A reliable protocol for colorimetric determination of iron oxide nanoparticle uptake by cells

Abstract

Size, shape, and surface properties of superparamagnetic iron oxide nanoparticles (SPIONs) can influence their interaction with biological systems, particularly the incorporation by tumor cells and consequently the biological activity and efficiency in biomedical applications. Several strategies have been used to evaluate cellular uptake of SPIONs. While qualitative methods are generally based on microscopy techniques, quantitative assays are carried out by techniques such as inductively coupled plasma-mass spectrometry and flow cytometry. However, inexpensive colorimetric methods based on equipments commonly found in chemistry and biochemistry laboratories are preferred for routine measurements. Nevertheless, colorimetric assays must be used judiciously, particularly when nanoparticles are involved, since their interaction with biological constituents tends to lead to quite underestimated results. Thus, herein described is a colorimetric protocol using 2,2'-bipyridine as chromogenic ligand, where each step was optimized and validated by total reflection X-ray fluorescence spectroscopy, realizing a highly reproducible and reliable method for determination of iron content in cells incubated with SPIONs. The limit of blank and limit of detection were determined to be as low as 0.076 and 0.143 μg Fe/mL, using sample volumes as small as 190 μL and a number of cells as low as 2.0 × 10. Furthermore, three different types of surface-functionalized nanoparticles were incorporated in cells and evaluated through this protocol, enabling to monitor the additive effect of o-phosphorylethanolamine (PEA) and folic acid (FA) conjugation on iron oxide nanoparticles (SPION-PEA and SPION-PEA/FA), that enhanced the uptake by HeLa cells, respectively, by four and ten times when compared to SPIONs conjugated with nonbioactive molecules. Graphical abstract Colorimetric determination of superparamagnetic iron oxide nanoparticles (SPIONs) incorporated by cells.

Magnetism and Afterglow United: Synthesis of Novel Double Core–Shell Eu2+‐Doped Bifunctional Nanoparticles

“…The excitation spectrum of Fe 3 O 4 @SiO 2 @SrAl 2 O 4 :Eu 3+ ,Dy 3+ is composed of a broad band distributed from about 30 000 cm −1 with a maximum at around 40 000 cm −1 (Figure a, blue curve). This behavior of the excitation spectrum of Fe 3 O 4 @SiO 2 @SrAl 2 O 4 :Eu 3+ ,Dy 3+ agrees with that reported for SrAl 2 O 4 :Eu 3+ by Sahu et al., in which the excitation band at approximately 39 000 cm −1 is assigned to the charge‐transfer state (CTS) caused by the electron transfer from an oxygen 2p orbital to an empty 4f shell of europium. This broad band largely overcomes the peaks between 18 000 and 32 000 cm −1 , which originate from the electronic transitions of trivalent europium, indicating an efficient energy‐transfer process between the CT state and the 5 D 0 → 7 F J transitions of Eu 3+ …”

Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy

“…The study of trace elements and their functions in living organisms and biological systems requires methods to study metals in cells or tissues [205]. This requirement has spawned the field of metallomics [206] and is providing great insight into the biodistribution of metals in the body to understand biomolecular metal regulation, metal accumulation, and abnormalities that could be indicative of a diseased state [201].…”

Applications of superparamagnetic iron oxide nanoparticles in drug and therapeutic delivery, and biotechnological advancements

“…6 nm) in cell lysates down to tens of nanograms (76 ng/mL Fe or 1.36 μM). This new method added to the qualitative and semi-quantitative methods for detecting and measuring iron content stands as proof for the use of SPIONs in biomedical purposes [ 164 ].…”