Magnetic Resonance Imaging of PSMA-Positive Prostate Cancer by a Targeted and Activatable Gd(III) MR Contrast Agent

Self-Assembling Peptide-Based High-Relaxivity Targeted MRI Contrast Agents

Concentration-dependent increases in relaxivity (r1) were found to be induced by self-assembly when Fmoc is adjacent to tryptophan in peptide-based MRI contrast agents featuring Gd-DOTA. A series of di- and tri-peptides were synthesized to test the effect of ionic strength, N-terminal substituent, peptide length, net charge, and relative location of Fmoc and tryptophan on r1 and critical aggregation concentration (CAC) at 1.0 Tesla. Compared to nominal r1 values of 3.5-7.4 mM-1 s-1 per Gd(III), r1 values increased dramatically to 13.2-16.9 mM-1 s-1 per Gd(III) upon self-assembly, with CACs between 0.22 and 2.59 mM when tested in H2O or PBS. When tested in fetal bovine serum (FBS), the compounds maintained high r1 values of 11.2-13.0 mM-1 s-1, but had dramatically lower CAC values below 25 μM. These findings guided the synthesis of two targeted, high-relaxivity MRI contrast agents that contained PSMA-binding ligand, DCL. Their r1 values in H2O or PBS increased from 5.9-7.4 mM-1 s-1 to 13.5-14.8 mM-1 s-1 with CAC values of 1.65-2.70 mM. In FBS, their r1 values were found to be 11.2-11.9 mM-1 s-1, with CAC values below 25 μM. By the conjugation of targeting agents in the last step of synthesis, a broadly applicable route to targeted, high-relaxivity MRI contrast agents is offered.

Rational Design of a Hetero-multinuclear Gadolinium(III)-Copper(II) Complex: Integrating Magnetic Resonance Imaging, Photoacoustic Imaging, Mild Photothermal Therapy, Chemotherapy and Immunotherapy of Cancer

For more accurate diagnosis and effective treatment of cancer, we proposed to develop a hetero-multinuclear metal complex based on the property of apoferritin (AFt) for targeting tumor theranostics by integrating dual-modality imaging diagnosis and multimodality therapy. To this end, we rational designed and synthesized a trinuclear Gd(III)-Cu(II) thiosemicarbazone complex (Gd-2Cu) and then constructed a Gd-2Cu@AFt nanoparticle (NP) delivery system. Gd-2Cu/Gd-2Cu@AFt NPs not only had significant T1-weighted magnetic resonance imaging and photoacoustic imaging of the tumor but also effectively inhibited tumor growth through a combination of mild photothermal therapy, chemotherapy, and immunotherapy. Gd-2Cu@AFt NPs optimized the behavior of imaging diagnosis and therapy of Gd-2Cu, improved its targeting ability, and reduced the side effects in vivo. Besides, we revealed and clarified the anticancer mechanism of Gd-2Cu: interrupting energy metabolism of the tumor cell, inducing apoptosis of the tumor cell, and activating a systemic immune response by inducing immunogenic cell death of cancer cells.

Magnetic Resonance Imaging of Fibroblast Activation Protein Using a Targeted Gadolinium-Based Contrast Agent

The aim of this study was to synthesize a quinoline-based MRI contrast agent, Gd-DOTA-FAPI04, and assess its capacity for targeting fibroblast activation protein (FAP)-positive tumors in vivo. Gd-DOTA-FAPI04 was synthesized by attaching a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) complex of gadolinium(III) to FAP inhibitor FAPI04. The longitudinal relaxation time (T1) of the contrast agent was measured using a Siemens Prisma 3.0T MR system, and the CCK-8 assay was performed to evaluate its potential cytotoxicity. Male nude mice bearing tumors grown from FAP-expressing fibrosarcoma cells were divided into experimental (n = 4) and control (n = 4) groups, and T1-weighted image enhancement was measured at different times (0, 10, 30, 60, 90, and 120 min) postinjection of Gd-DOTA-FAPI04. The control group received an additional preinjection of excess FAPI04. FAP expression in tumor tissue was investigated by using immunohistochemistry with an anti-FAP antibody. The longitudinal relaxivities of gadodiamide and Gd-DOTA-FAPI04 were measured to be 3.734 mM-1 s-1 and 5.323 mM-1 s-1, respectively. The CCK-8 assay demonstrated that Gd-DOTA-FAPI04 has minimal toxicity to cultured human fibrosarcoma cells. In vivo MRI showed that peak accumulation of Gd-DOTA-FAPI04 in FAP-expressing tumors occurred 1 h postinjection and could be blocked by preinjection of excess FAPI04. Immunohistochemical analysis of harvested tumor tissue supported the above findings. Gd-DOTA-FAPI04 is a promising contrast agent for in vivo imaging of FAP.

Stimuli-responsive linkers and their application in molecular imaging

Molecular imaging is a non-invasive imaging method that is widely used for visualization and detection of biological events at cellular or molecular levels. Stimuli-responsive linkers that can be selectively cleaved by specific biomarkers at desired sites to release or activate imaging agents are appealing tools to improve the specificity, sensitivity, and efficacy of molecular imaging. This review summarizes the recent advances of stimuli-responsive linkers and their application in molecular imaging, highlighting the potential of these linkers in the design of activatable molecular imaging probes. It is hoped that this review could inspire more research interests in the development of responsive linkers and associated imaging applications.

Preparation of near-infrared photoacoustic imaging and photothermal treatment agent for cancer using a modifiable acid-triggered molecular platform

Ratiometric near-infrared fluorescent pH probes with various pKa values were innovatively designed and synthesized based on cyanine with a diamine moiety. The photochemical properties of these probes were thoroughly evaluated. Among the series, IR-PHA exhibited an optimal pKa value of approximately 6.40, closely matching the pH of cancerous tissues. This feature is particularly valuable for real-time pH monitoring in both living cells and living mice. Moreover, when administered intravenously to tumor-bearing mice, IR-PHA demonstrated rapid and significant enhancement of near-infrared fluorescence and photoacoustic signals within the tumor region. This outcome underscores the probe's exceptional capability for dual-modal cancer imaging utilizing near-infrared fluorescence (NIRF) and photoacoustic (PA) modalities. Concurrently, the application of a continuous-wave near-infrared laser efficiently ablated cancer cells in vivo, attributed to the photothermal effect induced by IR-PHA. The results strongly indicate that IR-PHA is well-suited for NIRF/PA dual-modality imaging and photothermal therapy of tumors. This makes it a promising candidate for theranostic applications involving small molecules.

Precise prostate cancer diagnosis using fluorescent nanoprobes for detecting PSA and PSMA in serum

Novel Au-Se bond-based nanoprobes were designed for concurrent detection of PSA and PSMA in serum samples, aiming to enhance the early diagnosis of prostate cancer. These probes demonstrate robust stability, specificity and accuracy, underscoring their potential as non-invasive tools for diagnosis.

Glutathione-triggered prodrugs: Design strategies, potential applications, and perspectives

The burgeoning prodrug strategy offers a promising avenue toward improving the efficacy and specificity of cytotoxic drugs. Elevated intracellular levels of glutathione (GSH) have been regarded as a hallmark of tumor cells and characteristic feature of the tumor microenvironment. Considering the pivotal involvement of elevated GSH in the tumorigenic process, a diverse repertoire of GSH-triggered prodrugs has been developed for cancer therapy, facilitating the attenuation of deleterious side effects associated with conventional chemotherapeutic agents and/or the attainment of more efficacious therapeutic outcomes. These prodrug formulations encompass a spectrum of architectures, spanning from small molecules to polymer-based and organic-inorganic nanomaterial constructs. Although the GSH-triggered prodrugs have been gaining increasing interests, a comprehensive review of the advancements made in the field is still lacking. To fill the existing lacuna, this review undertakes a retrospective analysis of noteworthy research endeavors, based on a categorization of these molecules by their diverse recognition units (i.e., disulfides, diselenides, Michael acceptors, and sulfonamides/sulfonates). This review also focuses on explaining the distinct benefits of employing various chemical architecture strategies in the design of these prodrug agents. Furthermore, we highlight the potential for synergistic functionality by incorporating multiple-targeting conjugates, theranostic entities, and combinational treatment modalities, all of which rely on the GSH-triggering. Overall, an extensive overview of the emerging field is presented in this review, highlighting the obstacles and opportunities that lie ahead. Our overarching goal is to furnish methodological guidance for the development of more efficacious GSH-triggered prodrugs in the future. By assessing the pros and cons of current GSH-triggered prodrugs, we expect that this review will be a handful reference for prodrug design, and would provide a guidance for improving the properties of prodrugs and discovering novel trigger scaffolds for constructing GSH-triggered prodrugs.

Kilogram-Scale Synthesis of Extremely Small Gadolinium Oxide Nanoparticles as a T1-Weighted Contrast Agent for Magnetic Resonance Imaging

Magnetic resonance imaging contrast agents are frequently used in clinics to enhance the contrast between diseased and normal tissues. The previously reported poly(acrylic acid) stabilized exceedingly small gadolinium oxide nanoparticles (ES-GdON-PAA) overcame the problems of commercial Gd chelates, but limitations still exist, i.e., high r2/r1 ratio, long blood circulation half-life, and no data for large scale synthesis and formulation optimization. In this study, polymaleic acid (PMA) is found to be an ideal stabilizer to synthesize ES-GdONs. Compared with ES-GdON-PAA, the PMA-stabilized ES-GdON (ES-GdON-PMA) has a lower r2/r1 ratio (2.05, 7.0 T) and a lower blood circulation half-life (37.51 min). The optimized ES-GdON-PMA-9 has an exceedingly small particle size (2.1 nm), excellent water dispersibility, and stability. A facile, efficient, and environmental friendly synthetic method is developed for large-scale synthesis of the ES-GdONs-PMA. The weight of the optimized freeze-dried ES-GdON-PMA-26 synthesized in a 20 L of reactor reaches the kilogram level. The formulation optimization is also finished, and the concentrated ES-GdON-PMA-26 formulation (CGd = 100 mm) after high-pressure steam sterilization possesses eligible physicochemical properties (i.e., pH value, osmolality, viscosity, and density) for investigational new drug application.

A Bis(Aquated) Mn(II)-Based MRI Contrast Agent with a Rigid Hydroquinazoline Unit: Synthesis, Characterization, and in Vivo MR Imaging Study

Since the finding of nephrogenic systemic fibrosis (NFS) in patients with renal impairment and the long-term accumulation of Gd(III) ions in the central nervous system, the search for nongadolinium ion-based MRI contrast agents made of nutrient metal ions has drawn paramount attention. In this context, the development of Mn(II)-based MRI contrast agents has been a subject of interest for the last few decades. Herein, we report a pentadentate ligand (Li2[BenzPic2]) composed of two picolinate moieties and a rigid 1,2,3,4-tetrahydroquinazoline unit and the corresponding bis(aquated) Mn(II) complex (Complex 1). The complex exhibited high thermodynamic stability (log Kcond = 11.62) and kinetic inertness similar to that of the clinically approved Gd(III)-based contrast agent Magnevist. Complex 1 exerted longitudinal relaxivity (r1) of 5.32 mM-1 s-1 at 1.41 T, 37 °C, pH 7.4, and it increased by 3.6-fold in the presence of serum albumin protein, confirming a substantial rigidifying interaction (albumin association constant KA = 1.66 × 103 M-1) between the protein and the amphiphilic (log P = -0.45) contrast agent. An intravenous dose of 0.08 mmol/kg in a healthy mouse, excellent MRI signal intensity enhancement in the vasculature of the mouse liver, and brightened images of the gallbladder, kidney, and liver were realized.

A transferrin receptor targeting dual-modal MR/NIR fluorescent imaging probe for glioblastoma diagnosis

The prognosis of glioblastoma (GBM) remains challenging, primarily due to the lack of a precise, effective imaging technique for comprehensively characterization. Addressing GBM diagnostic challenges, our study introduces an innovative dual-modal imaging that merges near-infrared (NIR) fluorescent imaging with magnetic resonance imaging (MRI). This method employs superparamagnetic iron oxide nanoparticles coated with NIR fluorescent dyes, specifically Cyanine 7, and targeted peptides. This synthetic probe facilitates MRI functionality through superparamagnetic iron oxide nanoparticles, provides NIR imaging capability via Cyanine 7 and enhances tumor targeting trough peptide interactions, offering a comprehensive diagnostic tool for GBM. Notably, the probe traverses the blood-brain barrier, targeting GBM in vivo via peptides, producing clear and discernible images in both modalities. Cytotoxicity and histopathology assessments confirm the probe's favorable safety profile. These findings suggest that the dual-modal MR\NIR fluorescent imaging probe could revolutionize GBM prognosis and survival rates, which can also be extended to other tumors type.

Self-Assembled Nano-CT Contrast Agent Leveraging Size Aggregation for Improved In Vivo Tumor CT Imaging

Computed tomography (CT) is a widely utilized noninvasive diagnostic tool in clinical practice. However, the commonly employed small molecular iodinated contrast agents (ICAs) in clinical CT imaging have limitations such as nonspecific distribution in body, rapid clearance through kidneys, etc., leading to a narrow imaging time window. In contrast, existing nano-sized ICAs face challenges like structural uncertainty, poor reproducibility, low iodine content, and uniformity issues. In this study, a novel approach is presented utilizing the aggregation-induced emission luminogen (AIEgen) to design and fabricate a kind of monocomponent nano-sized ICA (namely, BioDHU-CT NPs) that exhibits a unique aggregation effect upon activation. The small sized BioDHU-CT nanoparticles exhibit excellent tumor targeting capabilities and can release ICA modified with AIEgen with a high release efficiency up to 88.45%, under the activation of reactive oxygen species highly expressed in tumor regions. The released ICA performs in situ aggregation capability in the tumor region, which can enhance the retention efficiency of CT contrast agents, extending the imaging time window and improving the imaging quality in tumor regions.

Redox-Activatable Magnetic Nanoarchitectonics for Self-Enhanced Tumor Imaging and Synergistic Photothermal-Chemodynamic Therapy

Oral squamous cell carcinoma (OSCC) is a prevalent malignancy of the head and neck region associated with high recurrence rates and poor prognosis under current diagnostic and treatment methods. The development of nanomaterials that can improve diagnostic accuracy and therapeutic efficacy is of great importance for OSCC. In this study, a redox-activatable nanoarchitectonics is designed via the construction of dual-valence cobalt oxide (DV-CO) nanospheres, which can serve as a contrast agent for magnetic resonance (MR) imaging, and exhibit enhanced transverse and longitudinal relaxivities through the release and redox of Co3+ /Co2+ in an acidic condition with glutathione (GSH), resulting in self-enhanced T1 /T2 -weighted MR contrast. Moreover, DV-CO demonstrates properties of intracellular GSH-depletion and hydroxyl radicals (•OH) generation through a Fenton-like reaction, enabling strengthened chemodynamic (CD) effect. Additionally, DV-CO displays efficient near-infrared laser-induced photothermal (PT) effect, thereby exhibiting synergistic PT-CD therapy for suppressing OSCC tumor cells. It further investigates the tumor-specific self-enhanced MR imaging of DV-CO both in subcutaneous and orthotopic OSCC mouse models, and demonstrate the therapeutic effects of DV-CO in orthotopic OSCC mouse models. Overall, the in vitro and in vivo findings highlight the excellent theranositc potentials of DV-CO for OSCC and offer new prospects for future advancement of nanomaterials.

AIEgens Cross-linked Iron Oxide Nanoparticles Synchronously Amplify Bimodal Imaging Signals in Situ by Tumor Acidity-Mediated Click Reaction

Activatable dual-modal molecular imaging probes present a promising tool for the diagnosis of malignant tumors. However, synchronously enhancing dual-modal imaging signals under a single stimulus is challenging. Herein, we propose an activatable bimodal probe that integrates aggregation-induced emission luminogens (AIEgens) and iron oxide nanoparticles (IOs) to synergistically enhance near-infrared fluorescence (NIRF) intensity and magnetic resonance (MR) contrast through a tumor acidity-mediated click reaction. Tumor acidity-responsive IOs containing dibenzocyclooctyne groups (termed cDIOs) and AIEgens containing azide groups (termed AATs) can be covalently cross-linked in response to tumor acidity, which leads to a simultaneous enhancement in NIRF intensity (≈12.4-fold) and r2 relaxivity (≈2.8-fold). cDIOs and AATs were effectively activated in mice orthotropic breast tumor, and the cross-linking prolonged their retention in tumor, further augmenting the bimodal signals and expanding imaging time frame. This facile strategy leverages the inherent properties of probes themselves and demonstrates promise in future translational studies.

A cell-impermeable luminogenic probe for near-infrared imaging of prostate-specific membrane antigen in prostate cancer microenvironments

Prostate-specific membrane antigen (PSMA) imaging probes are a promising tool for the diagnosis and image-guided surgery of prostate cancer (PCa). However, PSMA-specific luminescence probes for PCa detection and heterogeneity studies with high imaging contrast are lacking. Here, we report the first near-infrared (NIR) iridium(III) complex for the wash-free and specific imaging of PSMA in PCa cells and spheroids. The conjugation of a PSMA inhibitor, Lys-urea-Glu, to an iridium(III) complex synergizes the PSMA-specific affinity and biocompatibility of the inhibitor with the desirable photophysical properties of the iridium(III) complex, including NIR emission (670 nm), high photostability and a large Stokes shift. The cellular impermeability of the probe along with its strong binding affinity to PSMA enhances its specificity for PSMA, enabling the washing-free luminescent imaging of membrane PSMA with lower cytotoxicity. The probe was successfully applied for selectively visualizing PSMA-expressing cells and for the imaging of PSMA in a multicellular PCa model with good imaging penetration, indicating its potential use in complicated and heterogeneous tumor microenvironments. Furthermore, the probe showed good imaging performance in the PCa-bearing tumor mice via targeting PSMA in vivo. This work provides a novel strategy for the development of highly sensitive and specific NIR probes for PSMA in biological systems in vitro, which is of great significance for the precise diagnosis of PCa and for elucidating PCa heterogeneity.

Surface chemistry mediates the tumor entrance of nanoparticles probed using single-molecule dual-imaging nanodots

The active transport of nanoparticles into solid tumors through transcytosis has been recognized as a promising way to enhance tumor accumulation and penetration, but the effect of the physicochemical properties of nanoparticles remains unclear. Herein, we develop a type of single-molecule dual imaging nanodot by divergent growth of perylenediimide (PDI)-dye-cored polylysine dendrimers and internal orthogonal conjugation of Gd(III)-based macrocyclic probes for fluorescence imaging and magnetic resonance imaging (MRI) of surface chemistry-dependent tumor entrance. The MRI and fluorescence imaging show that sixth-generation nanodots with acetylated (G6-Ac) and oligo ethylene glycol (G6-OEG) surfaces exhibit similar high tumor accumulation but different intratumor distribution. Cellular uptake and transport experiments suggest that G6-Ac nanodots have lower lysosomal entrapment (61% vs. 83%) and a higher exocytotic rate (47% vs. 29%) than G6-OEG. Therefore, G6-Ac is more likely to undergo intercellular transport through cell transcytosis, and is able to reach a tumor area distant from blood vessels, while G6-OEG mainly enters the tumor through enhanced permeability and retention (EPR) effect-based passive transport, and is not able to deliver to distant tumor areas. This study suggests that it is possible to boost the tumor entrance of nanoparticles by engineering surface chemistry for active transport.

Evaluation of a photodynamic therapy agent using a canine prostate cancer model

BACKGROUND

Male dogs can develop spontaneous prostate cancer, which is similar physiologically to human disease. Recently, Tweedle and coworkers have developed an orthotopic canine prostate model allowing implanted tumors and therapeutic agents to be tested in a more translational large animal model. We used the canine model to evaluate prostate-specific membrane antigen (PSMA)-targeted gold nanoparticles as a theranostic approach for fluorescence (FL) imaging and photodynamic therapy (PDT) of early stage prostate cancer.

METHODS

Dogs (four in total) were immunosuppressed with a cyclosporine-based immunosuppressant regimen and their prostate glands were injected with Ace-1-hPSMA cells using transabdominal ultrasound (US) guidance. Intraprostatic tumors grew in 4-5 weeks and were monitored by ultrasound (US). When tumors reached an appropriate size, dogs were injected intravenously (iv) with PSMA-targeted nano agents (AuNPs-Pc158) and underwent surgery 24 h later to expose the prostate tumors for FL imaging and PDT. Ex vivo FL imaging and histopathological studies were performed to confirm PDT efficacy.

RESULTS

All dogs had tumor growth in the prostate gland as revealed by US. Twenty-four hours after injection of PSMA-targeted nano agents (AuNPs-Pc158), the tumors were imaged using a Curadel FL imaging device. While normal prostate tissue had minimal fluorescent signal, the prostate tumors had significantly increased FL. PDT was activated by irradiating specific fluorescent tumor areas with laser light (672 nm). PDT bleached the FL signal, while fluorescent signals from the other unexposed tumor tissues were unaffected. Histological analysis of tumors and adjacent prostate revealed that PDT damaged the irradiated areas to a depth of 1-2 mms with the presence of necrosis, hemorrhage, secondary inflammation, and occasional focal thrombosis. The nonirradiated areas showed no visible damages by PDT.

CONCLUSION

We have successfully established a PSMA-expressing canine orthotopic prostate tumor model and used the model to evaluate the PSMA-targeted nano agents (AuNPs-Pc158) in the application of FL imaging and PDT. It was demonstrated that the nano agents allowed visualization of the cancer cells and enabled their destruction when they were irradiated with a specific wavelength of light.

A trade-off between ligand coating and crystallinity of Gd-doped ultrasmall CeO2 for improving relaxivity

A Gd-doped ultrasmall CeO₂ contrast agent was prepared with high longitudinal relaxivity (r₁ = 10.1 mM^-1 s^-1, 7.0 T) through rationally regulating the crystallinity and surface coatings, providing a new paradigm for optimizing MRI performance. Moreover, responsive photoacoustic imaging (PAI) was established via tumor microenvironment-triggered oxidation, affording dual-modal imaging.

Biomimetic Theranostic Agents with Superior NIR-II Photoacoustic and Magnetic Resonance Imaging Performance for Targeted Photothermal Therapy of Prostate Cancer

The accurate diagnosis and treatment of prostate cancer at an early stage is crucial to reduce mortality rates. However, the limited availability of theranostic agents with active tumor-targeting abilities hinders imaging sensitivity and therapeutic efficiency. To address this challenge, we have developed biomimetic cell membrane-modified Fe₂O₃ nanoclusters implanted in polypyrrole (CM-LFPP), achieving photoacoustic/magnetic resonance dual-modal imaging-guided photothermal therapy of prostate cancer. The CM-LFPP exhibits strong absorption in the second near-infrared window (NIR-II, 1000-1700 nm), showing high photothermal conversion efficiency of up to 78.7% under 1064 nm laser irradiation, excellent photoacoustic imaging capabilities, and good magnetic resonance imaging ability with a T2 relaxivity of up to 48.7 s^-1 mM^-1. Furthermore, the lipid encapsulation and biomimetic cell membrane modification enable CM-LFPP to actively target tumors, leading to a high signal-to-background ratio of ~30.2 for NIR-II photoacoustic imaging. Moreover, the biocompatible CM-LFPP enables low-dose (0.6 W cm^-2) photothermal therapy of tumors under 1064 nm laser irradiation. This technology offers a promising theranostic agent with remarkable photothermal conversion efficiency in the NIR-II window, providing highly sensitive photoacoustic/magnetic resonance imaging-guided prostate cancer therapy.

Single-Atom Gadolinium Nano-Contrast Agents with High Stability for Tumor T1 Magnetic Resonance Imaging

Gadolinium chelates for tumor magnetic resonance imaging (MRI) face challenges such as inadequate sensitivity, lack of selectivity, and risk of Gd leakage. This study presents a single-atom Gd nano-contrast agent (Gd-SA) that enhances tumor MRI. Isolated Gd atoms coordinated by six N atoms and two O atoms are atomically dispersed on a hollow carbon nanosphere, allowing the maximum utilization of Gd atoms with reduced risk of toxic Gd ion leakage. Owning to the large surface area and fast exchange of relaxed water molecules, Gd-SA shows excellent T₁-weighted magnetic resonance enhancement with a r₁ value of 11.05 mM^-1 s^-1 at 7 T, which is 3.6 times that of the commercial gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In vivo MRI results show that the Gd-SA has a higher spatial resolution and a wider imaging time window for tumors than Gd-DTPA, with low hematological, hepatic, and nephric toxicities. These advantages demonstrate the great potential of single-atom Gd-based nanomaterials as safe, efficient, and long-term MRI contrast agents for cancer diagnosis.

Rational Design of Polymethine Dyes with NIR-II Emission and High Photothermal Conversion Efficiency for Multimodal-Imaging-Guided Photo-Immunotherapy

Phototheranostics have emerged and flourished as a promising pattern for cancer theranostics owing to their precise photoinduced diagnosis and therapeutic to meet the demands of precision medicine. The diagnosis information and therapeutic effect are directly determined by the fluorescence imaging ability and photothermal conversion efficiency (PCE) of phototheranostic agents. Hence, how to balance the competitive radiative and nonradiative processes of phototheranostic agents is the key factor to evaluate the phototheranostic effect. Herein, molecules named ICRs with high photostaibility  are rationally designed, exhibiting fluorescence emission in the second near-infrared window (NIR-II, 1000-1700 nm) and high PCE, which are related to the strong donor-acceptor (D-A) interaction and high reorganization energy Noteworthily, ICR-Qu with stronger D-A interaction and a large-sized conjugated unit encapsulated in nanoparticles exhibits high PCE (81.1%). In addition, ICR-QuNPs are used for fluorescence imaging (FLI), photoacoustic imaging (PAI), and photothermal imaging (PTI) to guide deep-tissue photonic hyperthermia, achieving precise removal and inhibition of breast cancer. Furthermore, combined with α-PD-1, ICR-QuNPs show huge potential to be a facile and efficient tool for photo-immunotherapy. More importantly, this study not only reports an "all-in-one" polymethine-based phototheranostic agent, but also sheds light on the exploration of versatile organic molecules for future practical applications.

Regulating the Membrane Affinity of Multi-module Probes to Address the Trade-off between Anchoring and Internalization

Cell membrane transport is the first and crucial step for bioprobes to realize the diagnosis, imaging, and therapy in cells. However, during this transport, there is a trade-off between anchoring and internalization steps, which will seriously affect the membrane transport efficiency. In the past, because the interaction between probes and cell membrane is constant, this challenge is hard to solve. Here, we proposed a strategy to regulate the membrane affinity of multi-module probes that enabled probe to have strong affinity during cell membrane anchoring and weak affinity during internalization. Specifically, a multi-module probe defined as LK-M-NA was constructed, which consisted of three main parts, membrane-anchoring α-helix peptide (LK), anchoring regulator (M), and therapeutic module (NA). With the α-helix module, LK-M-NA was able to rapidly anchor on the cell membrane and the binding energy was -1450.90 kcal/mol. However, after pericellular cleavage by the highly active matrix metalloproteinase-2 , LK could be removed due to the breakage of M and the binding energy reduced to -869.95 kcal/mol. Thus, the internalization restriction caused by high affinity was relieved. Owing to the alterable affinity, the membrane transport efficiency of LK-M-NA increased to 14.58%, well addressing the trade-off problem.

A Supramolecular Self-Assembling Nanoagent by Inducing Intracellular Aggregation of PSMA for Prostate Cancer Molecularly Targeted Theranostics

Prostate cancer (PCa) with prostate-specific membrane antigen (PSMA)-specific high expression is well suited for molecularly targeted theranostics. PSMA expression correlates with the malignancy of PCa, and its dimeric form can promote tumor progression by exerting enzymatic activity to activate downstream signal transduction. However, almost no studies have shown that arresting the procancer signaling of the PSMA receptors themselves can cause tumor cell death. Meanwhile, supramolecular self-assembling peptides are widely used to design anticancer agents due to their unique and excellent properties. Here, a PSMA-targeting supramolecular self-assembling nanotheranostic agent, DBT-2FFGACUPA, which actively targets PSMA receptors on PCa cell membranes and induces them to enter the cell and form large aggregates, is developed. This process not only selectively images PSMA-positive tumor cells but also suppresses the downstream procancer signals of PSMA, causing tumor cell death. This work provides an alternative approach and an advanced agent for molecularly targeted theranostics options in PCa that can induce tumor cell death without relying on any reported anticancer drugs.

Emerging nanobiotechnology-encoded relaxation tuning establishes new MRI modes to localize, monitor and predict diseases

Magnetic resonance imaging (MRI) is one of the most important techniques in the diagnosis of many diseases including cancers, where contrast agents (CAs) are usually necessary to improve its precision and sensitivity. Previous MRI CAs are confined to the signal-to-noise ratio (SNR) elevation of lesions for precisely localizing lesions. As nanobiotechnology advances, some new MRI CAs or nanobiotechnology-enabled MRI modes have been established to vary the longitudinal or transverse relaxation of CAs, which are harnessed to detect lesion targets, monitor disease evolution, predict or evaluate curative effect, etc. These distinct cases provide unexpected insights into the correlation of the design principles of these nanobiotechnologies and corresponding MRI CAs with their potential applications. In this review, first, we briefly present the principles, classifications and applications of conventional MRI CAs, and then elucidate the recent advances in relaxation tuning via the development of various nanobiotechnologies with emphasis on the design strategies of nanobiotechnology and the corresponding MRI CAs to target the tumor microenvironment (TME) and biological targets or activities in tumors or other diseases. In addition, we exemplified the advantages of these strategies in disease theranostics and explored their potential application fields. Finally, we analyzed the present limitations, potential solutions and future development direction of MRI after its combination with nanobiotechnology.

Simultaneous enhancement of T1 and T2 magnetic resonance imaging of liver tumor at respective low and high magnetic fields

Background: Nowadays, magnetic resonance imaging (MRI) is routinely applied in clinical diagnosis. However, using one contrast agent (CA) to simultaneously enhance the T1 and T2 MR contrast at low and high magnetic fields respectively has not been reported. Methods: Herein, we investigated the MR property of a γ-glutamyl transpeptidase (GGT)-instructed, intracellular formed gadolinium nanoparticle (DOTA-Gd-CBT-NP) at low and high magnetic fields. Results: Experimental results showed that DOTA-Gd-CBT-NP possesses a low r2/r1 ratio 0.91 which enables it to enhance T1 MR imaging of liver tumor at 1.0 T, and a high r2/r1 ratio 11.8 which renders the nanoparticle to largely enhance T2 MR imaging of liver tumor at 9.4 T. Conclusion: We expect that our GGT-responsive Gd-nanoparticle could be applied for simultaneous T1 and T2 MRI diagnosis of early liver cancer in clinic at respective low and high magnetic fields when the 9.4 T MR machine is clinically available in the future.