Papers by Author: S.N. Jayasinghe

Abstract: Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.

Abstract: In this paper a novel and versatile 3D print-patterning technique coupling electrohydrodyanmics and a specially designed and constructed plotting device is elucidated. This unit is capable of free-forming advanced ceramics and we demonstrate this by using it to print-pattern a 5mm × 5mm × 1mm walled zirconia structure layer by layer. The wall thickness achieved is ~150$m, almost half that of similar structures prepared using ink-jet printing. The as-printed structure was studied by scanning electron microscopy and some of its typical features are discussed and related to the forming process.

Abstract: Nano-sized HA (nHA) was applied to the surface of glass and titanium substrates using electrostatic atomisation spray (EAS) deposition. The phase purity of nHA was confirmed by X-ray diffraction. The nHA suspension consisted of rod–like particles 20-30nm in width and 50-100nm in length. The viscosity and conductivity of nHA suspension were 321 mPa s and 5.6 x 10-4 S/m, respectively. EAS of nHA in cone-jet mode was achieved at flow rate of 10-9 m3s-1 with the applied voltage between the needle and the ring-shaped ground electrode of ~6 kV. Micrometer- to submicrometerscaled nHA islands were successfully deposited on the substrate surface. Image analysis showed that the area percentage of nHA increased with deposition time, it covered 50% of the surface area after 10s of spraying. Partial dissolution of nHA was observed after immersion in deionised water for 1 month, particularly on the submicrometer sized nHA islands. Formation of a bone-like apatite layer was found after incubation in simulated body fluid (SBF K9) for 5 days, indicating the high bioactivity of the nHA deposits. In vitro culture with human osteoblast cells showed that the nHA islands were able to support the growth of HOB cells during 7 days of culture; the HOB cell activity increased with culture time as well as EAS deposition time. Immunofluorescence study showed that HOB cells expressed well-organised actin stress fibres on nHA deposited surfaces after 3 days of culture. The result indicated that nHA deposition provided more favourable surfaces for cell attachment. Therefore, electrostatic atomization spray deposition of nHA offers great potential for the creation of bioactive surfaces on bioinert implant surface to provide improved interfacial bonding with host tissues.

Abstract: Electrospraying of nano-sized hydroxyapatite (HA) has been used as a technique to modify the surface of alumina in order to achieve the goal of improving bone integration. A porous HA coating on alumina was produced by heat treating electrsprayed HA. Preliminary in vitro studies shown that this porous HA coating provided a favourable surface for attachment and growth of HOB cells. The results indicate that electrospraying is a very promising technique to create thin HA coatings on a range of biomedical implants to improve interfacial bonding with the host tissue.