The biodegradation of therapeutic magnetic-oxide nanoparticles (MONPs) in the human body raises concerns about their lifespan, functionality, and health risks. Interactions between apoferritin proteins and MONPs in the spleen, liver, and inflammatory macrophages significantly accelerate nanoparticle degradation, releasing metal ions taken up by apoferritin. This can alter the protein’s biological structure and properties, potentially causing health hazards. This study examines changes in apoferritin’s shape, electrical surface potential (ESP), and protein-core composition after incubation with cobalt-ferrite (CoFe₂O₄) oxide nanoparticles. Using atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM), we observed changes in the topography and ESP distribution in apoferritin nanofilms over time. After 48 h, the characteristic apoferritin hole (∼1.35 nm) vanished, and the protein’s height increased from ∼3.5 to ∼7.5 nm due to hole filling. This resulted in a significant ESP increase on the filled-apoferritin surface, attributed to the formation of a heterogeneous chemical composition and crystal structure (γ-Fe₂O₃, Fe₃O₄, CoO, CoOOH, FeOOH, and Co₃O₄). These changes enhance electrostatic interactions and surface charge between the protein and the AFM tip. This approach aids in predicting and improving the MONP lifespan while reducing their toxicity and preventing apoferritin deformation and dysfunction.

The last two decades have witnessed the emergence of micro- and nanoswimmers (MNSs). Researchers have invested significant efforts in engineering motile micro- and nanodevices to address current limitations in minimally invasive medicine. MNSs can move through complex fluid media by using chemical fuels or external energy sources such as magnetic fields, ultrasound, or light. Despite significant advancements in their locomotion and functionalities, the gradual deterioration of MNSs in human physiological media is often overlooked. Corrosion and biodegradation caused by chemical reactions with surrounding medium and the activity of biological agents can significantly affect their chemical stability and functional properties during their lifetime performance. It is therefore essential to understand the degradation mechanisms and factors that influence them to design ideal biomedical MNSs that are affordable, highly efficient, and sufficiently resistant to degradation (at least during their service time). This review summarizes recent studies that delve into the physicochemical characteristics and complex environmental factors affecting the corrosion and biodegradation of MNSs, with a focus on metal-based devices. Additionally, different strategies are discussed to enhance and/or optimize their stability. Conversely, controlled degradation of non-toxic MNSs can be highly advantageous for numerous biomedical applications, allowing for less invasive, safer, and more efficient treatments.

Functional oxide nanoparticles are extensively utilized in the last decades for biomedical purposes due to their unique functional properties. Nevertheless, their biodegradation mechanism by biological species, particularly by proteins at oxide/protein interfaces, still remains limited. Here, a systematic approaches is provided to investigate electrochemical behavior, electronic properties, and biodegradation mechanism of cobalt ferrite (CFO) and cobalt ferrite-bismuth ferrite (CFO-BFO) core-shell nanoparticles in apoferritin-containing media. Scanning Kelvin probe force microscopy results indicate that the presence of a thin shell (≈5 nm) of BFO on CFO causes a significant increase in surface potential. The potentiodynamic polarization measurements in different solutions showed higher anodic current densities for both samples when decreasing pH and increasing apoferritin concentration. Notably, CFO-BFO exhibits lower anodic current densities than CFO due to a slightly higher flat band potential and lower donor density distribution on CFO-BFO than on CFO, which results in lower electrochemical activity. Long-term monitoring reveals that biodegradation of both nanoparticles is accelerated by high apoferritin concentrations and acidic media, resulting in the decrease of electrochemical potentials and impedance values, and enhancement of metal ion release. Thus, this systematic biodegradation study can help to predict the lifespan and toxicity of these functional nanoparticles in biological environments.

The formation of a protein nanobiofilm on the surface of degradable biomaterials such as magnesium (Mg) and its alloys influences metal ion release, cell adhesion/spreading, and biocompatibility. During the early stage of human body implantation, competition and interaction between inorganic species and protein molecules result in a complex film containing Mg oxide and a protein layer. This film affects the electrochemical properties of the metal surface, the protein conformational arrangement, and the electronic properties of the protein/Mg oxide interface. In this study, we discuss the impact of various simulated body fluids, including sodium chloride (NaCl), phosphate-buffered saline (PBS), and Hanks' solutions on protein adsorption, electrochemical interactions, and electrical surface potential (ESP) distribution at the adsorbed protein/Mg oxide interface. After 10 min of immersion in NaCl, atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) showed a higher surface roughness related to enhanced degradation and lower ESP distribution on a Mg-based alloy than those in other solutions. Furthermore, adding bovine serum albumin (BSA) to all solutions caused a decline in the total surface roughness and ESP magnitude on the Mg alloy surface, particularly in the NaCl electrolyte. Using SKPFM surface analysis, we detected a protein nanobiofilm (∼10-20 nm) with an aggregated and/or fibrillary morphology only on the Mg surface exposed in Hanks' and PBS solutions; these surfaces had a lower ESP value than the oxide layer.

In previous work, the importance of taking the time-domain into account when studying corrosion inhibitor-containing electrochemical systems was highlighted. In this work, odd random phase electrochemical impedance spectroscopy (ORP-EIS) is applied as the electrochemical tool to study the time-effect by the evaluation of the non-stationarities per frequency decade over time for the screening of different silica- and phosphate- based corrosion inhibitors for hot-dip galvanized steel and possible corrosion inhibitor synergism. This serves as the basis for the interpretation of the results obtained from different macroscopic electrochemical techniques such as potentiodynamic polarization (PP), open circuit potential (OCP) with superimposed linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) measurements. The analysis of the time-domain shows that all systems have a system-specific ‘stabilization’ time which affects the interpretation of the results obtained from the macroscopic electrochemical techniques. Furthermore, these results indicate that all corrosion inhibitors tested exhibit corrosion protective action and that the combination of both silica-based corrosion inhibitors show synergistic action on hot-dip galvanized steel.

In this paper, different macroscopic electrochemical techniques are applied to study the corrosion inhibitor efficiency, protection mechanism and stability of a calcium aluminum polyphosphate silicate hydrate inhibitor on hot-dip galvanized steel in the time-domain. Potentiodynamic polarization (PP) measurements are applied to study the anodic and cathodic mechanistic behavior as well as inhibitor efficiencies at discrete and single times of exposure. Open circuit potential (OCP) with superimposed linear polarization resistance (LPR) measurements are applied as a faster, non-invasive alternative to PP, characterizing the overall performance of the system in terms of the polarization resistance. Electrochemical impedance spectroscopy (EIS) measurements are applied to detail both the overall performance of the system as well as the corrosion inhibition mechanism related to the electrochemical system’s physicochemical representation over time. Electrochemical noise (EN) measurement are used to evaluate the inhibition efficiency as a function of exposure time, represented by the electrochemical noise resistance. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the system’s instability, by evaluation of the non-linearities and non-stationarities over time. The non-stationarities present in the inhibitor-containing electrochemical system are shown to cause the overall instability of the system and should be taken into account when interpreting results from the different techniques over time.