Evaluating the influence on osteocyte mechanobiology within the lacunar-canalicular system for varying lacunar equancy and perilacunar elasticity: A multiscale fluid-structure interaction analysis.

The lacunar morphology and perilacunar tissue properties of osteocytes in bone can vary under different physiological and pathological conditions. How these alterations collectively change the overall micromechanics of osteocytes in the lacunar-canalicular system (LCS) of an osteon still requires special focus. Therefore, a Haversian canal and LCS-based osteon model was established to evaluate the changes in the hydrodynamic environment around osteocytes under physiological loading using fluid-structure interaction analysis, followed by a sub-modelled finite element analysis to assess the mechanical responses of osteocytes and their components. Osteocytes were modelled with detailed configurations, including cytoplasm, nucleus, and cytoskeleton, and parametric variations in lacunar equancy (L.Eq) and perilacunar elasticity (Pl.E) were considered within the osteon model. The study aimed to conduct a comparative study among osteon models with varying L. Eq and Pl. E to check the resulting differences in osteocyte mechanobiology. The results demonstrated that the average mechanical stimulation of each subcellular component of osteocytes increased with decreases in L. Eq and Pl. E, reflecting conditions typically seen in young, healthy bone as per previous literature. However, hydrodynamic responses, such as fluid flow and fluid shear stress on osteocytes, varied proportionally with the elasticity difference between the bone matrix and the perilacunar region during Pl. E variation. Additionally, the findings revealed that a minimal percentage of energy was used to transmit mechanical responses through microtubules from the cell membrane to the nucleus, and this energy percentage increased with higher L. Eq. The outcomes of the study could help to quantify how the osteocyte microenvironment and its mechanosensitivity within cortical bone changes with L. Eq and Pl. E alterations in different bone conditions, from young to aged and healthy to diseased.

A multiscale modeling to determine in vitro mechanical responses of different cells at the cell-substrate interface under fluid perfusion.

Investigating the influence of different cellular mechanical and physical properties on cells in vitro is important for assessing cellular activities like differentiation, proliferation, and migration. Evaluating the mechanical response of the cells lodged on a scaffold due to variations in substrate roughness, substrate elasticity, fluid flow, and the shapes of the cells is the main goal of the study. In this comprehensive analysis, a combination of the fluid structure interaction method and the submodeled finite element technique was employed to anticipate the mechanical responses across various cells at the interface between cells and the substrate. Fluid inlet velocity, substrate roughness, and substrate material were varied in this analysis. Different cell shapes were considered along with various components such as cell membrane, cytoplasm, nucleus, and cytoskeletons. This analysis shows the effect of these individual parameters on the elastic strain and strain energy density of cells at the cell-substrate interface. The results highlight that substrate roughness has a more significant impact on the mechanical response of cells at the interface than substrate elasticity. However, effect of the substrate elasticity becomes crucial for extremely soft substrate materials. The results of this research can be applied to identify the optimal parameters for fluid flow and create a suitable condition for cell culture.

Comparing the bone regeneration potential between a trabecular bone and a porous scaffold through osteoblast migration and differentiation: A multiscale approach.

Both cell migration and osteogenic differentiation are critical for successful bone regeneration. Therefore, understanding the mechanobiological aspects that govern these two processes is essential in designing effective scaffolds that promote faster bone regeneration. Studying these two factors at different locations is necessary to manage bone regeneration in various sections of a scaffold. Hence, a multiscale computational model was used to observe the mechanical responses of osteoblasts placed in different positions of the trabecular bone and gyroid scaffold. Fluid shear stresses in scaffolds at cell seeded locations (representing osteogenic differentiation) and strain energy densities in cells at cell substrate interface (representing cell migration) were observed as mechanical response parameters in this study. Comparison of these responses, as two critical factors for bone regeneration, between the trabecular bone and gyroid scaffold at different locations, is the overall goal of the study. This study reveals that the gyroid scaffold exhibits higher osteogenic differentiation and cell migration potential compared to the trabecular bone. However, the responses in the gyroid only mimic the trabecular bone in two out of nine positions. These findings can guide us in predicting the ideal cell seeded sites within a scaffold for better bone regeneration and in replicating a replaced bone condition by altering the physical parameters of a scaffold.

Evaluating the cell migration potential of TiO2 nanorods incorporated in a Ti6Al4V scaffold: A multiscale approach.

Improvement of cell migration by the nano-topographical modification of implant surface can directly or indirectly accelerate wound healing and osseointegration between bone and implant. Therefore, modification of the implant surface was done with TiO2 nanorod (NR) arrays to develop a more osseointegration-friendly implant in this study. Modulating the migration of a cell, adhered to a scaffold, by the variations of NR diameter, density and tip diameter in vitro is the primary objective of the study. The fluid structure interaction method was used, followed by the submodelling technique in this multiscale analysis. After completing a simulation over a global model, fluid structure interaction data was applied to the sub-scaffold finite element model to predict the mechanical response over cells at the cell-substrate interface. Special focus was given to strain energy density at the cell interface as a response parameter due to its direct correlation with the migration of an adherent cell. The results showed a huge rise in strain energy density after the addition of NRs on the scaffold surface. It also highlighted that variation in NR density plays a more effective role than the variation in NR diameter to control cell migration over a substrate. However, the effect of NR diameter becomes insignificant when the NR tip was considered. The findings of this study could be used to determine the best nanostructure parameters for better osseointegration.

1-Aza-15-Crown-5 Functionalized Graphene Oxide for 2D Graphene-Based Li⁺-ion Conductor.

Attachment of Li(+) ion on graphene surface to realize Li(+)-ion conductor is a real challenge because of the weak interaction between the ions and the functional groups of graphene oxide; although, a large number of theoretical results are already available in the literature. To overcome this problem, graphene oxide is functionalized by 1-aza-15-crown-5, the cage-like structure containing four oxygens that can bind Li(+) ion through electrostatic interaction. Li(+) migration on graphene surface has been investigated using ac relaxation mechanism. Perfect Debye-type relaxation behavior with ß (relaxation exponent) value ≈1 resulting from single ion is observed. The activation energy of Li(+) migration arising due to cation-π interaction is found to be 0.37 eV, which agrees well with recently reported theoretical value. It is believed that this study will help to design isolated ion conductors for Li(+)-ion battery.

Highly selective detection of trinitrophenol by luminescent functionalized reduced graphene oxide through FRET mechanism.

Among different nitro compounds, trinitrophenol (TNP) is the most common constituent to prepare powerful explosives all over the world. A few works on the detection of nitro explosives have already been reported in the past few years; however, selectivity is still in its infant stage. As all the nitroexplosives are highly electron deficient in nature, it is very difficult to separate one from a mixture of different nitro compounds by the usual photoinduced electron transfer (PET) mechanism. In the present work, we have used a bright luminescent, 2,6-diamino pyridine functionalized graphene oxide (DAP-RGO) for selective detection of TNP in the presence of other nitro compounds. The major advantage of using this material over other reported materials is not only to achieve very high fluorescence quenching of ∼96% but also superior selectivity >80% in the detection of TNP in aqueous medium via both fluorescence resonance energy transfer and PET mechanisms. Density functional theory calculations also suggest the occurrence of an effective proton transfer mechanism from TNP to DAP-RGO, resulting in this tremendous fluorescence quenching compared to other nitro compounds. We believe this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.

Emerging photoluminescence in azo-pyridine intercalated graphene oxide layers.

Inspite of being a potential material for electronic applications graphene possesses very poor optical properties, which need to be modified to make it suitable for optoelectronic devices. To achieve superior optical properties, graphene oxide (GO) sheets are functionalized with azo-pyridine to form a new intercalated structure with an interlayer separation of 0.9 nm. These azo-pyridine intercalated GO sheets show superior optical properties with bright blue emission via excited state intra-molecular proton transfer (ESIPT) which have potential applications in graphene based optoelectronic devices.

Characterization of micelle formation of dodecyldimethyl-N-2-phenoxyethylammonium bromide in aqueous solution.

Aggregation behavior of dodecyldimethyl-N-2-phenoxyethylammonium bromide commonly called domiphen bromide (DB) was studied in aqueous solution. The Krafft temperature of the surfactant was measured. The surfactant has been shown to form micellar structures in a wide concentration range. The critical micelle concentration was determined by surface tension, conductivity, and fluorescence methods. The conductivity data were also employed to determine the degree of surfactant counterion dissociation. The changes in Gibb's free energy, enthalpy, and entropy of the micellization process were determined at different temperature. The steady-state fluorescence quenching measurements with pyrene and N-phenyl-1-naphthylamine as fluorescence probes were performed to obtain micellar aggregation number. The results were compared with those of dodecyltrimethylammonium bromide (DTAB) surfactant. The micelle formation is energetically more favored in DB compared to that in DTAB. The 1H-NMR spectra were used to show that the 2-phenoxyethyl group, which folds back onto the micellar surface facilitates aggregate formation in DB.