Zhongxi Xie

A Hollow-Structured CuS@Cu2S@Au Nanohybrid: Synergistically Enhanced Photothermal Efficiency and Photoswitchable Targeting Effect for Cancer Theranostics

It is of great importance in drug delivery to fabricate multifunctional nanocarriers with intelligent targeting properties, for cancer diagnosis and therapy. Herein, hollow-structured CuS@Cu2 S@Au nanoshell/satellite nanoparticles are designed and synthesized for enhanced photothermal therapy and photoswitchable targeting theranostics. The remarkably improved photothermal conversion efficiency of CuS@Cu2 S@Au under 808 nm near-infrared (NIR) laser irradiation can be explained by the reduced bandgap and more circuit paths for electron transitions for CuS and Cu2 S modified with Au nanoparticles, as calculated by the Vienna ab initio simulation package, based on density functional theory. By modification of thermal-isomerization RGD targeting molecules and thermally sensitive copolymer on the surface of nanoparticles, the transition of the shielded/unshielded mode of RGD (Arg-Gly-Asp) targeting molecules and shrinking of the thermally sensitive polymer by NIR photoactivation can realize a photoswitchable targeting effect. After loading an anticancer drug doxorubicin in the cavity of CuS@Cu2 S@Au, the antitumor therapy efficacy is greatly enhanced by combining chemo- and photothermal therapy. The reported nanohybrid can also act as a photoacoustic imaging agent and an NIR thermal imaging agent for real-time imaging, which provides a versatile platform for multifunctional theranostics and stimuli-responsive targeted cancer therapy.

Thiol–Ene Click Reaction as a Facile and General Approach for Surface Functionalization of Colloidal Nanocrystals

Oleic acid (OA) and/or oleylamine (OAm) are generally used as the surface ligands for stabilization of inorganic nanocrystals (NCs). The hydrophobic and inert surface of the NCs limits their applications such as in biomedical areas. Hence, surface modifications are essential in many physical and chemical processes. Here, a facile and versatile strategy is reported for the modification of NCs by ultraviolet-induced thiol-ene chemistry, in which thiol-terminated poly(ethylene glycol) (HSPEG) and its derivatives can react directly with double bonds in OA/OAm ligands to form covalent linking within one step. Through this strategy, various hydrophobic NCs with different compositions and morphologies are able to be transferred into water combining with functionalization of active groups. As a proof-of-concept, this strategy is successfully used to construct a sensor for detecting avidin based on upconverting luminescence analysis. Therefore, this strategy provides a new tool for designing and tuning the surface properties of NCs for different applications.

Multifunctional chitosan modified Gd2O3:Yb3+,Er3+@nSiO2@mSiO2 core/shell nanoparticles for pH responsive drug delivery and bioimaging

Gd2O3:Yb3+,Er3+@nSiO2@mSiO2 (Gd@mSi) core/shell structure nanospheres were synthesized through a sol–gel method. Then biocompatible polysaccharide chitosan (CS) was grafted onto the surface of the nanoparticles to fabricate a pH responsive CS@Gd@mSi system. Furthermore, cancer targeting ligand folic acid (FA) was modified through the abundant amino groups on the chitosan polymer shell. The nanospheres with a Gd2O3:Yb3+,Er3+ core can be candidates for T1-weighted magnetic resonance imaging (MRI) contrast agents. The CS decorated nanocomposites showing good biocompatibility and red emission under 980 nm laser excitation can be potential candidates for bioimaging in vitro. FA modified nanospheres loaded with doxorubicin hydrochloride (DOX) show higher cytotoxicity for HeLa cells in vitro compared with those nanoparticles with chitosan shells only and pure DOX. The CS@Gd@mSi system can be a potential drug carrier with MRI, UCL, and finely controlled pH-dependent drug release properties.

Construction of Hierarchical Polymer Brushes on Upconversion Nanoparticles via NIR-Light-Initiated RAFT Polymerization

Photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization generally adopts high-energy ultraviolet (UV) or blue light. In combination with photoredox catalyst, the excitation light wavelength was extended to the visible and even near-infrared (NIR) region for photoinduced electron transfer RAFT polymerization. In this report, we introduce for the first time a surface NIR-light-initiated RAFT polymerization on upconversion nanoparticles (UCNPs) without adding any photocatalyst and construct a functional inorganic core/polymer shell nanohybrid for application in cancer theranostics. The multilayer core-shell UCNPs (NaYF4:Yb/Tm@NaYbF4:Gd@NaNdF4:Yb@NaYF4), with surface anchorings of chain transfer agents, can serve as efficient NIR-to-UV light transducers for initiating the RAFT polymerization. A hierarchical double block copolymer brush, consisting of poly(acrylic acid) (PAA) and poly(oligo(ethylene oxide)methacrylate-co-2-(2-methoxy-ethoxy)ethyl methacrylate) (PEG for short), was grafted from the surface in sequence. The targeting arginine-glycine-aspartic (RGD) peptide was modified at the end of the copolymer through the trithiolcarbonate end group. After loading of doxorubicin, the UCNPs@PAA-b-PEG-RGD exhibited an enhanced U87MG cancer cell uptake efficiency and cytotoxicity. Besides, the unique upconversion luminescence of the nanohybrids was used for the autofluoresence-free cell imaging and labeling. Therefore, our strategy verified that UCNPs could efficiently activate RAFT polymerization by NIR photoirradiation and construct the complex nanohybrids, exhibiting prospective biomedical applications due to the low phototoxicity and deep penetration of NIR light.

Synthesis and photovoltaic properties of new donor–acceptor (D–A) copolymers based on benzo[1,2-b:3,4-b′:6,5-b′′] trithiophene donor and different acceptor units (P1 and P2)

Two new conjugated D–A copolymers P1 (PBTT-TQ) and P2 (PBTT-TPz) based on the same benzo[1,2-b:3,4-b′:6,5-b′′] trithiophene (BTT) donor and different acceptor monomers 4,9-bis(5-bromithiophen-2-yl)-6,7-bis(2-ethylhexyl)[1,2,5] thiadiazolo[3,4-g] quinoxaline (TQ) and 5,7-bis(5-bromothiophen-2-yl)-2,3-bis(5-octylthiophen-2-yl) thieno[3,4-b] pyrazine (TPy), respectively, were synthesized by Stille cross-coupling reaction and characterized by gel permeation chromatography (GPC), 1H NMR, UV-Vis absorption, thermal analysis and electrochemical cyclic voltammetry (CV) tests. The optical bandgaps of P1 and P2 measured from the onset of optical absorption of these copolymers in thin films were 1.14 eV and 1.38 eV, respectively. Photovoltaic properties of the bulk heterojunction (BHJ) devices were studied using P1 and P2 as the donor and PC61BM or PC71BM as the acceptor with weight ratios of polymer : PC61BM of 1 : 1, 1 : 2 and 1 : 3. The optimized photovoltaic devices fabricated with active blend layers of P1:PC71BM (1 : 2) and P2:PC71BM (1 : 2) cast from o-diclorobenzene (o-DCB) showed PCEs of 2.05% and 3.14%, respectively, whereas P2:PC61BM and P2:PC71BM yielded PCEs of 1.44% and 2.11%, respectively. The PCEs of BHJ solar cells based on P1:PC71BM and P2:PC71BM processed from 1-chloronapthanene (CN)/o-DCB solvent were further improved up to 5.28% and 2.6%, respectively.