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Many kinds of materials are currently used as artificial bone substitutes. Hydroxyapatite (HA), the same as the main inorganic component of bone, is one of commonly used bio-ceramics and has excellent bioactivity and biocompatibility with hard tissues. However, it has problems as the bone filler or bone tissue-engineering scaffold due to low fracture toughness and low degradation rate. Recently, biodegradable materials for bone tissue have been developed to respond the requirement. Collagen, the same as the main organic component of bone, is biocompatible, biodegradable and promotes cell adhesion. A composites associated with HA is expected to have early osteoconduction and bone replacement ability. The present study was to fabricate bone-like composites consist of HA and collagen. Besides the ossiferous ability of the material in vivo is evaluated by using rabbits. Bone-like composites were successfully fabricated in this study, associating the collagen with HA. And the composites presented good osteoconductive and bone replacement potential.

We have here an insight into the features of molecular structures of bio-polymers with α-helix structure using infrared spectrum and elucidated theoretically, its relationship with bio-functions. In this case, we analyzed first the features of molecular structure of collagen and collected further the infrared spectrum of absorption of collagen and bovine serum albumin containing α-helix conformation in 400–4000 cm^-1 as well as their changes of strength of infrared absorption with varying temperatures using Fourier Transform–Infrared (FT-IR) spectrometers in the region of 15–95°C. The results show that there is a new band of 1650 cm^-1 close to the amide-I band of 1666 cm^-1 or 1670 cm^-1 in these bio-polymers, its strength decreases exponentially with increasing temperature of the systems, which can be expressed by exp[-(0.437 + 8.987 × 10^-6 T²)], but 1666 cm^-1 band increases linearly with increasing temperature. We calculated the energy spectrum of the protein molecules with α-helix conformation using the Soliton Theory of bio-energy transport, which are basically same with the experimental results measured by us. From these results and soliton theory we can conclude that the nonlinear soliton excitation, corresponding to 1650 cm^-1 band and the exciton excitation, is related to 1666 cm^-1 band, exists in the collagen and bovine serum albumin. In the meanwhile, these results also verified that the soliton theory of bio-energy transport along α-helix bio-polymers is appropriate to the protein molecules with α-helix conformation. Therefore, the studied results are helpful to elucidate the relationship between the molecular structure and bio-function of these bio-polymers.

This discussion about diagnostic tests for cancer incorporates a powerful branch of Physics namely X-ray diffraction. Although this technique was used to solve the DNA structure using the X-ray diffraction pictures of Rosalind Franklin,¹ and the structure of vitamin B12 by Dorothy Hodgkin² and hosts of other medical related structures, it is poorly understood by the general medical profession and the community at large. To the nonphysicist the patterns appear to have no relation to the results produced. It might as well be written in Greek. The well-known quote of Poincaré, the famous French mathematician and scientist, in 1885 comes to mind: "Science is built up with facts as a house is with stones. But a collection of facts is no more a science than a heap of stones is a house."

In order therefore to build a true understanding of this powerful technique it is necessary to build a firm understanding of the basic facts about this technique, so that the final results will be clear to all, as they will be held up by a firm house of knowledge. So let us take up the first stone.

Type I collagen fibrils have circular cross sections with radii mostly distributed in between 50 and 100 nm and are characterized by an axial banding pattern with a period of 67 nm. The constituent long molecules of those fibrils, the so-called triple helices, are densely packed but their nature is such that their assembly must conciliate two conflicting requirements. One is a double-twist around the axis of the fibril induced by their chirality and the other is a periodic layered organization, corresponding to the axial banding, built by specific lateral interactions. We examine here how such a conflict could contribute to the control of the radius of a fibril. We develop our analysis with the help of two geometrical archetypes: the Hopf fibration and the algorithm of phyllotaxis. The first one provides an ideal template for a twisted bundle of fibres and the second ensures the best homogeneity and local isotropy possible for a twisted dense packing with circular symmetry. This approach shows that, as the radius of a fibril with constant double-twist increases, the periodic layered organization can not be preserved without moving from planar to helicoidal configurations. Such changes of configurations are indeed made possible by the edge dislocations naturally present in the phyllotactic pattern. The distribution of those defects is such that the lateral growth of a fibril should stay limited in the observed range. Because of our limited knowledge about the elastic constants involved, this purely geometrical development stays at a quite conjectural level.

Tumor invasion, the process by which tumor cells break away from their primary tumor and gain access to vascular systems, is an important step in cancer metastasis. Most current 3D tumor invasion assays consisted of a single tumor cell embedded within an extracellular matrix (ECM). These assays taught us much of what we know today on how key biophysical (e.g., ECM stiffness) and biochemical (e.g., cytokine gradients) parameters within the tumor microenvironment guided and regulated tumor invasion. One limitation of the single tumor cell invasion assays was that it did not account for cell–cell adhesion within the tumor. In this paper, we developed a micrometer scale 3D co-culture spheroid invasion assay that recapitulated physiologically realistic tumor microenvironment and was compatible with microscopic imaging. Micrometer scale co-culture spheroids (1:1 ratio of metastatic breast cancer MDA-MB-231 and non-tumorigenic epithelial MCF-10A cells) were made using an array of microwells, and then were embedded within a collagen matrix in a microfluidic platform. Real time imaging of tumor spheroid invasion revealed that the spatial distribution of the two cell types within the tumor spheroid critically regulated tumor invasion. This work linked tumor architecture with tumor invasion and highlighted the importance of the biophysical cues within the bulk of the tumor in tumor invasion.

Collagen is the major component of the extracellular matrix in skin, tendon, cartilage, cornea, bone, etc., and as a main structural protein is the key determinant of mechanical and functional properties of tissues and organs. Proper balance between synthesis and degradation of collagen fibers is critical for maintaining normal physiologic function; therefore, the modification of collagen fibers in a controlled manner is of high importance for biomedicine. In this work, using second harmonic generation (SHG) and two-photon excited auto-fluorescence (TPEF) microscopy, we revealed that hypericin, a natural pigment extracted from plant, induced structural modification of collagen based tissues. Dynamics of the process was monitored by time-lapse multiphoton imaging. It was demonstrated that hypericin–mediated process was considerably irreversible and has a potential to be used for destroying of abnormal tissues and treatment of some diseases.

Tissue engineering is an innovative field of research applied to treat intestinal diseases. Engineered smooth muscle requires dense smooth muscle tissue and robust vascularization to support contraction. The purpose of this study was to use heparan sulfate (HS) and collagen coatings to increase the attachment of smooth muscle cells (SMCs) to scaffolds and improve their survival after implantation. SMCs grown on biologically coated scaffolds were evaluated for maturity and cell numbers after 2, 4 and 6 weeks in vitro and both 2 and 6 weeks in vivo. Implants were also assessed for vascularization. Collagen-coated scaffolds increased attachment, growth and maturity of SMCs in culture. HS-coated implants increased angiogenesis after 2 weeks, contributing to an increase in SMC survival and growth compared to HS-coated scaffolds grown in vitro. The angiogenic effects of HS may be useful for engineering intestinal smooth muscle.

Tumor invasion, the process by which tumor cells break away from their primary tumor and gain access to vascular systems, is an important step in cancer metastasis. Most current 3D tumor invasion assays consisted of a single tumor cell embedded within an extracellular matrix (ECM). These assays taught us much of what we know today on how key biophysical (e.g., ECM stiffiness) and biochemical (e.g., cytokine gradients) parameters within the tumor microenvironment guided and regulated tumor invasion. One limitation of the single tumor cell invasion assays was that it did not account for cell–cell adhesion within the tumor. In this chapter, we developed a micrometer scale 3D co-culture spheroid invasion assay that recapitulated physiologically realistic tumor microenvironment and was compatible with microscopic imaging. Micrometer scale co-culture spheroids (1:1 ratio of metastatic breast cancer MDA-MB-231 and non-tumorigenic epithelial MCF-10A cells) were made using an array of microwells, and then were embedded within a collagen matrix in a microfluidic platform. Real time imaging of tumor spheroid invasion revealed that the spatial distribution of the two cell types within the tumor spheroid critically regulated tumor invasion. This work linked tumor architecture with tumor invasion and highlighted the importance of the biophysical cues within the bulk of the tumor in tumor invasion.