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.

J-aggregation strategy of organic dyes for near-infrared bioimaging and fluorescent image-guided phototherapy.

With the continuous development of organic materials for optoelectronic devices and biological applications, J-aggregation has attracted a great deal of interest in both dye chemistry and supramolecular chemistry. Except for the characteristic red-shifted absorption and emission, such ordered head-to-tail stacked structures may be accompanied by special properties such as enhanced absorption, narrowed spectral bandwidth, improved photothermal and photodynamic properties, aggregation-induced emission enhancement (AIEE) phenomenon, and so forth. These excellent properties add great potential to J-aggregates for optical imaging and phototherapy in the near-infrared (NIR) region. Despite decades of development, the challenge of rationally designing the molecular structure to adjust intermolecular forces to induce J-aggregation of organic dyes remains significant. In this review, we discuss the formation of J-aggregates in terms of intermolecular interactions and summarize some recent studies on J-aggregation dyes for NIR imaging and phototherapy, to provide a clear direction and reference for designing J-aggregates of near-infrared organic dyes to better enable biological applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

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.

Macromolecular conjugated cyanine fluorophore nanoparticles for tumor-responsive photo nanotheranostics.

For photothermal therapy (PTT), the improved targeting can decrease the dosage and promote the therapeutic function of photothermal agents, which would effectively improve the antitumor effect. The tumor microenvironment (TME) and cells are targets in designing intelligent and responsive theranostics. However, most of these schemes have been limited to the traditional visible and first near-infrared (NIR-I) regions, eager to expand to the second near-infrared (NIR-II) window. We designed and synthesized a polyethylene glycol conjugated and disulfide-modified macromolecule fluorophore (MPSS). MPSS could self-assemble into core-shell micelles in an aqueous solution (MPSS-NPS), while the small molecule probes were in a high aggregation arrangement inside the nanoparticle. The pronounced aggregation quenching (ACQ) effect caused them to the "sleeping" state. After entering the tumor cells, the disulfide bonds in MPSS-NPS broke in response to a high concentration of glutathione (GSH) in TME, and the molecule probes were released. The highly aggregated state was effectively alleviated, resulting in distinct absorption enhancement in the near-infrared region. Therefore, the fluorescence signal was recovered, and the photothermal performance was triggered. In vitro and in vivo studies reveal that the Nano-system is efficient for the smart NIR-II fluorescence imaging-guided PTT, even at a low dosage and density of irradiation.

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.

Galactose conjugated boron dipyrromethene and hydrogen bonding promoted J-aggregates for efficiently targeted NIR-II fluorescence assistant photothermal therapy.

It is essential to develop novel multifunctional and easily synthesized stable NIR-II fluorescent probes to guide photothermal therapy for tumors. Here, we propose a new strategy to construct boron dipyrromethene (BODIPY) J-aggregates by intermolecular hydrogen bonding (H-bond) and π-π stacking interactions to achieve fluorescence emission in the second near-infrared window (NIR-II, 1000-1700 nm). A novel meso-benzamide galactose hexanoate-BODIPY (Gal-OH-BDP) amphiphilic small molecular dye was synthesized and it formed nanoparticles spontaneously in aqueous solution with a maximum emission wavelength near 1060 nm, which works as a smart nanomedicine for targeting NIR-II imaging-guided photothermal therapy (PTT) of hepatocellular carcinoma. Galactose not only provided hydrogen bonds to regulate the aggregation pattern of the molecules but also effectively targeted hepatocellular carcinoma cells and promoted the formation of well-dispersed nanoparticles of dye molecules due to their hydrophilicity. Moreover, due to high photothermal conversion efficiency (PCE = 55%), Gal-OH-BDP NPs achieve galactose-targeted NIR-II imaging and PTT, which is important for the precise diagnosis and treatment of tumors (Scheme 1). In the present research work, H-bond was introduced for the first time into BODIPY for building J-aggregates to achieve the NIR-II fluorescence.

Stable twisted conformation aza-BODIPY NIR-II fluorescent nanoparticles with ultra-large Stokes shift for imaging-guided phototherapy.

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for in vivo imaging and imaging-guided phototherapy with deep penetration and high spatiotemporal resolution. It is very appealing to obtain NIR-II fluorescent probes through simple procedures and economical substrates. Herein, we developed a D-A-D' structure NIR-II photosensitizer (triphenylamine modified aza-Bodipy, TAB) based on the strong electron-withdrawing nature of borane difluoride azadipyrromethene's center (aza-BODIPY). Subsequently, halogen atoms (Br, I) were introduced to the TAB molecule, and TAB-2Br and TAB-2I were synthesized. Compared to the TAB molecule, a significant redshift in the emission wavelength, ultra-large Stokes shift (>300 nm), and enhanced singlet oxygen production capacity were acquired for the halogenated molecules. After self-assembly of TABs and an amphiphilic polypeptide POEGMA23-PAsp20, the obtained P-TAB, P-TAB-2Br, and P-TAB-2I nanoparticles exhibited excellent water solubility and biocompatibility, remarkable photothermal conversion efficiency (beyond 40%), and good resistance to photobleaching, heat, and H2O2. Under 808 nm laser irradiation, the P-TAB-2I exhibited an efficient photothermal effect and ROS generation in vitro. And in vivo experiments revealed that P-TAB-2I displayed efficient NIR-II fluorescence imaging and remarkable tumor ablation results. All of these results make TAB-2I potential organic probes for clinical NIR-II fluorescence imaging and cancer phototherapy.

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

Most NIR-II fluorescent dyes, especially polymethine cyanine, face the inevitable self-quenching phenomenon in an aqueous solution. This unacceptable property has severely limited their application in high-resolution biological imaging. Here, a NIR-II macromolecular probe (MPAE) is synthesized through the structure modification of molecule probe and the covalent coupling of an amphiphilic polypeptide, which presents considerable biocompatibility and negligible systemic side effect. The molecule probe's stereo structure and the polymer's conjugation could effectively prevent the π-π stacking, thereby exhibiting excellent quenching resistance in aqueous solutions (absolute QY = 0.178%). This remarkable feature endows it with deeper tissue penetration than the clinically used indocyanine green (ICG) and high contrast brightness at the tumor site for the NIR-II fluorescence imaging. Based on the effective accumulation of tumor sites and considerable photothermal conversion efficiency (40.07%), the MPAE-NPS presents superior antitumor efficiency on breast tumor-bearing mice under the 1064 nm irradiation without rebound or recurrence. All these outstanding performances reveal the great promise of MPAE-NPS in Nano-drug delivery and imaging-assisted photothermal therapy in the NIR-II window.

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.

Polypeptide-Conjugated Second Near-Infrared Organic Fluorophore for Image-Guided Photothermal Therapy.

Image-guided photothermal therapy (PTT) is an attractive strategy to improve the diagnosis accuracy and treatment outcomes by monitoring the accumulation of photothermal agents in tumors in real-time and determining the best treatment window. Taking advantage of the superior imaging quality of NIR-II fluorescence imaging and remote-controllable phototherapy modality of PTT, we developed a facile macromolecular fluorophore (PF) by conjugating a small-molecule NIR-II fluorophore (Flav7) with an amphiphilic polypeptide. The PF can form uniform micelles in aqueous solution, which exhibit a slight negative charge. In vitro experimental results showed that the PF nanoparticles showed satisfactory photophysical properties, prominent photothermal conversion efficiency (42.3%), excellent photothermal stability, negligible cytotoxicity, and photothermal toxicity. Meanwhile, the PF can visualize and feature the tumors by NIR-II fluorescence imaging owing to prolonged blood circulation time and enhanced accumulation in tumors. Moreover, in vivo studies revealed that the PF nanoparticles achieved an excellent photothermal ablation effect on tumors with a low dose of NIR-II dye and light irradiation, and the process can be traced by NIR fluorescence imaging.