A novel pH-activated AIEgen probe for dynamic lysosome tracking and high-efficiency photodynamic therapy.

A novel AIEgen molecular probe (N-3QL) with typical AIE effects, good biocompatibility, lysosome targeting, pH activation, excellent photostability, and high brightness was synthesized using two simple synthetic steps. Spectroscopic and cytotoxicity experiments indicate that N-3QL can not only be used for the dynamic monitoring of cancer cell lysosomes, but also for photodynamic therapy (PDT) ablation of cancer cells.

Endogenous Enzyme-Activatable Spherical Nucleic Acids for Spatiotemporally Controlled Signal Amplification Molecular Imaging and Combinational Tumor Therapy.

Due to the adjustable hybridization activity, antinuclease digestion stability, and superior endocytosis, spherical nucleic acids (SNAs) have been actively developed as probes for molecular imaging and the development of noninvasive diagnosis and image-guided surgery. However, since highly expressed biomarkers in tumors are not negligible in normal tissues, an inevitable background signal and the inability to precisely release probes at the chosen region remain a challenge for SNAs. Herein, we proposed a rationally designed, endogenous enzyme-activatable functional SNA (Ep-SNA) for spatiotemporally controlled signal amplification molecular imaging and combinational tumor therapy. The self-assembled amphiphilic polymer micelles (SM-ASO), which were obtained by a simple and rapid copper-free strain-promoted azide-alkyne cycloaddition click reaction between dibenzocyclooctyne-modified antisense oligonucleotide and azide-containing aliphatic polymer polylactic acid, were introduced as the core elements of Ep-SNA. This Ep-SNA was then constructed by connecting two apurinic/apyrimidinic (AP) site-containing trailing DNA hairpins, which could occur via a hybridization chain reaction in the presence of low-abundance survivin mRNA to SM-ASO through complementary base pairing. Notably, the AP site-containing trailing DNA hairpins also empowered the SNA with the feasibility of drug delivery. Once this constructed intelligent Ep-SNA nanoprobe was specifically cleaved by the highly expressed cytoplasmic human apurinic/apyrimidinic endonuclease 1 in tumor cells, three key elements (trailing DNA hairpins, antisense oligonucleotide, and doxorubicin) could be released to enable subsequent high-sensitivity survivin mRNA imaging and combinational cancer therapy (gene silencing and chemotherapy). This strategy shows great application prospects of SNAs as a precise platform for the integration of disease diagnosis and treatment and can contribute to basic biomedical research.

Tannic Acid-Assisted Biomineralization Strategy for Encapsulation and Intracellular Delivery of Protein Drugs.

Protein therapy has been considered to be one of the most direct and safe ways to regulate cell function and treat tumors. However, safe and effective intracellular delivery of protein drugs is still a key challenge. Herein, we developed a tannic acid-assisted biomineralization strategy for the encapsulation and intracellular delivery of protein drugs. RNase A and glucose oxidase (GOD) were choose as the protein drug model. RNase A, GOD, TA, and Mn2+ are mixed in one pot to attain RG@MT, and CaCO3 coating is subsequently carried out to construct RG@MT@C through biomineralization. Once RG@MT@C is endocytosed, the acidic environment of the lysosome will dissolve the protective layer of CaCO3 and produce plenty of CO2 to cause lysosome bursting, ensuring the lysosome escape of the RG@MT@C and thus releasing the generated TA-Mn2+, RNase A, and GOD into the cytoplasm. The released substances would activate starvation therapy, chemodynamic therapy, and protein therapy pathways to ensure a high performance of cancer therapy. Due to simple preparation, low toxicity, and controlled release in the tumor microenvironment, we expect it can realize efficient and nondestructive delivery of protein drugs and meet the needs for precise, high performance of synergistically antitumor therapy in biomedical applications.

A novel AIEgen photosensitizer with an elevated intersystem crossing rate for tumor precise imaging and therapy.

Herein, we have designed and synthesized a quinolinyl-AIE photosensitizer (TPE-4QL+) with an alternative elevated intersystem crossing (ISC) rate, which exhibits not only highly efficient photosensitivity but also high tumor cell specificity and an excellent mitochondrial targeting ability. In vitro experiments indicate that using TPE-4QL+ as a photosensitizer can induce a series of tumor cells to die with a low dose of radiation, but with no obvious toxicity to normal cells. The in vivo studies on a mouse model bearing a subcutaneous 4T1 xenograft also show that TPE-4QL+ can be used with high efficiency as a photosensitizer in PDT.

Microemulsion-Confined Assembly of Magnetic Nanoclusters for pH/H2O2 Dual-Responsive T2-T1 Switchable MRI.

In this work, a T2-T1 switchable superparamagnetic iron oxide nanoprobe with a pH/H2O2 dual response was obtained using a microemulsion method. This novel method for the controllable assembly of small iron clusters followed by their independent modification was reported, which could not be prepared by common synthetic methods. The size of the assembled nanoprobe was uniform and controllable, with a stable T2 magnetic resonance imaging (MRI) signal under a single condition. When the nanoprobe was exposed to the tumor environment, the higher H+ and H2O2 concentrations at the tumor site could dissociate the nanoprobe and redisperse into small iron clusters. When this occurred, the T2 MRI signal was converted into a T1 MRI signal, achieving specific detection of tumors by a pH/H2O2 dual-response T2-T1 MRI.

Microemulsion-Confined Biomineralization of PEGylated Ultrasmall Fe3O4 Nanocrystals for T2-T1 Switchable MRI of Tumors.

Ultrasmall superparamagnetic iron oxide nanoparticles (USPIONs) are a novel T1 contrast agent with good biocompatibility and switchable imaging signal that have not been widely applied for magnetic resonance imaging (MRI) because it is difficult to induce their relatively close ideal agglomeration. Here, by combining the microemulsion method with the biomineralization principle, a pH-responsive T2-T1 switchable MRI nanoprobe was constructed via the microemulsion-confined biomineralization of PEGylated USPIONs (PEG-USPIONs). The size of the formed CaCO3-coated PEG-USPION conjugates (PEG-USPIONs@CaCO3 nanoprobe) was uniform and controllable, and the preparation method was simple. The PEG-USPIONs inside the nanoconjugates agglomerate more tightly, and the T1-MRI signal of the nanoprobe is converted to the T2-MRI signal. When exposed to the acidic environment of the tumor tissue or internal organelles, the CaCO3-coating of the nanoprobes is dissolved, and free PEG-USPIONs are released, thus realizing the T1-weighted imaging of the tumors. The suitability of the PEG-USPIONs@CaCO3 nanoprobe for tumor MRI detection was successfully demonstrated using a mouse model bearing a subcutaneous 4T1 xenograft.

Synergistically enhanced multienzyme catalytic nanoconjugates for efficient cancer therapy.

Tumors are complex and highly variable, making it difficult for a single treatment strategy to be significantly effective for cancer therapy. Herein, we report a robust cascade biomimetic nanoplatform that integrates chemiluminescence-induced photodynamic therapy (CL-PDT), Fenton reaction-based chemodynamic therapy (CDT), and glucose oxidase (GOD)-mediated starvation therapy to synergistically enhance cancer treatment. For the nanoplatform of CPPO@porphyrin-MOF@Cancer cell membrane-GOD (C1@M@C2G), the ferric ion-linked porphyrin-MOF can trigger a Fenton reaction to reach CDT, the carried CPPO as an energy donor is used to excite a photo-sensitive porphyrin-MOF in situ to generate singlet oxygen (1O2) for PDT, GOD catalyzes glucose into H2O2 and gluconic acid to realize starvation therapy, and the cancer cell membrane wrapped onto the nanoparticle plays a key role in homologous targeting, which is conducive to achieving better therapeutic effects. Significantly, the porphyrin-MOF with catalase-like activity can generate O2 to effectively relieve tumor hypoxia, thereby enhancing the catalytic effect of GOD and the efficacy of PDT. Additionally, the produced H2O2 and gluconic acid can further improve the CPPO-H2O2-triggered CL-PDT and promote the low pH-dependence Fenton reaction-based CDT, respectively. Both in vitro and in vivo studies showed that the constructed nanoplatform displays an excellent cooperative anti-tumor performance, so we firmly believe that this simple nanoplatform broadens the pathway to fight against cancer through effective cascade catalysis.

PEGylated AIEgen molecular probe for hypoxia-mediated tumor imaging and photodynamic therapy.

We report a novel PEGylated aggregation-induced emission luminogen (AIEgen) molecular probe for hypoxia-mediated tumor imaging and photodynamic therapy by linking a PEG chain to the AIE-active photosensitizer via a hypoxia-sensitive azo group.

A CaO2 @Tannic Acid-FeIII Nanoconjugate for Enhanced Chemodynamic Tumor Therapy.

Chemodynamic therapy (CDT) is an effective tumor treatment strategy in which FeII reacts with hydrogen peroxide (H2 O2 ) in tumor cells to produce highly toxic hydroxyl radical (. OH) through the Fenton reaction. However, the content of endogenous H2 O2 in cells is limited, and the reaction between FeIII and H2 O2 is inefficient, greatly limiting the efficiency of the Fenton reaction and reducing the effectiveness of tumor treatment. Therefore, in this work, we designed and synthesized a new type of nano-system (CaO2 @TA-FeIII ) for the enhanced CDT of tumors, in which the polyphenolic compound- tannic acid (TA) and FeIII formed a TA-Fe nano-coating on the surface of calcium peroxide (CaO2 ) nanospherical aggregates. When the CaO2 @TA-FeIII nanoconjugates reach the tumor site, the CaO2 contained in the nanoconjugates produces H2 O2 after disintegration in tumor cells, and the carried TA rapidly reduces FeIII to FeII , solving the two major shortcomings in CDT of (1) insufficient content of H2 O2 in cancer cells, and (2) low catalytic efficiency of the Fenton reaction. Additionally, the . OH produced in the Fenton reaction induces oxidative stress for the tumor cells, promoting the occurrence of the "calcium overload" process, and thereby accelerating the death of tumor cells. Experimental results in vitro and in vivo showed that CaO2 @TA-FeIII nanoconjugates can effectively kill cancer cells and display an excellent tumor therapeutic effect. We believe that the CaO2 @TA-FeIII nanoconjugates are a promising new nano-platform for highly effective tumor treatment.

Biomineralization of Aggregation-Induced Emission-Active Photosensitizers for pH-Mediated Tumor Imaging and Photodynamic Therapy.

As an efficient, noninvasive, and high spatiotemporal resolved approach, photodynamic therapy (PDT) has high therapeutic potential for cancer treatment, whereas its development still faces a number of challenges, such as the lack of efficient and stable photosensitizers (PSs) and the inadequate ability of PSs to accumulate at tumor sites and target responses. Herein, a pH-responsive calcium carbonate (CaCO3)-mineralized AIEgen nanoprobe was prepared by using bovine serum albumin as the skeleton and loaded with a mitochondria-specific aggregation-induced emission (AIE)-active PS of 1-methyl-4-(4-(1,2,2-triphenylvinyl)styryl)quinolinium iodide (TPE-Qu+), which exhibits superior singlet oxygen (1O2)-generation ability and meanwhile possesses a bright near-infrared fluorescence emission. The biomineralized nanoparticles have small sizes (100 ± 10 nm) with good water dispersion and stability. With an increase in acidity (pH = 7.4-5.0), the internal TPE-Qu+ molecules are released gradually and accumulated in the mitochondria due to their hydrophobicity and electropositivity and then generate fluorescence emission and PDT under an external light source. Tumor inhibition and low acute toxicity were further successfully confirmed by the intracellular uptake test and 4T1-tumor-bearing mouse model.

Self-Illuminated, Oxygen-Supplemented Photodynamic Therapy via a Multienzyme-Mimicking Nanoconjugate.

Current photodynamic therapy (PDT) faces several intrinsic limitations, including insufficient oxygen supply and limited penetration of external light sources. Herein, we report a nanoconjugate, which, in response to the elevated hydrogen peroxide levels associated with tumor tissues, can supplement the oxygen needed for PDT and provide local self-illumination. Consisting of a MnFe2O4 core, a metal-organic framework shell loaded with the chemiluminescence reagent luminol, and a hyaluronic acid surface coating, the nanoconjugate is highly effective for suppressing cancer tissues in vivo via PDT in the absence of externally delivered light.

Catalytic Hairpin Self-Assembly-Based SERS Sensor Array for the Simultaneous Measurement of Multiple Cancer-Associated miRNAs.

The abnormal expression of some miRNAs is often closely related to the development of tumors. Available detection methods or biosensors that can simultaneously quantify multiple miRNAs in a single sample have rarely been reported. Herein, a novel catalytic hairpin self-assembly (CHA)-based surface-enhanced Raman scattering (SERS) sensor array was developed to simultaneously measure multiple miRNAs associated with cancer in one sample. The sensor array with four different sensing units was constructed by immobilizing one of four different hairpin-structured DNA sequence 1 (hp1) onto one of four Au/Ag alloy nanoparticle (AuAgNP)-coated detection wells. When target miRNA is present, the SERS tags, which were prepared by modifying AuAgNPs with a Raman reporter molecule of 4-mercaptobenzonitrile (MPBN) and the related hairpin-structured DNA sequence 2 (hp2), were captured onto the corresponding sensor unit through a repeated specific CHA reaction. This generated many "hot spots" because of interactions between the SERS tags and the AuAgNP layer-coated surface of the sensor, which ultimately produced a strong SERS signal that allowed the detection of target miRNAs with the detection limit of 0.15 pM. Using this SERS sensor array, multiple cancer-associated miRNAs (miR-1246, miR-221, miR-133a, and miR-21) were successfully determined in buffer, serum, and cellular RNA extracts.

Microsphere-based suspension array for simultaneous recognition and quantification of multiple cancer-associated miRNA via DNAzyme-Mediated signal amplification.

Herein, a novel suspension array of polystyrene (PS) beads for simultaneous recognition and quantification of multiple cancer-associated microRNAs (miRNAs) using flow cytometry has been reported. The suspension array contained three moieties, streptavidin-modified PS beads, biotin-labeled substrate strands (17S) of the 17-8 DNAzyme and two split DNAzyme parts (PA, PB). 17S was labeled with 6-carboxyfluorescein (FAM) and Dabcyl on both sides of the ribonucleic acid. Once the target miRNAs appear, they can bind with the corresponding PA and PB to form an active secondary structure of DNAzyme. The active DNAzyme can cleave 17S and remove Dabcyl from the bead's surface, thus recovering the FAM's fluorescence intensity. Furthermore, the released target miRNA can autonomously move to the neighboring inactive DNAzyme for further cleavage, thus amplifying the fluorescence signal. Therefore, the target miRNAs can be quantified by reading the fluorescence intensity output from flow cytometry. The PS beads-based suspension array for the target miRNA in buffer shows good selectivity and high sensitivity. Via binding with a different pair of PA and PB, this suspension sensor array has successfully typed and quantified cancer-associated miRNAs of miR-21, miR-155, miR-335, and miR-122 in buffer and serum conditions.

A novel surface-enhanced Raman scattering-based ratiometric approach for detection of hyaluronidase in urine.

A ratiometric surface-enhanced Raman scattering (SERS) based method is described for the determination of the activity of hyaluronidase (HAase). Gold nanorods (AuNRs) were functionalized with 4-thiobenzonitrile (TBN) to act as the Raman reporter (TBN-AuNRs), and 4-thiophenylacetylene-functionalized gold-silver alloy nanoparticles (TPA-AuAgNPs) were used as the reference. Hyaluronic acid (HA) acts as the HAase recognition element. The TBN-modified AuNRs aggregate in the presence of HA due to the strong electrostatic interaction between the positively charged TBN-AuNRs and negatively charged HA. This strongly enhances the Raman signal of TBN at 2220 cm-1. However, HA has no significant effect on the dispersion of the modified AuAg NPs which are electroneutral. Hence, no change can be seen in the Raman intensity of TPA at 1974 cm-1. In the presence of HAase, HA is digested into smaller fragments. This results in good dispersion of the TBN-AuNRs and a weaker TBN Raman signal. Hence, the ratio of the Raman peaks at 1974 and 2220 cm-1 increases. Under the optimized conditions, the ratio changes in the 5-70 U mL-1 HAase activity range, and the detection limit is 1.7 U mL-1 (based on the 3σ rule). Moreover, this method has been successfully applied in the determination of the activity of HAase in artificial urine and it is expected to be a new method for the diagnosis of cancer, especially bladder cancer.

Target MicroRNA-Responsive DNA Hydrogel-Based Surface-Enhanced Raman Scattering Sensor Arrays for MicroRNA-Marked Cancer Screening.

On the basis of a target microRNA (miRNA)-responsive DNA hydrogel, a novel surface-enhanced Raman scattering (SERS) sensor array with nine sensor units that can detect multiple cancer-related miRNAs in one sample was developed. The target miRNA-responsive DNA hydrogel was first formed in each sensor unit to realize the construction of the DNA hydrogel-based SERS sensor array. Initially, because of the blocking of the streptavidin (SA)-modified sensor units by the formed DNA hydrogel, the SERS tags (biotin/4-mercaptobenzonitrile-functionalized AuAg alloy nanoparticles (B/M-AuAgNPs)) could not pass through the hydrogel and bind to the SA-modified sensor surface; thus, obvious Raman signals could not be observed. After the introduction of the target miRNA, DNA hydrogels of the corresponding sensor unit were disintegrated accordingly, and SERS tags were able to pass through the hydrogel to be captured onto the SA-modified detection surface, thus resulting in strong Raman signals and the detection of target miRNA. The assay is validated under clean buffer conditions as well as in serum. This target miRNA-responsive DNA hydrogel-based SERS sensor array has attractive application prospects in cancer typing via blood miRNA measurements.

Two-Photon Excitation/Red Emission, Ratiometric Fluorescent Nanoprobe for Intracellular pH Imaging.

Herein, we describe a novel two-photon excitation/red emission-based ratiometric pH nanosensor consisting of a pH-sensitive two-photon dye and Tm3+-doped upconversion nanoparticles (UCNP). The fluorescence emission ratio between the dye (610 nm) and UCNPs (810 nm) (I610/I810) provides a linear indicator of pH values in the range from pH 4.0 to 6.5 with high sensitivity. These nanoprobes selectively accumulate in the lysosomes of cells, making them suitable for lysosomal pH tracking. This pH nanoprobe has been successfully applied in visualizing chemically stimulated changes of intracellular pH in living cells and tissues.

Alkyne/Ruthenium(II) Complex-Based Ratiometric Surface-Enhanced Raman Scattering Nanoprobe for In Vitro and Ex Vivo Tracking of Carbon Monoxide.

Here, we report a surface-enhanced Raman scattering (SERS) nanosensor for real-time ratiometric detection of carbon monoxide (CO) based on a ligand displacement mechanism. This nanoprobe consists of a gold-silver (Au-Ag) alloy nanoparticle core as the highly active SERS substrate, an alkyne/ruthenium(II) (alkyne/Ru(II)) complex immobilized on the surface as the CO-sensing element, and a porous silica shell to improve the stability and biocompatibility of the particle. Displacement of the alkyne ligand by CO results in a decrease of the alkyne vibrations and an increase of the metal carbonyl complex signals, thus allowing the effective ratiometric detection of CO in real-time. The great potential of this assay for CO detection is validated in clean buffer environments, live cells, and tissue slices.

Cyclodextrin supramolecular inclusion-enhanced pyrene excimer switching for highly selective detection of RNase H.

Here, we report a novel fluorescence method for the highly selective and sensitive detection of RNase H by combining the use of a dual-pyrene-labeled DNA/RNA duplex with supramolecular inclusion-enhanced fluorescence. Initially, the probe is in the "off" state due to the rigidness of the double-stranded duplex, which separates the two pyrene units. In the presence of RNase H, the RNA strand of the DNA/RNA duplex will be hydrolyzed, and the DNA strand transforms into a hairpin structure, bringing close the two pyrene units which in turn enter the hydrophobic cavity of a γ-cyclodextrin. As a result, the pyrene excimer emission is greatly enhanced, thereby realizing the detection of RNase H activity. Under optimal conditions, RNase H detection can be achieved in the range from 0.08 to 4 U/mL, with a detection limit of 0.02 U/mL.

A spherical nucleic acid-based two-photon nanoprobe for RNase H activity assay in living cells and tissues.

We report here a two-photon nanoprobe for the detection of RNase H activity in living cells and ex vivo tissues by combining a two-photon dye with a spherical nucleic acid (SNA) featuring a DNA/RNA duplex corona and a gold nanoparticle core.

Nanoconjugates of Ag/Au/Carbon Nanotube for Alkyne-Meditated Ratiometric SERS Imaging of Hypoxia in Hepatic Ischemia.

We report a ratiometric surface-enhanced Raman scattering (SERS) nanoprobe for imaging hypoxic living cells or tissues, using azo-alkynes assembled on a single-walled carbon nanotube (SWCNT) surface-functionalized with Ag/Au alloy nanoparticles (SWCNT/Ag/AuNPs). Under a hypoxic condition, azobenzene derivatives preassembled on the surface of the nanostructures are reduced stepwise by various reductases and eventually removed from the surface of the SWCNT/Ag/AuNPs, resulting in the loss of characteristic alkyne Raman bands at 2207 cm-1. Using 2D-band of SWCNTs at 2578 cm-1 as the internal standard, we are able to determine the hypoxia level based on the ratio of two peak intensities ( I2578/ I2207) as demonstrated by the successful detection in different cell lines and rat liver tissue samples derived from hepatic ischemia surgery. By combining the outstanding anti-interference property of alkynes as SERS reporters and the distinct Raman responses of alkynes and SWCNTs in complex systems, this novel ratiometric SERS strategy holds promise in becoming a very useful tool for in vitro and in vivo monitoring of hypoxia in research and clinical settings.