Publications

Laser surface micropatterning of dental-grade zirconia (3Y-TZP) was explored with the objective of providing defined linear patterns capable of guiding bone-cell response.A nanosecond (ns-) laser was employed to fabricate microgrooves on the surface of 3Y-TZP discs, yielding three different groove periodicities (i.e., 30, 50 and 100 µm). The resulting topography and surface damage were characterized by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). X-Ray diffraction (XRD) and Raman spectroscopy techniques were employed to assess the hydrothermal degradation resistance of the modified topographies. Preliminary biological studies were conducted to evaluate adhesion (6 h) of human mesenchymal stem cells (hMSC) to the patterns in terms of cell number and morphology. Finally, Staphylococcus aureus adhesion (4 h) to the microgrooves was investigated.The surface analysis showed grooves of approximately 1.8 µm height that exhibited surface damage in the form of pile-up at the edge of the microgrooves, microcracks and cavities. Accelerated aging tests revealed a slight decrease of the hydrothermal degradation resistance after laser patterning, and the Raman mapping showed the presence of monoclinic phase heterogeneously distributed along the patterned surfaces. An increase of the hMSC area was identified on all the microgrooved surfaces, although only the 50 µm periodicity, which is closer to the cell size, significantly favored cell elongation and alignment along the grooves. A decrease in Staphylococcus aureus adhesion was observed on the investigated micropatterns.The study suggests that linear microgrooves of 50 µm periodicity may help in promoting hMSC adhesion and alignment, while reducing bacterial cell attachment.Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

JTD Keywords: abutment material, alumina toughened zirconia, antibacterial, bacterial adhesion, biofilm growth, cell adhesion, dental implants, hydrothermal degradation, implant surfaces, in-vitro, laser patterning, osseointegration, osteogenic differentiation, part 1, surface topography, y-tzp ceramics, Antibacterial, Antibacterials, Bacteria, Bone, Cell adhesion, Cell culture, Cells adhesion, Ceramics, Chemistry, Degradation resistance, Dental implants, Dental material, Dental materials, Dental prostheses, Human, Human mesenchymal stem cells, Humans, Hydrothermal degradation, Laser patterning, Laser surface, Lasers, Low-temperature degradation, Materials testing, Microscopy, electron, scanning, Nanosecond lasers, Osseointegration, Piles, Scanning electron microscopy, Staphylococcus aureus, Stem cells, Surface analysis, Surface damages, Surface properties, Surface property, Surface topography, Topography, Yttrium, Zirconia, Zirconium

Unlike the attachment of soft epithelial skin tissue to penetrating solid natural structures like fingernails and teeth, sealing around percutaneous/permucosal devices such as dental implants is hindered by inflammation and epidermal down growth. Here, we employed a dual keratinocyte-adhesive peptide and anti-inflammatory biomolecule coating on titanium to promote oral epithelial tissue attachment. For minimizing inflammation-triggered epidermal down growth, we coated pristine and oxygen plasma pre-treated polished titanium (pTi) with conjugated linoleic acid (CLA). Further, in order to aid in soft tissue attachment via the formation of hemidesmosomes, adhesive structures by oral keratinocytes, we coated the anionic linoleic acid (LA) adsorbed titanium with cationic cell adhesive peptides (CAP), LamLG3, a peptide derived from Laminin 332, the major extracellular matrix component of the basement membrane in skin tissue and Net1, derived from Netrin-1, a neural chemoattractant capable of epithelial cell attachment via alpha 6 beta 4 integrins. The dual CLA-CAP coatings on pTi were characterized by X-ray photoelectron spectroscopy and dynamic water contact angle measurements. The proliferation of human oral keratinocytes (TERT-2/OKF6) was accelerated on the peptide coated titanium while also promoting the expression of Col XVII and beta-4 integrin, two markers for hemidesmosomes. Simultaneously, CLA coating suppressed the production of inducible nitric oxide synthase (anti-iNOS); a pro-inflammatory M1 marker expressed in lipopolysaccharide (LPS) stimulated murine macrophages (RAW 264.7) and elevated expression of anti-CD206, associated to an anti-inflammatory M2 macrophage phenotype. Taken together, the dual keratinocyte-adhesive peptide and anti-inflammatory biomolecule coating on titanium can help reduce inflammation and promote permucosal/peri-implant soft tissue sealing.

JTD Keywords: Adhesives, Animal, Animals, Anti-inflammatories, Anti-inflammatory agents, Antiinflammatory agent, Biomolecules, Bone, Cell adhesion, Cell-adhesives, Coatings, Conjugated linoleic acid, Conjugated linoleic-acid, Contact angle, Hemidesmosome, Hemidesmosomes, Human, Humans, Hydroxyapatite, Inflammation, Integrins, Keratinocyte, Keratinocytes, Linoleic acid, Macrophages, Mice, Mouse, Nitric oxide, Oral implants, Pathology, Peptides, Skin tissue, Soft tissue, Supplementation, Surface properties, Surface property, Tissue, Titania, Titanium, X ray photoelectron spectroscopy

A technique for producing micrometer-scale structures over large, nonplanar chitosan surfaces is described. The technique makes use of the rheological characteristics (deformability) of the chitosan to create freestanding, three-dimensional scaffolds with controlled shapes, incorporating defined microtopography. The results of an investigation into the technical limits of molding different combinations of shapes and microtopographies are presented, highlighting the versatility of the technique when used irrespectively with inorganic or delicate organic moulds. The final, replicated scaffolds presented here are patterned with arrays of one-micrometer-tall microstructures over large areas. Structural integrity is characterized by the measurement of structural degradation. Human umbilical vein endothelial cells cultured on a tubular scaffold show that early cell growth is conditioned by the microtopography and indicate possible uses for the structures in biomedical applications. For those applications requiring improved chemical and mechanical resistance, the structures can be replicated in poly(dimethyl siloxane).

JTD Keywords: Biocompatible Materials/ chemistry, Cell Adhesion, Cell Culture Techniques/ methods, Cell Proliferation, Cells, Cultured, Chitosan/ chemistry, Crystallization/methods, Endothelial Cells/ cytology/ physiology, Humans, Materials Testing, Nanostructures/ chemistry/ ultrastructure, Nanotechnology/methods, Particle Size, Surface Properties, Tissue Engineering/methods

We developed new hybrid nanomaterials, urease/LDH (layered double hydroxides), for the urea detection. The LDH that were prepared by co-precipitation in constant pH and in ambient temperature are hydrotalcites (Mg2Al, Mg3Al) and zaccagnaite (Zn2Al and Zn3Al). The immobilization of urease in these various layered hybrid materials is realized by auto-assembly. The structures of hosted matrices were studied by X-ray diffraction, Absorbance Infrared spectroscopy in ATR mode and Atomic Force Microscopy (AFM). These techniques allowed the characterisation of the urease immobilization and its interactions with LDH chemical groups. The urease was adsorbed and its morphology was conserved in its new environment. Furthermore, the study of catalytic parameters of Urease/LDH biomembranes and of the kinetics reaction of urea hydrolysis shows a good conformation of the enzyme in hydrotalcite matrices and that the affinity is similar to free urease.

JTD Keywords: Ldh hybrid nanomaterials, Surface properties, Urea biosensors, Urease thin films

Thin films of silicon nitride (Si3N4) can be used in several kinds of micro-sized biosensors as a material to monitor fine environmental changes related to the process of bone formation in vitro. We found however that Si3N4 does not provide optimal conditions for osseointegration as osteoblast-like MG-63 cells tend to detach from the surface when cultured over confluence. Therefore Si3N4 was modified with self-assembled monolayers bearing functional end groups of primary amine (NH2) and carboxyl (COOH) respectively. Both these modifications enhanced the interaction with confluent cell layers and thus improve osseointegration over Si3N4. Furthermore it was observed that the NH2 functionality increased the adsorption of fibronectin (FN), promoted cell proliferation, but delayed the differentiation. We also studied the fate of pre-adsorbed and secreted FN from cells to learn more about the impact of above functionalities for the development of provisional extracellular matrix on materials interface. Taken together our data supports that Si3N4 has low tissue integration but good cellular biocompatibility and thus is appropriate in cellular biosensor applications such as the ion-sensitive field effect transistor (ISFET). COOH and NH2 chemistries generally improve the interfacial tissue interaction with the sensor and they are therefore suitable substrates for monitoring cellular growth or matrix deposition using electrical impedance spectroscopy.

JTD Keywords: Adsorption, Amines/chemistry, Biocompatible Materials/ chemistry, Biosensing Techniques, Cell Differentiation, Cell Line, Cell Proliferation, Electric Impedance, Extracellular Matrix/metabolism, Fibronectins/chemistry, Humans, Materials Testing, Osteoblasts/ cytology, Silicon Compounds/ chemistry, Surface Properties