Surfactant-Stripped Micelles of Near Infrared Dye and Paclitaxel for Photoacoustic Imaging Guided Photothermal-Chemotherapy

Supramolecular dye nanoassemblies for advanced diagnostics and therapies

Dyes have conventionally been used in medicine for staining cells, tissues, and organelles. Since these compounds are also known as photosensitizers (PSs) which exhibit photoresponsivity upon photon illumination, there is a high desire towards formulating these molecules into nanoparticles (NPs) to achieve improved delivery efficiency and enhanced stability for novel imaging and therapeutic applications. Furthermore, it has been shown that some of the photophysical properties of these molecules can be altered upon NP formation thereby playing a major role in the outcome of their application. In this review, we primarily focus on introducing dye categories, their formulation strategies and how these strategies affect their photophysical properties in the context of photothermal and non-photothermal applications. More specifically, the most recent progress showing the potential of dye supramolecular assemblies in modalities such as photoacoustic and fluorescence imaging, photothermal and photodynamic therapies as well as their employment in photoablation as a novel modality will be outlined. Aside from their photophysical activity, we delve shortly into the emerging application of dyes as drug stabilizing agents where these molecules are used together with aggregator molecules to form stable nanoparticles.

Aggregation-enhanced photothermal therapy of organic dyes

Photothermal therapy (PTT) represents a groundbreaking approach to targeted disease treatment by harnessing the conversion of light into heat. The efficacy of PTT heavily relies on the capabilities of photothermal agents (PTAs). Among PTAs, those based on organic dyes exhibit notable characteristics such as adjustable light absorption wavelengths, high extinction coefficients, and high compatibility in biological systems. However, a challenge associated with organic dye-based PTAs lies in their efficiency in converting light into heat while maintaining stability. Manipulating dye aggregation is a key aspect in modulating non-radiative decay pathways, aiming to augment heat generation. This review delves into various strategies aimed at improving photothermal performance through constructing aggregation. These strategies including protecting dyes from photodegradation, inhibiting non-photothermal pathways, maintaining space within molecular aggregates, and introducing intermolecular photophysical processes. Overall, this review highlights the precision-driven assembly of organic dyes as a promising frontier in enhancing PTT-related applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Cucurbit[8]uril-based water-dispersible assemblies with enhanced optoacoustic performance for multispectral optoacoustic imaging

Organic small-molecule contrast agents have attracted considerable attention in the field of multispectral optoacoustic imaging, but their weak optoacoustic performance resulted from relatively low extinction coefficient and poor water solubility restrains their widespread applications. Herein, we address these limitations by constructing supramolecular assemblies based on cucurbit[8]uril (CB[8]). Two dixanthene-based chromophores (DXP and DXBTZ) are synthesized as the model guest compounds, and then included in CB[8] to prepare host-guest complexes. The obtained DXP-CB[8] and DXBTZ-CB[8] display red-shifted and increased absorption as well as decreased fluorescence, thereby leading to a substantial enhancement in optoacoustic performance. Biological application potential of DXBTZ-CB[8] is investigated after co-assembly with chondroitin sulfate A (CSA). Benefiting from the excellent optoacoustic property of DXBTZ-CB[8] and the CD44-targeting feature of CSA, the formulated DXBTZ-CB[8]/CSA can effectively detect and diagnose subcutaneous tumors, orthotopic bladder tumors, lymphatic metastasis of tumors and ischemia/reperfusion-induced acute kidney injury in mouse models with multispectral optoacoustic imaging.

Hybridization of triphenylamine to BODIPY dyes at the 3,5,8-positions: A facile strategy to construct near infra-red aggregation-induced emission luminogens with intramolecular charge transfer for cellular imaging

A series of five BODIPY derivatives with triarylamine (TPA) moieties on their 3-, 5-, or 8-positions were reported, which showed wide-range fluorescence emissions across red and near infrared regions in their aggregation states. The influences of numbers and substituted positions of TPA groups on the optical and aggregation-induced emission (AIE) properties of these BODIPYs as well as organelle-specific imaging in live cells were investigated. The TPA groups installed at 3-/5-positions of BODIPY could effectively enlarge the conjugated system and red-shift the absorption and emission bands (λ_em^max up to 815 nm). In contrast, the TPA group linked to 8-position of BODIPY core has little contribution to decrease the HOMO-LUMO energy gap. Importantly, regardless the substitution positions of TPA groups, all these TPA-substituted BODIPYs (BTs) showed remarkable AIE performance and possessed high molar extinction absorption (up to ∼ 63000 M^-1 cm^-1), two-photon absorption (up to 171 GM at 870 nm), and large Stokes shifts. The BODIPY with one TPA group (BT1 and FBT1) showed lipid droplets-specific localization while BODIPY with two and three TPA groups (BT2, BT3 and FBT2) preferred to enrich in lysosomes. These BODIPYs all have been successfully used in tracking the dynamic behaviors of lipid droplets or lysosomes in living cells. Furthermore, BT1 and FBT1 can quantitatively detect the overexpression of lipid droplets, and BT3 has been successfully used to observe lysosomes behaviors of lipophagy process in living cells. This work systematically studied the influence of the number and position of TPA units on the optical properties and AIE-activities of BODIPYs, which not only enriched the BODIPY-based AIE NIR probes for organelle-specific imaging in live cells, but also provided a practical strategy for the effective construction of organic dyes with NIR AIE activity.

Recent advances in small molecule dye-based nanotheranostics for NIR-II photoacoustic imaging-guided cancer therapy

Photoacoustic (PA) imaging in the second near-infrared (NIR-II) window has gained more and more attention in recent years and showed great potential in the field of bioimaging. Until now, numerous materials have been developed as contrast agents for NIR-II PA imaging. Among them, small molecule dyes hold unique advantages such as definite structures and capability of fast clearance from body. By virtue of these advantages, small molecule dyes-constructed nanoparticles have relatively small size and show promise in the clinical translation. Thus, in this minireview, we summarize recent advances in small molecule dyes-based nanotheranostics for NIR-II PA imaging and cancer therapy. Studies about NIR-II PA imaging-guided phototherapy are first introduced. Then, NIR-II PA imaging-guided phototherapy-based combination therapeutic systems are reviewed. Finally, the conclusion and perspectives of this field are summarized and discussed.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

Spanning BODIPY fluorescence with self-assembled micellar clusters

BODIPY dyes possess favorable optical properties for a variety of applications including in vivo and in vitro diagnostics. However, their utilization might be limited by their water insolubility and incompatibility with chemical modifications, resulting in low aggregation stability. Here, we outline the route for addressing this issue. We have demonstrated two approaches, based on dye entrapment in micellar coordination clusters (MCCs); this provides a general solution for water solubility as well as aggregation stability of the seven BODIPY derivatives. These derivatives have various bulky aromatic substituents in the 2,3,5,6- and meso-positions and can rotate relative to a dipyrrin core, which also provides molecular rotor properties. The molecular structural features and the presence of aromatic groups allows BODIPY dyes to be used as "supporting molecules", thus promoting micelle-micelle interaction and micellar network stabilization. In the second approach, self-micellization, following BODIPY use, leads to MCC formation without the use of any mediators, including chelators and/or metal ions. In both approaches, BODIPY exhibits an excellent optical response, at a concentration beyond its solubilization limit in aqueous media and without undesired crystallization. The suggested approaches represent systems used to encapsulate BODIPY in a capsule-based surfactant environment, enabling one to track the aggregation of BODIPY; these approaches represent an alternative system to study and apply BODIPY's molecular rotor properties. The stabilized compounds, i.e., the BODIPY-loaded MCCs, provide a unique feature of permeability to hydrophilic ligand-switching proteins such as BSA; they exhibit a bright "turn-on" fluorescence signal within the clusters via macromolecular complexation, thus expanding the possibilities of water-soluble BODIPY-loaded MCCs utilization for functional indicators.

Engineering BODIPY-based near-infrared nanoparticles with large Stokes shifts and aggregation-induced emission characteristics for organelle specific bioimaging

Lipid droplets (LDs) and lysosomes, as two important subcellular organelles, play specific and indispensable roles in various cellular processes. The development of efficient LD- and lysosome-specific fluorescent bio-probes is of great importance. However, current commercial lipid droplet- (LD) and lysosome-specific fluorescent specific bio-probes often suffer from the aggregation-caused quenching (ACQ) effect, short absorption and emission wavelengths, poor photostability and low specificity. Herein, a typical ACQ luminogen BODIPY was directly conjugated to strong electron donating triarylamine units at its α-positions, giving near-infrared (NIR) fluorescent materials TPAB and 2TPAB with aggregation-induced emission (AIE). Both TPAB and 2TPAB nanoparticles were obtained by self-assembly, and showed NIR emissions, large Stokes shifts, good photostability and two-photon absorption. These nanoparticles presented remarkable bioimaging performances and were shown to specifically localize in LDs or lysosomes, respectively, depending on the number of triarylamine units attached. They have been successfully used to detect endogenous LD overproduction, and monitor abnormal activities of LDs/lysosomes, as well as real-time track the lipophagy process in cells. Their far NIR emission and two-photon excitation further supported their promising bioimaging application for lipid droplet tracking in liver tissue and live zebrafish larvae. Our work here enriches BODIPY based NIR AIE dyes and provides organelle specific bio-probes which are superior to currently used commercial ones.

NIR-responsive polydopamine-based calcium carbonate hybrid nanoparticles delivering artesunate for cancer chemo-photothermal therapy

Artesunate (AS), the first-line treatment of malaria with a satisfactory safety profile, has been repurposed as a potential anticancer candidate as it mainly generates reactive oxygen species (ROS) through its intrinsic endoperoxide bridge reacting with ferrous-based catalysts to suppress cancer cell growth. However, further clinical translation of AS is hindered by the attenuated anticancer efficacy due to insufficient ROS generation. Herein, we rationally integrated hydrophobic-modified AS (hAS) with biomimetic polydopamine (PDA) and biomineral calcium carbonate to fabricate high AS-loaded nanomedicine (Ca-PDA/hAS@PEG) for cancer chemo-photothermal therapy, which exerted anticancer effects in the following ways: (1) the heat was generated when PDA was irradiated by near-infrared (NIR) light for photothermal therapy. Meanwhile, the increased temperature accelerated the production of ROS from hAS, thus enhancing the anticancer efficacy of hAS-based chemotherapy; (2) hAS-mediated chemotherapy boosted the cancer inhibition effect of photothermal therapy by arousing the intracellular ROS levels in the presence of endogenous ferrous ions and sensitizing cancer cells to thermal ablation; (3) the integration of calcium carbonate into the nanoparticle facilitated the pH-responsive drug release for precise treatment. Such hybrid nanoparticles exhibited a combinational antitumor effect of photothermal therapy and chemotherapy in vivo with no systemic toxicity. Taken together, our work presents a facile strategy to improve the anticancer efficacy of AS by combining chemical modification and photothermal therapy-assisted endoperoxide bridge cleavage, which may offer opportunities to pave the way for clinical translation of AS-based nanomedicines. STATEMENT OF SIGNIFICANCE: The clinical translation of artesunate (AS) is hindered by the attenuated anticancer efficacy due to insufficient ROS generation. Herein, we rationally integrated hydrophobic-modified AS (hAS) with biomimetic polydopamine (PDA) and biomineral calcium carbonate to fabricate high AS-loaded nanomedicine (Ca-PDA/hAS@PEG) for improved cancer chemo-photothermal therapy. The heat generated from PDA in response to near-infrared light irradiation could locally ablate tumor as well as accelerate the production of ROS by hAS, thus enhancing the anticancer efficacy of hAS-based chemotherapy. On the other hand, hAS-based chemotherapy amplified the intracellular oxidative stress, sensitizing cancer cells to thermal ablation. Our work presents a facile strategy to improve the anticancer efficacy of AS by combining chemical modification and photothermal therapy-assisted endoperoxide bridge cleavage.

Co-delivery of NIR-II semiconducting polymer and pH-sensitive doxorubicin-conjugated prodrug for photothermal/chemotherapy

Semiconducting polymer (SP) is a promising photothermal agent in the antitumor application, but the co-delivery of the second near-infrared window (NIR-II)-based SPs with chemotherapeutic drug (e.g., doxorubicin (DOX)) remains a challenge. Here, SPs were firstly improved via backbone and alkyl side-chain engineering, and afterward, SPs and pH-sensitive prodrug copolymer self-assembled into a nanoparticle for a photoacoustic (PA)-imaging guided combination of photothermal therapy and chemotherapy. SP-encapsulated nanoparticles exhibited a high photothermal conversion efficiency of 45% at a relatively low power level of NIR irradiation (0.3 W/cm2 for 5 min). DOX was rapidly released in response to the acidic lysosomal environment. PA and fluorescence imaging confirmed that the photothermal therapy effectively drove DOX penetration inside tumor tissue, and it resulted in the killing of the surviving tumor cells from hyperthermia. The synergistic effect of SP-based photothermal therapy and DOX-induced chemotherapy was verified in vivo. Overall, the co-delivery of the SP and DOX using pH-sensitive nanoparticles represents a feasible strategy for photothermal therapy with potentially synergistic drug effects. STATEMENT OF SIGNIFICANCE: Recent years have yielded great progress in semiconducting polymers (SPs)-based photothermal therapy for anticancer treatment. However, studies about molecular weight and side-chain of SPs on photothermal conversion efficiency are limited, and investigation of controlled codelivery with chemotherapeutic drug is lacking. Here, we improved the SPs performance via backbone and side-chain engineering, and afterward offered a pH-sensitive DOX-conjugated amphiphilic copolymer to encapsulate SPs. SP-encapsulated nanoparticles exhibited high photothermal conversion efficiency at a clinically feasible power level of NIR irradiation. NIR irradiation-generated hyperthermia not only killed tumor cells but also promoted DOX penetration inside the tumor tissue to ablate the tumor cells that survived hyperthermia. The synergistic effect of SP-based photothermal therapy and DOX-induced chemotherapy was verified in vivo.

pH and Temperature Double-Switch Hybrid Micelles for Controllable Drug Release

pH/temperature dual-responsive hybrid micelles were prepared for constructing a double-locked drug delivery system. The temperature-sensitive polyethylene glycol-poly(tetrahydropyranylmethacrylate)-polyethylene glycol (PEG-PTHPMA-PEG) triblock copolymers were synthesized by reversible addition-fragmentation chain transfer polymerization and amide coupling reaction. pH-sensitive poly(2-(diisopropylamino ethylmethacrylate)-polyethylene glycol (PDPA-PEG) diblock polymers were introduced, which could self-assemble with PEG-PTHPMA-PEG in aqueous solutions to form hybrid micelles. The anticancer drug doxorubicin, which was encapsulated in the core of the hybrid micelles, could be released only under simultaneous stimulations of pH and temperature. It was proved that the micelles could maintain their structural stability under a unilateral stimulus, while the structure collapsed and recombined under a double stimulus, which triggered a large amount of drug release. Furthermore, the excellent biocompatibility and dual sensitivity of the vector were also proved by cytotoxicity experiments. The dual-responsive hybrid micelles designed here showed the advantages of a double insurance lock of drug leakage and precise controllability of drug release, which could act as accurate drug delivery systems.

Selenium Vacancy Engineering Using Bi2Se3 Nanodots for Boosting Highly Efficient Photonic Hyperthermia

Despite bismuth-based energy conversion nanomaterials having attracted extensive attention for nanomedicine, the nanomaterials suffer from major shortcomings including low tumor accumulation, long internal retention time, and undesirable photothermal conversion efficiency (PCE). To combat these challenges, bovine serum albumin and folic acid co-modified Bi2Se3 nanomedicine with rich selenium vacancies (abbreviated as VSe-BS) was fabricated for the second near-infrared (NIR-II) light-triggered photonic hyperthermia. More importantly, selenium vacancies on the crystal planes (0 1 5) and (0 1 11) of VSe-BS with similar formation energies could be distinctively observed via aberration-corrected scanning transmission electron microscopy images. The defect engineering endows VSe-BS with enhanced conductivity, making VSe-BS possess outstanding PCE (54.1%) in the NIR-II biowindow and desirable photoacoustic imaging performance. Tumor ablation studies indicate that VSe-BS possesses satisfactory therapeutic outcomes triggered by NIR-II light. These findings give rise to inspiration for further broadening the biological applications of defect engineering bismuth-based nanomaterials.

Thiophene-Fused BODIPY Dimers and Tetramers from Oxidative Aromatic Couplings as Near-Infrared Dyes

We describe a straightforward, postmodification synthesis for a family of thiophene-fused BODIPY dimers and tetramers through transforming flexible sulfur bridges into coplanar thiophene fusions. FeCl₃ was used as a bifunctional oxidant for both intramolecular and intermolecular oxidative aromatic coupling reactions. Oxidative fusion and dimerization gave strong red-shift absorptions from 509 nm for a BODIPY monomer to 830 nm for a tetramer.

Biocompatible nanomicelles for sensitive detection and photodynamic therapy of early-stage cancer

The lack of sensitive detection techniques and agents for early-stage tumors, which are characterized by small size, juvenile blood vessels and scarce secreted markers, has hampered timely cancer therapy and human well-being. Herein, the natural product pyropheophorbide-a (PPa) and FDA-approved Pluronic F127 are organized to develop F127-PPa nanomicelles with favorable size, red-shifted fluorescence and decent biocompatibility. After intravenous (i.v.) injection, the F127-PPa nanomicelles could not only accurately identify early-stage xenografted tumors, but also sensitively detect cancer metastasis in lungs through near-infrared (NIR) fluorescence imaging. The fluorescence signals are consistent with radionuclide imaging, photoacoustic (PA) imaging and bioluminescence imaging of tumors, consolidating the reliability of using F127-PPa nanomicelles for sensitive cancer diagnosis in a non-invasive and low-cost manner. Moreover, the fluorescence intensity of small tumors is linearly correlated with the tumoral mass ranging from 10 to 120 mg with a fluorescence coefficient of 4.5 × 10⁷ mg^-1. Under the guidance of multimodal imaging, the tumors could be thoroughly eradicated by F127-PPa under laser irradiation due to efficient reactive oxygen species (ROS) generation. These findings may provide clinically translatable agents and strategies for sensitive diagnosis of early-stage tumors and timely cancer therapy.

Targeted Micellar Phthalocyanine for Lymph Node Metastasis Homing and Photothermal Therapy in an Orthotopic Colorectal Tumor Model

Small-sized trastuzumab-targeted micelles (T-MP) were engineered using a surfactant-stripping approach that yielded concentrated phthalocyanines with strong near infrared absorption. T-MP accumulated more in the lymph node (LN) metastases of orthotopic colorectal cancer compared to the micelles conjugated with control IgG. Following surgical resection of the primary tumor, minimally invasive photothermal treatment of the metastatic LN with T-MP, but not the control micelles, extended mouse survival.

ABSTRACT

Tumor lymph node (LN) metastasis seriously affects the treatment prognosis. Studies have shown that nanoparticles with size of sub-50 nm can directly penetrate into LN metastases after intravenous administration. Here, we speculate through introducing targeting capacity, the nanoparticle accumulation in LN metastases would be further enhanced for improved local treatment such as photothermal therapy. Trastuzumab-targeted micelles (< 50 nm) were formulated using a unique surfactant-stripping approach that yielded concentrated phthalocyanines with strong near-infrared absorption. Targeted micellar phthalocyanine (T-MP) was an effective photothermal transducer and ablated HT-29 cells in vitro. A HER2-expressing colorectal cancer cell line (HT-29) was used to establish an orthotopic mouse model that developed metastatic disease in mesenteric sentinel LN. T-MP accumulated more in the LN metastases compared to the micelles conjugated with control IgG. Following surgical resection of the primary tumor, minimally invasive photothermal treatment of the metastatic LN with T-MP, but not the control micelles, extended mouse survival. Our findings demonstrate for the first time that targeted small-sized nanoparticles have potential to enable superior paradigms for dealing with LN metastases. [Image: see text]

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40820-021-00666-8.

Hyalase-Mediated Cascade Degradation of a Matrix Barrier and Immune Cell Penetration by a Photothermal Microneedle for Efficient Anticancer Therapy

For melanoma with high lethality and metastasis rate, traditional therapy has limited effects; local photothermal therapy (PTT) synergetic with immune therapy for cancer treatment can perhaps improve the situation. However, because of the natural existence of the tumor matrix barrier, the penetration depth of drugs and immune cells often dampens the efficacy of cancer treatment. Herein, we report an innovative synergetic PTT and immune therapy through dissolving microneedles for the codelivery of the hyaluronidase-modified semiconductor polymer nanoparticles containing poly(cyclopentadithiophene-alt-benzothiadiazole) and immune adjuvant polyinosinic-polycytidylic acid (PIC). Benefiting from the dissolution of an extracellular matrix of hyaluronidase, the semiconductor polymer nanoparticles and PIC penetrate the tumor deeply, under synergetic therapy with PTT, activating the immune cells and enhancing the T-cell immune response for inhibition of tumor growth and metastasis. This study provides a promising platform for effective melanoma treatment and a novel strategy to overcome the stromal barrier.

Near-infrared inorganic nanomaterial-based nanosystems for photothermal therapy

The development of robust materials for treating diseases through non-invasive photothermal therapy (PTT) has attracted increasing attention in recent years. Among various types of nanomaterials, inorganic nanomaterials with strong absorption in the near-infrared (NIR) window can be employed as high-efficiency photothermal agents to treat cancer and bacterial infections. In addition, inorganic nanomaterials can be easily combined with other drugs or chemical reagents to construct multifunctional nanomaterials to cascade stimulation responses, enhance therapeutic effects, and perform precise medical treatments. In this review, focusing on the latest developments of inorganic nanomaterials in photothermal therapy, we firstly introduced the light-to-heat conversion mechanism of inorganic nanomaterials. Secondly, we summarized the application of common inorganic nanomaterials, such as metallic nanoparticles, transition metal oxide nanoparticles and two dimensional (2D) nanosheets. In addition, the strategy of developing multifunctional nano-platforms with excellent biocompatibility as well as good targeted capability was also expounded. Finally, challenges and new perspectives for designing effective inorganic nanomaterial-based nanosystems for photothermal assisted therapy were also discussed.

Balancing the stability and drug activation in adaptive nanoparticles potentiates chemotherapy in multidrug-resistant cancer

Rationale: Prodrug strategies that render the drug temporarily inactive through a cleavable linkage are able to modulate the physicochemical properties of drugs for adaptive nanoparticle (NP) formulation. Here we used cabazitaxel as a model compound to test the validity of our "balancing NP stability and specific drug activation" strategy. Methods: Cabazitaxel is conjugated to hydrophobic polylactide fragments with varying chain lengths via a self-immolation linkage, yielding polymeric prodrugs that can be reactivated by reductive agents in cells. Following a nanoprecipitation protocol, cabazitaxel prodrugs can be stably entrapped in amphiphilic polyethylene-block-polylactide matrices to form core-shell nanotherapies with augmented colloidal stability. Results: Upon cellular uptake followed by intracellular reduction, the NPs spontaneously release chemically unmodified cabazitaxel and exert high cytotoxicity. Studies with near-infrared dye-labeled NPs demonstrate that the nanodelivery of the prodrugs extends their systemic circulation, accompanied with increased drug concentrations at target tumor sites. In preclinical mouse xenograft models, including two paclitaxel-resistant xenograft models, the nanotherapy shows a remarkably higher efficacy in tumor suppression and an improved safety profile than free cabazitaxel. Conclusion: Collectively, our approach enables more effective and less toxic delivery of the cabazitaxel drug, which could be a new generalizable strategy for re-engineering other toxic and water-insoluble therapeutics.

Activatable Polymeric Nanoprobe for Near-Infrared Fluorescence and Photoacoustic Imaging of T Lymphocytes

Development of real-time non-invasive imaging probes to assess infiltration and activation of cytotoxic T cells (CTLs) is critical to predict the efficacy of cancer immunotherapy, which however remains challenging. Reported here is an activatable semiconducting polymer nanoprobe (SPNP) for near-infrared fluorescence (NIRF) and photoacoustic (PA) imaging of a biomarker (granzyme B) associated with activation of CTLs. SPNP comprises a semiconducting polymer (SP) conjugated with a granzyme B cleavable and dye-labeled peptide as the side chain, both of which emit NIRF and PA signals. After systemic administration, SPNP passively targets the tumor and in situ reacts with granzyme B to release the dye-labeled peptide, leading to decreased NIRF and PA signals from the dye but unchanged signals from the polymer. Such ratiometric NIRF and PA signals of SPNP correlate well with the expression level of granzyme B and intratumoral population of CTLs. Thus, this study not only presents the first PA probes for in vivo imaging of immune activation but also provides a molecular design strategy that can be generalized for molecular imaging of other immune-related biomarkers.

Conjugated BODIPY Oligomers with Controllable Near-Infrared Absorptions as Promising Phototheranostic Agents through Excited-State Intramolecular Rotations

Conjugated molecules with coplanar strong donor and acceptor (D-A) units have been widely used in the design of near-infrared (NIR) photothermal agents to increase an absorption band through intramolecular charge transfer and to control intramolecular motions in aggregated states. However, such conjugated D-A systems have strong dipolar moments and intermolecular interactions, which may inhibit other channels of photothermal conversion and are often susceptible to nucleophiles, especially in the presence of light irradiation. Now, we report a molecular guideline to develop novel NIR organic photothermal nanoagents based on conjugated boron dipyrromethene (BODIPY) oligomers. This oligomerization is helpful not only for their tunable NIR absorptions in the ground state with distinctly redshifted absorption maxima up to 1002 nm and high extinction coefficients but also for their highly efficient photothermal conversion because of the possible motion of the BODIPY motifs around the ethene linked group in the excited state. These oligomers were fabricated as ultra-photostable nanoagents for multiple imaging-guided phototherapies, which efficiently accumulated in tumors, and gave complete tumor ablation with NIR laser irradiation. This strategy of "ground-state conjugation, excited-state rotation" provides a novel guideline to develop advanced theranostic molecules with NIR absorption.

Strategic Construction of Ethene-Bridged BODIPY Arrays with Absorption Bands Reaching the Near-Infrared II Region

An efficient strategy for the controllable synthesis of BODIPY arrays based on the Stille cross-coupling reaction has been developed, from which a family of well-defined ethene-bridged BODIPY arrays from dimer to hexamer was synthesized. These arrays showed strong absorptions reaching the near-infrared II (NIR II, 1000-1700 nm) region with maxima tunable from 702 nm (dimer) to 1114 nm (hexamer) and possessed efficient light-harvesting capabilities, excellent photostability, and good photothermal conversion abilities under NIR light irradiation.

Photosensitizer-stabilized self-assembling nanoparticles potentiate chemo/photodynamic efficacy of patient-derived melanoma

Development of injectable nanoparticles for delivery of active anticancer compounds often requires complicated schemes that involve tedious synthetic protocols and nanoformulations. In particular, clinical translation of synergistic nanoparticles that can facilitate multimodal therapies remains a considerable challenge. Herein, we describe a self-assembling, small-molecule nanosystem with unique properties, including near-infrared (NIR) light-responsive drug activation, size transformability, combinatorial synergy, and substantially reduced toxicity. Ligation of anticancer cabazitaxel (CTX) drugs via a reactive oxygen species-activatable thioketal linkage generates a dimeric TKdC prodrug, and subsequent coassembly with a photosensitizer, chlorin e6 (Ce6), forms colloidal-stable nanoassemblies (termed psTKdC NAs). Upon NIR laser irradiation, psTKdC NAs are transformed into smaller size particles and facilitate production of pharmacologically active CTX. Importantly, reactive oxygen species yielded by coassembled Ce6 can synergize with chemotherapy to achieve potent combinatorial effects. In a preclinical orthotopic model of an aggressive, human melanoma patient-derived xenograft (PDX), we show that administration of psTKdC NAs followed by laser irradiation produced durable tumor regression, with the tumors being completely eradicated in three of six PDXs. Furthermore, low systemic toxicity of this smart, photo-activatable nanotherapy was observed in animals. The new self-deliverable combinatorial system addresses essential requirements for high efficacy, safety, and translational capacity and deserves further investigation.

Dissolving Microneedles with Spatiotemporally controlled pulsatile release Nanosystem for Synergistic Chemo-photothermal Therapy of Melanoma

High aggressiveness and recurrence of melanoma tumors require multiple systemic drug administrations, causing discomfort and severe side effects to the patients. Topical treatment strategies that provide repetitively controllable and precise drug administrations will greatly improve treatment effects.

Methods: In this study, a spatiotemporally controlled pulsatile release system, which combined dissolving microneedles (DMNs) and thermal-sensitive solid lipid nanoparticles (SLNs), was constructed to realize multiple doses of dual-modal chemo-photothermal therapy in a single administration. Paclitaxel (PTX) and photothermal agent IR-780 were encapsulated into SLNs and were concentrated in the tips of DMNs (PTX/IR-780 SLNs @DMNs). Equipped with several needles, the DMN patch could be directly inserted into the tumor site and provide a stable “Zone accumulation” to constrain the PTX/IR-780 SLNs at the tumor site with uniform distribution.

Results:In vitro experiments showed that after irradiation with near-infrared light, the PTX/IR-780 SLNs gradually underwent phase transition, thereby accelerating the release of PTX. When irradiation was switched off, the PTX/IR-780 SLNs cooled to re-solidify with limited drug release. Compared with intravenous and intratumoral injections, very few SLNs from PTX/IR-780 SLNs @DMNs were distributed into other organs, resulting in enhanced bioavailability at the tumor site and good safety. In vivo analysis revealed that PTX/IR-780 SLNs @DMNs exhibited significant anti-tumor efficacy. In particular, the primary tumor was completely eradicated with a curable rate of 100% in 30 days and the highest survival rate of 66.67% after 100 days of treatment.

Conclusion: Herein, we developed a DMN system with a unique spatiotemporally controlled pulsatile release feature that provides a user-friendly and low-toxicity treatment route for patients who need long-term and repeat treatments.

Novel ultrasmall multifunctional nanodots for dual-modal MR/NIR-II imaging-guided photothermal therapy

Encouraging progress in multifunctional nanotheranostic agents that combine photothermal therapy (PTT) and different imaging modalities has been made. However, rational designed and biocompatible multifunctional agents that suitfable for in vivo application is highly desired but still challenging. In this work, we rationally designed novel ultrasmall multifunctional nanodots (FS-GdNDs) by combining the bovine serum albumin (BSA)-based gadolinium oxide nanodots (GdNDs) obtained through a biomineralization process with a small-molecule NIR-II fluorophore (FS). The as-prepared FS-GdNDs with an ultrasmall hydrodynamic diameter of 9.3 nm exhibited prominent NIR-II fluorescence properties, high longitudinal relaxivity (10.11 mM^-1 s^-1), and outstanding photothermal conversion efficiency (43.99%) and photothermal stability. In vivo studies showed that the FS-GdNDs with enhanced multifunctional characteristics diaplayed satisfactory dual-modal MR/NIR-II imaging performance with a quite low dose. The imaging-guided PTT achieved successful ablation of tumors and effectively extended the survival of mice. Cytotoxicity studies and histological assay demonstrated excellent biocompatibility of the nanodots. Importantly, this novel FS-GdNDs can undergo efficient body clearance through both hepatobiliary and renal excretion pathways. The novel ultrasmall multifunctional FS-GdNDs with excellent features hold tremendous potential in biomedical and clinical applications.

Double security drug delivery system DDS constructed by multi-responsive (pH/redox/US) microgel

In this paper, the multi-responsive core-shell microgels were prepared for constructing a double-locked drug delivery system. The pH- sensitive poly(2-(diisopropylamino ethylmethacry-late)-block-poly(ethyleneimine) diblock copolymers (PDPA-b-PEI) were synthesized and used to prepare micelles through their self-assembly in neutral solution. Redox-responsive gel shells were formed by Michael addition of primary amine group of branched PEI using disulfide as a cross-linker, which was specifically cleaved by glutathione (GSH). Anticancer drug doxorubicin DOX and perfluorohexane (PFH) could be encapsulated in the core of microgel. The DOX was released sustainably only under the condition of pH and GSH were both right. For example, under neutral condition with GSH, DOX could not release swimmingly due to the core of microgels was in hydrophobic state and wrapped the DOX firmly, although the gel shells were collapsed by GSH. When exposed to ultrasound, the drug released abruptly and achieved a complete release instantly. Moreover, it was found that the structure of the microgels was not destroyed after the ultrasound stimulus but had undergone an expansion-recovery process. Finally, it was demonstrated that the microgel had a "double security" effect, ensuring the low drug leakage during the normal blood circulation and efficient drug release under the pH/redox/ultrasound stimulus. The multi-responsive microgels designed here, which combines the usage of both endogenous and exogenous stimuli, has the advantages of low side-effect, high spatiotemporal controllability and complete release.

One Stone Two Birds: Zr-Fc Metal-Organic Framework Nanosheet for Synergistic Photothermal and Chemodynamic Cancer Therapy

Metal-organic frameworks (MOFs) have been identified as promising materials for the delivery of therapeutics to cure cancer owing to their intrinsic porous structure. However, in a majority of cases, MOFs act as only a delivery cargo for anticancer drugs while little attention has been focused on the utilization of their intriguing physical and chemical properties for potential anticancer purposes. Herein for the first time, an ultrathin (16.4 nm thick) ferrocene-based MOF (Zr-Fc MOF) nanosheet has been synthesized for synergistic photothermal therapy (PTT) and Fenton reaction-based chemodynamic (CDT) therapy to cure cancer without additional drugs. The Zr-Fc MOF nanosheet acts not only as an excellent photothermal agent with a prominent photothermal conversion efficiency of 53% at 808 nm but also as an efficient Fenton catalyst to promote the conversion of H₂O₂ into hydroxyl radical (^•OH). As a consequence, an excellent therapeutic performance has been achieved in vitro as well as in vivo through this combinational effect. This work aims to construct an "all-in-one" MOF nanoplatform for PTT and CDT treatments without incorporating any additional therapeutics, which may launch a new era in the investigation of MOF-based synergistic therapy platforms for cancer therapy.

Design of superior phototheranostic agents guided by Jablonski diagrams

This review summarizes how Jablonski diagrams guide the design of advanced organic optical agents and improvement of disease phototheranostic efficacies.

Near-IR absorbing J-aggregates of a phenanthrene-fused BODIPY as a highly efficient photothermal nanoagent

A phenanthrene-[b]-fused BODIPY exhibited well-defined J-aggregates in both pure hydrocarbon solution and aqueous solution, and was developed as a highly efficient photothermal nanoagent.

Surfactant-Stripped Micelles for NIR-II Photoacoustic Imaging through 12 cm of Breast Tissue and Whole Human Breasts

Surfactant-stripped micelles are formed from a commercially available cyanine fluoroalkylphosphate (CyFaP) salt dye and used for high contrast photoacoustic imaging (PAI) in the second near-infrared window (NIR-II). The co-loading of Coenzyme Q10 into surfactant-stripped CyFaP (ss-CyFaP) micelles improves yield, storage stability, and results in a peak absorption wavelength in the NIR-II window close to the 1064 nm output of Nd-YAG lasers used for PAI. Aqueous ss-CyFaP dispersions exhibit intense NIR-II optical absorption, calculated to be greater than 500 at 1064 nm. ss-CyFaP is detected through 12 cm of chicken breast tissue with PAI. In preclinical animal models, ss-CyFaP is visualized in draining lymph nodes of rats through 3.1 cm of overlaid chicken breast tissue. Following intravenous administration, ss-CyFaP accumulates in neoplastic tissues of mice and rats bearing orthotopic mammary tumors without observation of acute toxic side effects. ss-CyFaP is imaged through whole compressed human breasts in three female volunteers at depths of 2.6-5.1 cm. Taken together, these data show that ss-CyFaP is an accessible contrast agent for deep tissue PAI in the NIR-II window.

A Gold Nanocage/Cluster Hybrid Structure for Whole-Body Multispectral Optoacoustic Tomography Imaging, EGFR Inhibitor Delivery, and Photothermal Therapy

Gold nanocages (AuNCs) and gold nanoclusters (AuClusters) are two classes of advantageous nanostructures with special optical properties, and many other attractive properties. Integrating them into one nanosystem may achieve greater and smarter performance. Herein, a hybrid gold nanostructure for fluorescent and optoacoustic tomography imaging, controlled release of drugs, and photothermal therapy (PTT) is demonstrated. For this nanodrug (EA-AB), an epidermal growth factor receptor (EGFR) inhibitor erlotinib (EB) is loaded into AuNCs, which are then capped and functionalized by biocompatible AuCluster@BSA (BSA = bovine serum albumin) conjugates via electrostatic interaction. Upon cell internalization, the lysosomal proteases and low pH cause the release of EB from EA-AB, and also induce fluorescence restoration of the AuCluster for imaging. Irradiation with near-infrared light further promotes the drug release and affords a PTT effect as well. The AuNC-based nanodrug is optoacoustically active, and its biodistribution and metabolic process have been successfully monitored by whole-body and 3D multispectral optoacoustic tomography imaging. Owing to the combined actions of PTT and EGFR pathway blockage, EA-AB exhibits marked tumor inhibition efficacy in vivo.

Facile Transfer of Reverse Micelles from the Organic to the Aqueous Phase for Mimicking Enzyme Catalysis and Imaging-Guided Cancer Therapy

Reverse micelles (RMs) with confined water pools have been applied in many fields. However, the water insolubility of RMs seriously limits the scope of their application, especially those needed to operate in aqueous environments. Here, we report the first successful transfer of RMs from the organic phase to water phase without disturbing their confined water pools and hydrophobic alkyl region. This transfer was achieved by virtue of a mild host-guest interaction between the hydrophobic tails of interfacial cross-linked reverse micelles (ICRMs) and the hydrophobic cavity of (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD). Benefitting from the maintained confined water pools and the hydrophobic scaffold, the obtained water-soluble ICRMs served as multifunctional nanoplatforms for enzyme-mimicking catalysis and image-guided cancer therapy, which were impossible for normal RMs lacking water solubility or confined pool-buried water-soluble nanoparticles without a hydrophobic alkyl chain. This mild transfer approach thus surmounts the application obstacle of RMs and opens up new avenues for their application in aqueous environments.