Theranostic nanocarrier for acyclovir: tailored SPIONs with MR contrast potential

In this study, we address the critical need for advanced theranostic drug delivery systems by synthesizing and characterizing surface-functionalized superparamagnetic iron oxide nanoparticles (SPIONs). Acyclovir is an effective antiviral drug with poor water solubility leading to limitations in its administrations and effectivity. Our investigation into the drug-loading capacity of acyclovir reveals that surface-functionalized SPIONs with an average size of 8.1 nm exhibit a notable increase in drug-loading capacity proportional to drug concentration. Specifically, at drug concentrations of 752.21 μg, 1774.32 μg, and 3799.09 μg, we achieved loading efficiencies and capacities of 40.89%, 51.62%, and 50.14% respectively. Alongside, they have high biocompatibility as observed from the hemolysis assay and MTT assay. Moreover, the multifunctionality of these SPIONs extends beyond drug delivery, as they demonstrate high relaxivity suitable for magnetic resonance imaging (MRI) studies at remarkably low concentrations in the micromolar range. Specifically, the relaxivity value (r2) for the said SPIONs was calculated to 10.99 L/mmol^−s which is higher than many commercially used iron oxide-based contrast agents. The multifunctional attributes of these SPIONs position them as versatile and easily customisable platform for diverse therapeutic molecules. This study not only underscores the feasibility of utilizing surface-modified SPIONs as efficient carriers for acyclovir or other therapeutic molecules but also paves the way for evaluating the feasibility of next-generation theranostic materials for biomedical applications.