Advances in Biomedical Sciences and Engineering

Patients with severe spinal lateral deformity will consider for surgical intervention due to cardiopulmonary and cosmetic compromise. However, the current operation making use of conventional metals can only achieve 60-70% correction due to the spinal viscoelastic properties. Hence, spinal implants making use of the shape memory effect of nickel titanium shape memory alloy have been developed to overcome these problems. Nevertheless, the surgical outcome did not significantly differ with the conventional implants. The invention new spinal system is still needed in order to achieve better spinal deformity correction.

Nickel-titanium (NiTi) shape memory alloys are very potential for surgical implantation due to two unique properties: super-elasticity and shape memory effect. These advantages cannot be seen in current biomedical metallic materials such as medical grade titanium alloys and stainless steels. However, nickel ion release remains a major concern particularly for large implants placed on the spine or joints, as fretting is always expected at such implant junctions. Therefore, an advanced surface treatment using plasma immersion ion implantation (PIII) technology to tackle this issue

Strontium (Sr) and related compounds have become more attractive in the prevention and treatment of osteoporosis. Previously, we developed a novel bioactive bone cement, which mainly composed of strontium-containing hydroxyapatite (Sr-HA) filler and bisphenol A diglycidylether dimethacrylate (Bis-GMA) resin. This bone cement is superior to conventional polymethylmethacrylate (PMMA) bone cement in bioactivity, biocompatibility, and osseointegration. It also has shown sufficient mechanical strength properties for its use in percutaneous vertebroplasty (PVP) and total hip replacement (THR). In this chapter, we reviewed the in vitro, in vivo, and clinical evidence for the effectiveness of this bioactive bone cement.

Hydroxyapatite (HA) is the main mineral constituent of human bones. HA nanocrystals can be synthesized using a variety of wet solution methods including chemical precipitation, hydrothermal, sol-gel, micro- and nano-emulsion. HA nanocrystals synthesized from the chemical precipitation process generally exhibit plate-like morphology. They tend to self-organize into an ordered structure in the presence of biopolymers. The self-assembled HA-polymer nanocomposites simulate the hierarchical structure of human bone at a fundamental level. Such biomimetic nanocomposites favor osteoblast adhesion and proliferation, thereby stimulating new bone growth. Proper understanding of the biomineralization of self-assembled structures is needed for designing high performance polymer nanocomposites in bone tissue engineering.

Carbon nanotubes (CNTs) exhibit excellent electrical conductivity, mechanical strength, stiffness and toughness as well as good biocompatibility with human cells. Accordingly, CNTs are attractive reinforcing materials for polymer nanocomposites designed for orthopedic applications. The integration of CNTs into polymeric materials opens up new frontiers in biomaterials. In this chapter, the synthesis, purification and functionalization of carbon nanotubes, mechanical property and biocompatibility of CNT-polymer nanocomposites are described in details. Proper understanding of the process-structure-property relationship of CNT-polymer nanocomposites is necessary to achieve desired mechanical property and biocompatibility.

Ionizing radiation is encountered in our natural environment and is also generated and used by mankind, e.g., for medical uses. A better understanding of the biological effects of ionizing radiation will lead to better use of and better protection from radiation. In this chapter, the response of cells to radiation will be described and discussed. Some basic concepts of ionizing radiation will be briefly given in the beginning. The significant consequences of various types of radiation-induced DNA damages show that DNA is the principle target for biological effects of radiation. The misrepaired or unrepaired DNA damages, in particular DNA double strand breaks, will induce chromosomal aberrations and gene mutations. On the other hand, radiation-induced DNA double strand breaks play an important role in the induction of apoptosis and cell cycle arrest. Radiationinduced bystander response, adaptive response and genomic instability are currently “hot-pots” in the radiobiological research. These three phenomena indicate the complexity of cellular responses to radiation, and will be introduced and discussed in this chapter.

A brief review on the progress on in vivo studies of α-particle radiation effects using zebrafish embryos was given in this chapter. The zebrafish, Danio rerio, a small vertebrate from Southeast Asia, has become a preferred model for studying human disease. The main challenges of these α-particle radiobiological experiments included quantification of alpha-particle dose. In particular, specially etched polyallyldiglycol carbonate (PADC) films, which are a kind of solid-state nuclear track detector (SSNTD), were chosen as support substrates for zebrafish embryos. The fabrication procedures were outlined. Methods for quantification of alpha-particle dose were described. Preliminary in vivo studies on the radiation effects of alpha particles in zebrafish embryos were briefly reviewed. These included results on low-dose radiation effects of α particles as well as results on alpha-particle-induced bystander effects between zebrafish embryos in vivo.

The potential widespread use of nanomaterials has led to a strong concern about the impact of these new nanomaterials on human health and the environment. The exposure pathways, in vitro cytotoxicity, pulmonary and respiratory toxicity and biodistribution of carbon nanotubes (CNTs) will be reviewed in the first part of this chapter. Once CNTs are produced cheaply in large amounts, they will be used more widely around the world, and profoundly influence the aquatic environment and aquatic species as a consequence. The second part of this chapter will discuss zebrafish (Danio rerio) as a powerful and versatile in vivo model system in the toxicology research of nanomaterials. The widespread habitat of this fish species makes them an ideal model to study the ecological consequence of nanomaterials being discharged in large quantities in the aquatic system. The zebrafish is also a widely used model organism of human development and diseases, making them an excellent model to study biocompatibility of nanomaterials being introduced inside the vertebrate bodies. The impact of CNTs on the aquatic environment was investigated by examining the properties of pristine CNTs under several environmental conditions with developing zebrafish embryos. The in vivo biodistribution and long term effects were further studied using purified and chemically modified CNTs by introducing them into the 1-cell stage embryonic cell and the circulation system of the transparent zebrafish embryos. The study suggests that extensive purification and functionalization processes can help improve the biocompatibility of CNTs.