A Magneto-Optical Nanoplatform for Multimodality Imaging of Tumors in Mice

Magneto-optical nanosystems for tumor multimodal imaging and therapy in-vivo

Multimodal imaging, which combines the strengths of two or more imaging modalities to provide complementary anatomical and molecular information, has emerged as a robust technology for enhancing diagnostic sensitivity and accuracy, as well as improving treatment monitoring. Moreover, the application of multimodal imaging in guiding precision tumor treatment can prevent under- or over-treatment, thereby maximizing the benefits for tumor patients. In recent years, several intriguing magneto-optical nanosystems with both magnetic and optical properties have been developed, leading to significant breakthroughs in the field of multimodal imaging and image-guided tumor therapy. These advancements pave the way for precise tumor medicine. This review summarizes various types of magneto-optical nanosystems developed recently and describes their applications as probes for multimodal imaging and agents for image-guided therapeutic interventions. Finally, future research and development prospects of magneto-optical nanosystems are discussed along with an outlook on their further applications in the biomedical field.

Magnetic-optical dual-modality imaging monitoring chemotherapy efficacy of pancreatic ductal adenocarcinoma with a low-dose fibronectin-targeting Gd-based contrast agent

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is a lethal hypovascular tumor surrounded by dense fibrosis. Albumin-bound paclitaxel and gemcitabine (AG) chemotherapy is the mainstay of PDAC treatment through depleting peritumoral fibrosis and killing tumor cells; however, it remains challenging due to the lack of a noninvasive imaging method evaluating fibrotic changes during AG chemotherapy. In this study, we developed a dual-modality imaging platform that enables noninvasive, dynamic, and quantitative assessment of chemotherapy-induced fibrotic changes through near-infrared fluorescence molecular imaging (FMI) and magnetic resonance imaging (MRI) using an extradomain B fibronectin (EDB-FN)-targeted imaging probe (ZD2-Gd-DOTA-Cy7).

METHODS

The ZD2-Gd-DOTA-Cy7 probe was constructed by conjugating a peptide (Cys-TVRTSAD) to Gd-DOTA and the near-infrared dye Cy7. PDAC murine xenograft models were intravenously injected with ZD2-Gd-DOTA-Cy7 at a Gd concentration of 0.05 mmol/kg or free Cy7 and Gd-DOTA as control. The normalized tumor background ratio (TBR) on FMI and the T1 reduction ratio on MRI were quantitatively analyzed. For models receiving AG chemotherapy or saline, MRI/FMI was performed before and after treatment. Histological analyses were performed for validation.

RESULTS

The ZD2-Gd-DOTA-Cy7 concentration showed a linear correlation with the fluorescence intensity and T1 relaxation time in vitro. The optimal imaging time was 30 min after injection of the ZD2-Gd-DOTA-Cy7 (0.05 mmol/kg), only half of the clinic dosage of gadolinium. Additionally, ZD2-Gd-DOTA-Cy7 generated a 1.44-fold and 1.90-fold robust contrast enhancement compared with Cy7 (P < 0.05) and Gd-DOTA (P < 0.05), respectively. For AG chemotherapy monitoring, the T1 reduction ratio and normalized TBR in the fibrotic tumor areas were significantly increased by 1.99-fold (P < 0.05) and 1.78-fold (P < 0.05), respectively, in the control group compared with those in the AG group.

CONCLUSION

MRI/FMI with a low dose of ZD2-Gd-DOTA-Cy7 enables sensitive imaging of PDAC and the quantitative assessment of fibrotic changes during AG chemotherapy, which shows potential clinical applications for precise diagnosis, post-treatment monitoring, and disease management.

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

NIR-II Absorption/Emission Dual Function Based 2D Targeted Nanotheranostics for Tunable Hydrogenothermal Therapy

Photothermal therapy (PTT) is a promising approach for treating tumors that offers multiple advantages. Nevertheless, its practical use in clinical settings faces several limitations, such as suboptimal delivery efficiency, uneven heat distribution, and challenges in predicting optimal treatment duration. In addition, the localized hyperthermia generated by the PTT method to induce cell apoptosis can result in the production of excessive reactive oxygen species (ROS) and the release of inflammatory cytokines, which can pose a threat to the healthy tissues surrounding the tumor. To address the above challenges, this work designs an integrated H2 delivery nanoplatform for multimodal imaging H2 thermal therapy. The combination of the second near-infrared window (NIR-II) fluorescence imaging (FL) agent (CQ4T) and the photothermal and photoacoustic (PA) properties of Ti3C2 (TC) enables real-time monitoring of the tumor area and guides photothermal treatment. Simultaneously, due to the acid-responsive H2 release characteristics of the nanoplatform, H2 can be utilized for synergistic photothermal therapy to eradicate tumor cells effectively. Significantly, acting as an antioxidant and anti-inflammatory agent, Ti3C2-BSA-CQ4T-H2 (TCBCH) protects peritumoral normal cells from damage. The proposed technique utilizing H2 gas for combination therapies and multimodal imaging integration exhibits prospects for effective and secure treatment of tumors in future clinical applications.

Active Targeting Hyaluronan Conjugated Nanoprobe for Magnetic Particle Imaging and Near-Infrared Fluorescence Imaging of Breast Cancer and Lung Metastasis

A major contributing cause to breast cancer related death is metastasis. Moreover, breast cancer metastasis often shows little symptoms until a large area of the organs is occupied by metastatic cancer cells. Breast cancer multimodal imaging is attractive since it integrates advantages from several modalities, enabling more accurate cancer detection. Glycoprotein CD44 is overexpressed on most breast cancer cells and is the primary cell surface receptor for hyaluronan (HA). To facilitate breast cancer diagnosis, we report an indocyanine green (ICG) and HA conjugated iron oxide nanoparticle (NP-ICG-HA), which enabled active targeting to breast cancer by HA-CD44 interaction and detected metastasis with magnetic particle imaging (MPI) and near-infrared fluorescence imaging (NIR-FI). When evaluated in a transgenic breast cancer mouse model, NP-ICG-HA enabled the detection of multiple breast tumors in MPI and NIR-FI, providing more comprehensive images and a diagnosis of breast cancer. Furthermore, NP-ICG-HAs were evaluated in a lung metastasis model. Upon NP-ICG-HA administration, MPI showed clear signals in the lungs, indicating the tumor sites. This is the first time that HA-based NPs have enabled MPI of cancer. NP-ICG-HAs are an attractive platform for noninvasive detection of primary breast cancer and lung metastasis.

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.

Recent Developments in Magnetic Hyperthermia Therapy (MHT) and Magnetic Particle Imaging (MPI) in the Brain Tumor Field: A Scoping Review and Meta-Analysis

Magnetic hyperthermia therapy (MHT) is a promising treatment modality for brain tumors using magnetic nanoparticles (MNPs) locally delivered to the tumor and activated with an external alternating magnetic field (AMF) to generate antitumor effects through localized heating. Magnetic particle imaging (MPI) is an emerging technology offering strong signal-to-noise for nanoparticle localization. A scoping review was performed by systematically querying Pubmed, Scopus, and Embase. In total, 251 articles were returned, 12 included. Articles were analyzed for nanoparticle type used, MHT parameters, and MPI applications. Preliminary results show that MHT is an exciting treatment modality with unique advantages over current heat-based therapies for brain cancer. Effective application relies on the further development of unique magnetic nanoparticle constructs and imaging modalities, such as MPI, that can enable real-time MNP imaging for improved therapeutic outcomes.

Magnetic Particle Imaging: From Tracer Design to Biomedical Applications in Vasculature Abnormality

Magnetic particle imaging (MPI) is an emerging non-invasive tomographic technique based on the response of magnetic nanoparticles (MNPs) to oscillating drive fields at the center of a static magnetic gradient. In contrast to magnetic resonance imaging (MRI), which is driven by uniform magnetic fields and projects the anatomic information of the subjects, MPI directly tracks and quantifies MNPs in vivo without background signals. Moreover, it does not require radioactive tracers and has no limitations on imaging depth. This article first introduces the basic principles of MPI and important features of MNPs for imaging sensitivity, spatial resolution, and targeted biodistribution. The latest research aiming to optimize the performance of MPI tracers is reviewed based on their material composition, physical properties, and surface modifications. While the unique advantages of MPI have led to a series of promising biomedical applications, recent development of MPI in investigating vascular abnormalities in cardiovascular and cerebrovascular systems, and cancer are also discussed. Finally, recent progress and challenges in the clinical translation of MPI are discussed to provide possible directions for future research and development.

Enhancing lipid peroxidation via radical chain transfer reaction for MRI guided and effective cancer therapy in mice

Lipid peroxidation (LPO), the process of membrane lipid oxidation, is a potential new form of cell death for cancer treatment. However, the radical chain reaction involved in LPO is comprised of the initiation, propagation (the slowest step), and termination stages, limiting its effectiveness in vivo. To address this limitation, we introduce the radical chain transfer reaction into the LPO process to target the propagation step and overcome the sluggish rate of lipid peroxidation, thereby promoting endogenous lipid peroxidation and enhancing therapeutic outcomes. Firstly, radical chain transfer agent (CTA-1)/Fe nanoparticles (CTA-Fe NPs-1) was synthesized. Notably, CTA-1 convert low activity peroxyl radicals (ROO·) into high activity alkoxyl radicals (RO·), creating the cycle of free radical oxidation and increasing the propagation of lipid peroxidation. Additionally, CTA-1/Fe ions enhance reactive oxygen species (ROS) generation, consume glutathione (GSH), and thereby inactivate GPX-4, promoting the initiation stage and reducing termination of free radical reaction. CTA-Fe NPs-1 induce a higher level of peroxidation of polyunsaturated fatty acids in lipid membranes, leading to highly effective treatment in cancer cells. In addition, CTA-Fe NPs-1 could be enriched in tumors inducing potent tumor inhibition and exhibit activatable T1-MRI contrast of magnetic resonance imaging (MRI). In summary, CTA-Fe NPs-1 can enhance intracellular lipid peroxidation by accelerating initiation, propagation, and inhibiting termination step, promoting the cycle of free radical reaction, resulting in effective anticancer outcomes in tumor-bearing mice.

Renal clearable magnetic nanoparticles for magnetic resonance imaging and guided therapy

Magnetic resonance imaging (MRI) is a non-invasive, radiation-free imaging technique widely used for disease detection and therapeutic evaluation due to its infinite penetration depth. Magnetic nanoparticles (MNPs) have unique magnetic and physicochemical properties, making them ideal as contrast agents for MRI. However, the in vivo toxicity of MNPs, resulting from metal ion leakage and long-term accumulation in the reticuloendothelial system (RES), limits their clinical application. To overcome these challenges, there is considerable interest in the development of renal-clearable MNPs that can be completely cleared through the kidney, reducing retention time and potential toxic risks. In this review, we provide an overview of recent advancements in the development of renal-clearable MNPs for disease imaging and treatment. We discuss the factors influencing renal clearance, summarize the types of renal-clearable MNPs, their synthesis methods, and biomedical applications. This review aims to offer comprehensive information for the design and clinical translation of renal-clearable MNPs. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing.

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.

Cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles for targeted photodynamic and chemodynamic therapy of pancreatic cancer

Oxidative stress induced by reactive oxygen species (ROS) is promising treatment approach for pancreatic ductal adenocarcinoma (PDAC), which is typically insensitive to conventional chemotherapy. In this study, BxPC-3 pancreatic cancer cell membrane-coated upconversion nanoparticles/ZnxMn1-xS core-shell nanoparticles (abbreviated as BUC@ZMS) were developed for tumor-targeted cancer therapy via synergistically oxidative stress and overcoming glutathione (GSH) overexpression. Using a combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT), the BUC@ZMS core-shell nanoparticles were able to elicit the death of pancreatic cancer cells through the high production of ROS. Additionally, the BUC@ZMS core-shell nanoparticles could deplete intracellular GSH and increase the sensitivity of tumor cells to oxidative stress. The in vivo results indicated that BUC@ZMS nanoparticles can accumulate specifically in tumor locations and suppress PDAC without generating obvious toxicity. Thus, it was determined that the as-prepared core-shell nanoparticles would be a viable treatment option for solid malignancies.

Biomedical applications of magnetosomes: State of the art and perspectives

Magnetosomes, synthesized by magnetotactic bacteria (MTB), have been used in nano- and biotechnological applications, owing to their unique properties such as superparamagnetism, uniform size distribution, excellent bioavailability, and easily modifiable functional groups. In this review, we first discuss the mechanisms of magnetosome formation and describe various modification methods. Subsequently, we focus on presenting the biomedical advancements of bacterial magnetosomes in biomedical imaging, drug delivery, anticancer therapy, biosensor. Finally, we discuss future applications and challenges. This review summarizes the application of magnetosomes in the biomedical field, highlighting the latest advancements and exploring the future development of magnetosomes.

In Vivo Fluorescence Molecular Imaging Using Covalent Organic Nanosheets Without Labeling

Organic nanomaterials, as nanocarrier platforms, have tremendous potential for biomedical applications. The authors successfully prepared novel two-dimensional covalent organic nanosheets (CONs) that can be used as efficient in vivo bioimaging probes by condensing 1,3,5-triformylglucinol (Tp) and 2,7-diaminopyrene (Py) to produce TpPy covalent organic frameworks (COFs). TpPy COFs are then subjected to a liquid exfoliation process to obtain TpPy CONs (< 200 nm in size and < 1.7 nm in thickness). TpPy CONs disperse well in water to provide a stable, homogeneous colloidal suspension, which shows favorable photoluminescence properties. Cell viability tests using MDA-MB-231 and RAW 264.7 cells reveal that TpPy CONs are low in cytotoxicity. Confocal microscopy reveals clear fluorescent cell images after incubation with TpPy CONs for 24 h, without reduction in cell activity or cytosolic aggregation. To investigate the biological behavior of the TpPy CONs, the authors perform an in vivo fluorescence imaging study using MDA-MB-231 tumor-bearing mice. After intravenous injection of TpPy CONs disperse in phosphate-buffered saline (PBS), persistent and strong fluorescence signals are observed in the tumor region, with low background signals from normal tissues at 1, 3, 12, and 24 h after injection. Furthermore, these in vivo imaging results concurred with ex vivo biodistribution and histological results.

Near-infrared absorbing semiconducting polymer nanomedicines for cancer therapy

As a new type of organic optical nanomaterials, semiconducting polymer nanoparticles (SPNs) have the advantages of good optical characteristics and photostability, low toxicity concerns, and relatively simple preparation processes. Particularly, near-infrared (NIR) absorbing SPNs have shown a great promise in biomedicine. In addition to acting as nanoprobes for molecular imaging, these SPNs can produce local heat and reactive oxygen species with the stimulation of NIR light, allowing photothermal therapy (PTT) and photodynamic therapy (PDT), respectively. Herein, we summarize the recent development of SPN-based nanomedicines for cancer therapy. The rational designs of SPNs for enhanced PTT, PDT, or combinational PTT/PDT to achieve effective ablation of tumor tissues are highlighted. Via loading/conjugating SPNs with other therapeutic elements (such as chemotherapeutic drugs and immunotherapeutic agents), phototherapy-combined chemotherapy or immunotherapy can be realized, which is then discussed. In especial, the constructions of SPN-based nanomedicines for NIR photoactivatable chemotherapy and immunotherapy are introduced with representative examples. Finally, we discuss the current challenges and key concerns of SPNs for their biomedical applications and give an outlook for their future clinical translation. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Organic Semiconducting Nanoparticles for Biosensor: A Review

Highly bio-compatible organic semiconductors are widely used as biosensors, but their long-term stability can be compromised due to photo-degradation and structural instability. To address this issue, scientists have developed organic semiconductor nanoparticles (OSNs) by incorporating organic semiconductors into a stable framework or self-assembled structure. OSNs have shown excellent performance and can be used as high-resolution biosensors in modern medical and biological research. They have been used for a wide range of applications, such as detecting small biological molecules, nucleic acids, and enzyme levels, as well as vascular imaging, tumor localization, and more. In particular, OSNs can simulate fine particulate matters (PM_2.5, indicating particulate matter with an aerodynamic diameter less than or equal to 2.5 μm) and can be used to study the biodistribution, clearance pathways, and health effects of such particles. However, there are still some problems that need to be solved, such as toxicity, metabolic mechanism, and fluorescence intensity. In this review, based on the structure and design strategies of OSNs, we introduce various types of OSNs-based biosensors with functional groups used as biosensors and discuss their applications in both in vitro and in vivo tracking. Finally, we also discuss the design strategies and potential future trends of OSNs-based biosensors. This review provides a theoretical scaffold for the design of high-performance OSNs-based biosensors and highlights important trends and future directions for their development and application.

Omniparticle Contrast Agent for Multimodal Imaging: Synthesis and Characterization in an Animal Model

PURPOSE

Individual imaging modalities have certain advantages, but each suffers from drawbacks that other modalities may overcome. The goal of this study was to create a novel contrast agent suitable for various imaging modalities that after a single administration can bridge and strengthen the collaboration between the research fields as well as enrich the information obtained from any one modality.

PROCEDURES

The contrast agent platform is based on dextran-coated iron oxide nanoparticles (for MRI and MPI) and synthesized using a modified co-precipitation method, followed by a series of conjugation steps with a fluorophore (for fluorescence and photoacoustic imaging), thyroxine (for CT imaging), and chelators for radioisotope labeling (for PET imaging). The fully conjugated agent was then tested in vitro in cell uptake, viability, and phantom studies and in vivo in a model of intraductal injection and in a tumor model.

RESULTS

The agent was synthesized, characterized, and tested in vitro where it showed the ability to produce a signal on MRI/MPI/FL/PA/CT and PET images. Studies in cells showed the expected concentration-dependent uptake of the agent without noticeable toxicity. In vivo studies demonstrated localization of the agent to the ductal tree in mice after intraductal injection with different degrees of resolution, with CT being the best for this particular application. In a model of injected labeled tumor cells, the agent produced a signal with all modalities and showed persistence in tumor cells confirmed by histology.

CONCLUSIONS

A fully functional omniparticle contrast agent was synthesized and tested in vitro and in vivo in two animal models. Results shown here point to the generation of a potent signal in all modalities tested without detrimental toxicity. Future use of this agent includes its exploration in various models of human disease including image-guided diagnostic and therapeutic applications.

Application of magnetic particle imaging to evaluate nanoparticle fate in rodent joints

Nanoparticles are a promising approach for improving intra-articular drug delivery and tissue targeting. However, techniques to non-invasively track and quantify their concentration in vivo are limited, resulting in an inadequate understanding of their retention, clearance, and biodistribution in the joint. Currently, fluorescence imaging is often used to track nanoparticle fate in animal models; however, this approach has limitations that impede long-term quantitative assessment of nanoparticles over time. The goal of this work was to evaluate an emerging imaging modality, magnetic particle imaging (MPI), for intra-articular tracking of nanoparticles. MPI provides 3D visualization and depth-independent quantification of superparamagnetic iron oxide nanoparticle (SPION) tracers. Here, we developed and characterized a polymer-based magnetic nanoparticle system incorporated with SPION tracers and cartilage targeting properties. MPI was then used to longitudinally assess nanoparticle fate after intra-articular injection. Magnetic nanoparticles were injected into the joints of healthy mice, and evaluated for nanoparticle retention, biodistribution, and clearance over 6 weeks using MPI. In parallel, the fate of fluorescently tagged nanoparticles was tracked using in vivo fluorescence imaging. The study was concluded at day 42, and MPI and fluorescence imaging demonstrated different profiles in nanoparticle retention and clearance from the joint. MPI signal was persistent over the study duration, suggesting NP retention of at least 42 days, much longer than the 14 days observed based on fluorescence signal. These data suggest that the type of tracer - SPIONs or fluorophores - and modality of imaging can affect interpretation of nanoparticle fate in the joint. Given that understanding particle fate over time is paramount for attaining insights about therapeutic profiles in vivo, our data suggest MPI may yield a quantitative and robust method to non-invasively track nanoparticles following intra-articular injection on an extended timeline.

Redox Imbalance Triggered Intratumoral Cascade Reaction for Tumor "turn on" Imaging and Synergistic Therapy

The redox homeostasis in tumors enhances their antioxidant defense ability, limiting reactive oxygen species mediated tumor therapy efficacy. The development of strategies for specific and continuous disruption of the redox homeostasis in tumor cells facilitates the improvement of the cancer therapeutic effect by promoting the apoptosis of tumor cells. Herein, a responsively biodegradable targeting multifunctional integrated nanosphere (HDMn-QDs/PEG-FA) is designed to enhance the anti-tumor efficacy by triggering intratumoral cascade reactions to effectively disrupt intracellular redox homeostasis. Once HDMn-QDs/PEG-FA enters tumor cells, manganese dioxide (MnO₂ ) shell on the surface of nanosphere consumes glutathione (GSH) to produce Mn²⁺ , enabling enhanced chemodynamic therapy (CDT) via a Fenton-like reaction and T₁ -weighted magnetic resonance imaging. Meanwhile, the degradation of MnO₂ can also cause the fluorescence recovery of quantum dots conjugated on the surface of the shell, realizing "turn-on" fluorescence imaging. In addition, the doxorubicin is released because of the cleavage of the embedded SS bond in the hybrid core framework by GSH. A superior synergistic therapeutic efficiency combined CDT and chemotherapy is shown by HDMn-QDs/PEG-FA in vivo. The tumor-inhibition rate reaches to 94.8% and does not cause normal tissue damage due to the good targeting and tumor microenvironment-specific response.

Negatively charged Cu1.33S nanochains: endocytic pathway, photothermal therapy and toxic effect in vivo

Negatively charged nanomaterials have good biocompatibility and low cytotoxicity, but the efficiency of their entry into cells is relatively low. Thus, striking a balance between cell transport efficiency and cytotoxicity is a challenging problem in the field of nanomedicine. In this work, negatively charged Cu_1.33S nanochains have shown a higher cellular uptake level in 4T1 cells than Cu_1.33S nanoparticles with a similar diameter and surface charge. Inhibition experiments indicate that the cellular uptake of the nanochains depends principally on the lipid-raft protein (i.e. caveolin-1) mediated pathway, although the role of clathrin cannot be ruled out. Caveolin-1 can provide short-range attraction at the membrane interface. Furthermore, by using biochemical analysis, blood routine examination and histological evaluation on healthy Sprague Dawley rats, it is found that the Cu_1.33S nanochains have no obvious toxic effect. The Cu_1.33S nanochains have an effective photothermal therapy effect of tumor ablation in vivo under low injection dosage and laser intensity. As for the best performing group (20 μg + 1 W cm^-2), the temperature of the tumor site rapidly increases within the initial 3 min and rises to a plateau of 79 °C (ΔT = 46 °C) at 5 min. These results reveal the feasibility of the Cu_1.33S nanochains as a photothermal agent.

First Superferromagnetic Remanence Characterization and Scan Optimization for Super-Resolution Magnetic Particle Imaging

Magnetic particle imaging (MPI) is a sensitive, high-contrast tracer modality that images superparamagnetic iron oxide nanoparticles, enabling radiation-free theranostic imaging. MPI resolution is currently limited by scanner and particle constraints. Recent tracers have experimentally shown 10× resolution and signal improvements with dramatically sharper M-H curves. Experiments show a dependence on interparticle interactions, conforming to literature definitions of superferromagnetism. We thus call our tracers superferromagnetic iron oxide nanoparticles (SFMIOs). While SFMIOs provide excellent signal and resolution, they exhibit hysteresis with non-negligible remanence and coercivity. We provide the first quantitative measurements of SFMIO remanence decay and reformation using a novel multiecho pulse sequence. We characterize MPI scanning with remanence decay and coercivity and describe an SNR-optimized pulse sequence for SFMIOs under human electromagnetic safety limitations. The resolution from SFMIOs could enable clinical MPI with 10× reduced scanner selection fields, reducing hardware costs by up to 100×.

Non-invasive molecular imaging for precision diagnosis of metastatic lymph nodes: opportunities from preclinical to clinical applications

Lymph node metastasis is an indicator of the invasiveness and aggressiveness of cancer. It is a vital prognostic factor in clinical staging of the disease and therapeutic decision-making. Patients with positive metastatic lymph nodes are likely to develop recurrent disease, distant metastasis, and succumb to death in the coming few years. Lymph node dissection and histological analysis are needed to detect whether regional lymph nodes have been infiltrated by cancer cells and determine the likely outcome of treatment and the patient's chances of survival. However, these procedures are invasive, and tissue biopsies are prone to sampling error. In recent years, advanced molecular imaging with novel imaging probes has provided new technologies that are contributing to comprehensive management of cancer, including non-invasive investigation of lymphatic drainage from tumors, identifying metastatic lymph nodes, and guiding surgeons to operate efficiently in patients with complex lesions. In this review, first, we outline the current status of different molecular imaging modalities applied for lymph node metastasis management. Second, we summarize the multi-functional imaging probes applied with the different imaging modalities as well as applications of cancer lymph node metastasis from preclinical studies to clinical translations. Third, we describe the limitations that must be considered in the field of molecular imaging for improved detection of lymph node metastasis. Finally, we propose future directions for molecular imaging technology that will allow more personalized treatment plans for patients with lymph node metastasis.

Recent progress in nanomedicines for imaging and therapy of brain tumors

Nowadays, a malignant brain tumor is one of the most life-threatening diseases with poor prognosis, high risk of recurrence, and low survival rate for patients because of the existence of the blood-brain barrier (BBB) and the lack of efficient diagnostic and therapeutic paradigms. So far, many researchers have devoted their efforts to innovating advanced drugs to efficiently cross the BBB and selectively target brain tumors for optimal imaging and therapy outcomes. Herein, we update the most recent developments in nanomedicines for the diagnosis and treatment of brain tumors in preclinical mouse models. The special focus is on burgeoning drug delivery carriers to improve the specificity of visualization and to enhance the efficacy of brain tumor treatment. Also, we highlight the challenges and perspectives for the future development of brain tumor theranostics. This review is expected to receive wide attention from researchers, professors, and students in various fields to participate in future advancements in preclinical research and clinical translation of brain tumor nanomedicines.

System matrix recovery based on deep image prior in magnetic particle imaging

Objective.Magnetic particle imaging (MPI) is an emerging tomography imaging technique with high specificity and temporal-spatial resolution. MPI reconstruction based on the system matrix (SM) is an important research content in MPI. However, SM is usually obtained by measuring the response of an MPI scanner at all positions in the field of view. This process is very time-consuming, and the scanner will overheat in a long period of continuous operation, which is easy to generate thermal noise and affects MPI imaging performance.Approach.In this study, we propose a deep image prior-based method that prominently decreases the time of SM calibration. It is an unsupervised method that utilizes the neural network structure itself to recover a high-resolution SM from a downsampled SM without the need to train the network using a large amount of training data.Main results.Experiments on the Open MPI data show that the time of SM calibration can be greatly reduced with only slight degradation of image quality.Significance.This study provides a novel method for obtaining SM in MPI, which shows the potential to achieve SM recovery at a high downsampling rate. It is expected that this study will increase the practicability of MPI in biomedical applications and promote the development of MPI in the future.

Indocyanine Green-Conjugated Superparamagnetic Iron Oxide Nanoworm for Multimodality Breast Cancer Imaging

Breast cancer is the leading cause of cancer-associated deaths among women. Techniques for non-invasive breast cancer detection and imaging are urgently needed. Multimodality breast cancer imaging is attractive since it can integrate advantages from several modalities, enabling more accurate cancer detection. In order to accomplish this, indocyanine green (ICG)-conjugated superparamagnetic iron oxide nanoworm (NW-ICG) has been synthesized as a contrast agent. When evaluated in a spontaneous mouse breast cancer model, NW-ICG gave a large tumor to normal tissue contrasts in multiple imaging modalities including magnetic particle imaging, near-infrared fluorescence imaging, and photoacoustic imaging, providing more comprehensive detection and imaging of breast cancer. Thus, NW-ICGs are an attractive platform for non-invasive breast cancer diagnosis.

Self-assembling ferrimagnetic fluorescent micelles for bioimaging guided efficient magnetic hyperthermia therapy

Multifunctional magnet-fluorescent nanocomposites are widely applied in biomedical applications. Incorporating biocompatible quantum dots with highly ferrimagnetic magnetic nanoparticles into one nanoplatform for achieving efficient magnetic hyperthermia therapy (MHT) is very important. Herein, we reported an amphiphilic block copolymer with a flowable hydrophobic chain to encapsulate highly ferrimagnetic magnetic nanoparticles and ZnS/InP quantum dots via a facile self-assembly method. The obtained ferrimagnetic fluorescent micelle (FMFM) exhibited a uniform diameter of about 180 nm. In stark contrast, larger aggregation (400 nm in diameter) inevitably occurred using common poly(D,L-lactide) (PLA)-based amphiphilic block copolymer with a rigid hydrophobic chain, which was readily cleared by the reticuloendothelial system (RES). The flowable FMFM exhibited long-term colloidal stability within one month and desired fluorescent stability within 84 h. Benefiting from the high ferrimagnetism, the FMFM revealed excellent magnetic heating effect and magnetic resonance imaging capability. With accurate manipulation under an external magnetic field, FMFM realized in vitro enhanced fluorescence imaging sensitivity and accumulation efficiency at the tumor region, achieving in vitro and vivo improved MHT efficacy.

Micro-Nanocarriers Based Drug Delivery Technology for Blood-Brain Barrier Crossing and Brain Tumor Targeting Therapy

The greatest obstacle to using drugs to treat brain tumors is the blood-brain barrier (BBB), making it difficult for conventional drug molecules to enter the brain. Therefore, how to safely and effectively penetrate the BBB to achieve targeted drug delivery to brain tumors has been a challenging research problem. With the intensive research in micro- and nanotechnology in recent years, nano drug-targeted delivery technologies have shown great potential to overcome this challenge, such as inorganic nanocarriers, organic polymer-carriers, liposomes, and biobased carriers, which can be designed in different sizes, shapes, and surface functional groups to enhance their ability to penetrate the BBB and targeted drug delivery for brain tumors. In this review, the composition and overcoming patterns of the BBB are detailed, and then the hot research topics of drug delivery carriers for brain tumors in recent years are summarized, and their mechanisms of action on the BBB and the factors affecting drug delivery are described in detail, and the effectiveness of targeted therapy for brain tumors is evaluated. Finally, the challenges and dilemmas in developing brain tumor drug delivery systems are discussed, which will be promising in the future for targeted drug delivery to brain tumors based on micro-nanocarriers technology.

A guide to the design of magnetic particle imaging tracers for biomedical applications

Magnetic Particle Imaging (MPI) is a novel and emerging non-invasive technique that promises to deliver high quality images, no radiation, high depth penetration and nearly no background from tissues. Signal intensity and spatial resolution in MPI are heavily dependent on the properties of tracers. Hence the selection of these nanoparticles for various applications in MPI must be carefully considered to achieve optimum results. In this review, we will provide an overview of the principle of MPI and the key criteria that are required for tracers in order to generate the best signals. Nanoparticle materials such as magnetite, metal ferrites, maghemite, zero valent iron@iron oxide core@shell, iron carbide and iron-cobalt alloy nanoparticles will be discussed as well as their synthetic pathways. Since surface modifications play an important role in enabling the use of these tracers for biomedical applications, coating options including the transfer from organic to inorganic media will also be discussed. Finally, we will discuss different biomedical applications and provide our insights into the most suitable tracer for each of these applications.

The role of imaging in targeted delivery of nanomedicine for cancer therapy

Nanomedicines overcome the pharmacokinetic limitations of traditional drug formulations and have promising prospect in cancer treatment. However, nanomedicine delivery in vivo is still facing challenges from the complex physiological environment. For the purpose of effective tumor therapy, they should be designed to guarantee the five features principle, including long blood circulation, efficient tumor accumulation, deep matrix penetration, enhanced cell internalization and accurate drug release. To ensure the excellent performance of the designed nanomedicine, it would be better to monitor the drug delivery process as well as the therapeutic effects by real-time imaging. In this review, we summarize strategies in developing nanomedicines for efficiently meeting the five features of drug delivery, and the role of several imaging modalities (fluorescent imaging (FL), magnetic resonance imaging (MRI), computed tomography (CT), photoacoustic imaging (PAI), positron emission tomography (PET), and electron microscopy) in tracing drug delivery and therapeutic effect in vivo based on five features principle.

Recent developments of the reconstruction in magnetic particle imaging

Magnetic particle imaging (MPI) is an emerging molecular imaging technique with high sensitivity and temporal-spatial resolution. Image reconstruction is an important research topic in MPI, which converts an induced voltage signal into the image of superparamagnetic iron oxide particles concentration distribution. MPI reconstruction primarily involves system matrix- and x-space-based methods. In this review, we provide a detailed overview of the research status and future research trends of these two methods. In addition, we review the application of deep learning methods in MPI reconstruction and the current open sources of MPI. Finally, research opinions on MPI reconstruction are presented. We hope this review promotes the use of MPI in clinical applications.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

MnCO3@BSA-ICG nanoparticles as a magnetic resonance/photoacoustic dual-modal contrast agent for functional imaging of acute ischemic stroke

Timely and accurate diagnosis of acute ischemic stroke (AIS) and simultaneous functional imaging of cerebral oxygen saturation (sO₂) are essential to improve the survival rate of stroke patients but remains challenging. Herein, we developed a pH-responsive manganese (Mn)-based nanoplatform as a magnetic resonance/photoacoustic (MR/PA) dual-modal contrast agent for AIS diagnosis. The Mn-based nanoplatform was prepared via a simple and green biomimetic method using bovine serum albumin (BSA) as a scaffold for fabrication of MnCO₃ NPs as the T₁ MR contrast agent and accommodation of indocyanine green (ICG) as the PA probe. The obtained MnCO₃@BSA-ICG NPs were biocompatible and exhibited a pH-responsive longitudinal relaxation rate and a concentration-dependent PA signal. In vivo MR/PA dual-modal imaging demonstrated that MnCO₃@BSA-ICG NPs quickly and efficiently led to the MR/PA contrast enhancements in the infarcted area while not in the normal region, allowing a timely and accurate diagnosis of AIS. Moreover, PA imaging could directly monitor the sO₂ level, enabling a functional imaging of AIS. Therefore, MnCO₃@BSA-ICG NPs could be applied as a potential MR/PA contrast agent for timely and functional imaging of AIS.

Optical magnetic multimodality imaging of plectin-1-targeted imaging agent for the precise detection of orthotopic pancreatic ductal adenocarcinoma in mice

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy worldwide, and the precise detection is challenging currently. Magnetic particle imaging (MPI) is suitable for imaging deep and internal PDAC tumours because of its high sensitivity and unlimited imaging depth. The purpose of this study was to utilize the MPI, in combination with fluorescence molecular imaging (FMI) and magnetic resonance imaging (MRI), to advance the in vivo precise detection of PDAC xenografts.

METHODS

The PDAC targeted plectin-1 peptide and IRDye800CW were conjugated to the superparamagnetic iron oxide nanoparticles (PTP-Fe3O4-IRDye800CW) for the PDAC-targeting triple-modality imaging. Subcutaneous and orthotopic PDAC mouse models were established. FMI, MPI, and MRI were performed for dynamic and quantitative observation of PDAC tumours. Histological staining analyses were used for ex vivo validation.

FINDINGS

PTP-Fe3O4-IRDye800CW nanoparticles possessed great triple-modality imaging performance and specific targeting to plectin-1 expressed on PDAC cells. For in vivo multi-modality imaging of orthotopic PDAC models, the PTP-Fe3O4-IRDye800CW nanoparticles demonstrated higher specificity, even distribution, and longer retention effects in tumours for over 7 d compared with Con-Fe3O4-IRDye800CW nanoparticles. (MPI, 2d post-injection: PTP-Fe3O4-IRDye800CW: 85.72% ± 1.53% vs. Con-Fe3O4-IRDye800CW: 74.41% ± 1.91%, **P < 0.01 (Student's t test)). Ex vivo histological and Prussian blue stainings were performed to validate the distribution of probes.

INTERPRETATION

These data demonstrate the feasibility of utilizing MPI for in vivo PDAC imaging and complement with FMI/MRI for a precise and comprehensive in vivo characterization of PDAC. This may benefit PDAC patients for precise diagnosis and guidance of therapy.

FUNDING

This study was funded by the National Natural Science Foundation of China (Grant No. 62027901, 82071896, 81871422, 81871514, 81227901), Ministry of Science and Technology of China under Grant No. 2017YFA0205200, 2017YFA0700401, Beijing Natural Science Foundation (Grant No. 7212207), Elite Program of Dong Cheng District of Beijing (2020-dchrcpyzz-28), and Peking University Third Hospital (BYSYZD2019018, and jyzc2018-02).

Magnetic particle imaging: tracer development and the biomedical applications of a radiation-free, sensitive, and quantitative imaging modality

Magnetic particle imaging (MPI) is an emerging tracer-based modality that enables real-time three-dimensional imaging of the non-linear magnetisation produced by superparamagnetic iron oxide nanoparticles (SPIONs), in the presence of an external oscillating magnetic field. As a technique, it produces highly sensitive radiation-free tomographic images with absolute quantitation. Coupled with a high contrast, as well as zero signal attenuation at-depth, there are essentially no limitations to where that can be imaged within the body. These characteristics enable various biomedical applications of clinical interest. In the opening sections of this review, the principles of image generation are introduced, along with a detailed comparison of the fundamental properties of this technique with other common imaging modalities. The main feature is a presentation on the up-to-date literature for the development of SPIONs tailored for improved imaging performance, and developments in the current and promising biomedical applications of this emerging technique, with a specific focus on theranostics, cell tracking and perfusion imaging. Finally, we will discuss recent progress in the clinical translation of MPI. As signal detection in MPI is almost entirely dependent on the properties of the SPION employed, this work emphasises the importance of tailoring the synthetic process to produce SPIONs demonstrating specific properties and how this impacts imaging in particular applications and MPI's overall performance.

Recent development of a magneto-optical nanoplatform for multimodality imaging of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer. Given its inconspicuous and atypical early symptoms and hidden location, most patients have already reached the terminal stage before diagnosis. At present, the diagnosis of PDAC mainly depends on serological and imaging examinations. However, serum tests cannot identify specific tumor locations and each imaging technology has its own defects, bringing great challenges to the early diagnosis of PDAC. Therefore, it is of great significance to find new strategies for the early and accurate diagnosis of PDAC. In recent years, a magneto-optical nanoplatform integrating near infrared fluorescence, photoacoustic, magnetic resonance imaging, etc. has attracted widespread attention, giving full play to the complementary advantages of each imaging modality. Herein, we summarize the recent advances of imaging modalities in the diagnosis of pancreatic cancer, and then discuss in detail the construction and modification of magneto or/and optical probes for multimodal imaging, and advances in early diagnosis using the combination of various imaging modalities, which can provide potential tools for the early diagnosis or even intraoperative navigation and post-treatment follow-up of PDAC patients.

Multimodal Contrast Agent Enabling pH Sensing Based on Organically Functionalized Gold Nanoshells with Mn-Zn Ferrite Cores

Highly complex nanoparticles combining multimodal imaging with the sensing of physical properties in biological systems can considerably enhance biomedical research, but reports demonstrating the performance of a single nanosized probe in several imaging modalities and its sensing potential at the same time are rather scarce. Gold nanoshells with magnetic cores and complex organic functionalization may offer an efficient multimodal platform for magnetic resonance imaging (MRI), photoacoustic imaging (PAI), and fluorescence techniques combined with pH sensing by means of surface-enhanced Raman spectroscopy (SERS). In the present study, the synthesis of gold nanoshells with Mn-Zn ferrite cores is described, and their structure, composition, and fundamental properties are analyzed by powder X-ray diffraction, X-ray fluorescence spectroscopy, transmission electron microscopy, magnetic measurements, and UV-Vis spectroscopy. The gold surface is functionalized with four different model molecules, namely thioglycerol, meso-2,3-dimercaptosuccinate, 11-mercaptoundecanoate, and (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide, to analyze the effect of varying charge and surface chemistry on cells in vitro. After characterization by dynamic and electrophoretic light scattering measurements, it is found that the particles do not exhibit significant cytotoxic effects, irrespective of the surface functionalization. Finally, the gold nanoshells are functionalized with a combination of 4-mercaptobenzoic acid and 7-mercapto-4-methylcoumarin, which introduces a SERS active pH sensor and a covalently attached fluorescent tag at the same time. ¹H NMR relaxometry, fluorescence spectroscopy, and PAI demonstrate the multimodal potential of the suggested probe, including extraordinarily high transverse relaxivity, while the SERS study evidences a pH-dependent spectral response.

Chiral nanomaterials for biosensing, bioimaging, and disease therapies

Chiral plasmonic nanomaterials for biosensing, bioimaging and disease therapy.

One-pot synthesis of multifunctional radiolabeled upconversion nanorods for enhanced multimodal imaging performance

We report on the synthesis of radiolabeled NaYF4: Yb/Er/Gd(18/2/60mol%) upconversion nanorods (UCNRs) by one-pot solvothermal process. The synthesized UCNRs were transferred to water by using poly(maleic anhydride-alt-1-octadecene)-mPEG 5000 (C18PMH-PEG). Subsequently...

In situ hydrogen nanogenerator for bimodal imaging guided synergistic photothermal/hydrogen therapies

Multifunctional nanoagents integrating multiple therapeutic and imaging functions hold promise in the field of non-invasive and precise tumor therapies. However, the complex preparation process and uncertain drug metabolism of nanoagents loaded with various therapeutic agents or imaging agents greatly hinder its clinical applications. Developing simple and effective nanoagents that integrate multiple therapeutic and imaging functions remain a huge challenge. Therefore, a novel strategy based on in situ hydrogen release is proposed in this work: aminoborane (AB) was loaded onto mesoporous polydopamine nanoparticles (MPDA NPs) as a prodrug for hydrogen production, and then, PEG was modified on the surface of nanoparticles (represented as AB@MPDA-PEG). MPDA NPs not only act as photothermal agents (PTA) with high photothermal conversion efficiency (808 nm, η = 38.72%) but also as the carriers of AB accumulated in the tumor through enhanced permeability and retention (EPR) effect. H₂ gas generated by AB in the weak acid conditions of the tumor microenvironment (TME) not only was used to treat tumors via a combination of hydrogen and photothermal therapies but also serves as a US and CT contrast agent, providing accurate guidance for tumor treatment. Finally, in vivo and in vitro investigation suggest that the designed multifunctional nanosystem not only showed excellent properties such as high hydrogen-loading capacity, long-lasting sustained hydrogen release ability and excellent biocompatibility but also achieve selective PTT/hydrogen therapies and US/CT bimodal imaging functions, which can effectively guide antitumor therapies. The proposed hydrogen gas-based strategy for combination therapies and bimodal imaging integration holds promise as an efficient and safe tumor treatment for future clinical translation.

Multimodal Contrast Agents for Optoacoustic Brain Imaging in Small Animals

Optoacoustic (photoacoustic) imaging has demonstrated versatile applications in biomedical research, visualizing the disease pathophysiology and monitoring the treatment effect in an animal model, as well as toward applications in the clinical setting. Given the complex disease mechanism, multimodal imaging provides important etiological insights with different molecular, structural, and functional readouts in vivo. Various multimodal optoacoustic molecular imaging approaches have been applied in preclinical brain imaging studies, including optoacoustic/fluorescence imaging, optoacoustic imaging/magnetic resonance imaging (MRI), optoacoustic imaging/MRI/Raman, optoacoustic imaging/positron emission tomography, and optoacoustic/computed tomography. There is a rapid development in molecular imaging contrast agents employing a multimodal imaging strategy for pathological targets involved in brain diseases. Many chemical dyes for optoacoustic imaging have fluorescence properties and have been applied in hybrid optoacoustic/fluorescence imaging. Nanoparticles are widely used as hybrid contrast agents for their capability to incorporate different imaging components, tunable spectrum, and photostability. In this review, we summarize contrast agents including chemical dyes and nanoparticles applied in multimodal optoacoustic brain imaging integrated with other modalities in small animals, and provide outlook for further research.

Bioconjugated nanometals and cancer therapy: a pharmaceutical perspective

Conventional cancer chemotherapies are associated with challenges like delivering sub-therapeutic doses to target cells, lack of bioavailability, drug insolubility and nonspecific toxicity to healthy cells. Nanomedicine, an advanced process, can contribute to the development of personalized medicine for diagnosis, therapy and monitoring of cancer. The nanometals enhance drug dissolution and adhesion to targeted tumor surfaces, resulting in rapid onset of effective therapeutic action. Moreover, nanometals can be conjugated with ligands or polymers through a conjugation process, which further leads to enhanced efficiency, target specificity, improved pharmacokinetics and pharmacodynamics of the drug. This review focuses on the applications of conjugated nanometals in cancer therapy, with a special focus on noble and magnetic nanometals.

Engineering of magnetic nanoparticles as magnetic particle imaging tracers

Magnetic particle imaging (MPI) has recently emerged as a promising non-invasive imaging technique because of its signal linearly propotional to the tracer mass, ability to generate positive contrast, low tissue background, unlimited tissue penetration depth, and lack of ionizing radiation. The sensitivity and resolution of MPI are highly dependent on the properties of magnetic nanoparticles (MNPs), and extensive research efforts have been focused on the design and synthesis of tracers. This review examines parameters that dictate the performance of MNPs, including size, shape, composition, surface property, crystallinity, the surrounding environment, and aggregation state to provide guidance for engineering MPI tracers with better performance. Finally, we discuss applications of MPI imaging and its challenges and perspectives in clinical translation.

Biomimetic nanotherapy: core-shell structured nanocomplexes based on the neutrophil membrane for targeted therapy of lymphoma

Background

Non-Hodgkin’s lymphoma (NHL) is a malignant disease of lymphoid tissue. At present, chemotherapy is still the main method for the treatment of NHL. R-CHOP can significantly improve the survival rate of patients. Unfortunately, DOX is the main cytotoxic drug in R-CHOP and it can lead to adverse reactions. Therefore, it is particularly important to uncover new treatment options for NHL.

Results

In this study, a novel anti-tumor nanoparticle complex Nm@MSNs-DOX/SM was designed and constructed in this study. Mesoporous silica nanoparticles (MSNs) loaded with Doxorubicin (DOX) and anti-inflammatory drugs Shanzhiside methylester (SM) were used as the core of nanoparticles. Neutrophil membrane (Nm) can be coated with multiple nanonuclei as a shell. DOX combined with SM can enhance the anti-tumor effect, and induce apoptosis of lymphoma cells and inhibit the expression of inflammatory factors related to tumorigenesis depending on the regulation of Bcl-2 family-mediated mitochondrial pathways, such as TNF-α and IL-1β. Consequently, the tumor microenvironment (TME) was reshaped, and the anti-tumor effect of DOX was amplified. Besides, Nm has good biocompatibility and can enhance the EPR effect of Nm@MSNs-DOX/SM and increase the effect of active targeting tumors.

Conclusions

This suggests that the Nm-modified drug delivery system Nm@MSNs-DOX/SM is a promising targeted chemotherapy and anti-inflammatory therapy nanocomplex, and may be employed as a specific and efficient anti-Lymphoma therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00922-4.

Recent advances in near-infrared II imaging technology for biological detection

Molecular imaging technology enables us to observe the physiological or pathological processes in living tissue at the molecular level to accurately diagnose diseases at an early stage. Optical imaging can be employed to achieve the dynamic monitoring of tissue and pathological processes and has promising applications in biomedicine. The traditional first near-infrared (NIR-I) window (NIR-I, range from 700 to 900 nm) imaging technique has been available for more than two decades and has been extensively utilized in clinical diagnosis, treatment and scientific research. Compared with NIR-I, the second NIR window optical imaging (NIR-II, range from 1000 to 1700 nm) technology has low autofluorescence, a high signal-to-noise ratio, a high tissue penetration depth and a large Stokes shift. Recently, this technology has attracted significant attention and has also become a heavily researched topic in biomedicine. In this study, the optical characteristics of different fluorescence nanoprobes and the latest reports regarding the application of NIR-II nanoprobes in different biological tissues will be described. Furthermore, the existing problems and future application perspectives of NIR-II optical imaging probes will also be discussed.

Construction of nanomaterials as contrast agents or probes for glioma imaging

Malignant glioma remains incurable largely due to the aggressive and infiltrative nature, as well as the existence of blood-brain-barrier (BBB). Precise diagnosis of glioma, which aims to accurately delineate the tumor boundary for guiding surgical resection and provide reliable feedback of the therapeutic outcomes, is the critical step for successful treatment. Numerous imaging modalities have been developed for the efficient diagnosis of tumors from structural or functional aspects. However, the presence of BBB largely hampers the entrance of contrast agents (Cas) or probes into the brain, rendering the imaging performance highly compromised. The development of nanomaterials provides promising strategies for constructing nano-sized Cas or probes for accurate imaging of glioma owing to the BBB crossing ability and other unique advantages of nanomaterials, such as high loading capacity and stimuli-responsive properties. In this review, the recent progress of nanomaterials applied in single modal imaging modality and multimodal imaging for a comprehensive diagnosis is thoroughly summarized. Finally, the prospects and challenges are offered with the hope for its better development.

Janus Nanoparticles: From Fabrication to (Bio)Applications

Janus nanoparticles (JNPs) refer to the integration of two or more chemically discrepant composites into one structure system. Studies into JNPs have been of significant interest due to their interesting characteristics stemming from their asymmetric structures, which can integrate different functional properties and perform more synergetic functions simultaneously. Herein, we present recent progress of Janus particles, comprehensively detailing fabrication strategies and applications. First, the classification of JNPs is divided into three blocks, consisting of polymeric composites, inorganic composites, and hybrid polymeric/inorganic JNPs composites. Then, the fabrication strategies are alternately summarized, examining self-assembly strategy, phase separation strategy, seed-mediated polymerization, microfluidic preparation strategy, nucleation growth methods, and masking methods. Finally, various intriguing applications of JNPs are presented, including solid surfactants agents, micro/nanomotors, and biomedical applications such as biosensing, controlled drug delivery, bioimaging, cancer therapy, and combined theranostics. Furthermore, challenges and future works in this field are provided.