RETRACTED: Bioactivity, antibacterial activity and functionality of zirconia doped zinc phosphate bioglasses for application in dentistry

Investigation on the physical properties and biocompatibility of zirconia-alumina-silicate@diopside composite materials and its in vivo toxicity study in embryonic zebrafish

Bioceramic materials have a wide range of applications in the biomedical field, such as in the repair of bone defects and dental surgery. Silicate-based bioceramics have attracted biomedical researchers' interest due to their bioactivity and biodegradability. In this study, extended the scope of ZAS utilization in bone tissue engineering by introducing calcium-magnesium-silicate (diopside, CMS) as an interface material aim to develop a machinable bioceramic composite (ZASCMS) by the sol-gel method. The physicochemical characterization, in vitro biological properties and in vivo zebrafish cytotoxicity study of ZAS-based composites as a function of CMS contents, 0, 25, 50, 75 and 100 wt%, were performed. Results showed that the as-prepared ZASCMS possessed porous architecture with well-interconnected pore structure. Results also revealed that the mechanical properties of ZASCMS composite materials were gradually improved with increasing CMS contents. The ZASCMS composites with more than 50 wt% CMS had the highest compressive strength and modulus of 6.78 ± 0.62 MPa and 340.10 ± 16.81 MPa, respectively. Regarding in vitro bioactivities, the composite scaffolds were found to stimulate osteoblast-like UMR-106 cell adhesion, growth, and proliferation. The antibacterial activity of the ZASCMS composite scaffolds was tested against Staphylococcus epidermidis (S. epidermidis) and Escherichia coli (E. coli) also exhibited an antibacterial property. Furthermore, the in vivo studies using embryonic zebrafish were exposed to as-prepared particles (0-500 μg mL-1) and showed that the synthesized ZAS, CMS and ZASCMS composite particles were non-toxic based on the evaluation of survivability, hatching rate and embryonic morphology. In conclusions, our results indicated that the synthesized composite exhibited their biological properties and antibacterial activity, which could well be a promising material with high potential to be applied in orthopaedic and dental tissue engineering.

Bioactive glasses incorporating less-common ions to improve biological and physical properties

Bioactive glasses (BGs) have been a focus of research for over five decades for several biomedical applications. Although their use in bone substitution and bone tissue regeneration has gained important attention, recent developments have also seen the expansion of BG applications to the field of soft tissue engineering. Hard and soft tissue repair therapies can benefit from the biological activity of metallic ions released from BGs. These metallic ions are incorporated in the BG network not only for their biological therapeutic effects but also in many cases for influencing the structure and processability of the glass and to impart extra functional properties. The "classical" elements in silicate BG compositions are silicon (Si), phosphorous (P), calcium (Ca), sodium (Na), and potassium (K). In addition, other well-recognized biologically active ions have been incorporated in BGs to provide osteogenic, angiogenic, anti-inflammatory, and antibacterial effects such as zinc (Zn), magnesium (Mg), silver (Ag), strontium (Sr), gallium (Ga), fluorine (F), iron (Fe), cobalt (Co), boron (B), lithium (Li), titanium (Ti), and copper (Cu). More recently, rare earth and other elements considered less common or, some of them, even "exotic" for biomedical applications, have found room as doping elements in BGs to enhance their biological and physical properties. For example, barium (Ba), bismuth (Bi), chlorine (Cl), chromium (Cr), dysprosium (Dy), europium (Eu), gadolinium (Gd), ytterbium (Yb), thulium (Tm), germanium (Ge), gold (Au), holmium (Ho), iodine (I), lanthanum (La), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), nitrogen (N), palladium (Pd), rubidium (Rb), samarium (Sm), selenium (Se), tantalum (Ta), tellurium (Te), terbium (Tb), erbium (Er), tin (Sn), tungsten (W), vanadium (V), yttrium (Y) as well as zirconium (Zr) have been included in BGs. These ions have been found to be particularly interesting for enhancing the biological performance of doped BGs in novel compositions for tissue repair (both hard and soft tissue) and for providing, in some cases, extra functionalities to the BG, for example fluorescence, luminescence, radiation shielding, anti-inflammatory, and antibacterial properties. This review summarizes the influence of incorporating such less-common elements in BGs with focus on tissue engineering applications, usually exploiting the bioactivity of the BG in combination with other functional properties imparted by the presence of the added elements.

Evaluation of Antifungal Activity by Mixed Oxide Metallic Nanocomposite against Candida spp

High doses of antimicrobial agents are a huge threat due to the increasing number of pathogenic organisms that are becoming resistant to antimicrobial agents. This resistance has led to a search for alternatives. Therefore, this study presents the synthesis and characterization of ZrO2-Ag2O nanoparticles (NPs) by sol-gel. The NPs were analyzed by dynamic light scattering (DLS), UV-visible (UV-vis), Raman and scanning electron microscopy (SEM). The NPs were later evaluated for their antifungal effects against Candidaalbicans, Candida dubliniensis, Candida glabrata, and Candida tropicalis, using disc diffusion and microdilution methods, followed by the viability study. The DLS showed sizes for ZrO2 76 nm, Ag2O 50 nm, and ZrO2-Ag2O samples between 14 and 42 nm. UV-vis shows an absorption peak at 300 nm for ZrO2 and a broadband for Ag2O NPs. Raman spectra were consistent with factor group analysis predictions. SEM showed spherically shaped NPs. The antifungal activity result suggested that ZrO2-Ag2O NPs were effective against Candida spp. From the viability study, there was no significance difference in viability as a function of time and concentration on human mononuclear cells. This promising result can contribute toward the development of alternative therapies to treat fungal diseases in humans.

Tangerine mediated synthesis of zirconia as potential protective dental coatings

Demand of bioactive materials that may create a bacteria-free environment while healing and regenerating the defect area is increasing day by day. Zirconia is a very interesting material because of its biocompatibility and high fracture toughness. In this research work, zirconia nanoparticles (NPs) have been synthesized using sol-gel method. Molarity of sols is varied in the range of 25 to 125 mM. The effect of acidic and basic nature of sols is studied by maintaining acidic (2) and basic (9) pH. As-synthesized NPs are made soluble in deionized (DI) water using tangerine drops. Dissolved NPs are spin coated onto glass substrate prior to characterization. Pure tetragonal phase, observed under all conditions using basic medium (pH 9), is accompanied by smaller crystallite size and unit cell volume. Presence of stabilized zirconia phase leads to higher value of density and higher mechanical strength. Nanodendrites with distinct features are observed for the sample prepared with high molarity using basic medium. Whereas, soft agglomerated nanodendrites are observed using acidic medium. Optical properties show transmission of 60-80% in the visible and infrared regions for acidic based samples and ~84% for basic samples. Direct energy band gap is varied from 4.96 eV to 5.1 eV in acidic (pH 2) and 4.91 eV to 4.97 eV in basic (pH 9) media. FTIR spectra show the formation of fundamental tetragonal band at 490 cm^-1 for basic samples. Antibacterial response of zirconia is tested against E. coli, Streptococcus and Bacillus bacteria. Human teeth, bare and zirconia coated, are tested for their possible weight loss after dipping in various beverages. Zirconia coated tooth shows negligible degradation in hardness and weight after 24 hr dipping period. Thus, coatings prepared using water soluble zirconia (WSZ) nanoparticles, without the use of toxic solvents/reagents, are promising material to be used as protective coatings in biomedical applications.