-one" theranostic nanoplatforms with dual photoacoustic imaging (PA) and photothermal therapy (PTT) functions. So far, very limited molecular design guidelines have been developed for achieving CPs with highly efficient PA and PTT performance. Herein, by designing CP1, CP2, and CP3 using different electron acceptors (A) and a planar electron donor (D), we demonstrate how the D-A strength affects their absorption, emission, extinction coefficient, and ultimately PA and PTT performance. The resultant CP NPs have strong PA signals with high photothermal conversion efficiencies and excellent biocompatibility in vitro and in vivo. The CP3 NPs show a high PA signal to background ratio of 47 in U87 tumor-bearing mice, which is superior to other reported PA/PTT theranostic agents. A very small IC value of 0.88 μg/mL (CP3 NPs) was obtained for U87 glioma cell ablation under laser irradiation (808 nm, 0.8 W/cm, 5 min). This study shows that CP NP based theranostic platforms are promising for future personalized nanomedicine.

Molecular Engineering of Photoacoustic Performance by Chalcogenide Variation in Conjugated Polymer Nanoparticles for Brain Vascular Imaging

“…These values are much higher than the reported inorganic nanomaterials and organic CPNs, such as Au nanorods (21%), Cu 9 S 5 NPs (25.7%), polypyrrole (40%), and poly(cyclopentadithiophene‐ alt ‐diketopyrrolopyrrole) CPNs (20%) . The high value of photothermal conversion efficiency of CPNs should be attributed to the strong D–A pair in their conjugated backbones, which favors electron transfer to enhance nonradiative heat generation . As the three NPs reported here have similar photothermal conversion efficiencies, the outperforming photothermal property of PDTPBD NPs should be attributed to its higher absorption coefficient.…”

Polymer Dots as Effective Phototheranostic Agents

“…(b) Temperature monitoring of CP‐NPs under NIR laser illumination (left) and PA images of CP‐NPs and indocyanine green (ICG) (right). Reproduced with permission from ref . Copyright 2017 American Chemical Society.…”

Bright Aggregation‐Induced‐Emission Dots for Targeted Synergetic NIR‐II Fluorescence and NIR‐I Photoacoustic Imaging of Orthotopic Brain Tumors

“…The formulated TB1 dots show a very high fluorescence QY of 6.2% with a large absorptivity of 10.2 L g −1 cm −1 at 740 nm and emission maximum at 975 nm. Interestingly, the large NIR absorptivity also facilitates NIR‐I photoacoustic (PA) imaging, which intrinsically offers deeper penetration than even NIR‐II fluorescence imaging, owing to the much lower acoustic scattering than optical scattering in biological tissues . More importantly, PA imaging as a complementary adjuvant can delineate deep brain‐tumor margin with clear location depth information, which is difficult to realize by common NIR‐II fluorescence imaging.…”

“…D–A engineering is an effective method to reduce bandgap and shift the absorption maxima . Benzobisthiadiazole ( BBT ) is a strong electron‐deficient acceptor to constitute small molecules and conjugated polymers with NIR absorption and NIR‐II emission .…”

“…Once the rotary AIEgen of N,N ‐diphenyl‐4‐(1,2,2‐triphenylvinyl)aniline ( DPTPEA ) molecules with long conjugation length and high electron‐donating properties are attached to BBT acceptor, the yielded TB1 shows large extinction coefficient and NIR‐II emission, owing to the strong D–A strength and extended electronic conjugation . Furthermore, the strong absorption would benefit the high signal/background ratio (S/B) in both fluorescence and PA imaging in vivo . The synthetic route toward TB1 is illustrated in Scheme S1 (Supporting Information).…”