Pretreatment structural and arterial spin labeling MRI is predictive for p53 mutation in high-grade gliomas

OBJECTIVES

To determine the performance of pretreatment structural and arterial spin labelling (ASL) MRI in predicting p53 mutation in patients with high-grade gliomas (HGGs).

METHODS

Pre-treatment structural and ASL MRI were performed in 57 patients with histologically confirmed HGGs and information of p53 status. Whole-lesion histogram analysis of cerebral blood flow (CBF) images of the enhancing tumour and the peritumoral oedema in the HGGs were performed. Visually AcceSAble Rembrandt Images features were used as qualitative analysis. The differences of ASL histogram parameters and Visually AcceSAble Rembrandt Images features between HGGs with or without p53 mutation were analyzed with post hoc correction for multiple comparisons. LASSO regression was performed to select the optimal features that could predict p53 mutation, followed by receiver operating characteristic analysis to determine the predictive efficacy.

RESULTS

A total of 33 HGGs with p53 mutation and 24 without p53 mutation were included. HGGs with mutant p53 showed lower CBF_percentile5 and CBF_uniformity of the enhancing tumour (p < 0.05) and higher prevalence of the qualitative MRI feature of enhancing tumour crossing midline (ETCM) (p < 0.05) as compared with HGGs with wild-type p53. LASSO regression showed that the CBF_uniformity of the enhancing tumour and ETCM were predictive features for p53 mutation. CBF_uniformity showed an acceptable performance in predicting p53 mutation (area under the curve = 0.721), when combined with the feature of ETCM, its predictive efficacy was significantly improved (area under the curve = 0.814, p = 0.012).

CONCLUSION

An integrated pre-treatment structural and ASL MRI can help to predict p53 mutation in HGGs.

Deep Learning-Based Radiomics of B-Mode Ultrasonography and Shear-Wave Elastography: Improved Performance in Breast Mass Classification

Objective

Shear-wave elastography (SWE) can improve the diagnostic specificity of the B-model ultrasonography (US) in breast cancer. However, whether deep learning-based radiomics signatures based on the B-mode US (B-US-RS) or SWE (SWE-RS) could further improve the diagnostic performance remains to be investigated. We aimed to develop the B-US-RS and SWE-RS and determine their performances in classifying breast masses.

Materials and Methods

This retrospective study included 291 women (mean age ± standard deviation, 40.9 ± 12.3 years) from two centers who had US-visible solid breast masses and underwent biopsy and/or surgical resection between June 2015 and July 2017. B-mode US and SWE images of the 198 masses in 198 patients (training cohort) from center 1 were segmented, respectively, to construct B-US-RS and SWE-RS using the least absolute shrinkage and selection operator regression and tested in an independent validation cohort of 65 masses in 65 patients from center 1 and in an external validation cohort of 28 masses in 28 patients from center 2. The performances of B-US-RS and SWE-RS were assessed using receiver operating characteristic (ROC) analysis and compared with that of radiologist assessment [Breast Imaging Reporting and Data System (BI-RADS)] and quantitative SWE parameters [maximum elasticity (E _max), mean elasticity (E _mean), elasticity ratio (E _ratio), and elastic modulus standard deviation (E _SD)] by using the McNemar test.

Results

The single best-performing quantitative SWE parameter, E _max, had a higher specificity than BI-RADS assessment in the training and independent validation cohorts (P < 0.001 for both). The areas under the ROC curves (AUCs) of B-US-RS and SWE-RS both were 0.99 (95% CI = 0.99-1.00) in the training cohort, 1.00 (95% CI = 1.00-1.00) in the independent validation cohort, and 1.00 (95% CI = 1.00-1.00) in the external validation cohort. The specificities of B-US-RS and SWE-RS were higher than that of E _max in the training (P < 0.001 for both) and independent validation cohorts (P = 0.02 for both).

Conclusion

The B-US-RS and SWE-RS outperformed the quantitative SWE parameters and BI-RADS assessment for classifying breast masses. The integration of the deep learning-based radiomics approach would help improve the classification ability of B-mode US and SWE for breast masses.

One-/Two-Photon Excited Cell Membrane Imaging and Tracking by a Photoactive Nanocage

Cell membrane imaging by predesigned molecular and supramolecular photoluminescence probes is of great importance in understanding the nano-biointeractions for potential applications in cellular tracking, drug delivery, cancer diagnosis, and treatment. Herein, we report an effective strategy for cell membrane imaging in both living cell and tissue levels on the basis of a multifunctional nanocage (MOC-16) integrating one-/two-photon active phosphorescence, high charges, balanced hydrophobicity/lipophilicity, and proton sensitivity attributes. The intrinsic optical characters, including strong one-/two-photon excitation and pH-dependent red emission, make MOC-16 powerful optical probes for membrane imaging in living cell and tissue levels under both visible and near-infrared irradiations. Meanwhile, the highly positive charges of +28 endow MOC-16 with adequate water solubility and deprotonation ability while still maintaining its hydrophobicity, thus enabling balanced hydrophobic-lipophilic interactions at the nano-biointerface to facilitate a pH-dependent membrane absorption within the biological pH range of 5.3-7.4. However, the low-charged RuL₃ metalloligand or polyethylene glycol (PEG)-modified MOC-16^PEG with less hydrophobicity cannot offer enough nano-biointeractions for cell membrane tracking. These findings advance the fundamental understanding of nano-biointerface interactions of MOCs with cell membranes and provide further guidance in their biological applications.

Discriminative pattern of reduced cerebral blood flow in Parkinson's disease and Parkinsonism-Plus syndrome: an ASL-MRI study

Background

Accurate identification of Parkinson’s disease (PD) and Parkinsonism-Plus syndrome (PPS), especially in the early stage of the disease, is very important. The purpose of this study was to investigate the discriminative spatial pattern of cerebral blood flow (CBF) between patients with PD and PPS.

Methods

Arterial spin labeling (ASL) perfusion-weighted imaging was performed in 20 patients with PD (mean age 56.35 ± 7.56 years), 16 patients with PPS (mean age 59.62 ± 6.89 years), and 17 healthy controls (HCs, mean age 54.17 ± 6.58 years). Voxel-wise comparison of the CBF was performed among PD, PPS, and HC groups. The receiver operating characteristic (ROC) curve was used to evaluate the performance of CBF in discriminating between PD and PPS. The relationship between CBF and non-motor neuropsychological scores was assessed by correlation analysis.

Results

PD group showed a significantly decreased CBF in the right cerebelum_crus2, the left middle frontal gyrus (MFG), the triangle inferior frontal gyrus (IFG_Tri), the left frontal medial orbital gyrus (FG_Med_Orb) and the left caudate nucleus (CN) compared with the HC group (P < 0.05). Besides the above regions, the left supplementary motor area (SMA), the right thalamus had decreased CBF in the PPS group compared with the HC group (P < 0.05). PPS group had lower CBF value in the left MFG, the left IFG_Tri, the left CN, the left SMA, and the right thalamus compared with the PD group (P < 0.05). CBFs in left IFG_Tri, the left CN, the left SMA, and the right thalamus had moderate to high capacity in discriminating between PD and PPS patients (AUC 0.719–0.831). The CBF was positively correlated with the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores in PD patients, while positively correlated with the MMSE, Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD) scores in PPS patients (P < 0.05).

Conclusion

PD and PPS patients have certain discriminative patterns of reduced CBFs, which can be used as a surrogate marker for differential diagnosis.

Aberrant Functional and Causal Connectivity in Acute Tinnitus With Sensorineural Hearing Loss

Purpose

The neural bases in acute tinnitus remains largely undetected. The objective of this study was to identify the alteration of the brain network involved in patients with acute tinnitus and hearing loss.

Methods

Acute tinnitus patients (n = 24) with hearing loss and age-, sex-, education-matched healthy controls (n = 21) participated in the current study and underwent resting-state functional magnetic resonance imaging (fMRI) scanning. Regional homogeneity and amplitude of low-frequency fluctuation were used to investigate the local spontaneous neural activity and functional connectivity (FC), and Granger causality analysis (GCA) was used to analyze the undirected and directed connectivity of brain regions.

Results

Compared with healthy subjects, acute tinnitus patients had a general reduction in FC between auditory and non-auditory brain regions. Based on FC analysis, the superior temporal gyrus (STG) revealed reduced undirected connectivity with non-auditory brain regions including the amygdala (AMYG), nucleus accumbens (NAc), the cerebellum, and postcentral gyrus (PoCG). Using the GCA algorithm, increased effective connectivity from the right AMYG to the right STG, and reduced connectivity from the right PoCG to the left NAc was observed in acute tinnitus patients with hearing loss. The pure-tone threshold was positively correlated with FC between the AMYG and STG, and negatively correlated with FC between the left NAc and the right PoCG. In addition, a negative association between the GCA value from the right PoCG to the left NAc and the THI scores was observed.

Conclusion

Acute tinnitus patients have aberrant FC strength and causal connectivity in both the auditory and non-auditory cortex, especially in the STG, AMYG, and NAc. The current findings will provide a new perspective for understanding the neuropathophysiological mechanism in acute tinnitus.

Magnetic resonance imaging of enhanced nerve repair with mesenchymal stem cells combined with microenvironment immunomodulation in neurotmesis

INTRODUCTION

The immuno-microenvironment of injured nerves adversely affects mesenchymal stem cell (MSC) therapy for neurotmesis. Magnetic resonance imaging (MRI) can be used noninvasively to monitor nerve degeneration and regeneration. The aim of this study was to investigate nerve repair after MSC transplantation combined with microenvironment immunomodulation in neurotmesis by using multiparametric MRI.

METHODS

Rats with sciatic nerve transection and surgical coaptation were treated with MSCs combined with immunomodulation or MSCs alone. Serial multiparametric MRI examinations were performed over an 8-week period after surgery.

RESULTS

Nerves treated with MSCs combined with immunomodulation showed better functional recovery, rapid recovery of nerve T2, fractional anisotropy and radial diffusivity values, and more rapid restoration of the fiber tracks than nerves treated with MSCs alone.

DISCUSSION

Transplantation of MSCs in combination with immunomodulation can exert a synergistic repair effect on neurotmesis, which can be monitored by multiparametric MRI.

Radiomics model based on preoperative gadoxetic acid-enhanced MRI for predicting liver failure

BACKGROUND

Postoperative liver failure is the most severe complication in cirrhotic patients with hepatocellular carcinoma (HCC) after major hepatectomy. Current available clinical indexes predicting postoperative residual liver function are not sufficiently accurate.

AIM

To determine a radiomics model based on preoperative gadoxetic acid-enhanced magnetic resonance imaging for predicting liver failure in cirrhotic patients with HCC after major hepatectomy.

METHODS

For this retrospective study, a radiomics-based model was developed based on preoperative hepatobiliary phase gadoxetic acid-enhanced magnetic resonance images in 101 patients with HCC between June 2012 and June 2018. Sixty-one radiomic features were extracted from hepatobiliary phase images and selected by the least absolute shrinkage and selection operator method to construct a radiomics signature. A clinical prediction model, and radiomics-based model incorporating significant clinical indexes and radiomics signature were built using multivariable logistic regression analysis. The integrated radiomics-based model was presented as a radiomics nomogram. The performances of clinical prediction model, radiomics signature, and radiomics-based model for predicting post-operative liver failure were determined using receiver operating characteristics curve, calibration curve, and decision curve analyses.

RESULTS

Five radiomics features from hepatobiliary phase images were selected to construct the radiomics signature. The clinical prediction model, radiomics signature, and radiomics-based model incorporating indocyanine green clearance rate at 15 min and radiomics signature showed favorable performance for predicting postoperative liver failure (area under the curve: 0.809-0.894). The radiomics-based model achieved the highest performance for predicting liver failure (area under the curve: 0.894; 95%CI: 0.823-0.964). The integrated discrimination improvement analysis showed a significant improvement in the accuracy of liver failure prediction when radiomics signature was added to the clinical prediction model (integrated discrimination improvement = 0.117, P = 0.002). The calibration curve and an insignificant Hosmer-Lemeshow test statistic (P = 0.841) demonstrated good calibration of the radiomics-based model. The decision curve analysis showed that patients would benefit more from a radiomics-based prediction model than from a clinical prediction model and radiomics signature alone.

CONCLUSION

A radiomics-based model of preoperative gadoxetic acid–enhanced MRI can be used to predict liver failure in cirrhotic patients with HCC after major hepatectomy.

pH-Sensitive nanotheranostics for dual-modality imaging guided nanoenzyme catalysis therapy and phototherapy

A theranostic nanosystem with a pH-sensitive structure showed charge conversion properties in the tumor acidic microenvironment. It could perform dual-modality imaging diagnosis and carry out catalysis therapy and phototherapy.

Spontaneous pneumomediastinum and subcutaneous emphysema in avian influenza A (H5N6) human pneumonia

The pneumomediastinum and subcutaneous emphysema can repetitively occur in human H5N6 virus pneumonia. Prompt treatment of this uncommon complication is important for successful rescue of patients with H5N6 virus pneumonia.

Multifunctional Nanoregulator Reshapes Immune Microenvironment and Enhances Immune Memory for Tumor Immunotherapy

Hypoxia leads to up-regulation of PD-L1 and decreases T lymphocyte infiltration, thus boosting immunotherapeutic resistance of tumors. Moreover, tumor-infiltrating myeloid cells such as myeloid-derived suppressor cells (MDSCs) correlate with potent immune suppressive activity and resistance to the immune checkpoint blocking (ICB) in tumor sites. Here, a multifunctional nanoregulator incorporating MnO2 particles and small molecular IPI549 is developed, which can reshape the tumor immune microenvironment (TIME) to unleash the immune system. The intravenously administered nanoregulator effectively accumulates in tumor sites to alleviate hypoxia via oxygen-generating reduction of MnO2 and to inhibit PI3Kγ on MDSCs via IPI549 release in the tumor microenvironment (TME), which results in concurrent downregulation of PD-L1 expression, polarization of tumor associated macrophages (TAMs) toward pro-inflammatory M1-like phenotype (tumor-suppressive), enhanced infiltration of CD4+ helper T lymphocytes (Th cells), and cytotoxic CD8+ T lymphocytes (Tc cells), and suppressed infiltration of regulatory T lymphocytes (Treg cells) for effective tumor immunotherapy. Furthermore, the local generation of Mn2+ in TME allows tumor-specific magnetic resonance imaging (MRI). More excitingly, the nanoregulator-reshaped TIME is effectively reserved due to the synergistic effect of hypoxia alleviation and MDSC PI3Kγ inhibition, leading to remarkable post-medication inhibition of tumor re-growth and metastasis in an animal study.

Solid-phase microextraction: An appealing alternative for the determination of endogenous substances - A review

The determination of endogenous substances is of great significance for obtaining important biotic information such as biological components, metabolic pathways and disease biomarkers in different living organisms (e.g. plants, insects, animals and humans). However, due to the complex matrix and the trace concentrations of target analytes, the sample preparation procedure is an essential step before the analytes of interest are introduced into a detection instrument. Solid-phase microextraction (SPME), an emerging sample preparation technique that integrates sampling, extraction, concentration, and sample introduction into one step, has gained wide acceptance in various research fields, including in the determination of endogenous compounds. In this review, recent developments and applications of SPME for the determination of endogenous substances over the past five years are summarized. Several aspects, including the design of SPME devices (sampling configuration and coating), applications (in vitro and in vivo sampling), and coupling with emerging instruments (comprehensive two-dimensional gas chromatography (GC × GC), ambient mass spectrometry (AMS) and surface enhanced Raman scattering (SERS)) are involved. Finally, the challenges and opportunities of SPME methods in endogenous substances analysis are also discussed.

Predictive value of pretreatment MRI texture analysis in patients with primary nasopharyngeal carcinoma

Objectives

To determine the predictive value of pretreatment MRI texture analysis for progression-free survival (PFS) in patients with primary nasopharyngeal carcinoma (NPC).

Methods

Ethical approval by the institutional review board was obtained for this retrospective analysis. In 79 patients with primary NPC, texture analysis of the primary tumour was performed on pretreatment T2 and contrast-enhanced T1-weighted images (T2WIs and CE-T1WIs). The Cox proportional hazards model was used to determine the association of texture features, tumour volume and the tumour-node-metastasis (TNM) stage with PFS. Survival curves were plotted using the Kaplan-Meier method. The prognostic performance was evaluated with the receiver operating characteristic (ROC) analyses and C-index.

Results

Tumour volume (hazard ratio, 1.054; 95% confidence interval [CI], 1.016–1.093) and CE-T1WI-based uniformity (hazard ratio, 0; 95% CI, 0–0.001) were identified as independent predictors for PFS (p < 0.05). Kaplan-Meier analysis showed that smaller tumour volume (less than the cut-off value, 11.699 cm³) and higher CE-T1WI-based uniformity (greater than the cut-off value, 0.856) were associated with improved PFS (p < 0.05). The combination of CE-T1WI-based uniformity with tumour volume and the overall stage predicted PFS better (area under the curve [AUC], 0.825; Cindex, 0.794) than the tumour volume (AUC, 0.659; C-index, 0.616) or the overall stage (AUC, 0.636; C-index, 0.627) did (p < 0.05).

Conclusions

A texture parameter of pretreatment CE-T1WI-based uniformity improves the prediction of PFS in NPC patients.

Key Points

• Higher CE-T1WI-based uniformity and smaller tumour volume are predictive of improved PFS in NPC patients.

• The combination of CE-T1WI-based uniformity with tumour volume and the overall stage has a better predictive ability for PFS than the tumour volume or the overall stage alone.

• Pretreatment MRI texture analysis has a prognostic value for NPC patients.

Electronic supplementary material

The online version of this article (10.1007/s00330-018-5961-6) contains supplementary material, which is available to authorized users.

A robust and homogeneous porous poly(3,4-ethylenedioxythiophene)/graphene thin film for high-efficiency laser desorption/ionization analysis of estrogens in biological samples

Herein, a robust and homogeneous porous poly(3,4-ethylenedioxythiophene)/graphene (PEDOT/graphene) thin film surface-assisted laser desorption/ionization (SALDI) functional platform was prepared through a rapid and facile in-situ photopolymerization method. The graphene-embedded PEDOT skeleton well circumvented the aggregation-related problems in the traditional carbon-based SALDI method which combined with time-of-flight mass spectrometer (TOF MS). As a result, the reproducibility and quantitative capacity of the SALDI platform were significantly improved. Furthermore, the highly efficient adsorption performance of the PEDOT/graphene thin film was demonstrated in terms of in vitro and in vivo solid-phase microextraction (SPME) extraction. It showed that porous morphology with abundant graphene doping favored the adsorption and enrichment of target analytes. Owing to the excellent adsorption capability of the PEDOT/graphene thin film and the inherent strong laser absorption ability of graphene, expected SALDI effect (3-13 times higher than the commercial nanomaterial-assisted LDI plate) and quantitative analysis (linear range 0.5-100 μg L^-1) of the PEDOT/graphene functional surfaces were achieved. As for the real-world applications, we deployed the PEDOT/graphene thin film SALDI platform for the analysis of five estrogens in biological samples at microliter-volume level, without tedious sample preparation procedures. Satisfactory recoveries ranging from 60.6% to 99.0% were obtained. The present study suggested that the graphene-embedded PEDOT skeleton with porous morphology would be developed as promising coating for the adsorption of analytes of interest. Additionally, the combination of PEDOT with graphene not only expanded the application fields of PEDOT, but also offered an efficient strategy for preparing homogeneous functional surfaces to realize the quantitative analysis in SALDI method.

In Vivo Long-Term Tracking of Neural Stem Cells Transplanted into an Acute Ischemic Stroke model with Reporter Gene-Based Bimodal MR and Optical Imaging

Transplantation of neural stem cells (NSCs) is emerging as a new therapeutic approach for stroke. Real-time imaging of transplanted NSCs is essential for successful cell delivery, safety monitoring, tracking cell fate and function, and understanding the interactions of transplanted cells with the host environment. Magnetic resonance imaging (MRI) of magnetic nanoparticle-labeled cells has been the most widely used means to track stem cells in vivo. Nevertheless, it does not allow for the reliable discrimination between live and dead cells. Reporter gene-based MRI was considered as an alternative strategy to overcome this shortcoming. In this work, a class of lentiviral vector-encoding ferritin heavy chain (FTH) and enhanced green fluorescent protein (EGFP) was constructed to deliver reporter genes into NSCs. After these transgenic NSCs were transplanted into the contralateral hemisphere of rats with acute ischemic stroke, MRI and fluorescence imaging (FLI) were performed in vivo for tracking the fate of transplanted cells over a long period of 6 wk. The results demonstrated that the FTH and EGFP can be effectively and safely delivered to NSCs via the designed lentiviral vector. The distribution and migration of grafted stem cells could be monitored by bimodal MRI and FLI. FTH can be used as a robust MRI reporter for reliable reporting of the short-term viability of cell grafts, whereas its capacity for tracking the long-term viability of stem cells remains dependent on several confounding factors such as cell death and the concomitant reactive inflammation.

In vivo tracking of the tropism of mesenchymal stem cells to malignant gliomas using reporter gene-based MR imaging

Mesenchymal stem cells (MSCs) have emerged as a promising cellular vehicle for gene therapy of malignant gliomas due to their property of tumor tropism. However, MSCs may show bidirectional and divergent effects on tumor growth. Therefore, a robust surveillance system with a capacity for noninvasive monitoring of the homing, distribution and fate of stem cells in vivo is highly desired for developing stem cell-based gene therapies for tumors. In this study, we used ferritin gene-based magnetic resonance imaging (MRI) to track the tumor tropism of MSCs in a rat orthotopic xenograft model of malignant glioma. MSCs were transduced with lentiviral vectors expressing ferritin heavy chain (FTH) and enhanced green fluorescent protein (eGFP). Intra-arterial, intravenous and intertumoral injections of these FTH transgenic MSCs (FTH-MSCs) were performed in rats bearing intracranial orthotopic C6 gliomas. The FTH-MSCs were detected as hypointense signals on T2- and T2*-weighted images on a 3.0 T clinical MRI. After intra-arterial injection, 17% of FTH-MSCs migrated toward the tumor and gradually diffused throughout the orthotopic glioma. This dynamic process could be tracked in vivo by MRI up to 10 days of follow-up, as confirmed by histology. Moreover, the tumor tropism of MSCs showed no appreciable impact on the progression of the tumor. These results suggest that FTH reporter gene-based MRI can be used to reliably track the tropism and fate of MSCs after their systemic transplantation in orthotopic gliomas. This real-time in vivo tracking system will facilitate the future development of stem cell-based therapies for malignant gliomas.

The long-term fate of mesenchymal stem cells labeled with magnetic resonance imaging-visible polymersomes in cerebral ischemia

Understanding the long-term fate and potential mechanisms of mesenchymal stem cells (MSCs) after transplantation is essential for improving functional benefits of stem cell-based stroke treatment. Magnetic resonance imaging (MRI) is considered an attractive and clinically translatable tool for longitudinal tracking of stem cells, but certain controversies have arisen in this regard. In this study, we used SPION-loaded cationic polymersomes to label green fluorescent protein (GFP)-expressing MSCs to determine whether MRI can accurately reflect survival, long-term fate, and potential mechanisms of MSCs in ischemic stroke therapy. Our results showed that MSCs could improve the functional outcome and reduce the infarct volume of stroke in the brain. In vivo MRI can verify the biodistribution and migration of grafted cells when pre-labeled with SPION-loaded polymersome. The dynamic change of low signal volume on MRI can reflect the tendency of cell survival and apoptosis, but may overestimate long-term survival owing to the presence of iron-laden macrophages around cell graft. Only a small fraction of grafted cells survived up to 8 weeks after transplantation. A minority of these surviving cells were differentiated into astrocytes, but not into neurons. MSCs might exert their therapeutic effect via secreting paracrine factors rather than directing cell replacement through differentiation into neuronal and/or glial phenotypes.

Folic acid-functionalized polyethylenimine superparamagnetic iron oxide nanoparticles as theranostic agents for magnetic resonance imaging and PD-L1 siRNA delivery for gastric cancer

Programmed death ligand-1 (PD-L1), which is highly expressed in gastric cancers, interacts with programmed death-1 (PD-1) on T cells and is involved in T-cell immune resistance. To increase the therapeutic safety and accuracy of PD-1/PD-L1 blockade, RNA interference through targeted gene delivery was performed in our study. We developed folic acid (FA)- and disulfide (SS)–polyethylene glycol (PEG)-conjugated polyethylenimine (PEI) complexed with superparamagnetic iron oxide Fe₃O₄ nanoparticles (SPIONs) as a siRNA-delivery system for PD-L1 knockdown. The characterization, binding ability, cytotoxicity, transfection efficiency, and cellular internalization of the polyplex were determined. At nitrogen:phosphate (N:P) ratios of 10 or above, the FA-PEG-SS-PEI-SPIONs bound to PD-L1 siRNA to form a polyplex with a diameter of approximately 120 nm. Cell-viability assays showed that the polyplex had minimal cytotoxicity at low N:P ratios. The FA-conjugated polyplex showed higher transfection efficiency and cellular internalization in the folate receptor-overexpressing gastric cancer cell line SGC-7901 than a non-FA-conjugated polyplex. Subsequently, we adopted the targeted FA-PEG-SS-PEI-SPION/siRNA polyplexes at an N:P ratio of 10 for function studies. Cellular magnetic resonance imaging (MRI) showed that the polyplex could also act as a T₂-weighted contrast agent for cancer MRI. Furthermore, one of four PD-L1 siRNAs exhibited effective PD-L1 knockdown in PD-L1-overexpressing SGC-7901. To determine the effects of the functionalized polyplex on T-cell function, we established a coculture model of activated T cells and SGC-7901 cells and demonstrated changes in secreted cytokines. Our findings highlight the potential of this class of multifunctional theranostic nanoparticles for effective targeted PD-L1-knockdown therapy and MRI diagnosis in gastric cancers.

Superparamagnetic Iron Oxide Nanoparticles-Complexed Cationic Amylose for In Vivo Magnetic Resonance Imaging Tracking of Transplanted Stem Cells in Stroke

Cell-based therapy with mesenchymal stem cells (MSCs) is a promising strategy for acute ischemic stroke. In vivo tracking of therapeutic stem cells with magnetic resonance imaging (MRI) is imperative for better understanding cellular survival and migrational dynamics over time. In this study, we develop a novel biocompatible nanocomplex (ASP-SPIONs) based on cationic amylose, by introducing spermine and the image label, ultrasmall superparamagnetic iron oxide nanoparticles (SPIONs), to label MSCs. The capacity, efficiency, and cytotoxicity of the nanocomplex in transferring SPIONs into green fluorescence protein-modified MSCs were tested; and the performance of in vivo MRI tracking of the transplanted cells in acute ischemic stroke was determined. The results demonstrated that the new class of SPIONs-complexed nanoparticles based on biodegradable amylose can serve as a highly effective and safe carrier to transfer magnetic label into stem cells. A reliable tracking of transplanted stem cells in stroke was achieved by MRI up to 6 weeks, with the desirable therapeutic benefit of stem cells on stroke retained. With the advantages of a relatively low SPIONs concentration and a short labeling period, the biocompatible complex of cationic amylose with SPIONs is highly translatable for clinical application. It holds great promise in efficient, rapid, and safe labeling of stem cells for subsequent cellular MRI tracking in regenerative medicine.

A novel polymeric micelle used for in vivo MR imaging tracking of neural stem cells in acute ischemic stroke

Novel cationic polymeric micelles based on biodegradable poly(aspartic acid-dimethylethanediamine)–lysine–cholic acid were synthesized for in vivo tracking therapeutic stem cells using MRI.

In Vivo Targeted MR Imaging of Endogenous Neural Stem Cells in Ischemic Stroke

Acute ischemic stroke remains a leading cause of death and disability. Endogenous neurogenesis enhanced via activation of neural stem cells (NSCs) could be a promising method for stroke treatment. In vivo targeted tracking is highly desirable for monitoring the dynamics of endogenous NSCs in stroke. Previously, we have successfully realized in vivo targeted MR imaging of endogenous NSCs in normal adult mice brains by using anti-CD15 antibody-conjugated superparamagnetic iron oxide nanoparticles (anti-CD15-SPIONs) as the molecular probe. Herein, we explore the performance of this molecular probe in targeted in vivo tracking of activated endogenous NSCs in ischemic stroke. Our study showed that intraventricular injection of anti-CD15-SPIONs could label activated endogenous NSCs in situ seven days after ischemic stroke, which were detected as enlarged areas of hypo-intense signals on MR imaging at 7.0 T. The treatment of cytosine arabinosine could inhibit the activation of endogenous NSCs, which was featured by the disappearance of areas of hypo-intense signals on MR imaging. Using anti-CD15-SPIONs as imaging probes, the dynamic process of activation of endogenous NSCs could be readily monitored by in vivo MR imaging. This targeted imaging strategy would be of great benefit to develop a new therapeutic strategy utilizing endogenous NSCs for ischemic stroke.