3D Printing of Composite Radiation Shielding for Broad Spectrum Protection of Electronic Systems.

The miniaturization of satellite systems has compounded the need to protect microelectronic components from damaging radiation. Current approaches to mitigate this damage, such as indiscriminate mass shielding, built-in redundancies, and radiation hardened electronics, introduce high size, weight, power, and cost penalties that impact the overall performance of the satellite or launch opportunities. Additive manufacturing provides an appealing strategy to deposit radiation shielding only on susceptible components within an electronic assembly. Here, we describe a versatile material platform and process to conformally print customized composite inks at room temperatures directly and selectively onto commercial-off-the-shelf electronics. The suite of inks uses a flexible styrene-isoprene-styrene block copolymer binder that can be filled with particles of varying atomic densities for varying radiation shielding capabilities. Additionally, the system readily allows blended composites that contain multiple particle species with varying atomic composition within the same structure. The method can produce graded shielding that offers improved radiation attenuation via exquisite control over both shield geometry and composition. We anticipate this alternative to traditional shielding methods will enable the rapid proliferation of the next generation of compact satellite designs. This article is protected by copyright. All rights reserved.

Additive Manufacturing of Multimaterial Composites for Radiation Shielding and Thermal Management.

The harsh radiation environment of space induces the degradation and malfunctioning of electronic systems. Current approaches for protecting these microelectronic devices are generally limited to attenuating a single type of radiation or require only selecting components that have undergone the intensive and expensive process to be radiation-hardened by design. Herein, we describe an alternative fabrication strategy to manufacture multimaterial radiation shielding via direct ink writing of custom tungsten and boron nitride composites. The additively manufactured shields were shown to be capable of attenuating multiple species of radiation by tailoring the composition and architecture of the printed composite materials. The shear-induced alignment during the printing process of the anisotropic boron nitride flakes provided a facile method for introducing favorable thermal management characteristics to the shields. This generalized method offers a promising approach for protecting commercially available microelectronic systems from radiation damage and we anticipate this will vastly enhance the capabilities of future satellites and space systems.

Dielectric and Mechanical Properties of 3D Printed Nanocomposites with Varied Particle Diameter.

3D printed nanocomposites provide a method for generating high-performance radio frequency devices. Limited work has been done to investigate the influence the nanoparticle diameter has on the performance of 3D printable nanocomposites. We describe here the development of a family of 3D printable nanocomposite inks formulated from nanoparticles with diameters ranging from 30 to 300 nm. Relative permittivity values for the printed nanocomposites were unaffected by nanoparticle diameter whereas loss tangent, glass transition temperature, and elastic modulus were altered. This work provides a framework for designing 3D printable nanocomposites and highlights the importance that nanoparticle diameter plays in formulation strategy.

Solubilization of Hydrophobic Catalysts Using Nanoparticle Hosts.

A modular strategy for the solubilization and protection of hydrophobic transition metal catalysts using the hydrophobic pockets of water soluble gold nanoparticles is reported. Besides preserving original catalyst activity, this encapsulation strategy provides a protective environment for the hydrophobic catalyst and brings reusability. This system provides a versatile platform for the encapsulation of different hydrophobic transition metal catalysts, allowing a wide range of catalysis in water while uniting the advantages of homogeneous and heterogeneous catalysis in the same system.

Holographic aperture ladar with range compression.

Simultaneous range compression and aperture synthesis is experimentally demonstrated with a stepped linear frequency modulated waveform and holographic aperture ladar. The resultant three-dimensional (3D) data has high resolution in the aperture synthesis dimension and is recorded using a conventional low bandwidth focal plane array. Individual cross-range field segments are coherently combined using data driven registration and phase correction methods allowing range compression to be performed without the benefit of a coherent waveform. Furthermore, we demonstrate a synergistically enhanced ability to discriminate image objects due to the coaction of range compression and aperture synthesis. We show that two objects can be precisely located in 3D space, despite being unresolved in two directions, due to resolution gains in both the range and azimuth cross-range dimensions.

Sensing by Smell: Nanoparticle-Enzyme Sensors for Rapid and Sensitive Detection of Bacteria with Olfactory Output.

We present here a highly efficient sensor for bacteria that provides an olfactory output, allowing detection without the use of instrumentation and with a modality that does not require visual identification. The sensor platform uses nanoparticles to reversibly complex and inhibits lipase. These complexes are disrupted in the presence of bacteria, restoring enzyme activity and generating scent from odorless pro-fragrance substrate molecules. This system provides rapid (15 min) sensing and very high sensitivity (102 cfu/mL) detection of bacteria using the human sense of smell as an output.

Enhanced Laser Desorption/Ionization Mass Spectrometric Detection of Biomolecules Using Gold Nanoparticles, Matrix, and the Coffee Ring Effect.

Nanomaterials have been extensively used as alternate matrices to minimize the low molecular weight interferences observed in typical MALDI but such nanomaterials typically do not improve the spot-to-spot variability that is commonly seen. In this work, we demonstrate that nanoparticles and low matrix concentrations (<2.5 mg/mL) can be used to homogeneously concentrate analytes into a narrow ring by taking advantage of the "coffee ring" effect. Concentration of the samples in this way leads to enhanced signals when compared to conventional MALDI, with higher m/z analytes being enhanced to the greatest extent. Moreover, the ionization suppression often observed in samples with high salt concentrations can be overcome by preparing samples in this way. The ring that is formed is readily visible, allowing the laser to be focused only on spots that contain analyte. The coffee-ring effect represents a new mode by which nanomaterials can be used to enhance the MALDI-based detection of biomolecules.

Gradient and Patterned Protein Films Stabilized via Nanoimprint Lithography for Engineered Interactions with Cells.

Protein-based biomaterials provide versatile scaffolds for generating functional surfaces for biomedical applications. However, tailoring the functional and biological properties of protein films remains a challenge. Here, we describe a high-throughput method to designing stable, functional biomaterials by combining inkjet deposition of protein inks with a nanoimprint lithography based methodology. The translation of the intrinsically charged proteins into functional materials properties was demonstrated through controlled cellular adhesion. This modular strategy offers a rapid method to produce customizable biomaterials.

Phase gradient algorithm method for three-dimensional holographic ladar imaging.

Three-dimensional (3D) holographic ladar uses digital holography with frequency diversity to add the ability to resolve targets in range. A key challenge is that since individual frequency samples are not recorded simultaneously, differential phase aberrations may exist between them, making it difficult to achieve range compression. We describe steps specific to this modality so that phase gradient algorithms (PGA) can be applied to 3D holographic ladar data for phase corrections across multiple temporal frequency samples. Substantial improvement of range compression is demonstrated with a laboratory experiment where our modified PGA technique is applied. Additionally, the PGA estimator is demonstrated to be efficient for this application, and the maximum entropy saturation behavior of the estimator is analytically described.

Nanoparticle-dendrimer hybrid nanocapsules for therapeutic delivery.

BACKGROUND: Nanocapsules can efficiently encapsulate therapeutic cargo for anticancer drug delivery. However, the controlled release of the payload remains a challenge for effective drug delivery. MATERIALS & METHODS: We used dithiocarbamate-functionalized PAMAM dendrimer to cross-link the shell of arginine gold nanoparticles stabilized nanocapsule, and controlled the drug release from the nanocapsule. The ability of cross-linked nanocapsule to deliver hydrophobic paclitaxel to B16F10 cells was demonstrated both in vitro and in vivo. RESULTS: Cross-linked nanocapsule possesses tunable stability and modular permeability, and can deliver paclitaxel with improved anticancer efficiency compared with free drug both in vitro and in vivo. CONCLUSION: Dithiocarbamate chemistry provides a new tool to harness multifactorial colloidal self-assembly for controlled drug delivery for cancer therapy.

Biocidal and Antifouling Chlorinated Protein Films.

Bacteria attach to the surfaces of medical devices and implants, resulting in life-threatening infections. Nonfouling coatings can be used to prevent adhesion of bacteria on the surface, while biocidal coatings kill the microbes. Combining nonfouling and biocidal properties can yield highly effective antimicrobial coatings. We demonstrate here a nanoimprint lithography (NIL)-based method to generate antibacterial coatings that both resist bacterial attachment and kill bacteria. In this strategy nanoimprint lithography was used to create water-stable films of bovine serum albumin (BSA) that are nonadhesive toward bacteria because of their negative/zwitterionic surface potential. Biocidal activity was then imparted through chlorination of cysteine sulfurs, providing slow release of chlorine and potent antimicrobial activity against pathogenic bacteria.

Immunomodulatory effects of coated gold nanoparticles in LPS-stimulated in vitro and in vivo murine model systems.

The ability of nanoparticle surface functionalities to regulate immune responses during an immunological challenge (i. e. inflammation) would open new doors for their use in non-prophylactic therapeutics. We report here the use of functionalized 2 nm core gold nanoparticles to control the immunological responses of in vitro and in vivo systems presented with an inflammatory challenge. The results showed that NPs bearing a hydrophobic zwitterionic functionality boost inflammatory outcomes while hydrophilic zwitterionic NPs generate minimal immunological responses. Surprisingly, tetra(ethylene glycol) headgroups generate a significant anti-inflammatory response both in vitro and in vivo. These results demonstrate the ability of simple surface ligands to provide immunomodulatory properties, making them promising leads for the therapeutic usage of nanomaterials in diseases involving inflammation.

Enhanced Laser Desorption/Ionization Mass Spectrometric Detection of Gold Nanoparticles in Biological Samples Using the Synergy between Added Matrix and the Gold Core.

Laser desorption/ionization mass spectrometry (LDI-MS) has been used to detect gold nanoparticles (AuNPs) in biological samples, such as cells and tissues, by ionizing their attached monolayer ligands. Many NP-attached ligands, however, are difficult to ionize by LDI, making it impossible to track these NPs in biological samples. In this work, we demonstrate that concentrations of matrix-assisted LDI (MALDI) matrices an order of magnitude below the values typically used in MALDI can facilitate the selective detection of AuNPs with these ligands, even in samples as complex as cell lysate. This enhanced sensitivity arises from a synergistic relationship between the gold core and the matrix that helps to selectively ionize ligands attached to the AuNPs.

The Interplay of Size and Surface Functionality on the Cellular Uptake of Sub-10 nm Gold Nanoparticles.

Correlation of the surface physicochemical properties of nanoparticles with their interactions with biosystems provides key foundational data for nanomedicine. We report here the systematic synthesis of 2, 4, and 6 nm core gold nanoparticles (AuNP) featuring neutral (zwitterionic), anionic, and cationic headgroups. The cellular internalization of these AuNPs was quantified, providing a parametric evaluation of charge and size effects. Contrasting behavior was observed with these systems: with zwitterionic and anionic particles, uptake decreased with increasing AuNP size, whereas with cationic particles, uptake increased with increasing particle size. Through mechanistic studies of the uptake process, we can attribute these opposing trends to a surface-dictated shift in uptake pathways. Zwitterionic NPs are primarily internalized through passive diffusion, while the internalization of cationic and anionic NPs is dominated by multiple endocytic pathways. Our study demonstrates that size and surface charge interact in an interrelated fashion to modulate nanoparticle uptake into cells, providing an engineering tool for designing nanomaterials for specific biological applications.

Fabrication of Robust Protein Films Using Nanoimprint Lithography.

A nanoimprint-lithography-based fabrication method to generate stable protein films is described. The process is environmentally friendly and generalizable with respect to the protein building blocks. These non-fouling surfaces are readily patternable, incorporate intrinsic protein charge into the film, and able to control cellular adhesion.

A Multichannel Biosensor for Rapid Determination of Cell Surface Glycomic Signatures.

Cell surface glycosylation serves a fundamental role in dictating cell and tissue behavior. Cell surface glycomes differ significantly, presenting viable biomarkers for identifying cell types and their states. Glycoprofiling is a challenging task, however, due to the complexity of the constituent glycans. We report here a rapid and effective sensor for surface-based cell differentiation that uses a three-channel sensor produced by noncovalent conjugation of a functionalized gold nanoparticle (AuNP) and fluorescent proteins. Wild-type and glycomutant mammalian cells were effectively stratified using fluorescence signatures obtained from a single sensor element. Blinded unknowns generated from the tested cell types were identified with high accuracy (44 out of 48 samples), validating the robustness of the multichannel sensor. Notably, this selectivity-based high-throughput sensor differentiated between cells, employing a nondestructive protocol that required only a single well of a microplate for detection.

Bacteriophage-based nanoprobes for rapid bacteria separation.

The lack of practical methods for bacterial separation remains a hindrance for the low-cost and successful development of rapid detection methods from complex samples. Antibody-tagged magnetic particles are commonly used to pull analytes from a liquid sample. While this method is well-established, improvements in capture efficiencies would result in an increase of the overall detection assay performance. Bacteriophages represent a low-cost and more consistent biorecognition element as compared to antibodies. We have developed nanoscale bacteriophage-tagged magnetic probes, where T7 bacteriophages were bound to magnetic nanoparticles. The nanoprobe allowed the specific recognition and attachment to E. coli cells. The phage magnetic nanprobes were directly compared to antibody-conjugated magnetic nanoprobes. The capture efficiencies of bacteriophages and antibodies on nanoparticles for the separation of E. coli K12 at varying concentrations were determined. The results indicated a similar bacteria capture efficiency between the two nanoprobes.

Inkjet-printed gold nanoparticle surfaces for the detection of low molecular weight biomolecules by laser desorption/ionization mass spectrometry.

Effective detection of low molecular weight compounds in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is often hindered by matrix interferences in the low m/z region of the mass spectrum. Here, we show that monolayer-protected gold nanoparticles (AuNPs) can serve as alternate matrices for the very sensitive detection of low molecular weight compounds such as amino acids. Amino acids can be detected at low fmol levels with minimal interferences by properly choosing the AuNP deposition method, density, size, and monolayer surface chemistry. By inkjet-printing AuNPs at various densities, we find that AuNP clusters are essential for obtaining the greatest sensitivity. Graphical Abstract ᅟ.

Nanoparticle-Stabilized Capsules for the Treatment of Bacterial Biofilms.

Bacterial biofilms are widely associated with persistent infections. High resistance to conventional antibiotics and prevalent virulence makes eliminating these bacterial communities challenging therapeutic targets. We describe here the fabrication of a nanoparticle-stabilized capsule with a multicomponent core for the treatment of biofilms. The peppermint oil and cinnamaldehyde combination that comprises the core of the capsules act as potent antimicrobial agents. An in situ reaction at the oil/water interface between the nanoparticles and cinnamaldehyde structurally augments the capsules to efficiently deliver the essential oil payloads, effectively eradicating biofilms of clinically isolated pathogenic bacteria strains. In contrast to their antimicrobial action, the capsules selectively promoted fibroblast proliferation in a mixed bacteria/mammalian cell system making them promising for wound healing applications.

Supramolecular regulation of bioorthogonal catalysis in cells using nanoparticle-embedded transition metal catalysts.

Bioorthogonal catalysis broadens the functional possibilities of intracellular chemistry. Effective delivery and regulation of synthetic catalytic systems in cells are challenging due to the complex intracellular environment and catalyst instability. Here, we report the fabrication of protein-sized bioorthogonal nanozymes through the encapsulation of hydrophobic transition metal catalysts into the monolayer of water-soluble gold nanoparticles. The activity of these catalysts can be reversibly controlled by binding a supramolecular cucurbit[7]uril 'gate-keeper' onto the monolayer surface, providing a biomimetic control mechanism that mimics the allosteric regulation of enzymes. The potential of this gated nanozyme for use in imaging and therapeutic applications was demonstrated through triggered cleavage of allylcarbamates for pro-fluorophore activation and propargyl groups for prodrug activation inside living cells.