Fabrication and electrochemical characterization of highly efficient hierarchically assembled hybrid two-dimensional nanointerfaces for electrochemical biosensing and bioelectronics

Abstract : Two dimensional (2D) materials have provided a new era to biosensors research. Biosensors are functional biodevices which include the integration of biology with electronics. The integration of 2D materials with other nanomaterials has transformed the understanding of the biological and electronics world and has paved a way for the design and fabrication of novel 2D nanointerfaces. The use of 2D nanointerfaces has given great success to biosensors and bioelectronics field which ultimately impacts on biomedical diagnosis and sensing applications. The superior properties of 2D materials such as large surface area, ease of hybridization, good biocompatibility, and high electron transfer properties make them ideal interface materials for the design and fabrication of bioelectronic devices including biosensors. The thesis focused on the fabrication of 2D nanointerfaces by combining two 2D hybrid materials and then nanostructuring with metal nanoparticles for better electron transfer within the interface which is followed by immobilization of enzyme as a bio-recognition element for biosensing purposes. The conjugation of the 2D hybrid nanointerface materials was achieved through the self-assembly technique. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used in the study for characterization of the 2D hybrid nanointerface structures and chronoamperometry studies were employed to investigate the electrobiocatalytic properties of the 2D hybrid nanointerfaces structures. Structural characterization was done by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques for morphological details of 2D hybrid nanointerfaces structures. The fabrication of bioelectrodes was achieved by using the conjugated 2D hybrid nanointerface materials. ix There are three different segments in this research study. All of these different segments involved the use of 2D materials for bioelectronics purposes. The first phase involved the fabrication of smart hierarchically self-assembled 2D electrobiocatalytic interface system based on the combination of gold nanoparticles (AuNPs) doped graphene oxide (GO)-molybdenum disulfide (MoS2) layered nanohybrid, conjugated with poly (N-isopropylacrylamide, PNIPAAm) resulting in GO/AuNPs/MoS2/PNIPAAm interface. The introduction of PNIPAAm improved the stability of the self-assembled GO/AuNPs/MoS2 interface structure. Horseradish peroxidase (HRP) was subsequently immobilized on the GO/AuNPs/MoS2/PNIPAAm interface through electrostatic interactions giving GO/AuNPs/MoS2/PNIPAAm/Peroxidase electrobiocatalytic interface system as a platform for electrobiocatalysis reactions for biosensing applications. Morphological characterization of GO/AuNPs/MoS2/PNIPAAm indicates that this 2D nanointerface structure has a wide surface area for enzyme immobilization due to their flake-like structure. CV showed diffusion-controlled electron transfer properties at the interface. The electrobiocatalytic activity of the nanohybrid interface structure was studied using hydrogen peroxide (H2O2) as a model analyte. The fabricated bioelectrode exhibits a wide linear response to the detection of H2O2 from 1.57 to 11.33 mM, with a detection limit of 3.34 mM (S/N=3) and a capacitance of 8.6 F/cm2. The second phase of the study involved the fabrication of hybrid dual 2D-nanohybrid structure through self-assembly combination AuNPs with hybrid 2D materials consisting of boron nitride (BN) and tungsten disulphide (WS2) as a nanointerface system for electrochemical biosensing. HRP was immobilized on the hybrid dual 2Dnanoparticle systems to form a biointerface. Structural characterization showed high crystallinity in the fabricated structure, while morphological characterization confirmed x the high surface to volume area of the hybrid material and the presence of welldispersed AuNPs. Electrochemical characterization also confirmed that the fabricated HRP/BN/WS2/AuNPs/GC bioelectrode exhibited excellent electron transfer properties at the interface. The electrobiocatalytic activity of the nanohybrid interface structure was studied using H2O2 as a model analyte. The fabricated bioelectrode exhibited a wide linear range from 0.15 mM to 15.01 mM towards detection of H2O2 with a limit of detection of 3.0 mM (S/N = 3) and a sensitivity of 19.16 μA/mM/cm2. Theoretical studies of the BN/Au/WS2(001) nanohybrid structure was carried out using density functional theory (DFT) calculation for confirming the charge transport mobility and conductivity of the fabricated material. DFT calculations combined with the experimental studies showed that the self-assembled combination of the BN/Au/WS2(001) nanocomposite enhances the performance of the fabricated biosensor due to an introduced new electronic state emanating from the N 2p orbital. The third phase of the study involved the synthesis of acetylene sourced graphene (Gr) by chemical vapour deposition (CVD) method. Self-assembly method was used to prepare the 2D nanohybrid interfaces, which consist of Gr, WS2, AuNPs and HRP for fabricating electrochemical biosensor for detection of H2O2. The XRD results revealed that Gr/WS2/AuNPs nanohybrid structure has good crystalline nature. CV and electrochemical impedance spectroscopy results showed that due to the incorporation of AuNPs, the redox properties of Gr/WS2/AuNPs/HRP conjugate 2D hybrid structure improved in comparison to Gr/WS2/HRP. The same trend was observed in the chronoamperometric results. The Gr/WS2/AuNPs/HRP/GCE modified bioelectrode exhibited a good electrobiocatalytic performance towards the detection of H2O2 over a relatively wider linear range (0.40 mM to 23 mM), with a higher xi sensitivity (11.07 μA/mM/cm2) than that of Gr/WS2/HRP/GCE modified bioelectrode (9.23 μA/mM/cm2). The results have shown that electrobiocatalytic reactions can be controlled by modifying the nanohybrid interfaces.D.Phil. (Chemistr

Evaluation of thyroid dysfunction in patients with menstrual disorders of reproductive age group: a prospective cross-sectional study

Background: Thyroid disorders specifically the hypothyroidism has been associated with menstrual disturbances in women of reproductive age group. The objective of this study was to estimate the prevalence of thyroid dysfunction and its correlation with menstrual disorders in women of reproductive age group.Methods: A hospital based prospective analytical study was carried out in the department of Obstetrics and Gynaecology of Nalanda Medical College and Hospital, Patna from March 2017 to March 2018. 56 women of reproductive age group between 18 to 45 years presenting with menstrual disorders (like menorrhagia, oligo/hypomenorrhea, polymenorrhea, metrorrhagia, and amenorrhea) were recruited in this study. Thyroid function test was done in all patients. Statistical analysis done.Results: Maximum number of patients were seen in the age group of 31-40 years. Most common menstrual complain was menorrhagia (46.42%) followed by hypo/oligomenorrhoea (17.86%). In patients with menstrual disorders, 41.07 % had thyroid disorders in which subclinical hypothyroidism was prevalent in 17.86%, overt hypothyroidism in 12.5%, and overt hyperthyroidism in 5.35% of the women. Menorrhagia was the commonest menstrual disorder (52.94%) seen in hypothyroid patients followed by polymenorrhoea. A high degree positive correlation was observed between thyroid dysfunction and menstrual disorder (Pearson correlation coefficient, r=0.93).Conclusions: Our study concluded that thyroid dysfunction should be considered as an important etiological factor for menstrual irregularity. Thus, thyroid function tests should be performed in all patients with menstrual irregularities to avoid unnecessary interventions like curettage and hysterectomy

Is Screening of TORCH Worthwhile in Women with Bad Obstetric History: An Observation from Eastern Nepal

This pilot case-control study at a tertiary-care hospital over a four-month period was aimed at evaluating the possible usefulness of screening of TORCH (Toxoplasma gondii, rubella virus, cytomegalovirus, and Herpes simplex virus) in females with bad obstetric history. The study included 12 women with bad obstetric history and a similar number of matched controls with previous normal pregnancies. A serological evaluation of TORCH infections was carried out by detecting IgG and IgM antibodies against these infections by ELISA test-kit. Statistical analysis was not done to compare the results relating to the two groups due to a small number of cases and controls included in the study. Ten (83.3%) of the 12 cases with bad obstetric history and two (16.7%) of the 12 healthy controls were serologically positive at least for one of the TORCH agents. The seropositivity rate in women with bad obstetric history was quite high compared to that in the normal healthy controls. The results suggest that a previous history of pregnancy wastage and the serological evaluation of TORCH infections during current pregnancy must be considered while managing cases with bad obstetric history

Fetal colon diameter as a tool for estimating gestational age in advanced pregnancy in north Indian population: a pilot study

Background: Conventional Ultrasound dating is not very accurate after 34 weeks of gestation and has standard deviation of about 2 weeks. The aim of the study was to verify whether fetal colon diameter can be used as a tool for estimating gestational age (GA) of fetuses between 32 to 40 weeks.Methods: 100 healthy pregnant women aged 20-35 years were recruited. Fetal bi-parietal diameter, head circumference, abdominal circumference, and femoral lengths were assessed by ultrasound. In addition descending colon diameter was assessed at the level of colonic haustra. The correlation between GA and colon thickness was assessed by the Pearson correlation test.Results: Significant correlation between fetal colon diameter and maternal gestational age was observed (r=0.582). Correlation between gestational age and femur length (r = 0.725) was found to be higher than that between gestational age and colon diameter (r = 0.528) suggesting that femur length is a better parameter than colon diameter for gestational age estimation. The regression equation for gestational age as a function of colon diameter was derived as GA = 28.614 + 0.629 × CD. The diagnostic accuracy of CD of ≥ 12mm in predicting term pregnancy was 75% with a high negative predictive value of 88.9% and positive predictive value of 58.7%.Conclusions: The present study suggested that colon diameter can be used for predicting term pregnancy. Further studies are required to validate this novel marker of maturity amongst Indian population

Vulvar lichen sclerosus: recent advances in understanding and management

Vulvar lichen sclerosus (VLS) is a chronic inflammatory disorder, which affects women of all ages. It is one of the most common pathologies presenting to vulvar clinics. However, uncertainty continues to exist about its etiopathogenesis, diagnosis and treatment. Studies suggest a multifactorial origin as far as etiology is concerned, including a genetic, autoimmune, hormonal and local infectious background. There is often a delay in diagnosis of VLS due to its asymptomatic nature and lack of awareness in patients as well as physicians. Embarrassment of patients due to private nature of the disease and failure to examine the genital skin properly are the other reasons for delay in diagnosis. Conventionally, treatment includes topical corticosteroids as a first-line therapy with alternative options such as topical calcineurin inhibitors, topical and systemic retinoids, other steroid creams, various destructive techniques and surgical removal of affected tissues. New therapeutic approaches are coming into effect in gynecological practice due to potential risks of the above-mentioned methods. Stem cell and platelet-rich plasma therapy, energy-based modalities such as the fractional CO2 laser, photo dynamic therapy, and high intensity focused ultrasound, and new topical medicines, are some of the new options applied to improve the efficacy of treatment avoiding the side effects of conventional methods. Refinement of surgical techniques for restoring vulvar anatomy is leading to improved patient outcomes. This review summarizes current perspectives on the etiopathogenesis, diagnosis and treatment for vulvar lichen sclerosus.

Immune Dysfunction during Enteric Protozoal Infection: The Current Trends

Enteric protozoa usually cause severe morbidity and mortality in humans. Protozoal infections contribute to the high burden of infectious diseases. Despite recent advances in the epidemiology, diagnostic tool, molecular biology, and treatment of protozoan illnesses, gaps in knowledge still exist; hence, protozoal infections require further research. We are describing here some important enteric protozoal infections along with the immune dysfunction produced by them. Genus- 1. Entamoeba; 2. Giardia; 3. Cryptosporidium; 4. Cyclospora; 5. Cystoisospora; 6. Dientamoeba; 7. Blastocystis; 8. Balantidium

Metabolic Changes during Differentiation in Callus Cultures of Stevia rebaudiana (Bertoni)

Stevia rebaudiana (Bertoni) is an economically important medicinal plants act as an option for artificial sweetening agents. The plant regeneration protocol under in vitro conditions has been developed for this natural sweetener herb. Callus was efficiently induced when leaf segments were cultured on MS medium supplemented with 1.0 mg/l 2, 4-D + 1.0 mg/l Kinetin. The above callus was sub cultured on MS medium + 0.5 mg/l BAP + 0.3 mg/l NAA for root differentiation and on MS medium + 0.5 mg/l BAP + 0.1 mg/l NAA for shoot differentiation. Biochemical changes occurring during the callus differentiation were adopted to quantify the metabolites. Metabolites like starch, total soluble sugars and total phenols decreased while total soluble proteins increased in callus culture during the process of root and shoot differentiation.Key words: Callus, differentiation, in vitro, metabolites, Stevia rebaudianaAbbreviations:  BAP Benzyl amino purine; 2,4-D 2,4-Dichlorophenoxyacetic acid; MS Murashige and Skoog (1962) basal medium; NAA α-naphthalene acetic acid; IBA Indole-3-butyric acid; IAA Indole acetic acidNarender Singh et al. Metabolic Changes during Differentiation in Callus Cultures of Stevia rebaudiana (Bertoni). J Phytol 3/3 (2011) 63-67

Comparative study of intravenous hydralazine and labetalol in severe hypertensive disorders of pregnancy

Background: Hypertensive disorders of pregnancy are among the most common medical complications of pregnancy and major cause of maternal, fetal and neonatal morbidity and mortality. The purpose of this study was to compare the efficacy and safety of intravenous hydralazine and labetalol for management of severe hypertensive disorders of pregnancy.Methods: This prospective study was conducted among 100 women admitted with SBP ≥ 160 or DBP ≥ 110 mmHg or both. Patients were divided into 2 groups randomly: labetalol and hydralazine group.Results: Majority of patients (38%) were in the age group of 21-25 years and primigravida (52%). There was more significant decrease in the systolic, diastolic and mean arterial blood pressure at the end of 15 and 30 minutes in labetalol group. Labetalol required fewer doses as compared to hydralazine to achieve the target blood pressure (average 1.95 versus 3.1). Total numbers of term deliveries were 19 (38%) in hydralazine group and 16 (32%) in labetalol group. Pre-term deliveries in hydralazine and labetalol group were 14 (28%) and 15 (30%) respectively. Headache was significantly more common in hydralazine treated patients than labetalol group.Conclusions: Both hydralazine and labetalol were effective and well-tolerated in the treatment of severe hypertensive disorders of pregnancy. Labetalol may be preferred because it was more effective in lowering the systolic blood pressure, diastolic blood pressure and mean arterial pressure to achieve target levels with less number of doses

Assessment of serum lipid profile in early pregnancy and its relation with pre eclampsia: a prospective study

Background: Pathophysiology of pre eclampsia and atherosclerosis seems to be similar as a hyperlipidemic state, due to hormonal changes in pregnancy. We tried to assess the relationship between maternal plasma lipid concentration and risk of developing pre eclampsia.Methods: This is a prospective cohort study, for a period of one year from August 2009 to August 2010. Total no of subjects (N=270) were divided into two groups: Control group:  who remained normotensive during study and Study group: who developed pre-eclampsia.Results: The mean level of cholesterol in study group was (226.74±39.77 mg/dl) significantly higher as compared to control group (164±22.48 mg/dl). That was statistically significant (p=0.001). Mean levels of cholesterol in mild PET group was 216±28.90mg/dl and in severe PET group was 252.3±50.63 mg/dl respectively, that was also significantly higher as compared to control group (p=0.001). In our study mean levels of Triglyceride was 153.95±23.52 mg/dl in control group and 205.25±42.48 mg/dl in study group. There were statistically significant difference between the groups (p=0.001). In mild PET mean value of Triglyceride was 198.99±36.12 mg/dl and in severe PET it was 220.35± 53.13mg/dl. It was seen that both the study group had significantly higher mean value as compared to control group (p=0.001).Conclusions: In present study we have observed that maternal dyslipidemia in early second trimester is associated with increased risk of developing pre eclampsia. So dyslipidemia in early second trimester is a very good predictor of pre eclampsia

Cellular homeostasis, implantation window and unexplained infertility: role of phosphatase and tensin homolog deleted on chromosome 10

Background: Balance between endometrial cell proliferation and apoptosis is crucial for successful embryo implantation. PTEN (phosphatase and tensin homolog deleted on chromosome 10), a pro-apoptotic factor, is proposed to be one of the signaling proteins through which estrogen and progesterone act to affect cellular homeostasis. Although reports in literature have suggested role of PTEN in regulating endometrial cell proliferation and apoptosis during window of implantation, its involvement in women with unexplained infertility is not clear. In the present study, we examined expression, cellular distribution and activation status of PTEN, cell proliferation, and apoptosis in midsecretory endometrium from women with unexplained infertility as compared to fertile controls.Methods: Endometrial biopsies from infertile (n=11) and fertile women (n=22) were used for immunohistochemical evaluation of PTEN, phospho-PTEN and Ki67. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay was performed for detection of apoptotic cells.Results: Biopsies from infertile women as compared to fertile controls demonstrated statistically significant: i) decrease in nuclear PTEN (P < 0.001), increase in nuclear phospho-PTEN (P < 0.05), increase in nuclear and cytoplasmic phospho-PTEN/PTEN ratio (P < 0.001 and P < 0.05 respectively) in endometrial stroma, ii) increase in cytoplasmic phospho-PTEN (P < 0.001) and phospho-PTEN/PTEN ratio (P < 0.05) in glandular epithelium (GE), iii) increase in Ki67 labeling in GE (P < 0.01) and stroma (P < 0.05) and, iv) decrease in (P < 0.001) apoptosis.Conclusions: Altered PTEN expression and associated modulation in cellular homeostasis during the implantation window might contribute to mechanism underlying unexplained infertility