The Effect of Physiological Incubation on the Properties of Elastic Magnetic Composites for Soft Biomedical Sensors

Magnetic micro- and nanoparticles (MPs)-based composite materials are widely used in various applications in electronics, biotechnology, and medicine. This group of silicone composites have advantageous magnetic and mechanical properties as well as sufficient flexibility and biocompatibility. These composites can be applied in medicine for biological sensing, drug delivery, tissue engineering, and as remote-controlled microrobots operating in vivo. In this work, the properties of polydimethylsiloxane (PDMS)-based composites with different percentages (30 wt.%, 50 wt.%, 70 wt.%) of NdFeB microparticles as a filler were characterized. The novelty of the work was to determine the influence of the percentage of MP content and physiological conditioning on the properties of the PDMS-MP composites after in vitro incubation. An important essence of the work was a comprehensive study of the properties of materials important from the point of view of medical applications. Materials were tested before and after conditioning in 0.9 wt.% NaCl solution at a temperature of 37 °C. Several studies were carried out, including thermal, physicochemical, and rheological tests. The results show that with an increase of the incubation time, most of the measured thermal and physicochemical parameters decreased. The presence of the magnetic filler, especially at a concentration of 70 wt.%, has a positive effect on thermal stability and physicochemical and rheological properties. The performed tests provided important results, which can lead to further research for a broader application of magnetic composites in the biomedical field

Effect of Saliva and Mucin-Based Saliva Substitutes on Fretting Processes of 316 Austenitic Stainless Steel

The paper presents the results of research of the fretting process of 316 austenitic stainless steel in the environment of natural saliva and mucin-based saliva preparations. The aim of the work was the evaluation of synthetic saliva preparations on biomaterial wear during fretting and fretting-corrosion. The fretting process, in the oscillatory micro-movements conditions, occurs in the joints of removable dentures, especially during the chewing phase. Fretting usually leads to the intensification of fatigue damage processes of materials. Experimental research, through rheological, fretting, fretting-corrosion, and microscopic analysis were performed. Tests indicate that natural saliva and saliva preparations are similar in terms of viscoelastic properties. The statistically significant proposed saliva solutions reduced the material wear in comparison to dry sliding, which is important in the case of people with saliva secretion problem. The addition of xanthan gum to the artificial saliva composition improved rheological characteristics, but on the other hand, led to an increase of secondary wear. It was confirmed by the volumetric wear of the samples and evaluation of energy dissipated during friction. Fretting-corrosion processes were explained by a mechanism related to crevice corrosion supported by friction

Chemical stability assessment of soft magnetic composites for biomedical applications

Silicone-based elastic composites with a metallic filler have been strongly developed in recent years. These materials are considered applicable in many fields of science, including medicine. The advantageous mechanical parameters provided by the NdFeB micropowder reinforcement are balanced by the elasticity and biocompatibility guaranteed by the silicone matrix. So far, there have been several reports regarding such composites’ properties important from the biomedical point of view. The article deals with the physicochemical parameters of the new material for medical applications as well as the properties of the incubation liquid. The aim of the work was to determine effects of both the magnetic particles content (0, 30, 50, 70 wt%) and the incubation process under physiological conditions on the physicochemical properties of the material and the solution after incubation. The samples were incubated for various periods of time (8, 16 and 24 weeks) at the temperature of 37°C in a 0.9 wt% NaCl solution. The density, water contact angle, and water absorption of the materials were measured. The electrolytic conductivity, pH value, redox potential, surface tension, and kinematic viscosity were determined for the liquids after the materials incubation. The results obtained for pure silicone and the silicone-based composite reinforced with NdFeB microparticles were compared. The results indicate that incubation affects the samples and liquids, changing their physiochemical properties. For composites, the density decreased, which results in a noticeable concentration of the examined elements in the solutions

Degradation of Polylactide and Polycaprolactone as a Result of Biofilm Formation Assessed under Experimental Conditions Simulating the Oral Cavity Environment

Polylactide (PLA) and polycaprolactone (PCL) are biodegradable and bioabsorbable thermoplastic polymers considered as promising materials for oral applications. However, any abiotic surface used, especially in areas naturally colonized by microorganisms, provides a favorable interface for microbial growth and biofilm development. In this study, we investigated the biofilm formation of C. krusei and S. mutans on the surface of PLA and PCL immersed in the artificial saliva. Using microscopic (AFM, CLSM) observations and spectrometric measurements, we assessed the mass and topography of biofilm that developed on PLA and PCL surfaces. Incubated up to 56 days in specially prepared saliva and microorganisms medium, solid polymer samples were examined for surface properties (wettability, roughness, elastic modulus of the surface layer), structure (molecular weight, crystallinity), and mechanical properties (hardness, tensile strength). It has been shown that biofilm, especially S. mutans, promotes polymer degradation. Our findings indicate the need for additional antimicrobial strategies for the effective oral applications of PLA and PCL

Case Report: Heart aneurysm of unknown origin in a two-year-old child diagnosed in the course of Multisystem Inflammatory Syndrome in Children

We present a case of a 22-month-old boy with a hypokinetic and thin-walled aneurysm of the left ventricle apex. The lesion was diagnosed during routine echocardiography examination in the course of MIS-C, and its occurrence due to MIS-C is plausible. Cardiac magnetic resonance imaging revealed an akinetic aneurysm of the LV apex with a full-wall ischemic scar. Aortography confirmed a normal course of coronary arteries, with adequate perfusion of essential branches and no evidence of stenosis or aneurysms. The boy underwent consultation with the heart team and was deemed eligible for surgery. The aneurysm was excised up to the margin of healthy tissues, and both the surgery and the periprocedural period were uneventful. Determining the origin of the aneurysm is challenging. The most probable etiology appears to be a congenital lesion. Another consideration is an ischemic lesion that may have resulted from impaired coronary circulation during the complicated course of MIS-C. It is possible that this disturbance resolved spontaneously before aortography was performed. Additionally, a complication of pericarditis cannot be entirely ruled out

The Role of Oral Cavity Biofilm on Metallic Biomaterial Surface Destruction–Corrosion and Friction Aspects

Metallic biomaterials in the oral cavity are exposed to many factors such as saliva, bacterial microflora, food, temperature fluctuations, and mechanical forces. Extreme conditions present in the oral cavity affect biomaterial exploitation and significantly reduce its biofunctionality, limiting the time of exploitation stability. We mainly refer to friction, corrosion, and biocorrosion processes. Saliva plays an important role and is responsible for lubrication and biofilm formation as a transporter of nutrients for microorganisms. The presence of metallic elements in the oral cavity may lead to the formation of electro-galvanic cells and, as a result, may induce corrosion. Transitional microorganisms such as sulfate-reducing bacteria may also be present among the metabolic microflora in the oral cavity, which can induce biological corrosion. Microorganisms that form a biofilm locally change the conditions on the surface of biomaterials and contribute to the intensification of the biocorrosion processes. These processes may enhance allergy to metals, inflammation, or cancer development. On the other hand, the presence of saliva and biofilm may significantly reduce friction and wear on enamel as well as on biomaterials. This work summarizes data on the influence of saliva and oral biofilms on the destruction of metallic biomaterials