One-step synthesis, self-assembly and bioimaging applications of adenosine triphosphate containing amphiphilies with aggregation-induced emission feature

Aggregation-induced emission-active micelles: synthesis, characterization, and applications

Aggregation-induced emission (AIE)-active micelles are a type of fluorescent functional materials that exhibit enhanced emissions in the aggregated surfactant state. They have received significant interest due to their excellent fluorescence efficiency in the aggregated state, remarkable processability, and solubility. AIE-active micelles can be designed through the self-assembly of amphipathic AIE luminogens (AIEgens) and the encapsulation of non-emissive amphipathic molecules in AIEgens. Currently, a wide range of AIE-active micelles have been constructed, with a significant increase in research interest in this area. A series of advanced techniques has been used to characterize AIE-active micelles, such as cryogenic-electron microscopy (Cryo-EM) and confocal laser scanning microscopy (CLSM). This review provides an overview of the synthesis, characterization, and applications of AIE-active micelles, especially their applications in cell and in vivo imaging, biological and organic compound sensors, anticancer drugs, gene delivery, chemotherapy, photodynamic therapy, and photocatalytic reactions, with a focus on the most recent developments. Based on the synergistic effect of micelles and AIE, it is anticipated that this review will guide the development of innovative and fascinating AIE-active micelle materials with exciting architectures and functions in the future.

Construction of Bio/Nanointerfaces: Stable Gold Nanoparticle Bioconjugates in Complex Systems

The real application of DNA-functionalized gold nanoparticles (DNA-Au NPs) was limited by decreased stability and irreversible aggregation in high-ionic strength solutions and complex systems. Therefore, exploring a kind of DNA-Au NPs with excellent stability in high-ionic strength solutions and complex systems is challenging and significant. Herein, a novel universal bioconjugate strategy for constructing ultrastable DNA-Au NPs was designed based on the combination of polydopamine (PDA) shell and DNA linker. The obtained DNA-linked Au@polydopamine nanoparticles (DNA-Au@PDA NPs) showed colloidal stability in high-ionic strength solution and complex systems (such as human serum and cell culture supernatant). Moreover, the nanoparticles still maintained good dispersion after multiple freeze-thaw cycles. The high stability of DNA-Au@PDA NPs may be attributed to increasing the electrostatic and steric repulsions among nanoparticles through the effect of both PDA shell and DNA linker on Au@PDA NPs. For investigating the application of such nanoparticles, a highly sensitive assay for miRNA 141 detection was developed using DNA-Au@PDA NPs coupled with dynamic light scattering (DLS). Comparing with the regular DNA-Au NPs, DNA-Au@PDA NPs could detect as low as 50 pM miRNA 141 even in human whole serum. Taken together, the features of Bio/Nanointerface make the nanoparticle suitable for various applications in harsh biological and environmental conditions due to the stability. This work may provide a universal modification method for obtaining stable nanoparticles.

Silver Nanoparticle Surface Enabled Self-Assembly of Organic Dye Molecules

Fluorescence titration of methylene blue, rhodamine B and rhodamine 6G (R6G) by silver nanoparticle (AgNP) all resulted in an initial steep quenching curve followed with a sharp turn and a much flatter quenching curve. At the turn, there are about 200,000 dye molecules per a single AgNP, signifying self-assembly of approximately 36-layers of dye molecules on the surface of the AgNP to form a micelle-like structure. These fluorescence-quenching curves fit to a mathematical model with an exponential term due to molecular self-assembly on AgNP surface, or we termed it "self-assembly shielding effect", and a Stern-Volmer term (nanoparticle surface enhanced quenching). Such a "super-quenching" by AgNP can only be attributed to "pre-concentration" of the dye molecules on the nanoparticle surface that yields the formation of micelle-like self-assembly, resulting in great fluorescence quenching. Overall, the fluorescence quenching titration reveals three different types of interactions of dye molecules on AgNP surface: 1) self-assembly (methylene blue, rhodamine B and R6G), 2) absorption/tight interaction (tryptamine and fluorescein), and 3) loose interaction (eosin Y). We attribute the formation of micelle-like self-assembly of these three dye molecules on AgNP to their positive charge, possession of nitrogen atoms, and with relatively large and flat aromatic moieties.

Simultaneous recognition of cysteine and cytosine using thiophene-based organic nanoparticles decorated with Au NPs and bio-imaging of cells

Biomolecules like cysteine and cytosine play a significant role in many physiological processes, and their unusual level in biological systems can lead to many diseases including cancer. Indeed, the need for selective detection of these moieties by a fluorescence probe is imperative. Thus, thiophene based Schiff N,N'-bis(thiophene-2-ylmethylene)thiophenemethane (BMTM) was synthesized and then characterized using several analytical techniques before converting it into organic nanoparticles (ONPs). Then, fluorescent organic inorganic nanohybrids (FONs) were obtained after decorating ONPs with AuNPs to yield BMTM-Au-ONPs (FONPs). The morphology of the particles, analyzed using a Transmission Electron Microscope (TEM), shows that AuNPs were embedded with low density organic matter (ONPs). FONPs were employed to recognize cysteine and cytosine simultaneously. No interference was observed from other moieties such as guanine, uracyl, NADH, NAD, ATP, and adenine during the detection. It means that the intensity of the fluorescence signal was significantly changed (enhanced for cytosine and quenched for cysteine). So, FONPs were used to detect cysteine and cytosine in real samples, like Saccharomyces cerevisiae cells. As expected, no considerable fluorescence signal for cysteine was observed, while for cytosine, strong fluorescence signals were detected in the cells. DFT was used to explain the interaction of FONPs with cysteine or cytosine.

Facile preparation of graphitic-C3N4 quantum dots for application in two-photon imaging

A novel one-step method for the preparation of g-C₃N₄ QDs for effective two-photon imaging.

Two new quinoline-based regenerable fluorescent probes with AIE characteristics for selective recognition of Cu2+ in aqueous solution and test strips

Two novel highly selective quinoline-based fluorescent probes (1 and 2) with an aggregation induced emission (AIE) feature have been designed and synthesized for the rapid analysis of Cu2+ ions in aqueous media and on paper strips with a fluorescence quenching mechanism. Moreover, probes 1 and 2 exhibit excellent sensitivity and anti-interference for Cu2+ detection, and the detection limits are as low as 1.3 × 10-8 M and 8.5 × 10-8 M, respectively, which are much lower than the allowable standard of Cu2+ (∼20 μM) in drinking water (EPA). More importantly, these two probes were successfully applied for the determination of Cu2+ in real aqueous samples and fabrication of simple device test strips for rapid and on-site detection of Cu2+ ions. Interestingly, they can also be regenerated by adding an excess of S2-. Additionally, the crystallographic structure of probe 1 was confirmed through a single crystal X-ray study. Job's plot analysis and ESI-MS spectroscopic studies reflect the 1 : 1 complexation of the 1-Cu2+ and 2-Cu2+ complexes. Furthermore, DFT/TDDFT calculations were performed in order to help in understanding the electronic properties of the complexes and the chelation-induced quenching mechanism.

One-pot ultrafast preparation of silica quantum dots and their utilization for fabrication of luminescent mesoporous silica nanoparticles

Silica quantum dots (SiQDs) and their luminescent composites have displayed great potential for biomedical applications owing to their chemical inert and low cost. In this work, we report a facile, cost-effective and ultrafast strategy to prepare a stable luminescent SiQDs using N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) and salicylaldehyde as precursors for the first time. These luminescent SiQDs were further utilized for fabrication of luminescent mesoporous silica nanoparticles (MSNs) through direct encapsulation of SiQDs by MSNs. The novel synthetic and modified SiQDs uses commercial raw materials and the entire reaction can be completed within 30 s. The successful preparation of SiQDs and SiQDs@MSNs were characterized by various characterization equipments. The cell viability as well as cell uptake behavior of SiQDs@MSNs were also examined to evaluate their potential for biomedical applications. We demonstrated that these SiQDs@MSNs are low toxicity and of great potential for biological imaging. Based on the above results, we believe that these SiQDs@MSNs should be novel and promising candidates for biomedical applications owing to their intense fluorescence, biocompatibility and high specific surface areas.

Carbon nanoparticles suspension injection for the delivery of doxorubicin: Comparable efficacy and reduced toxicity

Drug delivery systems for doxorubicin (DOX) have attracted tremendous interest nowadays for the improved efficacy and/or reduced toxicity. Due to the aromatic structures and hydrophobic domains, carbon nanoparticle suspension injection (CNSI), a clinical applied reagent for lymph node mapping, strongly adsorbs DOX and holds great potential in cancer therapy. Herein, we evaluated the therapeutic effects of CNSI-DOX to establish its delivery applications for cancer drugs. CNSI adsorbed DOX from solution quickly after the mixing, and the release of DOX from CNSI followed a pH-dependent way. CNSI-DOX and free DOX had nearly identical inhibitive effects on cancer cells, while the vehicle CNSI was nontoxic. CNSI-DOX largely prolonged the life span of ascites tumor bearing mice after the intraperitoneally injection and the ascites weights showed significant decreases. CNSI-DOX also inhibited the growth of subcutaneous xenografts following the same administration route. The therapeutic efficacy of CNSI-DOX was similar to that of free DOX in ascites tumor model, but slightly lower in subcutaneous xenografts model. The advantage of using CNSI was majorly reflected by the reduced toxicity of DOX according to the bodyweight changes, serum biochemical indicators and histopathological observations. The LD₅₀ (median lethal dose) value of CNSI-DOX was 43.8 mg/kg bodyweight, nearly three times of that of free DOX (15.2 mg/kg bodyweight). Our results suggested that CNSI might be used for DOX delivery through "off label" use to benefit the patients immediately.