Jinlu Tang

Concatemeric dsDNA-templated copper nanoparticles strategy with improved sensitivity and stability based on rolling circle replication and its application in microRNA detection.

DNA-templated copper nanoparticles (CuNPs) have emerged as promising fluorescent probes for biochemical assays, but the reported monomeric CuNPs remain problematic because of weak fluorescence and poor stability. To solve this problem, a novel concatemeric dsDNA-templated CuNPs (dsDNA-CuNPs) strategy was proposed by introducing the rolling circle replication (RCR) technique into CuNPs synthesis. In this strategy, a short oligonucleotide primer could trigger RCR and be further converted to a long concatemeric dsDNA scaffold through hybridization. After the addition of copper ions and ascorbate, concatemeric dsDNA-CuNPs could effectively form and emit intense fluorescence in the range of 500-650 nm under a 340 nm excitation. In comparison with monomeric dsDNA-CuNPs, the sensitivity of concatemeric dsDNA-CuNPs was greatly improved with ~10,000 folds amplification. And their fluorescence signal was detected to reserve ~60% at 2.5 h after formation, revealing ~2 times enhanced stability. On the basis of these advantages, microRNA let-7d was selected as the model target to testify this strategy as a versatile assay platform. By directly using let-7d as the primer in RCR, the simple, low-cost, and selective microRNA detection was successfully achieved with a good linearity between 10 and 400 pM and a detection limit of 10 pM. The concatemeric dsDNA-CuNPs strategy might be widely adapted to various analytes that can directly or indirectly induce RCR.

Iodide-Responsive Cu–Au Nanoparticle-Based Colorimetric Platform for Ultrasensitive Detection of Target Cancer Cells

Colorimetric analysis is promising in developing facile, fast, and point-of-care cancer diagnosis techniques, but the existing colorimetric cancer cell assays remain problematic because of dissatisfactory sensitivity as well as complex probe design or synthesis. To solve the problem, we here present a novel colorimetric analytical strategy based on iodide-responsive Cu-Au nanoparticles (Cu-Au NPs) combined with the iodide-catalyzed H2O2-TMB (3,3,5,5-tetramethylbenzidine) reaction system. In this strategy, bimetallic Cu-Au NPs prepared with an irregular shape and a diameter of ∼15 nm could chemically absorb iodide, thus indirectly inducing colorimetric signal variation of the H2O2-TMB system. By further utilizing its property of easy biomolecule modification, a versatile colorimetric platform was constructed for detection of any target that could cause the change of Cu-Au NPs concentration via molecular recognition. As proof of concept, an analysis of human leukemia CCRF-CEM cells was performed using aptamer Sgc8c-modified Cu-Au NPs as the colorimetric probe. Results showed that Sgc8c-modified Cu-Au NPs successfully achieved a simple, label-free, cost-effective, visualized, selective, and ultrasensitive detection of cancer cells with a linear range from 50 to 500 cells/mL and a detection limit of 5 cells in 100 μL of binding buffer. Moreover, feasibility was demonstrated for cancer cell analysis in diluted serum samples. The iodide-responsive Cu-Au NP-based colorimetric strategy might not only afford a new design pattern for developing cancer cell assays but also greatly extend the application of the iodide-catalyzed colorimetric system.

Combining physical embedding and covalent bonding for stable encapsulation of quantum dots into agarose hydrogels

A strategy of combining physical embedding and covalent crosslinking was developed to encapsulate cysteamine-capped quantum dots (QDs) into agarose hydrogel microbeads (AHM). Cysteamine-capped QDs were encapsulated into the pores of agarose hydrogel microbeads by virtue of hydrogen bonding between the amino groups of cysteamine and hydroxyl groups of agarose, resulting in more than 6.0 × 107 QDs per microbead. Polyethylenimine (PEI) and oxalaldehyde were then introduced to form a covalently crosslinked network to further stabilize the encapsulation. The resulting hybrid hydrogel microbeads exhibited high doping capacity and negligible QDs leakage, and enabled optical multicolor barcoding.

Synthesis of Hollow Mesoporous Silica Nanorods with Controllable Aspect Ratios for Intracellular Triggered Drug Release in Cancer Cells

Here, we have reported a straightforward and effective synthetic strategy for synthesis of aspect-ratios-controllable mesoporous silica nanorods with hollow structure (hMSR) and its application for transcription factor (TF)-responsive drug delivery intracellular. Templating by an acid-degradable nickel hydrazine nanorods (NHNT), we have first synthesized the hollow dense silica nanorods and then coated on a mesoporous silica layer. Subsequently, the dense silica layer was removed by the surface-protected etching method and the hollow structure of hMSR was finally formed. The aspect ratios of the hMSR can be conveniently controlled by regulating the aspect ratios of NHNT. Four different hMSR with aspect ratios of ca. 2.5, ca. 5.3, ca. 8.1, and ca. 9.0 has been obtained. It was demonstrated that the as-prepared hMSRs have good stability, high drug loading capacity, and fast cell uptake capability, which makes them to a potential nanocarrier for drug delivery. As the paradigm, hMSR with an aspect ratio of ca. 8.1 was then applied for TF-responsive intracellular anticancer drug controlled release by using a Ag(+)-stabilized molecular switch of triplex DNA (TDNA) as capping agents and probes for TFs recognition. In the presence of TF, the pores of hMSR can be unlocked by the TFs induced disassembly of TDNA, leading to the leakage of DOX. The research in vitro displayed that this system has a TFs-triggered DOX release, and the cytotoxicity in L02 normal cells was lower than that of HeLa cells. We hope that this developed hMSR-based system will promote the development of cancer therapy in related fields.

Noncovalent assembly of reduced graphene oxide and alkyl-grafted mesoporous silica: an effective drug carrier for near-infrared light-responsive controlled drug release

In this paper, we report the assembly of reduced graphene oxide (RGO) and mesoporous silica grafted with alkyl chains (MSN-C18) to develop a new class of drug carriers which are able to deliver the loaded drug molecules into living cells upon exposure to near-infrared (NIR) light. This novel drug carrier consists of a structure formed by the noncovalent interaction of RGO caps and alkyl chains on the surface of MSN-C18. The capping of RGO sheets on mesoporous silica effectively blocks the pore mouths in the absence of NIR light. Conversely, and very importantly, the photothermal heating effect of RGO leads to a rapid increase in the local temperature upon exposure to NIR light, resulting in the weakening of the RGO sheet/alkyl chain noncovalent interaction. The RGO sheets will then be removed from the MSN surface, and the pores are uncapped. This uncapping mechanism makes it possible to release the loaded drug molecules upon irradiation with NIR light. In the present study, such a noncovalent assembly was examined by the use of doxorubicin as a model drug for NIR light-responsive intracellular controlled release studies. We believe that this noncovalent assembly will prove to be a promising drug delivery system for cancer therapy in the near future.

Aptamer-based FRET nanoflares for imaging potassium ions in living cells

Due to the effective properties of the FRET signal and K+-sensitive recognition of G-quadruplex, aptamer-based FRET nanoflares were developed to sense intracellular potassium ions.

A metal–organic framework based nanocomposite with co-encapsulation of Pd@Au nanoparticles and doxorubicin for pH- and NIR-triggered synergistic chemo-photothermal treatment of cancer cells

Here, we report a novel metal-organic framework-based nanocomposite with encapsulated Pd@Au nanoparticles and doxorubicin (DOX) for pH- and NIR-triggered synergistic chemo-photothermal treatment of cancer cells. In this work, Pd nanoparticles, which have uniform size and dispersibility, were first synthesized and used as a template to direct the covering of Au nanosheets. The obtained Au coated Pd (Pd@Au) nanoparticles have excellent dispersibility and photothermal conversion ability, which makes them a good photothermal nanomaterial. Subsequently, an acid-degradable metal-organic framework of ZIF-8 was employed to synchronously encapsulate Pd@Au nanoparticles and DOX to get a metal-organic framework-based nanocomposite (DOX/Pd@Au@ZIF-8). Under acid conditions (e.g. pH ∼5.0 in a lysosome), the ZIF-8 framework of the DOX/Pd@Au@ZIF-8 nanocomposite could be degraded, resulting in the release of encapsulated DOX. Moreover, the present Pd@Au nanoparticles can effectively convert NIR laser light (780 nm, 2.1 W cm-2) into heat, not only further promoting the release of DOX, but also realizing the synergistic chemo-photothermal treatment of cancer cells. The in vitro experiments showed that this nanocomposite system has an excellent synergistic treatment effect on SMMC-7721 cells, even at low concentrations (e.g. 20 μg mL-1). With the properties of synergistic chemo-photothermal treatment, we hope that such a nanocomposite system of DOX/Pd@Au@ZIF-8 could open the door to designing a significant multifunctional system for diverse applications in cancer treatment.

Polyvalent and Thermosensitive DNA Nanoensembles for Cancer Cell Detection and Manipulation

Development of smart DNA nanostructures is of great value in cancer studies. Here, by integrating rolling circle amplification (RCA) into split aptamer design, a novel strategy of polyvalent and thermosensitive DNA nanoensembles was first proposed for cancer cell detection and manipulation. In this strategy, a long nanosolo ssDNA with repeated Split-b and Poly T regions was generated through RCA. Split-b supplied polyvalent binding sites while Poly T supported signal output by hybridizing with fluorophore-labeled poly A. After addition of Split-a, nanoensembles formed on the cell surface due to target-induced assembly of Split-a/Split-b from the free state to the recognition structure, and on the basis of the thermosensitivity of split aptamer, nanoensembles were controlled reversibly by changing temperatures. As proof of concept, split ZY11 against SMMC-7721 cancer was used to construct nanoensembles. Compared with monovalent split aptamer, nanoensembles were demonstrated to have a much stronger interaction with target cells, thus realizing an ∼2.8-time increase in signal-to-background ratio (SBR). Moreover, nanoensembles extended the tolerance range of target binding from 4 °C to room temperature and speeded recognition thus achieving almost 50% binding in 1 min. Then, nanoensembles were successfully applied to detect 7721 cells in serum and mixed cell samples. By utilizing microplate well surface as the model, temperature-controlled catch/release of target cells was also realized with nanoensembles, even under unfriendly conditions for monovalent split aptamer. The RCA-mediated aptameric nanoensembles strategy not only solved the problem of split aptamer in inefficient binding but also paved a brand new way for developing polyvalent and intelligent nanomaterials.

Synthesis of a core/satellite-like multifunctional nanocarrier for pH- and NIR-triggered intracellular chemothermal therapy and tumor imaging

Here, we have reported a core/satellite-like multifunctional nanocarrier for pH- and NIR-triggered synergistic chemothermal therapy and tumor imaging. In this system, upconversion nanoparticles (UCNPs), which have an average diameter of 23 nm, were first synthesized by a classic high-temperature solvent method and subsequently used as the imaging cores to direct the coating of mesoporous silica shells. The obtained mesoporous silica coated core–shell nanoparticles (UCNP@mSiO2) have a uniform pore size (4.2 nm) and excellent DOX loading ability (85.3 μmol g−1 SiO2), which makes UCNP@mSiO2 a good carrier. In order to finally obtain this core/satellite-like system (DOX@UCNP@mSiO2–AuNRs), gold nanorods (AuNRs) with a positive charge of 15 mV were subsequently capped on the negatively charged DOX loaded UCNP@mSiO2 (−30 mV) via electrostatic interactions. Under low-pH conditions (e.g. pH 4.9), the charge of mesoporous silica changed to −10.8 mV, leading to the separation of AuNRs and the release of entrapped DOX. Moreover, the present AuNRs can effectively convert NIR light (780 nm) into heat, and the increased temperature is as high as 20 °C under the laser power density of 2.0 W cm−2. This study showed that this system has excellent imaging ability and synergistic chemothermal therapy effect. A versatile synergistic therapy system such as DOX@UCNP@mSiO2–AuNRs is expected to have wide biomedical applications and may be particularly useful for synergistic tumor therapy.

DNA nanotriangle-scaffolded activatable aptamer probe with ultralow background and robust stability for cancer theranostics

Activatable aptamers have emerged as promising molecular tools for cancer theranostics, but reported monovalent activatable aptamer probes remain problematic due to their unsatisfactory affinity and poor stability. To address this problem, we designed a novel theranostic strategy of DNA nanotriangle-scaffolded multivalent split activatable aptamer probe (NTri-SAAP), which combines advantages of programmable self-assembly, multivalent effect and target-activatable architecture. Methods: NTri-SAAP was assembled by conjugating multiple split activatable aptamer probes (SAAPs) on a planar DNA nanotriangle scaffold (NTri). Leukemia CCRF-CEM cell line was used as the model to investigate its detection, imaging and therapeutic effect both in vitro and in vivo. Binding affinity and stability were evaluated using flow cytometry and nuclease resistance assays. Results: In the free state, NTri-SAAP was stable with quenched signals and loaded doxorubicin, while upon binding to target cells, it underwent a conformation change with fluorescence activation and drug release after internalization. Compared to monovalent SAAP, NTri-SAAP displayed greatly-improved target binding affinity, ultralow nonspecific background and robust stability in harsh conditions, thus affording contrast-enhanced tumor imaging within an extended time window of 8 h. Additionally, NTri-SAAP increased doxorubicin loading capacity by ~5 times, which further realized a high anti-tumor efficacy in vivo with 81.95% inhibition but no obvious body weight loss. Conclusion: These results strongly suggest that the biocompatible NTri-SAAP strategy would provide a promising platform for precise and high-quality theranostics.