Derivation, validation, and prediction of loading-induced mineral apposition rates at endocortical and periosteal bone surfaces based on fluid velocity and pore pressure.

The capacity of bone to optimize its structure in response to mechanical loads has been widely observed. The mechanical load acting on a bone at the macroscopic level influences the bone cells, particularly osteocytes within the lacunae canalicular network (LCN). Osteocytes are responsive to a range of physical signals, including strain, interstitial fluid flow, and pore pressure. However, physiological tissue strain is known to be typically smaller than that required to directly induce bone formation. On the other hand, as per evidence provided by this study from the literature, models based on fluid flow alone cannot simultaneously predict bone formation at both the periosteal and endocortical surfaces. This suggests that another component of the osteocyte's mechanical environment, such as pore pressure, may play an essential role in bone adaptation, either alone or in combination with other stimuli, such as tissue strain and/or interstitial fluid flow. In vitro experiments have also confirmed that osteocytes respond to cyclic pore pressure and, thus, have a mechanism to sense the pressure, possibly because of its viscoelasticity. In this work, dissipation energy density, being irreversible work done per unit volume, has been successfully used as a greater stimulus to incorporate all of the parameters of mechanical environments of the LCN, such as waveforms of both fluid velocity and pore pressure, number of loading cycles. Mineral Apposition Rate (MAR) has also been mathematically derived to be proportional to the square root of the dissipation energy density minus its reference value. A hypothesis is accordingly proposed and successfully tested/validated for both endocortical and periosteal surfaces with respect to an in-vivo study on mouse tibia available in the literature. The constant of proportionality and the reference/threshold value of the dissipation energy density are determined through a nonlinear curve fitting. The mathematical/computational method thus developed is then successfully used to predict MAR at both endocortical and periosteal surfaces induced by a different loading condition. Computational implementation of the mathematical model has been done through a poroelastic finite element analysis of bone, where bone is assumed to be porous and filled with fluid, with a boundary condition that the periosteum is impermeable to the fluid and the endosteal surface maintains a reference zero pressure. This work also provides evidence for these assumptions to be true based on the state-of-the-art literature on related experimental studies. The currently developed model shows that the bone uses these conditions (assumptions) to its advantage, as the greater stimulus, i.e., the dissipation energy due to both fluid flow and pore pressure, are of a similar order at both the surfaces, and hence osteogenesis of the same order at both the surfaces. As a bottom line, the resulting model is the first of its kind as it has been able to correctly predict MAR at both endocortical and periosteal surfaces. This study thus significantly advances the modeling of cortical bone adaptation to exogenous mechanical loading.

Encapsulation of Cymbopogon khasiana × Cymbopogon pendulus Essential Oil (CKP-25) in Chitosan Nanoemulsion as a Green and Novel Strategy for Mitigation of Fungal Association and Aflatoxin B1 Contamination in Food System.

The present study deals with the encapsulation of Cymbopogon khasiana × Cymbopogon pendulus essential oil (CKP-25-EO) into a chitosan nanoemulsion and efficacy assessment for inhibition of fungal inhabitation and aflatoxin B1 (AFB1) contamination in Syzygium cumini seeds with emphasis on cellular and molecular mechanism of action. DLS, AFM, SEM, FTIR, and XRD analyses revealed the encapsulation of CKP-25-EO in chitosan with controlled delivery. The CKP-25-Ne displayed enhanced antifungal (0.08 µL/mL), antiaflatoxigenic (0.07 µL/mL), and antioxidant activities (IC50 DPPH = 6.94 µL/mL, IC50 ABTS = 5.40 µL/mL) in comparison to the free EO. Impediment in cellular ergosterol, methylglyoxal biosynthesis, and in silico molecular modeling of CKP-25-Ne validated the cellular and molecular mechanism of antifungal and antiaflatoxigenic activity. The CKP-25-Ne showed in situ efficacy for inhibition of lipid peroxidation and AFB1 secretion in stored S. cumini seeds without altering the sensory profile. Moreover, the higher mammalian safety profile strengthens the application of CKP-25-Ne as a safe green nano-preservative against fungal association, and hazardous AFB1 contamination in food, agriculture, and pharmaceutical industries.

An in silico model for woven bone adaptation to heavy loading conditions in murine tibia.

Existing in silico models for lamellar bone adaptation to mechanical loading are unsuitable for predicting woven bone growth. This anomaly is due to the difference in mechanobiology of the woven bone with respect to that of the lamellar bone. The present study is aimed at developing an in silico bone-adaptation model for woven bone at cellular and tissue levels. The diffusion of Ca2+ ions reaching lining cells from the osteocytic network and the bone cortex in response to a mechanical loading on the cortical bone has been considered as a stimulus. The diffusion of ions within osteocytic network has been computed with a lacunar-canalicular network (LCN) in which bone cells are uniformly arranged. Strain energy density is assumed to regulate ion flow within the network when the induced normal strain is above a threshold level. If the induced strain exceeds another higher threshold level, then the strain with a power constant is additionally assumed to regulate the stimulus. The intracellular flow of Ca2+ ions within the LCN has been simulated using Fick's laws of diffusion, using a finite element method. The ion diffusion from bone cortex to vesicles has been formulated as a normal strain with a power constant. The stimuli reaching the surface cells are assumed to form the new bone. The mathematical model closely predicts woven bone growth in mouse and rat tibia for various in vivo loading conditions. This model is the first to predict woven bone growth at tissue and cellular levels in response to heavy mechanical loading.

A Simplistic Approach to Bone Healing Simulation.

A simple computational approach to simulation of healing in long bone fractures is presented. In particular, an algorithm that could simulate the formation, maturation, and resorption of fracture callus is developed and validated. The simplicity of the approach lies in the fact that the algorithm uses only the applied load and a single constraint parameter for the entire simulation. The work hypothesizes bone healing as a comprehensive energy minimization process where mechanical stimulation is proposed as the primary precursor for the beginning of different stages (i.e., callus formation, mineralization, and resorption). As such, the hypothesis is derived from the second law of thermodynamics which states that the energy of a closed system should be minimum at equilibrium. Alternatively, each stage of healing bone healing may be termed a state of homeostasis. The validation is done through a multi-material, time-based simulation of bone healing in a damaged tibia. The simulation uses a cross-section-based finite element model and an advanced version of an already validated structural optimization algorithm. The optimization objective is to minimize overall strain energy for the entire process, subject to a polar first moment of mass constraint. The simulation results show different stages of healing, where the algorithm generates a callus geometry similar to those observed experimentally. Eventually, a geometry similar to that in an intact cross-section is achieved by resorption of the callus from the unwanted sites.

Synthesis, characterization and in situ bioefficacy evaluation of Cymbopogon nardus essential oil impregnated chitosan nanoemulsion against fungal infestation and aflatoxin B1 contamination in food system.

The present investigation aimed to synthesize Cymbopogon nardus essential oil impregnated chitosan nanoemulsion (Ne-CNEO) and its practical efficacy as novel green delivery system for protection of Syzygium cumini seeds against broad range storage fungi, aflatoxin B1 (AFB1) secretion and lipid peroxidation. Chemical characterization of CNEO revealed citral (62.73%) as major component. Successful impregnation of CNEO inside chitosan nanoemulsion was confirmed through SEM, AFM and FTIR analyses. In vitro release study showed biphasic release profile with initial burst followed by sustained release of CNEO from chitosan nanomatrix. Ne-CNEO exhibited enhancement in in vitro antifungal, antiaflatoxigenic (0.16 µL/mL) and antioxidant activity over CNEO. The antifungal and antiaflatoxigenic mechanism of action of Ne-CNEO was associated with inhibition of ergosterol biosynthesis, increased leakage of cellular contents, and impairment in cellular methylglyoxal biosynthesis. In silico modeling validated interaction of citral with Ver-1 and Omt-A proteins, confirming the molecular action for inhibition of AFB1 production. In situ investigation suggested remarkable protection of S. cumini seeds against fungal inhabitation, AFB1 production and lipid peroxidation without affecting organoleptic attributes. Furthermore, higher mammalian non-toxicity strengthens the application of Ne-CNEO as safe nano-green and smart preservative in place of adversely affecting synthetic preservatives in emerging food, agriculture and pharmaceutical industries.

Rescuing loading induced bone formation at senescence.

The increasing incidence of osteoporosis worldwide requires anabolic treatments that are safe, effective, and, critically, inexpensive given the prevailing overburdened health care systems. While vigorous skeletal loading is anabolic and holds promise, deficits in mechanotransduction accrued with age markedly diminish the efficacy of readily complied, exercise-based strategies to combat osteoporosis in the elderly. Our approach to explore and counteract these age-related deficits was guided by cellular signaling patterns across hierarchical scales and by the insight that cell responses initiated during transient, rare events hold potential to exert high-fidelity control over temporally and spatially distant tissue adaptation. Here, we present an agent-based model of real-time Ca(2+)/NFAT signaling amongst bone cells that fully described periosteal bone formation induced by a wide variety of loading stimuli in young and aged animals. The model predicted age-related pathway alterations underlying the diminished bone formation at senescence, and hence identified critical deficits that were promising targets for therapy. Based upon model predictions, we implemented an in vivo intervention and show for the first time that supplementing mechanical stimuli with low-dose Cyclosporin A can completely rescue loading induced bone formation in the senescent skeleton. These pre-clinical data provide the rationale to consider this approved pharmaceutical alongside mild physical exercise as an inexpensive, yet potent therapy to augment bone mass in the elderly. Our analyses suggested that real-time cellular signaling strongly influences downstream bone adaptation to mechanical stimuli, and quantification of these otherwise inaccessible, transient events in silico yielded a novel intervention with clinical potential.

Modeling cortical bone adaptation using strain gradients.

Cyclic and low-magnitude loading promotes osteogenesis (i.e. new bone formation). Normal strain, strain energy density and fatigue damage accumulation are typically considered as osteogenic stimuli in computer models to predict site-specific new bone formation. These models however had limited success in explaining osteogenesis near the sites of minimal normal strain, for example, neutral axis of bending. Other stimuli such as fluid motion or strain gradient also stimulate bone formation. In silico studies modeled the new bone formation as a function of fluid motion, however, computation of fluid motion involves complex mathematical calculations. Strain gradients drive fluid flow and thus can also be established as the stimulus. Osteogenic potential of strain gradients is however not well established. The present study establishes strain gradients as osteogenic stimuli. Bending-induced strain gradients are computed at cortical bone cross-sections reported in animal loading in vivo studies. Correlation analysis between strain gradients and site of osteogenesis is analyzed. In silico model is also developed to test the osteogenic potential of strain gradients. The model closely predicts in vivo new bone distribution as a function of strain gradients. The outcome establishes strain gradient as computationally easy and robust stimuli to predict site-specific osteogenesis. The present study may be useful in the development of biomechanical approaches to mitigate bone loss.

Assessing the Levisticum officinale Koch. essential oil as a novel preservative for stored chia seeds (Salvia hispanica L.) with emphasis on probable mechanism of action.

The present study was undertaken to explore the inhibitory effect of Levisticum officinale Koch. essential oil (LoffEO) on the growth and aflatoxin B1 secretion by Aspergillus flavus (AF-LHP-SH1, aflatoxigenic strain) causing deterioration of stored chia seeds (Salvia hispanica). The chemical profile analysis of LoffEO by GC-MS analysis revealed the presence of α-terpinyl acetate (26.03 %) as a major component followed by terpineol <1- > (24.03 %) and citronellal (24.03 %). Results on antifungal and antiaflatoxigenic activity indicated that LoffEO at 2.0 and 1.75 µL/mL caused complete inhibition of growth and aflatoxin B1 production, respectively. Antifungal toxicity of LoffEO was strongly correlated with the inhibition of ergosterol content, leakage of cellular ions, and disintegration of membrane permeability. Reduction in cellular methylglyoxal by LoffEO indicated a novel antiaflatoxigenic mechanism of action. The LoffEO showed moderate free radical quenching activity in DPPH assay (IC50 = 26.10 µL/mL) and exhibited remarkable inhibitory efficacy against lipid peroxidation of chia seeds. In addition, LoffEO presented strong in situ antiaflatoxigenic efficacy, and exhibited non-phytotoxic nature, acceptable sensory characteristics, and favorable safety profile (LD50 = 19786.59 µL/kg), which recommends its practical utilization as a novel and safe preservative to improve the shelf life of stored chia seeds from fungal infestation and aflatoxin B1 contamination.

Essential Oil Nanoemulsion as Eco-Friendly and Safe Preservative: Bioefficacy Against Microbial Food Deterioration and Toxin Secretion, Mode of Action, and Future Opportunities.

Microbes are the biggest shareholder for the quantitative and qualitative deterioration of food commodities at different stages of production, transportation, and storage, along with the secretion of toxic secondary metabolites. Indiscriminate application of synthetic preservatives may develop resistance in microbial strains and associated complications in human health with broad-spectrum environmental non-sustainability. The application of essential oils (EOs) as a natural antimicrobial and their efficacy for the preservation of foods has been of present interest and growing consumer demand in the current generation. However, the loss in bioactivity of EOs from fluctuating environmental conditions is a major limitation during their practical application, which could be overcome by encapsulating them in a suitable biodegradable and biocompatible polymer matrix with enhancement to their efficacy and stability. Among different nanoencapsulated systems, nanoemulsions effectively contribute to the practical applications of EOs by expanding their dispersibility and foster their controlled delivery in food systems. In line with the above background, this review aims to present the practical application of nanoemulsions (a) by addressing their direct and indirect (EO nanoemulsion coating leading to active packaging) consistent support in a real food system, (b) biochemical actions related to antimicrobial mechanisms, (c) effectiveness of nanoemulsion as bio-nanosensor with large scale practical applicability, (d) critical evaluation of toxicity, safety, and regulatory issues, and (e) market demand of nanoemulsion in pharmaceuticals and nutraceuticals along with the current challenges and future opportunities.

Improvement of in vitro and in situ antifungal, AFB1 inhibitory and antioxidant activity of Origanum majorana L. essential oil through nanoemulsion and recommending as novel food preservative.

Origanum majorana essential oil (OmEO) encapsulated into chitosan nanoemulsion is being reported as a novel preservative of stored food items against fungi, aflatoxin B1 (AFB1) contamination and lipid peroxidation. The major component of OmEO identified through GC-MS was terpinen-4-ol (28.92%). HR-SEM, FTIR and XRD analyses confirmed successful encapsulation of OmEO into chitosan nanoemulsion (OmEO-CsNe). The results showed remarkable improvement in efficacy after nanoencapsulation, since OmEO-CsNe completely inhibited the growth and AFB1 production by Aspergillus flavus at 1.0 µL/mL, which was 2.5 and 1.5 µL/mL, respectively for OmEO. The inhibition of ergosterol followed by release of cellular ions and 260 and 280 nm absorbing materials demonstrated plasma membrane as possible antifungal target. Inhibition of methylglyoxal confirmed antiaflatoxigenic mode of action. OmEO-CsNe showed enhanced antioxidant activity (IC50 = 14.94 and 5.53 µL/mL for DPPH and ABTS, respectively) and caused in situ inhibition of lipid peroxidation and AFB1 production in maize (third most important staple crop after wheat and rice) without altering their sensory attributes and presented safety profile (LD50 = 11,889 µL/kg) when tested on mice. The findings indicate that the encapsulation considerably enhances the performance of OmEO, therefore can be recommended as a promising antifungal agent to extend the shelf-life of food items.