Surfaces, Volume 4, Issue 4 (December 2021) – 8 articles

Catecholamines are an important class of neurotransmitters responsible for regularizing, controlling, and treating neural diseases. Based on control and diseases treatment, the development of methodology and dives to sensing is a promissory technology area. This work evaluated the role of iron phthalocyanine coordination (FePc) with the specific groups from catecholamine molecules (L-dopa, dopamine, epinephrine, and the amino acid tyrosine) and the effect of this coordination on electrochemical behavior. The in situ coordination analysis was performed through isotherms π-A of FePc Langmuir films in the absence and presence of catecholamines. The π-A isotherm indicates a strong interaction between FePc monolayer and L-Dopa and DA, which present a catechol group and a side chain with a protonated amino group (-NH₃⁺). These strong interactions with catechol and amine groups were confirmed by characterization at the molecular level using the surface-enhanced Raman spectroscopy (SERS) from a Langmuir–Schaefer monolayer deposited onto Ag surfaces. The electrochemical measurements present a similar tendency, with lower oxidation potential observed to DA>L-Dopa>Ep. The results corroborate that the coordination of the analyte on the electron mediator surface plays an essential role in an electrochemical sensing application. The FePc LS film was applied as a sensor in tablet drug samples, showing a uniformity of content of 96% for detecting active compounds present in the L-Dopa drug samples. Full article

Transparent, flexible, biaxially oriented polyethylene terephthalate (PET) sheets were modified by bioactive polymer-fibronectin top layers for the attachment of cells and growth of muscle fibers. Towards this end, PET sheets were grafted with 4-(dimethylamino)phenyl (DMA) groups from the in situ generated diazonium cation precursor. The arylated sheets served as macro-hydrogen donors for benzophenone and the growth of poly(2-hydroxy ethyl methacrylate) (PHEMA) top layer by surface-confined free radical photopolymerization. The PET-PHEMA sheets were further grafted with fibronectin (FBN) through the 1,1-carbonyldiimidazole coupling procedure. The bioactive PET-PHEMA-I-FBN was then employed as a platform for the attachment, proliferation and differentiation of eukaryotic cells which after a few days gave remarkable muscle fibers, of ~120 µm length and ~45 µm thickness. We demonstrate that PET-PHEMA yields a fast growth of cells followed by muscle fibers of excellent levels of differentiation compared to pristine PET or standard microscope glass slides. The positive effect is exacerbated by crosslinking PHEMA chains with ethylene glycol dimethacrylate at initial HEMA/EGDA concentration ratio = 9/1. This works conclusively shows that in situ generated diazonium salts provide aryl layers for the efficient UV-induced grafting of biocompatible coating that beneficially serve as platform for cell attachment and growth of muscle fibers. Full article

Naringenin (4′,5,7-trihydroxyflavanone-7-rhamnoglucosideor naringenin-7-rhamnoglucoside), a flavonoid present in large quantities in citrus, has different beneficial effects on human health as an antioxidant, free radical scavenger, anti-inflammatory, carbohydrate metabolism promoter, and immune system modulator. Different studies have shown that this substance also has a hypoglycemic and antihypertensive effect, reduces cholesterol and triglycerides, and plays an important protective role in the heart tissue; moreover, it provides neuroprotection against various neurological disorders such as Parkinson’s disease and unpredictable chronic stress-induced depression. Despite these advantages, Naringenin is poorly absorbed, and the small percentage absorbed is rapidly degraded by the liver, as a result losing its activity. Several approaches have been attempted to overcome these obstacles, among them, nanotechnology, with the use of Drug Delivery Systems (DDS) as Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC). DDS can, in fact, improve the drug bioavailability. The aim of this study was to develop and characterize SLN and NLC containing Naringenin and to evaluate the ability of these nanoparticles to release Naringenin at the cell level using biomembrane models represented by Multilamellar Vesicles (MLV). These studies were performed using Differential Scanning Calorimetry, a powerful technique to detect the interaction of drugs and delivery systems with MLV. It was shown that Naringenin could be better incorporated into NLC with respect to SLN and that Naringenin could be released by NLC into the biomembrane model. Therefore, suggesting the administration of Naringenin loaded into nanoparticles could help avoid the disadvantages associated with the use of the free molecule. Full article

Dimethyl-organotin(IV) valsartan (Me₂SnL₂) and dichlorostannanediyl valsartan (SnL₂Cl₂) complexes were synthesized, characterized, and applied as Poly(vinyl chloride) (PVC) photo-stabilizers. The complexes were loaded within the PVC films in a weight ratio of 0.5%, and the modified films were irradiated to a UV light of 313 nm wavelength for 300 h at room temperature. The efficiency of the complexes-filled films was compared with the plain one and evaluated before and after irradiation by Fourier transform infrared spectroscopy, weight loss, gel content, change in viscosity, atomic force microscopy, and field emission scanning electron microscopy. The SnL₂Cl₂ complex had higher activity than the Me₂SnL₂ complex to retard the PVC’s photodegradation by several mechanisms. Full article

Mn_xZn_1−xO thin films (x = 0%, 1%, 3%, and 5%) were grown on corning glass substrates using sol–gel technique. Single-phase hexagonal wurtzite structure was confirmed using X-ray diffraction. Raman analysis revealed the presence of Mn content with an additional vibrational mode at 570 cm⁻¹. The surface morphology of the samples was observed by scanning electron microscopy which suggested that the grain size increases with an increase in Mn concentration. The optical bandgap increases with increasing Mn concentration due to a significant blueshift in UV–visible absorption spectra. The alteration of the bandgap was verified by the I–V measurements on ZnO and Mn-ZnO films. The various functional groups in the thin films were recorded using FTIR analysis. Magnetic measurements showed that Mn_xZn_1−xO films are ferromagnetic, as Mn induces a fully polarised state. The effect of Mn²⁺ ions doping on Mn_xZn_1−xO thin films was investigated by extracting various parameters such as lattice parameters, energy bandgap, resistivity, and magnetisation. The observed coercivity is about one-fifth of the earlier published work data which indicates the structure is soft in nature, having less dielectric/magnetic loss, and hence can be used as ultra-fast switching in spintronic devices. Full article

Low Infrared emissivity coating (LIREC) is prone to generating some problems such as bulges, degumming, and abrasion. In order to study whether the performance of LIREC under different damages can meet the work needs, it is essential to timely measure and evaluate the performance state of LIREC in the application process. The existing methods for measuring the damage of LIREC have some disadvantages such as expensive equipment, complex operation, and inaccurate measurement results. In this paper, a measurement method of LIREC damage capability based on thermal imager is proposed. The radiation temperature is measured by thermal imager, the real temperature and ambient temperature of coating surface are measured by thermocouple, and the emittance of coating surface is calculated. Non-contact and continuous large-area emissivity measurements are carried out on the damaged parts of the coating and verified by experiments. The measurement results show that the different damage types and damage degrees directly affect the measurement results of LIREC. Wear damage increases the emissivity of the coating while debonding damage basically does not change the coating emissivity. Shedding damage of small diameter forms voids, which causes the increase of the damage parts of emittance. In addition, bulge damage impedes temperature transfer and reduces emissivity. This method can timely and accurately measure and evaluate the performance state of LIREC and can provide a new idea for the accurate measurement of damage emissivity of LIREC. Full article