PMMA Microspheres with Embedded Lanthanide Nanoparticles by Photoinitiated Dispersion Polymerization with a Carboxy-Functional Macro-RAFT Agent

Functional poly­(methyl methacrylate) (PMMA) microbeads with a very narrow size distribution were synthesized by photoinitiated RAFT dispersion polymerization in aqueous ethanol using an acrylic acid–oligo­(ethylene glycol) copolymer as a macro-RAFT agent. These particles are a prototype for multiparameter bead-based assays employing mass cytometry, a technique in which metal-encoded beads are injected into the plasma torch of an inductively coupled plasma mass spectrometer (ICP-MS), and the metal ions generated are detected by time-of-flight mass spectrometry. To label the beads, the polymerization reaction was carried out in the presence of various types of small (ca. 5 nm) lanthanide fluoride (LnF₃) nanoparticles (e.g., LaF₃, CeF₃, and TbF₃) with polymerizable methacrylate groups on their surface. The type of metal ion and the metal content of the PMMA microbeads could be varied by changing the composition of the reaction medium. An important feature of these microbeads is that acrylic acid groups in the corona are available for covalent attachment of biomolecules. As a proof of concept, FITC–streptavidin (FITC-SAv) was covalently coupled to the surface of a Ln-encoded microbead sample. The number of FITC-SAv binding sites on the beads was determined through three parallel assays involving biotin derivatives. Interaction of the beads with a biotin–tetramethylrhodamine derivative was monitored by fluorescence, whereas interaction of the beads with a biotin-DOTA-Lu derivative was monitored both by ICP-MS and by mass cytometry. Each measurement detected an average of ca. 5 × 10⁴ biotins per microsphere. Control experiments with beads covalently labeled with FITC–bovine serum albumin (FITC-BSA) showed only very low levels of nonspecific binding

Functional PEG–PAMAM-Tetraphosphonate Capped NaLnF₄ Nanoparticles and their Colloidal Stability in Phosphate Buffer

Developing surface coatings for NaLnF₄ nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH₂-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF₄ and NaTbF₄ nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH₂-PAMAM-4P ligand on oleate-capped NaLnF₄ NPs. The NPs were first treated with methoxy-poly­(ethylene glycol)-monophosphoric acid (<i>M</i>_n = 750) in tetrahydrofuran. The mPEG750-OPO₃-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH₂-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (<i>M</i>_n = 2000) and biotin-terminated PEG (<i>M</i>_n = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF₄ and NaTbF₄ NPs capped with mPEG2000–PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF₄ NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir 2012, 28, 12861−12870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline

Synthesis of Uniform NaLnF₄ (Ln: Sm to Ho) Nanoparticles for Mass Cytometry

Over the past decade, there have been extensive developments in the field of lanthanide-based nanoparticles (NPs). Most studies have focused on the application of upconverting NaYF₄-based NPs for deep tissue imaging and paramagnetic NaGdF₄ NPs for MRI. Current applications for the remaining members of the lanthanide series are rather limited. Recently, a novel bioanalytical technique known as mass cytometry (MC) has been developed which can benefit from the entire lanthanide series of NPs. MC is a high-throughput multiparametric cell-by-cell analysis technique based on atomic mass spectrometry that uses antibodies labeled with metal isotopes for biomarker detection. NaLnF₄ NPs offer the promise of high sensitivity coupled with multiparameter detection, provided that NPs can be synthesized with a narrow size distribution. Here we describe the synthesis of six members of this NP family (NaSmF₄, NaEuF₄, NaGdF₄, NaTbF₄, NaDyF₄, NaHoF₄) with the appropriate size (5–30 nm) and size distribution (CV < 5%) for MC. We employed the coprecipitation method developed by Li and Zhang [<i>Nanotechnology</i> <b>2008</b>, <i>19</i>, 345606], and for each member of this series, we examined the heating rate, final reaction temperature, and composition of the reaction mixture in an attempt to optimize the synthesis. For each of the six NaLnF₄, in the range of the target sizes, we were able to identify “sweet spots” in the reaction conditions to obtain NPs with a narrow size distribution. In addition, we investigated the oleate surface coverage of the NPs and the effect of long-term storage (2 years) on the colloidal stability of the NPs. Finally, NaTbF₄ NPs were rendered hydrophilic via lipid encapsulation and tested for nonspecific binding with KG1a and Ramos cells by mass cytometry

Synthesis of PMMA Microparticles with a Narrow Size Distribution by Photoinitiated RAFT Dispersion Polymerization with a Macromonomer as the Stabilizer

Macromonomers can serve as efficient and effective stabilizers for dispersion polymerization of monomers such as styrene and methyl methacrylate, but the size distributions of the polymer microparticles obtained tend to be broad. We are interested in functional microbeads which can be used for immunoassays, where the size distribution has to be very narrow. We report a photoinitiated RAFT dispersion polymerization of methyl methacrylate (MMA) in ethanol–water mixtures, with methoxy-poly­(ethylene glycol) methacrylate (<i>M</i>_n = 2000 g/mol, EO₄₅) as the reactive steric stabilizer. We identify reaction conditions where one can obtain PMMA microspheres with coefficient of variation in the particle diameter (CV_d) less than 3%. Carboxy-functional PMMA microspheres were obtained by a two-stage (seeded) polymerization with methacrylic acid (MAA) added as a comonomer in the second stage. We show that the functional microspheres prepared in this way are effective substrates for the covalent attachment of proteins such as BSA and IgG immunoglobulins. In one set of experiments with a dye-labeled secondary antibody, we found that we could detect 10⁴ IgGs per PMMA microbead

Improving Lanthanide Nanocrystal Colloidal Stability in Competitive Aqueous Buffer Solutions using Multivalent PEG-Phosphonate Ligands

The range of properties available in the lanthanide series has inspired research into the use of lanthanide nanoparticles for numerous applications. We aim to use NaLnF₄ nanoparticles for isotopic tags in mass cytometry. This application requires nanoparticles of narrow size distribution, diameters preferably less than 15 nm, and robust surface chemistry to avoid nonspecific interactions and to facilitate bioconjugation. Nanoparticles (NaHoF₄, NaEuF₄, NaGdF₄, and NaTbF₄) were synthesized with diameters from 9 to 11 nm with oleic acid surface stabilization. The surface ligands were replaced by a series of mono-, di-, and tetraphosphonate PEG ligands, whose synthesis is reported here. The colloidal stability of the resulting particles was monitored over a range of pH values and in phosphate containing solutions. All of the PEG-phosphonate ligands were found to produce non-aggregated colloidally stable suspensions of the nanoparticles in water as judged by DLS and TEM measurements. However, in more aggressive solutions, at high pH and in phosphate buffers, the mono- and diphosphonate PEG ligands did not stabilize the particles and aggregation as well as flocculation was observed. However, the tetraphosphonate ligand was able to stabilize the particles at high pH and in phosphate buffers for extended periods of time

Mesoporous Silica Nanoparticles-Encapsulated Agarose and Heparin as Anticoagulant and Resisting Bacterial Adhesion Coating for Biomedical Silicone

Silicone catheter has been widely used in peritoneal dialysis. The research missions of improving blood compatibility and the ability of resisting bacterial adhesion of silicone catheter have been implemented for the biomedical requirements. However, most of modification methods of surface modification were only able to develop the blood-contacting biomaterials with good hemocompatibility. It is difficult for the biomaterials to resist bacterial adhesion. Here, agarose was selected to resist bacterial adhesion, and heparin was chosen to improve hemocompatibility of materials. Both of them were loaded into mesoporous silica nanoparticles (MSNs), which were successfully modified on the silicone film surface via electrostatic interaction. Structures of the mesoporous coatings were characterized in detail by dynamic light scattering, transmission electron microscopy, Brunauer–Emmett–Teller surface area, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope, and water contact angle. Platelet adhesion and aggregation, whole blood contact test, hemolysis and related morphology test of red blood cells, in vitro clotting time tests, and bacterial adhesion assay were performed to evaluate the anticoagulant effect and the ability of resisting bacterial adhesion of the modified silicone films. Results indicated that silicone films modified by MSNs had a good anticoagulant effect and could resist bacterial adhesion. The modified silicone films have potential as blood-contacting biomaterials that were attributed to their biomedical properties

Porphyrin Nanoassemblies <i>via</i> Surfactant-Assisted Assembly and Single Nanofiber Nanoelectronic Sensors for High-Performance H₂O₂ Vapor Sensing

Porphyrins are recognized as important π-conjugated molecules correlating supramolecular chemistry, nanoscience, and advanced materials science. So far, as their supramolecular nanoassemblies are addressed, most efforts focus on the photo- or opto-related subjects. Beyond these traditional subjects, it is strongly desired to develop advanced porphyrin nanoassemblies in some other new topics of paramount importance. By means of a surfactant-assisted assembly, we herein show that porphyrins of different central metal ions, 5,10,15,20-tetra(4-pyridyl)-21<i>H</i>,23<i>H</i>-porphine (H2TPyP), zinc 5,10,15,20-tetra(4-pyridyl)-21<i>H</i>,23<i>H</i>-porphine (ZnTPyP), and oxo-[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) (TiOTPyP), could be organized to form irregular aggregates, short nanorods, and long yet straight nanofibers, respectively. Remarkably, in terms of an organic ribbon mask technique, we show that such long yet straight TiOTPyP nanofibers could be integrated into single nanofiber-based two-end nanoelectronics. Such simple nanodevices could serve as high-performance sensors of a satisfactory stability, reproducibility, and selectivity for an expeditious detection of vapor-phase H₂O₂. This provides a new alternative for a fast sensing of vapor-phase H₂O₂, which is currently an important issue in the fields of anti-terrorism, industrial healthcare, <i>etc.</i> In contrast to the traditional investigations focusing on the photo- or opto-related topics, our work endows porphyrin nanostructures with new opportunities as advanced nanomaterials in terms of portable yet high-performance nanoelectronic sensors, which is an issue of general concern in modern advanced nanomaterials

High Performance Nanocrystals of a Donor–Acceptor Conjugated Polymer

Highly crystalline, well-defined nanowires of a donor–acceptor (D–A) conjugated polymer based on bithiazole-thiazolothiazole (PTz) were successfully prepared by a facile solution self-assembly method. In PTz nanowires, polymer chains align along the long axis of the nanowires forming lamellar structures with close π-stacking perpendicular to the long axis of the nanowires. The nanowires possess a single crystal structure with orthorhombic crystal unit cell in which the lattice parameters are <i>a</i> ≈ 21.05 Å, <i>b</i> ≈ 6.94 Å, and <i>c</i> ≈ 4.64 Å. The intrinsic charge transport property of PTz was characterized by using its single crystal nanowires in field-effect transistors with a mobility up to 0.46 cm² V^–1 s^–1. As an example of PTz single crystal nanowires in optoelectronic application, phototransistors of PTz nanowires exhibited a photoresponsivity up to 2531 A W^–1 and a photosensitivity up to 1.7 × 10⁴

Stress tolerance validation of lines 898 and 1812 by retransformation.

<p>For osmotic or salt stress treatment, 15-day-old seedlings were transferred to a culture solution containing 20% (w/v) PEG-4000 (to simulate drought stress) or 150 mM NaCl, respectively. After 2 weeks of treatment, the osmotic stress tolerance of line 898 (A) and salt stress tolerance of line 1812 (B) reappeared in the retransformed plants.</p

The 1,455 transcription factors (TFs) belonging to 45 families used to construct the FOX system.

<p>The 1,455 transcription factors (TFs) belonging to 45 families used to construct the FOX system.</p