Magnetic nanoparticles (NPs) are increasingly being considered for use in biomedical applications such as biosensors, imaging contrast agents and drug delivery vehicles. In a biological fluid, proteins associate in a preferential manner with NPs. The small sizes and high curvature angles of NPs influence the types and amounts of proteins present on their surfaces. This differential display of proteins bound to the surface of NPs can influence the tissue distribution, cellular uptake and biological effects of NPs. To date, the effects of adsorption of a protein corona (PC) on the magnetic properties of NPs have not been considered, despite the fact that some of their potential applications require their use in human blood.Here, to investigate the effects of a PC (using fetal bovine serum) on the MRI contrast efficiency of superparamagnetic iron oxide NPs (SPIONs), we have synthesized two series of SPIONs with variation in the thickness and functional groups (i.e. surface charges) of the dextran surface coating. We have observed that different physico-chemical characteristics of the dextran coatings on the SPIONs lead to the formation of PCs of different compositions. 1 H relaxometry was used to obtain the longitudinal, r 1 , and transverse, r 2 , relaxivities of the SPIONs without and with a PC, as a function of the Larmor frequency. The transverse relaxivity, which determines the efficiency of negative contrast agents (CAs), is very much dependent on the functional group and the surface charge of the SPIONs' coating. The presence of the PC did not alter the relaxivity of plain SPIONs, while it slightly increased the relaxivity of the negatively charged SPIONs and dramatically decreased the relaxivity of the positively charged ones, which was coupled with particle agglomeration in the presence of the proteins. To confirm the effect of the PC on the MRI contrast efficiency, in vitro MRI experiments at n ¼ 8.5 MHz were performed using a low-field MRI scanner. The MRI contrasts, produced by different samples, were fully in agreement with the relaxometry findings.It is well-recognized that the surface of nanoparticles (NPs) is covered by biomolecules (proteins, sugars and lipids) upon coming into contact with biological systems, resulting in the formation of a protein "corona" that is strongly associated with the NPs' surface and that denes how living organisms (e.g. cells) "see" the NPs in a biological milieu. 1-5 According to previous reports, the cell "sees" a nano-system in which the NPs are covered by a "hard" corona of slowly exchanging proteins with a surrounding "so" corona consisting of weakly interacting and rapidly exchanging proteins. 6 The composition of the protein corona (PC) is highly dependent on the physicochemical properties of the NPs such as their size, composition, and surface characteristics. 7 Superparamagnetic iron oxide nanoparticles (SPIONs) have been recognized as very promising nanosystems with good biocompatibility 8,9 and high potential to be used for diagnosis and therapy simultaneou...

No abstract

Alzheimer's disease (AD) is the most common form of dementia. During the recent decade, nanotechnology has been widely considered, as a promising tool, for theranosis (diagnosis and therapy) of AD. Here we first discuss pathophysiology and characteristics of AD with a focus on the amyloid cascade hypothesis. Then magnetic nanoparticles (MNPs) and recent works on their applications in AD, focusing on the superparamagnetic iron oxide nanoparticles (SPIONs), are reviewed. Furthermore, the amyloid−nanoparticle interaction is highlighted, with the scope to be highly considered by the scientists aiming for diagnostics and/or treatment of AD employing nanoparticles. Furthermore, recent findings on the "ignored" parameters (e.g., effect of protein "corona" at the surface of nanoparticles on amyloid-β (Aβ) fibrillation process) are discussed. KEYWORDS: Magnetic resonance imaging, SPION, amyloid-β, nanomedicine, nanotechnology A lzheimer's disease (AD) is named after Alois Alzheimer, who described the first case in a 55 year old female patient (i.e., Auguste Deter) in 1906. The description of Auguste's pathology was featured by lifelong deteriorating memory, speaking, physical, and social abilities. After her death, the autopsy revealed uniform brain atrophy, atherosclerosis changes in larger cerebral vessels, neuronal loss, and numerous small foci perceivable even without staining distributed over the entire cortex. It took over 70 years to reveal that those foci consist of aggregates of extracellular loads of small peptides called amyloid-β (Aβ), that are considered today one of the hallmarks of the disease. 1 AD is characterized by progressive deterioration of cognitive function, most commonly of memory, that increasingly interferes with patients' daily activities leading to loss of independency (for details, see http://www.alz.org/downloads/ facts_figures_2012.pdf). To date, no precise treatments have been clinically proven to avoid or prevent the progression of AD. Several different pharmacological agents can only ameliorate or provide temporary alleviation of the symptoms. 2 In this review, we introduce clinical aspects and characteristics of AD with a focus on the amyloid cascade hypothesis. Magnetic nanoparticles (MNPs), as promising theranosis tools, are introduced, and recent reports on the potential applications of superparamagnetic iron oxide nanoparticles (SPIONs) in AD are summarized. It is worthwhile to note that the SPIONs are known as promising theranosis candidates for AD, due to their biocompatibility, unique magnetic properties and multifunctional application capability. 3,4 The amyloid−nanoparticle interaction is highlighted, with the scope to be highly considered by the scientific community aiming for diagnostics and/or treatment of AD employing nanoparticles. Moreover, recent findings on the "ignored" parameters (e.g., the effect of protein "corona" at the surface of nanoparticles on Aβ fibrillation process) are discussed.