Osseointegration and Histopathological Evaluation of Titanium-Titanium Diboride Composite Compared to Pure Titanium Implant Materials Prepared by Powder Metallurgy (In Vivo Study)

The efficacy and osseointegration rate of an implant depend on its biocompatibility. Modern implantology seeks fast and reliable osseointegration, which is essential for clinical success. The objective of this research was to assess the osseointegration and biocompatibility of a titanium-titanium diboride composite (Ti-TiB2) in rabbits in contrast to those of pure titanium (Ti). A total of 64 cylindrical implant specimens were fabricated, consisting of two sets: pure Ti (32 implants) and Ti-TiB2 composite (32 implants). In this study, two implants were implanted per tibia (left and right tibias) in 16 white male New Zealand rabbits, for a total of four implants per rabbit (4 × 16 = 64 implants). A pushout test was used to assess implant specimen-bone bonding after 2 and 6 weeks of healing. The experiment utilized five rabbits per healing phase, which means that 20 implants per time point were used for the pushout tests. (10 for pure Ti and 10 for the composite). Histology was used to examine the tissue response to biocompatibility, and histomorphometry was used to measure new bone growth at the two time points. With three rabbits per time point, 12 implants were employed for the histological analyses. After implantation, the pushout shear strength results revealed that the mean shear strength of the Ti-TiB2 implant specimens (5.4 ± 0.029 MPa for 2 weeks, 7.9 ± 0.029 MPa for 6 weeks) was statistically greater (p < 0.0001) than that of the pure Ti implant specimens (5.1 ± 0.015 MPa for 2 weeks, 6.6 ± 0.047 MPa for 6 weeks). After 2 weeks, woven bone tissues were observed around the pure titanium implants, and active osteoid tissue around the composite implants exhibited significant differences in new bone formation areas (NBFAs) (0.54 ± 0.004 mm2 for Ti and 0.65 ± 0.003 mm2 for the composite). After 6 weeks, there was new bone formation with osteocytes around the pure titanium implants (NBFA of 2.44 mm2) and osteoid maturation with the observation of reversal lines around the composite implants (NBFA of 2.89 mm2). The developed Ti-TiB2 material was biocompatible and demonstrated superior bone growth compared to that of the pure Ti materials after 2 and 6 weeks.

Molecular Genetics and Cytotoxic Responses to Titanium Diboride and Zinc Borate Nanoparticles on Cultured Human Primary Alveolar Epithelial Cells

Titanium diboride (TiB₂) and zinc borate (Zn₃BO₆) have been utilized in wide spectrum industrial areas because of their favorable properties such as a high melting point, good wear resistance, high hardness and thermal conductivity. On the other hand, the biomedical potentials of TiB₂ and Zn₃BO₆ are still unknown because there is no comprehensive analysis that uncovers their biocompatibility features. Thus, the toxicogenomic properties of TiB₂ and Zn₃BO₆ nanoparticles (NPs) were investigated on human primary alveolar epithelial cell cultures (HPAEpiC) by using different cell viability assays and microarray analyses. Protein-Protein Interaction Networks Functional Enrichment Analysis (STRING) was used to associate differentially expressed gene probes. According to the results, up to 10 mg/L concentration of TiB₂ and Zn₃BO₆ NPs application did not stimulate a cytotoxic effect on the HPAEpiC cell cultures. Microarray analysis revealed that TiB₂ NPs exposure enhances cellular adhesion molecules, proteases and carrier protein expression. Furthermore, Zn₃BO₆ NPs caused differential gene expressions in the cell cycle, cell division and extracellular matrix regulators. Finally, STRING analyses put forth that inflammation, cell regeneration and tissue repair-related gene interactions were affected by TiB₂ NPs application. Zn₃BO₆ NPs exposure significantly altered inflammation, lipid metabolism and infection response activator-related gene interactions. These investigations illustrated that TiB₂ and Zn₃BO₆ NPs exposure may affect different aspects of cellular machineries such as immunogenic responses, tissue regeneration and cell survival. Thus, these types of cellular mechanisms should be taken into account before the use of the related NPs in further biomedical applications.

TiB Nanowhisker Reinforced Titanium Matrix Composite with Improved Hardness for Biomedical Applications

Titanium and its alloys have been employed in the biomedical industry as implants and show promise for more broad applications because of their excellent mechanical properties and low density. However, high cost, poor wear properties, low hardness and associated side effects caused by leaching of alloy elements in some titanium alloys has been the bottleneck to their wide application. TiB reinforcement has shown promise as both a surface coating for Ti implants and also as a composite reinforcement phase. In this study, a low-cost TiB-reinforced alpha titanium matrix composite (TMC) is developed. The composite microstructure includes ultrahigh aspect ratio TiB nanowhiskers with a length up to 23 μm and aspect ratio of 400 and a low average Ti grain size. TiB nanowhiskers are formed in situ by the reaction between Ti and BN nanopowder. The TMC exhibited hardness of above 10.4 GPa, elastic modulus above 165 GPa and hardness to Young’s modulus ratio of 0.062 representing 304%, 170% and 180% increases in hardness, modulus and hardness to modulus ratio, respectively, when compared to commercially pure titanium. The TiB nanowhisker-reinforced TMC has good biocompatibility and shows excellent mechanical properties for biomedical implant applications.

Demonstration of the bactericidal effects of the boron neutron capture reaction

This pilot study represents a paradigm shift, using BNCT for the treatment of bacterial overgrowth on surgically implanted medical devices. In this study, titanium diboride disks were inoculated with S. aureus and irradiated in a thermal neutron beam. After a delivery of 2.6 × 10¹² n/cm² the surviving fraction of S. aureus on an irradiated disk was 3.1 × 10^-5 when compared with non-irradiated controls. This pilot study demonstrates proof of principle of boron neutron capture therapy for infection control (BNCIC).

A framework for health-related nanomaterial grouping

BACKGROUND

Nanotechnology has been in the limelight since its emergence and its products affect everyday lives. Nanomaterials are characterized by features such as size and shape, thus rendering their possible number essentially unlimited, which in turn makes them difficult to study and categorize regarding possible dangers. This work suggests that grouping could allow studying them with limited testing efforts without endangering safety.

METHODS

Initially, the materials are identified and grouped according to their applications in health/medicine, as well as on their environmentally-friendly potential. The materials are then categorized using various toxicity classification methods to identify those with highest risks and group them with others that demonstrate similar behavior.

RESULTS

The materials studied show promising uses in diagnostics, drug delivery, biosensors, water purification, oil spill cleaning, emission control and other fields. The toxicity risk assessment shows that the majority pose little to moderate risk, however there are certain materials that can be extremely hazardous or even cause death under specific circumstances. A risk mitigation plan was also developed.

CONCLUSIONS

Nanomaterials applications, including drug delivery, cancer treatment, waste treatment, solar energy generation etc. can be very beneficiary, but at the same time, these materials can be extremely harmful or even cause death, thus making the need to prioritize research on high risk materials crucial. A clear regulatory framework that addresses both benefits and risks and communicates that information effectively should play an important part in European and worldwide efforts.

GENERAL SIGNIFICANCE

The risk analysis validated the impression that there is limited research on nanomaterial toxicity risks, which calls for a more organized approach. The framework outlined in this work can be utilized by researchers as well as government bodies, in order to form regulatory policies and adopt a universally accepted labeling system. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.