Washing-Free Displacement Immunosensor for Cortisol in Human Serum Containing Numerous Interfering Species

Nandhakumar, Ponnusamy,Haque, Al-Monsur Jiaul,Lee, Nam-Sihk,Yoon, Young Ho,Yang, Haesik American Chemical Society 2018 ANALYTICAL CHEMISTRY - Vol.90 No.18

<P>Simple and sensitive competitive immunosensors for small molecules are difficult to obtain, especially in serum containing numerous interfering species (ISs) with different concentrations. Herein, we report a washing-free and sensitive (competitive) displacement immunosensor for cortisol in human serum, based on electron mediation of Os(bpy)<SUB>2</SUB>Cl<SUB>2</SUB> between an electrode and a redox label [oxygen-insensitive diaphorase (DI)] (i.e., electrochemical-enzymatic redox cycling). The anticortisol IgG-DI conjugate bound to a cortisol-immobilized electrode is displaced by competitive binding of cortisol in serum and diffuses away from the electrode during incubation; therefore, the concentration of the displaced conjugate near the electrode becomes very low, even without washing. Electrochemically interfering ascorbic acid is converted to a redox-inactive species by ascorbate oxidase during incubation. The remaining bound conjugate mainly contributes to electrochemical currents. Compared with ferrocene methanol, Fe(CN)<SUB>6</SUB><SUP>4-</SUP>, and Ru(NH<SUB>3</SUB>)<SUB>6</SUB><SUP>3+</SUP>, the electrochemical and redox cycling behaviors of Os(bpy)<SUB>2</SUB>Cl<SUB>2</SUB> are influenced significantly less by ISs in serum. Comparative studies reveal that washing-free displacement assay shows better cortisol-induced signal change than three other assays. The surface concentration of cortisol immobilized on the electrode is optimized, because the electrochemical signal is highly dependent on the surface concentration. When the washing-free displacement immunosensor is applied for the detection of cortisol in artificial serum, cortisol is measured with a detection limit of ∼30 pM within 12 min. The cortisol concentrations measured in clinical serum samples agree well with those obtained using a commercial instrument. The new immunosensor is highly promising for the simple, sensitive, and rapid point-of-care detection of small molecules.</P> [FIG OMISSION]</BR>

Stereoselective Recognition of Amino Alcohols and Amino Acids by Carbonylurea- and Carbonyguanidinium-based Imine Receptors

Nandhakumar, Raju,Ahn, Yun-Soo,Yoon, Hoe-Jin,Kim, Kwan-Mook Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

New receptors 1-3 that bind stereoselectively amino alcohols and convert chirality of amino acidsvia imine bond formation were synthesized. The receptors have uryl (1), thiouryl (2) and guanidinium (3) groups all with additional phenylcarbonyl motifs, which are effective hydrogen bonding donors and play a key role in the stereoselective recognitions. The stereoselectivities were measured from the integration of $^1HNMR$ peaks. Compound 1 and 2 showed the stereoselectivities for the imine formation with amino alcohols ($K_R/K_S$) in the range of 2${\sim}$4, and compound 3 in the range of 4${\sim}$8. Chirality conversion efficienciesof 1-3 for amino acids, i.e. D/L ratio at equilibrium, are in the range of 1.5${\sim}$5.6, showing a little higher efficiency with 3. The additional phenylcarbonyl motifs in 1-3 were revealed not to contribute to significant enhancement of the selectivities.

A Honey-Hive based Efficient Data Aggregation in Wireless Sensor Networks

Nandhakumar Ramachandran,Varalakshmi Perumal 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

The advent of Wireless Sensor Networks (WSN) has led to their use in numerous applications. Sensors are autonomous in nature and are constrained by limited resources. Designing an autonomous topology with criteria for economic and energy conservation is considered a major goal in WSN. The proposed honey-hive clustering consumes minimum energy and resources with minimal transmission delay compared to the existing approaches. The honey-hive approach consists of two phases. The first phase is an Intra-Cluster Min-Max Discrepancy (ICMMD) analysis, which is based on the local honey-hive data gathering technique and the second phase is Inter-Cluster Frequency Matching (ICFM), which is based on the global optimal data aggregation. The proposed data aggregation mechanism increases the optimal connectivity range of the sensor node to a considerable degree for inter-cluster and intra-cluster coverage with an improved optimal energy conservation.

Nitrosoreductase-Like Nanocatalyst for Ultrasensitive and Stable Biosensing

Nandhakumar, Ponnusamy,Kim, Byeongyoon,Lee, Nam-Sihk,Yoon, Young Ho,Lee, Kwangyeol,Yang, Haesik American Chemical Society 2018 ANALYTICAL CHEMISTRY - Vol.90 No.1

<P>Enzyme-like nanocatalytic reactions developed for high signal amplification in biosensors are of limited use because of their low reaction rates and/or unwanted side reactions in aqueous electrolyte solutions containing dissolved O<SUB>2</SUB>. Herein, we report a nitrosoreductase-like catalytic reaction, employing 4-nitroso-1-naphthol, Pd nanoparticles, and H<SUB>3</SUB>N–BH<SUB>3</SUB>, which affords a high reaction rate and minimal side reactions, enabling its use in ultrasensitive electrochemical biosensors. 4-Nitroso-1-naphthol was chosen after five hydroxy-nitro(so)arene compounds were compared in terms of high signal and low background levels. Importantly, the nanocatalytic reaction occurs without the self-hydrolysis and induction period observed in the nanocatalytic reduction of nitroarenes by NaBH<SUB>4</SUB>. The high signal level results from (i) fast nanocatalytic 4-nitroso-1-naphthol reduction, (ii) fast electrochemical redox cycling, and (iii) the low influence of dissolved O<SUB>2</SUB>. The low background level results from (i) slow direct reaction between 4-nitroso-1-naphthol and H<SUB>3</SUB>N–BH<SUB>3</SUB>, (ii) slow electrode-mediated reaction between 4-nitroso-1-naphthol and H<SUB>3</SUB>N–BH<SUB>3</SUB>, and (iii) slow electrooxidation of H<SUB>3</SUB>N–BH<SUB>3</SUB> at electrode. When applied to the detection of parathyroid hormone, the detection limit of the newly developed biosensor was ∼0.3 pg/mL. The nitrosoreductase-like nanocatalytic reaction is highly promising for ultrasensitive and stable biosensing.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2018/ancham.2018.90.issue-1/acs.analchem.7b03364/production/images/medium/ac-2017-03364x_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac7b03364'>ACS Electronic Supporting Info</A></P>

In vitro Antioxidant Activities of Methanol and Aqueous Extract of Annona squamosa (L.) Fruit Pulp

Elumalai Nandhakumar,Parameswaran Indumathi 사단법인약침학회 2013 Journal of Acupuncture & Meridian Studies Vol.6 No.3

The present study evaluated the antioxidant activity of the fruit of Annona squamosa by means of in vitro studies involving two different solvent extracts: methanol and aqueous. The antioxidant properties of the extract were determined by scavenging 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH), lipid peroxidation (LPO), nitric oxide (NO), superoxide anion (O₂-), hydroxyl radical (OHㆍ), reducing power and total antioxidant. The results showed that, compared to aqueous extract, a methanolic fruit extract of A squamosa has a higher percentage of inhibition of DPPH radical scavenging activity (97.99%), LPO (94.15%), NO scavenging activity (70.96%), O₂- scavenging activity and OHㆍ scavenging activity (78.68% and 85.25%, respectively), total antioxidant activity (206 µg α-tocopherol/g) and reducing power (56.0 µg of ascorbic acid/g). The results obtained in the in vitro models clearly suggest that methanol extract has higher antioxidant activity than the aqueous extract due to a higher presence of phenolic and flavonodal constituents in the methanol extract.

Stereoselective Recognition of Amino Alcohols and Amino Acids by Carbonylurea- and Carbonyguanidinium-based Imine Receptors

Raju Nandhakumar,Yun Soo Ahn,Hoe-Jin Yoon,김관묵 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

New receptors 1-3 that bind stereoselectively amino alcohols and convert chirality of amino acidsvia imine bond formation were synthesized. The receptors have uryl (1), thiouryl (2) and guanidinium (3) groups all with additional phenylcarbonyl motifs, which are effective hydrogen bonding donors and play a key role in the stereoselective recognitions. The stereoselectivities were measured from the integration of 1H NMR peaks. Compound 1 and 2 showed the stereoselectivities for the imine formation with amino alcohols (KR/KS) in the range of 2 ~ 4, and compound 3 in the range of 4 ~ 8. Chirality conversion efficienciesof 1-3 for amino acids, i.e. D/L ratio at equilibrium, are in the range of 1.5 ~ 5.6, showing a little higher efficiency with 3. The additional phenylcarbonyl motifs in 1-3 were revealed not to contribute to significant enhancement of the selectivities.

Acute and Sub-acute Toxicity Studies using Shemamruthaa, a Modified Indigenous Siddha Preparation, in Sprague-Dawley Rats

Elumalai Nandhakumar,Ayyakkannu Purushothaman,Panchanadham Sachdanandam 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.1

Shemamruthaa (SM), an indigenous herbalformulation (Hibiscus rosa sinensis flowers, Phyllanthusemblica, and pure honey) in a definite ratio was analyzedusing acute and sub-acute toxicity studies in Sprague-Dawley rats. The acute toxicity study for 72 h showed noadverse effects in behavior or mortality at a dosage of 75-2,000 mg/kg of BW. The sub-acute toxicity study at 50,100, 250, and 500 mg/kg of BW for 30 days showedtransient rises in the white blood cell count, and levels ofhemoglobin, free fatty acids, high density lipoproteins, andcholesterol, and a significant decrease in the blood glucose,cholesterol, triglyceride, phospholipid, and LDL levels. Other parameters remained unchanged. Changes observedwere significant only at the highest dosage of 500 mg/kgBW. These results proved that the drug SM is safe and nottoxic.

A Honey-Hive based Efficient Data Aggregation in Wireless Sensor Networks

Ramachandran, Nandhakumar,Perumal, Varalakshmi The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

The advent of Wireless Sensor Networks (WSN) has led to their use in numerous applications. Sensors are autonomous in nature and are constrained by limited resources. Designing an autonomous topology with criteria for economic and energy conservation is considered a major goal in WSN. The proposed honey-hive clustering consumes minimum energy and resources with minimal transmission delay compared to the existing approaches. The honey-hive approach consists of two phases. The first phase is an Intra-Cluster Min-Max Discrepancy (ICMMD) analysis, which is based on the local honey-hive data gathering technique and the second phase is Inter-Cluster Frequency Matching (ICFM), which is based on the global optimal data aggregation. The proposed data aggregation mechanism increases the optimal connectivity range of the sensor node to a considerable degree for inter-cluster and intra-cluster coverage with an improved optimal energy conservation.

Enantioselective Liquid–Liquid Extractions of Underivatized General Amino Acids with a Chiral Ketone Extractant

Huang, Haofei,Nandhakumar, Raju,Choi, Misun,Su, Zhishan,Kim, Kwan Mook American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.7

<P>The chiral ketone (<I>S</I>)-<B>3</B> shows high kinetic enantioselectivities toward the <SMALL>l</SMALL> form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the <SMALL>d</SMALL> form for cysteine with its −SH polar side chain when used as an extractant in enantioselective liquid–liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are <SMALL>l</SMALL>-form-selective.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-7/ja3105945/production/images/medium/ja-2012-105945_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja3105945'>ACS Electronic Supporting Info</A></P>

OFDM system with cyclostationary feature detection spectrum sensing

Arun Kumar,NandhaKumar P. 한국통신학회 2019 ICT Express Vol.5 No.1

In Orthogonal Frequency Division Multiplexing OFDM, a cyclic prefix (CP) is applied to reduce the intervention between symbols. The CP results in bandwidth wastage, and the solution to this problem leads to the cognitive radio. In the first part of the work, OFDM with CP is presented and integrated with cyclostationary spectrum sensing. Subsequently, OFDM with cyclostationary spectrum sensing without CP is proposed with the function of the filter at the transmitter and receiver being to utilize the bandwidth that is wasted in the CP phase. The Bit Error Rate BER, signal probability detection, false alarm, and error probability are obtained and analyzed.