Acceptor-engineering tailored type-Ⅰ photosensitizer with aggregation-induced NIR-II emission for cancer multimodal phototheranostics

Exploration of single molecular species synchronously featured by long excitation/emission wavelength, accurate diagnosis, and effective therapy, remains supremely appealing to implement high-performance cancer phototheranostics. However, those previously established phototheranostic agents are undiversified and stereotyped in terms of structural skeleton, and generally exhibit insufficient phototheranostic outcomes. Herein, we innovatively utilized indanone-condensed thiadiazolo[3,4-g]quinoxaline(ITQ) as electron acceptor to construct novel photosensitizer with second near-infrared(NIR-II) emission. Experimental study and theoretical calculation demonstrated that comparing with the counterparts constituting by widely employed NIR-II building block benzobisthiadiazole(BBTD) and 6,7-diphenylthiadiazoloquinoxaline(DPTQ), ITQ-based photosensitizer(TITQ) showed superior aggregation-induced emission(AIE) characteristics, much stronger type-I reactive oxygen species(ROS) production, and prominent photothermal conversion capacity. Furthermore, TITQ nanoparticles with excellent biocompatibility were capable of effectively accumulating in the tumor site and visualizing tumor through fluorescence-photoacoustic-photothermal trimodal imaging with highly spatiotemporal resolution, and completely eliminating tumor by type-I photodynamic-photothermal therapy.

Phototheranostic Nanoagents for Imaging-Guided Treatment of Oral Cancer

Phototherapy showed almost a lack of drug resistance and,depending on the therapeutic effects of non-invasive light-stimulating photosensors.The side effects of phototherapy were greatly reduced compared to their traditional equivalents.Phototheranostic nanoagents had new properties in drug delivery,biocompatibility,targeting and response,in which traditional phototheranostic drugs can not possess.Recently,a large number of relevant studies have demonstrated that photodynamic therapy(PDT)in combination with other agents and image-guided multifunctional photothermal therapy(PTT)were well suited for the treatment of oral cancer.Through the design of the nanoagents,researchers have discovered various applications for phototherapy,such as targeted release of co-packaged drugs,multifunctional imaging for diagnosis and treatment combination,accurate targeting caused by nanocarriers,and synergistic chemotherapy with phototherapy.In this paper,we first reviewed the research related to phototheranostic nanoagents for image-guided treatment of oral cancer.We tried to introduce the design concept and the treatment effect by three parts of components of phototheranostic nanoagents,categories of phototheranostic nanoagents and application of phototheranostic nanoagents.It also provided a reference for nanomaterial development and clinical applications in research of oral cancer treatment.

Applications of phototheranostic nanoagents in photodynamic therapy

Nanotherapeutics has an increasing role in the treatment of diseases such as cancer. In photodynamic therapy （PDT） a therapeutically inactive photosensitizer compound is selectively activated by light to produce molecules capable of killing diseased cells and pathogens. A phototheranostic agent can be defined as a single nanoentity with the capabilities for targeted delivery, optical imaging and photodynamic treatment of a disease. Malignant cells, tissue and microbial etiologic agents can be effectively targeted by PDT. Photodynamic therapy is noninvasive, or minimally invasive, and has few side effects as damage to healthy tissue is minimized and the killing effect is localized. Various forms of cancer, acne and other diseases may be treated. The in vivo efficacy of photosensitizers is further improved by attaching them to nanostructures capable of targeting the diseased site. Such photosensitizer-functionalized nanostructures, or nano- therapeutics, allow site-specific delivery of imaging and therapeutic agents for improved phototheranostic performance. This review explores the potential applications of phototheranostic nanostructures in diagnosis and therapy.

Gathering brings strength:How organic aggregates boost disease phototheranostics

Phototheranostics that concurrently and complementarily integrate real-time diagnosis and in situ therapeutic capabilities in one platform has become the advancing edge of precision medicine.Organic agents possess the merits of facile preparation,high purity,tunable photophysical property,good biocompatibility,and potential biodegradability,which have shown great promise for disease theranostics.This review summarizes the recent achievements of organic phototheranostic agents and applications,especially which rationally utilize energy dissipation pathways of Jablonski diagram to modulate the fluorescence emission,photoacoustic/photothermal production,and photodynamic processes.Of particular interest are the systems exhibiting huge differences in aggregate state as compared with the solution or single molecule form,during which the intramolecular motions play an important role in regulating the photophysical properties.The recent advances from such an aspect for biomedical applications including high-resolution imaging,activatable imaging and therapy,adaptive theranostics,image-guided surgery,immunotherapy,and afterglow imaging are discussed.A brief summary and perspective in this field are also presented.We hope this review will be helpful to the researchers interested in bioprobe design and theranostic applications,and inspire new insights into the linkage between aggregate science and biomedical field.

Small Molecular NIR-II Fluorophores for Cancer Phototheranostics

Phototheranostics integrates deep-tissue imaging with phototherapy(containing photothermal therapy and photodynamic therapy),holding great promise in early diagnosis and precision treatment of cancers.Recently,second near-infrared(NIR-II)fluorescence imaging exhibits the merits of high accuracy and specificity,as well as real-time detection.Among the NIR-II fluorophores,organic small molecular fluorophores have shown superior properties in the biocompatibility,variable structure,and tunable emission wavelength than the inorganic NIR-II materials.What’s more,some small molecular fluorophores also display excellent cytotoxicity when illuminated with the NIR laser.This review summarizes the progress of small molecular NIR-II fluorophores with different central cores for cancer phototheranostics in the past few years,focusing on the molecular structures and phototheranostic performances.Furthermore,challenges and prospects of future development toward clinical translation are discussed.

A facile phototheranostic nanoplatform integrating NIR-Ⅱ fluorescence/PA bimodal imaging and image-guided surgery/PTT combinational therapy for improved antitumor efcacy

Phototheranostic with highly integrated functions is an attractive platform for cancer management. It remains challenging to develop a facile phototheranostic platform with complementary bimodal imaging and combinational therapy capacity. Herein, the small-molecule cyanine IR780 loaded liposomes have been harnessed as a nanoplatform to simultaneously realize photoacoustic(PA)/the second near-infrared window(NIR-Ⅱ) fluorescence imaging and image-guided surgery/adjuvant photothermal therapy(PTT).This nanoplatform exhibits attractive properties like uniform controllable size, stable dispersibility, NIR-Ⅱ fluorescence emission, photothermal conversion, and biocompatibility. Benefiting from the complementary PA/NIR-Ⅱ fluorescence bimodal imaging, this nanoplatform was successfully applied in precise vasculature delineation and tumor diagnosis. Interestingly, the tumor was clearly detected by NIR-Ⅱ fluorescence imaging with the highest tumor-to-normal-tissue ratio up to 12.69, while signal interference from the liver was significantly reduced, due to the difference in the elimination rate of the nanoplatform in the liver and tumor. Under the precise guidance of the image, the tumor was accurately resected, and the simulated residual lesion after surgery was completely ablated by adjuvant PTT. This combined therapy showed improved antitumor efcacy over the individual surgery or PTT. This work develops a facile phototheranostic nanoplatform with great significance in accurately diagnosing and effectively treating tumors using simple NIR light irradiation.

Construction of a 980 nm laser-activated Pt(Ⅱ)metallacycle nanosystem for efficient and safe photo-induced bacteria sterilization

Although metal-based chemical agents have demonstrated promising bacteriostatic effects in phototherapy,their short excitation/emission wavelengths and inadequate phototherapy efficiencies make their application in vivo difficult.We therefore synthesized a novel Pt(Ⅱ)metallacycle(Pt1110)that can be activated with a 980 nm laser for photodiagnosis/treatment in deep tissue.We found that Pt1110 significantly improved photothermal conversion(95%improvement)and ^(1)O_(2) generation(ΦΔ75%increase)compared to the ligand itself 1 and was well capable of light-induced sterilization under safe laser irradiation(0.72 W/cm^(2)).In addition,Pt1110 has little to no toxicity to cells.After incorporated into liposome,Pt1110 NPs was effective in wound healing in infection and keratitis models upon laser irradiation,which was accurately observed by NIR-Ⅱfluorescence imaging.This novel metal-coordinated supramolecular material has a potential to become a universal platform for phototherapy in deep tissue.

Building multipurpose nano-toolkit by rationally decorating NIR-Ⅱ fluorophore to meet the needs of tumor diagnosis and treatment

Phototheranostics have attracted tremendous attention in cancer diagnosis and treatment because of the noninvasiveness and promising effectiveness.Developing advanced phototheranostic agents with long emission wavelength,excellent biocompatibility,great tumor-targeting capability,and efficient therapeutic effect is highly desirable.However,the mutual constraint between imaging and therapeutic functions usually hinders their wide applications in biomedical field.To balance this contradiction,we herein rationally designed and synthesized three novel tumor-targeted NIR-Ⅱ probes(QR-2PEG_(321),QR-2PEG_(1000),and QR-2PEG_(5000)) by conjugating three different chain lengths of PEG onto an integrin α_(v)β_(3)-targeted NIR-Ⅱ heptamethine cyanine fluorophore,respectively.In virtue of the essential amphiphilic characteristics of PEG polymers,these probes display various degree of aggregation in aqueous buffer accompanying with differential NIR-Ⅱ imaging and photothermal(PTT) therapeutic performance.Both in vitro and in vivo results have demonstrated that probe QR-2PEG_(5000) has the best NIR-Ⅱ imaging performance with prominent renal clearance,whereas QR-2PEG_(321)possesses excellent photoacoustic signal as well as PTT effect,which undoubtedly provides a promising toolbox for tumor diagnosis and therapy.We thus envision that these synthesized probes have great potential to be explored as a toolkit for precise diagnosis and treatment of malignant tumors.

Polycyclic naphthalenediimide-based nanoparticles for NIR-Ⅱ fluorescence imaging guided phototherapy

Optical imaging and phototherapy in the second near-infrared window(NIR-Ⅱ, 900–1700 nm) can reduce tissue auto-fluorescence and photon scattering, which facilitates higher spatial resolution and deeper tissue penetration depth for solid tumor theranostics. Herein, a polycyclic naphthalenediimide(NDI) based chromophore 13-amino-4,5-dibromo-2,7-di(dodecan-6-yl)-1 H-isoquinolino[4,5,6-fgh]naphtho[1,8-bc][1,9]phenanthroline-1,3,6,8(2H,7H,9H)-tetraone(NDI-NA) was designed and synthesized. With large polycyclic π-systems, NDI-NA molecule possesses broad near-infrared(NIR) absorption(maximum at777 nm) and emission(maximum at 921 nm). By nanoprecipitation, NDI-NA nanoparticles(NPs) were formed in aqueous solution with J-aggregative state, which showed huge red-shift in both absorption spectrum(maximum at 904 nm) and emission spectrum(maximum at 1,020 nm), endowing NDI-NA NPs efficient NIR-Ⅱ fluorescence imaging capability. Besides, the NPs present effective tumor-targeting capability in vivo based on the enhanced permeation and retention(EPR) effect. More importantly, NDI-NA NPs simultaneously have high photothermal conversion efficiency(30.8%) and efficient reactive oxygen species generation ability, making them remarkably phototoxic to cancer cells. The polycyclic chromophore based multifunctional NDI-NA NPs as NIR-Ⅱ phototheranostic agents possess bright future for clinical NIR-Ⅱ imaging-guided cancer phototherapy.

Boron difluoride formazanate dye for high-efficiency NIR-Ⅱ fluorescence imaging-guided cancer photothermal therapy

The small molecular second near-infrared(NIR-Ⅱ, 1000–1700 nm) dye-based nanotheranostics can concurrently combine deep-tissue photodiagnosis with in situ phototherapy, which occupies a vital position in the early detection and precise treatment of tumors. However, the development of small molecular NIR-Ⅱ dyes is still challenging due to the limited electron acceptors and cumbersome synthetic routes.Herein, we report a novel molecular electron acceptor, boron difluoride formazanate(BDF). Based on BDF, a new small molecular NIR-Ⅱ dye BDF1005 is designed and synthesized with strong NIR-I absorption at 768 nm and bright NIR-Ⅱ peak emission at 1034 nm. In vitro and in vivo experiments demonstrate that BDF1005-based nanotheranostics can be applied for NIR-Ⅱ fluorescence imaging-guided photothermal therapy of 4T1 tumor-bearing mice. Under 808 nm laser irradiation, tumor growth can be effectively inhibited. This work opens up a new road for the exploitation of NIR-Ⅱ small molecular dyes for cancer phototheranostics.

Liposome trade-off strategy in mitochondria-targeted NIR-cyanine: balancing blood circulation and cell retention for enhanced antitumor phototherapy in vivo

Cancer phototheranostics involving optical imaging-guided photodynamic therapy(PDT)and photothermal therapy(PTT)is a localized noninvasive approach in treating cancer.Mitochondria-targeted near-infrared(NIR)cyanines are excellent therapeutic photosensitizers of cancer.However,most mitochondria-targeted cyanines exist in the form of hydrophobic structures,which in vivo may cause cyanine aggregation during blood circulation,resulting in poor biocompatibility and limited therapeutic efficacy.Therefore,we developed a trade-off strategy by encapsulating mitochondria-targeted cyanines into liposomal bilayers(CyBI7-LPs),which balanced hydrophilicity that favored blood circulation and hydrophobicity that enhanced mitochondria tumor targeting.Moreover,CyBI7-LPs greatly minimized photobleaching of cyanine as self-generated reactive oxygen species(ROS)could rapidly escape from the liposomal bilayer,affording enhanced PTT/PDT efficacy.Bioorthogonal-mediated targeting strategy was further employed to improve uptake of tumor cells by modifying the liposomal surface to generate CyBI7-LPB.The CyBI7-LPB probe produced a tumor-to-background ratio(TBR)of approximately 6.4 at 24 HPI.Guiding by highly sensitive imaging resulted in excellent anti-tumor therapy outcomes using CyBI7-LPB due to the enhanced photothermal and photodynamic effects.This proposed liposomal nanoplatform exhibited a simple and robust approach as an imaging-guided synergistic anti-tumor therapeutic strategy.

NIR-Ⅱabsorbing organic nanoagents for photoacoustic imaging and photothermal therapy

Near-infrared(NIR)absorbing materials hold great potential in biomedical applications,such as fluorescence imaging(FLI),photoacoustic imaging(PAI),photodynamic therapy(PDT),and photothermal therapy(PTT).Generally,these materials can be classified into two main categories based on their absorbing wavelengths:the first NIR(NIR-I)(~650–950 nm)absorbing materials and the second NIR(NIR-Ⅱ)(~1000–1700 nm)absorbing materials.Due to the reduced absorption and scattering of NIR-Ⅱlight in tissue compared to NIR-Ⅰlight,NIR-Ⅱabsorbing materials enable imaging and therapy with improved contrast and deepened penetration,which is in favor of practical applications.Various inorganic materials have been developed for NIR-Ⅱphototheranostics in recent years.However,the non-biodegradability and potential toxicity of these materials hinder their further clinical trans-lation.Biocompatible organic materials with potential biodegradability as well as tailored optical property are thus more desired.In this review,we sum-marize the recent advances of NIR-Ⅱabsorbing organic nanoagents(ONAs)based on small molecules(SMs)and conjugated polymers(CPs)for PAI and PTT and show our perspectives on future challenges and development of these materials.