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  1. Parasuraman S, Elamvazuthi I, Kanagaraj G, Natarajan E, Pugazhenthi A
    Materials (Basel), 2021 Mar 31;14(7).
    PMID: 33807476 DOI: 10.3390/ma14071726
    Reinforced aluminum composites are the basic class of materials for aviation and transport industries. The machinability of these composites is still an issue due to the presence of hard fillers. The current research is aimed to investigate the drilling topographies of AA7075/TiB2 composites. The samples were prepared with 0, 3, 6, 9 and 12 wt.% of fillers and experiments were conducted by varying the cutting speed, feed, depth of cut and tool nose radius. The machining forces and surface topographies, the structure of the cutting tool and chip patterns were examined. The maximum cutting force was recorded upon increase in cutting speed because of thermal softening, loss of strength discontinuity and reduction of the built-up-edge. The increased plastic deformation with higher cutting speed resulted in the excess metal chip. In addition, the increase in cutting speed improved the surface roughness due to decrease in material movement. The cutting force was decreased upon high loading of TiB2 due to the deterioration of chips caused by fillers. Further introduction of TiB2 particles above 12 wt.% weakened the composite; however, due to the impact of the microcutting action of the fillers, the surface roughness was improved.
  2. Lazar PJL, Sengottuvelu R, Natarajan E
    Materials (Basel), 2018 Nov 05;11(11).
    PMID: 30400592 DOI: 10.3390/ma11112186
    The principal objective of this research work was to investigate the results of impregnating epoxy matrix-glass fibre composite laminates with nanosilica as secondary reinforcement. 0.5, 0.75, 1 and 3 wt% nanosilica was used and thereafter properties of composites were assessed through tensile, three point bending, quasi static indentation tests and dynamic mechanical analysis. Scanning electron microscope examinations were done on fracture surfaces and failure modes were analyzed. The internal failures of the composite due to quasi-static indentation were evaluated through C-Scan. Among samples of different weight fractions, 0.75 wt% nanosilica reinforced composite laminates exhibited substantial increase of 42% in tensile strength and 39.46% in flexural strength. The reduction in glass transition temperature (Tg), increase in storage modulus (E'), loss modulus (E″) and damping factor (tan δ) were also observed. Quasi-static indentation assessments revealed that energy absorption property was enhanced significantly by 53.97%. Hence nanosilica up to 0.75 wt% can be used as a potential candidate for secondary reinforcement in epoxy composite laminates.
  3. Kosalishkwaran G, Parasuraman S, Singh DKJ, Natarajan E, Elamvazuthi I, George J
    Med Biol Eng Comput, 2019 Oct;57(10):2305-2318.
    PMID: 31444622 DOI: 10.1007/s11517-019-02026-6
    Degenerative disc disease (DDD) is a common condition in elderly population that can be painful and can significantly affect individual's quality of life. Diagnosis of DDD allows prompt corrective actions but it is challenging due to the absence of any symptoms at early stages. In studying disc degeneration, measurement of the range of motion (RoM) and loads acting on the spine are crucial factors. However, direct measurement of RoM involves increased instrumentation and risk. In this paper, an innovative method is proposed for calculating RoM, emphasizing repeatability and reliability by considering the posterior thickness of the spine. This is achieved by offsetting the position of markers in relation to the actual vertebral loci. Three geometrically identical finite element models of L3-L4 are developed from a CT scan with different types of elements, and thereafter, mesh element-related metrics are provided for the assessment of the quality of models. The model with the best mesh quality is used for further analysis, where RoM are within ranges as reported in literature and in vivo experiment results. Various kinds of stresses acting on individual components including facet joints are analysed for normal and abnormal loading conditions. The results showed that the stresses in abnormal load conditions for all components including cortical (76.67 MPa), cancellous (69.18 MPa), annulus (6.30 MPa) and nucleus (0.343 MPa) are significantly greater as compared to normal loads (49.96 MPa, 44.2 MPa, 4.28 MPa and 0.23 MPa respectively). However, stress levels for both conditions are within safe limits (167-215 MPa for cortical, 46 MPa for the annulus and 3 MPa for facets). The results obtained could be used as a baseline motion and stresses of healthy subjects based on their respective lifestyles, which could benefit clinicians to suggest corrective actions for those affected by DDD.
  4. Lal LPJ, Ramesh S, Parasuraman S, Natarajan E, Elamvazuthi I
    Materials (Basel), 2019 Sep 20;12(19).
    PMID: 31547117 DOI: 10.3390/ma12193057
    Nanosilica particles were utilized as secondary reinforcement to enhance the strength of the epoxy resin matrix. Thin glass fibre reinforced polymer (GFRP) composite laminates of 3 ± 0.25 mm were developed with E-Glass mats of 610 GSM and LY556 epoxy resin. Nanosilica fillers were mixed with epoxy resin in the order of 0.25, 0.5, 0.75 and 1 wt% through mechanical stirring followed by an ultrasonication method. Thereafter, the damage was induced on toughened laminates through low-velocity drop weight impact tests and the induced damage was assessed through an image analysis tool. The residual compression strength of the impacted laminates was assessed through compression after impact (CAI) experiments. Laminates with nanosilica as secondary reinforcement exhibited enhanced compression strength, stiffness, and damage suppression. Results of Fourier-transform infrared spectroscopy revealed that physical toughening mechanisms enhanced the strength of the nanoparticle-reinforced composite. Failure analysis of the damaged area through scanning electron microscopy (SEM) evidenced the presence of key toughening mechanisms like damage containment through micro-cracks, enhanced fiber-matrix bonding, and load transfer.
  5. Lu B, Natarajan E, Balaji Raghavendran HR, Markandan UD
    Technol Cancer Res Treat, 2023;22:15330338221145246.
    PMID: 36601658 DOI: 10.1177/15330338221145246
    Breast cancer is the most common malignancy and the second most common cause of cancer-related mortality in women. Triple-negative breast cancers do not express estrogen receptors, progesterone receptors, or human epidermal growth factor receptor 2 and have a higher recurrence rate, greater metastatic potential, and lower overall survival rate than those of other breast cancers. Treatment of triple-negative breast cancer is challenging; molecular-targeted therapies are largely ineffective and there is no standard treatment. In this review, we evaluate current attempts to classify triple-negative breast cancers based on their molecular features. We also describe promising treatment methods with different advantages and discuss genetic biomarkers and other prediction tools. Accurate molecular classification of triple-negative breast cancers is critical for patient risk categorization, treatment decisions, and surveillance. This review offers new ideas for more effective treatment of triple-negative breast cancer and identifies novel targets for drug development.
  6. Baig S, Azizan AHS, Raghavendran HRB, Natarajan E, Naveen S, Murali MR, et al.
    Stem Cells Int, 2019;2019:5142518.
    PMID: 30956670 DOI: 10.1155/2019/5142518
    We have determined the protective effects of Thymus serpyllum (TS) extract and nanoparticle-loaded TS on hydrogen peroxide-induced cell death of mesenchymal stromal cells (MSCs) in vitro. Gas chromatography-mass spectroscopy confirmed the spectrum of active components in the extract. Out of the three different extracts, the hexane extract showed significant free radical scavenging activity. Treatment of MSCs with H2O2 (hydrogen peroxide) significantly increased intracellular cell death; however, pretreatment with TS extract and nanoparticle-loaded TS (200 μg/ml) suppressed H2O2-induced elevation of Cyt-c and MMP13 and increased the survival rates of MSCs. H2O2-induced (0.1 mM) changes in cytokines were attenuated in the extract and nanoparticles by pretreatment and cotreatment at two time points (p < 0.05). H2O2 increased cell apoptosis. In contrast, treatment with nanoparticle-loaded TS suppressed the percentage of apoptosis considerably (p < 0.05). Therefore, TS may be considered as a potential candidate for enhancing the effectiveness of MSC transplantation in cell therapy.
  7. Mohan S, Raghavendran HB, Karunanithi P, Murali MR, Naveen SV, Talebian S, et al.
    ACS Appl Mater Interfaces, 2017 Mar 22;9(11):9291-9303.
    PMID: 28266827 DOI: 10.1021/acsami.6b13422
    Tissue engineering aims to generate or facilitate regrowth or healing of damaged tissues by applying a combination of biomaterials, cells, and bioactive signaling molecules. In this regard, growth factors clearly play important roles in regulating cellular fate. However, uncontrolled release of growth factors has been demonstrated to produce severe side effects on the surrounding tissues. In this study, poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) incorporated three-dimensional (3D) CORAGRAF scaffolds were engineered to achieve controlled release of platelet-derived growth factor-BB (PDGF-BB) for the differentiation of stem cells within the 3D polymer network. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and microtomography were applied to characterize the fabricated scaffolds. In vitro study revealed that the CORAGRAF-PLGA-PDGF-BB scaffold system enhanced the release of PDGF-BB for the regulation of cell behavior. Stromal cell attachment, viability, release of osteogenic differentiation markers such as osteocalcin, and upregulation of osteogenic gene expression exhibited positive response. Overall, the developed scaffold system was noted to support rapid cell expansion and differentiation of stromal cells into osteogenic cells in vitro for bone tissue engineering applications.
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