Table of Contents

Volume 2, Issue 2

  April/May/June 2012

  Pages 53 - 102

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 Issue Catalogue (MARC XML)

REVIEW

Open Access Article

Calcium orthophosphates and human beings: A historical perspective from the 1770s until 1940

Sergey V. Dorozhkin
Pages 53 - 70
http://dx.doi.org/10.4161/biom.21340
Abstract | Full Text | PDF

The historical development of a scientific knowledge on calcium orthophosphates from the 1770s until 1940 is described. Many forgotten and poorly known historical facts and approaches have been extracted from old publications and then they have been analyzed, systematized and reconsidered from the modern point of view. The chosen time scale starts with the earliest available studies of 1770s (to the best of my findings, calcium orthophosphates had been unknown before), passes through the entire 19th century and finishes in 1940, because since then the amount of publications on calcium orthophosphates rapidly increases and the subject becomes too broad. Furthermore, since publications of the second half of the 20th century are easily accessible, a substantial amount of them have already been reviewed by other researchers. The reported historical findings clearly demonstrate that the substantial amount of the scientific facts and experimental approaches have been known for very many decades and, in fact, the considerable quantity of relatively recent investigations on calcium orthophosphates is just either a further development of the earlier studies or a rediscovery of the already forgotten knowledge.




REPORTS

Open Access Article

Synthesis and characterization of biocompatible-nanohydroxyapatite crystals obtained by a modified sol-gel processing

Ignacio A. Figueroa, Omar Novelo-Peralta, Carlos Flores-Morales, Rodrigo González-Tenorio and M. Cristina Piña-Barba
Pages 71 - 76
http://dx.doi.org/10.4161/biom.20379
Abstract | Full Text | PDF

A modified sol-gel process for synthesizing nanocrystalline hydroxyapatite powders (nHA) for biomedical applications, using tetrahydrated calcium nitrate [Ca(NO₃)₂∙4H₂O] and phosphorous pentoxide [P₂O₅] as precursor, is presented and discussed. The powders were washed and heat-treated at different temperatures and then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The total process time reached with this modified process was less than 16 h. The results showed that there was an increment in size of the HA nanocrystals (nHA) when treated at different temperatures, ranging from 30 nm for the sample treated at 600°C to 500 nm for the sample heat-treated at 1200°C.

Open Access Article

In vitro degradation and release characteristics of spin coated thin films of PLGA with a “breath figure” morphology

Thiruselvam Ponnusamy, Louise B. Lawson, Lucy C. Freytag, Diane A. Blake, Ramesh S. Ayyala and Vijay T. John
Pages 77 - 86
http://dx.doi.org/10.4161/biom.20390
Abstract | Full Text | PDF

Poly (lactic-co-glycolic acid) (PLGA) coatings on implant materials are widely used in controlled drug delivery applications. Typically, such coatings are made with non-porous films. Here, we have synthesized a thin PLGA film coating with a highly ordered microporous structure using a simple and inexpensive water templating “breath figure” technique. A single stage process combining spin coating and breath figure process was used to obtain drug incorporated porous thin films. The films were characterized by scanning electron microscope (SEM) to observe the surface and bulk features of porosity and also, degradation pattern of the films. Moreover, the effect of addition of small amount of poly (ethylene glycol) (PEG) into PLGA was characterized. SEM analysis revealed an ordered array of ~2 µm sized pores on the surface with the average film thickness measured to be 20 µm. The incorporation of hydrophilic poly (ethylene glycol) (PEG) enhances pore structure uniformity and facilitates ingress of water into the structure. A five week in vitro degradation study showed a gradual deterioration of the breath figure pores. During the course of degradation, the surface pore structure deteriorates to initially flatten the surface. This is followed by the formation of new pinprick pores that eventually grow into a macroporous film prior to film breakup. Salicylic acid (highly water soluble) and Ibuprofen (sparingly water soluble) were chosen as model drug compounds to characterize release rates, which are higher in films of the breath figure morphology rather than in non-porous films. The results are of significance in the design of biodegradable films used as coatings to modulate delivery.

Open Access Article

Effect of cement fill ratio in loosening of hip implants

Elizabeth Gunn, Dinesh Gundapaneni and Tarun Goswami
Pages 87 - 93
http://dx.doi.org/10.4161/biom.20709
Abstract | Full Text | PDF

Femoral loosening is one of the most prevalent causes of revision orthopedic surgeries. Cement mantle thickness has been directly correlated with femoral loosening. If the mantle is too thick, there is an increased risk of radiolucent lines and inconsistent densities. Also, the more bone that is reamed out during the procedure can lead to instability, especially if the quality of the bone is compromised due to osteoporosis. Too thin of a mantle can lead to a higher probability for cement fracture, loosening the prosthetic even further. This study has shown that there is an ideal thickness range between two to five that should be kept. From radiographic images one can measure the thickness of the cement mantle showing the loosening characteristics.

Open Access Article

Evaluation of silicon nitride as a wear resistant and resorbable alternative for total hip joint replacement

Johanna Olofsson, T. Mikael Grehk, Torun Berlind, Cecilia Persson, Staffan Jacobson and Håkan Engqvist
Pages 94 - 102
http://dx.doi.org/10.4161/biom.20710
Abstract | Full Text | PDF

Many of the failures of total joint replacements are related to tribology, i.e., wear of the cup, head and liner. Accumulation of wear particles at the implants can be linked to osteolysis which leads to bone loss and in the end aseptic implant loosening. Therefore it is highly desirable to reduce the generation of wear particles from the implant surfaces.

Silicon nitride (Si₃N₄) has shown to be biocompatible and have a low wear rate when sliding against itself and is therefore a good candidate as a hip joint material. Furthermore, wear particles of Si₃N₄ are predicted to slowly dissolve in polar liquids and they therefore have the potential to be resorbed in vivo, potentially reducing the risk for aseptic loosening.

In this study, it was shown that α-Si₃N₄-powder dissolves in PBS. Adsorption of blood plasma indicated a good acceptance of Si₃N₄ in the body with relatively low immune response. Si₃N₄ sliding against Si₃N₄ showed low wear rates both in bovine serum and PBS compared with the other tested wear couples. Tribofilms were built up on the Si₃N₄ surfaces both in PBS and in bovine serum, controlling the friction and wear characteristics.