High-resolution 3D photopolymerization assisted by upconversion nanoparticles for rapid prototyping applications.

Three-dimensional (3D) rapid prototyping technology based on near-infrared light-induced polymerization of photocurable compositions containing upconversion nanomaterials has been explored. For this aim, the rationally-designed core/shell upconversion nanoparticles NaYF:Yb,Tm/NaYF, with the distinct ultraviolet-emitting lines and unprecedentedly high near-infrared to ultraviolet conversion efficiency of [Formula: see text] have been used. The upconverted ultraviolet photons were capable to efficiently activate photoinitiators contained in light-sensitive resins under moderate intensities of NIR excitation below 10 W cm and induce generation of radicals and photopolymerization in situ.

Ultraviolet phototoxicity of upconversion nanoparticles illuminated with near-infrared light.

Recently introduced upconversion nanoparticles (UCNPs) have pushed the depth of photodynamic therapy (PDT) treatment to the centimetre range by converting deeply-penetrating near-infrared (NIR) radiation to visible radiation for photoexcitation of PDT drugs. Here we demonstrate that the direct exposure of the cancer tissue to phototoxic ultraviolet radiation generated by NIR-photoexcited UCNPs enabled successful PDT. To this aim, core/shell UCNPs of the formula NaYF:YbTm/NaYF featuring an enhanced band in the ultraviolet UV-A and UV-B spectral bands were rationally designed and synthesised.

[Experimental realization of minimally invasive techniques of scleral collagen cross-linking].

Aim: To realize two minimally invasive techniques of scleral collagen cross-linking (SXL) at the equator and posterior pole of the eye: 1) targeted irradiation of the region with ultraviolet A (UVA) and 2) sub-Tenon injection of Sklerateks.

Material And Methods: To perform UVA-SXL, a tool was developed that includes a UV-LED light source (370 nm, 3 mW/cm2) and a polymer-coated silica multimode optical fiber located in one of the two channels of a detachable metal tip. The other channel is used to deliver riboflavin to the scleral surface.

The influence of energy migration on luminescence kinetics parameters in upconversion nanoparticles.

The mechanism of upconversion at the nanoscale is still under discussion. In this paper, we report on the experimental results of anti-Stokes luminescence kinetics in the upconversion nanoparticles of β-NaYF: 20%Yb; 0.6%Tm.

Riboflavin photoactivation by upconversion nanoparticles for cancer treatment.

Riboflavin (Rf) is a vitamin and endogenous photosensitizer capable to generate reactive oxygen species (ROS) under UV-blue irradiation and kill cancer cells, which are characterized by the enhanced uptake of Rf. We confirmed its phototoxicity on human breast adenocarcinoma cells SK-BR-3 preincubated with 30-μM Rf and irradiated with ultraviolet light, and proved that such Rf concentrations (60 μM) are attainable in vivo in tumour site by systemic intravascular injection. In order to extend the Rf photosensitization depth in cancer tissue to 6 mm in depth, we purpose-designed core/shell upconversion nanoparticles (UCNPs, NaYF:Yb:Tm/NaYF) capable to convert 2% of the deeply-penetrating excitation at 975 nm to ultraviolet-blue power.

Model for Optimization of the UV-A/Riboflavin Strengthening (cross-linking) of the Cornea: Percolation Threshold.

To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results.

Incoherent wavefront reconstruction by a retroemission device.

This Letter addresses wavefront reconstruction by a retroemission device (REM). REM represents a lenslet array mounted on a substrate made of photoluminescent optical material, such as a polymer film impregnated with upconversion nanoparticles. An excitation light wavefront incident on the REM was sampled by the lenslet array piece-wise.

Submicron polyacrolein particles in situ embedded with upconversion nanoparticles for bioassay.

We report a new surface modification approach of upconversion nanoparticles (UCNPs) structured as inorganic hosts NaYF4 codoped with Yb(3+) and Er(3+) based on their encapsulation in a two-stage process of precipitation polymerization of acrolein under alkaline conditions in the presence of UCNPs. The use of tetramethylammonium hydroxide both as an initiator of acrolein polymerization and as an agent for UCNP hydrophilization made it possible to increase the polyacrolein yield up to 90%. This approach enabled the facile, lossless embedment of UCNPs into the polymer particles suitable for bioassay.

Visualization of upconverting nanoparticles in strongly scattering media.

Optical visualization systems are needed in medical applications for determining the localization of deep-seated luminescent markers in biotissues. The spatial resolution of such systems is limited by the scattering of the tissues. We present a novel epi-luminescent technique, which allows a 1.

Feasibility study of the optical imaging of a breast cancer lesion labeled with upconversion nanoparticle biocomplexes.

Innovative luminescent nanomaterials, termed upconversion nanoparticles (UCNPs), have demonstrated considerable promise as molecular probes for high-contrast optical imaging in cells and small animals. The feasibility study of optical diagnostics in humans is reported here based on experimental and theoretical modeling of optical imaging of an UCNP-labeled breast cancer lesion. UCNPs synthesized in-house were surface-capped with an amphiphilic polymer to achieve good colloidal stability in aqueous buffer solutions.

Quantitative imaging of single upconversion nanoparticles in biological tissue.

The unique luminescent properties of new-generation synthetic nanomaterials, upconversion nanoparticles (UCNPs), enabled high-contrast optical biomedical imaging by suppressing the crowded background of biological tissue autofluorescence and evading high tissue absorption. This raised high expectations on the UCNP utilities for intracellular and deep tissue imaging, such as whole animal imaging. At the same time, the critical nonlinear dependence of the UCNP luminescence on the excitation intensity results in dramatic signal reduction at (∼1 cm) depth in biological tissue.

[From scattering to wavefront. Healing optics].

The purpose of this report, made within research in progress, was to discuss the optical effect of irregular surface structures that might be associated with complicated refractive procedures related with the retinal image quality. We concentrated our discussion on the range of surface structures between the known scattering effects and wavefront aberrations of higher orders. The case study demonstrates that the surface irregularities of the cornea might induce, after refractive laser surgery, significant optical aberrations that are much too different from the classical wavevront or scattering errors.

From scattering to wavefronts--what's in between?

Purpose: Some optical errors are too localized and random to be detected by commercial wavefront devices and Zernike polynomial expression. We looked beyond aberrations defined by Zernike expression to discuss implications of fine irregularities associated with highly aberrated corneal surfaces and complex surface roughness that can lead to light scattering.

Methods: Most fine irregularities are related to postoperative surface roughness, complexities of corneal ablation, and the laser in situ keratomileusis (LASIK) flap.

[Effect of optic aberrations, caused by ablation pattern decentration after laser vision correction, on visual acuity].

The aim of this work was to study the effects of subclinical ablation pattern decentration on the quality of vision after photorefractive laser surgery. Optical high order spherical and coma-like aberrations of 30 eyes were evaluated before, 1 and 3 months after photorefractive surgery (PRK and LASIK). Relationship between the size and shape of the light spot on the retina during transmission of paraxial beams through the eye and the ablation zone decentrations was estimated.