Dynamic visualization of photothermal heating by gold nanocages using thermoresponsive elastin like polypeptides

Precision Loading and Delivery of Molecular Cargo by Size-Controlled Coacervation of Gold Nanoparticles Functionalized with Elastin-like Peptides

Thermoresponsive elastin-like peptides (ELPs) have been extensively investigated in biotechnology and medicine, but little attention has been paid to the process by which coacervation causes ELP-decorated particles to aggregate. Using gold nanoparticles (AuNPs) functionalized with a cysteine-terminated 96-repeat of the VPGVG sequence (V96-Cys), we show that the size of the clusters that reversibly form above the ELP transition temperature can be finely controlled in the 250 to 930 nm range by specifying the concentration of free V96-Cys in solution and using AuNPs of different sizes. We further find that the localized surface plasmon resonance peak of the embedded AuNPs progressively red-shifts with cluster size, likely due to an increase in particle-particle contacts. We exploit this fine control over size to homogeneously load precise amounts of the dye Nile Red and the antibiotic Tetracycline into clusters of different hydrodynamic diameters and deliver cargos near-quantitatively by deconstructing the aggregates below the ELP transition temperature. Beyond establishing a key role for free ELPs in the agglomeration of ELP-functionalized particles, our results provide a path for the thermally controlled delivery of precise quantities of molecular cargo. This capability might prove useful in combination photothermal therapies and theranostic applications, and to trigger spatially and temporally uniform responses from biological, electronic, or optical systems.

Versatile template-directed synthesis of gold nanocages with a predefined number of windows

Highly symmetrical gold nanocages can be produced with a controllable number of circular windows of either 2, 3, 4, 6 or 12 via an original fabrication route. The synthetic pathway includes three main stages: the synthesis of silica/polystyrene multipod templates, the regioselective seeded growth of a gold shell on the unmasked part of the silica surface and the development of gold nanocages by dissolving/etching the templates. Electron microscopy and tomography provide evidence of the symmetrical features of the as-obtained nanostructures. The optical properties of nanocages with 4 and 12 windows were measured at the single particle level by spatial modulation spectroscopy and correlated with numerical simulations based on finite-element modeling. The new multi-step synthesis approach reported here also allows the synthesis of rattle-like nanostructures through filling of the nanocages with a guest nano-object. With the potential to adjust the chemical composition, size and geometry of both the guest particle and the host cage, it opens new routes towards the fabrication of hollow nanostructures of high interest for a variety of applications including sensing devices, catalytic reactors and biomedicine.

A Gold Nanocage/Cluster Hybrid Structure for Whole-Body Multispectral Optoacoustic Tomography Imaging, EGFR Inhibitor Delivery, and Photothermal Therapy

Gold nanocages (AuNCs) and gold nanoclusters (AuClusters) are two classes of advantageous nanostructures with special optical properties, and many other attractive properties. Integrating them into one nanosystem may achieve greater and smarter performance. Herein, a hybrid gold nanostructure for fluorescent and optoacoustic tomography imaging, controlled release of drugs, and photothermal therapy (PTT) is demonstrated. For this nanodrug (EA-AB), an epidermal growth factor receptor (EGFR) inhibitor erlotinib (EB) is loaded into AuNCs, which are then capped and functionalized by biocompatible AuCluster@BSA (BSA = bovine serum albumin) conjugates via electrostatic interaction. Upon cell internalization, the lysosomal proteases and low pH cause the release of EB from EA-AB, and also induce fluorescence restoration of the AuCluster for imaging. Irradiation with near-infrared light further promotes the drug release and affords a PTT effect as well. The AuNC-based nanodrug is optoacoustically active, and its biodistribution and metabolic process have been successfully monitored by whole-body and 3D multispectral optoacoustic tomography imaging. Owing to the combined actions of PTT and EGFR pathway blockage, EA-AB exhibits marked tumor inhibition efficacy in vivo.

Short elastin-like peptide-functionalized gold nanoparticles that are temperature responsive under near-physiological conditions

Thermally-responsive, short elastin-like peptides (ELPs) of sequence VPGVG (V, P and G represent valine, proline and glycine respectively), bearing different N-terminal functional groups (amino-, N-acetyl and thiol) and a non-ionisable C-terminal group, were prepared by solid phase synthesis. The conformation and aggregation properties of the ELPs were studied in different pH aqueous buffer solutions using UV-vis spectroscopy and circular dichroism (CD). The thiol-capped ELPs were used to prepare functionalized gold nanoparticles (GNPs), which were found to undergo thermally-triggered reversible aggregation at 40 °C. The peptide conformation and nanoparticle aggregation behaviour of the ELP-GNPs in aqueous solution were investigated by transmission electron microscopy (TEM), circular dichroism (CD) and UV-vis spectroscopy. It was found that the ELP-GNP conjugates were capable of reversible, thermally triggered aggregation at near-physiological temperatures (transition temperature of 40 °C at pH = 7.4), opening up applications in photothermal cancer therapy and diagnosis.

Plasmono-magnetic material for precise photothermal heating

Noble metal nanoparticles have been extensively studied as photo-sensitive agents for photothermal cancer therapy. Precise control over the size and shape of the nanoparticles allowed strong optical absorption and efficient heat generation necessary for destroying a tumor to be achieved. However, one of the fundamental challenges of application of the nanoparticles towards photothermal cancer therapy is low specificity in the targeting tumor tissue in comparison with the healthy tissue and the resulting unfavorable biodistribution of the nanoparticles. Additional levels of control over particle distribution can be achieved by making the particles magnetic and using external magnets to control their accumulation in a tumor. Since the direct synthesis of particles with a magnetic core and a metallic shell limits the options for design and fine-tuning of plasmonic properties, the alternative approaches to the design of such materials have to be investigated. Here we propose and demonstrate a new design of a hybrid plasmono-magnetic material for photothermal heating created by grafting Au nanocages onto a surface of magnetic micro-beads. Next, we confirm its dual functionality in in vitro studies and show that individual hybrid particles can be magnetically controlled with a precision of a few micrometers and precisely destroy individual cells using plasmonic heating.

We demonstrated a new hybrid plasmono-magnetic material for photothermal heating created by grafting Au nanocages onto a surface of magnetic micro-beads.

Mobile phone based ELISA (MELISA)

Enzyme-linked immunosorbent assay (ELISA) is one of the most important technologies for biochemical analysis critical for diagnosis and monitoring of many diseases. Traditional systems for ELISA incubation and reading are expensive and bulky, thus cannot be used at point-of-care or in the field. Here, we propose and demonstrate a new miniature mobile phone based system for ELISA (MELISA). This system can be used to complete all steps of the assay, including incubation and reading. It weighs just 1 pound, can be fabricated at low cost, portable, and can transfer test results via mobile phone. We successfully demonstrated how MELISA can be calibrated for accurate measurements of progesterone and demonstrated successful measurements with the calibrated system.

Design and Fabrication of Temperature-Sensitive Nanogels with Controlled Drug Release Properties for Enhanced Photothermal Sterilization

For better removal of excessive free radicals and harmful bacteria from the human body, the development of synergistic antioxidant and antibacterial agents is urgently required. Herein, we designed novel temperature-sensitive, curcumin (Cur)-loaded nanogels for the application of scavenging reactive oxygen species and killing pathogenic bacteria. Photothermal sterilization, different from traditional antibiotics, is a promising and effective treatment for pathogenic bacterial infection. The nanogels were fabricated by using poly(N-isopropylacrylamide) (a temperature-sensitive hydrogel) to encapsulate poly(3,4-ethylenedioxythiophene) nanoparticles (photothermal agents) and Cur through a reformative precipitation polymerization. When triggered by near-IR light, the Cur-loaded nanogels exhibited high (56.8 %), and excellent temperature-sensitive effects. Moreover, the light-induced temperature increase can also weaken the interaction between the networks of PNIPAAm and Cur, to show excellent antioxidant and antibacterial performance (90 % cell death) of the nanogels.