Antiquenching Macromolecular NIR-II Probes with High-Contrast Brightness for Imaging-Guided Photothermal Therapy under 1064 nm Irradiation

Simply Designed and Universal DNA Nanohydrogel for Stimuli-Responsive NIR-II Fluorescence Imaging of Early-Stage Tumor

The delayed detection and recurrence of cancer lead to disappointing cure rates, underscoring the imperative for exploring precise early tumor diagnosis techniques. Despite the superior biocompatibility and flexible programmability of DNA nanoprobes for tumor imaging, intricate designs with multiple oligonucleotide sequences are always indispensable, which significantly hinder their clinical application and commercial development. To construct a simply designed DNA nanoprobe, here, we constructed a universal stimuli-responsive nanohydrogel through the hybridization of the staple strand and skeleton strand. Through a simple substitution of the staple strand, this hydrogel can be adapted for the response to different targets without necessitating a series of subsequent revisions and synthesis optimization. To achieve near-infrared II region (NIR-II) fluorescence imaging, alkynyl-modified NIR-II fluorescent dyes are labeled at two ends of bent staple strands and display weak fluorescence because of the aggregation-caused quenching effect. The highly expressed ATP or cytokine in tumor cells activates the liberation of staples and collapse of the bent configuration, which generates fluorescence recovery for tumor imaging. Moreover, this nanohydrogel also allows for the targeted release of anticancer drugs intercalated in the DNA helix. By integration of NIR-II fluorescent dyes, this versatile nanohydrogel enables precise diagnosis and treatment of early tumors. The straightforward design demonstrates low cost and easy adaptability for multitarget detection, highlighting its significant implications for the advancement of DNA nanotechnology in clinical application and commercialization production.

Spatially Controlled Co-Delivery of Diagnostic and Therapeutic Agents Using DNA Nanoframeworks for Pancreatic Cancer Precision Therapy

Theranostic platforms that integrate diagnostic and therapeutic functionalities offer promising strategies for precision medicine, particularly in the treatment of major diseases. However, the development of platforms capable of achieving spatially controlled detection and therapy at the lesion site remains a significant challenge. Herein, we present a dual-stimuli-responsive DNA nanoframework that achieve spatially controlled codelivery of molecular beacon (MB) and Cas9 ribonucleoprotein (RNP), enabling simultaneous specific optical detection and efficient gene therapy for pancreatic cancer. The DNA nanoframeworks are synthesized via precipitation polymerization, utilizing acrylamide-modified DNA to initiate a hybridization chain reaction that facilitates the effective loading of MB-extended and sgRNA-conjugated DNA hairpins. The Cas9 protein is efficiently loaded into the nanoframeworks through phase transition-induced polymer chain rearrangement, overcoming steric hindrance. Upon aptamer-mediated internalization into PANC-1 cells, the overexpressed apurinic/apyrimidinic endonuclease 1 and ribonuclease H in cancer cells induce site-specific cleave of MB and DNA-RNA hybrid duplex, respectively. This cleavage restores fluorescence for specific optical detection, whereas the released Cas9 RNP performs gene editing for efficient therapy. Low fluorescence background and favorable biocompatibility are observed in normal cells. In a pancreatic cancer mouse model, the platform demonstrates significant detection-guided antitumor efficacy, highlighting its potential for precision medicine in cancer therapy.

DNA-Based nanostructures for tumor microenvironment-responsive drug delivery

DNA nanostructures, with sequence programmability, biocompatibility, and structural versatility, have emerged as promising tools for biomedical applications, particularly in targeted drug delivery and therapeutic interventions. The tumor microenvironment (TME) is characterized by dysregulated pH gradients, elevated glutathione (GSH), hypoxia, adenosine triphosphate (ATP) abundance, and aberrant enzymatic activity, presenting significant challenges for conventional therapies. DNA-based nanostructure enables precise control over drug-loading efficiency, tumor-targeted specificity, and spatiotemporal release mechanisms, making them ideal for tumor-targeted drug delivery. In this review, we highlight recent advances in versatile TME-responsive DNA-based nanostructures for precise therapeutic drug delivery. First, we discuss the fundamental design principles governing the structural configuration and functional integration of DNA nanostructures in TME-responsive drug delivery. Next, we summarize the mechanisms by which TME characteristics, including pH gradients, glutathione (GSH), adenosine triphosphate (ATP), enzymatic activity, and multiple stimuli, regulate the targeting and controlled release of therapeutic payloads in DNA-based nanostructures. Finally, this review provides an outlook on future research directions aimed at further optimizing the designability of DNA nanostructure-based drug delivery systems, underscoring the necessity of interdisciplinary collaboration. It is expected that these principles facilitate the future development of next-generation DNA nanostructure-based drugs with smart, precise, safe, and potent therapeutic capabilities.

Exceptional Near-Infrared II Organic Small Molecule Nanoagent for Photoacoustic/Photothermal Imaging-Guided Highly Efficient Therapy in Cancer

Near-infrared II (NIR-II) photoacoustic (PA)/photothermal imaging-guided tumor therapy holds great promise in precision medicine for cancer treatment. This work reports on the synthesis and application of an organic small molecule nanoagent that has exceptional PA and photothermal properties in the near-infrared region. BCy-TPE was constructed by linking an NIR-II absorbing cyanine dye BCy-Cl with a twisted tetraphenylethene unit. The synthesized BCy-TPE exhibited an intense absorption peak at 1032 nm. After encapsulation into water-dispersible nanoparticles (NPs), BCy-TPE NPs exhibited two absorption peaks at 880 and 1046 nm. Notably, under 1064 nm laser excitation, BCy-TPE NPs deliver a remarkable photothermal conversion efficiency of 92%, together with superior biocompatibility, photostability, and PA/photothermal imaging capability. Moreover, after intravenous administration of BCy-TPE NPs into 4T1 tumor-bearing mice and treatment with safe-intensity (1.0 W cm-2 and 1064 nm) laser irradiation, tumor temperature increased rapidly to 52 °C within 1 min and tumors are completely ablated after a single photothermal therapy treatment. Overall, this work offers a novel strategy to develop superb NIR-II photothermal agents for PA/photothermal imaging-guided highly efficient therapy in cancer.

J-aggregates of strong electron-donating groups linked Aza-BODIPY adjusting by polypeptide for NIR-II phototheranostics

The commonly employed strategies for engineering second near-infrared (NIR-II) organic phototheranostic agents are based on expanding conjugated backbone length, strengthening donor (D)-acceptor (A) effect, or forming J-aggregates. We constructed the D-A-D' structure by incorporating strong electron-donating methoxy and tetraphenylethene (TPE) moieties on the electron-deficient Aza-BODIPY core, and simultaneously expanded the π-conjugation effect by introducing thiophene groups, to obtain a dye BDP-TPE. Next, the nanoparticles P-TPE were prepared via the assembly of BDP-TPE with amphiphilic polypeptides (mPEG2000-P(Asp)10), and successfully constructed the J-aggregates. The obtained P-TPE exhibited strong absorption and fluorescence with maxima at 808 and 1018 nm, respectively, with a conspicuous absolute quantum yield of 0.241 %. Moreover, P-TPE also showed excellent biocompatibility, and high photothermal conversion efficiency of 61.15 %, and excellent resistance to pH, long-term storage, and photobleaching. In vitro and in vivo experiments revealed that P-TPE exhibited good biocompatibility and effectively achieved NIR-II fluorescence imaging-guided PTT with complete tumor ablation under 808 nm laser irradiation. These results provided good evidence for the use of P-TPE as a NIR-II fluorescence imaging-guided PTT therapeutic agent in vivo.

J-aggregates of multi-groups cyanine dye for NIR-IIa fluorescence-guided mild photothermal therapy under 1064 nm irradiation

NIR-IIa fluorescence imaging (FI) and NIR-II photothermal therapy (PTT) have gained popularity due to the advantages of high temporal and spatial resolution and deep penetration. However, the hyperthermia (>48 °C) of conventional PTT with nonspecific warming and thermal diffusion may inevitably cause damage to healthy tissues or organs surrounding the tumor. Therefore, it is highly desirable to provide effective cancer treatment by implementing mild photothermal therapy (mPTT) at mild temperatures with lower laser power density. Here, the nanotheranostic platform FN@P-GA NPs with NIR-II absorption and NIR-IIa emission was developed by constructing J-aggregates. FN@P-GA possesses good biocompatibility, favorable NIR-IIa FI performance, decent stability, and high photothermal conversion efficiency (57.6 %), which lays a solid foundation for FI-guided mPTT. Due to its ability to effectively down-regulate the expression of HSP90 and reduce cellular thermoresistance to kill cancer cells, FN@P-GA successfully achieved NIR-IIa FI-guided mPTT and demonstrated its potent anti-tumor effect under 1064 nm laser irradiation at mild temperature and low power density (0.3 W/cm2).

Synthesis on NIR-II Multifunctional Imaging and Photothermal Therapy of a Novel Water-Soluble Molecule

The synthesis of water-soluble symmetric molecules with donor-acceptor-donor (D-A-D) structure is reported. The compound is connected by π bridge with 2-bromofluorene external polyethylene glycol 2000 as the shielding unit, and donor component and pyrrolopyrrole (DPP) as the acceptor unit. The D-A-D double donor fluorescent molecule P2-DPP is obtained by coupling reaction. The absorption peak and emission peak of the fluorescent molecule P2-DPP are 600 and 1020 nm, respectively. It has potential excellent imaging characteristics. It does not need to use nanoparticles formed by the DSPE-MPEG amphiphilic block to form micelles. The quantum yield reaches 0.6% and the penetration depth can reach 10 mm. The chemical is capable of achieving liver and renal metabolism. It has a good application prospect in the photothermal therapy of mouse tumors and realizes the integration of biological diagnosis and treatment.

Counterion influence on near-infrared-II heptamethine cyanine salts for photothermal therapy

Photothermal therapy (PTT) has attracted extensive attention in cancer treatment. Heptamethine cyanine dyes with near-infrared (NIR) absorption performance have been investigated for PTT. However, they are often accompanied by poor photostability, suboptimal photothermal conversion and limited therapeutic efficacy. The photophysical properties of fluorescent organic salts can be tuned through counterion pairing. However, whether the counterion can influence the photostability and photothermal properties of heptamethine cyanine salts has not been clarified. In this work, we investigated the effects of eleven counter anions on the physical and photothermal properties of NIR-II heptamethine cyanine salts with the same heptamethine cyanine cation. The anions have great impacts on the physiochemical properties of dyes in solution including aggregation, photostability and photothermal conversion efficiency. The physical tuning enables the control over the cytotoxicity and phototoxicity of the dyes. The selected salts have been demonstrated to significantly suppress 4T1 breast tumor growth with low toxicity. The findings that the counterion has great effects on the photothermal properties of cationic NIR-II heptamethine cyanine dyes will provide a reference for the preparation of improved photothermal agents through counterion pairing with possible translation to humans.

Recent advances in fluorescence imaging-guided photothermal therapy and photodynamic therapy for cancer: From near-infrared-I to near-infrared-II

Phototherapy (including photothermal therapy, PTT; and photodynamic therapy, PDT) has been widely used for cancer treatment, but conventional PTT/PDT show limited therapeutic effects due to the lack of disease recognition ability. The integration of fluorescence imaging with PTT/PDT can reveal tumor locations in a real-time manner, holding great potential in early diagnosis and precision treatment of cancers. However, the traditional fluorescence imaging in the visible and near-infrared-I regions (VIS/NIR-I, 400-900 nm) might be interfered by the scattering and autofluorescence from tissues, leading to a low imaging resolution and high false positive rate. The deeper near-infrared-II (NIR-II, 1000-1700 nm) fluorescence imaging can address these interferences. Combining NIR-II fluorescence imaging with PTT/PDT can significantly improve the accuracy of tumor theranostics and minimize damages to normal tissues. This review summarized recent advances in tumor PTT/PDT and NIR-II fluorophores, especially discussed achievements, challenges and prospects around NIR-II fluorescence imaging-guided PTT/PDT for cancers.

A Gas/phototheranostic Nanocomposite Integrates NIR-II-Peak Absorbing Aza-BODIPY with Thermal-Sensitive Nitric Oxide Donor for Atraumatic Osteosarcoma Therapy

Photothermal therapy (PTT) has received increasing interest in cancer therapeutics owing to its excellent efficacy and controllability. However, there are two major limitations in PTT applications, which are the tissue penetration depth of lasers within the absorption range of photothermal agents and the unavoidable tissue empyrosis induced by high-energy lasers. Herein, a gas/phototheranostic nanocomposite (NA1020-NO@PLX) is engineered that integrates the second near-infrared-peak (NIR-II-peak) absorbing aza-boron-dipyrromethenes (aza-BODIPY,NA1020) with the thermal-sensitive nitric oxide (NO) donor (S-nitroso-N-acetylpenicillamine, SNAP). An enhanced intramolecular charge transfer mechanism is proposed to achieve the NIR-II-peak absorbance (λmax = 1020 nm) on NA1020, thereby obtaining its deep tissue penetration depth. The NA1020 exhibits a remarkable photothermal conversion, making it feasible for the deep-tissue orthotopic osteosarcoma therapy and providing favorable NIR-II emission to precisely pinpoint the tumor for a visible PTT process. The simultaneously investigated atraumatic therapeutic process with an enhanced cell apoptosis mechanism indicates the feasibility of the synergistic NO/low-temperature PTT for osteosarcoma. Herein, this gas/phototheranostic strategy optimizes the existing PTT to present a repeatable and atraumatic photothermal therapeutic process for deep-tissue tumors, validating its potential clinical applications.

Antiaggregation of NIR-II Probe Regulated by Amphiphilic Polypeptide with High Contrast Brightness for Phototheranostics and Vascular Microscopic Imaging under 1064 nm Irradiation

Thanks to deep penetration and high resolution, the second near-infrared window (NIR-II, 1000-1700 nm) fluorescence (FL) imaging is expected to gain favor in clinical applications, including macroscopic imaging for cancer diagnosis and microangiography for vascular-related disease diagnosis. Nevertheless, most NIR-II fluorescent probes, especially cyanine, are highly susceptible to self-quenching in the aggregated state, which severely limits their application in bioimaging. Here, the Br-modified cyanine dye F4 -Br and the amphiphilic polypeptide poly(oligo[ethylene glycol]methacrylate)-b-poly(benzyl-L-aspartic acid) (POEGMA-PBLA) are synthesized. By modulating the self-assembly of F4 -Br and POEGMA-PBLA to effectively inhibit the H-aggregation of F4 -Br in aqueous solutions, nanoprobe F4 -Br@P17 with outstanding antiquenching capability is developed. This prominent feature allows it to perform vascular microscopic imaging with high spatiotemporal resolution and assess hemodynamic characteristics. F4 -Br@P17 nanoparticles (NPs) with good stability and satisfactory biocompatibility also enable high contrast brightness for NIR-II FL imaging of tumors. Given the efficient enrichment at tumor sites and the promising photothermal conversion efficiency (43.5%), F4 -Br@P17 NPs successfully conduct photothermal therapy and exhibit superior antitumor efficiency under 1064 nm laser irradiation. These remarkable performances reveal the tremendous possibility of F4 -Br@P17 NPs for in vivo microscopic imaging and FL imaging-guided photothermal therapy in the NIR-II region.

Biodegradable FePS3 nanoplatform for efficient treatment of osteosarcoma by combination of gene and NIR-II photothermal therapy

As a common tumor with high incidence, osteosarcoma possesses extremely poor prognosis and high mortality. Improving the survival of osteosarcoma patients is still a great challenge due to the precipice of advancement in treatment. In this study, a combination strategy of gene therapy and photothermal therapy (PTT) is developed for efficient treatment of osteosarcoma. Two-dimensional (2D) FePS₃ nanosheets are synthesized and functionalized by poly-L-lysine-PEG-folic acid (PPF) to fabricate a multifunctional nanoplatform (FePS@PPF) for further loading microRNAs inhibitor, miR-19a inhibitor (anti-miR-19a). The photothermal conversion efficiency of FePS@PPF is up to 47.1% under irradiation by 1064 nm laser. In vitro study shows that anti-miR-19a can be efficiently internalized into osteosarcoma cells through the protection and delivery of FePS@PPF nanaocarrier, which induces up-regulation of PTEN protein and down-regulation p-AKT protein. After intravenous injection, the FePS@PPF nanoplatform specifically accumulates to tumor site of osteosarcoma-bearing mice. The in vitro and in vivo investigations reveal that the combined PTT-gene therapy displays most significant tumor ablation compared with monotherapy. More importantly, the good biodegradability promotes FePS@PPF to be cleared from body avoiding potential toxicity of long-term retention. Our work not only develops a combined strategy of NIR-II PTT and gene therapy mediated by anti-miR-19a/FePS@PPF but also provides insights into the design and applications of other nanotherapeutic platforms.

Acceptor Engineering Produces Ultrafast Nonradiative Decay in NIR-II Aza-BODIPY Nanoparticles for Efficient Osteosarcoma Photothermal Therapy via Concurrent Apoptosis and Pyroptosis

Small-molecule photothermal agents (PTAs) with intense second near-infrared (NIR-II, 1,000 to 1,700 nm) absorption and high photothermal conversion efficiencies (PCEs) are promising candidates for treating deep-seated tumors such as osteosarcoma. To date, the development of small-molecule NIR-II PTAs has largely relied on fabricating donor-acceptor-donor (D-A-D/D') structures and limited success has been achieved. Herein, through acceptor engineering, a donor-acceptor-acceptor (D-A-A')-structured NIR-II aza-boron-dipyrromethene (aza-BODIPY) PTA (SW8) was readily developed for the 1,064-nm laser-mediated phototheranostic treatment of osteosarcoma. Changing the donor groups to acceptor groups produced remarkable red-shifts of absorption maximums from first near-infrared (NIR-I) regions (~808 nm) to NIR-II ones (~1,064 nm) for aza-BODIPYs (SW1 to SW8). Furthermore, SW8 self-assembled into nanoparticles (SW8@NPs) with intense NIR-II absorption and an ultrahigh PCE (75%, 1,064 nm). This ultrahigh PCE primarily originated from an additional nonradiative decay pathway, which showed a 100-fold enhanced decay rate compared to that shown by conventional pathways such as internal conversion and vibrational relaxation. Eventually, SW8@NPs performed highly efficient 1,064-nm laser-mediated NIR-II photothermal therapy of osteosarcoma via concurrent apoptosis and pyroptosis. This work not only illustrates a remote approach for treating deep-seated tumors with high spatiotemporal control but also provides a new strategy for building high-performance small-molecule NIR-II PTAs.

Increasing Molecular Planarity through Donor/Side-Chain Engineering for Improved NIR-IIa Fluorescence Imaging and NIR-II Photothermal Therapy under 1064 nm

Developing conjugated small molecules (CSM) with intense NIR-II (1000-1700 nm) absorption for phototheranostic is highly desirable but remains a tremendous challenge due to a lack of reliable design guidelines. This study reports a high-performance NIR-II CSM for phototheranostic by tailoring molecular planarity. A series of CSM show bathochromic absorption extended to the NIR-II region upon the increasing thiophene number, but an excessive number of thiophene results in decreased NIR-IIa (1300-1400 nm) brightness and photothermal effects. Further introduction of terminal nonconjugated alkyl chain can enhance NIR-II absorption coefficient, NIR-IIa brightness, and photothermal effects. Mechanism studies ascribe this overall enhancement to molecular planarity stemming from the collective contribution of donor/side-chain engineering. This finding directs the design of NIR-II CSM by rational manipulating molecular planarity to perform 1064 nm mediated phototheranostic at high efficiency.

Incorporation of Robust NIR-II Fluorescence Brightness and Photothermal Performance in a Single Large π-Conjugated Molecule for Phototheranostics

Second near-infrared (NIR-II, 1000-1700 nm) window fluorescence imaging-guided photothermal therapy probes are promising for precise cancer phototheranostics. However, most of the currently reported probes do not demonstrate high NIR-II fluorescent brightness (molar absorption coefficient (ε) × quantum yield (QY)) and photothermal performance (ε × photothermal conversion efficiency (PCE)) in a single molecule. Herein, a versatile strategy to solve this challenge is reported by fabricating a large π-conjugated molecule (BNDI-Me) with a rigid molecular skeleton and flexible side groups. The proposed BNDI-Me nanoprobe boosts the ε and simultaneously optimizes its QY and PCE. Therefore, high NIR-II fluorescent brightness (ε × QY = 2296 m^-1 cm^-1 ) and strong photothermal performance (ε × PCE = 82 000) are successfully incorporated in a single small molecule, and, to the best of knowledge, either of these two parameters is better than the best currently available fluorescent or photothermal probes. Thus, superior NIR-II imaging effect in vivo and high photothermal tumor inhibition rate (81.2%) at low systemic injection doses are obtained. The work provides further insights into the relationship of photophysical mechanisms and structures, and presents promising molecular design guidelines for the integration of more efficient multiple theranostic functions in a single molecule.

J-aggregates of Br- and piperazine-modified cyanine dye with the assistance of amphiphilic polypeptides for efficient NIR-IIa phototheranostics under 1064 nm irradiation

The second near-infrared IIa window (NIR-IIa, 1300nm∼1400nm) enables high-resolution imaging and deep-tissue tumor treatment due to its unique low tissue scattering and autofluorescence, high temporal-spatial resolution, and deep tissue penetration. Therefore, NIR-IIa fluorescence imaging-guided phototherapy is of specific interest. However, organic dyes and their nanoparticles for NIR-IIa phototheranostics are still scarce. Here, we have synthesized a Br- and piperazine-modified cyanine dye (FN) and its nanomicelles encapsulated by an amphiphilic polypeptide with sidechains of tertiary amine (PEA). The J-aggregates of P@FN₉ with 1116 nm absorption and efficient NIR-IIa fluorescence emission were formed by the self-assembly of FN and PEA. P@FN₉ nanoparticles (NPs) showed good stability and high photothermal conversion efficiency (55.4%). In addition, the high spatial resolution and signal-to-background ratio (SBR) of P@FN₉ were demonstrated by NIR-IIa fluorescence imaging of mouse vasculature. The P@FN₉ NPs successfully performed the NIR-IIa fluorescence imaging-guided photothermal therapy, and both in vitro and in vivo experiments indicated that the P@FN₉ NPs exhibited effective antitumor effects under the NIR-II (1064 nm) laser irradiation. STATEMENT OF SIGNIFICANCE.

Phosphotungstate Acid Doped Polyanilines Nanorods for in situ NIR-II Photothermal Therapy of Orthotopic Hepatocellular Carcinoma in Rabbit

INTRODUCTION

Second near-infrared photothermal therapy (NIR-II PTT) has become a promising strategy for treating cancer in terms of safety and potency. However, the application of NIR-II PTT was limited in the treatment of deep-buried solid tumors due to the low dose of NIR-II absorption nanomaterials and the inadequate laser energy in the deep tumor.

METHODS

Herein, the authors report the engineering of NIR-II absorbing polyaniline nanorods, termed HPW@PANI Nanorods, for in situ NIR-II PTT based on optical fibers transmission of laser power and transarterial infusion for the treatment of orthotopic hepatocellular carcinoma in the rabbit. HPW@PANI Nanorods were prepared via chemical oxidant polymerization of aniline under phosphotungstic acid, which exhibited effective NIR-II absorption for hyperthermia ablation cells.

RESULTS

HPW@PANI Nanorods were fast and efficiently deposited into primary orthotopic transplantation VX2 tumor in rabbits via transarterial infusion. Furthermore, an optical fiber was interventionally inserted into the primary VX2 tumor to transmit 1064nm laser energy for in situ NIR-II PTT, which could ablate primary tumor, inhibit distant tumor, and suppress peritoneal metastasis.

CONCLUSION

This study provides new insights into the application of in situ NIR-II PTT based on optical fibers transmission of laser power and transarterial injection of NIR-II absorption nanomaterials to treat deep-buried tumors.

Synthesis of strong electron donating-accepting type organic fluorophore and its polypeptide nanoparticles for NIR-II phototheranostics

A novel NIR-II small-molecule D-A type organic fluorophore conjugation of triphenylamine, thiophene, and benzo[c,d] indol groups (TPA-Et) with strong electron-donating and accepting groups has been synthesized. The dye shows a significant Stokes shift for efficient fluorescence in the NIR-II region and high photothermal performance. The TPA-Et was then encapsulated by an amphiphilic copolymer P(OEGMA)₂₀-P(Asp)₁₄, and micelles (P@TP) has been prepared with outstanding NIR-II imaging performance, excellent photothermal conversion efficiency (52.5%) under 808 nm laser irradiation, and good photostability. Fluorescence imaging experiments have consistently shown that P@TP can image tiny blood vessels in mice, enrich effectively in the tumor region, and maintain a relatively stable NIR-II fluorescence signal in the tumor area for a long time up to 60 h. In vivo photothermal therapy has a highly significant anticancer effect without tumor recurrence, demonstrating the apparent advantages of P@TP as a NIR nanotheranostic platform in NIR-II imaging-guided photothermal therapy.

Synthesis and bioimaging of a BODIPY-based fluorescence quenching probe for Fe3

Iron is the main substance for maintaining life. Real-time determination of ferric ion (Fe3+) in living cells is of great significance for understanding the relationship of Fe3+ concentration changes with various physiological and pathological processes. Fluorescent probes are suitable for the detection of trace metal ions in cells due to their low toxicity and high sensitivity. In this work, a boron-dipyrromethene-based fluorescent probe (BODIPY-CL) for selective detection of Fe3+ was synthesized. The fluorescence emission of BODIPY-CL was determined at 516 nm. In a pH range of 1 to 10, the probe BODIPY-CL exhibits a quenching response to Fe3+. Meanwhile, BODIPY-CL showed a highly selective response to Fe3+ compared with 16 kinds of metal ions. The stoichiometry ratio of BODIPY-CL bound to Fe3+ was nearly 2 : 1. The fluorescence quenching response obtained by the sensor was linear with the Fe3+ concentration in the range of 0-400 μM, and the detection limit was 2.9 μM. BODIPY-CL was successfully applied to image Fe3+ in cells. This study provides a promising fluorescent imaging probe for further research on the physiological and pathological effects of Fe3+.

An aza-BODIPY-based NIR-II luminogen enables efficient phototheranostics

The fabrication of a high-performance second near-infrared (NIR-II) biological window fluorophore is in urgent need for precise diagnosis and treatment of cancer. Nevertheless, the construction of phototherapeutic agents in the NIR-II region with excellent imaging performance and minimal side effects remains a big challenge due to the limited availability of core fluorophore candidates. In this study, a new NIR-II fluorescent probe, CB1, which is an aza-BODIPY core conjugated with bulky donors, was designed and synthesized. CB1 was further encapsulated in DSPE-PEG2000 to impart water solubility, which shows brighter NIR-II fluorescence and higher photostability than the clinically used indocyanine green (ICG). CB1 nanoparticles show deep tissue penetration and high imaging contrast in vivo. In addition, molecular conformation enables CB1 nanoparticles to exhibit good photothermal properties. Both in vitro and in vivo assessments confirm that CB1 nanoparticles could be utilized as distinguished theranostic agents for NIR-II fluorescence imaging and tumor growth inhibition with negligible side effects. Collectively, this work provides a promising approach for constructing a new platform for cancer diagnosis and therapy.

In situ formation of J-aggregate in the tumor microenvironment using acidity responsive polypeptide nanoparticle encapsulating galactose-conjugated BODIPY dye for NIR-II phototheranostics

Through the activation of packing arrangements of dyes to modulate their photophysical and/or photochemical properties, not only new NIR-II dyes but tumor-specific NIR-II imaging and therapy can also be achieved. Herein, we designed an acid-responsive polypeptide nanoparticle (P-ipr@Gal) encapsulated with a pH-sensitive amphiphilic polypeptide (P-ipr) as a carrier for the galactose-conjugated BODIPY (Gal-BDP) dye. When P-ipr@Gal NPs are enriched in tumor regions by the EPR effect, the acidic microenvironment (pH 6.4-6.8) promotes the disintegration of P-ipr@Gal nanomicelles and the release of sufficient Gal-BDP. The protonation of the julolidine nitrogen of the Gal-BDP dye switched on the molecular stacking transformation from the H-aggregate to J-aggregate. The J-aggregate significantly enhanced the redshift absorption and emission intensity, which enhanced the fluorescence brightness and photothermal therapeutic effect in the tumor region. We also prepared J-aggregates PAsp@Gal with non-acidic responsive polyaspartic acid benzyl esters (PAsp) encapsulated Gal-BDP, which remained "always-on" with J-aggregate characteristics. The P-ipr@Gal (or PAsp@Gal) J-aggregate has a maximum emission peak redshifted to nearly 1064 nm, with a 3.5-fold increase in the emission intensity compared to the H-aggregate at pH 7.4. Based on the effective accumulation of tumor sites and considerable PCE (>40%), P-ipr@Gal nanoparticles have a lower background and higher tumor background ratio, which makes them a potential NIR-II imaging-guided photothermal therapy agents.

Counterion-Paired Bright Heptamethine Fluorophores with NIR-II Excitation and Emission Enable Multiplexed Biomedical Imaging

Photon excitation and emission at the NIR-II spectral window enable high-contrast deep-tissue bioimaging. However, multiplexed imaging with NIR-II excitation and emission has been hampered by the limited chemical strategies to develop bright fluorophores with tunable absorption in this spectral regime. Herein, we developed a series of heptamethine cyanines (HCs) with varied absorption/emission maxima spanning from 1100 to 1600 nm through a physical organic approach. A bulky counterion paired to HCs was found to elicit substantial improvements in absorptivity (7-fold), brightness (14-fold), and spectral profiles in water, addressing a notorious quenching problem of NIR-II cyanines due to aggregation and polarization. We demonstrated the utilities of HC1222 and HC1342 for high-contrast dual-color imaging of circulatory system, lymphatic structures, tumor, and organ function in living mice under 1120 nm and 1319 nm excitation, showing HCs as a promising platform for non-invasive bioimaging.

Recent Progress of Cyanine Fluorophores for NIR-II Sensing and Imaging

The cyanine fluorophores, a kind of classic organic fluorophores, are famous for their high extinction coefficient, simple synthetic route, and relatively long absorption and emission wavelengths. Moreover, the excellent biocompatibility and low toxicity in biological samples make cyanine fluorophores show excellent application value in the biomedical field, especially in Near-Infrared II (NIR-II) sensing and imaging. In this review, we briefly outline the history, characteristics, and current state of development of cyanine fluorophores. In particular, we described the application of cyanine fluorophores in NIR-II sensing and imaging. We hope this review can help researchers grab the latest information in the fast-growing field of cyanine fluorophores for NIR-II sensing and imaging.

Surface-Charge-Switchable and Size-Transformable Thermosensitive Nanocomposites for Chemo-Photothermal Eradication of Bacterial Biofilms in Vitro and in Vivo

The appearance of multidrug-resistant bacteria and their biofilms presents a serious threat to modern medical systems. Herein, we fabricated a novel gold-nanorod-based chemo-photothermal-integrated antimicrobial platform with surface-charge-switchable and near-infrared (NIR)-induced size-transformable activities that show an enhanced killing efficiency against methicillin-resistant Staphylococcus aureus (MRSA) in both planktonic and biofilm phenotypes. The nanocomposites are prepared by in situ copolymerization using N-isopropyl acrylamide (NIPAM), acrylic acid (AA), and N-allylmethylamine (MAA) as monomers on the surfaces of gold nanorods (GNRs). Ciprofloxacin (CIP) is loaded onto polymer shells of nanocomposites with a loading content of 9.8%. The negatively charged nanocomposites switch to positive upon passive accumulation at the infectious sites, which promotes deep biofilm penetration and bacterial adhesion of the nanoparticles. Subsequently, NIR irradiation triggers the nanocomposites to rapidly shrink in volume, further increasing the depth of biofilm penetration. The NIR-triggered, ultrafast volume shrinkage causes an instant release of CIP on the bacterial surface, realizing the synergistic benefits of chemo-photothermal therapy. Both in vitro and in vivo evidence demonstrate that drug-loaded nanocomposites could eradicate clinical MRSA biofilms. Taken together, the multifunctional chemo-photothermal-integrated antimicrobial platform, as designed, is a promising antimicrobial agent against MRSA infections.