Gold Nanoframeworks with Mesopores for Raman–Photoacoustic Imaging and Photo‐Chemo Tumor Therapy in the Second Near‐Infrared Biowindow

Gold‐based nanostructures with tunable wavelength of localized surface plasmon resonance (LSPR) in the second near‐infrared (NIR‐II) biowindow receive increasing attention in phototheranostics. In view of limited progress on NIR‐II gold nanostructures, a particular liposome template‐guided route is explored to synthesize novel gold nanoframeworks (AuNFs) with large mesopores (≈40 nm) for multimodal imaging along with therapeutic robustness. The synthesized AuNFs exhibit strong absorbance in NIR‐II region, affording their capacity of NIR‐II photothermal therapy (PTT) and photoacoustic (PA) imaging for deep tumors. Functionalization of AuNFs with hyaluronic acid (HA) endows the targeting capacity for CD44‐overexpressed tumor cells while gatekeeping doxorubicin (DOX) loaded into mesopores. Conjugation of Raman reporter 4‐aminothiophenol (4‐ATP) onto AuNFs yields a surface‐enhanced Raman scattering (SERS) fingerprint for Raman spectroscopy/imaging. In vivo evaluation of HA‐4‐ATP‐AuNFs‐DOX on tumor‐bearing xenografts demonstrates its high efficacy in eradication of solid tumors in NIR‐II under PA–Raman dual image‐guided photo‐chemotherapy. Thus, current AuNFs offer versatile capabilities for phototheranostics.     

Near‐Infrared Plasmonic 2D Semimetals for Applications in Communication and Biology

Localized surface plasmon resonance (LSPR) has many applications which require meeting specific wavelength windows. The most prominent examples are photothermal therapy in biology, matched to the biological window (650–1350 nm), and communication relying on photodetection in optoelectronics, matched to the communication window (1260–1675 nm). However, for the classic noble metals (Au, Ag), tuning LSPRs from visible region to these two windows is still a demanding task due to their intrinsic limitations on charge density and dielectric function. Here, the discovery of near‐infrared biological and communication window‐matched plasmonic properties of semimetal TiS₂ nanosheets (NSs) is reported for the first time. Developed synthesis procedures allow fine‐tuning width and thickness of single‐crystal TiS₂ NSs. During characterization a new and intensive absorption peak in the 1000–1400 nm range is observed from both TiS₂ NS colloid solutions and films. This peak is attributed to LSPR due to its dependence on particle shape and on the refractive index of solvents. The superiority of such LSPRs is demonstrated in both, biological and optical applications: excitation at 808 and 980 nm generates a ≈50 °C photothermal temperature rise, while excitation at 1310 nm results in two‐times enhanced photocurrents of PbS photodetectors compared to untreated devices.     

Photoacoustic Imaging Guided Near‐Infrared Photothermal Therapy Using Highly Water‐Dispersible Single‐Walled Carbon Nanohorns as Theranostic Agents

The poly(maleic anhydride‐alt‐1‐octadecene‐poly(ethylene glycol)) (C₁₈PMH‐PEG) modified single‐walled carbon nanohorns (SWNHs) are designed with high stability and biocompatibility. The as‐prepared SWNHs/C₁₈PMH‐PEG not only can serve as an excellent photothermal agent but also can be used as a promising photoacoustic imaging (PAI) agent both in vitro and in vivo due to its strong absorption in the near infrared (NIR) region. The PAI result reveals that the SWNHs/C₁₈PMH‐PEG possesses ultra long blood circulation time and can significantly be accumulated at the tumor site through the enhanced penetration and retention (EPR) effect. The maximum accumulation of SWNHs/C₁₈PMH‐PEG at tumor site could be achieved at the time point of 24 h after intravenous injection, which is considered to be the optimal time for the 808 nm laser treatment. The subsequent photothermal ablation of tumors can be achieved without triggering any side effects. Therefore, a PAI guided PTT platform based on SWNHs is proposed and highlights the potential theranostic application for biomedical uses.     

One‐Step Preparation of Biocompatible Gold Nanoplates with Controlled Thickness and Adjustable Optical Properties for Plasmon‐Based Applications

The ability to synthesize plasmonic nanomaterials with well‐defined structures and tailorable size is crucial for exploring their potential applications. Gold nanoplates (AuNPLs) exhibit appealing structural and optical properties, yet their applications are limited by difficulties in thickness control. Other challenges include a narrow range of tunability in size and surface plasmon resonance, combined with a synthesis conventionally involving cytotoxic cetyltrimethylammonium (CTA) halide surfactant. Here, a one‐step, high‐yield synthesis of single‐crystalline AuNPLs is developed, based on the combined use of two structure‐directing agents, methyl orange and FeBr₃, which undergo preferential adsorption onto different crystalline facets of gold. The obtained AuNPLs feature high shape homogeneity that enables mesoscopic self‐assembly, broad‐range tunability of dimensions (controlled thickness from ≈7 to ≈20 nm, accompanied by modulation of the edge length from ≈150 nm to ≈2 µm) and plasmonic properties. These merits, coupled with a preparation free of CTA‐halide surfactants, have facilitated the exploration of various uses, especially in bio‐related areas. For example, they are demonstrated as biocompatible photothermal agents for cell ablation in NIR I and NIR II windows. This work paves the way to the innovative fabrication of anisotropic plasmonic nanomaterials with desired attributes for wide‐ranging practical applications.     

Ultrasmall Semiconducting Polymer Dots with Rapid Clearance for Second Near‐Infrared Photoacoustic Imaging and Photothermal Cancer Therapy

Phototheranostic agents in the second near‐infrared (NIR‐II) window (1000–1700 nm) are emerging as a promising theranostic platform for precision medicine due to enhanced penetration depth and minimized tissue exposure. The development of metabolizable NIR‐II nanoagents for imaging‐guided therapy are essential for noninvasive disease diagnosis and precise ablation of tumors. Herein, metabolizable highly absorbing NIR‐II conjugated polymer dots (Pdots) are reported for the first time for photoacoustic imaging guided photothermal therapy (PTT). The unique design of low‐bandgap D‐A π‐conjugated polymer (DPP‐BTzTD) together with modified nanoreprecipitation conditions allows to fabricate NIR‐II absorbing Pdots with ultrasmall (4 nm) particle size. Extensive experimental tests demonstrate that the constructed Pdots exhibit good biocompatibility, excellent photostability, bright photoacoustic signals, and high photothermal conversion efficiency (53%). In addition, upon tail‐vein intravenous injection of tumor‐bearing mice, Pdots also show high‐efficient tumor ablation capability with rapid excretion from the body. In particular, both in vitro and in vivo assays indicate that the Pdots possess remarkable PTT performance under irradiation with a 1064 nm laser with 0.5 W cm^?2, which is much lower than its maximum permissible exposure limit of 1 W cm^?2. This pilot study thus paves a novel avenue for the development of organic semiconducting nanoagents for future clinical translation.     

Size‐Controlled Synthesis of Cu2‐xE (E = S,Se) Nanocrystals with Strong Tunable Near‐Infrared Localized Surface Plasmon Resonance and High Conductivity in Thin Films

A facile method for preparing highly self‐doped Cu_2‐xE (E = S, Se) nanocrystals (NCs) with controlled size in the range of 2.8–13.5 nm and 7.2–16.5 nm, for Cu_2‐xS and Cu_2‐xSe, respectively, is demonstrated. Strong near‐infrared localized surface plasmon resonance absorption is observed in the NCs, indicating that the as‐prepared particles are heavily p‐doped. The NIR plasmonic absorption is tuned by varying the amount of oleic acid used in synthesis. This effect is attributed to a reduction in the number of free carriers through surface interaction of the deprotonated carboxyl functional group of oleic acid with the NCs. This approach provides a new pathway to control both the size and the cationic deficiency of Cu_2‐xSe and Cu_2‐xS NCs. The high electrical conductivity exhibited by these NPs in metal‐semiconductor‐metal thin film devices shows promise for applications in printable field‐effect transistors and microelectronic devices.     

Precise Modulation of Gold Nanorods for Protecting against Malignant Ventricular Arrhythmias via Near‐Infrared Neuromodulation

Hyperactivity of the left stellate ganglion (LSG) contributes to the occurrence of ventricular arrhythmias (VAs). Recently, advances in neuromodulation have been achieved with near‐infrared (NIR)‐sensitive gold nanorods (AuNRs). Here, AuNRs are precisely regulated and applied to inhibit LSG function as well as neural activity, thus ameliorating myocardial ischemia‐induced VAs in a canine model. Specifically, the optimized AuNRs are synthesized and microinjected into the LSG of anesthetized dogs, and then followed by 5 min of NIR laser irradiation at a wavelength of 808 nm. The results demonstrate that 5 min NIR laser irradiation on the PEG‐AuNR‐treated LSG can reversely inhibit LSG function and neural activity, thereby ameliorating myocardial ischemia‐induced VAs. With the tissue‐penetrating NIR and excellent photothermal effect of AuNRs, this method may become a promising and noninvasive therapeutic strategy for suppressing hyperactivity of the cardiac sympathetic nerves, therefore benefiting patients with VAs in the future.     

Supported Faceted Gold Nanoparticles with Tunable Surface Plasmon Resonance for NIR‐SERS

A novel dry plasma methodology for fabricating directly stabilized substrate‐supported gold nanoparticle (NP) ensembles for near infrared surface enhanced Raman scattering (NIR SERS) is presented. This maskless stepwise growth exploits Au‐sulfide seeds by plasma sulfidization of gold nuclei to produce highly faceted Au NPs with a multiple plasmon resonance that can be tuned from the visible to the near infrared, down to 1400 nm. The role of Au sulfidization in modifying the dynamics of Au NPs and of the corresponding plasmon resonance is discussed. The tunability of the plasmon resonance in a broad range is shown and the effectiveness as substrates for NIR SERS is demonstrated. The SERS response is investigated by using different laser sources operating both in the visible and in the NIR. SERS mapping of the SERS enhancement factor is carried out in order to evaluate their effectiveness, stability, and reproducibility as NIR SERS substrates, also in comparison with gold NPs fabricated by conventional sputtering and with the state‐of‐the‐art in the current literature.     

Specific Near‐IR Absorption Imaging of Glioblastomas Using Integrin‐Targeting Gold Nanorods

Molecular imaging using nanoprobes with high resolution and low toxicity is essential in early cancer detection. Here we introduce a new class of smart imaging probes employing PEGylated gold nanorods (GNRs) conjugated to cRGD for specific optical imaging of α_vβ₃ integrins from glioblastoma. GNRs exhibiting an optical resonance peak in the near‐infrared (NIR) region were synthesized using the seed‐mediated growth method. CTAB (cetyl trimethylammonium bromide) bilayer on the GNRs was replaced with a biocompatible stabilizer, heterobifunctional polyethyleneglycol (COOH‐PEG‐SH). Further, the carboxylated GNRs (PGNRs; PEG‐coated GNRs) were functionalized with cRGD using EDC‐NHS chemistry to formulate cRGD‐conjugated GNRs (cRGD‐PGNRs) for α_vβ₃ integrins. In order to assess the potential of the cRGD‐PGNRs as a targeted imaging probe, we investigated their optical properties, biocompatibility, colloidal stability and in vitro/in vivo binding affinities for cancer cells. Consequently, cRGD‐PGNRs demonstrated excellent tumor targeting ability with no cytotoxicity, as well as sufficient cellular uptake due to stable and prolonged blood circulation of cRGD‐PGNRs.     

Significantly Enhanced Photoluminescence of Doped Polymer‐Metal Hybrid Nanotubes

We report on the significantly enhanced photoluminescence (PL) of hybrid double‐layered nanotubes (HDLNTs) consisting of poly(3‐methylthiophene) (P3MT) nanotubes with various doping levels enveloped by an inorganic, nickel (Ni) metal nanotube. From laser confocal microscopy PL experiments on a single strand of the doped‐P3MT nanotubes and of their HDLNTs, the PL peak intensity of the HDLNT systems increased remarkably up to ～350 times as the doping level of the P3MT nanotubes of the HDLNTs increased, which was confirmed by measurements of the quantum yield. In a comparison of the normalized ultraviolet and visible absorption spectra of the doped‐P3MT nanotubes and their HDLNTs, new absorption peaks corresponding to surface‐plasmon (SP) energy were created at 563 and 615 nm after the nanoscale Ni metal coating onto the P3MT nanotubes, and their intensity increased on increasing the doping level of the P3MT nanotube. The doping‐induced bipolaron peaks of the HDLNTs of doped‐P3MT/Ni were relatively reduced, compared with those of the doped‐P3MT nanotubes before the Ni coating, due to the charge‐transfer effect in the SP‐resonance (SPR) coupling. Both energy‐transfer and charge‐transfer effects due to SP resonance contributed to the very‐large enhancement of the PL efficiency of the doped‐P3MT‐based HDLNTs.     

金纳米棒的制备及其在光声成像中的应用

该文制备了巯基聚乙二醇（PEG）修饰的金纳米棒,该纳米材料在近红外区具有良好的光吸收特性,具备作为优良光声造影剂的潜质。该文通过透射电子显微镜（TEM）、紫外 可见（UV VIS）吸收光谱等测量手段对金纳米棒进行了形貌、结构、基本光学性能及光声成像效果等表征。实验结果表明,随着材料浓度的增加,体外光声信号的响应近似呈线性增长;经由PEG修饰,金纳米棒的生物相容性得到提高;PEG修饰后的金纳米棒对小鼠大脑皮层血管的成像效果得到提升。结果表明,PEG修饰的金纳米棒材料,在光声成像造影领域具有巨大的应用前景。     

In‐Situ Vis–Near‐Infrared and Raman Spectroelectrochemistry of Double‐Walled Carbon Nanotubes

Double‐walled carbon nanotubes (DWCNTs) are studied using in‐situ visible–near‐infrared (vis‐NIR) and in‐situ Raman spectroelectrochemistry. Electrochemical vis‐NIR spectroscopy reveals a complex picture of DWCNTs due to the overlap of the features of the inner and outer tubes and possible optical transitions, which are not predicted by the simple tight‐binding model. The optical transitions are bleached upon electrochemical doping. This is qualitatively understood to be a consequence of the Fermi‐level shift by the applied potential relative to the van Hove singularity. In‐situ Raman spectra are quenched by the applied cathodic/anodic potentials due to the loss of resonance by electrochemical charging. The electrochemical tuning of Raman spectra proceeds distinctly for inner and outer tubes. While the bands of outer tubes rapidly follow the potential change, the features of inner tubes respond relatively slowly to electrochemical perturbations. The Raman D‐mode of DWCNTs was found to be bifurcated upon electrochemical charging, which is similar to the behavior of the tangential displacement mode. Ionic liquids are good electrolytes for the spectroelectrochemistry of DWCNTs, even at extreme applied potentials. They allow the deconvolution of the tangential modes of the inner and outer tubes at both cathodic and anodic doping.     

Near‐Field Enhanced Plasmonic‐Magnetic Bifunctional Nanotubes for Single Cell Bioanalysis

Near‐field enhanced bifunctional plasmonic‐magnetic (PM) nanostructures consisting of silica nanotubes with embedded solid nanomagnets and uniformly dual‐surface‐coated plasmonic Ag nanoparticles (NPs) are rationally synthesized. The solid embedded sections of nanotubes provide single‐molecule sensitivity with an enhancement factor up to 7.2 × 10⁹ for surface‐enhanced Raman scattering (SERS). More than 2× SERS enhancement is observed from the hollow section compared to the solid section of the same nanotube. The substantial SERS enhancement on the hollow section is attributed to the dual‐sided coating of Ag NPs as well as the near‐field optical coupling of Ag NPs across the nanotube walls. Experimentation and modeling are carried out to understand the dependence of SERS enhancement on the NP sizes, junctions, and the near field effects. By tuning the aspect ratio of the embedded nanomagnets, the magnetic anisotropy of nanotubes can be readily controlled to be parallel or vertical to the long directions for nano‐manipulation. Leveraging the bifunctionality, a nanotube is magnetically maneuvered to a single living mammalian cell amidst many and its membrane composition is analyzed via SERS spectroscopy.     

Self‐Assembled Robust Dipeptide Nanotubes and Fabrication of Dipeptide‐Capped Gold Nanoparticles on the Surface of these Nanotubes

Three water‐soluble dipeptides containing N‐terminally located β‐alanine residue and C‐terminally located α‐amino acid residues (β‐Ala‐L ‐Xaa, Xaa = Val/Ile/Phe) form robust crystalline nanotubes. These dipeptide nanotubes contain a common motif, a hybrid of β,α‐amino acids, which are stable against heat up to 80 °C, a wide range of pH (2–10), and proteolytic degradation. These robust crystalline dipeptide nanotubes are used as a template for fabricating dipeptide‐capped gold nanoparticles on their outer surfaces. This is an easy way to develop nanotube/nanoparticle hybrid materials under mild conditions.     

A Near‐Infrared Light‐Triggered Nanocarrier with Reversible DNA Valves for Intracellular Controlled Release

A near‐infrared (NIR) light‐triggered nanocarrier is developed for intracellular controlled release with good stability, high nuclease resistance, and good biocompatibility. The nanocarrier consists of a gold nanorod core and mesoporous silica shell, capped with reversible single‐stranded DNA valves, which are manipulated by switching between the laser on/off states. Upon laser irradiation, the valves of the nanocarrier open and the cargo molecules can be released from the mesopores. When the NIR laser is turned off, the valves close and the nanocarrier stops releasing the cargo molecules. The release amount of the cargo molecules can be controlled precisely by adjusting the irradiation time and the laser on‐off cycles. Confocal fluorescence imaging shows that the nanocarrier can be triggered by the laser irradiation and the controlled release can be accomplished in living cells. Moreover, the therapeutic effect toward cancer cells can also be regulated when the chemotherapeutic drug doxorubicin is loaded into the nanocarrier. This novel approach provides an ideal platform for drug delivery by a NIR light‐activated mechanism with precise control of area, time, and especially dosage.     

SnTe@MnO2‐SP Nanosheet–Based Intelligent Nanoplatform for Second Near‐Infrared Light–Mediated Cancer Theranostics

Near infrared light, especially the second near‐infrared light (NIR II) biowindows with deep penetration and high sensitivity are widely used for optical diagnosis and phototherapy. Here, a novel kind of 2D SnTe@MnO₂‐SP nanosheet (NS)‐based nanoplatform is developed for cancer theranostics with NIR II‐mediated precise optical imaging and effective photothermal ablation of mouse xenografted tumors. The 2D SnTe@MnO₂‐SP NSs are fabricated via a facile method combining ball‐milling and liquid exfoliation for synthesis of SnTe NSs, and surface coating MnO₂ shell and soybean phospholipid (SP). The ultrathin SnTe@MnO₂‐SP NSs reveal notably high photothermal conversion efficiency (38.2% in NIR I and 43.9% in NIR II). The SnTe@MnO₂‐SP NSs inherently feature tumor microenvironment (TME)‐responsive biodegradability, and the main metabolite TeO₃^2? shows great antitumor effect, coupling synergetic chemotherapy for cancer. Moreover, the SnTe@MnO₂‐SP NSs also exhibit great potential for fluorescence, photoacoustic (PA), and photothermal imaging agents in the NIR II biowindow with much higher resolution and sensitivity. This is the first report, as far as is known, with such an inorganic nanoagent setting fluorescence/PA/photothermal imaging and photothermal therapy in NIR II biowindow and TME‐responsive biodegradability rolled into one, which provide insight into the clinical potential for cancer theranostics.     

Shape‐ and Orientation‐Controlled Gold Nanoparticles Formed within Mesoporous Silica Nanofibers

Mesoporous silica nanofibers with longitudinal pore channels are synthesized in high yields using cetyltrimethylammonium bromide as the structure‐directing agent in hydrobromic acid solutions. These nanofibers are used as templates to prepare gold nanoparticles along the fiber axis. For the gold‐precursor‐loaded nanofibers that are not completely dried, nearly spherical gold nanoparticles are produced by hydrogen reduction. As the reduction temperature is lowered, the size of the gold nanoparticles decreases and the number density greatly increases, resulting in surface plasmon coupling between neighboring gold nanoparticles. For the gold‐precursor‐loaded nanofibers that undergo an additional drying process, ellipsoidal gold nanoparticles are obtained, with their major axes oriented along the direction of the pore channels. The major axes of ellipsoidal gold nanoparticles can be controlled to be oriented either parallel or perpendicular to the fiber axis by use of nanofibers with either longitudinal or circular pore channels, respectively. These gold‐nanoparticle‐embedded nanofibers can be expected to find interesting applications in the area of photonics and optoelectronics.     

Hierarchical Nanohybrids of Gold Nanorods and PGMA‐Based Polycations for Multifunctional Theranostics

Organic/inorganic nanohybrids hold great importance in fabricating multifunctional theranostics to integrate therapeutic functions with real‐time imaging. Although Au nanorods (NRs) have been employed for theranostics, complicated design of materials limits their practical applications. In this work, new multifunctional theranostic agents are designed and synthesized employing Au NRs with desirable near‐infrared absorbance as the cores. A facile “grafting‐onto” approach is put forward to prepare the series of hierarchical nanohybrids (Au‐PGEA and Au‐PGED) of Au NRs and poly(glycidyl methacrylate)‐based polycations. The resultant nanohybrids can be utilized as gene carriers with high gene transfection performances. The structural effect of polycations on gene transfection is investigated in detail, and Au‐PGEA with abundant hydroxyl groups on the surface exhibits superior performance. Au‐PGEA nanohybrids are further validated to possess remarkable capability of combined photothermal therapy (PTT) and gene therapy (GT) for complementary tumor treatment. Moreover, significantly enhanced computed tomography (CT)/photoacoustic (PA) signals are detected both in vitro and in vivo, verifying the potential of Au‐PGEA for dual‐modal imaging with precise and accurate information. Therefore, these multifunctional nanohybrids fabricated from a simple and straightforward strategy are promising for in vivo dual‐modal CT/PA imaging guided GT/PTT therapy with high antitumor efficacy.     

Ultra‐Small Iron Oxide Doped Polypyrrole Nanoparticles for In Vivo Multimodal Imaging Guided Photothermal Therapy

Recently, near‐infrared (NIR) absorbing conjugated polymeric nanoparticles have received significant attention in photothermal therapy of cancer. Herein, polypyrrole (PPy), a NIR‐absorbing conjugate polymer, is used to coat ultra‐small iron oxide nanoparticles (IONPs), obtaining multifunctional IONP@PPy nanocomposite which is further modified by the biocompatible polyethylene glycol (PEG) through a layer‐by‐layer method to acquire high stability in physiological solutions. Utilizing the optical and magnetic properties of the yielded IONP@PPy‐PEG nanoparticles, in vivo magnetic resonance (MR) and photoacoustic imaging of tumor‐bearing mice are conducted, revealing strong tumor uptake of those nanoparticles after intravenous injection. In vivo photothermal therapy is then designed and carried out, achieving excellent tumor ablation therapeutic effect in mice experiments. These results promise the use of multifunctional NIR‐absorbing organic‐inorganic hybrid nanomaterials, such as IONP@PPy‐PEG presented here, for potential applications in cancer theranostics.