Harnessing the Potential of a Nitroreductase-Responsive Fluorescent Probe for the Diagnosis of Bacterial Keratitis.

Bacterial keratitis, an ocular emergency, is the predominant cause of infectious keratitis. However, diagnostic procedures for it are invasive, time-consuming, and expeditious, thereby limiting effective treatment for the disease in the clinic. It is imperative to develop a timely and convenient method for the noninvasive diagnosis of bacterial keratitis. Fluorescence imaging is a convenient and noninvasive diagnostic method with high sensitivity. In this study, a type of nitroreductase-responsive probe (NTRP), which responds to nitroreductase to generate fluorescence signals, was developed as an activatable fluorescent probe for the imaging diagnosis of bacterial keratitis. Imaging experiments both in vitro and in vivo demonstrated that the probe exhibited "turn-on" fluorescence signals in response to nitroreductase-secreting bacteria within 10 min. Furthermore, the fluorescence intensity reached its highest at 4 or 6 h in vitro and at 30 min in vivo when the excitation wavelength was set at 520 nm. Therefore, the NTRP has the potential to serve as a feasible agent for the rapid and noninvasive in situ fluorescence diagnosis of bacterial keratitis.

Nitroreductase-responsive nanoparticles for in situ fluorescence imaging and synergistic antibacterial therapy of bacterial keratitis.

As bacterial keratitis progresses rapidly, prompt intervention is necessary. Current diagnostic processes are time-consuming and invasive, leading to improper antibiotics for treatment. Therefore, innovative strategies for diagnosing and treating bacterial keratitis are urgently needed. In this study, Cu2-xSe@BSA@NTRP nanoparticles were developed by loading nitroreductase-responsive probes (NTRPs) onto Cu2-xSe@BSA. These nanoparticles exhibited integrated fluorescence imaging and antibacterial capabilities. In vitro and in vivo experiments showed that the nanoparticles produced responsive fluorescence signals in bacteria within 30 min due to an interaction between the released NTRP and bacterial endogenous nitroreductase (NTR). When combined with low-temperature photothermal therapy (PTT), the nanoparticles effectively eliminated E. coli and S. aureus, achieved antibacterial efficacy above 95% and facilitated the re-epithelialization process at the corneal wound site in vivo. Overall, the Cu2-xSe@BSA@NTRP nanoparticles demonstrated potential for rapid, noninvasive in situ diagnosis, treatment, and visualization assessment of therapy effectiveness in bacterial keratitis.

Using host-guest interactions at the interface of quantum dots to load drug molecules for biocompatible, safe, and effective chemo-photodynamic therapy against cancer.

Combining photodynamic therapy (PDT) and chemotherapy (CHT) by loading an anti-cancer drug and a photosensitizer (PS) into the same delivery nanosystem has been proposed as an effective approach to achieve synergistic effects for a safe cancer treatment. However, exploring an ideal delivery nanosystem has been challenging, because the noncovalent interactions must be maintained between the multiple components to produce a stable yet responsive nanostructure that takes into account the encapsulation of drug molecules. We addressed this issue by engineering the interfacial interaction between Ag2S quantum dots (QDs) using a pillararene derivative to direct the co-self-assembly of the entire system. The high surface area-to-volume ratio of the Ag2S QDs provided ample hydrophobic space to accommodate the anti-drug molecule doxrubicine. Moreover, Ag2S QDs served as PSs triggered by 808 nm near-infrared (NIR) light and also as carriers for high-efficiency delivery of drug molecules to the tumor site. Drug release experiments showed smart drug release under the acidic microenvironments (pH 5.5) in tumor cells. Additionally, the Ag2S QDs demonstrated outstanding PDT ability under NIR light, as confirmed by extracellular and intracellular reactive oxygen species generation. Significant treatment efficacy of the chemo-photodynamic synergistic therapy for cancer using the co-delivery system was demonstrated via in vitro and in vivo studies. These findings suggest that our system offers intelligent control of CHT and PDT, which will provide a promising strategy for constructing hybrid systems with synergistic effects for advanced applications in biomedicine, catalysis, and optoelectronics.

IGF1 receptor-targeted black TiO2 nanoprobes for MRI-guided synergetic photothermal-chemotherapy in drug resistant pancreatic tumor.

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest malignant tumors with features of matrix barrier caused poor drug permeability, and susceptibility to drug resistance. Herein, a PDAC and its stromal cell dual-targeted photothermal-chemotherapy strategy is explored to loosen the matrix and reverse drug resistance. To achieve this goal, black TiO2-Gd nanocomposites were conjugated with insulin like growth factor 1 (IGF1), and loaded with gemcitabine (GEM) to construct bTiO2-Gd-IGF1-GEM nanoprobes. In vitro results show that under 808 nm near-infrared irradiation, killing effect of the nanoprobes on drug-resistant MIA PaCa-2 cell is 3.3 times than that of GEM alone. In vivo experiments indicate the synergetic photothermal-chemotherapy not only loosens fibrous matrix of pancreatic tumor model, but also dramatically inhibits tumor growth, and almost completely eradicates the tumor after 12 days of treatment. In addition, relaxation rate of the nanoprobes is 8.2 times than commercial contrast agent Magnevist, therefore boosts the signal of magnetic resonance imaging in pancreatic tumor. In conclusion, our results reinforce that the prepared nanoprobes are promising to break matrix barrier and overcome drug resistance in PDAC.

Maltodextrin-Conjugated Gd-Based MRI Contrast Agents for Specific Diagnosis of Bacterial Infections.

Bacterial infections are one of the most serious health risks worldwide, and their rapid diagnosis remains a major challenge in clinic. To enhance the relaxivity and bacterial specificity of magnetic resonance imaging (MRI) contrast agents, here, a kind of gadolinium-based nanoparticles (NPs) of impressive biocompatibility is constructed as a contrast agent for maltodextrin-mediated bacteria-targeted diagnosis. To realize this, positively charged ultrasmall gadolinium oxide (Gd2O3, 2-3 nm) NPs are embedded in mesoporous silica NPs (MSN) with pore size around 6.38 nm. The resulting Gd2O3@MSN exhibits enhanced r1 value and T1-weighted MRI performance. Interestingly, upon conjugation of Gd2O3@MSN with maltodextrin to produce Gd2O3@MSN-Malt NPs, a remarkable decrease in internalization by osteosarcoma cells, alongside an increased adsorption toward E. coli and S. aureus, is achieved. It is therefore conceivable that the bacteria-targeted Gd2O3@MSN-Malt might be a promising MRI contrast agent for effective discrimination of bacterial infections from tumor.

Research advances in integrated theranostic probes for tumor fluorescence visualization and treatment.

At present, cancer is obviously a major threat to human health worldwide. Accurate diagnosis and treatment are in great demand and have become an effective method to alleviate the development of cancer and improve the survival rate of patients. A large number of theranostic probes that combine diagnosis and treatment methods have been developed as promising tools for tumor precision medicine. Among them, fluorescent theranostic probes have developed rapidly in the frontier research field of precision medicine with their real time, low toxicity, and high-resolution merit. Therefore, this review focuses on recent advances in the development of fluorescent theranostic probes, as well as their applications for cancer diagnosis and treatment. Initially, small-molecule fluorescent theranostic probes mainly including tumor microenvironment-responsive fluorescent prodrugs and phototherapeutic probes were introduced. Subsequently, nanocomposite probes are expounded based on four types of nano-fluorescent particles combining different therapies (chemotherapy, photothermal therapy, photodynamic therapy, gene therapy, etc.). Then, the capsule-type "all in one" probes, which occupy an important position in theranostic probes, are summarized according to the surface carrier type. This review aims to present a comprehensive guide for researchers in the field of tumor-related theranostic probe design and development.

A ZIF-90 nanoplatform loaded with an enzyme-responsive organic small-molecule probe for imaging the hypoxia status of tumor cells.

Hypoxia is one of the most common and important features occurring across a wide variety of malignancies, which can have adverse effects on the therapeutic outcomes of chemotherapy and radiotherapy. Therefore, the characterization of tumor hypoxia is of great importance in clinical tumor treatment. Herein, we firstly develop a new spectroscopic off-on probe with high sensitivity (detection limit: 5.8 ng mL-1) and good selectivity for fluorescence imaging the hypoxic status of tumor cells via its enzymatic reaction with nitroreductase in vitro and in vivo in the presence of dimethyl sulfoxide (DMSO) as a co-solvent. Inspired by the recent investigations on metal-organic frameworks (MOFs), a dual pH and ATP-responsive ZIF-90 nanoplatform was synthesized, and then PEG was post-modified through a Schiff base reaction. This allows the platform to serve as a carrier to load the hypoxia-responsive probe to investigate its response to enzyme in cells and in mice without using dimethyl sulfoxide as a co-solvent. Consequently, the two probes we synthesized here can successfully respond to nitroreductase for turn-on fluorescence imaging at a cellular level and in tumor-bearing mice. This is the first time that an enzyme-responsive organic small-molecule probe has been mounted on one of the MOFs. Our results open up a promising way for the design and application of both enzyme-responsive probes and MOFs.

Nanozymes-Engineered Metal-Organic Frameworks for Catalytic Cascades-Enhanced Synergistic Cancer Therapy.

The efficiency of chemical intercommunication between enzymes in natural networks can be significantly enhanced by the organized catalytic cascades. Nevertheless, the exploration of two-or-more-enzymes-engineered nanoreactors for catalytic cascades remains a great challenge in cancer therapy because of the inherent drawbacks of natural enzymes. Here, encouraged by the catalytic activity of the individual nanozyme for benefiting the treatment of solid tumors, we propose an organized in situ catalytic cascades-enhanced synergistic therapeutic strategy driven by dual-nanozymes-engineered porphyrin metal-organic frameworks (PCN). Precisely, catalase-mimicking platinum nanoparticles (Pt NPs) were sandwiched by PCN, followed by embedding glucose oxidase-mimicking ultrasmall gold nanoparticles (Au NPs) within the outer shell, and further coordination with folic acid (P@Pt@P-Au-FA). The Pt NPs effectively enabled tumor hypoxia relief by catalyzing the intratumoral H2O2 to O2 for (1) enhancing the O2-dependent photodynamic therapy and (2) subsequently accelerating the depletion of ß-d-glucose by Au NPs for synergistic starving-like therapy with the self-produced H2O2 as the substrate for Pt NPs. Consequently, a remarkably strengthened antitumor efficiency with prevention of tumor recurrence and metastasis was achieved. This work highlights a rationally designed tumor microenvironment-specific nanoreactor for opening improved research in nanozymes and provides a means to design a catalytic cascade model for practical applications.

A novel non-enzymatic hydrolytic probe for dipeptidyl peptidase IV specific recognition and imaging.

A novel non-enzymatic hydrolytic probe for DPP IV is obtained. And this new probe can be used for special DPP IV recognition and imaging in living cells. Importantly, one general strategy for the construction of new non-enzymatic fluorescent probes for many important proteases can be proposed based on the present study.

A Ultrasensitive Near-Infrared Fluorescent Probe Reveals Pyroglutamate Aminopeptidase 1 Can Be a New Inflammatory Cytokine.

Previous study showed that pyroglutamate aminopeptidase 1 (PGP-1) has a relationship with the immune response in cells. However, whether PGP-1 is involved in inflammatory response in vivo and can serve as a new inflammatory cytokine are still unclear. To address these issues, a new near-infrared fluorescent probe, which exhibits high selectivity and super sensitivity, is developed. With this probe, the up-regulation of PGP-1 (evidenced by western blot) in BALB/c mice legs and livers under the stimulation of two main immunopotentiators is revealed for the first time. The occurrence of inflammatory process (including tissue necrosis) in mice is determined by up-regulation of tumor necrosis factor-α and hematoxylin-eosin staining. Interestingly, it is revealed for the first time that knocking down PGP-1 leads to the weakness of inflammatory process in RAW264.7 cells. These new findings suggest that PGP-1 is indeed involved in inflammatory response in vivo and can be a new inflammatory cytokine.

Y1 receptor ligand-based nanomicelle as a novel nanoprobe for glioma-targeted imaging and therapy.

Due to the molecular and cellular heterogeneity of glioma, discovery of novel targeted sites and ligands for glioma imaging and therapy remains challenging. Neuropeptide Y (NPY) Y1 receptors (Y1Rs) are highly over expressed in various brain tumors including glioma, and can serve as potential targeting sites for glioma imaging and therapy. Here, we show by in vivo fluorescent imaging that a highly selective Y1R ligand, [Asn6, Pro34] NPY (AP-NPY), facilitated circumvention of the blood brain barrier (BBB) by nanomicelles specifically targeting glioma. Modification with AP-NPY stabilized doxorubicin-loaded nanomicelles in the normal physiological state and promoted drug release in the acidic tumor microenvironment. Furthermore, targeted delivery of AP-NPY nanomicelles improved the therapeutic efficacy of doxorubicin for glioma, producing a prolonged survival rate. These results suggest that Y1R is a novel targeted receptor, and its selective ligand AP-NPY improves BBB permeability and glioma targeting. Our study paves the way for developing a novel delivery system for diagnosis and treatment of glioma in which Y1Rs are over expressed.

Paramagnetic and Superparamagnetic Inorganic Nanoparticles for T1-Weighted Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) has become a promising technique in the early diagnosis of cancers, especially the application of contrast agents can further enhance the detection limit. Compared with the dark signal in "negative" contrast agents (T2), "positive" contrast agents (T1) with bright signal are more desirable for high-resolution imaging. However, the clinically used gadolinium complexes have short circulation time and the risk of nephrogenic system fibrosis. Therefore, to overcome the disadvantage of T2 agents and traditional T1 agents, it is very interesting to develop nano-scaled T1-weighted MRI contrast agents with safer and more precise imaging performance. The present review systematically summarized the recent progress of paramagnetic and superparamagnetic inorganic nanoparticles as T1-weighted MRI contrast agents, including gadolinium oxide nanoparticles, gadoliniumbased upconversion nanoparticles, manganese oxide nanoparticles, and ultra-small iron oxide nanoparticles. Moreover, we also described their applications in multi-modal imaging and visualized theranostics.

A novel fibroblast activation protein-targeted near-infrared fluorescent off-on probe for cancer cell detection, in vitro and in vivo imaging.

A new hemicyanine-based fibroblast activation protein-targeted near-infrared fluorescent probe is designed and it shows high selectivity and sensitivity to cancer cell detection, and in vitro and in vivo imaging. This probe is successfully applied in fluorescence detection of living cells (with a detection limit of 1500 cells per mL). It is believed that many new functions or distributions of FAP could be discovered by this new probe later.

808 nm-excited upconversion nanoprobes with low heating effect for targeted magnetic resonance imaging and high-efficacy photodynamic therapy in HER2-overexpressed breast cancer.

To avoid the overheating effect of excitation light and improve the efficacy of photodynamic therapy (PDT) of upconversion nanoplatform, a novel nanoprobe based on 808 nm-excited upconversion nanocomposites (T-UCNPs@Ce6@mSiO2) with low heating effect and deep penetration has been successfully constructed for targeted upconversion luminescence, magnetic resonance imaging (MRI) and high-efficacy PDT in HER2-overexpressed breast cancer. In this nanocomposite, photosensitizers (Ce6) were covalently conjugated inside of mesoporous silica to enhance the PDT efficacy by shortening the distance of fluorescence resonance energy transfer and to decrease the cytotoxicity by preventing the undesired leakage of Ce6. Compared with UCNPs@mSiO2@Ce6, UCNPs@Ce6@mSiO2 greatly promoted the singlet oxygen generation and amplified the PDT efficacy under the excitation of 808 nm laser. Importantly, the designed nanoprobe can greatly improve the uptake of HER2-positive cells and tumors by modifying the site-specific peptide, and the in vivo experiments showed excellent MRI and PDT via intravenous injection by modeling MDA-MB-435 tumor-bearing nude mice. Our strategy may provide an effective solution for overcoming the heating effect and improving the PDT efficacy of upconversion nanoprobes, and has potential application in visualized theranostics of HER2-overexpressed breast cancer.