Bactericidal and Antiviral Bionic Metalized Nanocoatings

Nanofibers and Nanotextured Materials: Design Insights, Bactericidal Mechanisms and Environmental Advances

Antibiotic resistance is rising and poses a serious threat to human health on a worldwide scale. It can make it more difficult to cure common infections, raise medical expenditures, and increase mortality. In order to combat the development of biofilms and treat fatal bacterial infections, multifunctional polymeric nanofibers or nanotextured materials with specific structural features and special physiochemical capabilities have become a crucial tool. Due to the increased antibiotic resistance of many diseases, nanofibers with antibacterial activity are essential. Electrospinning is a flexible process able to produce fine fibers with specified properties by modifying variables such as the concentration of the solution, the feed flow, and the electric voltage. Substantial advancements have been made regarding the formation of nanofibers or nanotextured materials for a variety of applications, along with the development of electrospinning techniques in recent years. Using well-defined antimicrobial nanoparticles, encapsulating traditional therapeutic agents, plant-based bioactive agents, and pure compounds in polymer nanofibers has resulted in outstanding antimicrobial activity and has aided in curing deadly microbial infections. A plethora of studies have revealed that electrospinning is an effective technique for the production of antimicrobial fibers for the environmental, biomedical, pharmaceutical, and food sectors. Nevertheless, numerous studies have also demonstrated that the surface characteristics of substrates, such as holes, fibers, and ridges at the nanoscale, have an impact on cell proliferation, adhesion, and orientation.

Efficient Anti-Fog and Anti-Reflection Functions of the Bio-Inspired, Hierarchically-Architectured Surfaces of Multiscale Columnar Structures

Today, in the fields of optical precision instruments, medical devices, and automotive engineering, the demand for anti-reflection and anti-fog surfaces is growing rapidly. However, the anti-fog function often compromises the efficiency of the anti-reflection function. Therefore, optical precision instruments are always restricted by the inability to combine high anti-reflection efficiency and excellent anti-fog performance into one material. In addition, the synergistic mechanism of harmonizing anti-fogging and anti-reflection is currently unclear, which has a negative impact on the development and optimization of multifunctional surfaces. Herein, bio-inspired anti-fogging and anti-reflection surfaces (BFRSs) possessing multiscale hierarchical columnar structures (MHCS) were obtained using a brief and effective preparation technique, combining the biotemplating method and sol-gel method. Specifically, condensed fog droplets distributed on the BFRS can be absolutely removed within 6 s. In addition, the BFRSs endow the glass substrate with a relatively higher reflectance (17%) than flat glass surfaces (41%). Furthermore, we demonstrated the synergistic mechanism of the anti-fogging and anti-reflection functions of BFRSs. On the one hand, the high transparency benefits from the multiple refraction and scattering of light in the MHCS array. On the other hand, the excellent anti-fogging performance is attributed to the imbalance of the capillary force of the MHCS acting on the liquid film. The explanation for these two mechanisms provides more possibilities for the subsequent preparation of multifunctional surfaces. At the same time, the bionic research concept provides new solutions for the researcher to conquer the combination of high transmission and anti-fog properties for precision optical surfaces.

Optimization of Synthesis of Silver Nanoparticles Conjugated with Lepechinia meyenii (Salvia) Using Plackett-Burman Design and Response Surface Methodology—Preliminary Antibacterial Activity

In the present investigation, an ethanolic fraction (EF) of Lepechinia meyenii (salvia) was prepared and fractionated by gradient column chromatography, and the main secondary metabolites present in the EF were identified by HPLC-MS. Silver nanoparticles (AgNPs) were synthesized and conjugated with the EF of Lepechinia meyenii (salvia). The AgNPs synthesis was optimized using Plackett-Burman design and response surface methodology (RSM), considering the following independent variables: stirring speed, synthesis pH, synthesis time, synthesis temperature and EF volume. The AgNPs synthesized under the optimized conditions were characterized by UV visible spectroscopy (UV-VIS), Fourier Transform Infrared Spectroscopy (FT-IR), Dynamic Light Scattering (DLS) and Scanning Transmission Electron Microscopy (STEM). The antibacterial activity of the AgNPs against Staphylococcus aureus (ATCC® 25923) was evaluated. The following flavonoids were identified: rosmarinic acid, diosmin and hesperetin-7-O-rutinoside. The optimized conditions for the synthesis of nanoparticles were pH 9.45, temperature 49.8 °C, volume of ethanolic fraction 152.6 µL and a reaction time of 213.2 min. The obtained AgNPs exhibited an average size of 43.71 nm and a resonance plasmon of 410–420 nm. Using FT-IR spectroscopy, the disappearance of the peaks between 626.50 and 1379.54 cm−1 was evident with the AgNPs, which would indicate the participation of these functional groups in the synthesis and protection of the nanoparticles. A hydrodynamic size of 47.6 nm was obtained by DLS, while a size of 40–60 nm was determined by STEM. The synthesized AgNPs conjugated with the EF showed a higher antibacterial activity than the EF alone. These results demonstrate that the AgNPs synthesized under optimized conditions conjugated with the EF of the Lepechinia meyenii (salvia) presented an increased antibacterial activity.