Cryogenic electron tomography to determine thermodynamic quantities for nanoparticle dispersions

Here we present a method to extract thermodynamic quantities for nanoparticle dispersions in solvents. The method is based on the study of tomograms obtained from cryogenic electron tomography (cryoET). The approach is demonstrated for gold nanoparticles (diameter < 5 nm). Tomograms are reconstructed from tilt-series 2D images. Once the three-dimensional (3D) coordinates for the centres of mass of all of the particles in the sample are determined, we calculate the pair distribution function g(r) and the potential of mean force U(r) without any assumption. Importantly, we show that further quantitative information from 3D tomograms is readily available as the spatial fluctuation in the particles’ position can be efficiently determined. This in turn allows for the prompt derivation of the Kirkwood-Buff integrals with all their associated quantities such as the second virial coefficient. Finally, the structure factor and the agglomeration states of the particles are evaluated directly. These thermodynamic quantities provide key insights into the dispersion properties of the particles. The method works well both for dispersed systems containing isolated particles and for systems with varying degrees of agglomerations

Time-Resolved Study on Self-Assembling Behavior of PEGylated Gold Nanoparticles in the Presence of Human Serum Albumin: A System for Nanomedical Applications

The combination of a microfluidic approach for synchrotron-based dynamic (early structural changes) with lab-based static small-angle X-ray scattering (SAXS) measurements (longer time scale) allows qualifying nanoparticle (NP) systems for their use in nanomedicine. Time-resolved in situ investigations are performed on self-assembly and colloidal behavior of 5 nm PEGylated (polyethylene glycol) gold NPs in different media. SAXS methods combined with a micromixing fluidic system are used to observe the early stage of NP interactions. Dynamic measurements cover a time range from 1 to 100 s after mixing thoroughly, while static measurements complete the study for up to 10 days after sample preparation. These NPs, after mixing with saline solution (0.9% NaCl solution), self-assemble in 3D ordered domains. The NPs also show this ordering in the presence of human serum albumin (HSA) molecules. It is shown that, although the presence of protein molecules slows down the NP self-assembling process, these molecules improve the long-term colloidal stability of the ordered domains probably via interpolymer complexation between PEG and HSA molecules

New nanoprobe for breast cancer cell imaging based on low-density lipoprotein

AbstractMany malignant cancers have an increased demand for lipoprotein due to the requirement for lipids for the rapid proliferation of the tumours and which is met by the increased availability of LDL through upregulation of LDL transporters. This unique phenomenon is the basis for the use of LDL based nanoparticles for cell imaging. In this study, a novel MR-active LDL nanoparticle was synthesised as the MRI probes. This MR-active LDL was characterised by using different techniques including scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier-transform infra-red spectroscopy (FTIR) and magnetic resonance imaging (MRI). The intracellular uptake of Gd3+ and cytotoxicity was measured by ICP-AES and MTT assay respectively. Results suggest that this nanoprobe with spherical shape and size of 55 nm has reduced relaxation time compared to commercial contrast agent and is introduced as an appropriate imaging probe. The amount of reabsorption of nanoprobe increased up to 6 h and given that the connection of the chelator does not have an effect on reabsorption proves that entry through transporter of APO section has done. This study lays the basis for exploring a personalised medicine strategy by directing a patient’s own LDL to cancer cell imaging in the early stages

In-situ Investigations on Gold Nanoparticles Stabilization Mechanisms in Biological Environments Containing HSA

Nanoparticles (NPs) developments advance innovative biomedical applications. However, complex interactions and the low colloidal stability of NPs in biological media restrict their widespread utilization. The influence of NPs properties on the colloidal stability for gold NPs with 5 and 40 nm in diameter with two surface modifications, methoxy-polyethylene glycol-sulfhydryl (PEG) and citrate, in NaCl and human serum albumin (HSA) protein solution, is investigated. This study is based on small-angle X-ray scattering (SAXS) methods allowing the in-situ monitoring of interactions in physiological conditions. The PEG coating provides high colloidal stability for NPs of both sizes. For 5 nm NPs in NaCl solution, a stable 3D self-assembled body-centered cubic (BCC) arrangement is detected with an interparticle distance of 20.7 ± 0.1 nm. In protein solution, this distance increases to 21.9 ± 0.1 nm by protein penetration inside the ordered structure. For citrate-capped NPs, a different mechanism is observed. The protein particles attach to the NPs surfaces, and an appropriate concentration of proteins results in a stable suspension. Cryogenic transmission electron microscopy (Cryo-TEM), UV–visible spectroscopy, and dynamic light scattering (DLS) support the SAXS results. The findings will pave the way to design and synthesize NPs with controlled behaviors in biomedical applications

Iron-carbohydrate complexes treating iron anaemia: Understanding the nano-structure and interactions with proteins through orthogonal characterisation

Intravenous (IV) iron-carbohydrate complexes are widely used nanoparticles (NPs) to treat iron deficiency anaemia, often associated with medical conditions such as chronic kidney disease, heart failure and various inflammatory conditions. Even though a plethora of physicochemical characterisation data and clinical studies are available for these products, evidence-based correlation between physicochemical properties of iron-carbohydrate complexes and clinical outcome has not fully been elucidated yet. Studies on other metal oxide NPs suggest that early interactions between NPs and blood upon IV injection are key to understanding how differences in physicochemical characteristics of iron-carbohydrate complexes cause variance in clinical outcomes. We therefore investigated the core-ligand structure of two clinically relevant iron-carbohydrate complexes, iron sucrose (IS) and ferric carboxymaltose (FCM), and their interactions with two structurally different human plasma proteins, human serum albumin (HSA) and fibrinogen, using a combination of cryo-scanning transmission electron microscopy (cryo-STEM), x-ray diffraction (XRD), small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). Using this orthogonal approach, we defined the nano-structure, individual building blocks and surface morphology for IS and FCM. Importantly, we revealed significant differences in the surface morphology of the iron-carbohydrate complexes. FCM shows a localised carbohydrate shell around its core, in contrast to IS, which is characterised by a diffuse and dynamic layer of carbohydrate ligand surrounding its core. We hypothesised that such differences in carbohydrate morphology determine the interaction between iron-carbohydrate complexes and proteins and therefore investigated the NPs in the presence of HSA and fibrinogen. Intriguingly, IS showed significant interaction with HSA and fibrinogen, forming NP-protein clusters, while FCM only showed significant interaction with fibrinogen. We postulate that these differences could influence bio-response of the two formulations and their clinical outcome. In conclusion, our study provides orthogonal characterisation of two clinically relevant iron-carbohydrate complexes and first hints at their interaction behaviour with proteins in the human bloodstream, setting a prerequisite towards complete understanding of the correlation between physicochemical properties and clinical outcome.ISSN:0168-3659ISSN:1873-499