Selenium Silk Nanostructured Films with Antifungal and Antibacterial Activity

The rapid emergence of drug-resistant bacteria and fungi poses a threat for healthcare worldwide. The development of novel effective small molecule therapeutic strategies in this space has remained challenging. Therefore, one orthogonal approach is to explore biomaterials with physical modes of action that have the potential to generate antimicrobial activity and, in some cases, even prevent antimicrobial resistance. Here, to this effect, we describe an approach for forming silk-based films that contain embedded selenium nanoparticles. We show that these materials exhibit both antibacterial and antifungal properties while crucially also remaining highly biocompatible and noncytotoxic toward mammalian cells. By incorporating the nanoparticles into silk films, the protein scaffold acts in a 2-fold manner; it protects the mammalian cells from the cytotoxic effects of the bare nanoparticles, while also providing a template for bacterial and fungal eradication. A range of hybrid inorganic/organic films were produced and an optimum concentration was found, which allowed for both high bacterial and fungal death while also exhibiting low mammalian cell cytotoxicity. Such films can thus pave the way for next-generation antimicrobial materials for applications such as wound healing and as agents against topical infections, with the added benefit that bacteria and fungi are unlikely to develop antimicrobial resistance to these hybrid materials.

Bioinspired Antimicrobial Coatings from Peptide-Functionalized Liquid Crystalline Nanostructures

Surface-associated microbial infections and contaminations are a major challenge in various fields including the food and health sectors. This study demonstrates the design of antimicrobial coatings based on the self-assembly of the food-grade amphiphilic lipid glycerol monooleate with the human cathelicidin-derived antimicrobial peptide LL-37. Structural properties of the coating and their alterations with composition were studied using advanced experimental methods including synchrotron grazing-incidence small-angle X-ray scattering and ellipsometry. The integration of the LL-37 and its potential release from the nanostructured films into the surrounding solution was characterized with confocal Raman microscopy. Additional biological evaluation studies with clinically relevant bacterial strains, namely, Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive), were performed to investigate the antimicrobial activity of the coatings. Significant killing activity of the coating was found against both bacterial strains. The presented findings contribute to the fundamental understanding of lipid-peptide self-assembly on the surface and may open up a promising strategy for designing simple, sustainable antimicrobial coatings for medical and food applications.

Relation between thickness, crystallite size and magnetoresistance of nanostructured La1- x Sr x Mn y O3±δ films for magnetic field sensors

In the present study the advantageous pulsed-injection metal organic chemical vapour deposition (PI-MOCVD) technique was used for the growth of nanostructured La_{1- x} Sr _x Mn _y O_3±δ (LSMO) films on ceramic Al₂O₃ substrates. The compositional, structural and magnetoresistive properties of the nanostructured manganite were changed by variation of the processing conditions: precursor solution concentration, supply frequency and number of supply sources during the PI-MOCVD growth process. The results showed that the thick (≈400 nm) nanostructured LSMO films, grown using an additional supply source of precursor solution in an exponentially decreasing manner, exhibit the highest magnetoresistance and the lowest magnetoresistance anisotropy. The possibility to use these films for the development of magnetic field sensors operating at room temperature is discussed.

Linear Birefringent Films of Cellulose Nanocrystals Produced by Dip-Coating

Transparent films of cellulose nanocrystals (CNC) are prepared by dip-coating on glass substrates from aqueous suspensions of hydrolyzed filter paper. Dragging forces acting during films’ deposition promote a preferential alignment of the rod-shaped CNC. Films that are 2.8 and 6.0 µm in thickness show retardance effects, as evidenced by placing them between a linearly polarized light source and a linear polarizer sheet in the extinction configuration. Transmission Mueller matrix spectroscopic ellipsometry measurements at normal incidence as a function of sample rotation were used to characterize polarization properties. A differential decomposition of the Mueller matrix reveals linear birefringence as the unique polarization parameter. These results show a promising way for obtaining CNC birefringent films by a simple and controllable method.

Controlled Film Architectures to Detect a Biomarker for Pancreatic Cancer Using Impedance Spectroscopy

The need for analytical devices for detecting cancer at early stages has motivated research into nanomaterials where synergy is sought to achieve high sensitivity and selectivity in low-cost biosensors. In this study, we developed a film architecture combining self-assembled monolayer (SAM) and layer-by-layer (LbL) films of polysaccharide chitosan and the protein concanavalin A, on which a layer of anti-CA19-9 antibody was adsorbed. Using impedance spectroscopy with this biosensor, we were capable of detecting low concentrations of the antigen CA19-9, an important biomarker for pancreatic cancer. The limit of detection of 0.69U/mL reached is sufficient for detecting pancreatic cancer at very early stages. The selectivity of the biosensor was inferred from a series of control experiments with samples of cell lines that were tested positive (HT29) and negative (SW620) for the biomarker CA19-9, in addition to the lack of changes in the capacitance value for other analytes and antigen that are not related to this type of cancer. The high sensitivity and selectivity are ascribed to the very specific antigen-antibody interaction, which was confirmed with PM-IRRAS and atomic force microscopy. Also significant is that used information visualization methods to show that different cell lines and commercial samples containing distinct concentrations of CA19-9 and other analytes can be easily distinguished from each other. These computational methods are generic and may be used in optimization procedures to tailor biosensors for specific purposes, as we demonstrated here by comparing the performance of two film architectures in which the concentration of chitosan was varied.

Supramolecular Control in Nanostructured Film Architectures for Detecting Breast Cancer

The need for early detection of various diseases, including breast cancer, has motivated research into nanomaterials that can be assembled in organized films which serve as biosensors. Owing to the variety of possible materials and film architectures, procedures are required to design optimized biosensors. In this study, we combine surface-specific methods to monitor the assembly of antibodies on nanostructured films with two distinct architectures. In the first, a layer of the antibody type mouse anti-HER2 (clone tab250) was immobilized on a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid modified with N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (EDC). In the second approach, a SAM of cysteamine was coated with a biotin/spreptavidin bilayer on which a layer of biotinylated antibody type MSx2HUp185/her biotin was adsorbed. The rougher, less passivating coating with cysteamine determined from cyclic voltammetry and scanning electron microscopy led to biosensors that are more sensitive to detect the breast cancer ERBB2 (HER2) biomarker in impedance spectroscopy measurements. This higher distinguishing ability of the cysteamine-containing film architecture was proven with information visualization methods to treat the impedance data. Polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) confirmed that biosensing resulted from the antibody-ERBB2 antigen affinity.