Biofilm Interactions of Candida albicans and Mitis Group Streptococci in a Titanium-Mucosal Interface Model.

Streptococci from the mitis group (represented mainly by Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii) form robust biofilms with Candida albicans in different experimental models. These microorganisms have been found in polymicrobial biofilms forming on titanium biomaterial surfaces in humans with peri-implant disease. The purpose of this work was to study mutualistic interactions in biofilms forming on titanium and their effect on the adjacent mucosa, using a relevant infection model. Single and mixed biofilms of C. albicans and each Streptococcus species were grown on titanium disks. Bacterial and fungal biovolume and biomass were quantified in these biofilms. Organotypic mucosal constructs were exposed to preformed titanium surface biofilms to test their effect on secretion of proinflammatory cytokines and cell damage. C. albicans promoted bacterial biofilms of all mitis Streptococcus species on titanium surfaces. This relationship was mutualistic since all bacterial species upregulated the efg1 hypha-associated gene in C. albicans Mixed biofilms caused increased tissue damage but did not increase proinflammatory cytokine responses compared to biofilms comprising Candida alone. Interestingly, spent culture medium from tissues exposed to titanium biofilms suppressed Candida growth on titanium surfaces.IMPORTANCE Our findings provide new insights into the cross-kingdom interaction between C. albicans and Streptococcus species representative of the mitis group. These microorganisms colonize titanium-based dental implant materials, but little is known about their ability to cause inflammation and damage of the adjacent mucosal tissues. Using an in vitro biomaterial-mucosal interface infection model, we showed that mixed biofilms of each species with C. albicans enhance tissue damage. One possible mechanism for this effect is the increased fungal hypha-associated virulence gene expression we observed in mixed biofilms with these species. Interestingly, we also found that the interaction of multispecies biofilms with organotypic mucosal surfaces led to the release of growth-suppressing mediators of Candida, which may represent a homeostatic defense mechanism of the oral mucosa against fungal overgrowth. Thus, our findings provide novel insights into biofilms on biomaterials that may play an important role in the pathogenesis of mucosal infections around titanium implants.

Biomedical applications of nano-titania in theranostics and photodynamic therapy.

Titanium dioxide (TiO2) is one of the most abundantly used nanomaterials for human life. It is used in sunscreen, photovoltaic devices, biomedical applications and as a food additive and environmental scavenger. Nano-TiO2 in biomedical applications is well documented. It is used in endoprosthetic implants and early theranostics of neoplastic and non-neoplastic maladies as a photodynamic therapeutic agent and as vehicles in nano-drug delivery systems. Herein, we focus on the recent advancements and applications of nano-TiO2 in bio-nanotechnology, nanomedicine and photodynamic therapy (PDT).

Ambient particulate matter affects occludin distribution and increases alveolar transepithelial electrical conductance.

BACKGROUND AND OBJECTIVE: Inhaled particulate matter (PM) causes lung inflammation and epithelial dysfunction. However, the direct effect of PM on alveolar epithelial barrier integrity is not well understood. Our aim is to determine whether PM exposure affects the alveolar epithelial cells (AEC) transepithelial electrical conductance (Gt) and tight junction (TJ) proteins. METHODS: Human AEC (A549) and primary rat AEC were exposed to PM of <10 µm in size (PM(10) ) and diesel exhaust particles (DEP), using titanium dioxide (TiO(2) ) as a control for particle size effects. Gt and permeability to fluorescein isothiocyanate-dextran (FITC-Dextran) were measured to assess barrier integrity. TJ integrity was evaluated by analysing penetration of Lanthanum nitrate (La(3+) ) under transmission electron microscopy. Surface proteins were labelled with biotin and analysed by western blot. Immunofluorescence was performed to assess colocalization of TJ proteins including occludin and zonula occludens-1 (ZO-1). PM induced dissociation of occludin-ZO-1 was evaluated by co-immunoprecipitation. RESULTS: PM(10) and DEP increased Gt and disrupted TJ after 3 h of treatment. PM(10) and DEP induced occludin internalization from the plasma membrane into endosomal compartments and dissociation of occludin from ZO-1. Overexpression of antioxidant enzymes manganese superoxide dismutase (MnSOD) and catalase, prevented PM-induced Gt increase, occludin reduction from the plasma membrane and its dissociation from ZO-1. CONCLUSIONS: PM induces alveolar epithelial dysfunction in part via occludin reduction at the plasma membrane and ZO-1 dissociation in AEC. Furthermore, these effects are prevented by overexpression of two different antioxidant enzymes.

Physical characterization of different-roughness titanium surfaces, with and without hydroxyapatite coating, and their effect on human osteoblast-like cells.

The aim of this study was to characterize and compare various titanium (Ti) and hydroxyapatite (HA) coatings on Ti6Al4V, in view of their application on noncemented orthopedic implants. Two innovative vacuum plasma sprayed (VPS) coatings, the first of ultrahigh rough and dense Ti (PG60, Ra=74 microm) and the second of ultrahigh rough and dense Ti coated with HA (HPG60, Ra=52 microm), have been developed, and the response of osteoblast-like cells (MG-63) seeded on these new coatings was evaluated in comparison to: a low roughness and sandblasted (Ti/SA, Ra=4 microm) Ti6Al4V surface; Ti medium (TI01, Ra=18 microm), and high (TI60, Ra=40 microm) roughness VPS coatings; and the relative Ti plus HA duplex coatings (HT01, Ra=12 microm and HT60, Ra=36 microm respectively), also obtained by VPS. PG60 coating presented no open porosity, making it dense and potentially intrinsically stronger. Cell adhesion and proliferation on PG60 was similar to those of the smoothest one (Ti/SA) and adhesion on ultrahigh roughness was lower than the medium- and high-roughness coatings, whereas cell proliferation on PG60 was lower than TI60. The HA coating determined significant increases in cell proliferation at medium and high roughness levels when compared to the relative Ti coating, but not compared to the ultrahigh one; all HA-coated surfaces showed a decrease in alkaline phosphatase activity and collagen I production. Surface morphology and the HA coating strongly affected cell behavior. However, ultrahigh values of roughness are not correctly seen by cells, and the presence of HA has no improving effects.

Perovskites in the comb roof base of hornets: their possible function.

On the ceiling of the Oriental hornet comb cell, there are mineral granules of polycrystalline material known to belong to the group of perovskites. In a comb cell intended to house a worker hornet, the roof base usually carries one or several such perovskite granules containing titanium (Ti), whereas in the roof base of a cell housing a developing queen, there are usually several granules containing a high percentage of silicon (Si), aluminum (Al), calcium (Ca), and iron (Fe), but very little if any Ti. In worker comb cells, Ti usually appears as ilmenite (FeTiO3). Besides documenting the above-mentioned facts, this report discusses possible reasons for the appearance of ilmenite crystals in worker cells only and not in queen cells.

Enhanced bone apposition to a chemically modified SLA titanium surface.

Increased surface roughness of dental implants has demonstrated greater bone apposition; however, the effect of modifying surface chemistry remains unknown. In the present study, we evaluated bone apposition to a modified sandblasted/acid-etched (modSLA) titanium surface, as compared with a standard SLA surface, during early stages of bone regeneration. Experimental implants were placed in miniature pigs, creating 2 circular bone defects. Test and control implants had the same topography, but differed in surface chemistry. We created the test surface by submerging the implant in an isotonic NaCl solution following acid-etching to avoid contamination with molecules from the atmosphere. Test implants demonstrated a significantly greater mean percentage of bone-implant contact as compared with controls at 2 (49.30 vs. 29.42%; p = 0.017) and 4 wks (81.91 vs. 66.57%; p = 0.011) of healing. At 8 wks, similar results were observed. It is concluded that the modSLA surface promoted enhanced bone apposition during early stages of bone regeneration.

Mechanical performance of the new posterior spinal implant: effect of materials, connecting plate, and pedicle screw design.

STUDY DESIGN: A newly designed spinal implant was tested to evaluate multicycle stiffness and fatigue resistance. OBJECTIVES: To investigate the effect of different materials, connecting plate, and pedicle screw design on the mechanical performance of the spinal implant. SUMMARY OF THE BACKGROUND DATA: The addition of cross-linkages did not significantly increase implant compression/flexion stiffness, but accelerated fatigue failure at the rod junctions. Both Ti-6Al-4V spinal implants and the 316L stainless-steel counterparts have been used extensively for clinical cases; however, design factors establishing the proposed superiority of the Ti-6Al-4V implant for fatigue resistance have not, as yet, been extensively studied. METHODS: Twenty implants with connecting plates (two materials by two screw designs by five implants) and five implants without connecting plates were assembled to UHMWPE blocks and cyclically loaded from 60 N to 600 N at a frequency of 5 Hz. RESULTS: Failure sites for the tested prototypes were at the cephalic screw hubs or rod-plate junctions. All Ti-6Al-4V implants demonstrated reduced stiffness compared to the structurally identical 316L analogs. The use of connecting plates raised the stiffness of the 316L prototypes without cross-links. However, elimination of the connecting plate avoided stress concentration at the rod/plate junctions and increased fatigue life. The Ti-6Al-4V new system with the minimal notch effect at the screw hubs achieved greater fatigue resistance than its 316L counterpart. By contrast, enlargement of the inner-hub diameter resulted in greater gains for fatigue resistance than for stiffness, especially for Ti-6Al-4V variants. CONCLUSIONS: Although Ti-6Al-4V was superior to 316L for endurance-limit properties, structural design of the Ti-6Al-4V implant dramatically affects fatigue resistance. This may explain the differences between existing studies and the current report, comparing fatigue life for implants made from these two materials. Our results reveal that Ti-6Al-4V must be carefully treated because of sensitivity to notch, with special consideration given to screw-hub design.

The influence of design parameters on cortical strain distribution of a cementless titanium femoral stem.

The strain distribution imposed on a femur following a total joint replacement is an important factor, in proximal bone loss due to stress shielding, and long term clinical success. This study investigated how five different design parameters of a cementless titanium femoral prosthesis influenced cortical strains. Test loads were applied and strains were measured with and without an abductor force simulation, using six human cadaveric femora. The cementless design used demonstrated significant calcar loading proximally and a similar strain distribution to the intact femur distally. Implant gross geometry was the major factor in determining the cortical strain distributions under abductor simulation in both axial and torsional loading.

Biological roles of titanium.

Ti4+ in soil is a natural antibiotic mobilized by bacteria-generated H+. When added to the diet of young mice, Ti4+ enhanced their growth. These and observations of others indicate that Ti4+ has a variety of biological roles.

Surface-dimpled commercially pure titanium implant and bone ingrowth.

The purpose of this investigation was to examine the effect of the surface macrostructure of a dimpled commercially pure titanium (cp Ti) implant on bone ingrowth in vivo by means of histological examination and a push-out test. Cylindrical implants were inserted in one femur of each experimental rabbit and the animals were killed at 1.5, 3 and 13 months after implantation. The femur with the implant of each animal was then examined in a push-out test. The fracture surfaces of the bone-implant interface after the push-out test were examined under light and electron microscopy. It seems that the dimpled cp Ti surface results in the increased retention of the cp Ti implant in bone due to interlocking between vital bone and the dimples.

Biology of grit-blasted titanium alloy implants.

This study describes the biologic integration of grit-blasted titanium alloy (Ti-6A1-4V) implants that were press fit into the distal femoral canal of young adult rabbits and evaluated by histologic, histomorphometric, and biomechanical methods. Polished and aluminum oxide grit-blasted (4.2 +/- 0.7 microns surface roughness) solid implants were compared with titanium fibermetal implants. Nondecalcified cross sections were studied by histology, histomorphometry, and electron microscopy in the backscatter mode at 3, 6, and 12 weeks after implantation. Pullout strength was measured at 12 weeks. Data were analyzed by analysis of variance and post-hoc Student-Newman-Keuls and Scheffe's tests. The blasted implants had significantly more bone intimately in contact with the implant surface (31%) than the fibermetal (17%), or solid polished implants (15%). By 3 weeks, woven bone had formed directly on the surface of the blasted implants, whereas there was a discrete space between woven bone and the other implants. Active remodeling of bone was shown by fluorochrome uptake at the surface of the blasted implants at 12 weeks after implantation. The strength of fixation of blasted and fiber-metal implants was significantly greater than polished implants at 12 weeks after implantation. Direct attachment of newly formed bone onto the blasted implant surface was confirmed by backscatter electron microscopy. The results of this study indicate that grit-blasted titanium surfaces provide an excellent surface for bone implant integration.