Brylee David B. Tiu

High-Strength Stereolithographic 3D Printed Nanocomposites: Graphene Oxide Metastability

The weak thermomechanical properties of commercial 3D printing plastics have limited the technologys application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 and 100 °C for 12 h. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1 wt % GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, which is seen to this degree in 3D-printed samples reported in literature, is attributed to the metastable structure of GO, polymer-nanofiller cross-linking via acid-catalyzed esterification, and removal of intercalated water, thus improving filler-matrix interaction as evidenced by spectroscopy and microscopy analyses.

Plasmonics and templated systems for bioapplications

The science of surface plasmons in noble metal nanoparticles and in thin metal film–glass interfaces is driving most innovations in biochemical and biomedical applications. The sensitivity of these charge density oscillations toward changes in the geometry and the surrounding medium is more than capable in detecting antibody–antigen and molecular interactions, diagnosing an array of diseases, and delivering drugs in the form of an absorption peak in the visible to the near-infrared region. Modifications on the physical parameters and functionalities on the surface can be used to control the position of the maximum localized surface plasmon resonance absorbance peak or the minimum bulk SPR reflectivity dip. Several lithographic techniques such as colloidal templating can now produce binary and tertiary patterns with more controlled SPR peaks. On the other hand, the surfaces of plasmonic materials should also be properly functionalized in order to selectively recognize specific analytes. Hence, the flexible low-cost synthesis of artificial antibodies complements the surface plasmon properties of metallic nanomaterials. Continuous progress in these fields should make low-cost and responsive biosensors available for point-of-care applications and personal diagnostics.

Conducting polymer-gold co-patterned surfaces via nanosphere lithography

HYPOTHESIS Co-patterned arrays comprised of conjugated polymers and nanostructured gold is an important matrix for sensing and stimuli-responsive plasmonic applications. Nanosphere lithography (NSL) is an easy-to-use patterning technique and viable method to fabricate inverse honeycomb structures with electrochemically deposited conjugated polymers. The cross-sectional height of the conducting polymer pattern can be tuned such that the macropores of the honeycomb structure expose electrochemically accessible areas for further gold deposition. Using time-dependent electrochemical reduction, Au(3+) is reduced to Au(0) and selectively deposit on the macropores thus forming a co-patterned surface. EXPERIMENTS The Langmuir-Blodgett-like deposition was used to assemble polystyrene spheres on a conductive substrate. Then the carbazole-based monomer was electropolymerized within the interstices of the colloidal template, which was subsequently dissolved. A potentiostatic technique was used to deposit Au in the macropores. FINDINGS Fabrication of the polycarbazole-Au co-patterned surface was characterized by atomic force microscopy (AFM), electrochemical quartz crystal microbalance (EC-QCM), and X-ray photoelectron spectroscopy (XPS). Surface plasmon resonance spectroscopy (SPS) data supported backfilling behavior and quantified the complex refractive index of the array. UV-Vis absorption spectroscopy shows overlapping polycarbazole and gold LSPR peaks useful for plasmonic sensing applications. The colloidal templating approach reported in this study was further used in the fabrication of highly ordered Au nanodisks.

Production of Immunoabsorbent Nanoparticles by Displaying Single-Domain Protein A on Potato Virus X

The combination of antibodies with nanoparticles provides wide-ranging applications in biosensing. While several covalent presentation strategies have been established, there is need for alternative, non-covalent methods to provide a routine for scalable nanomanufacturing. We report the multivalent presentation of the B domain of Staphylococcus aureus protein A (SpAB) on potato virus X (PVX) nanoparticles. Three different synthetic strategies were used to obtain chimeric PVX(SpAB) filaments. The protein A fragments displayed on the surface of all three PVX chimeras remained fully functional as an immunoabsorbent for antibody capture enabling biosensing. The new biomaterials presented could find applications as diagnostic tools for biomedical or environmental monitoring.

Free-Standing, Nanopatterned Janus Membranes of Conducting Polymer–Virus Nanoparticle Arrays

Nanostructured mesoscale materials find wide-ranging applications in medicine and energy. Top-down manufacturing schemes are limited by the smallest dimension accessible; therefore, we set out to study a bottom-up approach mimicking biological systems, which self-assemble into systems that orchestrate complex energy conversion functionalities. Inspired by nature, we turned toward protein-based nanoparticle structures formed by plant viruses, specifically the cowpea mosaic virus (CPMV). We report the formation of hierarchical CPMV nanoparticle assemblies on colloidal-patterned, conducting polymer arrays using a protocol combining colloidal lithography, electrochemical polymerization, and electrostatic adsorption. In this approach, a hexagonally close-packed array of polystyrene microspheres was assembled on a conductive electrode to function as the sacrificial colloidal template. A thin layer of conducting polypyrrole material was electrodeposited within the interstices of the colloidal microspheres and monitored in situ using electrochemical quartz crystal microbalance with dissipation (EC-QCM-D). Etching the template revealed an inverse opaline conducting polymer pattern capable of forming strong electrostatic interactions with CPMV and therefore enabling immobilization of CPMV on the surface. The CPMV-polymer films were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Furthermore, molecular probe diffusion experiments revealed selective ion transport properties as a function of the presence of the CPMV nanoparticles on the surface. Lastly, by utilizing its electromechanical behavior, the polymer/protein membrane was electrochemically released as a free-standing film, which can potentially be used for developing high surface area cargo delivery systems, stimuli-responsive plasmonic devices, and chemical and biological sensors.

Solvatochromic, thermochromic and pH-sensory DCDHF-hydrazone molecular switch: response to alkaline analytes

Multi-stimuli responsive DCDHF-hydrazone molecular switch containing a hydrazone recognition moiety is developed for the naked-eye detection of alkaline analytes in both vapour and aqueous media. Mechanisms accounting for the thermochromism, pH-sensitivity and solvatochromism are proposed. DCDHF-hydrazone chromophores of different substituents introduced nanostructures with different morphologies via a re-precipitation technique. The films formulated from these nanostructures function as solid-state vapochromic sensors for probing alkaline vapours such as amines and ammonia. The sensing performance is reversible and has differential sensitivity towards a variety of amines at comparable concentrations. The structure of the hydrazone molecular switch was established spectroscopically and by single crystal X-ray crystallography.

Slow-Release Formulation of Cowpea Mosaic Virus for In Situ Vaccine Delivery to Treat Ovarian Cancer

Abstract The plant viral nanoparticle cowpea mosaic virus (CPMV) is shown to be an effective immunotherapy for ovarian cancer when administered as in situ vaccine weekly, directly into the intraperitoneal (IP) space in mice with disseminated tumors. While the antitumor efficacy is promising, the required frequency of administration may pose challenges for clinical implementation. To overcome this, a slow release formulation is developed. CPMV and polyamidoamine generation 4 dendrimer form aggregates (CPMV‐G4) based on electrostatic interactions and as a function of salt concentration, allowing for tailoring of aggregate size and release of CPMV. The antitumor efficacy of a single administration of CPMV‐G4 is compared to weekly administration of soluble CPMV in a mouse model of peritoneal ovarian cancer and found to be as effective at reducing disease burden as more frequent administrations of soluble CPMV; a single injection of soluble CPMV, does not significantly slow cancer development. The ability of CPMV‐G4 to control tumor growth following a single injection is likely due to the continued presence of CPMV in the IP space leading to prolonged immune stimulation. This enhanced retention of CPMV and its antitumor efficacy demonstrates the potential for viral–dendrimer hybrids to be used for delayed release applications.

Photon Management through Virus-Programmed Supramolecular Arrays

Photon extraction and capture efficiency is a complex function of the materials composition, its molecular structure at the nanoscale, and the overall organization spanning multiple length scales. The architecture of the material defines the performance; nanostructured features within the materials enhance the energy efficiency. Photon capturing materials are largely produced through lithographic, top‐down, manufacturing schemes; however, there are limits to the smallest dimension achievable using this technology. To overcome these technological barriers, a bottom‐up nanomanufacturing is pursued. Inspired by the self‐programmed assembly of virus arrays in host cells resulting in iridescence of infected organisms, virus‐programmed, nanostructured arrays are studied to pave the way for new design principles in photon management and biology‐inspired materials science. Using the nanoparticles formed by plant viruses in combination with charged polymers (dendrimers), a bottom‐up approach is illustrated to prepare a family of broadband, low‐angular dependent antireflection mesoscale layered materials for potential application as photon management coatings. Measurement and theory demonstrate antireflectance and phototrapping properties of the virus‐programmed assembly. This opens up new bioengineering principles for the nanomanufacture of coatings and films for use in LED lighting and photovoltaics.

Nanomanufacture of free-standing, porous, janus-type films of polymer–plant virus nanoparticle arrays

We present a facile method for preparing hierarchical assemblies of cowpea mosaic virus (CPMV) nanoparticles adsorbed onto patterned polypyrrole copolymer arrays, which can be released as a freely standing and microporous polymer-protein membrane with a Janus-type structure. The patterning protocol is based on colloidal sphere lithography wherein a sacrificial honeycomb pattern composed of colloidal polystyrene (PS) microspheres is assembled on an electrode. A thin layer of polypyrrole film is electropolymerized within the interstices of the template and monitored using an electrochemical quartz crystal microbalance with dissipation (EC-QCM-D) and microscopy. Dissolving the PS template reveals an inverse opaline pattern capable of electrostatically capturing the CPMV particles. Through an electrochemical trigger, the polypyrrole-CPMV delaminates from the surface producing a self-sustaining polymer-protein membrane that can potentially be used for sensing and nanocargo applications.