Chiral Carbon Dots: Synthesis and Applications in Circularly Polarized Luminescence, Biosensing and Biology.

Chiral carbon dots (CDs) are a novel luminescent zero-dimensional carbon-based nanomaterial with chirality. They not only have the advantages of good biocompatibility, multi-color-emission, easy functionalization, but also exhibits highly symmetrical chiral optical characteristics, which broadens their applicability to enantioselectivity of some chiral amino acids like cysteine and lysine, asymmetric catalysis as well as biomedicine in gene expression and antibiosis. In addition, the exploration of the excited state chirality of CDs has developed its excellent circularly polarized luminescence (CPL) properties, opening up a new application scenario like recognition of chiral light sources and anti-counterfeit printing with information encryption. This review mainly focuses on the mature synthesis approaches of chiral CDs, including chiral ligand method and supramolecular self-assembly method, then we consider emerging applications of chiral CDs in CPL, biosensing and biological effect. Finally, we concluded with a perspective on the potential challenges and future opportunities of such fascinating chiral CDs.

Near-infrared phosphorescent carbon dots for sonodynamic precision tumor therapy.

Theranostic sonosensitizers with combined sonodynamic and near infrared (NIR) imaging modes are required for imaging guided sonodynamic therapy (SDT). It is challenging, however, to realize a single material that is simultaneously endowed with both NIR emitting and sonodynamic activities. Herein, we report the design of a class of NIR-emitting sonosensitizers from a NIR phosphorescent carbon dot (CD) material with a narrow bandgap (1.62 eV) and long-lived excited triplet states (11.4 µs), two of which can enhance SDT as thermodynamically and dynamically favorable factors under low-intensity ultrasound irradiation, respectively. The NIR-phosphorescent CDs are identified as bipolar quantum dots containing both p- and n-type surface functionalization regions that can drive spatial separation of e--h+ pairs and fast transfer to reaction sites. Importantly, the cancer-specific targeting and high-level intratumor enrichment of the theranostic CDs are achieved by cancer cell membrane encapsulation for precision SDT with complete eradication of solid tumors by single injection and single irradiation. These results will open up a promising approach to engineer phosphorescent materials with long-lived triplet excited states for sonodynamic precision tumor therapy.

Design and Application of Metal Organic Framework ZIF-90-ZnO-MoS2 Nanohybrid for an Integrated Electrochemical Liquid Biopsy.

Limited healthcare capacity highlights the needs of integrated sensing systems for personalized health-monitoring. However, only limited sensors can be employed for point-of-care applications, emphasizing the lack of a generalizable sensing platform. Here, we report a metal organic framework (MOF) ZIF-90-ZnO-MoS2 nanohybrid-based integrated electrochemical liquid biopsy (ELB) platform capable of direct profiling cancer exosomes from blood. Using a bottom-up approach for sensor design, a series of critical sensing functions is considered and encoded into the MOF material interface by programming the material with different chemical and structural features. The MOF-based ELB platform is able to achieve one-step sensor fabrication, target isolation, nonfouling and high-sensitivity sensing, direct signal transduction, and multiplexed detection. We demonstrated the capability of the designed sensing system on differentiating cancerous groups from healthy controls by analyzing clinical samples from lung cancer patients, providing a generalizable sensing platform.

Hyperphosphorylation of Tau Due to the Interference of Protein Phosphatase Methylesterase-1 Overexpression by MiR-125b-5p in Melatonin Receptor Knockout Mice.

Melatonin has been indicated to ameliorate tau hyperphosphorylation in the pathogenesis of tau diseases, but the role of melatonin-receptor signal transduction has not been clearly discovered. In this study, we found intensive tau hyperphosphorylation in melatonin receptor knockout mice. Bielschowsky silver staining showed ghostlike neurofibrillary tangles in melatonin receptor-2 knockout (MT2KO) as well as melatonin receptors-1 and -2 knockout (DKO) mice, and an argyrophilic substance was deposited in melatonin receptor-1 knockout (MT1KO) mice. Furthermore, we found significantly decreased activity of protein phosphatase 2A (PP2A) by Western blot and enzyme-linked immunosorbent assay (ELISA), which was partly due to the overexpression of protein phosphatase methylesterase-1 (PME-1), but not glycogen synthase kinase-3ß (GSK-3ß), cyclin-dependent kinase 5 (CDK5) or protein kinase B (Akt). Finally, we observed a significant increase in cyclic adenosine monophosphate (cAMP) and a decrease in miR-125b-5p levels in MT1KO, MT2KO and DKO mice. Using a luciferase reporter assay, we discovered that miR-125b-5p largely decreased the expression of firefly luciferase by interfering with the 3'UTR of PME-1. Furthermore, miR-125b-5p mimics significantly decreased the expression of PME-1, while miR-125b-5p inhibitor induced tau hyperphosphorylation. These results show that melatonin-receptor signal transduction plays an important role in tau hyperphosphorylation and tangle formation.

Signal-on electrochemical aptasensors with different target-induced conformations for prostate specific antigen detection.

Prostate specific antigen (PSA) has become a potential biomarker for detecting prostate cancer (PCa) in the early stage. Herein, we report a target-induced resolution for the detection of PSA sensitively and specifically by amperometric electrochemical measurements. To meet a satisfactory performance, three conformations of pre-design DNA aptamers including two stem-loop structures and a double strand structure have been investigated and compared. All of them are immobilized on gold electrode as capture probes with redox-active molecular. The mechanism of signal transduction depends on molecular recognition events involving aptamer conformational changes, thus influencing the charge transfer. A short, single-stranded DNA (ssDNA) pseudoknot forming two stem-loop structural aptamers with labeled MB at the 3' -terminus was found to posse the highest signal variation than other structure when induced by PSA due to the strong conformational change. With the optimized capture strand, the aptasensor showed the peak current increase of MB by the binding relationship between PSA and the sensor over a wide concentration range of 4 magnitude orders. The proposed aptasensor exhibited a wide detection range from 10 pg/mL to 500 ng/mL with a low detection limit of 1.24 pg/mL (S/N = 3). Moreover, the electrochemical aptasensor demonstrated good reproducibility, sensitivity, selectivity, and reliability for the detection of PSA. We also found the aptasensor had a good response in the human serum samples, making this device easy to operate for the detection of the PSA physiological concentration.

Chiral Self-Assembly of Porphyrins Induced by Chiral Carbon Dots.

Chirality plays a key role in many fields ranging from life to natural sciences. For a long time, chiral materials have been developed and used to interact with chiral environments. In recent years, fluorescent carbon dots (CDots) are a new class of carbon nanomaterials exhibit excellent optical properties, good biocompatibility, excellent water solubility, and low cost. However, chirality transfer between semiconductor CDots and organics remains a challenge. Herein, a facile one-step hydrothermal method was used to synthesize chiral CDs from cysteine (cys). The obtained chiral CDots can act as chiral templates to induce porphyrins to form chiral supramolecular assemblies. The successful transmission of chiral information provides more options for the development of various chiral composite materials and the preservation of chiral information in the future.

Phase-Regulated Sensing Mechanism of MoS2 Based Nanohybrids toward Point-of-Care Prostate Cancer Diagnosis.

Alpha-methylacyl-CoA racemase (AMACR) has been proven to be consistently overexpressed in prostate cancer epitheliums, and is expected to act as a positive biomarker for the diagnosis of prostate carcinoma in clinical practice. Here, a strategy for specific determination of AMACR in real human serum by using an electrochemical microsensor system is presented. In order to implement the protocol, a self-organized nanohybrid consisting of metal nanopillars in a 2D MoS2 matrix is developed as material for the sensing interface. The testing signal outputs are strongly enhanced with the presence of the nanohybrids owing to that the metal pillars provide an efficient mass difussion and electron transfer path to the MoS2 film surface. Furthermore, the phase-regulated sensing mechanism over MoS2 is noticed and demonstrated by density functional theory calculation and experiments. The explored MoS2 based nanohybrids are employed for the fabrication of an electrochemical microsensor, presenting good linear relationship in both ng µL-1 and pg µL-1 ranges for AMACR quantification. The sampling analysis of human serum indicates that this microsensor has good diagnostic specificity and sensitivity toward AMACR. The proposed electrochemical microsensor system also demonstrates the advantages of convenience, cost-effectiveness, and disposability, resulting in a potential integrated microsystem for point-of-care prostate cancer diagnosis.

Fibrinogen-templated gold nanoclusters for fluorometric determination of cysteine and mercury(II).

Gold nanoclusters (Au NCs) using fibrinogen (FBG) protein as template are fabricated via one-pot reduction strategy, and applied for fluorometric detections of cysteine (Cys) and mercury(II). The modified FBG-Au NCs exhibit red fluorescence, with excitation/emission maxima at 360/620 nm, a 7% quantum yield, and a 2.2 µs decay time. The fluorescence of the nanoprobe is quenched by Cys and Hg(II). Cys can be determined by fluorometry in the 0.01 to 150 µmol L-1 concentration range and with a detection limit of 0.79 µmol L-1. Due to the oxidation of Hg(II), it can be detected in the 0.01 to 10 µmol L-1 concentration range. The properties of the FBG-Au NCs and the analytical performance are comparable with previously reported peptide/protein-templated Au NCs, supplying a promising candidate for Au NCs nanoprobes synthesis and applications. Graphical abstractSchematic representation of the preparation of gold nanoclusters (Au NCs) using fibrinogen (FBG) as the template. The modified Au NCs were applied to the fluorometric detection of cysteine (Cys) and mercury ion (Hg(II)).

miR-545 promoted enterovirus 71 replication via directly targeting phosphatase and tensin homolog and tumor necrosis factor receptor-associated factor 6.

Enterovirus 71 (EV71) is a small, nonenveloped icosahedral RNA virus and is the predominant causative pathogen of hand-foot-and-mouth disease. Recently, microRNAs (miRNAs) are reported to play important roles in the pathogenesis of EV71 replication. This study investigated the role of miR-545 in the EV71 replication and explored the underlying molecular mechanisms. We showed that miR-545 was upregulated in the EV71-infected human embryonic kidney (HEK) 293 cells and rhabdomyosarcoma (RD) cells. Overexpression of miR-545 promoted the viral replication of EV71 and attenuated the inhibitory effects of EV71 on cell viability in HEK293 and RD cells; while knockdown of miR-545 significantly suppressed the EV71 replication in these two cell lines. Bioinformatics analysis and luciferase reporter assay showed that miR-545 directly targeted the 3'untranslated region of phosphatase and tensin homolog (PTEN) and tumor necrosis factor receptor-associated factor 6 (TRAF6) in HEK293 cells. Furthermore, miR-545 negatively regulated the messenger RNA (mRNA) and protein expression of PTEN and TRAF6. The mRNA and protein expression of PTEN and TRAF6 was also suppressed by EV71 infection, which was attenuated by miR-545 knockdown in HEK293 cells. Overexpression of PTEN and TRAF6 both suppressed the EV71 replication in HKE293 cells, and also attenuated the enhanced effects of miR-545 overexpression on the EV71 replication in HEK293 cells. Collectively, our study for the first time showed that miR-545 had an enhanced effect on the EV71 replication in HEK293 and RD cells. Further mechanistic results indicated that miR-545 promoted EV71 replication at least partly via targeting PTEN and TRAF6.

Novel electrochemiluminescence of silver nanoclusters fabricated on triplex DNA scaffolds for label-free detection of biothiols.

Electrochemiluminescence (ECL) of metal nanoclusters and their application have been widely reported due to the good biocompatibility, fascinating electrocatalytic activity and so on. Using DNA as synthesis template opens new opportunities to modulate the physical properties of AgNCs. Triplex DNA has been reported for the site-specific, homogeneous and highly stable silver nanoclusters (AgNCs) fabrication from our recent research. Here we further explore their extraordinary ECL properties and applications in biosensor utilization. By reasonable design of DNA sequence, AgNCs were obtained in the predefined position of CG.C+ sites of triplex DNA, and the ECL emission at a low potential was observed with this novel DNA template. Finally, a simple and label-free method was developed for biothiols detection based on the enhanced catalytic reaction and a robust interaction between the triplex-AgNCs and cysteine, by influencing the microenvironment provided by DNA template.

The Strica Homolog AaCASPS16 Is Involved in Apoptosis in the Yellow Fever Vector, Aedes albopictus.

Caspases are a family of cysteine proteases playing essential roles during apoptosis. Seven caspases identified in Drosophila were Dronc, Dredd, Strica, Dcp-1, Decay, Drice and Damm. Among them, Strica is an insect-specific caspase containing a long serine- and threonine- rich prodomain, of which function is not yet well studied. Here we identified a homolog of strica from Aedes albopictus, named as Aacasps16. Aacasps16 encoded a protein containing a putative serine- and threonine-rich prodomain and a well conserved caspase catalytic domain. AaCASPS16 shared high identity with dipteran insects Strica homologs. Alignment showed that the closest relative of AaCASPS16 was Aedes aegypti AeCASPS16. The expression profiles of Aacasps16 during developmental and adult stages were analyzed. Purified recombinant AaCASPS16 exhibited the highest caspase activity to WEHD, which is the substrate preferred by human caspase-9. AaCASPS16 induced apoptosis when over-expressed in C6/36 cells. AaCASPS16 was processed during apoptosis induced by actinomycin D and ultraviolet irradiation treatment, whereas partial silencing of Aacasps16 reduced actinomycin D- and ultraviolet irradiation-triggered apoptosis in C6/36 cells. Taken together, our study identified AaCASPS16 as a novel apoptotic caspase in Aedes albopictus.

Electrochemical current rectification-a novel signal amplification strategy for highly sensitive and selective aptamer-based biosensor.

Electrochemical aptamer-based (E-AB) sensors represent an emerging class of recently developed sensors. However, numerous of these sensors are limited by a low surface density of electrode-bound redox-oligonucleotides which are used as probe. Here we propose to use the concept of electrochemical current rectification (ECR) for the enhancement of the redox signal of E-AB sensors. Commonly, the probe-DNA performs a change in conformation during target binding and enables a nonrecurring charge transfer between redox-tag and electrode. In our system, the redox-tag of the probe-DNA is continuously replenished by solution-phase redox molecules. A unidirectional electron transfer from electrode via surface-linked redox-tag to the solution-phase redox molecules arises that efficiently amplifies the current response. Using this robust and straight-forward strategy, the developed sensor showed a substantial signal amplification and consequently improved sensitivity with a calculated detection limit of 114nM for ATP, which was improved by one order of magnitude compared with the amplification-free detection and superior to other previous detection results using enzymes or nanomaterials-based signal amplification. To the best of our knowledge, this is the first demonstration of an aptamer-based electrochemical biosensor involving electrochemical rectification, which can be presumably transferred to other biomedical sensor systems.

Functionalized graphene as sensitive electrochemical label in target-dependent linkage of split aptasensor for dual detection.

A new type of electrochemical aptasensor was reported here for highly sensitive detection of adenosine triphosphate (ATP) and adenosine deaminase (ADA) activity using functionalized graphene as efficient electrochemical label. The specific binding of ATP and its aptamer could link the split aptamers modified graphene and magnetic beads together. After ADA catalysis and magnetic separation, graphene material anchored on electrode surface would efficiently facilitate electron transfer, thus produce detectable electrochemical signals. The detection limits for ATP and ADA activity were 13.6 nM and 0.01 unit/mL (~1.2 nM), respectively. Our work would supply new horizons for the diagnostic applications of graphene-based materials in biomedicine and biosensors.

New horizons for diagnostics and therapeutic applications of graphene and graphene oxide.

Graphene, a one-atom-thick two-dimensional (2D) layer of sp(2) -bonded carbon, has received worldwide attention owing to its extraordinary physical and chemical properties. Recently, great efforts have been devoted to explore potential applications of graphene and its oxide in life science, especially in disease-related diagnostics, near-Infrared (NIR) phototherapy and imaging. Here we will introduce recent advances and new horizons in this area, and focus on the rising progress on NIR photothermal therapy for cancer and Alzheimer's disease (AD), human telomerase detection, stem cell proliferation and differentiation on graphene substrate, diagnosis of cancer cell and related biomarkers, drug/nucleotide/peptide delivery and cell imaging, which have not been comprehensively reviewed. We hope to provide an outlook to the applications of graphene and its oxide, especially on the new horizons in this field, and inspire broader interests across various disciplines.

Label-free ultrasensitive detection of human telomerase activity using porphyrin-functionalized graphene and electrochemiluminescence technique.

Using porphyrin-functionalized graphene, we construct a PCR-free, low-cost, rapid, and electrochemiluminenscence (ECL) assay for detection of telomerase activity that has been demonstrated in six different cell lines and can be used as initial screening of G-quadruplex DNA binding agents and telomerase inhibitors. This ECL sensor shows highly sensitive for detection of telomerase with the detection limit as low as 10 HeLa cells mL(-1) .

Selective and quantitative cancer cell detection using target-directed functionalized graphene and its synergetic peroxidase-like activity.

We report here a folic acid conjugated graphene-hemin composite for selective, quantitative and fast colorimetric detection of cancer cells based on the peroxidase-like activity.

A graphene functionalized electrochemical aptasensor for selective label-free detection of cancer cells.

Here we report an electrochemical sensor that can realize label-free cancer cell detection using the first clinical trial II used aptamer AS1411 and functionalized graphene. By taking advantages of AS1411 high binding affinity and specificity to the overexpressed nucleolin on the cancer cell surface, our developed electrochemical aptasensor can distinguish cancer cells and normal ones and detect as low as one thousand cells. With DNA hybridization technique, this E-DNA sensor can be regenerated and reusable for cancer cell detection. Our work gives a good example for label-free cancer cell detection based on aptamer and graphene-modified electrode.

7-Amino actinomycin D bound to single-stranded hairpin DNA enhanced by loop sequence-dependent luminescent Eu(3+) and Tb(3+) binding.

Lanthanide Eu(3+) and Tb(3+) ions have been widely used in luminescent resonance energy transfer (LRET) for bioassays to study metal binding microenvironments. We report here that Eu(3+) or Tb(3+) can increase the binding affinity of antitumor antibiotic drug agent, 7-amino actinomycin D (7AACTD), binding to 5'-GT/TG-5' or 5'-GA/AG-5' mismatched stem region of the single-stranded hairpin DNA. Further studies indicate that the effect of Eu(3+) or Tb(3+) on 7AACTD binding is related to DNA loop sequence. Our results will provide new insights into how metal ions can enhance antitumor agents binding to their targets.

i-Motif quadruplex DNA-based biosensor for distinguishing single- and multiwalled carbon nanotubes.

The increasing worldwide demand for carbon nanotubes (CNTs) and increasing concern regarding how to safely develop and use CNTs are requiring a low-cost, simple, and highly sensitive CNT detection assay for toxicological evaluation and environmental monitoring. However, this goal is still far from being achieved. All the current CNT detection techniques are not applicable for automation and field analysis because they are dependent on highly expensive special instruments and complicated sample preparation. On the basis of the capability of single-walled carbon nanotubes (SWNTs) to specifically induce human telomeric i-motif formation, we design an electrochemical DNA (E-DNA) sensor that can distinguish single- and multiwalled carbon nanotubes both in buffer and in cell extracts. The E-DNA sensor can selectively detect SWNTs with a direct detection limit of 0.2 ppm and has been demonstrated in cancer cell extracts. To the best of our knowledge, this is the first demonstration of a biosensing technique that can distinguish different types of nanotubes. Our work will provide new insights into how to design a biosensor for detection of carbon nanotubes.