Showing papers by "SRM University published in 2015"

The metabolome regulates the epigenetic landscape during naive-to-primed human embryonic stem cell transition

Abstract: For nearly a century developmental biologists have recognized that cells from embryos can differ in their potential to differentiate into distinct cell types. Recently, it has been recognized that embryonic stem cells derived from both mice and humans exhibit two stable yet epigenetically distinct states of pluripotency: naive and primed. We now show that nicotinamide N-methyltransferase (NNMT) and the metabolic state regulate pluripotency in human embryonic stem cells (hESCs). Specifically, in naive hESCs, NNMT and its enzymatic product 1-methylnicotinamide are highly upregulated, and NNMT is required for low S-adenosyl methionine (SAM) levels and the H3K27me3 repressive state. NNMT consumes SAM in naive cells, making it unavailable for histone methylation that represses Wnt and activates the HIF pathway in primed hESCs. These data support the hypothesis that the metabolome regulates the epigenetic landscape of the earliest steps in human development.

Fungal biosynthesis of gold nanoparticles: mechanism and scale up

Abstract: Gold nanoparticles (AuNPs) are a widespread research tool because of their oxidation resistance, biocompatibility and stability. Chemical methods for AuNP synthesis often produce toxic residues that raise environmental concern. On the other hand, the biological synthesis of AuNPs in viable microorganisms and their cell-free extracts is an environmentally friendly and low-cost process. In general, fungi tolerate higher metal concentrations than bacteria and secrete abundant extracellular redox proteins to reduce soluble metal ions to their insoluble form and eventually to nanocrystals. Fungi harbour untapped biological diversity and may provide novel metal reductases for metal detoxification and bioreduction. A thorough understanding of the biosynthetic mechanism of AuNPs in fungi is needed to reduce the time of biosynthesis and to scale up the AuNP production process. In this review, we describe the known mechanisms for AuNP biosynthesis in viable fungi and fungal protein extracts and discuss the most suitable bioreactors for industrial AuNP biosynthesis.

Nanohydroxyapatite-reinforced chitosan composite hydrogel for bone tissue repair in vitro and in vivo

Abstract: Bone loss during trauma, surgeries, and tumor resection often results in critical-sized bone defects that need to be filled with substitutionary materials. Complications associated with conventional grafting techniques have led to the development of bioactive tissue-engineered bone scaffolds. The potential application of hydrogels as three-dimensional (3D) matrices in tissue engineering has gained attention in recent years because of the superior sensitivity, injectability, and minimal invasive properties of hydrogels. Improvements in the bioactivity and mechanical strength of hydrogels can be achieved with the addition of ceramics. Based on the features required for bone regeneration, an injectable thermosensitive hydrogel containing zinc-doped chitosan/nanohydroxyapatite/beta-glycerophosphate (Zn-CS/nHAp/β-GP) was prepared and characterized, and the effect of nHAp on the hydrogel was examined. Hydrogels (Zn-CS/β-GP, Zn-CS/nHAp/β-GP) were prepared using the sol–gel method. Characterization was carried out by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) as well as swelling, protein adsorption, and exogenous biomineralization studies. Expression of osteoblast marker genes was determined by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and western blot analyses. In vivo bone formation was studied using a rat bone defect model system. The hydrogels exhibited sol–gel transition at 37°C. The presence of nHAp in the Zn-CS/nHAp/β-GP hydrogel enhanced swelling, protein adsorption, and exogenous biomineralization. The hydrogel was found to be non-toxic to mesenchymal stem cells. The addition of nHAp to the hydrogel also enhanced osteoblast differentiation under osteogenic conditions in vitro and accelerated bone formation in vivo as seen from the depositions of apatite and collagen. The synthesized injectable hydrogel (Zn-CS/nHAp/β-GP) showed its potential toward bone formation at molecular and cellular levels in vitro and in vivo. The current findings demonstrate the importance of adding nHAp to the hydrogel, thereby accelerating potential clinical application toward bone regeneration.

Influence of electron storing, transferring and shuttling assets of reduced graphene oxide at the interfacial copper doped TiO2 p-n heterojunction for increased hydrogen production.

Abstract: Herein we report simple, low-cost and scalable preparation of reduced graphene oxide (rGO) supported surfactant-free Cu2O–TiO2 nanocomposite photocatalysts by an ultrasound assisted wet impregnation method. Unlike the conventional preparation techniques, simultaneous reduction of Cu2+ (in the precursor) to Cu+ (Cu2O), and graphene oxide (GO) to rGO is achieved by an ultrasonic method without the addition of any external reducing agent; this is ascertained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. UV-visible diffused reflectance spectroscopy (DRS) studies (Tauc plots) provide evidence for the loading of Cu2O tailoring the optical band gap of the photocatalyst from 3.21 eV to 2.87 eV. The photoreactivity of the as-prepared Cu2O–TiO2/rGO samples is determined via H2 evolution from water in the presence of glycerol as a hole (h+) scavenger under visible light irradiation. Very interestingly, the addition of rGO augments the carrier mobility at the Cu2O–TiO2 p–n heterojunction, which is evidenced by the significantly reduced luminescence intensity of the Cu2O–TiO2/rGO photocatalyst. Hence rGO astonishingly enhances the photocatalytic activity compared with pristine TiO2 nanoparticles (NPs) and Cu2O–TiO2, by factors of ∼14 and ∼7, respectively. A maximum H2 production rate of 110 968 μmol h−1 gcat−1 is obtained with a 1.0% Cu and 3.0% GO photocatalyst composition; this is significantly higher than previously reported graphene based photocatalysts. Additionally, the present H2 production rate is much higher than those of precious/noble metal (especially Pt) assisted (as co-catalysts) graphene based photocatalysts. Moreover, to the best of our knowledge, this is the highest H2 production rate (110 968 μmol h−1 gcat−1) achieved by a graphene based photocatalyst through the splitting of water under visible light irradiation.

Critical evaluation of incidence and prevalence of white spot lesions during fixed orthodontic appliance treatment: A meta-analysis.

Abstract: Objective: Development of dental caries, specifically, white spot lesions (WSLs), continues to be a well-recognized and troubling side effect of orthodontic fixed appliance therapy, despite vast improvement in preventive dental techniques and procedures. The aim of this meta-analysis is to evaluate, determine, and summarize the incidence and prevalence rates of WSLs during orthodontic treatment that have been published in the literature. Materials and Methods: According to predetermined criteria, databases were searched for appropriate studies. References of the selected articles and relevant reviews were searched for any missed publications.Results: In the 14 studies evaluated for WSLs, the incidence of new carious lesions formed during orthodontic treatment in patients was 45.8% and the prevalence of lesions in patients undergoing orthodontic treatment was 68.4%.Conclusion: The incidence and prevalence rates of WSLs in patients undergoing orthodontic treatment are quite high and significant. This widespread problem of WSL development is an alarming challenge and warrants significant attention from both patients and providers, which should result in greatly increased emphasis on effective caries prevention.

Internet addiction: Prevalence and risk factors: A cross-sectional study among college students in Bengaluru, the Silicon Valley of India

Abstract: Background: The Internet is a widely used tool known to foster addictive behavior, and Internet addiction threatens to develop into a major public health issue in the near future in a rapidly developing country like India. Objective: This cross-sectional study intends to estimate prevalence, understand patterns, and evaluate risk factors for Internet addiction among college students in the city of Bengaluru, India. Materials and Methods: Out of a total of 554 data samples from eight colleges selected through multistage cluster sampling, 515 samples were analyzed. Young's 20-item Internet Addiction Test (IAT), an inventory including demographic factors and patterns of internet use, was administered. Results: This study of college students aged 16-26 years (mean ± SD 19.2 ± 2.4 years), with marginally high female representation (56%), identified 34% [95% confidence interval (CI) 29.91-38.09%] and 8% (95%, CI 5.97-10.63%) as students with mild and moderate Internet addiction respectively. Binary logistic regression found Internet addiction to be associated with male gender [adjusted odds ratio (AOR) 1.69, 95% CI, 1.081- 2.65, P = 0.021], continuous availability online (AOR 1.724, 95% CI, 1.018-2.923, P = 0.042), using the Internet less for coursework/assignments (AOR 0.415, 95% CI, 0.263-0.655, P < 0.001), making new friendships online (AOR 1.721, 95% CI, 1.785-2.849, P = 0.034), getting into relationships online (AOR 2.283, 95% CI, 1.424-3.663, P = 0.001). Conclusion: The results highlight the vulnerability of college students to Internet addiction. The findings provide explanations on the addictive behavior of the internet users, support the inclusion of Internet Addiction in the DSM-VI, and open up new paths for further research.

Box-Behnken design based multi-response analysis and optimization of supercritical carbon dioxide extraction of bioactive flavonoid compounds from tea (Camellia sinensis L.) leaves

Abstract: The popularity of tea is increasing on the global aspect because of its role as a significant source of phenolic compounds in human diet. The objectives of this present study is to develop a supercritical carbon dioxide (SC-CO2) extraction method suitable for extraction of phenolic compounds such as total phenolics, flavonoids and tannin from tea leaves at various extraction conditions such as extraction pressure (100–200 bar), temperature (40–60 °C) and co-solvent (ethanol) flow rate (1–3 g/min). Furthermore, the total antioxidant activity of the SC-CO2 tea leaves extracts was assessed using ABTS+ (2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)) method. Response surface methodology (RSM) combined with Box-Behnken design was used to investigate and optimize the process variables. The results showed that, extraction pressure and co-solvent flow rate have significant effect on the responses. From the experimental data, second order polynomial mathematical models were developed for each response with high coefficient of determination value (R2 > 0.95). An optimization study using Derringer’s desired function methodology was performed and the optimal conditions based on both individual and combinations of all independent variables (extraction pressure of 188 bar, temperature of 50 °C and co-solvent flow rate of 2.94 g/min) were determined with maximum total phenolic content of 131.24 mg GAE/100 ml, total flavonoid content of 194.60 mg QE/100 ml, total tannin content of 49.99 mg TAE/100 ml and totalantioxidant activity of 262.23 μMol TEAC/100 ml of extracts respectively with a overall desirability value of 0.983, which was confirmed through validation experiments.

Novel CuO/chitosan nanocomposite thin film: facile hand-picking recoverable, efficient and reusable heterogeneous photocatalyst

Abstract: The present work demonstrates a new simple hand-picking technique for the 100% recovery of a photocatalyst. CuO nanospheres were synthesized by a simple wet chemical method and were subsequently embedded into the biopolymer matrix (chitosan) under mild conditions by the solution cast method and its photocatalytic application towards the degradation of organic pollutants was measured for the first time. The crystal structure, optical properties, surface and bulk morphology were discussed in detail. ICP-OES analysis showed 3.025% copper embedded in the chitosan (CS) matrix. Efficiency of the CuO/chitosan was evaluated against the degradation of rhodamine B dye as a probe. The combination of CuO nanospheres with chitosan leads to the higher efficiency of up to 99% degradation of the dye with 60 minutes of irradiation. This may be attributed to many features such as the slow electron hole pair recombination rate of nanosized CuO in the biopolymer matrix, the large surface area of the CuO and the high adsorption efficiency of the chitosan. The major advantage of this present protocol is that it is not only restricted to azo type dyes but can also be adopted for different kinds of organic pollutants. For all the types of organic contaminants tested, the CuO/chitosan nanocomposite thin film photocatalyst showed excellent activity. The facile hand-picking recovery and recyclability of this novel thin film likely opens up a new straightforward strategy in the effective photocatalytic degradation of organic contaminants.

Academic stress and depression among adolescents: a cross-sectional study.

Abstract: To examine the relationship between academic stress and depression among adolescents. A cross-sectional study was conducted at higher secondary schools in Tamil Nadu. 1120 adolescents were included in the study after screening by MINI-kid tool. Modified Educatonal Stress Scale for Adolescents was administered to all children. Adolescents who had academic stress were at 2.4 times (95% CI=0.9-2.4) (P<0.001) higher risk of depression than adolescents without academic stress. Adolescents with severe academic stress need to be identified early as interventions to reduce academic stress is likely to affect the occurrence and severity of depression.