Colloidal type II CdTe/CdSe nanocrystals were synthesized by sequential addition of a tri-n-octylphosphine telluride (TOPTe)/TOP solution and several shell-precursor solutions to a CdO/TOP solution; the shell-precursor solutions consisted of CdO and TOPSe in TOP. For the growth of the CdTe core, the TOPTe/TOP solution was swiftly added to the CdO/TOP solution at a higher temperature (300 degrees C) than the growth temperature (250 degrees C). For the growth of the CdSe shell, in contrast, the CdO/TOPSe/TOP solution was slowly added to the CdTe/TOP solution at a lower temperature than the growth temperature (200-240 degrees C). The temporal evolution of the optical properties of the growing core-shell nanocrystals was monitored in detail. During the growth of the CdSe shell, the core-shell nanocrystals exhibited interesting changes in photoluminescence (PL) properties. The highest PL efficiency (approximately 38 %) was detected from core-shell nanocrystals with a CdSe shell thickness of 0.4-0.5 nm (indicated by TEM); the formation of the first monolayer is proposed. Our synthetic approach is well suited to a practical realization of engineering materials with bandgaps in the near-IR and IR spectral ranges.

Graphical abstract

Traumatic brain injury (TBI) is a leading cause of injury-related death worldwide, yet there are no approved neuroprotective therapies that improve neurological outcome post-injury. Transient opening of the blood-brain barrier following injury provides an opportunity for passive accumulation of intravenously administered nanoparticles through an enhanced permeation and retention-like effect. However, a thorough understanding of physicochemical properties that promote optimal uptake and retention kinetics in TBI is still needed. In this study, we present a robust method for magnetic resonance imaging of nanoparticle uptake and retention kinetics following intravenous injection in a controlled cortical impact mouse model of TBI. Three contrast-enhancing nanoparticles with different hydrodynamic sizes and relaxivity properties were compared. Accumulation and retention were monitored by modelling the permeability coefficient, Ktrans, for each nanoparticle within the reproducible mouse model. Quantification of Ktrans for different nanoparticles allowed for non-invasive, multi-time point assessment of both accumulation and retention kinetics in the injured tissue. Using this method, we found that 80 nm poly(lactic-co-glycolic acid) nanoparticles had maximal Ktrans in a TBI when injected 3 hours post-injury, showing significantly higher accumulation kinetics than the small molecule, Gd-DTPA. This robust method will enable optimization of administration time and nanoparticle physicochemical properties to achieve maximum delivery.

Iontophoresis is an electrical‐current‐based, noninvasive drug‐delivery technology, which is particularly suitable for intraocular drug delivery. Current ocular iontophoresis devices use low current intensities that significantly limit macromolecule and nanoparticle (NP) delivery efficiency. Increasing current intensity leads to ocular tissue damage. Here, an iontophoresis device based on a hydrogel ionic circuit (HIC), for high‐efficiency intraocular macromolecule and NP delivery, is described. The HIC‐based device is capable of minimizing Joule heating, effectively buffering electrochemical (EC) reaction‐generated pH changes, and absorbing electrode overpotential‐induced heating. As a result, the device allows safe application of high current intensities (up to 87 mA cm−2, more than 10 times higher than current ocular iontophoresis devices) to the eye with minimal ocular cell death and tissue damage. The high‐intensity iontophoresis significantly enhances macromolecule and NP delivery to both the anterior and posterior segments by up to 300 times compared to the conventional iontophoresis. Therapeutically effective concentrations of bevacizumab and dexamethasone are delivered to target tissue compartments within 10–20 min of iontophoresis application. This study highlights the significant safety enhancement enabled by an HIC‐based device design and the potential of the device to deliver therapeutic doses of macromolecule and NP ophthalmic drugs within a clinically relevant time frame.