Pooling sputum samples for the Xpert MTB/RIF assay: a practical screening strategy for highly infectious tuberculosis cases.

The Xpert MTB/RIF test (Xpert) can help in the accurate screening of tuberculosis, however, its widespread use is limited by its high cost and lack of accessibility. Pooling of sputum samples for testing is a strategy to cut expenses and enhance population coverage but may result in a decrease in detection sensitivity due to the dilution of Mycobacterium tuberculosis (Mtb) by sample mixing. We investigated how the mixing ratio affected the detection performance of Xpert. We used frozen sputum samples that had been kept after individual Xpert assays of the sputa from Mtb-confirmed TB patients and non-TB patients. Our results showed that the overall sensitivity of the Xpert pooling assay remained higher than 80% when the mixing ratio was between 1/2 and 1/8. When the mixing ratio was raised to 1/16, the positive detection rate fell to 69.0%. For patients with either a high sputum Mtb smear score ≥ 2+, a time-to-positive culture ≤ 10 days, or an Xpert test indicating a high or medium abundance of bacteria, the pooling assay positivity rates were 93.3%, 96.8%, and 100% respectively, even at a 1/16 mixing ratio. For participants with cavities and cough, the pooling assay positivity rates were 86.2% and 90.0% at a 1/8 ratio, higher than for those without these signs. Our results show that the Xpert pooled assay has a high overall sensitivity, especially for highly infectious patients. This pooling strategy with lower reagent and labor costs could support TB screening in communities with limited resources, thereby facilitating reductions in the community transmission and incidence of TB worldwide.

Surface ligand-regulated renal clearance of MRI/SPECT dual-modality nanoprobes for tumor imaging.

BACKGROUND: The general sluggish clearance kinetics of functional inorganic nanoparticles tend to raise potential biosafety concerns for in vivo applications. Renal clearance is a possible elimination pathway for functional inorganic nanoparticles delivered through intravenous injection, but largely depending on the surface physical chemical properties of a given particle apart from its size and shape. RESULTS: In this study, three small-molecule ligands that bear a diphosphonate (DP) group, but different terminal groups on the other side, i.e., anionic, cationic, and zwitterionic groups, were synthesized and used to modify ultrasmall Fe3O4 nanoparticles for evaluating the surface structure-dependent renal clearance behaviors. Systematic studies suggested that the variation of the surface ligands did not significantly increase the hydrodynamic diameter of ultrasmall Fe3O4 nanoparticles, nor influence their magnetic resonance imaging (MRI) contrast enhancement effects. Among the three particle samples, Fe3O4 nanoparticle coated with zwitterionic ligands, i.e., Fe3O4@DMSA, exhibited optimal renal clearance efficiency and reduced reticuloendothelial uptake. Therefore, this sample was further labeled with 99mTc through the DP moieties to achieve a renal-clearable MRI/single-photon emission computed tomography (SPECT) dual-modality imaging nanoprobe. The resulting nanoprobe showed satisfactory imaging capacities in a 4T1 xenograft tumor mouse model. Furthermore, the biocompatibility of Fe3O4@DMSA was evaluated both in vitro and in vivo through safety assessment experiments. CONCLUSIONS: We believe that the current investigations offer a simple and effective strategy for constructing renal-clearable nanoparticles for precise disease diagnosis.

Intranasal Pathway for Nanoparticles to Enter the Central Nervous System.

Intranasal administration was previously proposed for delivering drugs for central nervous system (CNS) diseases. However, the delivery and elimination pathways, which are very imperative to know for exploring the therapeutic applications of any given CNS drugs, remain far from clear. Because lipophilicity has a high priority in the design of CNS drugs, the as-prepared CNS drugs tend to form aggregates. Therefore, a PEGylated Fe3O4 nanoparticle labeled with a fluorescent dye was prepared as a model drug and studied to elucidate the delivery pathways of intranasally administered nanodrugs. Through magnetic resonance imaging, the distribution of the nanoparticles was investigated in vivo. Through ex vivo fluorescence imaging and microscopy studies, more precise distribution of the nanoparticles across the entire brain was disclosed. Moreover, the elimination of the nanoparticles from cerebrospinal fluid was carefully studied. The temporal dose levels of intranasally delivered nanodrugs in different parts of the brain were also investigated.

A Novel Online Calculator Predicting Acute Kidney Injury After Liver Transplantation: A Retrospective Study.

Acute kidney injury (AKI) after liver transplantation (LT) is a common complication, and its development is thought to be multifactorial. We aimed to investigate potential risk factors and build a model to identify high-risk patients. A total of 199 LT patients were enrolled and each patient data was collected from the electronic medical records. Our primary outcome was postoperative AKI as diagnosed and classified by the KDIGO criteria. A least absolute shrinkage and selection operating algorithm and multivariate logistic regression were utilized to select factors and construct the model. Discrimination and calibration were used to estimate the model performance. Decision curve analysis (DCA) was applied to assess the clinical application value. Five variables were identified as independent predictors for post-LT AKI, including whole blood serum lymphocyte count, RBC count, serum sodium, insulin dosage and anhepatic phase urine volume. The nomogram model showed excellent discrimination with an AUC of 0.817 (95% CI: 0.758-0.876) in the training set. The DCA showed that at a threshold probability between 1% and 70%, using this model clinically may add more benefit. In conclusion, we developed an easy-to-use tool to calculate the risk of post-LT AKI. This model may help clinicians identify high-risk patients.

Risk factors of major bleeding detected by machine learning method in patients undergoing liver resection with controlled low central venous pressure technique.

BACKGROUND: Controlled low central venous pressure (CLCVP) technique has been extensively validated in clinical practices to decrease intraoperative bleeding during liver resection process; however, no studies to date have attempted to propose a scoring method to better understand what risk factors might still be responsible for bleeding when CLCVP technique was implemented. METHODS: We aimed to use machine learning to develop a model for detecting the risk factors of major bleeding in patients who underwent liver resection using CLCVP technique. We reviewed the medical records of 1077 patients who underwent liver surgery between January 2017 and June 2020. We evaluated the XGBoost model and logistic regression model using stratified K-fold cross-validation (K = 5), and the area under the receiver operating characteristic curve, the recall rate, precision rate, and accuracy score were calculated and compared. The SHapley Additive exPlanations was employed to identify the most influencing factors and their contribution to the prediction. RESULTS: The XGBoost classifier with an accuracy of 0.80 and precision of 0.89 outperformed the logistic regression model with an accuracy of 0.76 and precision of 0.79. According to the SHapley Additive exPlanations summary plot, the top six variables ranked from most to least important included intraoperative hematocrit, surgery duration, intraoperative lactate, preoperative hemoglobin, preoperative aspartate transaminase, and Pringle maneuver duration. CONCLUSIONS: Anesthesiologists should be aware of the potential impact of increased Pringle maneuver duration and lactate levels on intraoperative major bleeding in patients undergoing liver resection with CLCVP technique.   What is already known on this topic-Low central venous pressure technique has already been extensively validated in clinical practices, with no prediction model for major bleeding. What this study adds-The XGBoost classifier outperformed logistic regression model for the prediction of major bleeding during liver resection with low central venous pressure technique. How this study might affect research, practice, or policy-anesthesiologists should be aware of the potential impact of increased PM duration and lactate levels on intraoperative major bleeding in patients undergoing liver resection with CLCVP technique.

Adjunctive interleukin-2 for the treatment of drug-susceptible tuberculosis: a randomized control trial in China.

PURPOSE: Evaluation of the efficacy and safety of IL-2 in the treatment of drug-susceptible tuberculosis. METHODS: First, the cases of diagnosed drug-susceptible tuberculosis were randomized into two groups-the control group that received the background regimen of isoniazid, rifampin, pyrazinamide, and ethambutol, and the experimental group that received the background regimen plus IL-2. The efficacy and safety evaluations were performed throughout the therapy process as well as 12 months after the treatment completion. RESULTS: A total of 1151 patients underwent the randomization, among which 539 (96.2%) of the 560 in the experimental group achieved the sputum culture conversion to negative, compared to the 551 (93.2%) of the 591 in the control group, after 2 months of treatment, with significant difference observed between the groups (P = 0.025). Cavity closure after 2 months in the IL-2 (experimental) group was 60/211 (28.4%) compared to 46/248 (18.5%) in the control group, with a significant difference between the groups (P = 0.001). After treatment completion, the proportion of favorable outcomes was 559/560 (99.8%) in the experimental group and 587/591 (99.3%) in the control group, with no significant difference between the groups. Twelve months after treatment completion, relapse occurred in 15/560 (2.6%) in the IL-2 group and 19/591 (3.2%) in the control group, with no significant difference. CONCLUSION: IL-2 may enhance culture conversion and the cavity closure rate in the early treatment phase, although the enhancement may not be significant after treatment completion.

Functionalized Ultrasmall Iron Oxide Nanoparticles for T1-Weighted Magnetic Resonance Imaging of Tumor Hypoxia.

Hypoxia is a common biological condition in many malignant solid tumors that plays an imperative role in regulating tumor growth and impacting the treatment's therapeutic effect. Therefore, the hypoxia assessment is of great significance in predicting tumor development and evaluating its prognosis. Among the plenty of existing tumor diagnosis techniques, magnetic resonance imaging (MRI) offers certain distinctive features, such as being free of ionizing radiation and providing images with a high spatial resolution. In this study, we develop a fluorescent traceable and hypoxia-sensitive T1-weighted MRI probe (Fe3O4-Met-Cy5.5) via conjugating notable hypoxia-sensitive metronidazole moiety and Cy5.5 dye with ultrasmall iron oxide (Fe3O4) nanoparticles. The results of in vitro and in vivo experiments show that Fe3O4-Met-Cy5.5 has excellent performance in relaxivity, biocompatibility, and hypoxia specificity. More importantly, the obvious signal enhancement in hypoxic areas indicates that the probe has great feasibility for sensing tumor hypoxia via T1-weighted MRI. These promising results may unlock the potential of Fe3O4 nanoparticles as T1-weighted contrast agents for the development of clinical hypoxia probes.

Pulsatility protects the endothelial glycocalyx during extracorporeal membrane oxygenation.

BACKGROUND: Pulsatile flow protects vital organ function and improves microcirculatory perfusion during extracorporeal membrane oxygenation (ECMO). Studies revealed that pulsatile shear stress plays a vital role in microcirculatory function and integrity. The objective of this study was to investigate how pulsatility affects wall shear stress and endothelial glycocalyx components during ECMO. METHODS: Using the i-Cor system, sixteen canine ECMO models were randomly allocated into the pulsatile or the non-pulsatile group (eight canines for each). Hemodynamic parameters, peak wall shear stress (PWSS), serum concentration of syndecan-1, and heparan sulfate were measured at different time points during ECMO. Pulsatile shear stress experiments were also performed in endothelial cells exposed to different magnitudes of pulsatility (five plates for each condition), with cell viability, the expressions of syndecan-1, and endothelial-to-mesenchymal transformation (EndMT) markers analyzed. RESULTS: The pulsatile flow generated more surplus hemodynamic energy and preserved higher PWSS during ECMO. Serum concentrations of both syndecan-1 and heparan sulfate were negatively correlated with PWSS, and significantly lower levels were observed in the pulsatile group. Besides, non-pulsatility triggered EndMT and endothelial cells exposed to low pulsatility had the lowest possibility of EndMT. CONCLUSION: The maintenance of the PWSS by pulsatility during ECMO possesses beneficial effects on glycocalyx integrity. Moreover, pulsatility prevents EndMT in endothelial cells, and low pulsatility exhibits the best protective effects. The augmentation of pulsatility may be a plausible future direction to improve the clinical outcome in ECMO.

Anchoring Group Mediated Radiolabeling for Achieving Robust Nanoimaging Probes.

Radiolabeling counts for much in the functionalization of inorganic nanoparticles (NPs) because it endows NPs with high-sensitive imaging capacities apart from providing accurate pharmacokinetic information on the labeled particles, which makes the development of relevant radiolabeling chemistry highly desirable. Herein, a novel Ligand Anchoring Group MEdiated RAdioLabeling (LAGMERAL) method is reported, in which a polyethylene glycol (PEG) ligand with a diphosphonate (DP) terminal group plays a key role. It offers possibilities to radiolabel NPs through the spare coordination sites of the DP anchoring group. Through X-ray absorption spectroscopy studies, the coordination states of the foreign metal ions on the particle surface are investigated. In addition, radioactive Fe3 O4 NPs are prepared by colabeling the particles with 125 I at the outskirt of the particles through a phenolic hydroxyl moiety of the PEG ligand, and 99m Tc at the root of the ligand, respectively. In this way, the stabilities of these types of radiolabeling are compared both in vitro and in vivo to show the advantages of the LAGMERAL method. The outstanding stability of probe and simplicity of the labeling process make the current approach universal for creating advanced NPs with different combinations of functionalities of the inorganic NPs and radioactive properties of the metal radioisotopes.

Decreased mortality seen in rifampicin/multidrug-resistant tuberculous meningitis treated with linezolid in Shenzhen, China.

BACKGROUND: The morbidity of rifampicin/multidrug-resistant tuberculous meningitis (RR/MDR-TBM) has shown an increasing trend globally. Its mortality rate is significantly higher than that of non-rifampicin/multidrug-resistant tuberculous meningitis (NRR/MDR-TBM). This article aimed to explore risk factors related to RR/MDR-TBM, and compare therapeutic effects of linezolid (LZD)- and non-linezolid-containing regimen for RR/MDR-TB patients in Shenzhen city. Furthermore, we aimed to find a better therapy for pathogen-negative TBM with RR/MDR-TBM related risk factors. METHODS: We conducted a retrospective study enrolling 137 hospitalized cases with confirmed TBM from June 2014 to March 2020. All patients were divided into RR/MDR-TBM group (12 cases) and NRR/MDR-TBM group (125 cases) based on GeneXpert MTB/RIF and (or) phenotypic drug susceptibility test results using cerebral spinal fluid (CSF). The risk factors related to RR/MDR-TBM were investigated through comparing clinical and examination features between the two groups. The mortality rate of RR/MDR-TBM patients treated with different regimens was analyzed to compare their respective therapeutic effects. A difference of P < 0.05 was considered statistically significant. RESULTS: Most patients (111/137, 81%) were from southern or southwestern China, and a large proportion (72/137, 52.55%) belonged to migrant workers. 12 cases were RR/MDR-TBM (12/137, 8.8%) while 125 cases were NRR/MDR-TBM (125/137, 91.2%). The proportion of patients having prior TB treatment history in the RR/MDR-TBM group was significantly higher than that of the NRR/MDR-TBM group (6/12 vs. 12/125, 50% vs. 10.5%, P < 0.01). No significant difference was observed on other clinical and examination features between the two groups. Mortality was significantly lower in RR/MDR-TBM patients on linezolid-containing treatment regimen than those who were not (0/7 versus 3/5, 0% versus 60%, P = 0.045). CONCLUSIONS: The main related risk factor of RR/MDR-TBM is the history of anti-tuberculosis treatment. Linezolid-containing regimen appears to lower mortality rate of RR/MDR-TBM significantly in our study. We think Linezolid should be evaluated prospectively in the treatment of RR/MDR-TBM.

Rapidly liver-clearable rare-earth core-shell nanoprobe for dual-modal breast cancer imaging in the second near-infrared window.

BACKGROUND: Fluorescence imaging as the beacon for optical navigation has wildly developed in preclinical studies due to its prominent advantages, including noninvasiveness and superior temporal resolution. However, the traditional optical methods based on ultraviolet (UV, 200-400 nm) and visible light (Vis, 400-650 nm) limited by their low penetration, signal-to-noise ratio, and high background auto-fluorescence interference. Therefore, the development of near-infrared-II (NIR-II 1000-1700 nm) nanoprobe attracted significant attentions toward in vivo imaging. Regrettably, most of the NIR-II fluorescence probes, especially for inorganic NPs, were hardly excreted from the reticuloendothelial system (RES), yielding the anonymous long-term circulatory safety issue. RESULTS: Here, we develop a facile strategy for the fabrication of Nd3+-doped rare-earth core-shell nanoparticles (Nd-RENPs), NaGdF4:5%Nd@NaLuF4, with strong emission in the NIR-II window. What's more, the Nd-RENPs could be quickly eliminated from the hepatobiliary pathway, reducing the potential risk with the long-term retention in the RES. Further, the Nd-RENPs are successfully utilized for NIR-II in vivo imaging and magnetic resonance imaging (MRI) contrast agents, enabling the precise detection of breast cancer. CONCLUSIONS: The rationally designed Nd-RENPs nanoprobes manifest rapid-clearance property revealing the potential application toward the noninvasive preoperative imaging of tumor lesions and real-time intra-operative supervision.

Quantitative Mapping of Glutathione within Intracranial Tumors through Interlocked MRI Signals of a Responsive Nanoprobe.

Studies reveal that malignant tumors feature uneven distributions of some key biomarkers across the entire tumorous region. Nevertheless, only very limited progress has been made towards non-invasive and quantitative detection of tumor-specific biomarkers in vivo, especially with clinically compatible imaging modalities. Reported here is an Fe3 O4 nanoparticle-based glutathione (GSH) responsive magnetic resonance imaging (MRI) probe that can form particle aggregates within tumors in vivo to give rise to strong GSH concentration dependent interlocked relaxivities. A quantitative correlation between the interlocked MRI signals and local GSH concentration was established, and further applied for mapping the heterogeneous distribution of GSH within an intracranial tumor (2.4 mm × 1.6 mm) in vivo. This methodology will offer a practical route for quantitatively mapping tumor-specific biomarkers in vivo with unlimited detection depth, which largely challenges optical-imaging-based approaches.

Polymerase Chain Reaction Assays Reverted to Positive in 25 Discharged Patients With COVID-19.

We report the observation that 14.5% of COVID-19 patients had positive RT-PCR testing again after discharge. We describe correlations between laboratory parameters and treatment duration (P = .002) and time to virus recrudescence (P = .008), suggesting the need for additional measures to confirm illness resolution in COVID-19 patients.

Treatment Outcome of a Shorter Regimen Containing Clofazimine for Multidrug-resistant Tuberculosis: A Randomized Control Trial in China.

BACKGROUND: The emergence of multidrug-resistant tuberculosis (MDR-TB) poses a serious obstacle to global TB control programs. METHODS: We carried out a prospective, randomized, multicenter study in China that was focused on the potential of a shorter regimen containing clofazimine (CFZ) for the treatment of MDR-TB. There were 135 MDR-TB cases that met eligibility requirements and were randomly stratified into either the control group or experimental group. Patients in the control group received an 18-month treatment regimen, whereas patients in the experimental group received a 12-month treatment regimen containing CFZ. RESULTS: At the completion of the treatment period, the difference in sputum-culture conversion rates between the experimental group and the control group was not significant. Notably, by the end of 3 months of treatment, 68.7% patients receiving the experimental regimen had sputum-culture conversion, as compared with 55.9% of those receiving the control regimen; this was a significant difference, suggesting an early sputum conversion (P = .04). There were 67 adverse events reported in 56 patients in this study, including 32 in the control group and 35 in the experimental group. No significant difference in the overall incidences of adverse events was observed between the 2 groups. CONCLUSIONS: The MDR-TB patients treated with the shorter regimen containing CFZ had a comparable successful outcome rate when compared to those with the standard regimen. The patients assigned to the experimental group achieved more rapid sputum-culture conversion, reflecting superior antimicrobial activity against MDR-TB. CLINICAL TRIALS REGISTRATION: Chinese Clinical Trial Registry ChiCTR 1800020391.

Biodegradable Inorganic Nanoparticles for Cancer Theranostics: Insights into the Degradation Behavior.

Inorganic nanoparticles as a versatile nanoplatform have been broadly applied in the diagnosis and treatment of cancers due to their inherent superior physicochemical properties (including magnetic, thermal, optical, and catalytic performance) and excellent functions (e.g., imaging, targeted delivery, and controlled release of drugs) through surface functional modification or ingredient dopant. However, in practical biological applications, inorganic nanomaterials are relatively difficult to degrade and excrete, which induces a long residence time in living organisms and thus may cause adverse effects, such as inflammation and tissue cysts. Therefore, the development of biodegradable inorganic nanomaterials is of great significance for their biomedical application. This Review will focus on the recent advances of degradable inorganic nanoparticles for cancer theranostics with highlight on the degradation mechanism, aiming to offer an in-depth understanding of degradation behavior and related biomedical applications. Finally, key challenges and guidelines will be discussed to explore biodegradable inorganic nanomaterials with minimized toxicity issues, facilitating their potential clinical translation in cancer diagnosis and treatment.

Emitting/Sensitizing Ions Spatially Separated Lanthanide Nanocrystals for Visualizing Tumors Simultaneously through Up- and Down-Conversion Near-Infrared II Luminescence In Vivo.

Near-infrared lights have received increasing attention regarding imaging applications owing to their large tissue penetration depth, high spatial resolution, and outstanding signal-to-noise ratio, particularly those falling in the second near-infrared window (NIR II) of biological tissues. Rare earth nanoparticles containing Er3+ ions are promising candidates to show up-conversion luminescence in the first near-infrared window (NIR I) and down-conversion luminescence in NIR II as well. However, synthesizing particles with small size and high NIR II luminescence quantum yield (QY) remains challenging. Er3+ ions are herein innovatively combined with Yb3+ ions in a NaErF4 @NaYbF4 core/shell manner instead of being codoped into NaLnF4 matrices, to maximize the concentration of Er3+ in the emitting core. After further surface coating, NaErF4 @NaYbF4 @NaYF4 core/shell/shell particles are obtained. Spectroscopy studies are carried out to show the synergistic impacts of the intermediate NaYbF4 layer and the outer NaYF4 shell. Finally, NaErF4 @NaYbF4 @NaYF4 nanoparticles of 30 nm with NIR II luminescence QY up to 18.7% at room temperature are obtained. After covalently attaching folic acid on the particle surface, tumor-specific nanoprobes are obtained for simultaneously visualizing both subcutaneous and intraperitoneal tumor xenografts in vivo. The ultrahigh QY of down-conversion emission also allows for visualization of the biodistribution of folate receptors.

Monitoring the Opening and Recovery of the Blood-Brain Barrier with Noninvasive Molecular Imaging by Biodegradable Ultrasmall Cu2- xSe Nanoparticles.

The reversible and controllable opening and recovery of the blood-brain barrier (BBB) is crucial for the treatment of brain diseases, and it is a big challenge to noninvasively monitor these processes. In this article, dual-modal photoacoustic imaging and single-photon-emission computed tomography imaging based on ultrasmall Cu2- xSe nanoparticles (3.0 nm) were used to noninvasively monitor the opening and recovery of the BBB induced by focused ultrasound in living mice. The ultrasmall Cu2- xSe nanoparticles were modified with poly(ethylene glycol) to exhibit a long blood circulation time. Both small size and long blood circulation time enable them to efficiently penetrate into the brain with the assistance of ultrasound, which resulted in a strong signal at the sonicated site and allowed for photoacoustic and single-photon emission computed tomography imaging monitoring the recovery of the opened BBB. The results of biodistribution, blood routine examination, and histological staining indicate that the accumulated Cu2- xSe nanoparticles could be excreted from the brain and other major organs after 15 days without causing side effects. By the combination of the advantages of noninvasive molecular imaging and focused ultrasound, the ultrasmall biocompatible Cu2- xSe nanoparticles holds great potential for the diagnosis and therapeutic treatment of brain diseases.

Coordinatively Unsaturated Fe3+ Based Activatable Probes for Enhanced MRI and Therapy of Tumors.

Exogenous FeIII can be used for cancer magnetic resonance (MR) imaging and potentially for cancer treatment by a ferroptosis pathway or photothermal ablation. To achieve this, effective and accurate delivery of FeIII to cancerous sites is critical, requiring a balance of release kinetics of Fe3+ in tumorous and normal tissues. A nanoprobe is described consisting of upconversion luminescence (UCL) nanoparticles as a core and a coordinatively unsaturated FeIII -containing Fe3+ /gallic acid complex as a shell. Owing to the introduction of an unsaturated coordination structure, FeIII in the nanoprobe can be released only in the tumor microenvironment in response to the lightly acidic pH. The multiple UCLs are used for quantitatively visualizing the release of Fe3+ in vivo, whilst the release resultant serves as a photothermal agent. This nanoprobe exhibited ligand-free tumor targeting ability, activatable MR imaging performance, and efficacious therapeutic effects against tumors in vivo.

Dual-Ratiometric Target-Triggered Fluorescent Probe for Simultaneous Quantitative Visualization of Tumor Microenvironment Protease Activity and pH in Vivo.

The abnormal expression of tumor-associated proteases and lowered extracellular pH are important signatures strongly associated with cancer invasion, progression, and metastasis. However, their malignant effects were mainly identified using cell and tissue studies. To noninvasively visualize the heterogeneous distribution of these abnormal indicators in vivo and further disclose their collective behaviors, a target-triggered fluorescent nanoprobe composed of a ratiometric pH-sensitive dye, a near-infrared dye (Cy5.5), and biocompatible Fe3O4 nanoparticles was constructed. The pH-sensitive dye was linked through a peptide substrate of matrix metalloprotease-9 (MMP-9) with Fe3O4 nanoparticles to establish a Förster resonance energy transfer (FRET) system for sensing the pH of the tumor microenvironment. Cy5.5 served as an internal reference for forming a secondary ratiometric fluorescent system together with the activated pH dye to enable the visualization of protease activities in vivo. Extensive imaging studies using a mouse model of human colon cancer revealed that the overexpression of MMP-9 and abnormal microenvironmental pH quantitatively visualized by this dual-ratiometric probe are spatially heterogeneous and synergistically guide the tumor invasion in vivo.

A Dual-Modal Molecular Probe for Near-Infrared Fluorescence and Photoacoustic Imaging of Peroxynitrite.

Peroxynitrite (ONOO-), a reactive and short-lived biological oxidant, is closely related with many pathological conditions such as cancer. However, real-time in vivo imaging of ONOO- in tumors remains to be challenging. Herein, we develop a near-infrared fluorescence (NIRF) and photoacoustic dual-modal molecular probe (CySO3CF3) composed of a water-soluble hemicyanine dye caged with a trifluoromethyl ketone moiety for in vivo imaging of ONOO-. The trifluoromethyl ketone moiety can undergo a series of ONOO--induced cascade oxidation-elimination reactions, leading to sensitive and specific fluorescence and photoacoustic turn-on responses toward ONOO-; whereas, a zwitterionic structure of the hemicyanine component ensures good water-solubility. Thus, CySO3CF3 not only specifically detects ONOO- in solution and cells with the limit of detection down to 53 nM but also allows for NIRF and photoacoustic dual-modal imaging of ONOO- in the tumors of living mice.