Addressing the optimal silver content in bioactive glass systems in terms of BSA adsorption

Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Surface Modification of Bioactive Glass Promotes Cell Attachment and Spreading

Phosphate glasses have several advantages over traditional silicate-based bioglasses but are inferior in the crucial step of cell attachment to their surface. Here, as a proof of concept, we analyze fibroblast attachment to the phosphate glass surface subjected to basic treatment and silanization. Silicate (S53P4)- and phosphate (Sr50)-based bioactive glasses were either untreated or surface-treated with basic buffer and functionalized with silane. The surface-treated samples were studied as such and after fibronectin was adsorbed on to their surface. With both glass types, surface treatment enhanced fibroblast adhesion and spreading in comparison to the untreated glass. The surface-treated Sr50 glass allowed for cell adhesion, proliferation, and spreading to a similar extent as seen with S53P4 and borosilicate control glasses. Here, we show that surface treatment of bioactive glass can be used to attract cell adhesion factors found in the serum and promote cell-material adhesion, both important for efficient tissue integration.

Role of phase separation on the biological performance of 45S5 Bioglass®

We analyzed the biological performance of spinodally and droplet-type phase-separated 45S5 Bioglass^® generated by quenching the melt from different equilibrium temperatures. MC3T3-E1 pre-osteoblast cells attached more efficiently to 45S5 Bioglass® with spinodal than to the one with droplet morphology, providing the first demonstration of the role of micro-/nano-scale on the bioactivity of Bioglass®. Upon exposure to biological solutions, phosphate buffered saline (PBS) and cell culture medium (α-MEM), a layer of hydroxyapatite (HA) formed on both glass morphologies. Although both Bioglass® varieties were incubated under identical conditions, and physico-chemical characteristics of the HA layers were similar, the adsorption magnitude of a model protein, bovine serum albumin (BSA, an abundant blood serum component) and its β-sheet/β-turn ratio and α-helix content were significantly higher on spinodal than droplet type Bioglass®. These results indicate that: (i) a protein layer quickly adsorbs on the surface of 45S5 Bioglass® varieties (with or without HA layer), (ii) the amount and the conformation of adsorbed proteins are guided by the glass micro-/nano-structure, and (iii) cell attachment and proliferation are influenced by the concentration and the conformation of attached proteins with a significantly better cell adhesion to spinodal type 45S5 Bioglass® substrate. Taken together, our results indicate that the biological performance of 45S5 Bioglass® can be improved further with a relatively simple, inexpensive fabrication procedure that provides a superior glass micro-/nano-structure. A simple modification to the fabrication procedure of classic 45S5 Bioglass® generates spinodal (A(a)) and droplet (A(b)) varieties and has a significant impact on protein adsorption (B) and cell adhesion (C).

Surface Plasmon Resonance or Biocompatibility-Key Properties for Determining the Applicability of Noble Metal Nanoparticles

Metal and in particular noble metal nanoparticles represent a very special class of materials which can be applied as prepared or as composite materials. In most of the cases, two main properties are exploited in a vast number of publications: biocompatibility and surface plasmon resonance (SPR). For instance, these two important properties are exploitable in plasmonic diagnostics, bioactive glasses/glass ceramics and catalysis. The most frequently applied noble metal nanoparticle that is universally applicable in all the previously mentioned research areas is gold, although in the case of bioactive glasses/glass ceramics, silver and copper nanoparticles are more frequently applied. The composite partners/supports/matrix/scaffolds for these nanoparticles can vary depending on the chosen application (biopolymers, semiconductor-based composites: TiO₂, WO₃, Bi₂WO₆, biomaterials: SiO₂ or P₂O₅-based glasses and glass ceramics, polymers: polyvinyl alcohol (PVA), Gelatin, polyethylene glycol (PEG), polylactic acid (PLA), etc.). The scientific works on these materials' applicability and the development of new approaches will be targeted in the present review, focusing in several cases on the functioning mechanism and on the role of the noble metal.

Enhanced Cellular Internalization: A Bactericidal Mechanism More Relative to Biogenic Nanoparticles than Chemical Counterparts

Biogenic synthesis of silver nanoparticles for enhanced antimicrobial activity has gained a lot of momentum making it an urgent need to search for a suitable biocandidate which could be utilized for efficient capping and shaping of silver nanoparticles with enhanced bactericidal activity utilizing its secondary metabolites. Current work illustrates the enhancement of antimicrobial efficacy of silver nanoparticles by reducing and modifying their surface with antimicrobial metabolites of cell free filtrate of Trichoderma viride (MTCC 5661) in comparison to citrate stabilized silver nanoparticles. Nanoparticles were characterized by visual observations, UV-visible spectroscopy, zetasizer, and transmission electron microscopy (TEM). Synthesized particles were monodispersed, spherical in shape and 10-20 nm in size. Presence of metabolites on surface of biosynthesized silver nanoparticles was observed by gas chromatography-mass spectroscopy (GC-MS), energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity of both silver nanoparticles was tested against Shigella sonnei, Pseudomonas aeruginosa (Gram-negative) and Staphylococcus aureus (Gram-positive) by growth inhibition curve analysis and colony formation unit assay. Further, it was noted that internalization of biosynthesized nanoparticles inside the bacterial cell was much higher as compared to citrate stabilized particles which in turn lead to higher production of reactive oxygen species. Increase in oxidative stress caused severe damage to bacterial membrane enhancing further uptake of particles and revoking other pathways for bacterial disintegration resulting in complete and rapid death of pathogens as evidenced by fluorescein diacetate/propidium iodide dual staining and TEM. Thus, study reveals that biologically synthesized silver nanoarchitecture coated with antimicrobial metabolites of T. viride was more potent than their chemical counterpart in killing of pathogenic bacteria.