The significant impact of mechanically-induced phase transformation on cellular functionality of biomedical austenitic stainless steel.

The implant surface and tissue experience strain when micro-motion occurs at the bone-implant interface under physiological loading. Moreover, strain is also introduced on the surface during mechanical processing of biomedical devices. Both these situations can induce phase transformation depending on the degree of stability of the microstructural constituents. In this regard, we elucidate here the interplay between mechanically-induced phase transformation (strain-induced martensite) in austenitic stainless steel on osteoblast functions. Strain-induced martensite significantly impacted cellular functions, notably, cell attachment, cell-surface interactions, proliferation, and synthesis of prominent proteins (fibronectin, actin, and vinculin). Strain-induced martensite favorably modulated cellular activity and contributed to small differences in hydrophilicity in relation to the non-strained austenitic stainless steel surface. The study provides a pathway for tuning biological functionality via microstructural control facilitated by mechanical strain.

Supramolecular structures fabricated through the epitaxial growth of semiconducting poly(3-hexylthiophene) on carbon nanotubes as building blocks of nanoscale electronics.

Semiconducting conjugated polymers such as (3-hexylthiophene) (P3HT) and carbon nanotubes are attractive for applications that include field-effect transistors and photovoltaic devices. In these applications, the control of structure, morphology, and alignment of polymer chains is important from the perspective of charge transport and optical properties. In this regard, a novel solution-based nucleation approach involving direct epitaxial nucleation of nanofibers of the poly(3-hexylthiophene) (P3HT) polymer on carbon nanotubes (CNTs) leading to supramolecular structure is demonstrated. The supramolecular structure of P3HT on CNTs is characterized by nucleation of oriented precursors of P3HT on CNTs by an epitaxial mechanism, onto which high density transcrystalline ∼800-1000 nm long nanofibrils of P3HT with a thickness of ∼2-3 nm are nucleated in a periodic manner. The nanoscale structure of epitaxially grown P3HT nanofibrils exhibits optical and photoluminescence characteristics. The UV-vis spectroscopy study of the fabricated structure suggests a combination of π-π electronic transition and a strong lattice vibration in the conjugated polymer chains. Furthermore, the supramolecular structure is envisaged to comprise an accumulating thread for charge transport, onto which nanometer thick long fibrils are assembled in a periodic configuration with strong potential for organic-inorganic optoelectronic devices. In conclusion, the described approach enables fabrication of supramolecular structure on carbon nanotube-based electrodes, making it attractive for functional devices.

Reduced toxicity and superior cellular response of preosteoblasts to Ti-6Al-7Nb alloy and comparison with Ti-6Al-4V.

There are serious concerns on the toxicity of vanadium in Ti-6Al-4V alloy. In this regard, we describe the biological footprint of Ti-6Al-4V and compare with a viable alternate Ti-6Al-7Nb alloy, in terms of novel experimentation pertaining to cellular activity that include qualitative and quantitative analysis of Feret's diameter of cells, area, and perimeter, and proteins-actin, vinculin, and fibronectin. Interestingly, Ti-6Al-7Nb was characterized by superior cell attachment, proliferation, viability, morphology, and spread, which were significantly different from Ti-6Al-4V alloy. Additionally, immunofluorescence studies demonstrated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions in Ti-6Al-7Nb alloy. These striking observations suggest enhanced cell-substrate interaction and activity on the surface of niobium-containing titanium alloy. The significant differences in the cellular response between the two alloys clearly point to the determining role of alloying element (Nb versus V) in a conclusive manner. Based on this study, next generation of titanium alloys is proposed to focus on niobium-containing alloy.