Defective Porous Carbon Polyhedra Decorated with Copper Nanoparticles for Enhanced NIR-Driven Photothermal Cancer Therapy.

Currently, there is tremendous interest in the discovery of new and improved photothermal agents for near-infrared (NIR)-driven cancer therapy. Herein, a series of novel photothermal agents, comprising copper nanoparticles supported on defective porous carbon polyhedra are successfully prepared by heating a Cu-BTC metal-organic framework (MOF) precursor at different temperatures (t) in the range 400-900 °C under an argon atmosphere. The copper nanoparticle size and carbon defect concentration in the obtained products (denoted herein as Cu@CPP-t) increase with synthesis temperature, thus imparting the Cu@CPP-t samples with distinct NIR absorption properties and photothermal heating responses. The Cu@CPP-800 sample shows a remarkable photothermal conversion efficiency of 48.5% under 808 nm laser irradiation, representing one of the highest photothermal efficiencies yet reported for a carbon-based photothermal agent. In vivo experiments conducted with tumor bearing nude Balb/c mice confirm the efficacy of Cu@CPP-800 as a very promising NIR-driven phototherapy agent for cancer treatment. Results encourage the wider use of MOFs as low cost precursors for the synthesis of carbon-supported metal nanoparticle composites for photothermal therapy.

Exploiting Single Atom Iron Centers in a Porphyrin-like MOF for Efficient Cancer Phototherapy.

In recent years, single-atom catalysts (SACs) have attracted enormous attention due their effectiveness in promoting a variety of catalytic reactions. However, the ability of SACs to enhance cancer phototherapies has received little attention to date. Herein, we synthesized a metal organic framework (MOF) rich in porphyrin-like single atom Fe(III) centers (denoted herein as porphyrin-MOF or P-MOF) and then evaluated the performance of the P-MOF for cancer treatment by photodynamic therapy (PDT) and photothermal therapy (PTT) under NIR (808 nm) irradiation, as well as photoacoustic imaging (PAI) of tumors. On acccount of the abundance of single atom Fe(III) centers, the P-MOF material demonstrated excellent performance for modulation of the hypoxic tumor microenvironment of Hela cell tumors in mice, while also demonstrating good properties as a photoacoustic imaging (PAI) agent. Density functional theory (DFT) calculations were used to elucidate the superior performance of P-MOF in these applications relative to Fe2O3 (a Fe(III) reference compound). The calculations revealed that the narrow band gap energy of P-MOF (1.31 eV) enabled strong absorption of NIR photons, thereby inducing nonradiative transitions that converted incident light into heat to promote PTT. Further, a facile change of the spin state of the single atom Fe(III) centers in P-MOF under NIR irradiation transformed coordinated triplet oxygen (3O2) to singlet oxygen (1O2), benefiting PDT. This work demonstrates the great future potential of both SACs and MOFs as multifunctional agents for cancer treatment and tumor imaging.

Highly Efficient Vacancy-Driven Photothermal Therapy Mediated by Ultrathin MnO2 Nanosheets.

In medical applications, two-dimensional nanomaterials have been widely studied on account of their intriguing properties such as good biocompatibility, stability, and multifunctionality. Herein, an ultrathin MnO2 nanosheet has been fabricated by a simplistic hydrothermal process. The high photothermal conversion performance (62.4%) can be attributed to the vacancy in the ultrathin MnO2 nanosheet, as confirmed by the extended X-ray absorption fine structure results and the density functional theory calculation, benefiting photoacoustic imaging-guided cancer therapy. This highly efficient vacancy-induced photothermal therapy has been reported for the first time. As a result, this work demonstrates that this ultrathin MnO2 nanosheet has a potential to construct a nanosystem for imaging-guided cancer therapy.

Hollow carbon nanospheres derived from biomass by-product okara for imaging-guided photothermal therapy of cancers.

Okara is a by-product of tofu manufacturing and is usually used as a feedstuff. Herein, we developed a methodology of using okara as a carbon source for the preparation of photothermal nano-materials. It's interesting to find that just after calcination, the carbonized okara forms sphere-shaped hollow particles (denoted as HCNS) with an average diameter of 200 nm. Owning to the existence of a cavity, the HCNS was found to exhibit not only a good photothermal conversion efficiency, but also an ideal photoacoustic imaging property, which makes it a promising agent for imaging-guided photothermal therapy (PTT). The high photothermal conversion efficiency can result from the high carbon content and its hollow morphology. The in vitro and in vivo results both demonstrated the biocompatibility and capacity of the plant source carbon spheres for NIR-triggered cancer treatment. Therefore, the current work suggests a new method to gain a safe and low-cost photothermal platform which could be further exploited in biomedical fields.

Confinement of carbon dots localizing to the ultrathin layered double hydroxides toward simultaneous triple-mode bioimaging and photothermal therapy.

It is a great challenge to develop multifunctional nanocarriers for cancer diagnosis and therapy. Herein, versatile CDs/ICG-uLDHs nanovehicles for triple-modal fluorescence/photoacoustic/two-photon bioimaging and effective photothermal therapy were prepared via a facile self-assembly of red emission carbon dots (CDs), indocyanine green (ICG) with the ultrathin layered double hydroxides (uLDHs). Due to the J-aggregates of ICG constructed in the self-assembly process, CDs/ICG-uLDHs was able to stabilize the photothermal agent ICG and enhanced its photothermal efficiency. Furthermore, the unique confinement effect of uLDHs has extended the fluorescence lifetime of CDs in favor of bioimaging. Considering the excellent in vitro and in vivo phototherapeutics and multimodal imaging effects, this work provides a promising platform for the construction of multifunctional theranostic nanocarrier system for the cancer treatment.

Excitation-Dependent Theranostic Nanosheet for Cancer Treatment.

In this work, a novel ruthenium complex loaded monolayer layered double hydroxide (LDH) (denoted as Ru(C-bpy)2 /mLDH) as supramolecular nanosensor is synthesized, which is greatly exclusive to the hypoxic tumor microenvironment. The Ru(C-bpy)2 /mLDH ultrathin sheet displays not only enhanced luminescence lifetime compared to the parent Ru(C-bpy)2 alone, but also improved oxygen responsibility under an excitation of 488 or 800 nm. Moreover, the Ru(C-bpy)2 /mLDH is possessed of two-photon fluorescence imaging ability under the 800 nm irradiation. In addition, the Ru(C-bpy)2 /mLDH can generate singlet oxygen with a high yield (φ∆ ) of 0.28 under the 520 nm irradiation, while the φ∆ of Ru(C-bpy)2 is 0.19. Therefore, the Ru(C-bpy)2 /mLDH can be applied as a supramolecular theranostic agent with light-switchable cancer imaging and photodynamic therapy properties.

An NIR-sensitive layered supramolecular nanovehicle for combined dual-modal imaging and synergistic therapy.

A supramolecular nanovehicle, denoted as ICG-DOX/Gd-LDH, was synthesized by the co-intercalation of indocyanine green (ICG) and doxorubicin hydrochloride (DOX) into a gallery of Gd3+-doped-layered double hydroxide (Gd-LDH) such that to achieve a chemo-photothermal synergistic therapeutic agent. The unique structure of Gd-LDH can not only stabilize the photothermal agent ICG to enhance the photothermal efficiency, but also hamper the recombination between electron and holes, leading to the generation of more reactive oxygen species (ROS) under irradiation in the NIR range. Together with the loading capacity of DOX, ICG-DOX/Gd-LDH exhibited excellent combinatorial effects on tumor growth inhibition in both in vitro studies on HeLa cell line and in vivo tests over tumor-bearing mouse models. Moreover, it showed ideal ability for long-term tracing of the carrier distribution via either MRI or fluorescence imaging. Thus, this study indicates that Gd-LDH is a promising platform for the construction of multifunctional formulations, especially theranostic nano-systems for cancer treatment.

Controlled Growth of Well-Defined Conjugated Polymers from the Surfaces of Multiwalled Carbon Nanotubes: Photoresponse Enhancement via Charge Separation.

The installation of heterojunctions on the surfaces of carbon nanotubes (CNTs) is an effective method for promoting the charge separation processes needed for CNT-based electronics and optoelectronics applications. Conjugated polymers are proven state-of-the-art candidates for modifying the surfaces of CNTs. However, all previous attempts to incorporate conjugated polymers to CNTs resulted in unordered interfaces. Herein we show that well-defined chains of regioregular poly(3-hexylthiophene) (P3HT) were successfully grown from the surfaces of multiwalled CNTs (MWNTs) using surface-initiated Kumada catalyst-transfer polycondensation. The polymerization was found to proceed in a controlled manner as chains of tunable lengths were prepared through variation of the initial monomer-to-initiator ratio. Moreover, it was determined that large-diameter MWNTs afforded highly ordered P3HT aggregates, which exhibited a markedly bathochromically shifted optical absorption due to a high grafting density induced planarization of the polymer chains. Using ultrafast spectroscopy, the heterojunctions formed between the MWNTs and P3HT were shown to effectively overcome the binding energy of excitons, leading to photoinduced electron transfer from P3HT to MWNTs. Finally, when used as prototype devices, the individual MWNT-g-P3HT core-shell structures exhibited excellent photoresponses under a low illumination density.