Strong NIR Absorption Research Articles

Dianionic States of Trithiadodecaazahexaphyrin Complexes with Homotrinuclear MII3O Clusters (M = Ni and Cu): Crystal Structures, Metal- Or Macrocycle-Centered Reduction, and Doublet-Quartet Transitions in the Dianions.

Metal complexes of trithiadodecaazahexaphyrin (Hhp) that contain MII3O clusters inside a π-extended trianionic (Hhp3-) macrocycle have been prepared. Studies of the magnetic properties of NiII3O(Hhp) and CuII3O(Hhp) reveal a diamagnetic and EPR-silent trianionic (Hhp3-) macrocycle and diamagnetic NiII3(O2-) or paramagnetic CuII3(O2-) tetracations. The positive charge of MII3O(Hhp) is compensated by one acetate anion {MII3O(Hhp)}+(CH3CO2-). The three-electron reduction of {MII3O(Hhp)}+ yields {cryptand(Cs+)}2{NiII2NiIO(Hhp5-)}2-·2C7H8 (1) and {cryptand(Cs+)}2{CuII3O(Hhp•6-)}2-·C7H8 (2) crystalline salts. The magnetic properties of 1 reveal the formation of Hhp5- and the reduction of nickel(II) to the paramagnetic NiI ion (S = 1/2), which is accompanied by the formation of the {NiII2NiIO(Hhp5-)}2- dianion. As a result, the magnetic moment of 1 is 1.68 μB in the 20-220 K range, and a broad EPR signal of NiI was observed. The Hhp5- macrocycle has a singlet ground state, but the increase in the magnitude of the magnetic moment of 1 above 220 K is attributed to the population of the triplet excited state in Hhp5-. The {NiII2NiIO(Hhp5-)}2- dianion is transferred from the doublet excited state to the quartet excited state with an energy gap of 1420 ± 50 K. Salt 1 also shows an unusually strong low-energy NIR absorption, which was observed at 1000-2200 nm. In 2, a highly reduced Hhp•6- radical hexaanion (S = 1/2) coexists with a CuII3(O2-) cluster (S = 1/2) in the {CuII3O(Hhp•6-)}2- dianions. The dianions have a triplet ground state with antiferromagnetic exchange between two S = 1/2 spins with J = -6.4 cm-1. The reduction of Hhp in both salts equalizes the initially alternated C-N bonds, supporting the increase in the Hhp macrocycle electron delocalization.

Hollow mesoporous polyaniline nanoparticles with high drug payload and robust photothermal capability for cancer combination therapy

In recent years, synergistic chemo-photothermal therapy has revealed promising potential in treatments against various kinds of cancer. However, the development of superb photothermal agents with high drug loading capacity is still highly required. In this work, a hollow mesoporous polyaniline nanoparticle (HPANI NP) has been developed for encapsulating chemotherapeutic drug doxorubicin (DOX) with an remarkable drug loading content as high as 37.5%. Additional PEG modification endowed the drug-loaded HPANI NPs with improved water-dispersibility and bioavailability. Such PEG-HPANI-DOX NPs exhibited strong NIR absorbance and robust photothermal conversion capacity, exhibiting highly efficient synergistic cancer treatment. More interestingly, the responsively released DOX molecules could emit strong red fluorescence, which could be employed to monitor the cellular endocytosis and drug release profile of PEG-HPANI-DOX NPs. Finally, the as-fabricated NPs showed good biocompatibility and low toxicity, serving as a promising nanoagent for highly efficient drug delivery and cancer combination therapy.

Highly Efficient Water-Soluble Photosensitizer Based on Chlorin: Synthesis, Characterization, and Evaluation for Photodynamic Therapy.

The clinical applications of many photosensitizers (PSs) are limited because of their poor water solubility, weak tissue penetration, low chemical purity, and severe toxicity in the absence of light. We designed a novel chlorin-based PS (designated as HPS) to achieve fluorescence image-guided photodynamic therapy (PDT) with efficient ROS generation. In addition to its simple fabrication process, HPS has other advantages such as excellent water solubility, strong NIR absorption, and high biocompatibility upon chemical functionalization for enhanced phototherapy. HPS exhibited high photodynamic performance against lung cancer and breast cancer cells by generating a large amount of singlet oxygen (1O2) under 654 nm laser irradiation. HPS accumulated into multiple organelles such as mitochondria and the endoplasmic reticulum and triggered cell apoptosis by laser exposure. In the tumor-bearing mice, in vivo, HPS showed an optimal half-life in circulation and achieved fluorescence-image-guided PDT within the irradiation window, resulting in effective tumor growth inhibition and the prolonged survival of animals. Moreover, the antitumor PDT effect of HPS was close to the clinical trial phase II stage of HPPH even at the low dosage of 0.32 mg/kg (under 75 J/cm2 laser), while the systemic safety of HPS was much higher. In conclusion, HPS is a novel water-soluble chlorin derivative with excellent PDT potential for clinical transformation.

An ultra-stable bio-inspired bacteriochlorin analogue for hypoxia-tolerant photodynamic therapy.

Photodynamic therapy (PDT) greatly suffers from the weak NIR-absorption, oxygen dependence and poor stability of photosensitizers (PSs). Herein, inspired by natural bacteriochlorin, we develop a bacteriochlorin analogue, tetrafluorophenyl bacteriochlorin (FBC), by one-step reduction of tetrafluorophenyl porphyrin (TFPP). FBC can realize deep tissue penetration, benefitting from the strong NIR absorption. The reactive oxygen species (ROS) generation capacity of FBC can retain around 60% with a 1.0 cm-thick pork skin as the barrier. Besides, FBC could not only produce oxygen-dependent 1O2, but also generate less oxygen-dependent O2−˙ and ˙OH to achieve excellent PDT even in hypoxic tumors. Moreover, FBC exhibits an ultra-high stability and it is almost unchanged even under visible light at room temperature for 15 months. Interestingly, the high reactivity of the fluorophenyl group makes it easy for FBC to produce FBC derivatives. A biocompatible FBC nanogel could be directly formed by blending FBC with SH–PEG–SH. The FBC nanogel displays excellent photodynamic efficacy in vitro and in vivo. Thus, FBC would be a promising PS for the clinical PDT of deep tumors.

Developing strong NIR absorption materials through linear planar π-conjugated cyclopalladated complex dimers.

Near-infrared absorption metal complexes (NIRMCs) have been traditionally associated with the π-expanded macrocycle structure. However, macrocyclic ligands suitable for NIRMCs require a laborious synthetic route, and are a limited few. Herein, we report a kind of NIRMC based on linear large planar π-conjugated cyclopalladated dimers, which can be obtained by a facile base-induced dimerization of corresponding monomers. These dimers show an intense absorption in the NIR region with ε770 nm = 2.5 × 105 cm-1 M-1, and display a fluorescence emission peak at ca. 910 nm. Quinoid thiophene methine (QTM) and the cyclopalladated structure are speculated to be the key factors for their strong NIR absorption, which provides a different perspective of preparing NIR absorption metal complexes.

Bismuth Sulfide Nanorods as Efficient Photothermal Theragnosis Agents for Cancer Treatment

Bi2S3 nanostructures can theoretically have photothermal properties. However, there are few reports on the application of bismuth sulfide in photothermal therapy due to the poor photothermal effect. To address this problem, herein we obtained Bi2S3 nanorods with defect structures via a facile method. Due to the special shape and defects, the Bi2S3 nanorods exhibited a strong absorption band in the NIR region, thus showed excellent photothermal effect. The photothermal conversion efficiency of Bi2S3 nanorods was calculated to be as high as 78.1% due to the strong NIR absorption. Importantly, the photothermal ablation experiments both in vitro and in vivo proved that the Bi2S3 nanorods can effectively kill cancer cells under the irradiation of an 808 nm laser. In addition, Bi2S3 nanorods can be used as effective CT imaging agents due to inherently high X-ray attenuation coefficient of bismuth. Our work demonstrated that the Bi2S3 nanorods were very promising photothermal nanoplatforms for photothermal therapy of cancers, guided by CT imaging.

Synthesis and Characterization of Push‐Pull Aza‐BODIPY Dyes Towards Application in NIR‐II Photothermal Therapy

AbstractA new series of aza‐BODIPYs (CN−X) with significantly red‐shifted absorbances were designed and synthesized by installation of various electron‐donating groups on the para‐positions of 3,5‐phenyl groups while strong electron‐withdrawing groups (nitrile groups) were fixed on the para‐positions of 1,7‐phenyl moieties. Interestingly, strong electron‐donating groups such as N'N‐dimethylaniline (CN−NMe2) could provide strong NIR absorption up to 857 nm and weak fluorescence emission up to 967 nm, whereas strong evidence supported heat production via non‐radiative decay after excitation. Electrochemical studies revealed that the substituents on the dyes showed strong effects on the oxidation potentials where the oxidation wave of CN−NMe2 occurred at the lowest overpotential, followed by CN−OMe, CN−Me, CN−Br and CN−H, respectively. Calculations were also performed to understand the push‐pull effect of the substituents on the aza‐BODIPY systems. Finally, applications of dyes in NIR cancer cell imaging and the NIR‐II photothermal effect were also investigated.

BiVO4@Bi2S3 Heterojunction Nanorods with Enhanced Charge Separation Efficiency for Multimodal Imaging and Synergy Therapy of Tumor.

Despite malignant tumors being one of the most serious diseases threatening human health and living quality, exploring theranostic agents for highly effective tumor diagnosis and treatment is still full of challenges. Herein, we demonstrate the design and preparation of Tween-20-modified BiVO4@Bi2S3 heterojunction nanorods (HNRs) for multimodal computed tomography (CT)/photoacoustic (PA) imaging and radiotherapy (RT)/radiodynamic therapy (RDT)/photothermal therapy (PTT) synergistic therapy. Benefiting from the high X-ray attenuation coefficient of Bi, BiVO4@Bi2S3 HNRs exhibit a sensitive CT imaging capacity and radiation enhancement effect during RT. Meanwhile, the strong NIR absorption of Bi2S3 endows BiVO4@Bi2S3 HNRs with an excellent PA imaging and photothermal transformation capacity. More importantly, by taking advantage of the type II band alignment between BiVO4 and Bi2S3, an extra internal electric field is established to accelerate the separation of X-ray-induced electrons and holes in BiVO4@Bi2S3 HNRs, resulting in the realization of highly effective X-ray-induced RDT. Because the in vitro and in vivo experiments have verified that the RT/RDT/PTT synergistic therapeutic efficacy is greatly superior to any single treatment, it is believed that our BiVO4@Bi2S3 HNRs can be used as the multifunctional nanotheranostic platform for malignant tumor theranostics.

Photoacoustic Imaging Probes Based on Tetrapyrroles and Related Compounds.

Photoacoustic imaging (PAI) is a rapidly evolving field in molecular imaging that enables imaging in the depths of ultrasound and with the sensitivity of optical modalities. PAI bases on the photoexcitation of a chromophore, which converts the absorbed light into thermal energy, causing an acoustic pressure wave that can be captured with ultrasound transducers, in generating an image. For in vivo imaging, chromophores strongly absorbing in the near-infrared range (NIR; > 680 nm) are required. As tetrapyrroles have a long history in biomedical applications, novel tetrapyrroles and inspired mimics have been pursued as potentially suitable contrast agents for PAI. The goal of this review is to summarize the current state of the art in PAI applications using tetrapyrroles and related macrocycles inspired by it, highlighting those compounds exhibiting strong NIR-absorption. Furthermore, we discuss the current developments of other absorbers for in vivo photoacoustic (PA) applications.

Doxorubicin-Loaded Bi-PEG Nanoparticles as Novel Chemo-Photothermal Nanoagents for Efficiently Killing Cancer Cells.

The chemo-photothermal therapy has been proved to be one of efficient strategies for destroying cancer cells, and the prerequisite is to develop photothermal nanoagents with drug-loading capacity. However, most of the current chemo-photothermal nanoagents have multiple structures which require complex synthetic process, undoubtedly hindering their bioapplication. Herein, we prepared PEGylated Bi nanoparticles and loaded with the model drug doxorubicin (DOX), forming DOX@Bi-PEG nanoparticles. Bi-PEG nanoparticles were firstly synthesized through a rapid reduction method and then coated with PEGylated phospholipids, exhibiting strong NIR absorption, high photothermal conversion efficiency of 49.4%, DOX-loading efficiency of 22.8% as well as low cytotoxicity. After incubation with 4T1 cells, DOX@Bi-PEG nanoparticles can be uptaken by cells and then release DOX within cells for chemotherapy. Furthermore, when exposed to 1064 nm laser, these nanoparticles can produce enough heat for photothermal ablating cancer cells. Therefore, the present DOX@Bi-PEG nanoparticles can be served as novel and efficient nanoagents for chemophotothermal therapy of cancer cells.

Cleavage of the C-H Bond in Bu3MeP+ by Zinc Porphyrin Dianions: Formation of {ZnII(CH2PBu3)(TPyPH)}- Containing Zn-C(ylide) Bond and the (TPyPH)3- Macrocycle Showing Strong NIR Absorption.

Reduction of {ZnII(TPyP)} to the {ZnII(TPyP)}2- dianions (TPyP: tetra(4-pyridyl)porphyrin) in the presence of Bu3MeP+ allows one to observe the C-H bond cleavage in the methyl group of Bu3MeP+ to form (Bu3MeP+){ZnII(CH2PBu3)(TPyPH)}-·0.337C6H5CH3 (1). Salt 1 is the first coordination complex of neutral CH2PBu3 ylide and metalloporphyrin. The released hydrogen atom attacks the meso-carbon atom of TPyP4- forming a TPyPH3- macrocycle related to phlorins. Decreased symmetry of the TPyPH3- allows the observation of a strong NIR absorption. We discuss the molecular structure, optical, and magnetic properties of 1 together with its formation pathways.

Deprotection of a benzyl unit induces a 22π aromatic macrocycle of 3-oxypyripentaphyrin(0.1.1.1.0) with strong NIR absorption.

We report aromaticity switching from a 6π pyridine ring to a 22π macrocyclic ring of 3-oxypyripentaphyrin(0.1.1.1.0). This system has potential applications in photodynamic therapy owing to macrocyclic aromaticity being selectively induced by protecting group removal and strong absorption bands produced in the NIR region especially in methanol.

Electrochemical deposition of a semiconducting gold dithiolene complex with NIR absorption.

Here, the synthesis of a new anionic gold dithiolene complex, NBu4·[1-i], and that of its corresponding neutral gold complex 2 is reported. Complex 2 shows strong absorption into the IR, semiconductivity (σRT = 3.06 × 10-7 S cm-1) with an activation energy of 0.25 eV, and weakly temperature dependent paramagnetic susceptibility, indicating strong intermolecular interactions in the solid state. As a consequence of their strong intermolecular interactions, neutral gold dithiolene complexes are often highly insoluble, limiting their utility and processability. Electrochemical deposition is used to deposit conductive films of complex 2, which retain the NIR properties present in the bulk material, indicting that the strong intermolecular interactions are retained in the film.

Synthesis and Semiconducting Characteristics of the BF2 Complexes of Bisbenzothiophene-Fused Azadipyrromethenes.

A novel type of dibenzothiophene [b]-fused core-expanded azaBODIPYs were obtained through an efficient post-functionalization of tetrabrominated azadipyrromethenes, using CuI-catalyzed cyclization, followed by BF2 complexation. These dyes show nearly planar skeletons, strong NIR absorption with maximum peaks up to 733 nm, and remarkable low-lying LUMO level of -4.15 eV. The field-effect transistor based on 1b exhibits bipolar transport properties, with the highest electron and hole mobilities up to 0.012 and 0.046 cm2 V-1 s-1, respectively.

FeS2@C-ICG-PEG nanostructure with intracellular O2 generation for enhanced photo-dynamic/thermal therapy and imaging

Here, photodynamic therapy (PDT), photothermal therapy (PTT) and multimode imaging have been integrated in to one-nanoplatform. The FeS2@C-PEG yolk-shell nanostructures (200 nm) have been synthesized, which possesses strong NIR absorption and high photothermal conversion (42.3%), ascribing to the narrow band gap and the novel hollow structure. Moreover, FeS2@C-PEG also reveals the NIR-triggered ROS (OH and O2–) generation, and the mechanism was investigated in detail, showing that the photo-excited electrons and dissolved O2 determine the ROS generation. Moreover, by evaluating the energy band of FeS2, the VB potential is enough to oxidize water to form O2 under NIR irradiation that relieves tumor hypoxia and enhances PDT. Besides, the Fenton reaction of Fe ion also makes FeS2 would degrade intracellular H2O2 to produce ·OH and O2 to assist PDT. To make the best of the hollow structure, photosensitizer ICG was loaded to further improve the PTT and PDT. Furthermore, FeS2@C-PEG possess high relaxivity (424.9 mM−1 s−1), making the potential contrast agent for MRI. And the synergistic effect of PTT and PDT further insures the enhanced anticancer efficacy.

Multifunctional A7R Peptide-Modified Hollow Mesoporous Silica@Ag₂S Nanotheranostics for Photoacoustic/Near-Infrared Fluorescence Imaging-Guided Tumor-Targeted Chemo-Photothermal Therapy.

The fabrication of theranostic nanoplatforms which combine diagnostic and therapeutic functions have become an emerging approach for personal nanomedicine. Herein, a multifunctional nanoplatform consisting of A7R peptide (ATWLPPR) conjugated hollow mesoporous silica nanoparticles decorated with Ag₂S nanodots (Ag₂S@HMSs-A7R) has been developed as an efficient theranostic agent for simultaneous photoacoustic (PA) imaging and near-infrared fluorescence imaging (NIRF)-guided targeted chemotherapy and photothermal therapy against human breast cancer MDA-MB-231 cells. The design of Ag₂S doped HMSs by in situ controlled growth of ultrasmall Ag₂S nanodots in the mesopores of HMSs. The synthesized multifunctional nanoplatform exhibits high doxorubicin (DOX) loading capability (451 mg/g) and can be precisely controlled by glutathione (GSH), acidic environment and external laser irradiation. Thanks to the strong tunable NIR absorbance of Ag₂S, the nanoplatform produce effective photoacoustic capacity and superb photothermal conversion under light irradiation, thereby exhibiting sufficient in vivo fluorescence and photoacoustic signals as well as desirable photothermal therapeutic performance. Importantly, A7R peptide can selectively bind the Neuropilin-1 (NRP-1) receptor which overexpressed by the MDA-MB-231 cells. The achieved Ag₂S@HMSs-A7R possess ideal imaging capability for both PA and NIRF imaging in vivo, and the anti-tumor effect of Ag₂S@HMSs(DOX)-A7R was studied in vitro and in vivo, showing remarkable synergistic chemo-photothermal effect (combination index, CI < 1). Over all, the strategy of utilizing triple-responsive nanocarriers presents a highly promising potential as an efficient method for cancer theranostics.

Anodic Mechanism of 1,1′‐Bis(diphenylphosphino)ferrocenedicarbonylnickel Determined by Low‐Temperature Spectroelectrochemistry

[Ni(CO)2(dppf)] [1] {dppf = 1,1′‐bis(diphenylphosphino)ferrocene} was made by reductive carbonylation of [NiCl2(dppf)] with [Fe(CO)5], similar to our recent report in Organometallics, 2019, 38, 586–592. Complex [1] showed two oxidation waves in the cyclic voltammogram. UV/Vis‐NIR spectroelectrochemistry (SEC) and IR SEC at –30 °C as well as computational support by means of DFT was used to assign the oxidation state of both metal atoms after oxidation. The monocation [1]+ showed a strong NIR absorption band which was described as an IVCT [NiI→FeII] and inverse IVCT (iIVCT) or hole transfer [FeII→NiI] based on time dependence DFT (TD‐DFT). The IR SEC spectrum of [1]+ showed multiple bands associated with two similar configurations, one which had the spin delocalized over both metal atoms and a second configuration where the spin is primarily Ni localized. The second oxidation to [1]2+ occurred at the Ni atom and resulted in release of a CO ligand followed by the formation of dimeric complex determined by low temperature IR SEC.

Peripheral π-Extention of Carbazole-Based Porphyrins

We have explored the synthesis and functionalization of carbazole-based porphyrins. For example, compound 1 exhibited strong NIR absorption at 1087 nm due to the expanded conjugation by four benzo-fusion moieties. Here, we tried intramolecular cyclization of ethynyl-substituted compounds to form ethylene-fused compounds 2. Furthermore, additional benzo-fusion to carbazole moiety using benzocarbazole furnished 3. Thus newly synthesized porphyrins showed further red-shifted and broadened NIR absorption. Figure 1

Resistive Switching: Organic Memristor Utilizing Copper Phthalocyanine Nanowires with Infrared Response and Cation Regulating Properties (Adv. Electron. Mater. 4/2019)

In article number 1800793, Zong-Xiang Xu, Ye Zhou, Su-Ting Han, and co-workers report a NIR-sensitive organic memristor based on solution-processed copper phthalocyanine nanowires. The uniform mesh structure of the device enables a well-manipulated Ag+ migration path, promotes the formation/rupture of robust conductive filament, and ultimately improves memory performance. Furthermore, the strong NIR absorption of the nanowires ensures photo-mediated resistive switching.

Photoacoustic Imaging of Nanoparticle Transport in the Kidneys at High Temporal Resolution.

Noninvasive monitoring of kidney elimination of engineered nanoparticles at high temporal and spatial resolution will not only significantly advance our fundamental understandings of nephrology on the nanoscale, but also aid in the early detection of kidney disease, which affects more than 10 % of the worldwide population. Taking advantage of strong NIR absorption of the well-defined Au25 (SG)18 nanocluster, photoacoustic (PA) imaging was used to visualize its transport in situ through the aorta to the renal parenchyma and its subsequent filtration into the renal pelvis at a temporal resolution down to 1 s. High temporal and spatial resolution imaging of Au25 (SG)18 kidney elimination allowed the accurate quantification of the glomerular filtration rate (GFR) of individual kidneys in normal and pathological conditions, broadening the biomedical applications of engineered nanoparticles in preclinical kidney research.