Surface properties and cytocompatibility of Ti-6Al-4V fabricated using Laser Engineered Net Shaping.

Direct laser deposition (DLD) is one of the rapidly emerging laser-based additive manufacturing (LBAM) process. Laser Engineered Net Shaping (LENS) is one such DLD technique which was employed to fabricate one of the widely used Ti-6Al-4V implant material with enhanced surface-related properties compared to the wrought sample (commercially available). Wear and corrosion behavior of LENS fabricated Ti-6Al-4V (L-Ti64) was characterized using low-frequency reciprocatory wear tester and potentiostat. Sample hardness was determined using Vickers's microhardness test. Adhesion and morphology of Human mesenchymal stem cells (hMSCs) on the samples were examined using Scanning Electron Microscopy (SEM) and fluorescence microscope whereas the quantification of live cells was determined using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to determine the concentration of leached-out metal ions during wear test. All the above mentioned surface-related properties were compared to that of wrought Ti-6Al-4V (W-Ti64) to standardize the efficiency of LENS-fabricated materials (L-Ti64) when compared to its wrought counterpart. The results clearly indicated stable passive behavior of L-Ti64, which was evident from the lower corrosion rate and high passive range obtained. L-Ti64 exhibited improved hardness level than W-Ti64 by 8% which enhanced the wear resistance and also prevented the release of wear debris. However, in presence of FBS, coefficient of friction (COF) increased by about 21 and 33% for L-Ti64 and W-Ti64 respectively, which inturn accelerated the wear rate of both the samples. Low cytotoxicity and well spread morphology of human Mesenchymal Stem Cells (hMSC's) affirmed higher level of biocompatibility of both the samples. However, no significant differences in the cellular behaviors were observed.

Surface engineering of LENS-Ti-6Al-4V to obtain nano- and micro-surface topography for orthopedic application.

Two distinct surface topographies consisting of micro- and nano-surface were developed using laser texturing (LT) and anodization process respectively and their effect on the surface-related properties of Ti-6Al-4V fabricated using Laser Engineered Net Shaping (LENS) were determined. The topographies developed using laser texturing (25, 50 and 75% overlap) were examined using 3D profilometer, whereas, Field Emission Scanning Electron Microscopy (FE-SEM) was used to analyze Titania NanoTubes (TNT) formed using anodization. Though all the surface modified specimens exhibited hydrophilic behavior, least contact angle values were observed for the specimen surface modified with TNT. 25LT and 50LT specimens offered about 8 fold higher corrosion resistance than TNT specimens. All the surface modified samples exhibited non-toxicity to blood cells as well as to the mesenchymal stem cells (hMSCs) with a higher rate of proliferation and differentiation hMSCs observed on 75LT specimens and TNT specimen.