Carbon nanodots are fascinating candidates for the field of biomedicine, in applications such as bioimaging and drug delivery. However, the nuclear penetrability and process are rarely studied and lack understanding, which limits their applications for drug carriers, single-molecule detection and live cell imaging. In this study, we attempt to examine the uptake of CNDs in cells with a focus on the potential nuclear penetrability using enhanced dark-field microscopy (EDFM) associated with hyperspectral imaging (HSI) to quantitatively determine the light scattering signals of CNDs in the cells. The effects of both CND incubation time and concentration are investigated, and plausible nuclear penetration involving the nuclear pore complex (NPC) is discussed. The experimental results and an analytical model demonstrate that the CNDs’ uptake proceeds by a concentration-dependent three-stage behavior and saturates at a CND incubation concentration larger than 750 µg/mL, with a half-saturated concentration of 479 μg/mL. These findings would potentially help the development of CNDs’ utilization in drug carriers, live cell imaging and other biomedical applications.

Polymer-inorganic nanocomposites based on polymer-grafted nanocrystals (PGNCs) are enabling technologically relevant applications owing to their unique physical, chemical, and mechanical properties. While diverse PGNC superstructures have been realized through evaporation-driven self-assembly, this approach presents multifaceted challenges in experimentally probing and controlling assembly kinetics. Here, we report a kinetically controlled assembly of binary superstructures from a homogeneous disordered PGNC mixture utilizing solvent vapor annealing (SVA). Using a NaZn13-type superstructure as a model system, we demonstrate that varying the solvent vapor pressure during SVA allows for exquisite control of the rate and extent of PGNC assembly, providing access to nearly complete kinetic pathways of binary PGNC crystallization. Characterization of kinetically arrested intermediates reveals that assembly follows a multistep crystallization pathway involving spinodal-like preordering of PGNCs prior to NaZn13 nucleation. Our work opens up new avenues for the synthesis of multicomponent PGNC superstructures exhibiting multifunctionalities and emergent properties through a thorough understanding of kinetic pathways.

Amphiphilic phospholipid-iodinated polymer conjugates were designed and synthesized as new macromolecular probes for a highly radiopaque and biocompatible imaging technology. Bioconjugation of PEG 2000-phospholipids and iodinated polyesters by click chemistry created amphiphilic moieties with hydrophobic polyesters and hydrophilic PEG units, which allowed their self-assemblies into vesicles or spiked vesicles. More importantly, the conjugates exhibited high radiopacity and biocompatibility in in vitro X-ray and cell viability measurements. This new type of bioimaging contrast agent with a Mn value of 11 289 g mol-1 was found to have a significant X-ray signal at 3.13 mg mL-1 of iodine equivalent than baseline and no cytotoxicity after 48 hours incubation of with HEK and 3T3 cells at 20 μM (20 picomoles) concentration of conjugates per well. The potential of adopting the described macromolecular probes for bioimaging was demonstrated, which could further promote the development of a field-friendly and highly sensitive bioimaging contrast agent for point-of-care diagnostic applications.

This work reports on uniformly mingled nanostructures of Co3O4 and MnO2 deposited on a well-aligned electrospun carbon nanofiber (WA-ECNF) mat for rapid glucose electrooxidation and sensing. The hybridization of Co3O4 and MnO2 is synthesized by a simple one-step and template-free electrodeposition technique with a constant low current at 60 mu A for 3 h at room temperature in an aqueous solution. The binary MnO2/Co3O4@WA-ECNF nanomatrix electrode exhibits excellent uniformity with high porosity, increased electrochemically active surface areas and conductivity, fast charge transfer, and improved efficiency for glucose electrooxidation in comparison to the monometallic MnO2 or Co3O4 at the WA-ECNFs. The electrochemical performance of the MnO2/Co3O4@ECNF electrode is characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). The MnO2/Co3O4@ECNE electrode shows superior sensing characteristics including a rapid glucose oxidation response within 5 s, a wide range of detection from 5 mu M to 10.9 mM, an excellent sensitivity of 1159 mu A mM(-1) cm(-2), and a detection limit of 0.3 mu M (S/N = 3) with satisfactory selectivity, great reproducibility, and stability. These results are discussed with mechanisms of glucose absorption to the nanostructure surfaces followed by a fast glucose oxidation reaction.

全氟/多氟烷基化合物(per-and polyfluoroalkyl substances,PFASs)是食品接触材料中的风险物质,由它所引起的食品安全问题,是国际国内社会关注的焦点.因此研究广泛存在的PFASs给社会群体带来的问题,提高社会各界的意识,引导对PFASs替代品的思考,具有十分重要的意义.本文分析了食品接触材料中PFASs的应用及膳食暴露,PFASs对人体健康的危害,总结了国际各主要贸易体的监管措施,简单梳理了PFASs替代品的研究进展,对各利益相关方提出了要求和建议,并展望了研发绿色的非氟PFASs替代品的发展趋势.

The agglomeration of spherulites during isothermal crystallization of olefin multiblock copolymers and the role of mesophase separation on the agglomeration behavior were investigated by a new rheological method, which is based on the analogy between crystal morphology and particle suspension in polymeric matrix. The new suspension-based rheological method solved the problem of frequency dependency, which was encountered in the traditional rheological study in determination of the fraction of transformation. It was achieved by decomposing the time-resolved dynamic moduli during crystallization into the hydrodynamic part and the agglomerates' part using a two-step shifting procedure. The relative crystallinity determined from the product of two shifting factors, the strain rate amplification factor and the stress amplification factor, was consistent with the DSC measurements. Moreover, the dependence of the agglomerates' contribution to the storage modulus of the crystal (G'(Agg)) on its volume fraction (phi(rheo)) was found to be independent of the crystallization temperature, resulting in a master curve G'(Agg) vs phi(rheo) that could be used as a unique parameter to characterize the agglomeration of spherulites. For olefin block copolymers with similar hard-block content (or crystallinity), it was found that mesophase separation not only delayed the agglomeration of spherulites but also changed its packing behavior. Comparisons with polymer nanocomposites further illustrated the differences in the spatial distribution and agglomeration of "fillers" in polymer nanocomposites, homogeneous semicrystalline polymers, and heterogeneous semicrystalline polymers.

A polymerization reaction was employed as a signal amplification method to realize direct visualization of gender-specific DNA extracted from human blood in a polymerase chain reaction (PCR)-free fashion. Clear distinction between X and Y chromosomes was observed by naked eyes for detector-free sensing purposes. The grown polymer films atop X and Y chromosomes were quantitatively measured by ellipsometry for thickness readings. Detection assays have been optimized for genomic DNA recognition to a maximum extent by varying the selection of the proper blocking reagents, the annealing temperature, and the annealing time. Traditional PCR and gel electrophoresis for amplicon identification were conducted in parallel for performance comparison. In the blind test for blood samples examined by the new approach, 25 out of 26 were correct and one was false negative, which was comparable to, if not better than, the PCR results. This is the first time our amplification-by-polymerization technique is being used for chromosome DNA analysis. The potential of adopting the described sensing technique without PCR was demonstrated, which could further promote the development of a portable, PCR-free DNA sensing device for point-of-need applications.

The crystallization of two high impact polypropylenes (HIPP) was investigated under shear flow by online rheo-Raman spectroscopy. Abnormal retardation of crystallization under shear is observed in one HIPP, but the usual shear accelerated crystallization is observed in the other one. Such abnormal phenomenon was understood by thorough investigations on the phase separation behaviors in two HIPPs by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rheology. The slowdown of crystallization under shear can be ascribed to the suppression of the interface and fluctuation assisted nucleation under shear, which cannot be compensated by the acceleration effect due to molecular stretching/orientation under shear. The difference between two HIPP comes from the interplay between the suppression and acceleration effect of shear flow, which is determined by the amount of ethylene-propylene segmented copolymer (EPS) and its selective location in isotactic polypropylene (iPP) and ethylene-propylene random copolymer (EPR).

The crystallization behaviors of olefin multiblock copolymers were investigated by Raman spectroscopy. A new approach was proposed to fulfill the Raman three phase analysis. The crystallinity obtained from such approach is well consistent with the method using melt Raman spectrum as a reference. It is found that both the Raman total crystalline fraction and the Raman orthorhombic crystalline fraction are affected by the hard block content of OBCs. Non-isothermal experiments on melting and crystallization illustrate that Raman spectrum and DSC can give identical transition temperatures. However, Raman spectrum analysis shows two distinct features during crystallization and melting of OBCs, namely the disappearance of all-trans noncrystalline phase at temperature much higher than the melting point and the dynamic balance of the interfacial phase fraction.

A delayed liquid–solid transition has been found in strongly segregated olefin multiblock copolymers, compared to that in weakly segregated systems.

Chain shuttling polymerization enables an efficient production of ethylene octene block copolymers (OBCs) that combine different mechanical properties in a polymer chain. However, this method results in molecular weight polydispersity and multiblock chain structure. The melt-phase behavior and mesophase transition of the polydisperse OBCs with low octene content but different molecular weight and block composition were investigated by rheology, differential scanning calorimetry (DSC), atomic force microscopic (AFM), polarized optical microscopy (POM), and small-angle X-ray scattering (SAXS). Three rheological methods, namely the deviation of the scaling dependence of zero shear viscosity on molecular weight, the terminal behavior and the failure of time temperature superposition (TTS), and two-dimensional rheological correlation spectrum, are used to reveal the mesophase separation with increasing sensitivity. The occurrence of mesophase separation transitions (MST) was observed in such low octene content and low molecular weight OBC systems, with much lower degree of segregation than the theoretical predictions in diblock copolymers. The extent of mesophase separation is further justified by its effect on subsequent crystallization behaviors.

The compatibility between olefin block copolymers ( OBC1 and OBC2 ) and isotactic polypropylene ( iPP ) was studied in this work. The two OBCs have similar hard block content and octene content, but are different in molecular weight. The linear viscoelasticity of OBCs were systematically studied. It was found from linear viscoelasticity that OBC1 with high molecular weight tends to exhibit strong mesophase separation,while OBC2 with low molecular weight is homogeneous in the studied temperature range. The interfacial tensions between OBCs and iPP were measured by drop retraction and dynamic rheological method. Both methods have achieved consistent results for the interfacial tension of the blends. The interfacial tension between iPP/OBC1 is around 1. 17 mN/m,which is larger than that between iPP/OBC2 (about 0. 3 mN/m). The variation of glass transition temperature in iPP/OBC blends were also studied by dynamic mechanical analysis, and depressions in the glass transition temperature of iPP were observed in both blends, from which the solubility of OBCs in iPP was estimated by self-concentration model. It was found that although the interfacial tension between OBC1 and iPP is larger, their miscibility is better. This is ascribed to the strong mesophase separation of OBC1. Further study on the crystallization of iPP in blends also justified the miscibility difference between iPP and the two OBCs.

A novel multi-channel poly(methyl methacrylate) (PMMA) microfluidic biosensor with interdigitated ultramicroelectrode arrays (IDUAs) for electrochemical detection was developed. The focus of the development was a simple fabrication procedure and the realization of a reliable large IDUA that can provide detection simultaneously to several microchannels. As proof of concept, five microchannels are positioned over a large single IDUA where the channels are parallel with the length of the electrode finger. The IDUAs were fabricated on the PMMA cover piece and bonded to a PMMA substrate containing the microfluidic channels using UV/ozone-assisted thermal bonding. Conditions of device fabrication were optimized realizing a rugged large IDUA within a bonded PMMA device. Gold adhesion to the PMMA, protective coatings, and pressure during bonding were optimized. Its electrochemical performance was studied using amperometric detection of potassium ferri and ferro hexacyanide. Cumulative signals within the same chip showed very good linearity over a range of 0–38 μM (R 2 = 0.98) and a limit of detection of 3.48 μM. The bonding of the device was optimized so that no cross talk between the channels was observed which otherwise would have resulted in unreliable electrochemical responses. The highly reproducible signals achieved were comparable to those obtained with separate single-channel devices. Subsequently, the multi-channel microfluidic chip was applied to a model bioanalytical detection strategy, i.e., the quantification of specific nucleic acid sequences using a sandwich approach. Here, probe-coated paramagnetic beads and probe-tagged liposomes entrapping ferri/ferro hexacyanide as the redox marker were used to bind to a single-stranded DNA sequence. Flow rates of the non-ionic detergent n-octyl-β-d-glucopyranoside for liposome lysis were optimized, and the detection of the target sequences was carried out coulometrically within 250 s and with a limit of detection of 12.5 μM. The robustness of the design and the reliability of the results obtained in comparison to previously published single-channel designs suggest that the multi-channel device offers an excellent opportunity for bioanalytical applications that require multianalyte detection and high-throughput assays.

Vasopressin is an indicating biomarker for blood pressure in the human body and low vasopressin levels can be indicative of late-phase hemorrhagic shock or other traumatic injuries. In this paper we have developed an aptamer-based label-free microfluidic biosensor for the electrochemical detection of vasopressin. The detection area consists of aptamers immobilized on carbon nanotubes which specifically capture the vasopressin molecules in solution resulting in changes in conductivity across the sensor. We report a limit of detection of 43 pM in standard solutions and demonstrate high detection specificity toward vasopressin when different interferents are present. The miniaturized microfluidic biosensor offers continuous monitoring of different vasopressin levels with good potential for portability. Ultimately such a system could serve as a point-of-care diagnostics tool for patients with excessive bleeding when standard medical infrastructure is not available.

We report the use of reversible addition–fragmentation chain transfer (RAFT) polymerization as a highly efficient chemical amplification means to direct visualization of DNA in porous polyacrylamide gel. It is the first time that a dynamic polymer growth on the surface of soft medium is used in signal amplification for DNA detection. In the proof-of-concept experiment, a thin acrylamide gel on a glass microscope slide formed a thin layer of uniformly crosslinked network with porous structures. Oligonucleotides of different sequences were entrapped within the gel at separate spots. Hybridization of complementary DNA detection probes introduced chain transfer agents (CTAs) into the gel via preconjugation to the probes. Surface-initiated polymer growth was prompted on the gel surface and the growth of polymer brushes at the spot where DNA hybridization occurred was monitored using infrared spectroscopy and atomic force microscopy. Visible change in the texture of the porous gel occurred after polymer growth, which offered an attractive detection alternative for in-gel DNA analysis. Compared to the results from traditional ethidium bromide staining, better detection sensitivity and specificity were achieved.

A series of novel long-chain hyperbranched poly(ethylene glycol)s (LHPEGs) with biodegradable connections were designed and synthesized in one pot through proton-transfer polymerization using PEG and commercial glycidyl methacrylate as monomers and potassium hydride as catalyst. The LHPEGs were hydrolyzed at neutral pH resulting in the decrease of molecular weights. In vitro evaluation demonstrated that LHPEGs were biocompatible and displayed negligible hemolytic activity. The efficient cellular uptake of LHPEGs was confirmed by flow cytometry and confocal laser scanning microscopy. Moreover, conjugation of a model hydrophobic anticancer drug methotrexate to LHPEGs inhibited the proliferation of a human cervical carcinoma Hela cell line. MTT assay indicated that the conjugated methotrexate dose required for 50% cellular growth inhibition against Hela cells was 20 μg/mL. By combining the advantages of long-chain hyperbranched structure and PEG, LHPEG provides a promising drug carrier for therapeutic fields.

We report here an approach to grafting DNA-polymer bioconjugates on a planar solid support using reversible addition-fragmentation chain transfer (RAFT) polymerization. In particular, a trithiocarbonate compound as the RAFT chain transfer agent (CTA) is attached to the distal point of a surface-immobilized oligonucleotide. Initiation of RAFT polymerization leads to controlled growth of polymers atop DNA molecules on the surface. Growth kinetics of poly(monomethoxy-capped oligo(ethylene glycol) methacrylate) atop DNA molecules is investigated by monitoring the change of polymer film thickness as a function of reaction time. The reaction conditions, including the polymerization temperature, the initiator concentration, the CTA surface density, and the selection of monomers, are varied to examine their impacts on the grafting efficiency of DNA-polymer conjugates. Comparing to polymer growth atop small molecules, the experimental results suggest that DNA molecules significantly accelerate polymer growth, which is speculated as a result of the presence of highly charged DNA backbones and purine/pyrimidine moieties surrounding the reaction sites.

A simple three-step strategy to functionalize multiwalled carbon nanotubes using 1,2-distearoyl-sn-glycero-3-phosphoethanolamine phospholipids has been described. The resulting phospholipid-modified multiwalled carbon nanotubes were analyzed by TEM, AFM, NMR, IR, UV–vis and TGA techniques. The experimental results show that the use of amine-terminated phospholipids not only improves the dispersity of multiwalled carbon nanotubes in both aqueous and organic solvents greatly, but also results in the significant enhancement of biocompatibility. These findings will serve as a future biological platform for new devices ranging from biosensors to nano-detectors.

By increasing the hydrophobicity of end group, the complexation rate between α-cyclodextrin (α-CD) and poly(ethylene glycol) (PEG) derivative speeds up greatly. Based on such a huge difference of complexation kinetics, the PEG derivative with palmityloxy terminal (PEG-C16) can be successfully separated from a carboxylic acid end-functionalized analogue (PEG-COOH) by once supramolecular purification. Adding α-CD into the aqueous solution of PEG-C16/PEG-COOH mixture, PEG-C16 is encapsulated into α-CD cavity to form the crystalline inclusion complex in a very short time, while almost all of PEG-COOH molecules are still reserved in the aqueous solution. After dichloromethane extraction, the pure PEG-C16 is obtained. Moreover, the host CD can be recycled. Thus, it is an efficient green way to separate and purify the linear polymers with different terminal functionality.

A general strategy for realizing the self-assembly of aqueous CdTe nanocrystals (NCs) at the water/oil interface by means of an amphiphilic core-shell hyperbranched polymer has been proposed. Aqueous CdTe NCs were firstly transferred into the chloroform phase in the presence of palmityl chloride functionalized hyperbranched poly(amidoamine) (HPAMAM-PC), and then self-assembled at the water/chloroform interface by decreasing the pH value of the aqueous phase or introducing α-CDs to the aqueous phase. The resulting CdTe/HPAMAM-PC self-assembly film was characterized by fluorescence microscopy, UV–vis, PL, TEM, EDS, FT-IR, DSC and TGA. S Supplementary data are available from stacks.iop.org/Nano/19/445609