Patterned nanoparticle assembly methodology

Methods for forming a nanoparticle assembly are generally provided. The method can comprise applying a colloidal fluid to a surface of a magnetic media, wherein the colloidal fluid comprises magnetic nanoparticles, a surfactant, a trigger salt, and a carrier medium; and assembling the magnetic nanoparticles into a pattern through a magnetic force arising from the surface of the magnetic media

Patterned Nanoparticle Assembly Methodology

Methods for forming a nanoparticle assembly are generally provided. The method can comprise applying a colloidal fluid to a surface of a magnetic media, wherein the colloidal fluid comprises magnetic nanoparticles, a surfactant, a trigger salt, and a carrier medium; and assembling the magnetic nanoparticles into a pattern through a magnetic force arising from the surface of the magnetic media

Telomeric expression sites are highly conserved in trypanosoma brucei

Subtelomeric regions are often under-represented in genome sequences of eukaryotes. One of the best known examples of the use of telomere proximity for adaptive purposes are the bloodstream expression sites (BESs) of the African trypanosome Trypanosoma brucei. To enhance our understanding of BES structure and function in host adaptation and immune evasion, the BES repertoire from the Lister 427 strain of T. brucei were independently tagged and sequenced. BESs are polymorphic in size and structure but reveal a surprisingly conserved architecture in the context of extensive recombination. Very small BESs do exist and many functioning BESs do not contain the full complement of expression site associated genes (ESAGs). The consequences of duplicated or missing ESAGs, including ESAG9, a newly named ESAG12, and additional variant surface glycoprotein genes (VSGs) were evaluated by functional assays after BESs were tagged with a drug-resistance gene. Phylogenetic analysis of constituent ESAG families suggests that BESs are sequence mosaics and that extensive recombination has shaped the evolution of the BES repertoire. This work opens important perspectives in understanding the molecular mechanisms of antigenic variation, a widely used strategy for immune evasion in pathogens, and telomere biology

Synthesis and characterization of Multi-dopant Ferrite Magnetic Nanoparticles with Designed Structures

Nonstoichiometric ferrite nanoparticles have drawn attention on the tunability of the magnetic properties by controlling the composition. We adopted the extended LaMer technique to synthesize multi-dopant ferrite nanoparticles with core-shell structure by controlling the pumping rate. The synthesis consists two steps: 1) synthesis of oleate precursors, and 2) continuous injection synthesis of particles. Cobalt oleate and nickel oleate were mixed separately with iron oleate in a volume ratio of 1:2, respectively, to give a cobalt ferrite precursor and nickel ferrite precursor solutions. The two precursor solutions were injected respectively with controlled pumping rate (Fig. 1), and cobalt ferrite/nickel ferrite core-gradient shell nanoparticles were then produced with continuous growth (Fig 2). Nanoparticles with same core size and shell thickness were made. Samples with low, medium, and high gradients were compared with a control with no gradient. TEM (Transmission Electron Microscopy) results showed a well-controlled size with a mean diameter of 10 nm and standard deviation of 1 nm. The elemental distribution throughout the particle was analyzed by EELS (Electron Energy Loss Spectroscopy) to confirm the existence of core-gradient shell structure. Physical properties, such as saturation magnetization, blocking temperature, and effective anisotropy were then measured and calculated based on VSM (Vibration Sampling Magnetometry) and ZFC-FC (Zero Field Cooling-Field Cooling) measurements

Construction of a corresponding empirical model to bridge thermal properties and synthesis of thermoresponsive poloxamines

The thermoresponsive properties of poloxamine (tetra-branch PEO-PPO block copolymer) hydrogels are related to several variables. Of particular interest to this study were the molecular weight of the polymer, the molar ratio between PEO and PPO blocks, and the concentration of the aqueous solution. Accurately controlling the thermoresponsive behaviors of the polymer is critical to the application of such materials; therefore, the structure–property relationship of tetra-branch PEO-PPO block copolymer was studied by synthesis via anionic ring-opening polymerization (AROP). The structure–property relationships were studied by measuring the thermoresponsive behavior via differential scanning calorimetry (DSC) and developing an empirical model which statistically fit the collected data. This empirical model was then used for designing poloxamines that have critical micellization temperatures (CMT) between room temperature and physiological temperature. The model was validated with three polymers that targeted a CMT of 308 K (35°C). The empirical model showed great success in guiding the synthesis of poloxamines showing a temperature difference of less than 3 K between the predicted and the observed CMTs. This study showed a great potential of using an empirical model to set synthesis parameters to control the properties of the polymer products

Quantitative Measurement of Ligand Exchange with Small-Molecule Ligands on Iron Oxide Nanoparticles via Radioanalytical Techniques

Ligand exchange on the surface of hydrophobic iron oxide nanoparticles is a common method for controlling surface chemistry for a desired application. Furthermore, ligand exchange with small-molecule ligands may be necessary to obtain particles with a specific size or functionality. Understanding to what extent ligand exchange occurs and what factors affect it is important for the optimization of this critical procedure. However, quantifying the amount of exchange may be difficult because of the limitations of commonly used characterization techniques. Therefore, we utilized a radiotracer technique to track the exchange of a radiolabeled ¹⁴C-oleic acid ligand with hydrophilic small-molecule ligands on the surface of iron oxide nanoparticles. Iron oxide nanoparticles functionalized with ¹⁴C-oleic acid were modified with small-molecule ligands with terminal functional groups including catechols, phosphonates, sulfonates, thiols, carboxylic acids, and silanes. These moieties were selected because they represent the most commonly used ligands for this procedure. The effectiveness of these molecules was compared using both procedures widely found in the literature and using a standardized procedure. After ligand exchange, the nanoparticles were analyzed using liquid scintillation counting (LSC) and inductively coupled plasma–mass spectrometry. The labeled and unlabeled particles were further characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS) to determine the particle size, hydrodynamic diameter, and zeta potential. The unlabeled particles were characterized via attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR) and vibrating sample magnetometry (VSM) to confirm the presence of the small molecules on the particles and verify the magnetic properties, respectively. Radioanalytical determination of ¹⁴C-oleic acid was used to calculate the total amount of oleic acid remaining on the surface of the particles after ligand exchange. The results revealed that the ligand-exchange reactions performed using widely cited procedures did not go to completion. Residual oleic acid remained on the particles after these reactions and the reactions using a standardized protocol. A comparison of the ligand-exchange procedures indicated that the binding moiety, multidenticity, reaction time, temperature, and presence of a catalyst impacted the extent of exchange. Quantification of the oleic acid remaining after ligand exchange revealed a binding hierarchy in which catechol-derived anchor groups displace the most oleic acid on the surface of the nanoparticles and the thiol group displaces the least amount of oleic acid. Thorough characterization of ligand exchange is required to develop nanoparticles suitable for their intended application

pH Triggered Recovery and Reuse of Thiolated Poly(acrylic acid) Functionalized Gold Nanoparticles with Applications in Colloidal Catalysis

Thiolated poly­(acrylic acid) (PAA-SH) functionalized gold nanoparticles were explored as a colloidal catalyst with potential application as a recoverable catalyst where the PAA provides pH-responsive dispersibility and phase transfer capability between aqueous and organic media. This system demonstrates complete nanoparticle recovery and redispersion over multiple reaction cycles without changes in nanoparticle morphology or reduction in conversion. The catalytic activity (rate constant) was reduced in subsequent reactions when recovery by aggregation was employed, despite unobservable changes in morphology or dispersibility. When colloidal catalyst recovery employed a pH induced phase transfer between two immiscible solvents, the catalytic activity of the recovered nanoparticles was unchanged over four cycles, maintaining the original rate constant and 100% conversion. The ability to recover and reuse colloidal catalysts by aggregation/redispersion and phase transfer methods that occur at low and high pH, respectively, could be used for different gold nanoparticle catalyzed reactions that occur at different pH conditions

Extended LaMer Synthesis of Cobalt Doped Ferrite

Nonstoichiometric cobalt ferrite nanoparticles have drawn interest in magnetically mediated energy delivery due to their high magnetocrystalline anisotropy and their high peak loss frequency. The use of an extended LaMer synthesis allows for size control of the doped particles up to a threshold core diameter of 18 nm. Above this diameter, particles become unstable and drop out of suspension, allowing for further nucleation events to occur. This leads to a cyclic nucleation, growth, and destabilization regime seen during the course of the reaction. Using the size control of the extended LaMer synthesis technique, we examine the specific absorption rate (SAR) as a function of particle size up to 18 nm and observe the same oscillatory behavior in the measured SAR values