An Antibody-directed and Immune Response Modifier-augmented Photothermal Therapy Strategy Relieves Aging via Rapid Immune Clearance of Senescent Cells

Cellular senescence is an irreversible and multifaceted process inducing tissue dysfunction and organismal aging, and thus the clearance of senescent cells can prevent or delay the onset of aging-related pathologies. Herein, we developed an augmented photothermal therapy strategy integrated with an antibody against β2-microglobulin (aB2MG) and an immune adjuvant imiquimod (R837) to effectively accelerate senescent cell apoptosis and clearance under a near-infrared light. With this strategy, the designed CroR@aB2MG enables the targeting of senescent cells and the application of photothermal therapy concomitantly, the initiation of immune clearance subsequently, and finally the realization of protective effects against senescence. Our results showed that the photo-induced heating effect caused senescent cells to quickly undergo apoptosis and the synchronous immune response accelerated the clearance of senescent cells in vitro and in vivo. Therefore, this photoactivated speedy clearing strategy may provide an efficient way for the treatment of senescence-related diseases by eliminating senescent cells with biomaterials.

Distinguishing Molecular Mechanical Action from Photothermal and Photodynamic Behavior

Molecular motors (MM) are molecular machines, or nanomachines, that rotate unidirectionally upon photostimulation and perform mechanical work on their environment. In the last several years, it has been shown that the photomechanical action of MM can be used to permeabilize lipid bilayers, thereby killing cancer cells and pathogenic microorganisms and controlling cell signaling. The work contributes to a growing acknowledgement that the molecular actuation characteristic of these systems is useful for various applications in biology. However, the mechanical effects of molecular motion on biological materials are difficult to disentangle from photodynamic and photothermal action, which are also present when a light-absorbing fluorophore is irradiated with light. Here, an overview of the key methods used by various research groups to distinguish the effects of photomechanical, photodynamic, and photothermal action is provided. It is anticipated that this discussion will be helpful to the community seeking to use MM to develop new and distinctive medical technologies that result from mechanical disruption of biological materials.

Colorimetric and photothermal dual-mode immunosensor based on Ti3C2Tx/AuNPs nanocomposite with enhanced peroxidase-like activity for ultrasensitive detection of zearalenone in cereals

A novel peroxidase-like nanozyme has been constructed by decorating two-dimensional Ti3C2Tx nanosheets (Ti3C2Tx NSs) with gold nanoparticles (AuNPs) to develop a colorimetric and photothermal dual-mode immunosensor. The Ti3C2Tx/AuNPs nanocomposite-catalyzed 3,3',5,5'-tetramethylbenzidine (TMB)-H2O2 reaction system produces the one-electron oxidation product of TMB (oxTMB), which exhibits color change and strong near-infrared (NIR) laser-driven photothermal effect at 808 nm laser irradiation. Given these characteristics, the developed immunosensor achieves ultrasensitive dual-mode detection of zearalenone (ZEN) by measuring colorimetric and photothermal signals with a microplate reader and a portable infrared thermometer, respectively. Under optimal working conditions, the limit of detection (LOD) of ZEN is 0.15 pg mL-1 for the colorimetric mode and 0.48 pg mL-1 for the photothermal mode. In the analysis of actual contaminated cereals samples, the test result of this method was consistent with that of UPLC-MS/MS. The proposed colorimetric and photothermal dual-mode immunosensor offers a new strategy for the low-cost detection of hazardous substances. The application of a widely used household infrared thermometer makes the signal readout more convenient, which provides great prospects in food safety and environment inspection applications.

Second-Generation Soft Actuators Driven by NIR Light Based on Croconaine Dye-Doped Vitrimers

Soft actuators with photo-response can be selectively driven by the light source, but it is challenging to achieve a selective response of multiple components under a uniform light field, which is actually of great importance for the development of soft robots. In this work, a series of near-infrared light (NIR)-responsive vitrimers (CR-vitrimers) are synthesized by carboxylate transesterification using carboxyl-bearing croconaine dye (CR-800) as a photothermal agent (PTA). NIR-responsive liquid crystalline elastomers (CR-vitrimer-LCEs) under NIR laser (λmax = 808 nm) without the template can be further prepared. More importantly, the dynamic covalent bonding properties of vitrimer allow for the fabrication of a hand-shaped actuator by hot pressing, consisting of "fingers" with different NIR-response threshold values. After programming as needed, the hand-shaped actuator successfully achieves local and sequential control under a uniform NIR light field.

Water-solubility croconic acid-bisindole dye with morpholine ring for tumor NIRF/PA imaging and photothermal therapy activated by lysosome pH-response

A novel croconic acid-bisindole dye CR-630 with a morpholine ring showed good water-solubility and obvious lysosome-targeting. The protonation of the nitrogen atom in the indole and lysosome-targeting of morpholine ring let it exhibit stronger pH-responsive NIR/PA imaging and photothermal effect in the lysosome acidic microenvironment (pH 4.0-5.5) than in the tumor acidic microenvironment. In the animal study, compound CR-630 could NIRF/PA image in the tumor tissues in 1.5-2.0 h, effectively inhibit the growth of the tumor, and even ablate the tumor at the drug dose of 1 mg/kg. It also demonstrated good biosafety. This study gives a new idea to develop water-solubility organic dyes with lysosome targeting, stronger pH-responsive NIRF/PA imaging and PTT for breast cancer.

Rational Design of Biomaterials to Potentiate Cancer Thermal Therapy

Cancer thermal therapy, also known as hyperthermia therapy, has long been exploited to eradicate mass lesions that are now defined as cancer. With the development of corresponding technologies and equipment, local hyperthermia therapies such as radiofrequency ablation, microwave ablation, and high-intensity focused ultrasound, have has been validated to effectively ablate tumors in modern clinical practice. However, they still face many shortcomings, including nonspecific damages to adjacent normal tissues and incomplete ablation particularly for large tumors, restricting their wide clinical usage. Attributed to their versatile physiochemical properties, biomaterials have been specially designed to potentiate local hyperthermia treatments according to their unique working principles. Meanwhile, biomaterial-based delivery systems are able to bridge hyperthermia therapies with other types of treatment strategies such as chemotherapy, radiotherapy and immunotherapy. Therefore, in this review, we discuss recent progress in the development of functional biomaterials to reinforce local hyperthermia by functioning as thermal sensitizers to endow more efficient tumor-localized thermal ablation and/or as delivery vehicles to synergize with other therapeutic modalities for combined cancer treatments. Thereafter, we provide a critical perspective on the further development of biomaterial-assisted local hyperthermia toward clinical applications.

A water-soluble thiophene-croconaine dye with a high molar extinction coefficient for NIR fluorescence imaging-guided synergistic photothermal/photodynamic therapy of cancer

Phototherapeutic agents with near-infrared (NIR) fluorescence, strong reactive oxygen species generation and photothermal conversion capabilities are highly desirable for use in cancer therapy. Herein, a water-soluble NIR croconaine dye (TCR) with a thiophene-croconaine rigid core and two symmetric alkyl chains was designed and synthesized. TCR exhibits intense NIR absorption and fluorescence that peaked at 780 and 815 nm, respectively, with a high molar extinction coefficient of 1.19 × 10⁵ M^-1 cm^-1. Moreover, TCR has a high photothermal conversion efficiency of 77% and is capable of generating hydroxyl radicals (OH˙) under 735 nm laser irradiation. Based on these outstanding properties, TCR has proven its application in NIR fluorescence imaging-guided synergistic photothermal/photodynamic therapy of cancer.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Conjugated Organic Photothermal Films for Spatiotemporal Thermal Engineering

With the growth of photoenergy harvesting and thermal engineering, photothermal materials (PTMs) have attracted substantial interest due to their unique functions such as localized heat generation, spatiotemporal thermal controllability, invisibility, and light harvesting capabilities. In particular, π-conjugated organic PTMs show advantages over inorganic or metallic PTMs in thin film applications due to their large light absorptivity, ease of synthesis and tunability of molecular structures for realizing high NIR absorption, flexibility, and solution processability. This review is intended to provide an overview of organic PTMs, including both molecular and polymeric PTMs. A description of the photothermal (PT) effect and conversion efficiency (η_PT ) for organic films is provided. After that, the chemical structure and optical properties of organic PTMs are discussed. Finally, emerging applications of organic PT films from the perspective of spatiotemporal thermal engineering principles are illustrated.

PhotothermalPhage: A Virus-Based Photothermal Therapeutic Agent

Virus-like particles (VLPs) are multifunctional nanocarriers that mimic the architecture of viruses. They can serve as a safe platform for specific functionalization and immunization, which provides benefits in a wide range of biomedical applications. In this work, a new generation immunophotothermal agent is developed that adjuvants photothermal ablation using a chemically modified VLP called bacteriophage Qβ. The design is based on the conjugation of near-infrared absorbing croconium dyes to lysine residues located on the surface of Qβ, which turns it to a powerful NIR-absorber called PhotothermalPhage. This system can generate more heat upon 808 nm NIR laser radiation than free dye and possesses a photothermal efficiency comparable to gold nanostructures, yet it is biodegradable and acts as an immunoadjuvant combined with the heat it produces. The synergistic combination of thermal ablation with the mild immunogenicity of the VLP leads to effective suppression of primary tumors, reduced lung metastasis, and increased survival time.

Organelle-targeted photothermal agents for cancer therapy

Over the past ten years, advances in the field of organelle-targeted photothermal therapy (PTT) have stimulated the rapid development of organelle-targeted PTT agents as anticancer therapeutic agents. However, to the best of our knowledge, no comprehensive review of organelle-targeted PTT agents has been reported thus far. In this article, we have provided a structured approach for describing the different types and properties of each organelle-targeted PTT agent as well as the potential future therapeutic applications that were classified by their target organelles. Representative agents that have been used in the field of PTT since 2010 have been summarized and the most recent advances in improving the therapeutic efficacy across various types of cancers have also been highlighted.

Facile Synthesis of a Croconaine-Based Nanoformulation for Optoacoustic Imaging and Photothermal Therapy

Near-infrared (NIR) light absorbing theranostic agents can integrate optoacoustic imaging and photothermal therapy for effective personalized precision medicine. However, most of these agents face the challenges of unstable optical properties, material-associated toxicity, and nonbiodegradability, all of which limit their biomedical application. Several croconaine-based organic agents able to overcome some of these limitations have been recently reported, but these suffer from complicated multistep synthesis protocols. Herein, the use of CR760, a croconaine dye with excellent optical properties, is reported for nanoparticle formulation and subsequent optoacoustic imaging and photothermal therapy. Importantly, CR760 can be conveniently prepared in a single step from commercially available materials. Furthermore, CR760 can be covalently attached, via a polyethylene glycol linker, to the α_v β₃ integrin ligand c(RGDyC), resulting in self-assembled nanoparticles (NPs) with cancer-targeting capability. Such CR760RGD-NPs exhibit strong NIR absorption, high photostability, high optoacoustic generation efficiency, and active tumor-targeting, making them ideal candidates for optoacoustic imaging. Due to favorable electron transfer, CR760RGD-NPs display a 45.37% photothermal conversion efficiency thereby rendering them additionally useful for photothermal therapy. Targeted tumor elimination, biosafety, and biocompatibility are demonstrated in a 4T1 murine breast tumor model. This work points to the use of CR760RGD-NPs as a promising nanoagent for NIR-based cancer phototheranostics.

Fluorescence emission enhancement of a T-shaped benzimidazole with a mechanically-interlocked 'suit'

A fluorescent T-shaped benzimidazole was successfully designed and interlocked in a bicyclic macrocycle to form a suit[1]ane through supramolecular templated-synthesis. Compared with the bare fluorophore, suit[1]ane requires nearly two times the concentration to initialize the aggregation-caused quenching effect in solution. Furthermore, an 8-fold higher solid-state fluorescence quantum yield (21.7%) is also achieved. By taking advantage of mechanical bonding and molecular packing, such fluorescence emission enhancement through formation of a suitane opens the way to new complex fluorescent materials.

880 nm NIR-Triggered Organic Small Molecular-Based Nanoparticles for Photothermal Therapy of Tumor

Photothermal therapy (PTT) has received constant attention as an efficient cancer therapy method due to locally selective treatment, which is not affected by the tumor microenvironment. In this study, a novel 880 nm near-infrared (NIR) laser-triggered photothermal agent (PTA), 3TT-IC-4Cl, was used for PTT of a tumor in deep tissue. Folic acid (FA) conjugated amphiphilic block copolymer (folic acid-polyethylene glycol-poly (β-benzyl-L-aspartate)₁₀, FA-PEG-PBLA₁₀) was employed to encapsulate 3TT-IC-4Cl by nano-precipitation to form stable nanoparticles (TNPs), and TNPs exhibit excellent photothermal stability and photothermal conversion efficiency. Furthermore, the in vitro results showed TNPs display excellent biocompatibility and significant phototoxicity. These results suggest that 880 nm triggered TNPs have great potential as effective PTAs for photothermal therapy of tumors in deep tissue.

Single-Molecule Förster Resonance Energy Transfer-Based Photosensitizer for Synergistic Photodynamic/Photothermal Therapy

Photosensitizers (PSs) inevitably release a large amount of energy in the form of fluorescence during photodynamic therapy (PDT). However, under the premise of satisfying fluorescence imaging, a large amount of energy is lost, which limits the efficiency of tumor therapy. Accordingly, in this study, we developed a new strategy (BDP-CR) using the single-molecule Förster resonance energy transfer (smFRET) mechanism to transfer part of the fluorescent energy into heat for combined PDT and photothermal therapy (PTT) featuring the "1 + 1 > 2" amplification effect. Under the 671 nm light irradiation, BDP-CR can produce singlet oxygen (¹O₂) for PDT based on the BDP moiety and also generate hyperthermia to achieve the PTT effect by exciting CR based on the smFRET effect, which effectively kills cancer cells both in vitro and in vivo. This strategy exhibits a broad absorption peak with strong light-harvesting ability, which improves photon utilization for treatment while realizing fluorescence imaging. Of note, owing to the smFRET effect, we achieve a combination treatment outcome at relatively low concentrations and light doses. Thus, we believe that this design concept will provide a new strategy for single-molecule FRET photosensitizers in combination therapy of cancer with potential clinical application prospects.

Synthesis of high molar extinction coefficient push–pull tricyanofuran-based disperse dyes: Biological activity and dyeing performance

Novel push–pull tricyanofuran-based disperse dyes demonstrated high extinction coefficient, good antimicrobial performance and high colorfastness on polyester fibers.

Photothermal Microscopy: Imaging the Optical Absorption of Single Nanoparticles and Single Molecules

The photothermal (PT) signal arises from slight changes of the index of refraction in a sample due to absorption of a heating light beam. Refractive index changes are measured with a second probing beam, usually of a different color. In the past two decades, this all-optical detection method has reached the sensitivity of single particles and single molecules, which gave birth to original applications in material science and biology. PT microscopy enables shot-noise-limited detection of individual nanoabsorbers among strong scatterers and circumvents many of the limitations of fluorescence-based detection. This review describes the theoretical basis of PT microscopy, the methodological developments that improved its sensitivity toward single-nanoparticle and single-molecule imaging, and a vast number of applications to single-nanoparticle imaging and tracking in material science and in cellular biology.

Biradical-Featured Stable Organic-Small-Molecule Photothermal Materials for Highly Efficient Solar-Driven Water Evaporation

With recent progress in photothermal materials, organic small molecules featured with flexibility, diverse structures, and tunable properties exhibit unique advantages but have been rarely applied in solar-driven water evaporation owing to limited sunlight absorption resulting in low solar-thermal conversion. Herein, a stable croconium derivative, named CR-TPE-T, is designed to exhibit the unique biradical property and strong π-π stacking in the solid state, which facilitate not only a broad absorption spectrum from 300 to 1600 nm for effective sunlight harvesting, but also highly efficient photothermal conversion by boosting nonradiative decay. The photothermal efficiency is evaluated to be 72.7% under 808 nm laser irradiation. Based on this, an interfacial-heating evaporation system based on CR-TPE-T is established successfully, using which a high solar-energy-to-vapor efficiency of 87.2% and water evaporation rate of 1.272 kg m^-2 h^-1 under 1 sun irradiation are obtained, thus making an important step toward the application of organic-small-molecule photothermal materials in solar energy utilization.

Cell organelle targeting of near-infrared croconaine dye controls photothermal outcome

Near-infrared croconaine-peptide conjugates that target the cell nucleus promote photothermal induced cell death. In contrast, a croconaine-morpholine conjugate that targets the cell lysosomes promotes lysosome permeabilization without measurable cell phototoxicity.

A hydrogen-bonded polymer constructed from mechanically interlocked, suit[1]ane monomers

A T-shaped 2,4,7-substituted benzimidazolium “axle” with two ester functionalities and a 24-membered crown ether “wheel” with appendages containing terminal olefin groups were threaded — axle through wheel — to form a [2]pseudorotaxane. Grubbs’ ring-closing metathesis (RCM) was then used to form a third loop and create a bicyclic cage that fully encapsulates the axle and permanently interlocks the two molecular components creating a suit[1]ane. There are no bulky groups on the axle to prevent unthreading, but the axle is trapped due to the cage-like nature of the newly created polyether host. After hydrolysis of the esters groups to carboxylic acids, this novel mechanically interlocked molecule (MIM) polymerizes in the solid state. The structure of the resulting supramolecular polymer was determined by single-crystal X-ray diffraction and contains linear one-dimensional tapes of suit[1]ane monomers linked by intermolecular hydrogen bonding between the carboxylic acid groups.

Recent Development of Photothermal Agents (PTAs) Based on Small Organic Molecular Dyes

Photothermal therapy (PTT) has attracted great attention due to its noninvasive and effective use against cancer. Various photothermal agents (PTAs) including organic and inorganic PTAs have been developed in the last decades. Organic PTAs based on small-molecule dyes exhibit great potential for future clinical applications considering their good biocompatibility and easy chemical modification or functionalization. In this review, we discuss the recent progress of organic PTAs based on small-molecule dyes for enhanced PTT. We summarize the strategies to improve the light penetration of PTAs, methods to enhance their photothermal conversion efficiency, how to optimize PTAs' delivery into deep tumors, and how to resist photobleaching under repeated laser irradiation. We hope that this review can rouse the interest of researchers in the field of PTAs based on small-molecule dyes and help them to fabricate next-generation PTAs for noninvasive cancer therapy.

Croconaine Rotaxane Dye with 984 nm Absorption: Wavelength-Selective Photothermal Heating

Croconaines are an emerging class of near-infrared dyes that are useful for various sensing, photothermal, optoelectronic, and photoacoustic applications. Previous work encapsulated a dumbbell-shaped croconaine dye whose structure contains two thiophene flanking units inside a tetralactam macrocycle and produced a croconaine rotaxane 1 with a narrow 824 nm absorption band. Herein, a new rotaxane 2 is reported that encapsulates a croconaine dye with two thienothiophene flanking units. The new croconaine rotaxane 2 exhibits a narrow 984 nm absorption band that is distinct from the 824 nm absorption of rotaxane 1. Photothermal heating experiments showed that an 830 nm diode laser selectively heats a solution containing rotaxane 1, with no heating of a solution containing rotaxane 2. Conversely, a 980 nm diode laser selectively heats a solution containing rotaxane 2, with no heating of a solution containing rotaxane 1. The new croconaine rotaxane 2 shows no fatigue after four cycles of laser heating and cooling.

Photothermal therapy and photoacoustic imaging via nanotheranostics in fighting cancer

The nonradiative conversion of light energy into heat (photothermal therapy, PTT) or sound energy (photoacoustic imaging, PAI) has been intensively investigated for the treatment and diagnosis of cancer, respectively. By taking advantage of nanocarriers, both imaging and therapeutic functions together with enhanced tumour accumulation have been thoroughly studied to improve the pre-clinical efficiency of PAI and PTT. In this review, we first summarize the development of inorganic and organic nano photothermal transduction agents (PTAs) and strategies for improving the PTT outcomes, including applying appropriate laser dosage, guiding the treatment via imaging techniques, developing PTAs with absorption in the second NIR window, increasing photothermal conversion efficiency (PCE), and also increasing the accumulation of PTAs in tumours. Second, we introduce the advantages of combining PTT with other therapies in cancer treatment. Third, the emerging applications of PAI in cancer-related research are exemplified. Finally, the perspectives and challenges of PTT and PAI for combating cancer, especially regarding their clinical translation, are discussed. We believe that PTT and PAI having noteworthy features would become promising next-generation non-invasive cancer theranostic techniques and improve our ability to combat cancers.

1,5-Diaminonaphtalene is a Highly Performing Electron-Transfer Secondary-Reaction Matrix for Laser Desorption Ionization Mass Spectrometry of Indolenine-Based Croconaines

Croconaine dyes are appealing molecules synthesized via the condensation of croconic acid and reactive electron-donating aromatic or heterocyclic systems. Here, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) investigation of indolenine-based croconaines is presented for the first time. Archetype proton-transfer matrices, such as 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA), 9-aminoacridine (9AA) as the protonating/deprotonating matrix, and electron-transfer (ET) secondary-reaction matrices, such as 1,5-diaminonapthalene (DAN) and trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB), were investigated. DHB, CHCA, and 9AA generate a mix of odd-electron molecular ions and protonated, sodiated, and potassiated adducts. Among the ET matrices, DAN was found to be capable of directing the ionization process toward the exclusive formation of odd-electron molecular ions M^+• without fragmentation. MALDI tandem MS provides useful structural characterization of croconaine dyes, thus making identification very straightforward for all investigated compounds. Interestingly the fragmentation of bromo-containing croconaines revealed, for the first time, the gas-phase formation of a bromime cation [Br]⁺.

Synthesis and Computational Study of Semicroconaines and Nonsymmetric Croconaines

The synthesis of two new dye families of croconic acid derivatives, semicroconaine and nonsymmetric croconaine dyes, is reported for the first time. These compounds show strong absorption in the UV-visible and NIR, respectively. Semicroconaine dyes were obtained by a scalable and efficient condensation of croconic acid with aromatic heterocyclic methylene-active compounds. The subsequent reaction of the semicroconaine dyes with aromatic heterocyclic compounds affords nonsymmetric croconaines. The structure and electronic properties of the synthesized compounds have been investigated by preliminary theoretical calculations at DFT level of approximation.

Molecular Photoacoustic Contrast Agents: Design Principles & Applications

Photoacoustic imaging (PAI) is a rapidly growing field which offers high spatial resolution and high contrast for deep-tissue imaging in vivo. PAI is nonionizing and noninvasive and combines the optical resolution of fluorescence imaging with the spatial resolution of ultrasound imaging. In particular, the development of exogenous PA contrast agents has gained significant momentum of late with a vastly expanding complexity of dye materials under investigation ranging from small molecules to macromolecular proteins, polymeric and inorganic nanoparticles. The goal of this review is to survey the current state of the art in molecular photoacoustic contrast agents (MPACs) for applications in biomedical imaging. The fundamental design principles of MPACs are presented and a review of prior reports spanning from early-to-current literature is put forth.

Decorating gold nanostars with multiwalled carbon nanotubes for photothermal therapy

Gold nanoparticles and carbon nanotubes have attracted substantial attention in recent years for their potential applications in photothermal therapy (PTT) as an emerging breakthrough in cancer treatment. Herein, a hybrid nanomaterial of gold nanostars/multiwalled carbon nanotubes (MWCNTs) was synthesized by two-step reduction via the control of several synthetic conditions such as the reducing agent, pH value, concentration and ratio of reagents. The material shows good biocompatibility and high photothermal conversion efficiency, demonstrating its applicability in PTT. The lack of surfactant in the synthesis process made the hybrid nanomaterial cell-friendly, with no effects on viability in vitro. The MWCNT/gold nanostars hybrid nanomaterial presented 12.4% higher photothermal efficiency than gold nanostars alone and showed a 2.4-fold increase over gold nanospheres based on a heating test under 808 nm laser irradiation. Moreover, the MWCNTs/gold nanostars at low concentration (0.32 nM) exhibited remarkably improved photothermal cancer cell-killing efficacy, which may be attributed to the surface plasmon resonance absorption of the gold nanostars and the combined effects of enhanced coupling between the MWCNTs and gold nanostars. Collectively, these results demonstrate that the MWCNTs/gold nanostars developed herein show prominent photothermal value, and thus may serve as a novel photothermal agent for cancer therapy.

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H2O2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H2O2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL-1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.

Radiolabeled Angiogenesis-Targeting Croconaine Nanoparticles for Trimodality Imaging Guided Photothermal Therapy of Glioma

To meet the criteria of effective theranostics, biocompatible nanomedicine endowing intrinsic therapeutic and imaging properties have gained extraordinary momentum. In this study, an ultra-stable near-infrared (NIR) dye croconaine (CR780) was engineered with arginine-glycine-aspartic acid (RGD) peptide and polyethylene glycol (PEG), which was then self-assembled into uniform nanoparticles (NPs). These RGD-CR780-PEG5K assemblies were radiolabeled with ¹²⁵I through a facile standard Iodo-Gen method. The resulting [¹²⁵I]RGD-CR780-PEG5K NPs showed effective accumulation in α_vβ₃ integrin expressing glioblastoma, as evidenced by single photon emission computed tomography (SPECT)/CT and NIR fluorescence imaging. More importantly, high-resolution photoacoustic imaging revealed that these NPs selectively targeted to angiogenic tumor vessels. With the favorable tumor selective accumulation and high photothermal conversion efficiency, the [¹²⁵I]RGD-CR780-PEG5K NPs allowed thorough tumor ablation and inhibition of tumor relapse at a relatively low laser energy (0.5 W/cm²). Overall, this work offers a proper methodology to fabricate tumor-targeted multi-modal nanotheranostic agents, providing great opportunity for precision imaging and cancer therapy.

Organic molecule-based photothermal agents: an expanding photothermal therapy universe

Over the last decade, organic photothermal therapy (PTT) agents have attracted increasing attention as a potential complement for, or alternative to, classical drugs and sensitizers involving inorganic nanomaterials. In this tutorial review, we provide a structured description of the main classes of organic photothermal agents and their characteristics. Representative agents that have been studied in the context of photothermal therapy since 2000 are summarized and recent advances in using PTT agents to address various cancers indications are highlighted.

Light-triggered release from dye-loaded fluorescent lipid nanocarriers in vitro and in vivo

Light is an attractive trigger for release of active molecules from nanocarriers in biological systems. Here, we describe a phenomenon of light-induced release of a fluorescent dye from lipid nano-droplets under visible light conditions. Using auto-emulsification process we prepared nanoemulsion droplets of 32nm size encapsulating the hydrophobic analogue of Nile Red, NR668. While these nano-droplets cannot spontaneously enter the cells on the time scale of hours, after illumination for 30s under the microscope at the wavelength of NR668 absorption (535nm), the dye showed fast accumulation inside the cells. The same phenomenon was observed in zebrafish, where nano-droplets initially staining the blood circulation were released into endothelial cells and tissues after illumination. Fluorescence correlation spectroscopy revealed that laser illumination at relatively low power (60mW/cm²) could trigger the release of the dye into recipient media, such as 10% serum or blank lipid nanocarriers. The photo-release can be inhibited by deoxygenation with sodium sulfite, suggesting that at least in part the release could be related to a photochemical process involving oxygen, though a photo-thermal effect could also take place. Finally, we showed that illumination of NR668 can provoke the release into the cells of another highly hydrophobic dye co-encapsulated into the lipid nanocarriers. These results suggest dye-loaded lipid nano-droplets as a prospective platform for preparation of light-triggered nanocarriers of active molecules.

Reversible mechanical protection: building a 3D "suit" around a T-shaped benzimidazole axle

The T-shaped benzimidazolium/crown ether recognition motif was used to prepare suit[1]anes. These novel mechanically interlocked molecules (MIMs) were fully characterized by 1H and 13C NMR spectroscopy, single-crystal X-ray diffraction, UV-vis absorption and fluorescence spectroscopy. By conversion to a suit[1]ane, a simple benzimidazole was shown to be protected from deprotonation by strong base. Moreover, it was demonstrated that this unique three-dimensional encapsulation can be made reversible, thus introducing the concept of "reversible mechanical protection"; a protecting methodology that may have potential applications in synthetic organic chemistry and the design of molecular machinery.

Highly specific noninvasive photoacoustic and positron emission tomography of brain plaque with functionalized croconium dye labeled by a radiotracer

Highly-efficient targeting probes are desirable for disease diagnosis and functional imaging. However, most of the current near-infrared (NIR) probes suffer from low signal conversion, insufficient photostability, poor probe specificity, and limited functions. Herein, an NIR ultrahigh absorbing croconium dye for amyloid (CDA) was designed and synthesized to specifically bind to cerebrovascular amyloid without antibody linkage. This unique CDA is able to strongly bind the hydrophobic channels of amyloid beta (Aβ) fiber with a very strong binding energy of -9.3 kcal mol-1. Our experimental results demonstrate that the amphipathic dye with an intense absorption peak at 800 nm generated a significant local temperature surge under low-power laser irradiation. Compared with representative prominent indocyanine green, Prussian blue, and gold nanorods, this probe can produce the strongest photoacoustic signal based on the same mass concentration. Labeled with radioactive 18F, this multifunctional probe allowed for the ultrasensitive photoacoustic tomography (PAT)/positron emission tomography (PET)/fluorescence imaging of Aβ plaques in the brain cortex. Featured with high spatial resolution and optical specificity, PAT was intrinsically suitable for imaging pathological sites on cortical vessels, whereas PET revealed whole-body anatomy with quantitative biodistribution information. Our study shows that a CDA-based functionalized dye aided with PAT and PET is capable of plaque diagnosis and localization.