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Peroxidase (POD)-like nanozymes have been found to act as nanoreactors for the generation of reactive oxygen species (ROS) to resolve drug resistance in the tumor microenvironment (TME). Amplifying cellular oxidative stress is considered to be a drug-free strategy to efficiently induce apoptosis in tumor cells. However, the limited content of intracellular hydrogen peroxide (H2O2) extremely restricts the performance of POD-like nanozymes to amplify cellular oxidative stress. Moreover, additional operational processes combined with exogenous reagents to achieve oxidative stress lead to a dilemma of extra cytotoxicity. Here, an integrated iron-porphyrin-MOF-based nanozyme composite named HA@GOx@PCN-224(Fe) (HGPF) was precisely designed and constructed. Generally, the POD-like nanozyme PCN-224(Fe) was used as a platform to immobilize glucose oxidase (GOx), and further embedded with hyaluronic acid (HA) to enable the targeting ability of tumor cells. When endocytosed by tumor cells, intracellular glucose was oxidized to H2O2 and gluconic acid catalyzed by immobilized GOx of HGPF. Afterwards, inspired by heme analogs, H2O2 was catalyzed by iron-porphyrin active sites of the HGPF nanozyme to generate hydroxyl radicals (˙OH). Under light irradiation, the iron-porphyrin of HGPF acted as a photosensitizer to facilely produce singlet oxygen (1O2). Such a synergistic generation of ROS strikingly amplified oxidative stress and induced severe apoptosis in tumor cells. HGPF was expected to integrate intracellular oxygen sources and overcome the dilemma of limited intracellular H2O2 content. Consequently, HGPF was constructed as an integrated nanoreactor to simultaneously achieve light-enhanced catalytic oxidation cascades, providing a promising strategy for a synergistic amplification of cellular oxidative stress. [ABSTRACT FROM AUTHOR]

An "AND" logic gate-based NIR fluorescent probe Si-NH2-Glu was developed based on novel meso-amine Si-Rhodamine, which combined γ-glutamyl transpeptidase and pH dual-responsive sites. The features of Si-NH2-Glu enable it to be applied in orthotopic tumor imaging and fluorescence-guided surgery. [ABSTRACT FROM AUTHOR]

Novel purine-based iridium complexes were designed for selective determination of ER viscosity. The Ir-PH possessed excellent ER targeting ability and could distinguish the viscosity changes under ER stress by fluorescence lifetime image microscopy (FLIM), which may accelerate the development of relative quantitative detection of microenvironment changes at the subcellular level. [ABSTRACT FROM AUTHOR]

It is still a challenge to develop new intelligent multifunctional fluorescence reagents with high brightness, high optical stability, and high contrast fluorescence based on small molecules. In this study, by building push–pull electronic structures and adjusting the number of carbazole groups and the length of the alkyl chain, a series of multifunctional molecules based on a purine-core has been successfully synthesized and achieved the improvement of the fluorescence quantum yield. Furthermore, the relationship between the structure and optical properties of these purine derivatives has been investigated from multiple perspectives. Moreover, the most promising molecule (CPPC) exhibits high fluorescence quantum yield, high brightness, high optical stability, and high contrast fluorescence, and it has been successfully applied in information encryption, anti-counterfeiting and LD-tracking of living cells. The present study offers a novel and efficient approach to develop multifunctional fluorescence materials with high performance based on purine. [ABSTRACT FROM AUTHOR]

We developed a fusion glass disc technique using small-size samples (30 mg) for assaying precious siliceous samples of geochemical reference materials using wavelength-dispersive X-ray fluorescence determination of major (SiO2, TiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O, and P2O5) and minor (Ni, Sr, and Zr) elements. The normal-size glass discs (approximately 30 mm in diameter) were prepared using an automatic fluxer, combined with manual preparation, with a flux to sample ratio of 100 : 1. GSR-1 and GSR-3 were selected to evaluate the results obtained using XRF, ICP-OES (fusion), and ICP-OES (acid attack) and to assess the accuracy and precision of the three methods based on Whitty-Léveillé and coworkers' protocol. In the present work, a set of 46 rock certified reference materials (CRMs) was used to calibrate the spectrometer and another set of 16 CRMs was analyzed further to validate the accuracy and precision of the procedure. The homogeneity of the discs was evaluated using the μ-XRF mapping image technique. In general, we obtained good agreement with the recommended values for most determinations. Finally, we summarized the small-size sample methods published in recent years and compared the advantages and disadvantages of these methods in detail. [ABSTRACT FROM AUTHOR]

Inspired by the natural properties of the phospholipid bilayer (PB), three probes that could assemble with phospholipid bilayer through hydrophobic and electrostatic interactions are reported for rapid and accurate specific imaging of plasma membrane in 2D and 3D cell models. What's more, we have captured the picture of probe assembly with the phospholipid bilayer in cells for the first time. [ABSTRACT FROM AUTHOR]

Cationic polymers have shown great potential in the delivery of nucleic acids and proteins. In this study, a series of pyrimidine-based cationic polymers were synthesized via the Michael addition reaction from pyrimidine-based linkages and low molecular weight polyethyleneimine (PEI). The structure–activity relationship (SAR) of these materials in DNA and protein delivery was investigated. These materials could condense both DNA and protein into nanoparticles with proper sizes and zeta-potentials. In vitro experiments indicated that such polymers were efficient in transporting DNA and proteins into cells. Furthermore, the bioactivity of the genes and proteins encapsulated in these polymers were maintained during the delivery processes. Among the polymers, U-PEI600 synthesized from a uracil-containing linker and PEI 600 Da mediated comparable gene expression to PEI 25 kDa. Moreover, the activities of β-galactosidase delivered by U-PEI600 were well maintained after entering the cells. Evaluation using an immune response assay showed that the U-PEI600/OVA polyplex could stimulate greater production of immune factors with low cytotoxicity. Our study provides a strategy for the construction of cationic polymeric gene and cytosolic protein vectors with high efficiency and low toxicity. [ABSTRACT FROM AUTHOR]

The efficient delivery of therapeutic genes remains a major challenge in realizing a feasible gene-based treatment. Herein, a versatile oligopeptide, glutathione, was introduced to construct novel non-viral cationic gene vectors. Reduced/oxidized forms of glutathione (GSH/GSSG) and relevant amino acids (Glu, Cys, and Gly) were used to modify low molecular weight PEI through surface modification or crosslinking. These polymers could bind well and condense DNA into spherical nanoparticles, which were stable in the presence of serum. The disulfide bonds within the crosslinked polymer GSSG-PEI may facilitate polymer degradation and DNA release under a reductive environment. In vitro transfection experiments reveal that the modification could largely improve the gene transfection efficiency of low molecular weight PEI, especially in the presence of serum. In HeLa cells, GSSG-PEI could even give up to 150 times higher efficiency than PEI 25 kDa. TEM and serum concentration effect assay also demonstrate the good serum tolerance of the polymers. Flow cytometry results show that GSSG-PEI might induce cellular uptake with higher efficiency than PEI 25 kDa, especially in the presence of serum. Results reveal that GSSG is a good candidate for the crosslinking of small cationic molecules to form polymeric gene vectors with improved transfection efficiency and biocompatibility. [ABSTRACT FROM AUTHOR]

The chemically selective detection of natural nucleobase modifications has been regarded as the key step in understanding their important roles in epigenetics. Herein, for the first time, we introduce a Wittig reaction into the design of reaction-based fluorescent probes for ratiometrically detecting 5fU, selectively labelling 5fU-modified DNA and imaging intracellular 5fU produced by γ-irradiation. [ABSTRACT FROM AUTHOR]

A series of amphiphilic graft copolymers, poly(N-propargyldiethanolamine 4,4′-dithiodibutyionate)-graft-monomethoxy poly(ethylene glycol) (PPD-g-mPEG), were designed via a chemoenzymatic method for pH and reduced glutathione (GSH) dual-responsive drug delivery. The effects of percent grafting and molecular weights of mPEG on critical micelle concentration (CMC) values, size of micelles, drug loading and dual-response were tested. The graft copolymers could easily form homogeneous spherical micelles with appropriate sizes and zeta-potentials. The micelles of PPD-g-mPEG copolymers loaded doxorubicin (DOX) in high efficiency, and showed excellent stability under physiological conditions and synergetic dual-response to weakly acidic pH and GSH. In vitro experiments confirmed that the DOX-loaded micelles could be internalized into cancer cells efficiently and release DOX over time. Furthermore, cell cytotoxicity assays indicated that the graft copolymers were non-cytotoxic to both cancerous and normal cells while the DOX-loaded micelles greatly improved the selectivity ratios between HeLa cells and HL-7702 cells. DOX-loaded micelles also avoided hemolysis of red blood cells (RBCs) effectively compared with commercialized doxorubicin hydrochloride. All these demonstrated the potential of PPD-g-mPEG as a model to create more functional dual-responsive nanocarriers for controlled drug delivery. [ABSTRACT FROM AUTHOR]

Biothiols and SO2 play crucial roles in many physiological and pathological processes. To unravel their complicated interrelationship and cellular cross-talk, it would be highly desirable to develop single-molecule fluorescent probes that can selectively detect biothiols and SO2via different emission channels. Here, a novel chromenylium derivative, BPO-Py-diNO2, based on the rational design of dual recognition sites for biothiols and SO2 selectively and sensitively responded to biothiols with near-infrared fluorescence, and to SO2 with green fluorescence. The emission shift for the two channels was 170 nm. BPO-Py-diNO2 was selectively enriched in lysosomes. It could also be used to evaluate dual-channel imaging of endogenous biothiols and SO2 in living HeLa cells, and it could be used for monitoring the mutual interconversion of biothiols and SO2. [ABSTRACT FROM AUTHOR]

A novel reaction-based fluorescent probe (ATC-Hg) was designed and synthesized via the “covalent assembly” principle, which exhibited excellent selectivity and high sensitivity for Hg2+ and CH3Hg+. Moreover, it is the first Hg(ii) sensitive fluorescent probe that has been successfully applied in imaging in both cells and Escherichia coli. [ABSTRACT FROM AUTHOR]

In the past few decades, although various reduction-responsive nanocarriers have been designed and explored for gene delivery, it is difficult to directly detect or monitor the reduction capability of these carriers, especially under intracellular conditions. Taking advantage of the generated fluorescence signal in the reduction process of the naphthalimide-sulfonamide (NS) group, we developed a novel liposomal nanocarrier, FNSL, which showed reduction-sensitive property and self-reporting character. As a new reduction-responsive site in a gene delivery system, the NS group in FNSL is capable of responding to glutathione (GSH) and simultaneously emitting green fluorescence at 500 nm in both extra- and intracellular circumstances. Hence, it will be very convenient to assess the reducibility of this carrier and monitor the stimuli-responsive gene release via fluorescence signal. FNSL has high affinity for DNA and can condense it into nanoparticles with a proper nano-size and zeta potential. Compared with the non-reducible FNAL, FNSL showed enhanced gene release capability, higher transfection efficiency (TE), and lower cytotoxicity. Furthermore, treatment of FNSL-mediated transfection with slightly exogenous GSH greatly improved the TE of FNSL in HepG2 cells, and its TE was even higher than that of Lipofectamine 2000. These results demonstrate that FNSL possesses great potential for efficient and low-toxicity gene delivery, and this study on a bioreducible liposome with self-reporting ability would be a guide for further research on the development of biodegradable gene carriers. [ABSTRACT FROM AUTHOR]

A new strategy for the construction of fluorinated cationic polymers for gene delivery was introduced. The fluorinated polymers were synthesized by crosslinking low molecular weight PEI with diols containing various lengths of perfluoroalkyl chains via epoxide ring-opening polymerization. Such a study presents the first example of polymeric gene vectors with fluorination on the polymer backbone but not on the side chains. These materials showed good DNA condensation and protection ability and could condense DNA into nanoparticles with appropriate sizes and zeta-potentials. The fluorine atoms might strengthen the interaction toward DNA, leading to more stable polyplexes. In vitro transfection results showed that the fluorinated polymers could mediate efficient gene delivery toward both 2D and 3D cell cultures at low weight ratios, and their transfection efficiency was higher than that of PEI 25 kDa and their non-fluorinated counterparts. Several assays including DLS, TEM, luciferase reporter gene transfection and flow cytometry revealed that fluorination improved the serum resistance of these polymeric vectors, and more fluorine atoms might lead to better serum tolerance. These fluorinated materials exhibited very low cytotoxicity at transfection dosage. A cellular uptake study with uptake inhibitors indicated that macro-pinocytosis and microtubule-mediated endocytosis were the major endocytosis pathways for these polyplexes. [ABSTRACT FROM AUTHOR]

Typical aggregation-induced emission enhancement fluorogens (AIEEgens) generally are designed as propeller-shaped molecules with multiple aromatic rotors. Described herein are 1,4-dihydropyridines, which have the minimum size necessary for AIEE, containing only a single ring, synthesized through a facile biocatalysis procedure. Owing to the AIEE property, intramolecular motion can be restrained by the surrounding environment, causing the radiative channel to open up. Both the fluorescence intensities and the lifetimes of the 1,4-dihydropyridine representatives increased with increasing viscosity, and high sensitivities were observed. On the basis of the single crystal X-ray structures, density functional theory (DFT) calculations were performed to explain the mechanism of the single-ring AIEE behaviour. Moreover, a few of the neutral AIEEgens were found to possess a high specificity towards mitochondria. As an example, one of the AIEEgens exhibited superior photostability and excellent storage tolerance, allowing for real-time imaging, viscosity mapping, and long-term tracking of the dynamics of the mitochondrial morphology. [ABSTRACT FROM AUTHOR]

Compared to traditional cationic lipids, bola-type lipids have received much less attention despite their advantages including the ability to form more stable and regular-shaped liposomes. In this report, a series of novel symmetric cationic bolalipids based on lysine or cyclen headgroups were designed and synthesized. Structure–activity relationships including the effect of the hydrophobic chain length and cationic headgroup on liposome formation, DNA binding, the physical property of bolasomes, and gene transfection were systematically studied. Results reveal that an appropriate hydrophobic chain length is essential to form nano-sized bolasomes with good DNA binding and condensation ability. MTS-based cell viability assays showed low cytotoxicity of these bolasome/DNA complexes. Lys-14-10, which has a 36-atom-length hydrophobic chain, exhibited the best transfection efficiency in the two cell lines. Flow cytometry and confocal laser microscopy assays reveal that the bolaplexes formed from bolalipids with such a chain might induce the highest cellular uptake. For the cationic headgroup, lysine is more suitable than cyclen for such a bola-type vector. Although the TEs of these bolalipids are still lower than commercially used non-bola lipid lipofectamine 2000, this study may give us some clues for the design of novel bolalipids with higher TE and biocompatibility. [ABSTRACT FROM AUTHOR]

A near-infrared ratiometric fluorophore (NIR-HBT) was rationally designed and constructed by expanding both the excitation and emission wavelength of the classical ratiometric fluorophore 2-(benzothiazol-2-yl)phenol (HBT) into the near-infrared region. The NIR-HBT was easily synthesized by incorporating the HBT module into the hemicyanine skeleton and showed evident NIR ratiometric fluorophore characteristics. Further application of the new fluorophore for pH detection demonstrated that NIR-HBT possesses superior overall analytical performance and NIR-HBT was successfully applied for detection of acidosis caused by inflammation in living animal tissue, which indicated the potential application value of NIR-HBT in biological imaging and sensing. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe for SO2 derivatives based on the conjugate of carbazole and indolium was presented, which could selectively respond to HSO3− over other thiol compounds. More importantly, CZ-Id is a novel mitochondria-targeted ratiometric fluorescent probe to image exogenous SO2 derivatives. [ABSTRACT FROM AUTHOR]

A ratiometric fluorescent probe (RMClO-2) for ClO− based on the conjugate of coumarin–rhodamine was presented, which could sense ClO− with fast response (within 5 s), high sensitivity and excellent selectivity. More importantly, RMClO-2 is the first mitochondria-targeted ratiometric fluorescent probe to image exogenous and endogenous ClO−. [ABSTRACT FROM AUTHOR]

A series of cationic polymers (P1–P5) were designed and synthesized using a ring-opening polymerization strategy based on low molecular weight polyethyleneimine (PEI) and using diglycidyl ethers as the bridging moiety. Although these polymers have reduced amino group density relative to 25 kDa PEI, their pH buffering capacity and deoxyribonucleic acid (DNA) binding ability were seldom affected. They were able to condense plasmid DNA (pDNA) well to form nanoparticles of suitable sizes (150–300 nm) and positive zeta potentials (+25–40 mV). Cell Counting Kit-8 (CCK-8) assays revealed that polyplexes formed from these polymers have lower cytotoxicity than those derived from PEI. Luciferase reporter gene delivery experiments indicated that these polymers have much better transfection efficiency than 25 kDa PEI, especially P2 and P5. Unlike PEI, serum has little negative effect on the transfection by these materials, and their transfection efficiencies were seldom reduced even with high concentrations of serum. Under optimized conditions, up to 400 times higher transfection efficiency than with PEI could be achieved. Several assays including gel electrophoresis, dynamic light scattering and transmission electron microscopy also confirmed the good serum tolerance of these polyplexes. The evenly distributed hydroxyl groups formed by the ring-opening polymerization are considered to contribute much to their high serum tolerance, and such polymerization might be a promising strategy for the design of efficient non-viral gene delivery vectors. [ABSTRACT FROM AUTHOR]

Biothiols and SO 2 play crucial roles in many physiological and pathological processes. To unravel their complicated interrelationship and cellular cross-talk, it would be highly desirable to develop single-molecule fluorescent probes that can selectively detect biothiols and SO 2 via different emission channels. Here, a novel chromenylium derivative, BPO-Py-diNO 2 , based on the rational design of dual recognition sites for biothiols and SO 2 selectively and sensitively responded to biothiols with near-infrared fluorescence, and to SO 2 with green fluorescence. The emission shift for the two channels was 170 nm. BPO-Py-diNO 2 was selectively enriched in lysosomes. It could also be used to evaluate dual-channel imaging of endogenous biothiols and SO 2 in living HeLa cells, and it could be used for monitoring the mutual interconversion of biothiols and SO 2 .

Synthetic polycations show great potential for the construction of ideal non-viral gene delivery systems. Several cationic polymers were synthesized by the epoxide ring-opening polymerization between diepoxide and various polyamines. Disulfide bonds were introduced to afford the polymers bio-reducibility, while the oxygen-rich structure might enhance the serum tolerance and biocompatibility. The polycations have much lower molecular weights than PEI 25 kDa, but still could well bind and condense DNA into nano-sized particles. DNA could be released from the polyplexes by addition of reductive DTT. Compared to PEI, the polycations have less cytotoxicity possibly due to their lower molecular weights and oxygen-rich structure. More significantly, these materials exhibit excellent serum tolerance than PEI, and up to 6 times higher transfection efficiency than PEI could be obtained in the presence of serum. The transfection mediated by was seldom affected even at a high concentration of serum. Much lower protein adsorption of polycations than PEI was proved by bovine serum albumin adsorption experiments. Flow cytometry also demonstrates their good serum resistance ability.

A ratiometric fluorescent probe for SO2 derivatives based on the conjugate of carbazole and indolium was presented, which could selectively respond to HSO3(-) over other thiol compounds. More importantly, CZ-Id is a novel mitochondria-targeted ratiometric fluorescent probe to image exogenous SO2 derivatives.

The terpyridine anthracene ligand was synthesized and characterized. is a ratiometric fluorescent probe for Cd(2+) with a recognition mechanism based on intramolecular charge transfer (ICT). An complex was isolated, and its structure was established using single-crystal XRD. The complex was able to serve as a novel reversible chemosensing ensemble to allow ratiometric response to pyrophosphate (PPi) in aqueous media. Moreover, the fluorescence imaging in living cells from these two emission channels suggested that was a ratiometric probe for Cd(2+), and the in situ generated complex was also a ratiometric ensemble for PPi detection in living cells.

A series of novel cationic lipids based on 1,4,7,10-tetrazacyclododecane (cyclen) with the imidazole group as the pH-sensitive moiety and various aliphatic long chains were designed and synthesized. Cationic liposomes were prepared by mixing the lipids and the helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in an appropriate molar ratio. The liposomes showed good stability and could condense plasmid DNA into nanosized particles (∼100 to ∼250 nm) with a positive zeta-potential (+10-25 mV). CCK-8-based cell viability assays showed a relatively lower cytotoxicity of the lipoplexes compared to commercially available lipofectamine 2000. Both enhanced green fluorescent protein and luciferase assays were carried out to investigate the in vitro transfection efficiency (TE) of the lipoplexes. Results showed that both the structures of the hydrophobic chain and the linking bond significantly affected the TE, and the linoleyl-containing lipoplex gave the best TE, which is comparable to lipofectamine 2000. The imidazole group was demonstrated to play an important role in the transfection, and the imidazole-absent analog gave dramatically lower TE. Furthermore, it was also found that Ca(2+) could largely enhance the TE of these lipids, and the optimized TE was about 5 times higher than lipofectamine 2000. Flow cytometry demonstrates that the enhancement of TE by Ca(2+) was caused by the improvement of cellular uptake. These results suggest that the cyclen-imidazole containing lipids might be promising non-viral gene delivery vectors.