Heptamethine Cyanine Research Articles

Heptamethine cyanines in bioorthogonal chemistry

Due to their excellent fluorescence properties and biological function, cyanine dyes have been widely applied in biological imaging. Heptamethine cyanine (Cy7) dyes, as a type of classic near-infrared (NIR) fluorescent dyes, are considered as one of the effective fluorescent tools in the living organisms due to their good biocompatibility and very low background interference. Bioorthogonal reactions performed in living cells and tissues have developed by leaps and bounds in recent years. The NIR fluorescent labeling technique involving cyanine has attracted widespread attention. This review summarizes their recent application in the field of bioorthogonal imaging, mainly concluding Cy7-type dyes, labeling strategy, bioimaging application, etc. We expect this work can provide some helps for the studies of NIR bioorthogonal reaction in vivo.

Multiple Ligand Simultaneous Docking of Antiviral Drugs and Cyanine Dyes with Proteins

Protein nanoparticles are currently regarded as promising biocompatible and biodegradable systems for targeted delivery of different types of pharmacological agents. Prior to fabricating such kind of drug nanocarriers it is reasonable to evaluate the drug-protein binding affinity and possible interaction modes using the computational tools, particularly, the molecular docking technique. The present study was undertaken to evaluate the possibility of creating the protein nanoparticles carrying the antiviral drugs and cyanine dyes as visualizing agents. The components of the examined systems included endogenous functional proteins cytochrome c, serum albumin, lysozyme and insulin, antiviral drugs favipiravir, molnupiravir, nirmatrelvir and ritonavir, mono- and heptamethinecyanine dyes. Using the multiple ligand simultaneous docking technique, it was demonstrated that: i) the drugs and the dyes occupy different binding sites on the protein molecule and do not interfere with each other; ii) the heptamethines AK7-5 and AK7-6 possess the highest affinity for the proteins; iii) among the examined systems the strongest complexes are formed between the heptamethine dyes and serum albumin. Taken together, the results obtained indicate that albumin-based nanoparticles functionalized by the heptamethine cyanine dyes can be used for targeted delivery of the explored antiviral agents.

Synthesis and evaluation of novel mitochondria-specific near-IR stains based on triphenylphosphonium-heptamethine cyanines

Mitochondria play a crucial role in many biological processes that ensure cell viability. Dysfunction of mitochondria can therefore lead to serious disorders, including cardiovascular disease and cancer. This makes mitochondria desirable targets for selective imaging and targeted therapy. Currently, several mitochondria-specific stains have been developed; however, most of them suffer from low specificity and/or poor brightness. Herein, we developed a series of novel near-IR heptamethine cyanine dyes containing mitochondria-specific triphenylphosphonium (TPP+) groups. These dyes were investigated in comparison to the recently reported cyanine Cy-TPP for staining mitochondria in human breast cancer SK-BR-3 and MDA-MB-231 cell lines. Several new dyes presented better visualization and higher fluorescence intensity in mitochondria than Cy-TPP. These dyes are considered promising mitochondria-specific stains for biomedical applications based on cell mitochondria visualization.

Enhanced Lifetime of Cyanine Salts in Dilute Matrix Luminescent Solar Concentrators via Counterion Tuning.

Organic luminophores offer great potential for energy harvesting and light emission due to tunable spectral properties, strong luminescence, high solubility, and excellent wavelength-selectivity. To realize their full potential, the lifetimes of luminophores must extend to many years under illumination. Many organic luminophores, however, have a tendency to degrade and undergo rapid photobleaching, leading to the perception of intrinsic instability of organic molecules. In this work we demonstrate that by exchanging the counterion of a heptamethine cyanine salt the photostability and corresponding lifetime of dilute cyanine salts can be enhanced by orders of magnitude from 10 hours to an extrapolated lifetime of greater than 65,000 hours under illumination. To help correlate and comprehend the underlying mechanism behind this phenomenon, the water contact angle and binding energy of each pairing were measured and calculated. We find that increased water contact angle, and therefore increasing hydrophobicity, generally correlate to improved lifetimes. Similarly, a lower absolute binding energy between cation and anion correlates to increased lifetimes. Utilizing the binding energy formalism, we predict the stability of a new anion and experimentally verify with good consistency. Moving forward, these factors could be used to rapidly screen and identify highly photostable organic luminophore salt systems for a range of energy harvesting and light emitting applications.

Short-wave infrared fluorescence imaging of near-infrared dyes with robust end-tail emission using a small-animal imaging device.

Commercially available near-infrared (NIR) dyes, including indocyanine green (ICG), display an end-tail of the fluorescence emission spectrum detectable in the short-wave infrared (SWIR) window. Imaging methods based on the second NIR spectral region (1,000-1,700 nm) are gaining interest within the biomedical imaging community due to minimal autofluorescence and scattering, allowing higher spatial resolution and depth sensitivity. Using a SWIR fluorescence imaging device, the properties of ICG vs. heptamethine cyanine dyes with emission >800 nm were evaluated using tissue-simulating phantoms and animal experiments. In this study, we tested the hypothesis that an increased rigidity of the heptamethine chain may increase the SWIR imaging performance due to the bathochromic shift of the emission spectrum. Fluorescence SWIR imaging of capillary plastic tubes filled with dyes was followed by experiments on healthy animals in which a time series of fluorescence hindlimb images were analyzed. Our findings suggest that higher spatial resolution can be achieved even at greater depths (>5 mm) or longer wavelengths (>1,100 nm), in both tissue phantoms and animals, opening the possibility to translate the SWIR prototype toward clinical application.

Interaction of Near-Infrared (NIR)-Light Responsive Probes with Lipid Membranes: A Combined Simulation and Experimental Study.

Cancer is considered a major societal challenge for the next decade worldwide. Developing strategies for simultaneous diagnosis and treatment has been considered a promising tool for fighting cancer. For this, the development of nanomaterials incorporating prototypic near-infrared (NIR)-light responsive probes, such as heptamethine cyanines, has been showing very promising results. The heptamethine cyanine-incorporating nanomaterials can be used for a tumor's visualization and, upon interaction with NIR light, can also produce a photothermal/photodynamic effect with a high spatio-temporal resolution and minimal side effects, leading to an improved therapeutic outcome. In this work, we studied the interaction of 12 NIR-light responsive probes with lipid membrane models by molecular dynamics simulations. We performed a detailed characterization of the location, orientation, and local perturbation effects of these molecules on the lipid bilayer. Based on this information, the probes were divided into two groups, predicting a lower and higher perturbation of the lipid bilayer. From each group, one molecule was selected for testing in a membrane leakage assay. The experimental data validate the hypothesis that molecules with charged substituents, which function as two polar anchors for the aqueous phase while spanning the membrane thickness, are more likely to disturb the membrane by the formation of defects and pores, increasing the membrane leakage. The obtained results are expected to contribute to the selection of the most suitable molecules for the desired application or eventually guiding the design of probe modifications for achieving an optimal interaction with tumor cell membranes.

Development of a sensitive LC-MS/MS method for the quantification of theranostic agent cypate in mouse plasma and application to a pharmacokinetic study

Cypate, a heptamethine cyanine dye, is a prototypic near-infrared (NIR) theranostic agent for optical imaging and photothermal therapy. In the present study, a selective, sensitive, and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantitation of cypate in mouse plasma. The chromatographic separation was achieved using a short C18 column (2.1 mm × 50 mm, 5 μm) with a run time of 5 min. The MS was operated in multiple reaction monitoring (MRM) mode via positive electrospray ionization. The ion transitions for cypate and internal standard IR-820 were m/z 626.3 → 596.3 and m/z 827.4 → 330.2, respectively. The method was linear over a concentration range of 1.0–500 ng/mL. The within-run and between-run precision was less than 14.4% with accuracy in the range of −13.4% ∼ 9.8%. The validated method was successfully applied to a pharmacokinetic study of cypate in mice following intravenous administration.

Photo-induced Electron Transfer-triggered Structure Deformation Promoting Near-Infrared Photothermal Conversion for tumor therapy.

Photothermal therapy (PTT) is a promising approach to cancer treatment. Heptamethine cyanine (Cy7) is an attractive photothermal reagent because of its large molar absorption coefficient, good biocompatibility, and absorption of near-infrared irradiation. However, the photothermal conversion efficiency of Cy7 is limited without ingenious excitation-state regulation. In this study, the photothermal conversion ability of Cy7 is efficiently enhanced based on photo-induced electron transfer (PET)-triggered structural deformation. Three Cy7 derivatives, whose Cl is replaced by carbazole, phenoxazine, and phenothiazine at the meso-position (CZ-Cy7, PXZ-Cy7, and PTZ-Cy7), are presented as examples to demonstrate the regulation of the energy release of the excited states. Because the phenothiazine moiety exhibits an obvious PET-induced structural deformation in the excited state, which quenches the fluorescence and inhibits intersystem crossing of S1 →T1 , PTZ-Cy7 exhibits a photothermal conversion efficiency (PCE) as high as 77.5%. As a control, only PET occurs in PXZ-Cy7, with a PCE of 43.5%. Furthermore, the PCE of CZ-Cy7 is only 13.0% because there is no PET process. Interestingly, PTZ-Cy7 self-assembles into homogeneous nanoparticles exhibiting passive tumor-targeting properties. This study provides a new strategy for excited-state regulation for photoacoustic (PA) imaging-guided PTT with high efficiency. This article is protected by copyright. All rights reserved.

All-in-One Heptamethine Cyanine Amphiphiles for Dual Imaging-Guided Chemo-Photodynamic-Photothermal Therapy of Breast Cancer.

Developing a theranostic system that integrates multimodal imaging, synergistic therapeutic, and formulation entities is a promising strategy for efficient cancer treatment. However, the complexity and safety concerns of multiple functional entities hinder their clinical translation. Herein, versatile "all-in-one" heptamethine cyanine amphiphiles (PEG-Cy-Fs) with multiple favorable capabilities, including fluorine-19 magnetic resonance imaging (19 F MRI), near-infrared fluorescence imaging (NIR FLI), photodynamic therapy (PDT), photothermal therapy (PTT), polyethylene glycolation (PEGylation) and high biocompatibility, are developed for the convenient construction of theranostic platforms. Amphiphiles PEG-Cy-Fs are synthesized on a multi-hundred-milligram scale with high efficacy, which self-assembled with a chemotherapy drug tamoxifen (TAM) into monodisperse and stable nanoparticles (SoFoTm/PEG-Cy-F18 ) with "turned on" FLI, sensitive 19 F MRI, mitochondria-targeting ability, high PDT and PTT efficacy, and PEGylation-optimized pharmacokinetics. The selective accumulation of SoFoTm/PEG-Cy-F18 in xenograft MCF-7 tumor with a long retention time (>10 days) enabled 19 F MRI-NIR FLI-guided chemo-photodynamic-photothermal therapy (chemo-PDT-PTT) of breast cancer with high therapeutical index in mice. The "all-in-one" heptamethine cyanine amphiphile may facilitate the convenient and standardized preparation of high-performance theranostics systems for clinical translation.

Near-infrared fluorophore IR-61 delays postovulatory aging of mouse oocytes through suppressing oxidative stress mediated by mitochondrial protection.

Postovulatory aging can trigger deterioration of oocyte quality and subsequent embryonic development, and thus reduce the success rates of assisted reproductive technology (ART). The molecular mechanisms underlying postovulatory aging, and preventative strategies, remain to be explored. The near-infrared fluorophore IR-61, a novel heptamethine cyanine dye, has the potential for mitochondrial targeting and cell protection. In this study, we found that IR-61 accumulated in oocyte mitochondria and reduced the postovulatory aging-induced decline in mitochondrial function, including mitochondrial distribution, membrane potential, mtDNA number, ATP levels, and mitochondrial ultrastructure. In addition, IR-61 rescued postovulatory aging-caused oocyte fragmentation, defects in spindle structure, and embryonic developmental potential. RNA sequencing analysis indicated that the postovulatory aging-induced oxidative stress pathway might be inhibited by IR-61. We then confirmed that IR-61 decreased the levels of reactive oxygen species and MitoSOX, and increased GSH content in aged oocytes. Collectively, the results indicate that IR-61 may prevent postovulatory aging by rescuing oocyte quality, promoting successful rate in ART procedure.

Synthesis of Glutathione-Responsive Cyclomatrix Polyphosphazene for Multimodal Theranostic Nanodrug Delivery

In this work, a multimodal (chemotherapeutic/photodynamic/photothermal) theranostic nanodrug delivery platform was developed based on the synergetic action of self-framed polyphosphazene prodrug and heptamethine cyanine dye IR-780. First, an electronegative glutathione (GSH)-responsive polyphosphazene prodrug abbreviated as HGEH was prepared via multicomponent condensation reaction of genistein (GEN), bis-(4-hydroxyphenyl)-disulfide, and hexachlorocyclotriphosphazene. The particle size of drug (GEN)-containing HGEH nanoparticles is adjustable. Subsequently, cationic near-infrared photosensitizer IR-780 was adsorbed onto the electron-rich HGEH to obtain the multimodal theranostic nanodrug delivery platform HGEH-IR780. The platform was demonstrated to retain high stability in avoiding drug leakage and enable controlled drug release in response to the tumor microenvironment, in which a higher GSH concentration exists. The in vitro experiments show that HGEH-IR780 undergoes photothermal and photodynamic processes to concurrently generate heat and reactive oxygen species for efficiently killing mouse breast cancer cells (4T1) upon exposure to a single-bandwidth near-infrared laser (808 nm). Specifically, HGEH-IR780 inhibits 4T1 cells by up to 80% at a concentration of 100 μg/mL. The as-developed HGEH-IR780 exhibits promising results in GSH-responsive anticancer activity and photodynamic/photothermal therapy, which provides a reference for the construction of the polyphenol flavonoid multimodal therapeutic nanoplatform.

Recent progress on near-infrared fluorescence heptamethine cyanine dye-based molecules and nanoparticles for tumor imaging and treatment.

Recenly, near-infrared fluorescence heptamethine cyanine dyes have shown satisfactory values in bioengineering, biology, and pharmacy especially in cancer diagnosis and treatment, owing to their excellent fluorescence property and biocompatibility. In order to achieve broad application prospects, diverse structures, and chemical properties of heptamethine cyanine dyes have been designed to develop novel functional molecules and nanoparticles over the past decade. For fluorescence and photoacoustic tumor imaging properties, heptamethine cyanine dyes are equipped with good photothermal performance and reactive oxygen species production properties under near-infrared light irradiation, thus holding great promise in photodynamic and/or photothermal cancer therapies. This review offers a comprehensive scope of the structures, comparisons, and applications of heptamethine cyanine dyes-based molecules as well as nanoparticles in tumor treatment and imaging in current years. Therefore, this review may drive the development and innovation of heptamethine cyanine dyes, significantly offering opportunities for improving tumor imaging and treatment in a precise noninvasive manner. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Heavy-atom engineered hypoxia-responsive probes for precisive photoacoustic imaging and cancer therapy

Photoacoustic agents combining photodynamic therapy (PDT) and photothermal therapy (PTT) functions have emerged as potent theranostic agents for combating cancer. The molecular approaches for enhancing the near-infrared (NIR)-absorption and maximizing non-radiative energy transfer are essential for effective photoacoustic imaging (PAI) and therapy applications. In addition, such molecules with high specificity and affinity to cancer cells are urgently needed, which would further decrease the side effect during treatments. In this study, we applied a heavy-atom engineering strategy and introduced p-aminophenol, -thio, and -seleno moieties into NIR heptamethine cyanine (Cy7) skeleton (Cy7-X-NH2, X = O, S, Se) to significantly increase photothermal conversion efficiency for PTT and promote intersystem crossing for PDT. Additionally, we designed a series of nitroreductase (NTR)-activated photoacoustic probes (Cy7-X-NO2, X = O, S, Se), and target hypoxic tumors with NTR overexpression. Our prostate cancer targeting probe, Cy7-Se-NO2-KUE, exhibited specific tumor photoacoustic signals and effective tumor killing through outstanding synergistic PTT/PDT in vivo. These findings highlighted a versatile strategy for cancer photoacoustic diagnosis and enhanced phototherapy.

Synthesis of Near-Infrared-Absorbing Anionic Heptamethine Cyanine Dyes with Trifluoromethyl Groups.

A novel anionic heptamethine cyanine (HMC) dye with two trifluoromethyl groups that selectively absorb near-infrared light is synthesized. When contrasted with previously studied anionic HMC dyes with substituents such as methyl, phenyl, and pentafluorophenyl groups, the trifluoromethylated dye displays a red-shifted maximum absorption wavelength (for instance, 948 nm in CH2Cl2) along with enhanced photostability. Furthermore, HMC dyes with broad absorption in the near-infrared region are synthesized by combining a trifluoromethylated anionic HMC dye with a cationic HMC dye as a counterion.

Heptamethine Cyanine‐Based Nanotheranostics with Catalase‐Like Activity for Synergistic Phototherapy of Cancer

AbstractSingle‐molecule photosensitizers (PSs) for synergistic phototherapy are desirable but highly challenging, due to the competitive relationship between photothermal (PTT) and photodynamic therapy (PDT). Herein, a supramolecular strategy is developed that can tune the stacking pattern of PS molecules in their aggregates to optimize the PTT/PDT efficiency. Specifically, near‐infrared (NIR) heptamethine cyanines (Cy7) are synthesized using tricyanofuran (TCF) as the acceptor and benzothiazole (BTH)/indole (IND) as the donor, where BTH is a less hydrogen‐bonded tecton relative to IND. Both IND‐Cy7‐TCF and BTH‐Cy7‐TCF have similar photophysical properties at the molecular level, but BTH‐Cy7‐TCF in aggregated state exhibits higher singlet oxygen quantum yield (1.3% vs 0.2%) and competitive photothermal conversion efficiency (56.4% vs 62.3%) compared to IND‐Cy7‐TCF, due to the fine‐tuning of hydrogen bonding and intermolecular π–π interactions to form loose molecular stacks. Interestingly, the unique molecular stacking structure provides a binding site and catalytic center for H2O2 that exhibits catalase‐like activity, which can further ameliorate the efficiency of PDT and enhance the synergistic effect of PDT/PTT phototherapy in vitro and in vivo. This study can provide a simple but effective supramolecular strategy to design small molecule PSs with desirable aggregated structure for synergistic dual‐mode phototherapy.

Molecular Docking Study of the Interactions Between Cyanine Dyes And DNA

Among the various fluorescent probes currently used for biomedical and biochemical studies, significant attention attracts cyanine dyes possessing advantageous properties upon their complexation with biomolecules, particularly nucleic acids. Given the wide range of cyanine applications in DNA studies, a better understanding of their binding mode and intermolecular interactions governing dye-DNA complexation would facilitate the synthesis of new molecular probes of the cyanine family with optimized properties and would be led to the development of new cyanine-based strategies for nucleic acid detection and characterization. In the present study molecular docking techniques have been employed to evaluate the mode of interaction between one representative of monomethines (AK12-17), three trimethines (AK3-1, AK3-3, AK3-5), three pentamethines (AK5-1, AK5-3, AK5-9) and one heptamethine (AK7-6) cyanine dyes and B–DNA dodecamer d(CGCGAATTCGCG)2 (PDB ID: 1BNA). The molecular docking studies indicate that: i) all cyanines under study (excepting AK5-9 and AK7-6) form the most stable dye-DNA complexes with the minor groove of double-stranded DNA; ii) cyanines AK5-9 and AK7-6 interact with the major groove of the DNA on the basis of their more extended structure and higher lipophilicity in comparison with other dyes; iii) cyanine dye binding is governed by the hydrophobic and Van der Waals interactions presumably with the nucleotide residues C9A, G10A (excepts AK3-1, AK3-5), A17B (excepts AK3-5, AK5-3) and A18B in the minor groove and the major groove residues С16B, A17B, A18B, C3A, G4A, A5A, A6A (AK5-9 and AK7-6); iv) all dyes under study (except AK3-1, AK3-5 and AK5-39 possess an affinity to adenine and cytosine residues, whereas AK3-1, AK3-5 and AK5-3 also interact with thymine residues of the double-stranded DNA.

Tailoring albumin-based theranostic PROTACs nanoparticles for enhanced NIR-II bioimaging and synergistic cancer chemo-phototherapy

PROteolysis TArgeting Chimeras (PROTACs), a developing therapeutic tool designed to dictate target proteins for proteolysis through hijacking the ubiquitin–proteasome system, show potential for cancer therapy. However, unfavorable solubility and poor permeability of traditional PROTACs lead to low bioavailability and insufficient tumor distribution, which limit their clinical applications. Herein, we report a tridentate molecular probe (PROTAC-Cy7) by a three-in-one molecular designing strategy, which integrated a warhead that binds to MCL-1, the E3 ligase ligand pomalidomide and a heptamethine cyanine linker connecting the warhead and the ligand into the same scaffold. Then, bovine serum albumin (BSA) nanoparticles (NPs) with excellent biocompatibility, nonantigenic and biosafety were utilized to manufacture water-insoluble PROTAC-Cy7. The prepared PROTAC-Cy7@BSA NPs demonstrated tumor targeting and efficient degradation of MCL-1 through specific binding to MCL-1 receptors, which are overexpressed in multiple tumors. Moreover, PROTAC-Cy7@BSA NPs can be successfully used for near-infrared-II (NIR-II) noninvasively biomedical vascular imaging and to perform tumor resection guided by intraoperative real-time imaging. Under 808 nm laser irradiation, PROTAC-Cy7@BSA NPs exhibited synergistic Chemo-Phototherapy and showed perfect tumor suppression with 100% survival rate throughout the course of 60-day monitoring period. Our work provides a simple and feasible strategy for designing multifunctional drugs to have imaging-guided tumor-targeted multimodal therapy.

Doubly Strapped Zwitterionic NIR‐I and NIR‐II Heptamethine Cyanine Dyes for Bioconjugation and Fluorescence Imaging

AbstractHeptamethine cyanine dyes enable deep tissue fluorescence imaging in the near infrared (NIR) window. Small molecule conjugates of the benchmark dye ZW800‐1 have been tested in humans. However, long‐term imaging protocols using ZW800‐1 conjugates are limited by their instability, primarily because the chemically labile C4′‐O‐aryl linker is susceptible to cleavage by biological nucleophiles. Here, we report a modular synthetic method that produces novel doubly strapped zwitterionic heptamethine cyanine dyes, including a structural analogue of ZW800‐1, with greatly enhanced dye stability. NIR‐I and NIR‐II versions of these doubly strapped dyes can be conjugated to proteins, including monoclonal antibodies, without causing undesired fluorophore degradation or dye stacking on the protein surface. The fluorescent antibody conjugates show excellent tumor‐targeting specificity in a xenograft mouse tumor model. The enhanced stability provided by doubly strapped molecular design will enable new classes of in vivo NIR fluorescence imaging experiments with possible translation to humans.

Doubly Strapped Zwitterionic NIR-I and NIR-II Heptamethine Cyanine Dyes for Bioconjugation and Fluorescence Imaging.

Heptamethine cyanine dyes enable deep tissue fluorescence imaging in the near infrared (NIR) window. Small molecule conjugates of the benchmark dye ZW800-1 have been tested in humans. However, long-term imaging protocols using ZW800-1 conjugates are limited by their instability, primarily because the chemically labile C4'-O-aryl linker is susceptible to cleavage by biological nucleophiles. Here, we report a modular synthetic method that produces novel doubly strapped zwitterionic heptamethine cyanine dyes, including a structural analogue of ZW800-1, with greatly enhanced dye stability. NIR-I and NIR-II versions of these doubly strapped dyes can be conjugated to proteins, including monoclonal antibodies, without causing undesired fluorophore degradation or dye stacking on the protein surface. The fluorescent antibody conjugates show excellent tumor-targeting specificity in a xenograft mouse tumor model. The enhanced stability provided by doubly strapped molecular design will enable new classes of in vivo NIR fluorescence imaging experiments with possible translation to humans.

Heptamethine Cyanine Dyes with Ultra‐Efficient Excited‐State Nonradiative Decay for Synergistic Photothermal Immunotherapy

AbstractOrganic dyes in the excited singlet state (S1) decay via intersystem crossing (ISC) to the triplet state, radiative dissipation as fluorescence, or nonradiative decay for thermal deactivation. Although many studies are conducted to improve ISC and fluorescence efficiency, few have optimized S1 decay via thermal deactivation, which is crucial for designing photothermal agents. A strategy for inhibiting radiative decay and ISC by introducing electron withdraw groups (EWGs) into the meso position of heptamethine cyanines (Cy7) is reported here, which allows S1 energy decay via nonradiative relaxation. The decrease in the electron density of Cy7 caused by EWGs improved the photostability, which is important for biological applications because conventional cyanine dyes are easily photobleached. The EWG substitutes acted as efficient rotation groups with low‐energy barriers, narrowing the energy gap between S1 and the ground state and considerably improving the photothermal conversion efficiency (PCE). The PCE of CF3cy with the strongest EWG is increased up to 83%. Liposome is used as a carrier to improve the biocompatibility and tumor retention of CF3cy, which is combined with the toll‐like receptor agonist resiquimod (R848) for synergistic photothermal immunotherapy against both primary and distant tumors and elicits a long‐lasting immunological memory effect.