Evaluating differential nanoparticle accumulation and retention kinetics in a mouse model of traumatic brain injury via Ktrans mapping with MRI.

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.

Optical Projection Tomography with a Tissue Clearing Agent for Developmental and Reproductive Toxicology Studies.

BACKGROUND: Developmental and reproductive toxicology (DART) testing represents an expensive and time-consuming stage in determining the toxicological profile of new chemical entities. Within DART studies, morphological evaluation of fetal skeletons for developmental abnormalities typically requires 7 to 14 days. Current processing techniques involve digestion of soft tissue using a strong base (KOH), followed by qualitative assessment of the remaining skeletal tissue by a fetal morphologist. Micro-computed tomography (micro-CT) has been proposed as a nondestructive image-based alternative for quantitative assessment of skeletal morphology. Such methods eliminate the need for extensive tissue processing and can be paired with quantitative analysis algorithms. However, due to the significant capital and operational expenses required for micro-CT imaging, this approach has yet to gain widespread traction and regulatory acceptance. METHODS: A novel tissue clearing agent was used in 1-week-old rats to render soft tissue optically transparent. Alizarin red was used to stain the skeleton. High dynamic range optical trans-illumination images were then acquired with an optical-CT imaging system and rendered as three-dimensional images of skeletal structure. RESULTS: High dynamic range-based optical-CT imaging of chemically cleared tissues can rapidly generate high resolution (50-250 µm) reconstructions of whole skeletons. CONCLUSION: In summary, this study demonstrates that the combination of tissue clearing, optical imaging, and novel reconstruction algorithms may present a new paradigm for high-throughput evaluation of tissues in DART testing. Birth Defects Research 110:12-16, 2018. © 2017 Wiley Periodicals, Inc.

Rapid focus map surveying for whole slide imaging with continuous sample motion.

Whole slide imaging (WSI) has recently been cleared for primary diagnosis in the U.S. A critical challenge of WSI is to perform accurate focusing in high speed. Traditional systems create a focus map prior to scanning. For each focus point on the map, a sample needs to be static in the x-y plane, and axial scanning is needed to maximize the contrast. Here we report a novel focus map surveying method for WSI. In this method, we illuminate the sample with two LEDs and recover the focus points based on 1D autocorrelation analysis. The reported method requires no axial scanning, no additional camera and lens, works for stained and transparent samples, and allows continuous sample motion in the surveying process. By using a 20× objective lens, we demonstrate a mean focusing error of ∼0.08 µm in the static mode and ∼0.17 µm in the continuous motion mode. The reported method may provide a turnkey solution for most existing WSI systems due to its simplicity, robustness, accuracy, and high speed. It may also standardize the imaging performance of WSI systems for digital pathology and find other applications in high-content microscopy, such as time-lapse live-cell imaging.

Core-Cross-Linked Nanoparticles Reduce Neuroinflammation and Improve Outcome in a Mouse Model of Traumatic Brain Injury.

Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults, yet there are currently no treatments available that prevent the secondary spread of damage beyond the initial insult. The chronic progression of this secondary injury is in part caused by the release of reactive oxygen species (ROS) into surrounding normal brain. Thus, treatments that can enter the brain and reduce the spread of ROS should improve outcome from TBI. Here a highly versatile, reproducible, and scalable method to synthesize core-cross-linked nanoparticles (NPs) from polysorbate 80 (PS80) using a combination of thiol-ene and thiol-Michael chemistry is described. The resultant NPs consist of a ROS-reactive thioether cross-linked core stabilized in aqueous solution by hydroxy-functional oligoethylene oxide segments. These NPs show narrow molecular weight distributions and have a high proportion of thioether units that reduce local levels of ROS. In a controlled cortical impact mouse model of TBI, the NPs are able to rapidly accumulate and be retained in damaged brain as visualized through fluorescence imaging, reduce neuroinflammation and the secondary spread of injury as determined through magnetic resonance imaging and histopathology, and improve functional outcome as determined through behavioral analyses. Our findings provide strong evidence that these NPs may, upon further development and testing, provide a useful strategy to help improve the outcome of patients following a TBI.