The Key Role of Intrinsic Lifetime Dynamics from Upconverting Nanosystems in Multiemission Particle Velocimetry

Evaluation of particle dynamics at the nano- and microscale poses a challenge to the development of novel velocimetry techniques. Established optical methods implement external or internal calibrations of the emission profiles by varying the particle velocity and are limited to specific experimental conditions. The proposed multiemission particle velocimetry approach aims to introduce a new concept for a luminescent probe, which guarantees accurate velocity measurements at the microscale, independent of the particle concentration or experimental setup, and without need for calibration. The simplicity of these analyses relies on the intrinsic luminescence dynamics of core-shell upconverting nanoparticles. Upon excitation with a focused near-infrared pulsed laser, the nanoparticle emits photons at different wavelengths. The time interval between emissions from different excited states is independent of the local environment or particle velocity. The velocity of the particles is calculated by measuring the distance between the maxima of two different emissions and dividing it by the known difference in luminescence lifetimes. This method is demonstrated using simple digital imaging of nanoparticles flowing in 75-150 µm diameter capillaries. Using this novel approach typically results in a relative standard deviation of the experimental velocities of 5% or lower without any calibration.

Wavelength-Selective Nonlinear Imaging and Photo-Induced Cell Damage by Dielectric Harmonic Nanoparticles

We introduce a nonlinear all-optical theranostics protocol based on the excitation wavelength decoupling between imaging and photoinduced damage of human cancer cells labeled by bismuth ferrite (BFO) harmonic nanoparticles (HNPs). To characterize the damage process, we rely on a scheme for in situ temperature monitoring based on upconversion nanoparticles: by spectrally resolving the emission of silica coated NaGdF4:Yb³⁺/Er³⁺ nanoparticles in close vicinity of a BFO HNP, we show that the photointeraction upon NIR-I excitation at high irradiance is associated with a temperature increase >100 °C. The observed laser-cell interaction implies a permanent change of the BFO nonlinear optical properties, which can be used as a proxy to read out the outcome of a theranostics procedure combining imaging at 980 nm and selective cell damage at 830 nm. The approach has potential applications to monitor and treat lesions within NIR light penetration depth in tissues.

Intrinsic Time-Tunable Emissions in Core-Shell Upconverting Nanoparticle Systems

Color-tunable luminescence has been extensively investigated in upconverting nanoparticles for diverse applications, each exploiting emissions in different spectral regions. Manipulation of the emission wavelength is accomplished by varying the composition of the luminescent material or the characteristics of the excitation source. Herein, we propose core-shell β-NaGdF₄ : Tm³⁺ , Yb³⁺ /β-NaGdF₄ : Tb³⁺ nanoparticles as intrinsic time-tunable luminescent materials. The time dependency of the emission wavelength only depends on the different decay time of the two emitters, without additional variation of the dopant concentration or pumping source. The time-tunable emission was recorded with a commercially available camera. The dynamics of the emissions is thoroughly investigated, and we established that the energy transfer from the ¹ D₂ excited state of Tm³⁺ ions to the higher energy excited states of Tb³⁺ ions to be the principal mechanism to the population of the ⁵ D₄ level for the Tb³⁺ ions.

Dual Activity of Rose Bengal Functionalized to Albumin-Coated Lanthanide-Doped Upconverting Nanoparticles: Targeting and Photodynamic Therapy

A modified version of a desolvation method was used to render lanthanide-doped upconverting nanoparticles NaGdF₄:Yb³⁺/Er³⁺ (Ln-UCNPs) water-dispersible and biocompatible for photodynamic therapy. Bovine serum albumin (BSA) was used as surface coating with a direct conjugation to NaGdF₄:Yb³⁺/Er³⁺ nanoparticles forming a ∼2 nm thick shell. It was estimated that approximately 112 molecules of BSA were present and cross-linked per NaGdF₄:Yb³⁺/Er³⁺ nanoparticle. Analysis of the BSA structural behavior on the Ln-UCNP surfaces displayed up to 80% loss of α-helical content. Modification of the Ln-UCNPs with a BSA shell prevents luminescence quenching from solvent molecules (H₂O) with high energy vibrations that can interact with the excited states of the optically active ions Er³⁺ and Yb³⁺ via dipole-dipole interactions. Additionally, the photosensitizer rose bengal (RB) was conjugated to albumin on the surface of the Ln-UCNPs. Emission spectroscopy under 980 nm excitation was carried out, and an energy transfer efficiency of 63% was obtained. In vitro cell studies performed using human lung cancer cells (A549 cell line) showed that Ln-UCNPs coated with BSA were not taken by the cells. However, when RB was conjugated to BSA on the surface of the nanoparticles, cellular uptake was observed, and cytotoxicity was induced by the production of singlet oxygen under 980 nm irradiation.

Solitary ivory vertebra due to primary Ewing's sarcoma

Dense sclerosis of most of the vertebral body has been termed as "ivory vertebra". While this condition occurs rather frequently in adults it is not found very often in children.

Clinicoradiological diagnosis of benign osteoblastoma of the spine in children

Three cases of benign osteoblastoma of the spine in children are reported, diagnosed on the basis of clinicoradiological findings and confirmed at surgery and by histopathology. The authors feel that in all cases of painful scoliosis and painful torticollis, a careful search should be made for any suspicious area of sclerosis, especially in the posterior elements of the vertebrae, and all the positive or suspected cases should undergo nuclear bone scanning. All patients whose bone scan is positive should be subjected to computed tomography for differential diagnosis between osteoid osteoma and benign osteoblastoma.

Clubfoot with supernumerary soleus muscle. Report of 2 cases

In 2 cases of clubfoot with severe and rigid varus deformity, an accessory soleus muscle with attachment on the medial side of the calcaneus was found. After cutting the distal attachment of this muscle, the deformity diminished. The accessory soleus muscle is not interpreted as the primary cause of the clubfoot, but as a highly contributing cause to the rigid varus deformity.

Spinal brucellosis

Twenty-four cases of spinal brucellosis are described. We believe that it is possible to distinguish this condition from spinal tuberculosis on the basis of the clinical and radiological findings.