The synthesis of well-defined nanoparticle materials has been an area of intense investigation, but size control in nanoparticle syntheses is largely empirical. Here, we introduce a general method for fine size control in the synthesis of nanoparticles by establishing steady state growth conditions through the continuous, controlled addition of precursor, leading to a uniform rate of particle growth. This approach, which we term the "Extended LaMer Mechanism" allows for reproducibility in particle size from batch to batch, as well as the ability to predict nanoparticle size by monitoring the early stages of growth. We have demonstrated this method by applying it to a challenging synthetic system: magnetite nanoparticles. To facilitate this reaction, we have developed a reproducible method for synthesizing an iron oleate precursor that can be used without purification. We then show how such fine size control affects the performance of magnetite nanoparticles in magnetic hyperthermia.

Silver nanoplates are introduced as a new photoacoustic contrast agent that can be easily functionalized for molecular photoacoustic imaging in vivo. Methods are described for synthesis, functionalization, and stabilization of silver nanoplates using biocompatible (“green”) reagents. Directional antibody conjugation to the nanoplate surface is presented along with proof of molecular sensitivity in vitro with pancreatic cancer cells. Cell viability tests show the antibody-conjugated silver nanoplates to be nontoxic at concentrations up to 1 mg/ml. Furthermore, the silver nanoplates' potential for in vivo application as a molecularly sensitive photoacoustic contrast agent is demonstrated using an orthotopic mouse model of pancreatic cancer. Results of these studies suggest that the synthesized silver nanoplates are well suited for a host of biomedical imaging and sensing applications.

Magnetic Particle Imaging (MPI) is a promising new tracer modality with zero attenuation in tissue, high contrast and sensitivity, and an excellent safety profile. However, the spatial resolution of MPI is currently around 1 mm in small animal scanners. Especially considering tradeoffs when scaling up MPI scanning systems to human size, this resolution needs to be improved for clinical applications such as angiography and brain perfusion. One method to improve spatial resolution is to increase the magnetic core size of the superparamagnetic nanoparticle tracers. The Langevin model of superparamagnetism predicts a cubic improvement of spatial resolution with magnetic core diameter. However, prior work has shown that the finite temporal response, or magnetic relaxation, of the tracer increases with magnetic core diameter and eventually leads to blurring in the MPI image. Here we perform the first wide ranging study of 5 core sizes between 18–32 nm with experimental quantification of the spatial resolution of each. Our results show that increasing magnetic relaxation with core size eventually opposes the expected Langevin behavior, causing spatial resolution to stop improving after 25 nm. Different MPI excitation strategies were experimentally investigated to mitigate the effect of magnetic relaxation. The results show that magnetic relaxation could not be fully mitigated for the larger core sizes and the cubic resolution improvement predicted by the Langevin was not achieved. This suggests that magnetic relaxation is a significant and unsolved barrier to achieving the high spatial resolutions predicted by the Langevin model for large core size SPIOs.

This article describes the three-dimensional self-assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers. For layers in which the NPs are more free to rotate, the easy axis of the NP can readily orient along the field direction. In more dense packing, free rotation of the NPs is hampered, and the NP ensembles likely build up quasi-domain states to minimize energy, which leads to lower magnetization in those layers. Detailed analysis of polarized neutron reflectometry data together with model calculations of the arrangement of the NPs within the layers and input from small-angle scattering measurements provide full characterization of the core/shell NP dimensions, degree of chaining, arrangement of the NPs within the different layers, and magnetization depth profile.

Background: Here we describe superparamagnetic relaxometry (SPMR), a technology that utilizes highly sensitive magnetic sensors and superparamagnetic nanoparticles for cancer detection. Using SPMR, we sensitively and specifically detect nanoparticles conjugated to biomarkers for various types of cancer. SPMR offers high contrast in vivo, as there is no superparamagnetic background, and bones and tissue are transparent to the magnetic fields. Methods: In SPMR measurements, a brief magnetizing pulse is used to align superparamagnetic nanoparticles of a discrete size. Following the pulse, an array of superconducting quantum interference detectors (SQUID) sensors detect the decaying magnetization field. NP size is chosen so that, when bound, the induced field decays in seconds. They are functionalized with specific biomarkers and incubated with cancer cells in vitro to determine specificity and cell binding. For in vivo experiments, functionalized

Miniature ultrasonic lysis for biological sample preparation is a promising technique for efficient and rapid extraction of nucleic acids and proteins from a wide variety of biological sources. Acoustic methods achieve rapid, unbiased, and efficacious disruption of cellular membranes while avoiding the use of harsh chemicals and enzymes, which interfere with detection assays. In this work, a miniature acoustic nucleic acid extraction system is presented. Using a miniature bulk acoustic wave (BAW) transducer array based on 36° Y-cut lithium niobate, acoustic waves were coupled into disposable laminate-based microfluidic cartridges. To verify the lysing effectiveness, the amount of liberated ATP and the cell viability were measured and compared to untreated samples. The relationship between input power, energy dose, flow-rate, and lysing efficiency were determined. DNA was purified on-chip using three approaches implemented in the cartridges: a silica-based sol-gel silica-bead filled microchannel, nucleic acid binding magnetic beads, and Nafion-coated electrodes. Using E. coli, the lysing dose defined as ATP released per joule was 2.2× greater, releasing 6.1× more ATP for the miniature BAW array compared to a bench-top acoustic lysis system. An electric field-based nucleic acid purification approach using Nafion films yielded an extraction efficiency of 69.2% in 10 min for 50 µL samples.

We have developed a miniature ultrasonic lysing system for the rapid release and extraction of Mycobacterium Tuberculosis (MTB) DNA. The prototype consists of two key sections, a disposable plastic manifold that hold sputum slides and a plastic cartridge with five fluidic DNA extraction channels. The MTB vaccine Bacillus Calmette-Guérin (BCG) was used as a simulant for MTB for all the lysing studies. The slide manifold houses up to five individual sputum slides and is processed by a computer to fill and load the cartridges with sputum suspensions from each slide. The plastic cartridge was developed to facilitate acoustic coupling through the bottom interface such that MTB/BCG can be lysed remotely. The disposable cartridge eliminated cross contamination problems and additional cleaning time. Due to the high power density, only 66 mW was required to lyse microliter BCG samples at the same level as the positive control (i.e. boiling for 30 minutes at 95 °C).

Charge-separated metal-organic frameworks (MOFs)a re au nique class of MOFs that can possess added properties originating from the exposed ionic species. A new charge-separated MOF,n amely,U NM-6 synthesized from atetrahedral borate ligand and Co 2 + cation is reported herein. UNM-6c rystalizes into the highly symmetric P43n space group with fourfold interpenetration, despite the stoichiometrici mbalance between the Ba nd Co atoms,w hich also leads to loosely bound NO 3 À anions within the crystal structure. These NO 3 À ions can be quantitatively exchangedw ith various other anions, leadingt o Lewis acid (Co 2 +)a nd Lewis base (anions) pairs within the pores and potentially cooperative catalytic activities.F or example, UNM-6-Br,t he MOF after anion exchange with Br À anions, displays high catalytic activity and stability in reactions of CO 2 chemical fixation into cyclic carbonates. The field of metal-organic framework (MOF) has expanded at an incredible rate with constantly emerging new MOF structures possessing tailor-designed surface areas and functionalities, pore sizes and shapes,a nd pore volumes for am yriado f promisinga pplications. [1-9] The majority of existing MOFs con