Fast and Inexpensive Separation of Bright Phosphor Particles from Commercial Sources by Gravitational and Centrifugal Sedimentation for Deep Tissue X-ray Luminescence Imaging

Abstract

X-ray luminescence tomography (XLT) detects X-ray scintillators contrast agents using a focused or collimated X-ray beam to provide high spatial resolution excitation through thick tissue. The approach requires bright nanophosphors that are either synthesized or purchased. However, currently available commercial nanophosphors are mostly composed of a polydisperse mixture of several micro- to nano-sized particles that are unsuitable for biomedical imaging applications because of their size and aggregated form. Here, we demonstrate a fast and robust method to obtain uniform nano to submicron phosphor particles from a commercial source of polydisperse Eu- and Tb-doped Gd2O2S particles by separating the smaller particles present using gravitational and centrifugal sedimentation. In contrast to ball milling for 15–60 min, which drastically degraded the particles’ brightness while reducing their size, our sedimentation method enabled the extraction of comparatively bright nanophosphors (≈100–300 nm in size) with a luminescence intensity of ≈10–20% of the several micron particles in the sample. Moreover, if scale up for higher yielding is required, the sedimentation process can be accelerated using fixed-angle and/or swinging bucket rotating centrifugation. Finally, after separation and characterization, nano and submicron phosphors were suspended and imaged through 5 mm thick porcine tissue using our in-house-built scanning X-ray induced luminescence chemical imaging (XELCI) system.

Measurement of Submicron Particle Size Using Scattering Angle-Corrected Polarization Difference with High Angular Resolution

“…The Chahine algorithm is an iterative algorithm with a simple iterative formula and a fast convergence rate [35,36]. The iteration format of the algorithm is shown as Equation (17). Firstly, an initial value W (1) is set for the particle size distribution W, and iteration is performed using Equations ( 17) and (18).…”

“…Submicron particles can be used as additives, cured coatings, and adhesives with excellent physical, chemical, and surface properties, which help to improve product performance [6][7][8][9][10][11]. The particle size of submicron particles significantly affects their effectiveness in application [12][13][14][15][16][17]. Therefore, the particle size becomes an important indicator of the quality of submicron particles, and obtaining the particle size distribution has become an essential and important step in the preparation of submicron particles.…”