Superparamagnetic iron oxide nanoparticles (SPIONs) are approved by the Food and Drug (FDA) in the United States. SPIONs are used in magnetic resonance imaging (MRI) as contrast agents and for target delivery in nanomedicine using external magnet sources. These can also act as an artificial peroxidase (i.e. nanozyme), and a reaction between SPIONs and peroxides was regarded as highly stable in various pH conditions and temperatures.
In this study, we report a nanozyme ability of the clustered SPIONs (CSPIONs) coated with biocompatible poly(lactic-co-glycolic acid) (PLGA) and the results based on colorimetric changes. The synthesized CPSIONs had an average size of 120.1 nm, zeta-potential (ζ-potential) of -61.7 mV (n=3), and the clustered shape was identified by taking transmission electron microscopy images. We hypothesize that the CSPIONs can have more catalytic effects toward H2O2 than single SPIONs not clustered. As a result, CSPIONs were shown to oxidize a 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) commonly used as a substrate for hydrogen peroxidase in the presence of H2O2, leading to a change the color of the substrate. We also utilized a colorimetric assay at 417 nm covering various glucose concentrations from 5 mM to 1.25 μM that considered the glucose condition of diabetes patients in physiological fluids. This study demonstrated that the absorbance value increases along with increasing the glucose level. It suggests that the particles can detect the glucose after SPIONs were clustered. The results were highly repeated at concentrations below 5 mM (standard deviations were presented as < 0.03). Moreover, the sensitivity and limit of detection (LOD) were 1.50 and 5.44 μM, respectively, indicating CSPIONs are more responsive to glucose compared to the SPIONs crystals.
In conclusion, this study proposes that glucose can be detected more sensitive in vitro when SPIONs are clustered. The CSPIONs have the potential to be used for glucose detection in diabetic patients using a physiological fluid such as ocular, saliva, and urine.
Altered electrochemical properties of iron oxide nanoparticles by carbon enhance molecular biocompatibility through discrepant atomic interaction