Journal of Biomimetics, Biomaterials and Tissue Engineering Vol. 5

Abstract: A new class of osteoconductive and osteoinductive combination biomaterials composed of calcium phosphate cement (CPC), demineralized bone matrix (DBM) and a water-soluble viscosity modifier were prepared and characterized in-vitro and in-vivo. In previous studies, a range of combinations formulations were tested in order to compare their performance characteristic. In-vitro characterization results show that the mechanical strength is decreased when the amount of DBM increases. However, DBM does not affect the CPC’s ability to set hard and convert to nanocrystalline apatitic calcium phosphate, which shares the chemical structure of natural bone as seen in x-ray diffraction. It is known that the DBM alone is osteoinductive. In-vivo osteoinductivity testing of the formulations in an intramuscular, athymic rat model demonstrated that the combination material is also osteoinductive. Two formulations were chosen for in-vivo efficacy testing based on the results of in-vitro and in-vivo characterization. These formulations were studied using rabbit critical-sized femoral core defect model. The formulations were composed of DBM with particle sizes of 250 to 710 μm, carboxymethyl-cellulose (CMC) as the viscosity modifier and weight percent compositions of 50% DBM/ 45% CPC/ 5% CMC and 60% DBM/ 30% CPC/ 10% CMC. Bone integration and healing was graded at 6, 12, and 24 weeks. The two formulations were compared to the gold standard autograft at 12 weeks and to an empty defect as the negative control at 24 weeks. Based on micro-computed topography (μCT), both formulations allowed for continuity of bone throughout the defect region at all time points. No differences in dense area fraction were seen between two formulations at 6 weeks (p = 0.8661). There was no significant statistical difference between the two formulations and autograft at 12 weeks (p = 0.2467). At 24 weeks, both formulations had significantly higher dense area fractions than empty controls (p = 0.0001). Histologically, the biology of the treatment areas appeared to have returned to normal by 24 weeks with CPC appearing to be the principal osteogenic inducer. In conclusion, these combinations of CPC and DBM offers significant advantages (handling, mechanical properties and osteoinductivity) over current DBM products and can be an effective alternative to autograft in healing of bone defects.

Abstract: Dysfunction of the corneal endothelium due to cell loss caused by aging, disease or trauma can lead to severe visual impairment and blindness. Traditionally, dysfunctional endothelia are managed surgically, by removing the entire central cornea and transplanting either donor corneal tissue (penetrating keratoplasty), or just endothelia isolated from donor corneas. As in many cases it is only the corneal endothelium requiring replacement, many attempts were made over the last decades to develop an endothelial substitute, thereby precluding the need for the use of full donor corneas. This article reviews these attempts, which include artificial membranes, cell-coated corneal transplants, and cell-coated membranes. The presumption of an artificial corneal endothelium capable of duplicating the transendothelial ion-and-fluid transport function is examined in light of the latest hypotheses regarding the mechanism of this function.

Abstract: The hydrothermal reaction at 250°C between crocodile eggshells and three phosphate precursors, (NH4)2HPO4, Ca3(PO4)2 and H3PO4 were studied. Only (NH4)2HPO4 and Ca3(PO4)2 precursors gave monophasic hydroxyapatite within 25 and 8 h, respectively. Pure hydroxyapatite could not be produced when using H3PO4. The characteristic vibration for PO43- are observed at 566-603, 1043-1093, 962-963 and 466-474 cm-1 and for OH- group at 3570-3572 and 633-634 cm-1. The morphology of the prepared hydroxyapatite is agglomerated plate-like crystals. The Ca/P ratio by ICP method is 1.62-1.64.

Abstract: This manuscript reviews about titanium surface modification techniques for its application in orthopaedic and dental implants. There are a few limitations in the long term prognosis of orthopaedic and dental implants. Poor osseointegration with bone, periimplant infection leading to implant failure and short term longevity demanding revision surgery, are to mention a few. Micro- and nanoscale modification of titanium surface using physicochemical, morphological and biochemical approaches have resulted in higher bone to implant contact ratio and improved osseointegration. With recent advances in micro, nano-fabrication techniques and multidisciplinary research studies focusing on bridging biomaterials for medical applications, TiO2 nanotubes have been extensively studied for implant applications. The need for titanium implant surface that can closely mimic the nanoscale architecture of human bone has become a priority. For such purpose, TiO2 nanotubes of different dimensions and architectural fashions at the nanoscale level are being evaluated. This manuscript discusses in brief about the in-vitro and in-vivo studies on titanium surface modification techniques. This manuscript also addresses the recent studies done on such nanotubular surfaces for the effective delivery of osteoinductive growth factors and anti bacterial/ anti inflammatory drugs to promote osseointegration and prevent peri-implant infection.

Abstract: Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, can be bioinert, bioresorbable and bioactive, as well as porous for tissue ingrowth. This review is devoted to calcium orthophosphates, which belong to the categories of bioresorbable and bioactive bioceramics. There have been a number of major advances made in this field during the past 30 – 40 years. From initial work on development of bioceramics that were tolerated in the physiological environment, emphasis has now shifted towards the use of bioceramics that interact with bone tissue by forming a direct bond. By structural and compositional control, it is now possible to choose whether the bioceramics of calcium orthophosphates are biologically stable once incorporated within the skeletal structure or whether they are resorbed over time. Current biomedical applications of calcium orthophosphate bioceramics include replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery.