Structure and antibacterial properties of Ag-doped micropattern surfaces produced by photolithography method.

Photolithography methods offer ample opportunities for creating biological surface patterns over large areas. Herein, samples with patterned surface having the same Ag total coverage area and content, but different surface topography made of periodically spaced Ag/Si pillars with a diameter of 10 and 50 µm and a height of 3, 1, and 0.2 µm were produced by photolithography technique and studied to uncover the dependences of bactericide ion release on surface topography and antibacterial effect on Ag+ ion concentration. Reactive ion etching of Si wafers in areas unprotected by Ag capping layer was accompanied by a number of competing processes: (i) formation of Ag particles on the tops of pillars due to temperature-activated diffusion and coalescence, (ii) sputtering of Ag from the pillar to surface and redeposition into the etching cavities, resulting in the formation of small Ag nanoparticles located in areas between pillars, (iii) precipitation of AgSix phase as a result of chemical interaction of sputtered Si ions with Ag ions and atoms in surrounding plasma. Samples with the largest pillar heights which had also Ag particles formed between pillars demonstrated the fastest Ag+ ion release and, correspondingly, a noticeable antibacterial effect toward antibiotic-resistant hospital Escherichia coli K-261 strains already after 3 h. All samples showed 100% antibacterial effect after 24 h. Thus our results open up new possibilities for the production of scalable micropattern surfaces with controlled bactericide ion release and pronounced antibacterial characteristics for future applications in the orthopedic field.

Approaches for Controlled Ag+ Ion Release: Influence of Surface Topography, Roughness, and Bactericide Content.

Silver is the most famous bactericidal element known from ancient times. Its antibacterial and antifungal effects are typically associated with the Ag ionization and concentration of Ag+ ions in a bacterial culture. Herein we thoroughly studied the influence of surface topography and roughness on the rate of Ag+ ion release. We considered two types of biocompatible and bioactive TiCaPCON-Ag films with 1 and 2 at. % of Ag and nine types of Ti surfaces with an average roughness varying in the range from 5.4 × 10-2 to 12.6 µm and different topographic features obtained through polishing, sandblasting, laser treatment, and pulsed electrospark deposition. It is demonstrated that the Ag+ ion release rates do not depend on the Ag content in the films as the main parameter, and it is other factors, such as the state of Ag agglomeration, surface topography and roughness, as well as kinetics of surface oxidation, that play a critical role. The obtained results clearly show a synergistic effect of the Ag content in the film and surface topography and roughness on Ag+ ion release. By changing the surface topographical features at a constant content of bactericidal element, we showed that the Ag+ ion release can be either accelerated by 2.5 times or almost completely suppressed. Despite low Ag+ ion concentration in physiological solution (<40 ppb), samples with specially fabricated surface reliefs (flakes or holes) showed a pronounced antibacterial effect already after 3 h of immersion in E. coli bacterial culture. Thus, our results open up new possibilities for the production of cost-effective, scalable, and biologically safe implants with pronounced antibacterial characteristics for future applications in the orthopedic field.

Fabrication method, structure, mechanical, and biological properties of decellularized extracellular matrix for replacement of wide bone tissue defects.

The present paper was focused on the development of a new method of decellularized extracellular matrix (DECM) fabrication via a chemical treatment of a native bone tissue. Particular attention was paid to the influence of chemical treatment on the mechanical properties of native bones, sterility, and biological performance in vivo using the syngeneic heterotopic and orthotopic implantation models. The obtained data indicated that after a chemical decellularization treatment in 4% aqueous sodium chlorite, no noticeable signs of the erosion of compact cortical bone surface or destruction of trabeculae of spongy bone in spinal channel were observed. The histological studies showed that the chemical treatment resulted in the decellularization of both bone and cartilage tissues. The DECM samples demonstrated no signs of chemical and biological degradation in vivo. Thorough structural characterization revealed that after decellularization, the mineral frame retained its integrity with the organic phase; however clotting and destruction of organic molecules and fibers were observed. FTIR studies revealed several structural changes associated with the destruction of organic molecules, although all organic components typical of intact bone were preserved. The decellularization-induced structural changes in the collagen constituent resulted changed the deformation under compression mechanism: from the major fracture by crack propagation throughout the sample to the predominantly brittle fracture. Although the mechanical properties of radius bones subjected to decellularization were observed to degrade, the mechanical properties of ulna bones in compression and humerus bones in bending remained unchanged. The compressive strength of both the intact and decellularized ulna bones was 125-130 MPa and the flexural strength of humerus bones was 156 and 145 MPa for the intact and decellularized samples, respectively. These results open new avenues for the use of DECM samples as the replacement of wide bone tissue defects.