Tuning the photophysical properties of cyanine by barbiturate functionalization and nanoformulation for efficient optoacoustics- guided phototherapy.

Cyanine derivatives are organic dyes widely used for optical imaging. However, their potential in longitudinal optoacoustic imaging and photothermal therapy remains limited due to challenges such as poor chemical stability, poor photostability, and low photothermal conversion. In this study, we present a new structural modification for cyanine dyes by introducing a strongly electron-withdrawing group (barbiturate), resulting in a new series of barbiturate-cyanine dyes (BC810, BC885, and BC1010) with suppressed fluorescence and enhanced stability. Furthermore, the introduction of BC1010 into block copolymers (PEG114-b-PCL60) induces aggregation-caused quenching, further boosting the photothermal performance. The photophysical properties of nanoparticles (BC1010-NPs) include their remarkably broad absorption range from 900 to 1200 nm for optoacoustic imaging, allowing imaging applications in NIR-I and NIR-II windows. The combined effect of these strategies, including improved photostability, enhanced nonradiative relaxation, and aggregation-caused quenching, enables the detection of optoacoustic signals with high sensitivity and effective photothermal treatment of in vivo tumor models when BC1010-NPs are administered before irradiation with a 1064 nm laser. This research introduces a barbiturate-functionalized cyanine derivative with optimal properties for efficient optoacoustics-guided theranostic applications. This new compound holds significant potential for biomedical use, facilitating advancements in optoacoustic-guided diagnostic and therapeutic approaches.

Anti-Quenching NIR-II Excitation Phenylboronic Acid Modified Conjugated Polyelectrolyte for Intracellular Peroxynitrite-Enhanced Chemo-Photothermal Therapy.

Multidrug resistance to clinical chemotherapeutic drugs severely limits antitumor efficacy and patient survival. The integration of chemotherapy with photothermal therapy (PTT) and reactive nitrogen species has become a major strategy to enhance cancer treatment efficacy. Herein, a multifunctional peroxynitrite (ONOO-) nanogenerator (PBT/NO/Pt) for NIR-II fluorescence (NIR-II FL)/NIR-II photoacoustic (NIR-II PA) imaging-guided chemo/NIR-II PTT/ONOO- combination therapy is reported. The multifunction nanogenerator is developed by co-loading a pH-sensitive nitric oxide donor (DETA NONOate) and nicotinamide adenine dinucleotide phosphate oxidases trigger superoxide (O2 •-) generator chemotherapy drug (CDDP) to an NIR-II excitation-conjugated polyelectrolyte (PNC11BA). PNC11BA has non-conjugated alkyl chain segments in the polymer backbone and abundant positively charged phenylboronic acid in its side chains, which support the anti-quenching of NIR-II FL and the integration of DETA NONOate and CDDP into PBT/NO/Pt. In the acidic tumor microenvironment, the coordination bonds between CDDP and PNC11BA are cleaved, releasing CDDP for chemotherapeutic activity. The simultaneous release of nitric oxide (NO) and O2 •- rapidly leads to the in situ generation of the more cytotoxic reactive physiological nitrogen species ONOO-. In vitro and in vivo results prove that PBT/NO/Pt exhibited a markedly ONOO- enhanced chemo-photothermal synergistic therapy for SKOV3/DDP tumor by downregulating the intracellular glutathione and increasing CDDP-DNA adducts.

An All-Rounder for NIR-II Phototheranostics: Well-Tailored 1064 nm-Excitable Molecule for Photothermal Combating of Orthotopic Breast Cancer.

The second near-infrared (NIR-II, 1000-1700 nm) light-activated organic photothermal agent that synchronously enables satisfying NIR-II fluorescence imaging is highly warranted yet rather challenging on the basis of the overwhelming nonradiative decay. Herein, such an agent, namely TPABT-TD, was tactfully designed and constructed via employing benzo[c]thiophene moiety as bulky electron donor/π-bridge and tailoring the peripheral molecular rotors. Benefitting from its high electron donor-acceptor strength and finely modulated intramolecular motion, TPABT-TD simultaneously exhibits ultralong absorption in NIR-II region, intense fluorescence emission in the NIR-IIa (1300-1500 nm) region as nanoaggregates, and high photothermal conversion upon 1064 nm laser irradiation. Those intrinsic advantages endow TPABT-TD nanoparticles with prominent fluorescence/photoacoustic/photothermal trimodal imaging-guided NIR-II photothermal therapy against orthotopic 4T1 breast tumor with negligible adverse effect.

Chalcogen Atom-Modulated Croconaine for Efficient NIR-II Photothermal Theranostics.

Organic dye-based agents with near-infrared (NIR)-II absorption have great potential for cancer theranostics because of the deeper tissue penetration and good biocompatibility. However, proper design is required to develop NIR-II-absorbing dyes with good optical properties. We proposed to construct chalcogen atom-modulated croconaine for NIR-II light-triggered photothermal theranostics. By introducing different chalcogen atoms (O, S, Se, or Te) into the structure of croconaine, the light absorption of croconaine can be precisely regulated from the NIR-I to the NIR-II range due to the heavy-atom effect. Especially, Te-substituted croconaine (CRTe) and its nanoformulations exhibit superior NIR-II responsiveness, a high photothermal conversion efficiency (70.6%), and good photostability. With their favorable tumor accumulation, CRTe-NPs from tumor regions can be visualized by NIR-II optoacoustic systems with high resolution and high contrast; meanwhile, their superior photothermal performance also contributes to efficient cell killing and tumor elimination upon 1064 nm laser irradiation. Therefore, this work provides an efficient strategy for the molecular design of NIR-II organic photothermal agents.

An NIR-II Excitable AIE Small Molecule with Multimodal Phototheranostic Features for Orthotopic Breast Cancer Treatment.

One-for-all phototheranostics, referring to a single component simultaneously exhibiting multiple optical imaging and therapeutic modalities, has attracted significant attention due to its excellent performance in cancer treatment. Benefitting from the superiority in balancing the diverse competing energy dissipation pathways, aggregation-induced emission luminogens (AIEgens) are proven to be ideal templates for constructing one-for-all multimodal phototheranostic agents. However, to this knowledge, the all-round AIEgens that can be triggered by a second near-infrared (NIR-II, 1000-1700 nm) light have not been reported. Given the deep tissue penetration and high maximum permissible exposure of the NIR-II excitation light, herein, this work reports for the first time an NIR-II laser excitable AIE small molecule (named BETT-2) with multimodal phototheranostic features by taking full use of the advantage of AIEgens in single molecule-facilitated versatility as well as synchronously maximizing the molecular donor-acceptor strength and conformational distortion. As formulated into nanoparticles (NPs), the high performance of BETT-2 NPs in NIR-II light-driven fluorescence-photoacoustic-photothermal trimodal imaging-guided photodynamic-photothermal synergistic therapy of orthotopic mouse breast tumors is fully demonstrated by the systematic in vitro and in vivo evaluations. This work offers valuable insights for developing NIR-II laser activatable one-for-all phototheranostic systems.

NIR-II Excitation Phototheranostic Nanomedicine for Fluorescence/Photoacoustic Tumor Imaging and Targeted Photothermal-Photonic Thermodynamic Therapy.

The success of phototheranostics is hampered by some intrinsic defects, such as limited light penetration depth, heat resistance of tumor cells to photothermal therapy (PTT) induced by heat shock protein (HSP) and stress resistance against photodynamic therapy (PDT) caused by hypoxia microenvironment of tumor. Herein, a second near infrared (NIR-II) light excitation phototheranostic nanomedicine has been fabricated by integrating the semiconducting polymer, azo compound, and HSP inhibitor into a thermosensitive liposome, followed by modification with targeting aptamer, forming Lip(PTQ/GA/AIPH) for multimodal phototheranostics of triple-negative breast cancer (TNBC). The phototheranostic nanomedicine provides tumor targeting NIR-II fluorescence and photoacoustic dual-modal imaging, as well as NIR-II PTT. The released HSP inhibitor can effectively inhibit the activity of HSP for enhanced NIR-II PTT. Moreover, azo compound can be decomposed by the NIR-II photothermal activation, generating cytotoxic free radicals and realizing oxygen-irrelevant photonic thermodynamic therapy (PTDT) effects. Under the NIR-II laser irradiation, NIR-II fluorescence/photoacoustic dual-modal imaging guided enhanced NIR-II PTT and PTDT by Lip(PTQ/GA/AIPH), can achieve precise diagnosis and effective suppression of deep-seated TNBC with negligible side effects. This work develops a promising NIR-II excitation phototheranostic nanomedicine for spatiotemporally specific diagnosis and combination therapy of TNBC.

AIE-active two-photon fluorescent nanoprobe with NIR-II light excitability for highly efficient deep brain vasculature imaging.

Aggregation induced emission (AIE)-active bright two-photon fluorescent probes with second near-infrared (NIR-II) light excitability can be used for efficient brain bioimaging studies, wherein the fabrication of water-dispersible nanoparticles by encapsulating the hydrophobic probes with amphiphilic polymer holds the key to ensuring biocompatibility and in vivo adaptability. However, barely any study has evaluated the structural requirements that can substantially affect the water-dispersible nanoparticle formation ability of an organic AIE-active dye with amphiphilic polymers. The present study systematically assessed the structural dependency of a well-known acrylonitrile based AIE system/fluorogenic core upon the formation of water-dispersible nanoparticles and elucidated how the structural modifications can impact the in vivo two-photon imaging. Methods: A total of four acrylonitrile-based aggregation induced emission (AIE)-active two-photon (TP) fluorescent probes (AIETP, AIETP C1, AIETP C2 and AIETP C3) have been judiciously designed and synthesized with structural variations to realize how the structural alterations could substantially influence the water-dispersible nanoparticle formation ability (with amphiphilic polymers) and photo-stability to impact the in vivo imaging. Results: It has been found that the incorporation of the phenyl-thiazole unit in AIETP, AIETP C2 and AIETP C3 facilitated the formation of water-dispersible nanoparticles (NPs) with amphiphilic polymers (Pluronic F127) whereas the presence of only phenyl moiety instead in AIETP C1 could not meet the suitable condition to form the NPs with good aqueous dispersibility. Rationally designed AIETP NPs that exhibited higher brightness, improved photostability and good two-photon absorption cross section was successfully employed for in vivo brain vasculature imaging. Conclusions: Robust noninvasive 2D and 3D two-photon (NIR-II light, 1040 nm) brain vasculature imaging with beneficial attributes such as outstanding penetration depth (800 µm) and exceptional spatial resolution (1.92 µm), were achieved by utilizing AIETP NPs in this study.

Facile Synthesis of Efficient Luminogens with AIE Features for Three-Photon Fluorescence Imaging of the Brain through the Intact Skull.

Visualization of the brain in its native environment is important for understanding common brain diseases. Herein, bright luminogens with remarkable aggregation-induced emission (AIE) characteristics and high quantum yields of up to 42.6% in the solid state are synthesized through facile reaction routes. The synthesized molecule, namely BTF, shows ultrabright far-red/near-infrared emission and can be fabricated into AIE dots by a simple nanoprecipitation procedure. Due to their high brightness, large Stokes shift, good biocompatibility, satisfactory photostability, and large three-photon absorption cross section, the AIE dots can be utilized as efficient fluorescent nanoprobes for in vivo brain vascular imaging through the intact skull by a three-photon fluorescence microscopy imaging technique. This is the first example of using AIE dots for the visualization of the cerebral stroke process through the intact skull of a mouse with high penetration depth and good image contrast. Such good results are anticipated to open up a new venue in the development of efficient emitters with strong nonlinear optical effects for noninvasive bioimaging of living brain.

Tm3+ -Sensitized NIR-II Fluorescent Nanocrystals for In†Vivo Information Storage and Decoding.

In vivo fluorescence imaging in the second near-infrared window (NIR-II) affords deep-tissue penetration and high spatial resolution. Herein, we present a new type of Tm3+ -sensitized lanthanide nanocrystals with both excitation (1208 nm) and emission (1525 nm) located in the NIR-II window for in vivo optical information storage and decoding. Taking advantage of the tunable fluorescence lifetimes, the optical multiplexed encoding capacity is enhanced accordingly. Micro-devices with QR codes featuring the NIR-II fluorescence-lifetime multiplexed encoding were implanted into mice and were successfully decoded through time-gated fluorescence imaging technology.

Aggregation-Induced Emission Luminogen with Near-Infrared-II Excitation and Near-Infrared-I Emission for Ultradeep Intravital Two-Photon Microscopy.

Currently, a serious problem obstructing the large-scale clinical applications of fluorescence technique is the shallow penetration depth. Two-photon fluorescence microscopic imaging with excitation in the longer-wavelength near-infrared (NIR) region (>1100 nm) and emission in the NIR-I region (650-950 nm) is a good choice to realize deep-tissue and high-resolution imaging. Here, we report ultradeep two-photon fluorescence bioimaging with 1300 nm NIR-II excitation and NIR-I emission (peak ∼810 nm) based on a NIR aggregation-induced emission luminogen (AIEgen). The crab-shaped AIEgen possesses a planar core structure and several twisting phenyl/naphthyl rotators, affording both high fluorescence quantum yield and efficient two-photon activity. The organic AIE dots show high stability, good biocompatibility, and a large two-photon absorption cross section of 1.22 × 103 GM. Under 1300 nm NIR-II excitation, in vivo two-photon fluorescence microscopic imaging helps to reconstruct the 3D vasculature with a high spatial resolution of sub-3.5 µm beyond the white matter (>840 µm) and even to the hippocampus (>960 µm) and visualize small vessels of ∼5 µm as deep as 1065 µm in mouse brain, which is among the largest penetration depths and best spatial resolution of in vivo two-photon imaging. Rational comparison with the AIE dots manifests that two-photon imaging outperforms the one-photon mode for high-resolution deep imaging. This work will inspire more sight and insight into the development of efficient NIR fluorophores for deep-tissue biomedical imaging.