Sureshan Sivananthan

Porous polymer/hydroxyapatite scaffolds: characterization and biocompatibility investigations

Poly-lactic-glycolic acid (PLGA) has been widely used as a scaffold material for bone tissue engineering applications. 3D sponge-like porous scaffolds have previously been generated through a solvent casting and salt leaching technique. In this study, polymer–ceramic composite scaffolds were created by immersing PLGA scaffolds in simulated body fluid, leading to the formation of a hydroxyapatite (HAP) coating. The presence of a HAP layer was confirmed using scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy in attenuated total reflection mode. HAP-coated PLGA scaffolds were tested for their biocompatibility in vitro using human osteoblast cell cultures. Biocompatibility was assessed by standard tests for cell proliferation (MTT, WST), as well as fluorescence microscopy after standard cell vitality staining procedures. It was shown that PLGA–HAP composites support osteoblast growth and vitality, paving the way for applications as bone tissue engineering scaffolds.

Comparison of in vitro biocompatibility of NanoBone(®) and BioOss(®) for human osteoblasts.

INTRODUCTION Scaffolds for bone tissue engineering seeded with the patients own cells might be used as a preferable method to repair bone defects in the future. With the emerging new technologies of nanostructure design, new synthetic biomaterials are appearing on the market. Such scaffolds must be tested in vitro for their biocompatibility before clinical application. However, the choice between a natural or a synthetic biomaterial might be challenging for the doctor and the patient. In this study, we compared the biocompatibility of a synthetic bone substitute, NanoBone(®) , to the widely used natural bovine bone replacement material BioOss(®) . MATERIAL AND METHODS The in vitro behaviour of human osteoblasts on both materials was investigated. Cell performance was determined using scanning electron microscopy (SEM), cell vitality staining and four biocompatibility tests (LDH, MTT, WST, BrdU). RESULTS We found that both materials showed low cytotoxicity and good biocompatibility. The MTT proliferation test was superior for Nanobone(®) . DISCUSSION Both scaffolds caused only little damage to human osteoblasts and justify their clinical application. However, NanoBone(®) was able to support and promote proliferation of human osteoblasts slightly better than BioOss(®) in our chosen test set-up. The results may guide doctors and patients when being challenged with the choice between a natural or a synthetic biomaterial. Further experiments are necessary to determine the comparison of biocompatibility in vivo.

Antimicrobial peptide immunity protects human nasal and auricular cartilage against infection

Background: Despite being impervious to surveillance by the adaptive immune system because of its lack of vascularity, infection of the nasal and auricular cartilage after surgery such as rhinoplasty or otoplasty is rare. Why is this so? Our goal was to determine whether the expression of antimicrobial peptides provides a previously unrecognized nonepithelial layer of innate immune defense within the nasal and auricular cartilage. Materials and Methods: Seven samples of nasal septum cartilage and 2 biopsies from auricular cartilage grafts were harvested during rhinoplasty and otoplasty procedures. Ten cadaveric samples of auricular and 9 samples of nasal cartilage were also obtained. Immunohistochemical staining was directed against the human &bgr;-defensin antimicrobial peptides (hBD) 1, 2, and 3. A semiquantitative analysis was performed to measure immunoreactivity. Results: All 3 human &bgr;-defensins were detected along the perichondral line and within the cartilage matrix in the nasal and auricular samples. Areas with positive immunohistochemical staining were also detected within chondrocyte cytoplasm. Conclusions: We provide the first evidence of antimicrobial peptide expression (hBD-1, -2 and -3) within the perichondrium and cartilage matrix layers of the nasal and auricular cartilage. This previously unrecognized innate immune function of perichondrocytes and chondrocytes may explain the resistance of the nasal and auricular cartilage to infection after surgical procedures despite the absence of a vascular system.

Design of a Mechanical Stimulator for In Vivo Tissue Engineering of a Diarthrosislike Structure

This paper proposes the conceptual design of a mechanical stimulator that uses a tissue engineering strategy to develop a diarthrosislike structure in vivo. The adopted design approach is based on a function analysis. The approach has resulted in the design of a stimulator consisting of four components: cages, a compliant four-bar mechanism, a transmission mechanism, and a fixation component. The implanted stimulator is driven by internal body power, particularly by the longitudinal deformation of a skeletal muscle. The compliant mechanism is designed to impose controlled shear and compressive strain to the growing joint construct in order to initiate cartilage formation. The paper emphasizes the conceptual design and its rationale. Evaluation using finite element analysis was performed, which showed that the design meets the technical demands. Titanium prototypes were fabricated for stiffness and endurance testing.

Design of an Endoreactor for the Cultivation of a Joint-Like-Structure

To avoid revision surgeries in artificial joint replacements and to allow young people to have a joint replacement, using biological joint replacement created by tissue engineering is a promising alternative. Several research groups have tissue engineered bone [Warnke 2004] and cartilage [Chung 2007] separately. The tissue engineering of a joint, consisting of bone and cartilage is the next frontier. The present study focuses on the design of a novel device, named Endoreactor, that is employing the mechanosensitivity of cells to create a joint-like-structure (JLS) consisting of a bone and cartilage sandwich, similar to an amphiarthrosis, by applying a mechanical loading regime to a stem cell seeded scaffold construct during endocultivation. This way, the patients who will eventually need the new joint will serve as their own bioreactor, having the joint grow in their own body. In the JLS, the outside layers are designed to become bone, using a 6 mm thick scaffold with high stiffness. The center layer is a 4 mm thick scaffold which is compliant so as to experience more strain than the outside scaffolds to stimulate cartilage formation. Compression is realized by placing the JLSs between the long links of a kite-shaped four-bar linkage. This Endoreactor is powered by natural body motion through connection to the musculoskeletal system of the host, which in the experimental phase is a Gottingen minipig. The loading frequency and rest versus active time is dictated by the activity level of the minipig. This results in a natural loading pattern that is employed for the stimulation of cartilage formation in the JLS. A tensile force created during ambulation is converted into compressive action between the two long links of the mechanism. A mechanical stop limits the motion. This way controlled intermittent dynamic compression between 2.5% and 12.5% is realized in the cartilage layer of the JLS. All functions are integrated into a single piece compliant mechanism which is produced out of titanium using 3D rapid prototyping by selective laser melting technology. The mechanism can be fitted with cages that hold the scaffolds for bone and cartilage in place and protect them from external loads while being implanted. A safety spring was added to accommodate for large actuation excursions. A number of prototypes were produced and tested for fatigue, plastic deformation, failure load, and displacements of the long links at the JLS locations under different axial loads. These tests confirmed the proper mechanical functioning of the Endoreactor. Work with animal models making use of the device to culture an amphiarthosis-like joint is foreseen in the near future. This work was carried out at part of MYJOINT: Living Bioreactor—Growing a New Joint in a Human Back, EU FP6-2004-NEST-C-1, Proposal No. 028861.

Huiles essentielles antibactériennes chez des patients à tumeurs cancéreuses malodorantes

RésuméLes ulcères nécrotiques malodorants cancéreux sont un souci majeur puisqu’ils conduisent à l’isolement social et à une mauvaise qualité de vie. Les médications actuelles et les traitements topiques ont prouvé qu’ils n’étaient pas adaptés pour réduire l’odeur de pourri à des niveaux acceptables. Nous rapportons ici notre expérience positive par l’utilisation des huiles essentielles antibactériennes chez des patients souffrant de cancers curables de la tête et du cou, accompagnés d’ulcération nécrotique malodorante. Tous les patients ont reçu un traitement avec une antibiothérapie orale ou systémique. De plus, les ulcères ont été nettoyés deux fois par jour avec une préparation d’huiles essentielles antibactériennes mélangées (Kielmix®). Tous les patients ont fait l’expérience d’une résolution complète de l’odeur de pourri au troisième ou au quatrième jour du traitement. Comme autre effet, nous avons noté, en dehors de la réduction de l’odeur nauséabonde, l’effet anti-inflammatoire sur les ulcérations. Chez certains patients, les ulcérations ont commencé à guérir et sont parvenues à une complète reépithélisation. Les patients ont pu percevoir une résolution de leur état nauséabond. La qualité de vie a été améliorée significativement avec une reprise des contacts sociaux avec les membres de la famille et leurs connaissances.AbstractMalodorous necrotic ulcers in cancer patients are of major concern as it leads to social isolation and poor quality of life. Current medications and topical therapies have proven inadequate in their ability to reduce foul smell to acceptable levels. We report the positive experience we have had in using antibacterial essential oils in patients with incurable head and neck cancer and associated malodorous necrotic ulcers. All patients received a standard course of therapy with oral or systemic antibiosis. In addition, we rinsed the ulcers with an antibacterial essential oil mix (mainly based on eucalyptus oil) twice a day. All patients experienced complete resolution of the foul smell by only the third or fourth day of therapy. As a secondary effect we saw that besides smell reduction the oils had anti-inflammatory effects on cancer ulcers. In some patients ulcers started to heal and achieved complete re-epithiliazation. The patients experienced great personal relief upon resolution of their malodorous conditions. Quality of life improved significantly with the resulting reintroduction of social contact with friends and relatives.