We established a procedure to develop a localized surface plasmon resonance (LSPR) optical sensor platform for immunoassay. Computational simulations, focused on the assessment of the LSPR spectrum and spatial distribution of the electromagnetic field enhancement near the metallic nanoparticle, were used to engineer a nanostructured-sensing platform. Crucial parameters that rule the LSPR sensor performance, as bulk and molecular sensitivity, were evaluated, guiding the development of the optical platform. An LSPR surface-based platform composed of silver nanospheres adhered on a glass slide and functionalized with monoclonal anti-Candida antibodies of the IgG class was fabricated. Molecular biosensing was demonstrated by the identification of Candida albicans antigen. In particular, C. albicans is the most common species involved in a variety of hospital yeast infections. The developed sensing platform was able to identify C. albicans antigen concentration as low as 50 ng / mL, indicating the viability of exploring LSPR effect on C. albicans antigen biosensor. Moreover, this work provides insight on the LSPR behavior due to the adsorption of molecules layer on a nanoparticle surface, establishing a paradigm on engineering LSPR biosensor.
We evaluated the damage caused to optically trapped red blood cells (RBCs) after 1 or 2 min of exposure to near-infrared (NIR) laser beams at 785 or 1064 nm. Damage was quantified by measuring cell elasticity using an automatic, real-time, homemade, optical tweezer system. The measurements, performed on a significant number (hundreds) of cells, revealed an overall deformability decrease up to ∼104% after 2 min of light exposure, under 10 mW optical trapping for the 785-nm wavelength. Wavelength dependence of the optical damage is attributed to the light absorption by hemoglobin. The results provided evidence that RBCs have their biomechanical properties affected by NIR radiation. Our findings establish limits for laser applications with RBCs.
In this work we demonstrate the potential use of gold nanoparticles as contrast agents for the optical coherence tomography (OCT) imaging technique in dentistry. Here, a new in situ photothermal reduction procedure was developed, producing spherical gold nanoparticles inside dentinal layers and tubules. Gold ions were dispersed in the primer of commercially available dental bonding systems. After the application and permeation in dentin by the modified adhesive systems, the dental bonding materials were photopolymerized concurrently with the formation of gold nanoparticles. The gold nanoparticles were visualized by scanning electron microscopy (SEM). The SEM images show the presence of gold nanospheres in the hybrid layer and dentinal tubules. The diameter of the gold nanoparticles was determined to be in the range of 40 to 120 nm. Optical coherence tomography images were obtained in two- and three-dimensions. The distribution of nanoparticles was analyzed and the extended depth of nanosphere production was determined. The results show that the OCT technique, using in situ formed gold nanoparticles as contrast enhancers, can be used to visualize dentin structures in a non-invasive and non-destructive way.
Here we report on a new variation of the Z-scan method to characterize the third-order optical nonlinearity of photonic
materials. By exploiting a Hartmann-Shack wavefront sensor on a Z-scan set up we demonstrate an improvement in
sensitivity of the method. We also show that the method is suitable for the evaluation of samples having strong nonlinear
absorption. The nonlinear indices of refraction values have been obtained by analyzing the variation of the fifth-order
Zernike coefficients C5 that describe defocus as function of the sample position on the Z-scan setup. Here the method is
demonstrated by evaluating the nonlinear optical properties of CS2 and Coumarin as standard materials, using a 1 KHz
repetition rate Ti-Sapphire laser delivering 100fs pulses.
Here we analyze the influence of 9 nm (mean diameter) silver particles on the nonlinear properties of intrinsic cell
molecules. A novel high sensitivity thermal managed eclipse Z-scan technique with a femtosecond laser system was used
to analyze the nonlinear susceptibility of water solution of fluorescent and non-fluorescent amino acids (Tryptophan,
Tyrosine, Phenylalanine, Proline and Histidine) with different concentration of silver nanoparticles. The generalized
Maxwell Garnett model is used to explain the behavior of the measured nonlinear refractive index with the change of the
nanoparticles concentration in the sample.
The field of Nonlinear Optics has provided many techniques to characterize photonic materials. The Z-scan method is a
well estabileshed technique that exploits front wave distortions of the light beam to determine the nonlinear properties of
optical materials. Several variations of the methods have been developed, as the eclipse Z-scan that can provide up to
two orders of magnitude higher sensitivity than the original Z-scan set-up. We report a new variation of the Z-scan
method to characterize the third-order optical nonlinearity of photonic materials. By exploiting the combination of the
eclipse Z-scan with thermal nonlinearity management, we demonstrate an improvement in sensitivity and flexibility of
the method to simultaneously characterize the thermal and nonthermal nonlinearity of optical materials. The method is
demonstrated by measuring the nonlinear refractive index in CS2, SiO2 and H2O as standard materials, and also of a
biomaterial, the amino acid Tryptophan in water solution, using the same experimental set up based on a femtosecond
Ti-saphire laser operating at 76MHz repetition rate.
The inner structure of teeth, i.e. the root canal anatomy, is very complex. However a good knowledge of endodontic architecture is the first step towards successful endodontic treatment. Optical coherence tomography (OCT) is a powerful technique to generate images of hard and soft tissue. Its images show dependency on the optical properties of the tissue under analysis. Changes in the scattering and absorption of tissues can be observed through the OCT images. In this work, we used optical coherence tomography to perform in vitro studies of the inner structure of the first molar of albino rats (Rattus norvegicus). Focusing on the pulp chamber and in the root canal, we compare the images generated with the OCT technique to the histology. We are analyzing the feasibility of OCT to help on the diagnostic of endodontic diseases.
Evaluation of molar dental restorations on enamel is performed using optical coherence tomography (OCT) with 10 µm resolution. Images of ~50 µm failure gaps in the restorations are demonstrated and the OCT images are compared with x-ray and optical microscopy pictures. The results demonstrate the potential of the technique for clinical evaluation of dental restorations.