New drug discovery technique to identify compounds binding to transmembrane receptors in complex mixtures.

Ultrasmall iron oxide nanoparticles (USIONPs) (<4 nm) have recently attracted significant attention because of their potential as positive T 1 magnetic resonance imaging (MRI) contrast agent contrary to larger superparamagnetic iron oxide nanoparticles (>6 nm) which act as negative T 2 MRI contrast agents. However, studies on the cellular uptake behavior of these nanoparticles are very limited compared to their counterpart, larger-sized superparamagnetic iron oxide nanoparticles. In particular, the effects of specific nanoparticle parameters on the cellular uptake behavior of USIONPs by various cancer cells are not available. Here, we specifically investigated the role of USIONPs’ surface functionalities [tannic acid (TA) and quinic acid (QA)] in mediating cellular uptake behavior of cancer cells pertaining to primary (U87 cells) and metastatic (MDA-MB-231Br cells) brain malignancies. Here, we chose TA and QA as representative capping molecules, wherein TA coating provides a general negatively charged nontargeting surface while QA provides a tumor-targeting surface as QA and its derivatives are known to interact with selectin receptors expressed on tumor cells and tumor endothelium. We observed differential cellular uptake in the case of TA- and QA-coated USIONPs by cancer cells. Both the cell types showed significantly higher cellular uptake of QA-coated USIONPs compared to TA-coated USIONPs at 4, 24, and 72 h. Blocking studies indicated that P-selectin cell surface receptors, in part, mediated the cellular uptake of QA-coated USIONPs. Given that P-selectin is overexpressed in cancer cells, tumor microenvironment, and at the metastatic niche, QA-coated USIONPs hold potential to be utilized as a platform for tumor-targeted drug delivery and in imaging and detection of primary and metastatic tumors.

Magnetic iron oxide nanoclusters, which refers to a group of individual nanoparticles, have recently attracted much attention because of their distinctive behaviors compared to individual nanoparticles. In this review, we discuss preparation methods for creating iron oxide nanoclusters, focusing on synthetic procedures, formation mechanisms, and the quality of the products. Then, we discuss the emerging applications for iron oxide nanoclusters in various fields, covering traditional and novel applications in magnetic separation, bioimaging, drug delivery, and magnetically responsive photonic crystals.

Inorganic nanoparticles as MALDI matrices have recently been explored to study the molecular mass determination and structural analysis of glycans and peptides. However, the specific factors contributing to the success of the analysis are not well elucidated. In this paper, we investigated the roles of nanoparticle surface coatings and additive ions in MALDI in-source decay (ISD) analysis of model glycans and peptides. Specifically, iron oxide nanoparticles with four defined capping molecules (gluconic acid, citric acid, lactobionic acid, or glutathione) were tested, and the roles of additives (NH4OH, NaOH, LiOH, NaCl, or trifluoroacetic acid) were examined. For a model glycan, maltoheptaose, and a model peptide, substance P acid, nanoparticle capping molecules, additive cations, and additive anions altogether influenced the molecular ion sensitivity and ISD fragmentation efficiency.

Ultrasmall iron oxide nanoparticles (USIONPs) have been recently developed as labeling probes for T 2 magnetic resonance imaging contrast agents. However, their use in stem cell tracking has been limited, especially as T 1 contrast agents. In this study, we studied the effects of USIONP surface coatings on proliferation, cellular uptake, and multipontency of established and primary neural stem cells (NSCs). USIONPs were functionalized with gluconic acid (GA), tannic acid (TA), and hyaluronic acid (HA) to label the NSCs. All functionalized USIONPs were characterized as T 1 contrast agents via relaxivity measurements. Direct functionalization with TA and HA coating promoted NSC proliferation and enhanced cellular uptake in a dose-dependent manner compared to those with GA. Furthermore, HA coating showed enhanced cell proliferation and cellular uptake in primary NSCs depending on the HA molecular weight. Stem cell characteristics were well-maintained, verified by neurosphere formation and gene expression of stemness and differentiation markers. Collectively, we demonstrated that NSC proliferation, cellular uptake, and multipotency can be enhanced using various surface coating strategies of USIONPs.