Induced hyperthermia has been demonstrated as an effective oncological treatment due to the reduced heat tolerance of most malignant tissues; however, most techniques for heat generation within a target volume are insufficiently selective, inducing heating and unintended damage to surrounding healthy tissues. Plasmonic photothermal therapy (PPTT) utilizes light in the near-infrared (NIR) region to induce highly localized heating in gold nanoparticles, acting as exogenous chromophores, while minimizing heat generation in nearby tissues. However, optimization of treatment parameters requires extensive in vitro and in vivo studies for each new type of pathology and tissue targeted for treatment, a process that can be substantially reduced by implementing computational modeling. Herein, we describe the development of an innovative model based on the finite element method (FEM) that unites photothermal heating physics at the nanoscale with the micron scale to predict the heat generation of both single and arrays of gold nanoparticles. Plasmonic heating from laser illumination is computed for gold nanoparticles with three different morphologies: nanobipyramids, nanorods, and nanospheres. Model predictions based on laser illumination of nanorods at a visible wavelength (655 nm) are validated through experiments, which demonstrate a temperature increase of 5 °C in the viscinity of the nanorod array when illuminated by a 150 mW red laser. We also present a predictive model of the heating effect induced at 810 nm, wherein the heating efficiencies of the various morphologies sharing this excitation peak are compared. Our model shows that the nanorod is the most effective at heat generation in the isolated scenario, and arrays of 91 nm long nanorods reached hyperthermic levels (an increase of at least 5 °C) within a volume of over 20 μm 3 .

Gold bipyramid (GBP) nanoparticles are promising for a range of biomedical applications, including biosensing and surface-enhanced Raman spectroscopy, due to their favorable optical properties and ease of chemical functionalization. Here we report improved synthesis methods, including preparation of gold seed particles with an increased shelf life of ∼1 month, and preparation of GBPs with significantly shortened synthesis time (< 1 h). We also report methods for the functionalization and bioconjugation of the GBPs, including functionalization with alkanethiol self-assembled monolayers (SAMs) and bioconjugation with proteins via carbodiimide cross-linking. Binding of specific antibodies to the nanoparticle-bound proteins was subsequently observed via localized surface plasmon resonance sensing. Rabbit IgG and goat anti-Rabbit IgG antibodies were used as a model system for antibody-antigen interactions. As-synthesized, SAM-functionalized, and bioconjugated bipyramids were characterized using scanning electron microscopy, UV–vis spectroscopy, zeta potential, and dynamic light scattering.

Surface-enhanced Raman scattering (SERS) spectra contain information on the chemical structure on nanoparticle surfaces through the position and alignment of molecules with the electromagnetic near field. Time-dependent density functional theory (TDDFT) can provide the Raman tensors needed for a detailed interpretation of SERS spectra. Here, the impact of molecular conformations on SERS spectra is considered. TDDFT calculations of the surfactant cetyltrimethylammonium bromide with five conformers produced more accurate unenhanced Raman spectra than a simple all-trans structure. The calculations and measurements also demonstrated a loss of structural information in the CH2/CH3 scissor vibration band at 1450 cm–1 in the SERS spectra. To study lipid bilayers, TDDFT calculations on conformers of methyl phosphorylcholine and cis-5-decene served as models for the symmetric choline stretch in the lipid headgroup and the CC stretch in the acyl chains of 1,2-oleoyl-glycero-3-phosphocholine. Conformer considerations enabled a measurement of the distribution of double-bond orientations with an order parameter of S CC = 0.53.

Nano-and micropatterns from the Langmuir− Blodgett (LB) assembly of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylene disodium salt nanoparticles (PPP-NPs) on glass substrates exhibited a variety of structures and tunable band gaps. Tuning the band gap of optical materials used in devices based on conjugated polymers is useful for manufacturing organic light-emitting diodes and optoelectronics. The PPP-NPs are prepared by supramolecular assembly of the polymer in methanol. A highly packed, collapsed PPP-NPs monolayer assembly is obtained when the uncompressed LB film is transferred to the surface of a glass substrate. The band gap of the PPP-NPs dispersed in methanol is reduced by 0.56 eV after monolayer assembly into 2D nanostructure with an average diameter of 28 ± 7 nm and 4.2 ± 0.5 nm height to be 2.47 eV. This large band gap decrease is attributed to the collapse of their supramolecular assembly, the interparticle energy transfer, and change of the dielectric function from methanol to air. Because of the soft nature of the PPP-NPs, compressing the LB film resulted in a hierarchical assembly of the PPP-NPs into microdisks with a few nanometers in thickness. The single microdisk has a band gap of 1.61 eV and a broad optical spectrum composed of multiple peaks due to random energy transfer between the PPP-NPs. When the LB film of the microdisks assembly is compressed, nanopillars of an average ∼200 nm diameter and ∼40 nm height are obtained, which have an intense optical signal. The band gap of the individual nanopillar is 1.6 eV.

The purpose of this study is to define a simplified method to accurately predict and characterize kV cone beam computed tomography (kV CBCT) and computed tomography (CT) image contrast enhancement from gold nanoparticles (GNPs). Parameters of the kV CBCT of a Varian Novalis Tx linear accelerator and of a GE LightSpeed 4 Big Bore CT machine were modeled using the MCNP 6.2 Monte Carlo code. A 0.25×0.25 cm 2 source, defined with a 100 kVp energy spectrum with appropriate filtration, was implemented in the MCNP6.2 model for kV CBCT, which also contained x-and y-blades and a full bowtie filter. A 1 cm 3 cube of GNP solution (modeled as a mass percentage of gold in water) was placed 100 cm below the source. For the CT-simulator model, a source was defined with energy spectra for 80 and 140 kVp x-rays with appropriate filtration and angular spectrum. A 1 cm 3 GNP solution was modeled as before and a detector was placed 40 cm below that. Attenuation coefficients of four GNP solutions were computed and Hounsfield unit (HU) values were calculated. The computed HU values were compared against experimentally measured values obtained by scanning batches of GNPs of various sizes and concentrations using a GE LightSpeed 4 Big Bore CT scanner at 80 kVp and 140 kVp energies, as well as the kV CBCT capability of a Varian Novalis Tx linear accelerator. HU analysis was carried out using Velocity Medical Solutions clinical CT image analysis software. The MCNP calculated HU values matched the measured values to within±5%. Image contrast enhancement analysis showed a total increase in HU of up to 223. The sample having the highest gold mass percentage tested showed the greatest increase in HU number compared to water.