Blood–Nanoparticle Interactions and <i>in Vivo</i> Biodistribution: Impact of Surface PEG and Ligand Properties

Theranostic nanoparticles (NPs) cannot reach their target tissue without first passing through blood; however, the influence of blood protein and blood cell interactions on NP biodistribution are not well understood. The current work shows that 30 nm PEGylated gold NPs (GNPs) interact not only with blood proteins as thought before but also with blood cells (especially platelets and monocytes) <i>in vivo</i> and that longer blood circulation correlates strongly with tumor uptake. Further, GNP surface properties such as negative charge or lyophilization had either a minimal (i.e., charge) or 15-fold increase (i.e., fresh vs lyophilized) in blood retention times and tumor uptake. Tumor accumulation was increased over 10-fold by use of a bioactive ligand (i.e., TNF) on the lyophilized GNP surface. Resident macrophages were primarily responsible for the bulk of GNP uptake in liver while spleen uptake was highly surface property dependent and appears to involve macrophages and cellular interaction between the red and white pulp. This study shows that the PEG layer and ligand on the surface of the NP are critical to blood interactions and eventual tumor and RES organ biodistribution <i>in vivo</i>

Diagnostic laboratory standardization and validation of platelet transmission electron microscopy

<p>Platelet transmission electron microscopy (PTEM) is considered the gold standard test for assessing distinct ultrastructural abnormalities in inherited platelet disorders (IPDs). Nevertheless, PTEM remains mainly a research tool due to the lack of standardized procedures, a validated dense granule (DG) count reference range, and standardized image interpretation criteria. The aim of this study was to standardize and validate PTEM as a clinical laboratory test. Based on previously established methods, we optimized and standardized preanalytical, analytical, and postanalytical procedures for both whole mount (WM) and thin section (TS) PTEM. Mean number of DG/platelet (plt), percentage of plts without DG, platelet count (PC), mean platelet volume (MPV), immature platelet fraction (IPF), and plt light transmission aggregometry analyses were measured on blood samples from 113 healthy donors. Quantile regression was used to estimate the reference range for DG/plt, and linear regression was used to assess the association of DG/plt with other plt measurements. All PTEM procedures were standardized using commercially available materials and reagents. DG interpretation criteria were established based on previous publications and expert consensus, and resulted in improved operator agreement. Mean DG/plt was stable for 2 days after blood sample collection. The median within patient coefficient of variation for mean DG/plt was 22.2%; the mean DG/plt reference range (mid-95th %) was 1.2–4.0. Mean DG/plt was associated with IPF (<i>p </i>= .01, R² = 0.06) but not age, sex, PC, MPV, or plt maximum aggregation or primary slope of aggregation (<i>p </i>> .17, R² < 0.02). Baseline ultrastructural features were established for TS-PTEM. PTEM was validated using samples from patients with previously established diagnoses of IPDs. Standardization and validation of PTEM procedures and interpretation, and establishment of the normal mean DG/plt reference range and PTEM baseline ultrastructural features, will facilitate implementation of PTEM as a valid clinical laboratory test for evaluating ultrastructural abnormalities in IPDs.</p