Highly Stable Organic Small Molecular Nanoparticles as an Advanced and Biocompatible Phototheranostic Agent of Tumor in Living Mice

Novel BODIPY-based nano-biomaterials with enhanced D-A-D structure for NIR-triggered photodynamic and photothermal therapy

Near-infrared (NIR) responsive nanoparticles are an important platform for multimodal phototherapy. Importantly, the simultaneous NIR-triggered photodynamic (PDT) and photothermal (PTT) therapy is a powerful approach to increase the antitumor efficiency of phototherapic nanoparticles due to the synergistic effect. Herein, a boron dipyrromethene (BODIPY)-based amphiphilic dye with enhanced electron donor-acceptor-donor (D-A-D) structure (BDP-AP) was designed and synthesized, which could self-assemble into stable nanoparticles (BDP-AP NPs) for the synergistic NIR-triggered PDT/PTT therapy. BDP-AP NPs synchronously generated singlet oxygen (1O2) and achieved preeminent photothermal conversion efficiency (61.42%). The in vitro and in vivo experiments showed that BDP-AP NPs possessed negligible dark cytotoxicity and infusive anticancer performance. BDP-AP NPs provide valuable guidance for the construction of PDT/PTT-synergistic NIR nanoagents to improve the efficiency of photoinduced cancer therapy in the future.

Tailored Phototherapy Agent by Infection Site In Situ Activated Against Methicillin-Resistant S. aureus

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is a promising treatment approach for multidrug resistant infections. PDT/PTT combination therapy can more efficiently eliminate pathogens without drug resistance. The key to improve the efficacy of photochemotherapy is the utilization efficiency of non-radiation energy of phototherapy agents. Herein, a facile phototherapy molecule (SCy-Le) with the enhancement of non-radiative energy transfer is designed by an acid stimulation under a single laser. Introduction of the protonated receptor into SCy-Le results in a distorted intramolecular charge in the infected acidic microenvironment, pH ≈ 5.5, which in turn, enhances light capture, reduces the singlet-triplet transition energies (ΔES1-T1), promotes electron system crossing, enhances capacity of reactive oxygen species generation, and causes a significant increase in temperature by improving vibrational relaxation. SCy-Le shows more than 99% bacterial killing rate against both methicillin-resistant Staphylococcus aureus and its biofilms in vitro and causes bacteria-induced wound healing in mice. This work will provide a new perspective for the design of phototherapy agents, and the emerging photochemotherapy will be a promising approach to combat the problem of antibiotic resistance.

Nanoparticles as carriers of photosensitizers to improve photodynamic therapy in cancer

Photodynamic therapy (PDT) has emerged as a promising non invasive therapeutic approach for cancer treatment, offering unique advantages over conventional treatments. The combination of light activation and photosensitizing agents allows for targeted and localized destruction of cancer cells, reducing damage to surrounding healthy tissues. In recent years, the integration of nanoparticles with PDT has garnered significant attention due to their potential to enhance therapeutic outcomes. This review article aims to provide a comprehensive overview of the current state-of-the-art in utilizing nanoparticles for photodynamic therapy in cancer treatment. We summarized various nanoparticle-based approaches, their properties, and their implications in optimizing PDT efficacy, and discussed challenges and prospects in the field.

Melanin-Inspired Composite Materials: From Nanoarchitectonics to Applications

Synthetic melanin is a mimic of natural melanin analogue with intriguing properties such as metal-ion chelation, redox activity, adhesion, and broadband absorption. Melanin-inspired composite materials are formulated by assembly of melanin with other types of inorganic and organic components to target, combine, and build up the functionality, far beyond their natural capabilities. Developing efficient and universal methodologies to prepare melanin-based composite materials with unique functionality is vital for their further applications. In this review, we summarize three types of synthetic approaches, predoping, surface engineering, and physical blending, to access various melanin-inspired composite materials with distinctive structure and properties. The applications of melanin-inspired composite materials in free radical scavenging, bioimaging, antifouling, and catalytic applications are also reviewed. This review also concludes current challenges that must be addressed and research opportunities in future studies.

Porphyrin Derivative with Binary Properties of Photodynamic Therapy and Water-Dependent Reversible Photoacidity Therapy for Treating Hypoxic Tumor

Porphyrin photosensitizers are the classic drugs in clinical photodynamic therapy (PDT), but the hypoxia of tumor environment and the rapid oxygen consumption of PDT severely weaken their therapeutic effect. A recently reported water-dependent reversible photoacidity therapy (W-RPAT) is O2 -independence, providing a solution for the treatment of hypoxic tumors. In this work, TPP-O-PEG5, a porphyrin derivative with binary properties of PDT and W-RPAT, is designed and synthesized for the first time. The nanoparticles (NPs) of TPP-O-PEG5 encapsulated with DSPE-mPEG2000, an amphiphilic polymer approved by Food and Drug Administration, can simultaneously produce reactive oxygen species and H+ under irradiation of a 660 nm laser, and revert the H+ back under darkness, presenting strong phototoxicity to multiple tumor cell lines with no obvious difference between the IC50 values tested under normoxic (≈20% O2 ) and hypoxic (<0.5% O2 ) conditions. Excitingly, in vivo experiments show that the therapeutic effect of TPP-O-PEG5 NPs on large hypoxic tumors is better than that of NPe6, a clinical porphin PDT drug. This work provides a novel strategy for porphyrin photosensitizers to break through the limitation of hypoxic environment, and significantly improve the phototherapeutic effect on hypoxic tumors.

Reconstituting Low-Density Lipoprotein with NIR-Absorbing Organic Photothermal Agents for Targeted Killing of Cancer Cells

Photothermal therapy (PTT) systems typically do not possess intrinsic tumor-targeting capability, resulting in indiscriminate thermal damage to both cancer and normal cells. Herein, a low-density lipoprotein (LDL)-based nanosystem (denoted as MTTQ@LDL) is reported for targeted photothermal killing of cancer cells. Such a nanosystem is fabricated by reconstituting the lipophilic core of LDL with an organic photothermal agent MTTQ. The reconstitution process improves the supramolecular photothermal effects of MTTQ assemblies, which contributes to the significantly enhanced photothermal conversion efficiency (41.3% vs. 16.2%). MTTQ@LDL can actively target LDL receptor-overexpressed cancer cells via receptor-mediated endocytosis, enabling the selective killing of cancer cells over normal cells (98% vs. 7%) post-NIR irradiation. Reconstituted LDL can serve as a promising platform for targeted delivery of functional materials, holding great promise in tumor eradication in vivo.

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

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

Enhanced photothermal therapy performance of D-A conjugated polymers based on [1,2,3]triazolo[4,5-g]quinoxaline by manipulating molecular motion

Donor-acceptor (D-A) conjugated polymers can favor the nonradiative thermal dissipation process, due to the formation of an intramolecular charge transfer (ICT) state resulting from the electron cloud delocalization of the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital). Thus, to realize a high extinction coefficient and excellent photothermal conversion ability for a single photothermal agent, donor-acceptor type conjugated polymers PBDT-QTz and PCDT-QTz, comprising a new electron-deficient unit 2-(2-decyltetradecyl)-6,7-dimethyl-2H-[1,2,3]triazolo [4,5-g] quinoxaline (QTz) as the acceptor and 4,8-di(thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene (BDT) or 4H-cyclopenta[2,1-b:3,4-b'] dithiophene (CDT) as the donor, are designed and synthesized by manipulating intramolecular motion. The high extinction coefficient of 28.5 L g-1 cm-1 at 850 nm and the optimal photothermal conversion efficiency of 64.3% under an 808 nm laser are achieved based on PBDT-QTz. Consequently, PBDT-QTz nanoparticles can be successfully used for both in vitro and in vivo experiments. After intravenous administration and 808 nm laser irradiation, HeLa tumor-bearing mice achieve complete tumor remission without recurrence. The results provide an efficient photothermal agent by manipulating molecular motion.

Synthesis and properties of novel type I photosensitizer polycyclic amide

Herein, we have designed and synthesized a novel type-I photosensitizer (PhPA) via Rh-catalyzed oxidative cyclization of diacetoxyterephthalamide with alkynes. The photoelectric properties, photosensitivity and photodegradation process of PhPA have been systematically investigated. The remarkable fluorescence quenching effect (Φ_PL < 0.01) of PhPA suggests that the intersystem crossing from the singlet excited state to the reactive triplet state is enhanced by the enlarged conjugated backbone. Additionally, the ability of superoxide radical (O₂^-˙) generation was confirmed by electron paramagnetic resonance spectroscopy. Finally, the mechanism of PhPA photo-oxidative degradation via the structure of two metabolites is proposed.

Mitochondria-Targeted Fluorescent Nanoparticles with Large Stokes Shift for Long-Term BioImaging

Mitochondria (MITO) play a significant role in various physiological processes and are a key organelle associated with different human diseases including cancer, diabetes mellitus, atherosclerosis, Alzheimer's disease, etc. Thus, detecting the activity of MITO in real time is becoming more and more important. Herein, a novel class of amphiphilic aggregation-induced emission (AIE) active probe fluorescence (AC-QC nanoparticles) based on a quinoxalinone scaffold was developed for imaging MITO. AC-QC nanoparticles possess an excellent ability to monitor MITO in real-time. This probe demonstrated the following advantages: (1) lower cytotoxicity; (2) superior photostability; and (3) good performance in long-term imaging in vitro. Each result of these indicates that self-assembled AC-QC nanoparticles can be used as effective and promising MITO-targeted fluorescent probes.

Core-satellite nanoreactors based on cationic photosensitizer modified hollow CuS nanocage for ROS diffusion enhanced phototherapy of hypoxic tumor

Photodynamic therapy (PDT) efficiency is directly affected by the reactive oxygen species (ROS) generated by photosensitizers. However, ROSs' ultrashort life span and limited diffusion distance restrict the PDT efficiency. Therefore, it is important to control the delivery strategy of photosensitizers for PDT treatment. Herein, the core-satellite nanoreactors were fabricated with oxygen generation and ROS diffusion properties. The hollow CuS encapsulating horseradish peroxidase (HRP) was combined with the cationic photosensitizers (PEI-Ce6). The unique photosensitizers delivery strategy makes the nanoreactors achieve ROS diffusion-enhanced PDT effect. First, HRP in "core" (HRP@CuS) can decompose hydrogen peroxide (H₂O₂) to O₂, increasing O₂ levels on the surface of the nanoreactor. Second, the Ce6 molecules covalent-linked with PEI are uniformly dispersed on the surface of CuS as a "satellite", avoiding Ce6 aggregation and causing more Ce6 molecules be activated to produce more ¹O₂. Due to the Ce6 was on the surface of the CuS nanocages, the generated ROS may ensure a larger diffusion range. Meanwhile, the inherently CuS nanocages exhibit photothermal and photoacoustic (PA) effect. The photothermal effect further enhances the ROS diffusion. Under the guidance of PA imaging, nanoreactors exhibit highly efficient hypoxic tumor ablation via photodynamic and photothermal effect. Overall, the core-satellite nanoreactors provide an effective strategy for tumor therapy, further promoting the research of photosensitizers delivery.

De Novo Design of Activatable Photoacoustic/Fluorescent Probes for Imaging Acute Lung Injury In Vivo

Effective monitoring of the physiological progression of acute lung injury (ALI) in real time is crucial for early theranostics to reduce its high mortality. In particular, activatable fluorescence and photoacoustic molecule probes have attracted attention to assess ALI by detecting related indicators. However, the existing fluorophores often encounter issues of low retention in the lungs and slow clearance from the body, which compromise the probe's actual capability for in situ imaging by intravenous injection in vivo. Herein, a novel near-infrared hemicyanines fluorophore (FJH) bearing a quaternary ammonium group was first developed by combining with the rational design and screening strategy. The properties of good hydrophilicity and blood circulation effectively enable FJH accumulation for lung imaging. Inspired by the high retention efficiency, the probe FJH-C that turns on fluorescence and photoacoustic signals in response to the ALI indicator (esterase) was subsequently synthesized. Notably, the probe FJH-C successfully achieved the selectivity and sensitivity toward esterase in vitro and in living cells. More importantly, FJH-C can be further used to assess lipopolysaccharides and silica-induced ALI through the desired fluo-photoacoustic signal. Therefore, this study not only shows the first activatable probe for real-time imaging of lung function but also highlights the fluorophore structure with high lung retention. It is believed that FJH and FJH-C can serve as an efficient platform to reveal the pathological progression of other lung diseases for early diagnosis and medical intervention.

Surfactant-chaperoned donor-acceptor-donor NIR-II dye strategy efficiently circumvents intermolecular aggregation to afford enhanced bioimaging contrast

Fluorescence emission in the near-infrared-II (NIR-II) optical window affords reduced autofluorescence and light scattering, enabling deep-tissue visualization for both disease detection and surgical navigation. Small-molecule NIR-II dyes are preferable for clinical bioimaging applications, as the flexibility in their molecular synthesis allows for precise control of their optical and pharmacokinetic properties. Among the various types of dye, donor-acceptor-donor-based (D-A-D) dyes demonstrate exceptional photostability, whereas the frequently used PEGylation approach does not keep their intrinsic brightness enough in water environments due to their inherent effect of self-assembly. Here, we demonstrate that the commercially-available surfactants can serve as a dispersant to prevent molecular aggregation of PEGylated D-A-D dyes. Due to the favorable energetics for co-assembly between D-A-D dyes and surfactants, the formed surfactant-chaperoned dye strategy dramatically increases dye brightness. Accordingly, this effect provides remarkably improved performance for in vivo bioimaging applications. In parallel, we also investigate the D-A-D dye uptake and signal enhancement properties in the liver of murine models and demonstrate that the lumen-lining Kupffer cells can potentially disassemble PEGylated D-A-D aggregates such that their inherent brightness is restored. This phenomenon is similar to the surfactant-chaperoned dye strategy and our investigations provide a positive addition to better use of the current NIR-II fluorophores, especially for visualizing high-brightness required events.

NIR-II AIEgens with Photodynamic Effect for Advanced Theranostics

Phototheranostics that concurrently integrates accurate diagnosis (e.g., fluorescence and photoacoustic (PA) imaging) and in situ therapy (e.g., photodynamic therapy (PDT) and photothermal therapy (PTT)) into one platform represents an attractive approach for accelerating personalized and precision medicine. The second near-infrared window (NIR-II, 1000-1700 nm) has attracted considerable attention from both the scientific community and clinical doctors for improved penetration depth and excellent spatial resolution. NIR-II agents with a PDT property as well as other functions are recently emerging as a powerful tool for boosting the phototheranostic outcome. In this minireview, we summarize the recent advances of photodynamic NIR-II aggregation-induced emission luminogens (AIEgens) for biomedical applications. The molecular design strategies for tuning the electronic bandgaps and photophysical energy transformation processes are discussed. We also highlight the biomedical applications, such as image-guided therapy of both subcutaneous and orthotopic tumors, and multifunctional theranostics in combination with other treatment methods, including chemotherapy and immunotherapy; and the precise treatment of both tumor and bacterial infection. This review aims to provide guidance for PDT agents with long-wavelength emissions to improve the imaging precision and treatment efficacy. We hope it will provide a comprehensive understanding about the chemical structure-photophysical property-biomedical application relationship of NIR-II luminogens.

Reactive Species-Activatable AIEgens for Biomedical Applications

Precision medicine requires highly sensitive and specific diagnostic strategies with high spatiotemporal resolution. Accurate detection and monitoring of endogenously generated biomarkers at the very early disease stage is of extensive importance for precise diagnosis and treatment. Aggregation-induced emission luminogens (AIEgens) have emerged as a new type of excellent optical agents, which show great promise for numerous biomedical applications. In this review, we highlight the recent advances of AIE-based probes for detecting reactive species (including reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), and reactive carbonyl species (RCS)) and related biomedical applications. The molecular design strategies for increasing the sensitivity, tuning the response wavelength, and realizing afterglow imaging are summarized, and theranostic applications in reactive species-related major diseases such as cancer, inflammation, and vascular diseases are reviewed. The challenges and outlooks for the reactive species-activatable AIE systems for disease diagnostics and therapeutics are also discussed. This review aims to offer guidance for designing AIE-based specifically activatable optical agents for biomedical applications, as well as providing a comprehensive understanding about the structure-property application relationships. We hope it will inspire more interesting researches about reactive species-activatable probes and advance clinical translations.

A water-dependent reversible photoacidity strategy for cancer treatment

In the reported mechanisms of reversible photoacidity, protons were dissociated from compounds which contained hydroxyl, indazole or formed hydroxyl via intramolecular hydrogen abstraction under irradiation. Herein, a water-dependent reversible photoacidity (W-RPA) mechanism mediated by a thiadiazoloquinoxaline compound (TQs-Th-PEG5) has been found, in which the proton is not dissociated from TQs-Th-PEG5 itself but from a water locked by TQs-Th-PEG5 under the irradiation of a 660 nm laser. After turning off the laser, the produced acid will disappear quickly. This process is repeatable with no consumption of TQs-Th-PEG5. More importantly, water is indispensable. Furthermore, it is confirmed that there is no other element involved in the process except TQs-Th-PEG5, light and water. Excitingly, W-RPA therapy mediated by TQs-Th-PEG5 nanoparticle exhibits remarkable antitumor effect both in vitro and in vivo, especially in hypoxic tumors with diameter larger than 10 mm owing to its oxygen-independent feature. This study not only discovers a W-RPA mechanism but also provides a novel phototherapy strategy for cancer treatment.

Magnetic-targeted capacitive heterostructure of polypyrrole for hypoxia-tolerant synergistic photodynamic/photothermal therapy under near infrared excitation

Dual/Multi-modal photonanomedicines with the maximized antitumor efficacy has attracted extensive concerning. In this contribution, through photovoltaic engineering of photothermal conjugated polymer, a facile magnetic-targeted capacitive heterostructure of polypyrrole (upconversion nanoparticles (UCNPs)@SiO₂-Fe₃O₄ @polypyrrole (USFP)), capable of photodynamic therapy (PDT) and photothermal therapy (PTT) upon near infrared (NIR) excitation is purposefully developed. Owing to the optimized regulation of photoreaction pathway via photoinduced capacitance effect, the yield of reactive oxygen species (ROS) including ¹O₂ in polypyrrole can be significantly promoted. Notably, the external layers (porous silica and polypyrrole) of USFP allow the encounter and subsequent Fenton reaction between Fe₃O₄ and H₂O₂ in tumor site, thereby further enhancing the photodynamic effect via an effective O₂ supply. Upon intravenous injection into tumor-bearing mice, USFP can accumulate in tumors through a magnetic guidance, ablation experiments in vitro and in vivo confirmed the enhanced synergistic therapeutic effect and desirable biocompatibility of USFP.

Advances in Hybrid Vesicular-based Drug Delivery Systems: Improved Biocompatibility, Targeting, Therapeutic Efficacy and Pharmacokinetics of Anticancer Drugs

Anticancer drugs and diagnostics can be transported in nanoscale vesicles that provide a flexible platform. A hybrid nanoparticle, a nano assembly made up of many types of nanostructures, has the greatest potential to perform these two activities simultaneously. Nanomedicine has shown the promise of vesicular carriers based on lipopolymersomes, lipid peptides, and metallic hybrid nano-vesicle systems. However, there are significant limitations that hinder the clinical implementation of these systems at the commercial scale, such as low productivity, high energy consumption, expensive setup, long process durations, and the current cancer therapies described in this article. Combinatorial hybrid systems can be used to reduce the above limitations. A greater therapeutic index and improved clinical results are possible with hybrid nanovesicular systems, which integrate the benefits of many carriers into a single structure. Due to their unique properties, cell-based drug delivery systems have shown tremendous benefits in the treatment of cancer. Nanoparticles (NPs) can benefit significantly from the properties of erythrocytes and platelets, which are part of the circulatory cells and circulate for a long time. Due to their unique physicochemical properties, nanomaterials play an essential role in cell-based drug delivery. Combining the advantages of different nanomaterials and cell types gives the resulting delivery systems a wide range of desirable properties. NPs are nextgeneration core-shell nanostructures that combine a lipid shell with a polymer core. The fabrication of lipid-polymer hybrid NPs has recently undergone a fundamental shift, moving from a two-step to a one-step technique based on the joint self-assembly of polymers and lipids. Oncologists are particularly interested in this method as a combinatorial drug delivery platform because of its two-in-one structure. This article addresses various preparative methods for the preparation of hybrid nano-vesicular systems. It also discusses the cellular mechanism of hybrid nano-vesicular systems and describes the thorough knowledge of various hybrid vesicular systems.

Photothermal agents based on small organic fluorophores with intramolecular motion

Photothermal therapy (PTT) has attracted great attention due to its noninvasive and low side effects. Photothermal agents (PTAs) which could convert absorbing light into heat play a critical role in PTT. For conventional small organic PTAs, the photothermal conversion ability is mainly achieved by intermolecular noncovalent interactions such as π-π interactions. However, in terms of organic fluorophores with rotator or vibrator segments, the balance between fluorescence emission and heat generation is mainly regulated by intramolecular motions which could be mediated by molecular engineering. Following this designing principle, various fluorophores with intramolecular motions for effective PTT have been reported. In this review, we highlight the recent progress of PTAs based on small organic fluorophores with intramolecular motions for enhanced PTT. Designing tactics of these fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation capability are emphasized. Finally, one-for-all phototheranostics achieved by mediating intramolecular motions of these fluorophores are highlighted. We hope this review could pave a new avenue to developing fluorophores with intramolecular motion as PTAs to advance their clinical transition. STATEMENT OF SIGNIFICANCE: Recent progress of photothermal agents (PTAs) based on small organic fluorophores with intramolecular motion is summarized in this review. Molecular engineering of these small organic fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation at tumor sites for enhanced photothermal therapy (PTT) is highlighted. Strategies to tune the intramolecular motions of these fluorophores to achieve multimodal phototherapy are emphasized as well.

Acceptor engineering for NIR-II dyes with high photochemical and biomedical performance

It is highly important and challenging to develop donor-acceptor-donor structured small-molecule second near-infrared window (NIR-II) dyes with excellent properties such as water-solubility and chem/photostability. Here, we discovery an electron acceptor, 6,7-di(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-g]quinoxaline (TQT) with highest stability in alkaline conditions, compared with conventional NIR-II building block benzobisthiadiazole (BBT) and 6,7-diphenyl-[1,2,5] thiadiazolo[3,4-g]quinoxaline (PTQ). The sulfonated hydrophilic dye, FT-TQT, is further synthesized with 2.13-fold increased quantum yield than its counterpart FT-BBT with BBT as acceptor. FT-TQT complexed with FBS is also prepared and displays a 16-fold increase in fluorescence intensity compared to FT-TQT alone. It demonstrates real-time cerebral and tumor vessel imaging capability with µm-scale resolution. Dynamic monitoring of tumor vascular disruption after drug treatment is achieved by NIR-II fluorescent imaging. Overall, TQT is an efficient electron acceptor for designing innovative NIR-II dyes. The acceptor engineering strategy provides a promising approach to design next generation of NIR-II fluorophores which open new biomedical applications.

Small molecule NIR-II fluorophores are of interest for a range of applications but can suffer from chemical and photostability issues. Here, the authors report on the development of an acceptor molecule with improved stability in alkaline conditions expanding the range of possible applications.

Looking deep inside tissue with photoacoustic molecular probes: a review

Significance

Deep tissue noninvasive high-resolution imaging with light is challenging due to the high degree of light absorption and scattering in biological tissue. Photoacoustic imaging (PAI) can overcome some of the challenges of pure optical or ultrasound imaging to provide high-resolution deep tissue imaging. However, label-free PAI signals from light absorbing chromophores within the tissue are nonspecific. The use of exogeneous contrast agents (probes) not only enhances the imaging contrast (and imaging depth) but also increases the specificity of PAI by binding only to targeted molecules and often providing signals distinct from the background.

Aim

We aim to review the current development and future progression of photoacoustic molecular probes/contrast agents.

Approach

First, PAI and the need for using contrast agents are briefly introduced. Then, the recent development of contrast agents in terms of materials used to construct them is discussed. Then, various probes are discussed based on targeting mechanisms, in vivo molecular imaging applications, multimodal uses, and use in theranostic applications.

Results

Material combinations are being used to develop highly specific contrast agents. In addition to passive accumulation, probes utilizing activation mechanisms show promise for greater controllability. Several probes also enable concurrent multimodal use with fluorescence, ultrasound, Raman, magnetic resonance imaging, and computed tomography. Finally, targeted probes are also shown to aid localized and molecularly specific photo-induced therapy.

Conclusions

The development of contrast agents provides a promising prospect for increased contrast, higher imaging depth, and molecularly specific information. Of note are agents that allow for controlled activation, explore other optical windows, and enable multimodal use to overcome some of the shortcomings of label-free PAI.

A supramolecular photosensitizer derived from an Arene-Ru(II) complex self-assembly for NIR activated photodynamic and photothermal therapy

Effective photosensitizers are of particular importance for the widespread clinical utilization of phototherapy. However, conventional photosensitizers are usually plagued by short-wavelength absorption, inadequate photostability, low reactive oxygen species (ROS) quantum yields, and aggregation-caused ROS quenching. Here, we report a near-infrared (NIR)-supramolecular photosensitizer (RuDA) via self-assembly of an organometallic Ru(II)-arene complex in aqueous solution. RuDA can generate singlet oxygen (¹O₂) only in aggregate state, showing distinct aggregation-induced ¹O₂ generation behavior due to the greatly increased singlet-triplet intersystem crossing process. Upon 808 nm laser irradiation, RuDA with excellent photostability displays efficient ¹O₂ and heat generation in a ¹O₂ quantum yield of 16.4% (FDA-approved indocyanine green: Φ_Δ = 0.2%) together with high photothermal conversion efficiency of 24.2% (commercial gold nanorods: 21.0%, gold nanoshells: 13.0%). In addition, RuDA-NPs with good biocompatibility can be preferably accumulated at tumor sites, inducing significant tumor regression with a 95.2% tumor volume reduction in vivo during photodynamic therapy. This aggregation enhanced photodynamic therapy provides a strategy for the design of photosensitizers with promising photophysical and photochemical characteristics.

Novel Glutathione Activated Smart Probe for Photoacoustic Imaging, Photothermal Therapy, and Safe Postsurgery Treatment

Preventing tumor recurrence is the most important target for cancer treatment. However, the current effective and advanced technology relies on the use of near-infrared region (NIR), and the equipment of NIR-I and NIR-II fluorescence imaging technique-based fluorescent-guided surgery is expensive and complicated to operate. Here, we report a safe and effective strategy of an organic-inorganic hybrid gold nanoparticle-based novel smart probe (Au@PDA-ss-PEGm NPs) which is appropriate for photoacoustic imaging (PAI) and plasmonic photothermal therapy (PPTT) of tumors in vivo. After intravenous injection, the probe would be transported to the tumor to penetrate the cellular membrane. Then the disulfide bond on the probe surface would be broken with the help of a high concentration of glutathione in the tumor cell. The remaining Au@PDA NPs would aggregate to form plasmonic nanoclusters and exhibit a notable plasmon coupling enhanced photothermal (PCEPT) effect. Besides, the results further proved its good biosafety and pharmacokinetic characteristics in vivo and, more important, a short time exposure under 808 nm laser after surgical removal of the tumor, which would be effective to prevent tumor recurrence and bring dawn to the high-efficiency treatment of tumors.

AIEgen-Based Bionic Nanozymes for the Interventional Photodynamic Therapy-Based Treatment of Orthotopic Colon Cancer

Relative to traditional photosensitizer (PS) agents, those that exhibit aggregation-induced emission (AIE) properties offer key advantages in the context of photodynamic therapy (PDT). At present, PDT efficacy is markedly constrained by the hypoxic microenvironment within tumors and the limited depth to which lasers can penetrate in a therapeutic context. Herein, we developed platelet-mimicking MnO2 nanozyme/AIEgen composites (PMD) for use in the interventional PDT treatment of hypoxic tumors. The resultant biomimetic nanoparticles (NPs) exhibited excellent stability and were able to efficiently target tumors. Moreover, they were able to generate O2 within the tumor microenvironment owing to their catalase-like activity. Notably, through an interventional approach in which an optical fiber was introduced into the abdominal cavity of mice harboring orthotopic colon tumors, good PDT efficacy was achieved. We thus propose that a novel strategy consisting of a combination of an AIEgen-based bionic nanozyme and a biomimetic cell membrane coating represents an ideal therapeutic platform for targeted antitumor PDT. This study is the first to have combined interventional therapy and AIEgen-based PDT, thereby overcoming the limited light penetration that typically constrains the therapeutic efficacy of this technique, highlighting a promising new AIEgen-based PDT treatment strategy.

Azulene-Containing Squaraines for Photoacoustic Imaging and Photothermal Therapy

Photoacoustic imaging (PAI) guided photothermal therapy (PTT) can realize real-time diagnosis and in situ treatment of cancer at the same time. Absorption in the near-infrared (NIR) region with large molar extinction coefficient (ε) and high value of photothermal conversion efficiency (PCE) are key prerequisites for photothermal agents (PTAs) to realize dual PAI and PTT treatments. Squaraines have stable quinoid structures with strong planarity and rigidity, in favor of the NIR absorption and high ε values. On the other hand, azulene derivatives mostly have very faint fluorescence emission, which is beneficial for photothermal transformation. Herein, two azulene-containing squaraines Az-SQ-1 and Az-SQ-2 are synthesized as high-performance PTAs. In comparison with Az-SQ-1, Az-SQ-2 possesses larger ε_max of 3 × 10⁵ M^-1 cm^-1 at 780 nm in organic solution and higher PCE of 53.2% in the form of nanoparticles under 808 nm laser irradiation. Accordingly, Az-SQ-2 NPs present stronger photoacoustic signals (about 15.1-times the background signal) and more efficient suppression of tumor growth. Our research indicates that the introduction of azulene unit to traditional NIR dyes is a simple but effective approach to obtain outstanding PTAs in the aspect of phototheranostics.

Evoking Highly Immunogenic Ferroptosis Aided by Intramolecular Motion-Induced Photo-Hyperthermia for Cancer Therapy

Immunogenic cell death (ICD) through apoptosis or necroptosis is widely adopted to improve the therapeutic effect in cancer treatment by triggering a specific antitumor immunity. However, the tumor resistance to apoptosis/necroptosis seriously impedes the therapeutic effect. Recently, ferroptosis featured with excessive lipid peroxidation is demonstrated capable of bypassing the apoptosis/necroptosis resistance to kill cancer cells. To date, numerous efficient ferroptosis inducers are developed and successfully utilized for sensitizing cancer cells to ferroptosis. Unfortunately, these inducers can hardly generate adequate immunogenicity during induction of ferroptotic cancer cell death, which distinctly attenuates the efficacy of triggering antitumor immune response, therefore leads to unsatisfactory therapeutic effect. Herein, a novel high-performance photothermal nanoparticle (TPA-NDTA NP) is designed by exploiting energy via excited-state intramolecular motion and employed for immensely assisting ferroptosis inducer to evoke highly efficient ICD through ferroptosis pathway. Tumor models with poor immunogenicity are used to demonstrate the tremendously enhanced therapeutic effect endowed by highly enhanced immunogenic ferroptosis in vitro and in vivo by virtue of the NPs. This study sheds new light on a previously unrecognized facet of boosting the immunogenicity of ferroptosis for achieving satisfactory therapeutic effect in cancer therapy.

Multimodal Imaging-Guided Photothermal Immunotherapy Based on a Versatile NIR-II Aggregation-Induced Emission Luminogen

Synergistic photothermal immunotherapy has captured great attention owing to the mutually strengthening therapeutic outcomes towards both original tumors and abscopal tumors. Herein, a versatile theranostic agent displaying aggregation-induced emission, namely TPA-BT-DPTQ, was designed and prepared based on benzo[c]thiophene unit as a building block; it can be used for simultaneous fluorescence imaging (FLI) in the second near-infrared (NIR-II) window, photoacoustic imaging (PAI), photothermal imaging (PTI), and thermal eradication of tumors. Further experiments validate that photothermal therapy (PTT) mediated by TPA-BT-DPTQ nanoparticles not only destroys the primary tumor but also enhances immunogenicity for further suppressing the growth of tumors at distant sites. Furthermore, PTT combining a programmed death-ligand 1 (PD-L1) antibody prevents the metastasis and recurrence of cancer by potentiating the effect of immunotherapy.

NIR-II Aggregation-Induced Emission Luminogens for Tumor Phototheranostics

As an emerging and powerful material, aggregation-induced emission luminogens (AIEgens), which could simultaneously provide a precise diagnosis and efficient therapeutics, have exhibited significant superiorities in the field of phototheranostics. Of particular interest is phototheranostics based on AIEgens with the emission in the range of second near-infrared (NIR-II) range (1000-1700 nm), which has promoted the feasibility of their clinical applications by virtue of numerous preponderances benefiting from the extremely long wavelength. In this minireview, we summarize the latest advances in the field of phototheranostics based on NIR-II AIEgens during the past 3 years, including the strategies of constructing NIR-II AIEgens and their applications in different theranostic modalities (FLI-guided PTT, PAI-guided PTT, and multimodal imaging-guided PDT-PTT synergistic therapy); in addition, a brief conclusion of perspectives and challenges in the field of phototheranostics is given at the end.

Self-assembled porphyrin polymer nanoparticles with NIR-II emission and highly efficient photothermal performance in cancer therapy

The development of new organic nanoagents with extremely high photothermal conversion efficiency and good biocompatibility has gained considerable attention in the area of photothermal cancer therapy. In this work, we designed and synthesized a new porphyrin polymer (P-PPor) with donor-acceptor (D-A) structure. P-PPor displayed intense absorbance in the near-infrared (NIR) region with the maximum peak around at 850 ​nm. Under excitation of 808 ​nm, P-PPor demonstrated the significant fluorescence in the NIR-II region (λ _max ​= ​1015 ​nm), with the fluorescence quantum yield of 2.19%. Due to the presence of hydrophilic PEG chains and hydrophobic alkyl chains in the conjugated skeleton, the amphiphilic P-PPor could self-assemble into the nanoparticles (P-PPor NPs) with good dispersibility in water and enhanced absorption in the NIR region. Moreover, P-PPor NPs exhibited quenched fluorescence because of the aggregation-caused quenching (ACQ) effect, resulting in the distinct photothermal effect. The photothermal conversion efficiency (PCE) of P-PPor NPs was measured as 66% under 808 ​nm laser irradiation, higher than most of PTT agents. The remarkable photothermal effect of P-PPor NPs was further demonstrated in vitro and in vivo using 4T1 tumor mode. Meanwhile, the NIR-II fluorescence imaging in vivo indicated the high distribution of P-PPor NPs in tumor site. These results suggested that P-PPor NPs could effectively damage the cancer cells in mice under 808 ​nm laser irradiation, and did not cause any obvious side effects after phototherapy. Thus, P-PPor NPs could be used as a potential agent in photothermal cancer therapy with high effectiveness and safety.

Lipids coated CaCO3-PDA nanoparticles as a versatile nanocarrier to enable pH-responsive dual modal imaging guided combination cancer therapy

Development of an intelligent and versatile delivery system to achieve tumor targeted delivery and controlled release of diverse functional moieties is of great significance to realize precise cancer theranostics. In...

Near-infrared light-triggered nano-prodrug for cancer gas therapy

Gas therapy (GT) has attracted increasing attention in recent years as a new cancer treatment method with favorable therapeutic efficacy and reduced side effects. Several gas molecules, such as nitric oxide (NO), carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S) and sulfur dioxide (SO2), have been employed to treat cancers by directly killing tumor cells, enhancing drug accumulation in tumors or sensitizing tumor cells to chemotherapy, photodynamic therapy or radiotherapy. Despite the great progress of gas therapy, most gas molecules are prone to nonspecific distribution when administered systemically, resulting in strong toxicity to normal tissues. Therefore, how to deliver and release gas molecules to targeted tissues on demand is the main issue to be considered before clinical applications of gas therapy. As a specific and noninvasive stimulus with deep penetration, near-infrared (NIR) light has been widely used to trigger the cleavage and release of gas from nano-prodrugs via photothermal or photodynamic effects, achieving the on-demand release of gas molecules with high controllability. In this review, we will summarize the recent progress in cancer gas therapy triggered by NIR light. Furthermore, the prospects and challenges in this field are presented, with the hope for ongoing development.

Aggregation-Induced Emission-Based Platforms for the Treatment of Bacteria, Fungi, and Viruses

The prevention and control of pathogenic bacteria, fungi, and viruses is a herculean task for all the countries since they greatly threaten global public health. Rapid detection and effective elimination of these pathogens is crucial for the treatment of related diseases. It is urgently demanded to develop new diagnostic and therapeutic strategies to combat bacteria, fungi, and viruses-induced infections. The emergence of aggregation-induced emission (AIE) luminogens (AIEgens) is a revolutionary breakthrough for the treatment of many diseases, including pathogenic infections. In this review, the main focus is on the applications of AIEgens for theranostic treatment of pathogenic bacteria, fungi, and viruses. Due to the AIE characteristic, AIEgens are promising fluorescent probes for the detection of bacteria, fungi, and viruses with excellent sensitivity and photostability. Moreover, AIEgen-based theranostic platforms can be fabricated by introducing bactericidal moieties or designing AIE photosensitizers and AIE photothermal agents. The current strategies and ongoing developments of AIEgens for the treatment of pathogenic bacteria, fungi, and viruses will be discussed in detail.

Practicable Applications of Aggregation-Induced Emission with Biomedical Perspective

Considerable efforts have been made into developing aggregation-induced emission fluorogens (AIEgens)-containing nano-therapeutic systems due to the excellent properties of AIEgens. Compared to other fluorescent molecules, AIEgens have advantages including low background, high signal-to-noise ratio, good sensitivity, and resistance to photobleaching, in addition to being exempt from concentration quenching or aggregation-caused quenching effects. The present review outlines the major developments in the biomedical applications of AIEgens-containing systems. From a literature survey, the recent AIE works are reviewed and the reasons why AIEgens are chosen in various biomedical applications are highlighted. The research activities on AIEgens-containing systems are increasing rapidly, therefore, the present review is timely.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Boosting Photoacoustic Effect via Intramolecular Motions Amplifying Thermal-to-Acoustic Conversion Efficiency for Adaptive Image-Guided Cancer Surgery

Photoacoustic (PA) imaging emerges as a promising technique for biomedical applications. The development of new strategies to boost PA conversion without depressing other properties (e.g., fluorescence) is highly desirable for multifunctional imaging but difficult to realize. Here, we report a new phenomenon that active intramolecular motions could promote PA signal by specifically increasing thermal-to-acoustic conversion efficiency. The compound with intense intramolecular motion exhibits amplified PA signal by elevating thermal-to-acoustic conversion, and the fluorescence also increases due to aggregation-induced emission signature. The simultaneously high PA and fluorescence brightness of TPA-TQ3 NPs enable precise image-guided surgery. The preoperative fluorescence and PA imaging are capable of locating orthotopic breast tumor in a high-contrast manner, and the intraoperative fluorescence imaging delineates tiny residual tumors. This study highlights a new design guideline of intramolecular motion amplifying PA effect.

Competition between the Photothermal Effect and Emission in Potential Phototherapy Agents

Planar donor-acceptor-donor (D-A-D) organic molecules have been highlighted as promising photothermal agents due to their good light-to-heat conversion ratio, easy degradation, and chemical tunability. Very recently, it has been demonstrated that their photothermal conversion can be boosted by appending rather long alkyl chains. Despite this behavior being tentatively associated with the population of a nonradiative twisted intramolecular charge transfer (TICT) state driven by an intramolecular motion, the precise mechanisms and the role played by the environment, and most notably aggregation, still remain elusive. In this context, we carried out a series of time-dependent density functional theory (TD-DFT) calculations combined with molecular dynamics (MD) simulations to achieve a realistic description of the isolated and aggregated systems. Our theoretical models unambiguously evidence that the population of CT states is very unlikely in both cases, whereas the light-triggered heat dissipation can be ascribed to the activation of specific vibrational degrees of freedom related to the relative motion of the peripheral chains. Overall, our results clearly corroborate the active role played by the alkyl substituents in the photothermal conversion through vibrational motion, while breaking from the conventional picture, which invokes the formation of dark TICT states in loosely packed aggregates.

Bright Bacterium for Hypoxia-Tolerant Photodynamic Therapy Against Orthotopic Colon Tumors by an Interventional Method

While promising, the efficacy of aggregation-induced emission (AIE)-based photodynamic therapy (PDT) is limited by several factors including limited depth of laser penetration and intratumoral hypoxia. In the present study, a novel bacteria-based AIEgen (TBP-2) hybrid system (AE) is developed, that is able to facilitate the hypoxia-tolerant PDT treatment of orthotopic colon tumors via an interventional method. For this approach, an interventional device is initially designed, composed of an optical fiber and an endoscope, allowing for clear visualization of the position of the orthotopic tumor within the abdominal cavity. It is then possible to conduct successful PDT treatment of this hypoxic tumor via laser irradiation, as the TBP-2 is able to generate hydroxyl radicals (•OH) via a type I mechanism within this hypoxic microenvironment. Moreover, this interventional approach is proved to significantly impair orthotopic colon cancer growth and overcame PDT defects. This study is the first report involving such an interventional PDT strategy to knowledge, and it has the potential to complement other treatment modalities while also highlighting novel approaches to the design of hybrid AIEgen systems.

Shuttle-Shape Carrier-Free Platinum-Coordinated Nanoreactors with O2 Self-Supply and ROS Augment for Enhanced Phototherapy of Hypoxic Tumor

The synergistic nanotheranostics of reactive oxygen species (ROS) augment or phototherapy has been a promising method within synergistic oncotherapy. However, it is still hindered by sophisticated design and fabrication, lack of a multimodal synergistic effect, and hypoxia-associated poor photodynamic therapy (PDT) efficacy. Herein, a kind of porous shuttle-shape platinum (IV) methylene blue (Mb) coordination polymer nanotheranostics-loaded 10-hydroxycamptothecin (CPT) is fabricated to address the abovementioned limitations. Our nanoreactors possess spatiotemporally controlled O2 self-supply, self-sufficient singlet oxygen (1O2), and outstanding photothermal effect. Once they are taken up by tumor cells, nanoreactors as a cascade catalyst can efficiently catalyze degradation of the endogenous hydrogen peroxide (H2O2) into O2 to alleviate tumor hypoxia. The production of O2 can ensure enhanced PDT. Subsequently, under both stimuli of external red light irradiation and internal lysosomal acidity, nanoreactors can achieve the on-demand release of CPT to augment in situ mitochondrial ROS and highly efficient tumor ablation via phototherapy. Moreover, under the guidance of near-infrared (NIR) fluorescent imaging, our nanoreactors exhibit strongly synergistic potency for treatment of hypoxic tumors while reducing damages against normal tissues and organs. Collectively, shuttle-shape platinum-coordinated nanoreactors with augmented ROS capacity and enhanced phototherapy efficiency can be regarded as a novel tumor theranostic agent and further promote the research of synergistic oncotherapy.

Thiophene donor for NIR-II fluorescence imaging-guided photothermal/photodynamic/chemo combination therapy

Organic fluorophores/photosensitizers have been widely used in biological imaging and photodynamic and photothermal combination therapy in the first near-infrared (NIR-I) window. However, their applications in the second near-infrared (NIR-II) window are still limited primarily due to low fluorescence quantum yields (QYs). Here, a boron dipyrromethene (BDP) is created as a molecularly engineered thiophene donor unit with high QYs to the redshift. Thiophene insertion initiates substantial redshifts of the absorbance as compared to its counterparts in which iodine is introduced. The fluorescent molecule can be triggered by an NIR laser with a single wavelength, thereby producing emission in the NIR-II windows. Single NIR laser-triggered phototherapeutic nanoparticles (NPs) are developed by encapsulating the BDP and the chemotherapeutic drug docetaxel (DTX) by using a synthetic amphiphilic poly(styrene-co-chloromethyl styrene)-graft-poly(ethylene glycol) functionalized with folic acid (FA). These BDP-T-N-DTX-FA NPs not only show superior solubility and high singlet oxygen QY (Φ_Δ=62%) but also demonstrate single NIR laser-triggered multifunctional characteristics. After intravenous administration of the NPs into 4T1 tumor-bearing mice, the accumulation of the NPs in the tumor showed a high signal-to-background ratio (11.8). Furthermore, 4T1 tumors in mice were almost eradicated by DTX released from the BDP-T-N-DTX-FA NPs under single NIR laser excitation and the combination of photodynamic therapy (PDT) and photothermic therapy (PTT). STATEMENT OF SIGNIFICANCE: The application of organic photosensitizers is still limited primarily due to low fluorescence quantum yields (QYs) in the second near-infrared (NIR-II) window. Here, a boron dipyrromethene (BDP) as a molecularly engineered thiophene donor unit with high QYs to the redshift is created. Phototherapeutic nanoparticles (NPs) are developed by encapsulating the BDP and docetaxel (DTX) using a synthetic amphiphilic poly(styrene-co-chloromethyl styrene)-graft-poly(ethylene glycol) functionalized with folic acid (FA). These BDP-T-N-DTX-FA NPs not only show high singlet oxygen QY (Φ_Δ=62%) but also demonstrate single NIR laser-triggered multifunctional characteristics and a high signal-to-background ratio (11.8). Furthermore, 4T1 tumors in mice were almost eradicated by DTX released from the BDP-T-N-DTX-FA NPs under single NIR laser excitation and the PDT/PTT combination therapy.

Regioisomer-manipulating thio-perylenediimide nanoagents for photothermal/photodynamic theranostics

Thionated perylenediimides (PDIs) can potentially generate thermal and reactive oxygen species and thus can be used as theranostic agents for photothermal/photodynamic therapy. Herein, thionated cis-/trans-isomer PDI-CS and PDI-TS were designed and prepared to investigate thionation engineering on therapeutic performance. The results revealed that the photodynamic performance is less associated with the positon of sulfur atoms. By contrast, trans-isomer PDI-TS showed a photothermal conversion efficiency of up to 58.4%, which was 40% higher than that of PDI-CS (∼41.6%). An in vitro half-maximal inhibitory concentration of ∼7.78 μg mL-1 was achieved for PDI-TS, which was 1.7-fold smaller than that of PDI-CS, strongly reasserting the regioisomer-modulated phototheranostic performance. Notably, the strong π-π and CS interactions in PDI-TS nanoagents are essential factors attributed to their excellent photothermal performance, indicating that the optimization of non-bonding interactions is an ingenious way to improve phototheranostic performance. This work provides a facile means of creating thio-perylenediimides that possess excellent antitumor properties and a novel proof of concept to improve therapeutic performance through the optimization of non-bonding interactions.

Synergistic Effect of Photothermally Targeted NIR-Responsive Nanomedicine-Induced Immunogenic Cell Death for Effective Triple Negative Breast Cancer Therapy

Triple negative breast cancer (TNBC) is a breast cancer subtype. At present, TNBC patients do not have approved targeted therapy. Therefore, patients primarily depend on forceful systemic chemotherapy that has unavoidable harmful side effects, resulting in inadequate therapeutic outcomes and leading to a high mortality rate. Hence, there is an urgent need to develop targeted therapies for the TNBC populace. Developing a new nanotherapeutic approach of combinational therapy could be an effective alternative strategy. Therefore, we designed a combination of hyaluronan (HA)-polyaniline (PANi)-imiquimod (R837), denoted as HA-PANi/R837, nanoparticles (NPs) that exhibited a high extinction coefficient of 8.23 × 10⁸ M^-1 cm^-1 and adequate photothermal conversion efficiency (PCE) (η = 41.6%), making them an efficient photothermal agent (PTA) that is highly beneficial for selective CD44-mediated photothermal ablation of TNBC tumors. Furthermore, co-encapsulation of R837 (toll-like receptor 7 agonist) immunoadjuvant molecules triggers an immune response against the tumor. The formed CD44-targeted HA-PANi/R837 NPs' selectivity incinerates the tumor under near-infrared (NIR)-triggered photothermal ablation, generating tumor-associated antigens and triggering R837 combination with anti-CTLA-4 for immunogenic cell death (ICD) activation to kill the remaining tumor cells in mice and protect against tumor relapse and metastasis. Our results demonstrated that novel HA-PANi/R837 NP-induced photothermal ICD achieved in CD44-targeted TNBC is a promising application.

A photo-triggered antifungal nanoplatform with efflux pump and heat shock protein reversal activity for enhanced chemo-photothermal synergistic therapy

Drug-resistant pathogens are less sensitive to traditional antibiotics in many stubborn infections. It is imminently desirable to have an effective alternative therapeutic agent for combating drug-resistant pathogen infections. Herein, a photo-triggered multifunctional nanoplatform (TMOB/FLU@PCM NPs) with efflux pump and heat shock protein expression reversal activity is developed for the highly effective eradication of drug-resistant fungi. Upon 808 nm laser excitation, the hyperthermia originating from a BODIPY derivative (TMOB) can not only melt the phase-change material (PCM) vehicle consisting of hexadecanol and cis-2-dodecenoic acid (BDSF) to on-demand release the quorum sensing molecule BDSF and the antifungal drug fluconazole (FLU), but can also destroy the integrity of the C. albicans cell membrane. Thanks to the release of BDSF from TMOB/FLU@PCM NPs, the expression of drug efflux pumps (MDR1, CDR2, CDR4) and thermotolerant proteins (HSP12, HSP21, HSP60, HSP90) is inhibited, which further boosts the therapeutic effect of chemo/photothermal therapy. Moreover, the hyphal and biofilm formation of C. albicans can be blocked by TMOB/FLU@PCM NPs under 808 nm laser irradiation. In vitro and in vivo results indicate that TMOB/FLU@PCM NPs with good biosafety can efficiently eliminate clinical azole-resistant C. albicans. Thus, TMOB/FLU@PCM NPs exhibits a promising future in the treatment of azole-resistant C. albicans infection.

Harnessing Hypoxia-Dependent Cyanine Photocages for In Vivo Precision Drug Release

Photocaging holds promise for the precise manipulation of biological events in space and time. However, current near-infrared (NIR) photocages are oxygen-dependent for their photolysis and lack of timely feedback regulation, which has proven to be the major bottleneck for targeted therapy. Herein, we present a hypoxia-dependent photo-activation mechanism of dialkylamine-substituted cyanine (Cy-NH) accompanied by emissive fragments generation, which was validated with retrosynthesis and spectral analysis. For the first time, we have realized the orthogonal manipulation of this hypoxia-dependent photocaging and dual-modal optical signals in living cells and tumor-bearing mice, making a breakthrough in the direct spatiotemporal control and in vivo feedback regulation. This unique photoactivation mechanism overcomes the limitation of hypoxia, which allows site-specific remote control for targeted therapy, and expands the photo-trigger toolbox for on-demand drug release, especially in a physiological context with dual-mode optical imaging under hypoxia.