A mitochondria-targeting lipid-small molecule hybrid nanoparticle for imaging and therapy in an orthotopic glioma model.

Hybrid lipid‒nanoparticle complexes have shown attractive characteristics as drug carriers due to their integrated advantages from liposomes and nanoparticles. Here we developed a kind of lipid-small molecule hybrid nanoparticles (LPHNPs) for imaging and treatment in an orthotopic glioma model. LPHNPs were prepared by engineering the co-assembly of lipids and an amphiphilic pheophorbide a‒quinolinium conjugate (PQC), a mitochondria-targeting small molecule. Compared with the pure nanofiber self-assembled by PQC, LPHNPs not only preserve the comparable antiproliferative potency, but also possess a spherical nanostructure that allows the PQC molecules to be administrated through intravenous injection. Also, this co-assembly remarkably improved the drug-loading capacity and formulation stability against the physical encapsulation using conventional liposomes. By integrating the advantages from liposome and PQC molecule, LPHNPs have minimal system toxicity, enhanced potency of photodynamic therapy (PDT) and visualization capacities of drug biodistribution and tumor imaging. The hybrid nanoparticle demonstrates excellent curative effects to significantly prolong the survival of mice with the orthotopic glioma. The unique co-assembly of lipid and small molecule provides new potential for constructing new liposome-derived nanoformulations and improving cancer treatment.

Metal-free colorimetric detection of pyrophosphate ions by the peroxidase-like activity of ATP.

Pyrophosphate (P2O74-, PPi) plays a vital role in ecological environment. Its elevated levels in water bodies can lead to eutrophication. Hence, its detection is extremely significant. Whereas most of the existing methods for the actual detection of PPi may cause environmental pollution or suffer from operational complexity. In this study, we introduced a sensitive and selective method for detecting PPi based on the fact that PPi can inhibit the peroxidase-like activity of adenosine 5'-triphosphate (ATP). This strategy not only eliminated the complexity of material preparation (ATP is commercialized), but also addressed the general need for metal ions in detecting PPi. The dynamic range of PPi detection was 1.0-200 µM and the detection limit was 74 nM. In addition, this strategy had been successfully applied to the determination of PPi in tap water and lake water. This work extends the application of natural biological small molecule ATP in the analysis and provides an innovative thought for the metal-free detection of PPi.

Colorimetric detection of ATP by inhibiting the Peroxidase-like activity of carbon dots.

Adenosine triphosphate (ATP) is the main energy currency for cells and an important biomolecule involved in cellular reactions, whose abnormal levels are closely related to physical disease, thus it is extremely important to establish a convenient, fast and simple ATP monitoring method. Toward this end, we developed a facile method for colorimetric detection of ATP on the basis of the inhibiting effect of ATP on the peroxidase-like activity of carbon dots (CDs). The detection principle of this method was utilizing the peroxidase-like activity of CDs, which catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to generate blue products. However, the introduction of ATP in the system can inhibit the generation of blue products, so ATP can be colorimetric detected. This method exhibited high sensitivity with a detection limit of 34 nM and a wide linear range (0.050-2.0 µM). The as-proposed colorimetric ATP sensor was capable of detecting ATP in real samples accurately.

A signal amplification strategy for prostate specific antigen detection via releasing oxidase-mimics from coordination nanoparticles by alkaline phosphatase.

A novel signal amplification method for prostate specific antigen (PSA) is developed by freeing fluorescein with photoinduced oxidase-like activity from coordination nanoparticles (CNPs) in the presence of alkaline phosphatase (ALP). CNPs loaded with fluorescein (F@CNPs) are obtained in aqueous solution by self-assembly using Tb3+ as metal ion, guanosine monophosphate (5'-GMP) as ligand, and fluorescein as signal molecule. The F@CNPs display outstanding properties of simple synthesis, low cost, good water solubility, negligible leakage and satisfactory load capacity. Fluorescein is quantitatively encapsulated in CNPs with a binding ratio of 92.72%. Meanwhile, ALP can specifically hydrolyze the phosphate group of 5'-GMP ligand, triggering the destruction of F@CNPs and leakage of fluorescein. Fluorescein, a photoinduced oxidase mimic, can catalyze the oxidation of non-fluorescent Amplex UltraRed (AUR) into fluorescent resorufin under LED lamp. This strategy exhibits good sensitivity for ALP detection. In addition, a new immunoassay for PSA is validated by labelling ALP on PSA antibody. The low detection limit of 0.04 ng mL-1 in detecting PSA is appropriate for PSA detection in real samples. Therefore, the work not only establishes a new strategy for ALP and PSA determination, but also provides a new conception for putting photoinduced oxidase-like fluorescein in practical application.

A siramesine-loaded metal organic framework nanoplatform for overcoming multidrug resistance with efficient cancer cell targeting.

Cancer is the leading cause of death and the most important obstacle to increasing life expectancy. With the sophisticated design and research of anticancer drugs, multidrug resistance to chemotherapy has become more and more common. After the emergence of multidrug resistance, the development of a new drug is beset with difficulties. The repurposing of non-anticancer drugs is thus a timely strategy for cancer therapy. Here, we highlight the potential of repurposing siramesine, a central nervous system drug for antitumor research and we construct a metal organic framework-based nanoplatform for effective intracellular accumulation and pH-response siramesine release. The released drug induces lysosome membrane permeabilization, leading to lysosomal cathepsins leakage and then results in cell apoptosis. Due to the modification of folic acids, the constructed drug delivery nanosystem shows good biocompatibility and efficient cancer cell targeting. Importantly, the drug delivery system shows enhanced anticancer efficacy in vitro, which not only effectively kills cancer cells but also kills multidrug resistant cells. Thus, the drug delivery nanosystem constructed in this study is thought to become a promising anticancer agent for cancer therapy and even overcoming multidrug resistance, which provides good prospects for biomedical applications.

Cetyltrimethylammonium chloride-loaded mesoporous silica nanoparticles as a mitochondrion-targeting agent for tumor therapy.

Mitochondria play an important role in supplying cellular energy, cell signaling and governing cell death. In addition, mitochondria have also been proved to be essential for tumor generation and development. Thus, mitochondrion-targeting therapeutics and treatments have emerged as promising strategies against cancer. However, the lack of mitochondrion-targeting agents has limited their application. To this end, we report cetyltrimethylammonium chloride-loaded mesoporous silica nanoparticles conjugated with human serum albumin (CTAC@MSNs-HSA) as a mitochondrion-targeting agent for anticancer treatment. As the structure-directing agent in the synthesis of MSNs, CTAC is stored within MSNs. Due to their desirable size and HSA receptor-mediated transcytosis, CTAC@MSNs-HSA show great cellular uptake and enhanced accumulation in the cytoplasm. Positively charged CTAC could actively target mitochondria by interacting with the negatively charged mitochondria membrane, and then lead to the dysfunction of mitochondria by decreasing mitochondrial potential and intracellular ATP levels, resulting in the necrosis and apoptosis of MCF-7 cells. Therefore, significant antitumor activity is observed by in vitro studies. Moreover, in vivo studies confirm that the CTAC@MSNs-HSA are able to induce cancer cell death and efficiently inhibit tumor growth. These results demonstrate the potential of CTAC@MSNs-HSA in cancer therapeutics as well as providing insights into mitochondrion-targeting treatment.

Enhancing the peroxidase-like activity of ficin by rational blocking thiol groups for colorimetric detection of biothiols.

The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.e., direct blocking with N-ethylmaleimide (NEM), or using tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to interrupt disulfide bonds then blocking thiol groups with NEM, were applied to block thiol groups of ficin, ficin-NEM (ficin-N) and ficin-TCEP-NEM (ficin-TN) were produced, respectively. The blocking of thiol groups accelerated the peroxidase activity dramatically. The peroxidase catalytic activity of ficin-N and ficin-TN toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2 was about 2.5-fold and 5-fold increase compared with ficin, respectively, which accompanied a color change from colorless to blue and followed classic Michaelis-Menten model. The kinetic parameters indicated that higher affinity of ficin-N (Km = 0.31) and ficin-TN (Km = 0.39) to H2O2 compared with ficin (Km = 0.58), and ficin-TN had the highest Kcat which increased by 6.5 times and 4.5 times for TMB and H2O2, respectively. According to these findings, a colorimetric method with high sensitivity for the detection of biothiols was developed due to sulfhydryl compounds inhibited the peroxidase activity of ficin. Comparing with ficin and ficin-N, ficin-TN had the widest detection range (0.01-16 µM) and the lowest detection limit (3 nM). The practical applications of ficin-TN for biothiol determination in human serum samples have been demonstrated with satisfactory results. Ficin-N and ficin-TN are promising to apply to the bioanalysis.

One-pot synthesis of a composite consisting of the enzyme ficin and a zinc(II)-2-methylimidazole metal organic framework with enhanced peroxidase activity for colorimetric detection for glucose.

An enzyme-metal organic framework (MOF) composite with saucer-like structure was prepared via one-pot synthesis from ficin (a cysteine proteolytic enzyme with POx activity), zinc(II) ions and 2-methylimidazole. The composites exhibit a 2.5-fold higher catalytic activity and stronger affinity for substrates compared to free ficin. This was exploited to design a colorimetric assay for the determination of glucose. The addition of glucose oxidase causes the formation of H2O2 which is catalytically oxidized by ficin to form a blue coloration that can be measured at 652 nm. The assay has a 0.12 µM detection limit and excellent selectivity. It was successfully applied to the determination of glucose in diluted serum samples. Graphical abstract Schematic presentation of the synthesis process and the enhanced peroxidase activity of ficin@MOF composites. Ficin was immobilized in a new saucer-like shape of Ficin@MOF composites, which showed higher peroxidase activity than free ficin. Scheme and graphical abstract contains poor quality of text.We have attach a new picture with 600 dpi as scheme and graphical abstract.

New optical method for the determination of ß-galactosidase and α-fetoprotein based on oxidase-like activity of fluorescein.

Fluorescein has been found as an efficient visible-light-induced oxidase mimic and its catalytic performance is group-dependent. Herein, a facile colorimetric strategy for ß-galactosidase (ß-gal) was developed using fluorescein di ß-D-galactopyranoside (FDG) as a probe based on the analyte induced change in oxidase mimicking activity of fluorescein derivatives. FDG doesn't possess any visible-light-induced oxidase activity and can generate fluorescein and fluorescein mono ß-D-galactopyranoside (FMG) in the presence of ß-gal. The in situ generated fluorescein and FMG possess high oxidase-like activities under visible-light illumination and could catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine (TMB) upon short irradiation by light-emitting diode (LED) lamp. Thus, the ß-gal activity can be selectively detected in linear range from 0.10 to 12.9 µg mL-1 with a limit of detection (LOD) of 0.04 µg mL-1. We further integrated with the visual detection of α-fetoprotein antigen (AFP) based on the corresponding colorimetric signal induced by ß-gal-linked colorimetric immunoassay, a LOD of 0.08 ng mL-1 could be achieved. Significantly, our proposed assay provides a facile sensing platform based on the change in enzyme mimicking activity induced by analytes. In addition, this optical method works without complex synthesis procedure and efficiently avoids participation of unstable H2O2 as an oxidant. Therefore, the present work not only shows the excellent assay performance in ß-gal and tumor biomarker detection, but also opens up a new avenue for its application in practical optical sensing.

Targeted H+-Triggered Bubble-Generating Nanosystems for Effective Therapy in Cancer Cells.

A novel targeting drug delivery system for cancer therapy based on H+-triggered bubble-generating nanosystems (BGNSs) was engineered. First, hollow mesoporous silica nanoparticles (HMSNs) were used to load doxorubicin (DOX). Then, the obtained drug-loaded HMSNs were treated with NaHCO3 to prepare the BGNSs. The BGNSs were coated with polydopamine (pDA), and finally, folic acids (FA) were anchored on the nanosystems to obtain the desired nanoscale drug delivery system (BGNSs@pDA-FA). BGNSs@pDA-FA was effectively internalized by cancer cells through folate receptor-mediated endocytosis and generated CO2 bubbles under the acidic environment of the lysosomes, thus enhancing lysosomal membrane permeability (LMP) to release caspase-3 into the cytoplasm, resulting in cancer cell death via an apoptosis-like pathway. Notably, we demonstrated that the BGNSs@pDA-FA exhibited a significant simultaneous synergetic cytotoxicity against MCF-7 cells and remarkably overcame the multidrug resistance (MDR) of MCF-7/ADR cells. Moreover, compared to free DOX and a nanosystem without FA modification (BGNSs), the BGNSs@pDA-FA induced relatively minor side effects in the MCF-10A cells. Therefore, the results showed that BGNSs@pDA-FA, as a targeted drug delivery system, have a good probability of overcoming the MDR of tumor cells with minor side effects on normal cells.

Aptamer-conjugated PEGylated quantum dots targeting epidermal growth factor receptor variant III for fluorescence imaging of glioma.

The extent of resection is a significant prognostic factor in glioma patients. However, the maximum safe resection level is difficult to determine due to the inherent infiltrative character of tumors. Recently, fluorescence-guided surgery has emerged as a new technique that allows safe resection of glioma. In this study, we constructed a new kind of quantum dot (QD)-labeled aptamer (QD-Apt) nanoprobe by conjugating aptamer 32 (A32) to the QDs surface, which can specially bind to the tumors. A32 is a single-stranded DNA capable of binding to the epidermal growth factor receptor variant III (EGFRvIII) specially distributed on the surface of glioma cells. To detect the expression of EGFRvIII in human brain tissues, 120 specimens, including 110 glioma tissues and 10 normal brain tissues, were examined by immunohistochemistry, and the results showed that the rate of positive expression of EGFRvIII in the glioma tissues was 41.82%, and 0.00% in normal brain tissues. Besides, the physiochemical properties of QD-Apt nanoparticles (NPs) were thoroughly characterized. Biocompatibility of the NPs was evaluated, and the results suggested that the QD-Apt was nontoxic in vivo and vitro. Furthermore, the use of the QD-Apt in labeling glioma cell lines and human brain glioma tissues, and target gliomas in situ was also investigated. We found that not only could QD-Apt specially bind to the U87-EGFRvIII glioma cells but also bind to human glioma tissues in vitro. Fluorescence imaging in vivo with orthotopic glioma model mice bearing U87-EGFRvIII showed that QD-Apt could penetrate the blood-brain barrier and then selectively accumulate in the tumors through binding to EGFRvIII, and consequently, generate a strong fluorescence, which contributed to the margins of gliomas that were visualized clearly, and thus, help the surgeons realize the maximum safe resection of glioma. In addition, QD-Apt can also be applied in preoperative diagnosis and postoperative examination of glioma. Therefore, these achievements facilitate the use of tumor-targeted fluorescence imaging in the diagnosis, surgical resection, and postoperative examination of glioma.

Intrinsic Peroxidase-like Activity of Ficin.

Ficin is classified as a sulfhydryl protease isolated from the latex of fig trees. In most cases, a particular enzyme fits a few types of substrate and catalyzes one type of reaction. In this investigation, we found sufficient proofs for the intrinsic peroxidase-like activity of ficin and designed experiments to examine its effectiveness in a variety of scenarios. Ficin can transform peroxidase substrates to colored products in the existence of H2O2. Our results also indicate that the active sites of peroxidase-like activity of ficin are different from that of protease, which reveals that one enzyme may catalyze more than one kind of substrate to perform different types of reactions. On the basis of these findings, H2O2 releasing from MCF-7 cells was detected successfully. Our findings support a wider application of ficin in biochemistry and open up the possibility of utilizing ficin as enzymatic mimics in biotechnology and environmental monitoring.

Efficacy of NGR peptide-modified PEGylated quantum dots for crossing the blood-brain barrier and targeted fluorescence imaging of glioma and tumor vasculature.

Delivery of imaging agents to brain glioma is challenging because the blood-brain barrier (BBB) functions as a physiological checkpoint guarding the central nervous system from circulating large molecules. Moreover, the ability of existing probes to target glioma has been insufficient and needs to be improved. In present study, PEG-based long circulation, CdSe/ZnS quantum dots (QDs)-based nanoscale and fluorescence, asparagines-glycine-arginine peptides (NGR)-based specific CD13 recognition were integrated to design and synthesize a novel nanoprobe by conjugating biotinylated NGR peptides to avidin-PEG-coated QDs. Our data showed that the NGR-PEG-QDs were nanoscale with less than 100 nm and were stable in various pH (4.0~8.0). These nanomaterials with non-toxic concentrations could cross the BBB and target CD13-overexpressing glioma and tumor vasculature in vitro and in vivo, contributing to fluorescence imaging of this brain malignancy. These achievements allowed groundbreaking technological advances in targeted fluorescence imaging for the diagnosis and surgical removal of glioma, facilitating potential transformation toward clinical nanomedicine.

Asn-Gly-Arg-modified polydopamine-coated nanoparticles for dual-targeting therapy of brain glioma in rats.

The blood-brain barrier (BBB) is the major clinical obstacle in the chemotherapeutic management of brain glioma. Here we synthesized a pH-sensitive dual-targeting doxorubicin (DOX) carrier to compromise tumor endothelial cells, enhance BBB transportation, and improve drug accumulation in glioma cells. The drug delivery system was constructed with polydopamine (PDA)-coated mesoporous silica nanoparticles (NPs, MSNs) and the PDA coating was functionalized with Asn-Gly-Arg (NGR), a ligand with specific affinity for cluster of differentiation 13 (CD13). MSN-DOX-PDA-NGR showed a higher intracellular accumulation in primary brain capillary endothelial cells (BCECs) and C6 cells and greater BBB permeability than the non-targeting NPs (MSN-DOX-PDA) did in vitro. Ex vivo and in vivo tests showed that MSN-DOX-PDA-NGR had a higher accumulation in intracranial tumorous tissue than the undecorated NPs did. Furthermore, the antiangiogenesis and antitumor efficacy of MSN-DOX-PDA-NGR were stronger than that of MSN-DOX-PDA. Therefore, these results indicate that the dual-targeting vehicles are potentially useful in brain glioma therapy.

A H(+)-triggered bubble-generating nanosystem for killing cancer cells.

We constructed a H(+)-triggered bubble-generating nanosystem (BGNS), which generated CO2 bubbles in the acidic environment of lysosomes after being internalized by cancer cells. The quickly generated bubbles caused enhanced lysosomal membrane permeabilization. As expected, H(+)-triggered BGNS possessed remarkable cytotoxicity against MCF-7 breast cancer cells, and successfully overcame the multidrug resistance of MCF-7/ADR cells.

Interaction of proteins with aluminum(III)-chlorophosphonazo III by resonance Rayleigh scattering method.

In weak acid medium, aluminum(III) can react with chlorophosphonazo III [CPA(III), H(8)L] to form a 1:1 coordination anion [Al(OH)(H(4)L)](2-). At the same time, proteins such as bovine serum albumin (BSA), lysozyme (Lyso) and human serum albumin (HSA) existed as large cations with positive charges, which further combined with [Al(OH)(H(4)L)](2-) to form a 1:4 chelate. This resulted in significant enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). In this study, we investigated the interaction between [Al(OH)(H(4)L)](2-) and proteins, optimization of the reaction conditions and the spectral characteristics of RRS, SOS and FDS. The maximum RRS wavelengths of different protein systems were located at 357-370 nm. The maximum SOS and FDS wavelengths were located at 546 and 389 nm, respectively. The scattering intensities (ΔI) of the three methods were proportional to the concentration of the proteins, within certain ranges, and the detection limits of the most sensitive RRS method were 2.6-9.3 ng/mL. Moreover, the chelate reaction mechanism or the reasons for the enhancement of RRS were discussed through absorption spectra, fluorescence spectra and circular dichroism (CD) spectra.

Rapid determination of the toxicity of quantum dots with luminous bacteria.

In this paper, a novel method so-called bioluminescence inhibition assay with luminous bacteria (Photobacterium phosphoreum) was introduced to evaluate the toxicity of quantum dots. The bioassay was based on measuring the decrease of the light emitted by luminous bacteria. With obvious advantages of simplicity, rapidity and sensitivity, it can dramatically improve the efficiency of probing the toxicity of QDs. Based on this method, we systemically explored the effect of the composition and surface modification on QDs' toxicity. The experiment of composition effect was performed using three kinds of QDs, namely CdSe, CdTe and ZnS-AgInS(2) QDs with the same stabilizer - dihydrolipoic acid. As for the effect of different stabilizers, mercaptoacetic acid, l-cysteine and dihydrolipoic acid stabilized CdSe were researched, respectively. Our results demonstrated that both the composition and surface modification were the important factors affecting the toxicity of QDs. In addition, a concentration dependence of toxicity was also found.

Quenching effect of nickel ions on fluorescent gold nanoparticles.

Herein, we reported the quenching effect of Ni(2+) on bovine serum albumin protected fluorescent gold nanoparticles (BSA-GNPs). The quenching mechanism was discussed and a static quenching mechanism was proposed. The number of binding sites (n), apparent stability constants (K) and corresponding thermodynamic parameters of BSA-GNPs-Ni(2+) complex were measured at different temperatures. Under optimum conditions, the fluorescence intensity of BSA-GNPs is linearly proportional to nickel concentration from 6.0x10(-8)mol/L to 8.0x10(-6)mol/L with a detection limit of 1.0x10(-8)mol/L. The result indicated that BSA-GNP was a potential Ni(2+) probe.

Oxidation of L-cysteine at a fluorosurfactant-modified gold electrode: lower overpotential and higher selectivity.

We describe the oxidation of L-cysteine (CySH) at a fluorosurfactant (i.e., Zonyl FSO)-modified gold electrode (FSO-Au). Significantly reduced anodic overpotential of CySH was observed. The FSO layer inhibited the adsorption of CySH and its oxidation products at the gold electrode surface, and the low coverage of the adsorbed thiol-containing species might account for the more facile electron-transfer kinetics of free CySH at low potentials. An electrochemical impedance spectroscopy study revealed the lower charge-transfer resistance of CySH oxidation at the FSO-Au electrode as compared to that at a bare gold electrode. Interestingly, although the FSO layer facilitated CySH oxidation, the anodic responses of other electroactive biological species such as glucose, uric acid, and ascorbic acid were generally suppressed. Furthermore, the modified electrode was capable of differentiating CySH from other low-molecular-mass biothiols such as homocysteine and glutathione. The unique features of the FSO-Au electrode allowed for the development of a highly selective method of detecting CySH in complex biological matrices. The direct determination of free reduced and total CySH in human urine samples has been successfully carried out without the assistance of any separation techniques.