Jia Wen

Facile synthesis of a nanocomposite based on graphene and ZnAl layered double hydroxides as a portable shelf of a luminescent sensor for DNA detection

Recently, nanocomposites based on graphene and layered double hydroxides (LDH) have been developed and used in many fields. However, to the best of our knowledge, there is no report on the luminescence sensor applications of graphene/LDH composites. Herein, a hybrid graphene–ZnAl-LDH nanocomposite has been developed using a facile one-step process and the presence of LDH in the composite can effectively prevent the restacking of graphene and improve both its luminescence properties and thermal stability. Furthermore, the composite can be used as a portable shelf of the Ru(phen)3Cl2 (tris(1,10-phenanthroline)ruthenium(II) dichloride) sensor to selectively discriminate DNA. It was found that the graphene–ZnAl-LDH composite can effectively quench the emission of the Ru(phen)3Cl2 sensor. After the addition of a certain amount of DNA into the system, Ru(phen)3Cl2 was released from the graphene–ZnAl-LDH composite and it interacted with DNA immediately, leading to the luminescence recovery of the sensor. The results indicate that the RGO–ZnAl-LDH composite displayed an excellent luminescence response and good linear correlation to DNA. Therefore, the composite can be employed as a portable shelf of Ru(phen)3Cl2 to discriminate DNA. Moreover, both the shelf and the sensor can be easily collected and made ready for the next sample if there is no DNA in the solution. The proposed method was further applied to detect the immunodeficiency virus gene (HIV), thus providing a new field of application for hybrid graphene/LDH composites.

Construction of A Triple-Stimuli-Responsive System Based on Cerium Oxide Coated Mesoporous Silica Nanoparticles

In this work, a triple-stimuli (GSH, pH and light irradiation) responsive system were designed based on CeO2 nanoparticles (CeO2 NPs) coated doxorubicin (DOX) and photosensitizer hematoporphyrin (HP) dual-loaded mesoporous silica nanoparticles (MSN). Upon entering into cancer cells, both high concentration of intracellular GSH and low pH environment would reduce CeO2 NPs to cerium ions, accompanied with the degradation of CeO2 NPs and the conformational change of HP under light irradiation, the preloaded DOX are thus released from the nanocarrier, resulting in a contrast fluorescence enhancement. Meanwhile, 1O2 generated from HP for potential photodynamic therapy (PDT) upon light irradiation. In comparison, not much influence can be observed for normal cells. This nanosystem not only has a significantly enhanced efficacy for cancer cells but also broad the scope for the future design and applications of multifunctional platforms for synergetic chemotherapy and PDT.

A water-soluble nucleolin aptamer-paclitaxel conjugate for tumor-specific targeting in ovarian cancer

Paclitaxel (PTX) is among the most commonly used first-line drugs for cancer chemotherapy. However, its poor water solubility and indiscriminate distribution in normal tissues remain clinical challenges. Here we design and synthesize a highly water-soluble nucleolin aptamer-paclitaxel conjugate (NucA-PTX) that selectively delivers PTX to the tumor site. By connecting a tumor-targeting nucleolin aptamer (NucA) to the active hydroxyl group at 2′ position of PTX via a cathepsin B sensitive dipeptide bond, NucA-PTX remains stable and inactive in the circulation. NucA facilitates the uptake of the conjugated PTX specifically in tumor cells. Once inside cells, the dipeptide bond linker of NucA-PTX is cleaved by cathepsin B and then the conjugated PTX is released for action. The NucA modification assists the selective accumulation of the conjugated PTX in ovarian tumor tissue rather than normal tissues, and subsequently resulting in notably improved antitumor activity and reduced toxicity.Paclitaxel, a first line chemotherapeutic drug, suffers from poor water solubility and low tissue selectivity. Here, the authors report a water-soluble nucleolin aptamer-paclitaxel conjugate that selectively accumulates in ovarian tumor issues displaying reduced toxicity and improved activity profiles.

A simple photoluminescent strategy for pH and amine vapors detection based on Eu(III)-complex functionalized material

In this work, we report the development of easy-prepared, low cost and portable photoluminescent films for pH and amine vapors detection based on Eu(III)-complex functionalized materials: Eu(DBM)3Phen (LMOF-1), Eu(DBM)3BPY (LMOF-2), which were loaded on portable matrices (e.g. neutral silica plate and normal filter paper). The films not only displayed response over a pH range of 4–13 but also can be employed to sense volatile amines or acids vapors like ammonia, ethylenediamine, acetic acid and hydrochloric acid etc., which is significant for portable pH or acid–base vapors detection.

Mesoporous silica nanoparticles-assisted ruthenium(II) complexes for live cell staining

Ruthenium complexes which can bind to DNA via electrostatic and intercalation interactions producing strong luminescence have become ideal candidates for DNA staining. However, some of them such as Ru(phen)3Cl2 and Ru(phen)2(dppz)Cl2 could hardly cross the cellular membrane of live cells which limited their further interaction with DNA in live cells. To solve this problem, a potential approach is to find a proper vehicle for loading and delivery of these ruthenium complexes into live cells. Mesoporous silica nanoparticles (MSNs) with non-toxicity and good biocompatibility can be good candidates. More importantly, ruthenium complexes with positively charge could be loaded on negatively charged MSNs via electrostatic attractions to form MSNs-Ru hybrid. In vitro test demonstrated that MSNs had no side effects on the interactions between Ru complexes and DNA. Furthermore, it is found that the MSNs-Ru hybrid can enter into living human cervical cancer cells HeLa and stain the DNA while the corresponding ruthenium complexes alone could hardly cross the cellular membrane in the control experiment, demonstrating MSNs can be employed to be an efficient ruthenium complexes delivery nanomaterial for live cell staining.

Reduction degree and property study of graphene nanosheets prepared with different reducing agents and their applicability as a carrier of the Ru(phen)3Cl2 luminescent sensor for DNA detection

Recently, graphene nanosheets (GNS) have been widely investigated and used in capacitors, catalysts, biological/chemical sensors, etc. However, the feasible applications of GNS prepared with different reducing agents as a carrier of luminescent sensors have never been systematically studied yet. Herein, a series of GNS were acquired using different reducing agents, such as hydrazine, glucose and urea. The reduction degrees and properties of the GNS samples were systematically studied by using an X-ray diffractometer, Raman spectra, IR spectra and X-ray photoelectron spectroscopy. The results indicated that the reduction degree was in the order of hydrazine > glucose > urea, demonstrating that reducing agents play an important role in the bulk fabrication of high quality graphene. Then the GNS samples were all employed as a carrier of the Ru(phen)3Cl2 (tris(1,10-phenanthroline)ruthenium(II) dichloride) sensor to discriminate DNA. It is found that all the GNS samples can effectively quench the emission of the Ru(phen)3Cl2 sensor. After the addition of a certain amount of DNA into the corresponding systems, the luminescence intensity was fully recovered. In comparison, the luminescence response of GNS-G prepared with glucose shows the best linear correlation to the DNA added, with a detection limit of 3.62 × 10−9 g mL−1, indicating GNS-G can be employed as a good carrier of Ru(phen)3Cl2 to discriminate DNA. This work will significantly advance the research of bulk fabrication of high quality graphene and the specific applications in luminescent sensors of graphene-based functional materials in the future.

Hierarchical self-assembly of squaraine and silica nanoparticle functionalized with cationic coordination sites for near infrared detection of ATP

Optical activity of hierarchical supramolecular assemblies based on organic dyes would create multiple functional architectures. In this work, three kinds of silica nanoparticles with or without functional groups were synthesized. For the first time, silica nanoparticles can induce positively charged squaraine (SQ) to aggregate to form supramolecular assemblies. Adenosine-5′-triphosphate (ATP) as building blocks was absorbed on the surface of silica nanoparticles through metal-anion coordination and electrostatic interactions, in which the aggregates of SQ was transferred to monomer. The thickness being composed of ATP and SQ on the outside of nanoparticles is about 5 nm. These supramolecular assemblies showed selective turn-on fluorescence response to ATP in near infrared (NIR) region over other ions through metal-anion coordination and electrostatic interactions. These functional silica nanoparticles possessing many advantages provide proof-of-principle “seed crystals” for construction of supramolecular assemblies and platforms for sensing with facile performance.

A water-soluble near-infrared fluorescent probe for specific Pd2+ detection

Palladium (Pd) is widely used in chemistry, biology, environmental science etc., and Pd2+ is the most plenitudinous oxidation state of the Pd that can exist under physiological conditions or in living cells, which could have adverse effects on both our health and environment. Thus, it is of great significance to monitor the changes of Pd2+. Hence, a novel near-infrared fluorescent probe M-PD has been developed for selective detection of Pd2+ based on naphthofluorescein in this work. The result demonstrated that M-PD exhibited favorable properties for sensing Pd2+ such as excellent water solubility, high selectivity and sensitivity. And the limit of detection was estimated as 10.8 nM, much lower than the threshold in drugs (5-10 ppm) specified by European Directorate for the Quality Control of Medicines. More importantly, detection and recovery experiments of Pd2+ in aspirin aqoeous solution and soil are satisfactory. In addition, M-PD has also been successfully used for near-infrared fluorescence imaging of Pd2+ in living cells, indicating that the probe has better feasibility and application potential in the determination of Pd2+.

Double-mode detection of HClO by naked eye and concurrent fluorescence increasing in absolute PBS

A water soluble fluorescent probe WCN was successfully designed and synthesized based on acenaphthenequinone. It can be employed for double-mode detection of HClO by the naked eye and concurrent significant fluorescence increasing in absolute PBS. The detection limit was measured down to 77 pM. Especially important, WCN works well in both living cells and a living mouse.