Smart Coatings Prepared via MAPLE Deposition of Polymer Nanocapsules for Light-Induced Release

Biocompatible Hybrid Graphenic Thin Coatings on Flexible Substrates through Matrix-Assisted Pulsed Laser Evaporation (MAPLE)

This work reports the production of biocompatible thin layers for biomedical applications based on a graphene-like material (GL), a graphene-related material (GRM) obtained from carbon black. GL was combined in a hybrid fashion with polydopamine (pDA), a mussel-inspired water-resistant wet adhesive bonding obtained by the oxidative polymerization of dopamine (DA), and polyvinyl pyrrolidinone (PVP), a nontoxic synthetic polymer with intrinsic adhesion properties, to obtain a tighter adhesion of the thin layer to the substrate (silicone slices). Matrix-assisted pulsed laser evaporation (MAPLE) was used to coat PDMS slices with thin films of GL-pDA and GL-PVP directly from their frozen suspensions in water. The results indicate that the relevant chemical-physical characteristics of both thin films (evidenced by FTIR and AFM) were maintained after MAPLE deposition and that the films exhibit uniformity also at the nanometric level. After deposition, the GL-pDA and GL-PVP films underwent a biological survey toward murine fibroblasts (NIH3T3), human keratinocytes (HaCAT), and human cervical adenocarcinoma epithelial-like (HeLa) cells to assess the feasibility of this approach. Results indicate that both the GL-pDA and GL-PVP films did not perturb the biological parameters evaluated, including cytoskeleton alterations. Both hybrid films enhanced the effects of GL on cellular vitality across all cell lines. Specifically, the GL-pDA film exhibited a more stable effect over time (up to 72 h), whereas the GL-PVP film behaved similarly to the GL film in NIH3T3 and HeLa cell lines after long-term exposure. These promising results make the GL-pDA and GL-PVP films potential candidates for the manufacture of coated flexible devices for biomedical applications.

Surface pre-treatment of aluminum alloy for mechanical improvement of adhesive bonding by maple-assisted pulsed laser evaporation technique

Adhesive joints are widely used for structural bonding in various industrial sectors. The performance of bonded joints is commonly attributed to the cleanliness of the substrate and the pre-treatment of the surfaces to be bonded. In this study, the Matrix Assisted Pulsed Laser Evaporation (MAPLE) deposition technique was used for surface modification of aluminum (Al) plates by the deposition of poly(propylene glycol) bis(2-aminopropyl ether) (PPG-NH2) of different number average molecular weights (Mn) of 400 g mol-1, 2000 g mol-1, and 4000 g mol-1, respectively. Fourier-transformed infrared spectroscopy (FT-IR) analysis indicated the characteristic peaks for the deposited layers of PPG-NH2 of different molecular weights in all cases while scanning electron microscopy (SEM) revealed continuous layers on the surface of Al plates. In order to demonstrate alterations in the wettability of Al substrates, a crucial aspect in surface treatment and adhesive bonding, measurements of contact angles, surface free energies (SFE), and adhesion work (W a) were conducted. The tensile strength measurements were performed using the lap-joint test after applying the commercial silyl-based polymer adhesive Bison Max Repair Extreme Adhesive®. It was evidenced that at higher values of the SFE and W a, the tensile strength was almost 3 times higher for PPG-NH2 with Mn = 4000 g mol-1 compared with the untreated Al sample. This study provides valuable insights into the successful application of the MAPLE technique as a pre-treatment method for reinforcing adhesive bonding of Al plates, which can lead to improved mechanical performance in various industrial applications.

Nanostructured Coatings Based on Graphene Oxide for the Management of Periprosthetic Infections

To modulate the bioactivity and boost the therapeutic outcome of implantable metallic devices, biodegradable coatings based on polylactide (PLA) and graphene oxide nanosheets (nGOs) loaded with Zinforo™ (Zin) have been proposed in this study as innovative alternatives for the local management of biofilm-associated periprosthetic infections. Using a modified Hummers protocol, high-purity and ultra-thin nGOs have been obtained, as evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations. The matrix-assisted pulsed laser evaporation (MAPLE) technique has been successfully employed to obtain the PLA-nGO-Zin coatings. The stoichiometric and uniform transfer was revealed by infrared microscopy (IRM) and scanning electron microscopy (SEM) studies. In vitro evaluation, performed on fresh blood samples, has shown the excellent hemocompatibility of PLA-nGO-Zin-coated samples (with a hemolytic index of 1.15%), together with their anti-inflammatory ability. Moreover, the PLA-nGO-Zin coatings significantly inhibited the development of mature bacterial biofilms, inducing important anti-biofilm efficiency in the as-coated samples. The herein-reported results evidence the promising potential of PLA-nGO-Zin coatings to be used for the biocompatible and antimicrobial surface modification of metallic implants.

Silver/Graphene Oxide Nanostructured Coatings for Modulating the Microbial Susceptibility of Fixation Devices Used in Knee Surgery

Exploring silver-based and carbon-based nanomaterials' excellent intrinsic antipathogenic effects represents an attractive alternative for fabricating anti-infective formulations. Using chemical synthesis protocols, stearate-conjugated silver (Ag@C18) nanoparticles and graphene oxide nanosheets (nGOs) were herein obtained and investigated in terms of composition and microstructure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations revealed the formation of nanomaterials with desirable physical properties, while X-ray diffraction (XRD) analyses confirmed the high purity of synthesized nanomaterials. Further, laser-processed Ag@C18-nGO coatings were developed, optimized, and evaluated in terms of biological and microbiological outcomes. The highly biocompatible Ag@C18-nGO nanostructured coatings proved suitable candidates for the local modulation of biofilm-associated periprosthetic infections.

Coating of Flexible PDMS Substrates through Matrix-Assisted Pulsed Laser Evaporation (MAPLE) with a New-Concept Biocompatible Graphenic Material

In this study, matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit graphene-like materials (GL), a new class of biocompatible graphene-related materials (GRMs) obtained from a controlled top-down demolition of a carbon black, on silicone slices to test their potential use as functional coating on invasive medical devices as indwelling urinary catheters. Results indicate that the relevant chemical-physical features of the deposit (controlled by FTIR and AFM) were maintained after MAPLE deposition. After deposition, GL films underwent a biological survey toward target cellular lines (murine fibroblast NIH3T3, human keratinocytes HaCAT and the human cervical adenocarcinoma epithelial-like HeLa). Results indicate that the GL films did not lead to any perturbations in the different biological parameters evaluated. The presented results and the possibility to further functionalize the GL or combine them with other functional materials in a hybrid fashion to assure a tighter adhesion onto the substrate for use in harsh conditions open the door to practical applications of these new-concept medical devices (drug delivery, next generation flexible devices, multifunctional coatings) paving the way to the prevention of nosocomial infections driven by catheterization through antibiotics-free approaches.

Thermal Effect on Thin-Film Formation of the Polymer Sheets by the CO2 Laser with the Copper Base

A method that makes polymer sheets partially thinner with continuous-wave carbon dioxide (CO₂) lasers has been developed. This method can create thin polymer films by attaching the polymer sheets to the copper base by vacuum suction through the holes in the base. Applying the method to polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polytetrafluoroethylene (PTFE), the thin-film formation is confirmed in PP, PET, and PS but not PTFE. These polymers have the similar thermal properties. PP, PET, and PS show fluidity with increased temperature, but PTFE does not have fluidity. These characteristics of the polymers indicate that the fluidity of polymer is the important characteristic for film formation. The experiments with PP and PET sheets of different thickness show that thicker sheets make thicker films. The fluid flow of the molten polymer is considered to form the thin film at the bottom of the groove made by laser scribing. The numerical simulation of the 2D thermal model also indicates the week cooling effects of the base on the film formation and importance of polymer fluidity. The results of Fourier transform infrared spectrometer (FT-IR) show thermal degradation of the films. To decrease the heat’s effect on the films, the polymer sheets should be processed at the highest laser-beam scanning speed that can make thin films.

Composite Coatings for Osteoblast Growth Attachment Fabricated by Matrix-Assisted Pulsed Laser Evaporation

The bioactive and biocompatible properties of hydroxyapatite (HAp) promote the osseointegration process. HAp is widely used in biomedical applications, especially in orthopedics, as well as a coating material for metallic implants. We obtained composite coatings based on HAp, chitosan (CS), and FGF2 by a matrix-assisted pulsed laser evaporation (MAPLE) technique. The coatings were physico-chemically investigated by means of X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Infrared Microscopy (IRM), and Scanning Electron Microscopy (SEM). Further, biological investigations were performed. The MAPLE-composite coatings were tested in vitro on the MC3T3-E1 cell line in order to endorse cell attachment and growth without toxic effects and to promote pre-osteoblast differentiation towards the osteogenic lineage. These coatings can be considered suitable for bone tissue engineering applications that lack toxicity and promotes cell adhesion and proliferation while also sustaining the differentiation of pre-osteoblasts towards mature bone cells.

Polymeric Coatings and Antimicrobial Peptides as Efficient Systems for Treating Implantable Medical Devices Associated-Infections

Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action and minimum environmental toxicity. One approach in infection control is based on the development of antimicrobial coatings based on polymers and antimicrobial peptides, also termed as “natural antibiotics”.

PEG-Functionalized Magnetite Nanoparticles for Modulation of Microbial Biofilms on Voice Prosthesis

This study reports the fabrication of nanostructured coatings based on magnetite, polyethyleneglycol, and biologically active molecule (polymyxin B-PM) for producing biofilm-resistant surfaces (voice prosthesis). Magnetite nanoparticles (MNPs) have been synthesized and functionalized using a co-precipitation method and were further deposited into thin coatings using the matrix-assisted pulsed laser evaporation (MAPLE) technique. The obtained nanoparticles and coatings were characterized by X-ray diffraction (XRD), thermogravimetric analysis with differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM), transmission electron microscopy with selected area electron diffraction (TEM-SAED), Fourier-transform infrared spectroscopy (FT-IR), and infrared microscopy (IRM). Their antibiofilm activity was tested against relevant Staphylococcus aureus and Pseudomonas aeruginosa bacterial strains. The Fe₃O₄@PEG/PM surface of modified voice prosthesis sections reduced the number of CFU/mL up to four orders of magnitude in the case of S. aureus biofilm. A more significant inhibitory effect is noticed in the case of P. aeruginosa up to five folds. These results highlight the importance of new Fe₃O₄@PEG/PM in the biomedical field.

Bioactive Coatings Loaded with Osteogenic Protein for Metallic Implants

Osteoconductive and osteoinductive coatings represent attractive and tunable strategies towards the enhanced biomechanics and osseointegration of metallic implants, providing accurate local modulation of bone-to-implant interface. Composite materials based on polylactide (PLA) and hydroxyapatite (HAp) are proved beneficial substrates for the modulation of bone cells' development, being suitable mechanical supports for the repair and regeneration of bone tissue. Moreover, the addition of osteogenic proteins represents the next step towards the fabrication of advanced biomaterials for hard tissue engineering applications, as their regulatory mechanisms beneficially contribute to the new bone formation. In this respect, laser-processed composites, based on PLA, Hap, and bone morphogenetic protein 4(BMP4), are herein proposed as bioactive coatings for metallic implants. The nanostructured coatings proved superior ability to promote the adhesion, viability, and proliferation of osteoprogenitor cells, without affecting their normal development and further sustaining the osteogenic differentiation of the cells. Our results are complementary to previous studies regarding the successful use of chemically BMP-modified biomaterials in orthopedic and orthodontic applications.

Biofilm-Resistant Nanocoatings Based on ZnO Nanoparticles and Linalool

Biofilms represent an increasing challenge in the medical practice worldwide, imposing a serious threat to public health. As bacterial strains have developed antibiotic resistance, researcher’s attention has been extensively focused on developing more efficient antimicrobial strategies. In this context, the present study reports the synthesis, physicochemical characterization, ex vivo biodistribution, and in vitro evaluation of the capacity of nanostructured surfaces based on zinc oxide (ZnO) and biologically active molecules to modulate clinically relevant microbial biofilms. ZnO nanoparticles (NPs) were synthesized through a co-precipitation method without thermal treatment. The matrix-assisted pulsed laser evaporation (MAPLE) was applied for preparing nanostructured coatings based on ZnO NPs surface modified with linalool that were further characterized by X-ray diffraction (XRD), thermogravimetric analysis with differential scanning calorimetry (TGA-DSC), scanning electron microscopy (SEM), transmission electron microscopy with selected area electron diffraction (TEM-SAED), Fourier-transform infrared spectroscopy (FT-IR), and infrared microscopy (IRM). Histological analyses carried out at 7 days and 14 days after the intraperitoneal administration of linalool modified ZnO NPs revealed the absence of the latter from the brain, kidney, liver, lung, myocardium, and pancreas. Through in vitro assays on prokaryotic cells, it was proven that ZnO coatings hinder microbial biofilm formation of both Gram-positive and Gram-negative bacteria strains.