Chitins and chitosans for the repair of wounded skin, nerve, cartilage and bone

1.1. Biomineralization
The study of biomineralization is not only important to gain an understanding of how mineral-rich tissues are created in vivo but also because it is a great source of inspiration for the design of advanced materials.1-7 Mineralized tissues have remarkable hierarchical structures that have evolved over time to achieve great functions in a large variety of organisms. Organic phases play a key role in templating the structure of mineralized tissues; therefore, their matrices are often hybrid in composition, varying widely in the relative content of organic and inorganic substances. Understanding the complex integration of hard and soft phases that biology achieves in mineralized matrices across scales and its link to properties is knowledge of great value to materials chemistry. At the same time, the synthetic mechanisms used by biology to create mineralized matrices could also offer some useful strategies to create synthetic hybrid materials. Often, the amount of organic material utilized by Nature to modify mechanical properties of mineralized structures is vanishingly small. One example is the role of occluded proteins in the toughness of biogenic calcite.8 The study of mammalian bone and teeth in the biomineralization and biomimetic context is particularly interesting since the information derived could contribute a significant biomedical impact on therapies and strategies to repair or regenerate human mineralized tissues. This is an important area given the continually rising average life span of humans. The materials of interest could be highly sophisticated bioactive scaffolds to regenerate bone and possibly dental tissues as well. This review focuses on the formation of hydroxyapatite (HA) in synthetic systems designed primarily in the biomimetic context of bone or enamel mineralization for therapeutic approaches in repair of human tissues. Bone and enamel share the same mineral composition, HA, but have different morphologies and organic content. Enamel is almost entirely inorganic in composition, and bone has a relatively high organic composition. Knowledge acquired in this field may inspire the chemical synthesis of novel hybrid materials, including apatite-based structures for the regeneration of human bone and dental tissues.

Biomimetic Systems for Hydroxyapatite Mineralization Inspired By Bone and Enamel

No wonder you activities are, reading will be always needed. It is not only to fulfil the duties that you need to finish in deadline time. Reading will encourage your mind and thoughts. Of course, reading will greatly develop your experiences about everything. Reading molecular biology of the gene is also a way as one of the collective books that gives many advantages. The advantages are not only for you, but for the other peoples with those meaningful benefits.

Molecular Biology of the Gene.

http://barthelat-lab.mcgill.ca/files/papers/JPMS2009.pdf

Merger of structure and material in nacre and bone - Perspectives on de novo biomimetic materials

Multiscale modeling and simulation of polymer nanocomposites

Molecular interactions in intercalated organically modified clay and clay–polycaprolactam nanocomposites: Experiments and modeling

Nacre, the shiny inner layer of mollusk shells is a model biomimetic nanocomposite system. Its exceptional mechanical properties have been the inspiration for materials scientists for several decades. Nacre exhibits a layered brick and mortar structure. It is composed of 95% inorganic (aragonitic CaCO3) phase and 5% organic (mainly proteins and polysaccharides) phase that are arranged in interlocked brick and mortar architecture with the mineral as bricks and organics as the mortar. In the current work, we describe the dynamic nanomechanical behavior of nacre using dynamic nanoindentation (nano-DMA) experiments. Two sets of loads were applied to obtain the dynamic response from varying depths in nacre. These tests were performed at three different frequencies (25, 50, and 100 Hz) to study the effect of frequency on the dynamic properties of nacre. The loss modulus (E″) and the loss factor (tan δ) were measured. Both of these parameters were observed to increase with increase in depth. Significant increase in tan δ was observed with the increase in frequency. Photoacoustic Fourier transform infrared spectroscopic studies on nacre indicate the presence of water in nacre. This water may be present at nanograin interfaces in nacre platelets, at organic–inorganic interfaces, and also in the organic phase in nacre. We believe that water is one of the significant contributors to the viscoelasticity of nacre. Our results indicate that the aragonite platelets in nacre may also contribute to viscoelasticity.

Dynamic nanomechanical response of nacre

Role of coordinated metal ions on the orientation of phthalocyanine based coatings.

In our previous work, hydroxyapatite (HAP) was synthesized under two conditions: one in the presence of polyacrylic acid (in situ HAP) and the other in the absence of polyacrylic acid (ex situ HAP). Composites of both HAPs with polycaprolactone (PCL) were investigated for their applicability as scaffolds for bone tissue engineering. In the current work, bioactivity of these composites has been investigated by soaking them in simulated body fluid for different intervals of time. Nucleation and growth mechanism of apatite on these composites has also been investigated. Fourier transform infrared spectroscopy study suggests that although apatite growth starts with an intermediate phase, it completely transforms to HAP after 4 days of soaking. Nanoindentation results suggest that the apatite growing on in situ HAP/PCL composites has much higher hardness and elastic modulus as compared to the apatite growing on ex situ HAP/PCL composites. The apatite grown on the ex situ composites has a net-like interconnected structure. The observed differences in mechanical properties and morphology of apatite have been described on the basis of nucleation mechanisms. The nucleation of apatite on the in situ HAP/PCL composites proceeds through the formation of a complex between Ca2+ and COO− groups; on the other hand, nucleation occurs because of dissolution reaction of apatite in ex situ HAP/PCL composites. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006

Devendra Verma

Papers

Molecular interactions in intercalated organically modified clay and clay–polycaprolactam nanocomposites: Experiments and modeling

Dynamic nanomechanical response of nacre

Role of coordinated metal ions on the orientation of phthalocyanine based coatings.

Bioactivity in in situ hydroxyapatite-polycaprolactone composites.

Mechanical response and multilevel structure of biomimetic hydroxyapatite/polygalacturonic/chitosan nanocomposites