Effects of Mesoporous Silica Coating and Postsynthetic Treatment on the Transverse Relaxivity of Iron Oxide Nanoparticles

Mesoporous silica nanoparticles have the capacity to load and deliver therapeutic cargo and incorporate imaging modalities, making them prominent candidates for theranostic devices. One of the most widespread imaging agents utilized in this and other theranostic platforms is nanoscale superparamagnetic iron oxide. Although several core–shell magnetic mesoporous silica nanoparticles presented in the literature have provided high <i>T</i>₂ contrast in vitro and in vivo, there is ambiguity surrounding which parameters lead to enhanced contrast. Additionally, there is a need to understand the behavior of these imaging agents over time in biologically relevant environments. Herein, we present a systematic analysis of how the transverse relaxivity (<i>r</i>₂) of magnetic mesoporous silica nanoparticles is influenced by nanoparticle diameter, iron oxide nanoparticle core synthesis, and use of a hydrothermal treatment. This work demonstrates that samples which did not undergo a hydrothermal treatment experienced a drop in <i>r</i>₂ (75% of original <i>r</i>₂ within 8 days of water storage), while samples with hydrothermal treatment maintained roughly the same <i>r</i>₂ for over 30 days in water. Our results suggest that iron oxide oxidation is the cause of <i>r</i>₂ loss, and this oxidation can be prevented during both synthesis and storage by use of deoxygenated conditions during nanoparticle synthesis. Hydrothermal treatment also provides colloidal stability, even in acidic and highly salted solutions, and a resistance against acid degradation of the iron oxide nanoparticle core. Results of this study show the promise of multifunctional mesoporous silica nanoparticles but will also likely inspire further investigation into multiple types of theranostic devices, taking into consideration their behavior over time and in relevant biological environments

Introduction au dossier: «Retour sur La question du logement»

<p>Illustration of injury longitudinal strain (A) A case with left ventricular remodeling; injury longitudinal strain is –9.2%. (B) A case without left ventricular remodeling: injury longitudinal strain is –12.2%. Abnormal segments are marked with *, which indicates that the longitudinal strain is >–15%.</p

Univariate logistic regression for left ventricular remodeling in STEMI patients.

<p>Univariate logistic regression for left ventricular remodeling in STEMI patients.</p

Patients’ clinical characteristics.

<p>Patients’ clinical characteristics.</p

Univariate and multivariate logistic regression for left ventricular remodeling.

<p>Univariate and multivariate logistic regression for left ventricular remodeling.</p

Left ventricle deformation performance indices in STEMI patients.

<p>Left ventricle deformation performance indices in STEMI patients.</p

Echocardiographic findings in STEMI patients.

<p>Echocardiographic findings in STEMI patients.</p

Echocardiography findings.

<p>Echocardiography findings.</p

Clinical data for STEMI patients.

<p>Clinical data for STEMI patients.</p

Left ventricular deformation performance indices.

<p>Left ventricular deformation performance indices.</p