Picric acid capped silver nanoparticles as a probe for colorimetric sensing of creatinine in human blood and cerebrospinal fluid samples.

Creatinine is the most important parameter to be determined in the diagnosis of renal, muscular and thyroid function. The most common method for the determination of creatinine is Jaffe's reaction, a routine practice for blood and urine analysis. However, in cases of icteric and haemolyzed blood samples, interference occurs during the estimation of creatinine by other constituents present in the blood like bilirubin, creatine, and urea, which lead to wrong diagnosis. To overcome such difficulty, we have developed a silver nanoparticle (Ag NPs) based sensor for the selective determination of creatinine. In this study, a new approach has been given to the traditional Jaffe's reaction, by coating Ag NPs with picric acid (PA) to form an assembly that can selectively detect creatinine. The Ag NPs based sensor proficiently and selectively recognizes creatinine due to the ability of picric acid to bind with it and form a complex. The nanoassembly and the interactions were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS) analysis, UV-Vis spectroscopy, FT-IR spectroscopy and ESI-MS, which demonstrated the binding affinity of creatinine with PA-capped Ag NPs. A linear correlation was obtained in the range of 0.01 µM-1 µM with an R(2) value of 0.9998 and a lower detection limit of 8.4 nM. The sensor was successfully applied to different types of blood and CSF samples for the determination of creatinine, and the results were compared to that of the Jaffe's method. With the advantages of high sensitivity, selectivity and low sample volume, this method is potentially suitable for the on-site monitoring of creatinine.

Estimation of postmortem interval through albumin in CSF by simple dye binding method.

Estimation of postmortem interval is a very important question in some medicolegal investigations. For the precise estimation of postmortem interval, there is a need of a method which can give accurate estimation. Bromocresol green (BCG) is a simple dye binding method and widely used in routine practice. Application of this method in forensic practice may bring revolutionary changes. In this study, cerebrospinal fluid was aspirated from cisternal puncture from 100 autopsies. A study was carried out on concentration of albumin with respect to postmortem interval. After death, albumin present in CSF undergoes changes, after 72 h of death, concentration of albumin has become 0.012 mM, and this decrease was linear from 2 h to 72 h. An important relationship was found between albumin concentration and postmortem interval with an error of ± 1-4h. The study concludes that CSF albumin can be a useful and significant parameter in estimation of postmortem interval.

A unique fluorescence biosensor for selective detection of tryptophan and histidine.

A novel photoinduced electron transfer (PET) based substituted calix[4]arene fluoroionophore has been used for the selective recognition of tryptophan (L-Trp) and histidine (L-His) by emission spectroscopy. The detection limit of the synthesized receptor was found to be 0.00826 nM for L-Trp and 0.00158 nM for L-His. Moreover, this probe has been applied for the recognition of L-Trp and L-His from blood serum.

A non enzymatic glucose biosensor based on an ultrasensitive calix[4]arene functionalized boronic acid gold nanoprobe for sensing in human blood serum.

We developed a new, advanced, simple and non enzymatic approach for the colorimetric detection of glucose based on calix[4]arene/phenyl boronic acid (CX-PBA)functionalized gold nanoparticles (AuNPs). This molecular receptor proficiently and selectively recognizes glucose due to its ability to reversibly bind diol-containing compounds. The assembly was characterized by transmission electron micrograph (TEM), dynamic light scattering (DLS), UV-Vis, FT-IR, ESI-MS and (1)H NMR spectrometry, which demonstrates the binding affinity for glucose via a boronic acid-diol interaction. The linear range for glucose was found to be 5-100 nM with phosphate buffer pH 10, with a lower detection limit of 4.3 nM. Interference by other saccharides was negligible. The biosensor has been successfully applied to estimate the glucose in human blood serum samples and the results compared well to an automatic analyzer. With the advantages of high sensitivity, selectivity and low sample volume, this method is potentially suitable for the on-site monitoring of glucose.

A highly efficient PET switch on-off-on fluorescence receptor based on calix[4]arene for the selective recognition of Cd2+ and Sr2+.

A novel PET (photoinduced electron transfer) based substituted calix[4]arene fluoroionophore has been synthesized and used for the selective recognition of Cd(2+) and Sr(2+) by emission spectra. The detection limit of the synthesized receptor was found to be 0.94 pM for Cd(2+) and 1.04 pM for Sr(2+). Moreover, this probe has been applied to the recognition of Cd(2+) and Sr(2+) in waste water.

Fluorescence switch on-off-on receptor constructed of quinoline allied calix[4]arene for selective recognition of Cu2+ from blood serum and F- from industrial waste water.

A novel PET with ICT based substituted calix[4]arene fluroionophore was synthesized and used for detection of Cu(2+) and F(-) by emission spectra. The detection limit of the synthesized receptor was found to be 4.16 nM for Cu(2+) and 2.15 nM for F(-). Moreover, this probe has been applied for recognition of Cu(2+) in blood serum and F(-) from waste water.

Melamine modified gold nanoprobe for "on-spot" colorimetric recognition of clonazepam from biological specimens.

Inexpensive, rapid, and reliable methods of detection are crucial to the control of toxicological investigations. Here we report a highly sensitive, selective and cost effective method for the detection of trace amounts of clonazepam based on gold nanoparticles (AuNPs) in the presence of melamine. Hydrogen bonding interactions between clonazepam and melamine resulted in the aggregation of AuNPs and a consequent color change of AuNPs from wine red to blue. The results showed that the absorption ratio (A636/A552) was linear for clonazepam concentrations in the range of 10 × 10(-8) to 1.0 × 10(-9) M (R(2) = 0.999). The detection limit was 8.9 × 10(-10) M (S/N = 3), which was much lower than that of most existing methods. Coexisting substances including alprazolam, diazepam, nitrazepam and lorazepam did not affect the determination of clonazepam. The sensor developed by this new approach could be used as a spot test and a good alternative means for on-site and real time screening of clonazepam. This proposed scheme was also supported by the use of real samples such as skeletal remains and blood to illustrate the applicability of the developed nanosensor by a series of experiments.

Novel cationic quinazolin-4(3H)-one conjugated fullerene nanoparticles as antimycobacterial and antimicrobial agents.

A series of novel cationic fullerene derivatives bearing a substituted-quinazolin-4(3H)-one moiety as a side arm were synthesized using the 1,3-dipolar cycloaddition reaction of C60 with azomethine ylides generated from the corresponding Schiff bases of substituted quinazolinones. The synthesized compounds 5a-f were characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, and ESI-MS and screened for their antibacterial activity against Mycobacterium tuberculosis (H37RV) and antimicrobial activity against selected Gram-positive (Staphylococcus aureus and S. pyogenes) and Gram-negative (Pseudomonas aeruginosa, Klebsiella pneumonia and Escherichia coli) bacterial and fungal strains (Candida albicans, Aspergillus clavatus, and A. niger), respectively. All the compounds exhibited significant activity, with the most effective compounds having MIC values and zones of inhibition comparable to those of standard drugs.

A novel nanoaggregation detection technique of TNT using selective and ultrasensitive nanocurcumin as a probe.

Here, for the first time, we designed an ultrasensitive nanocurcumin based nanomaterials surface energy transfer (NSET) probe for detection of trace amount of TNT with excellent sensitivity (1 nM) and selectivity over other nitro explosives via nanoaggregation and we found the largest fluorescent enhancement to date for sensing TNT (upto 800 fold).

Calixarene capped ZnS quantum dots as an optical nanoprobe for detection and determination of menadione.

In this communication we report a p-sulfonatocalix[4]arene coated ZnS quantum dots "cup type" highly stable optical probe for the detection and determination of menadione (VK(3)) with high sensitivity and selectivity. The detection of VK(3) depends on supramolecular host-guest chemistry.

An ICT based "turn on/off" quinoline armed calix[4]arene fluoroionophore: its sensing efficiency towards fluoride from waste water and Zn2+ from blood serum.

A novel structurally simple calix[4]arene appended 8-amidoquinoline linked conjugate was synthesized and has been used as a turn-on fluorescence probe for Zn(2+) and turn off fluorescence probe for F(-). Moreover, this probe has been applied for Zn(2+) detection in blood serum upto 8.7 µM and fluoride detection upto 22 nM in waste water samples, using emission spectra.

Calix[4]arene based 1,3,4-oxadiazole and thiadiazole derivatives: design, synthesis, and biological evaluation.

In the present investigation, we describe some novel calixarene based heterocyclic compounds (5a-5i) in which 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives have been coupled with 5,11,17,23-tetra-tert-butyl-25,27-bis(chlorocarbonyl-methoxy)-26,28-dihydroxy calix[4]arene. All the newly synthesized calixarene based heterocyclic compounds have been characterized by elemental analysis and various spectroscopic methods like FTIR, (1)H NMR, (13)C NMR, and FAB-MS. All the final scaffolds have been subjected to antioxidant activity, in vitro antimicrobial screening against two gram (+ve) bacteria (S. aureus, S. pyogenes), two gram (-ve) bacteria (E. coli, P. aeruginosa) and two fungal strains (C. albicans, A. clavatus) and also have been screened for their antitubercular activity against Mycobacterium tuberculosis H(37)Rv.

Development and validation of GC/MS method for determination of pramipexole in rat plasma.

A simple, rapid and sensitive method has been developed and validated for the determination of pramipexole in rat plasma by using gas chromatography mass spectrometry. The lower limit of quantification (LLOQ) is superior to the other reported LC-MS/MS methods. After being made alkaline with NaOH, plasma samples (0.1 mL) were subjected to liquid-liquid extraction using methyl-t-butyl ether. Analytes were determined using electron impact ionization in a single quadrupole mass spectrometer. GC/MS was performed in the selected ion monitoring mode using target ions at m/z 211, 212 and 152 for pramipexole and m/z 194 and 165 for caffeine as internal standard. A linear calibration curve was plotted over the range of 20-1000 pg/mL for pramipexole (r(2) > 0.996). The LLOQ was 20.0 pg/mL, respectively, which offered high sensitivity and selectivity enough for bioanalytical investigation. Inter- and intraday precisions ranged from 0.3 to 8.8% and from 0.9 to 11.33%, respectively. The recovery of pramipexole from plasma ranged from 82.4 ± 7.1 to 87.8 ± 5.7%. The method fulfills all standards required for bioanalytical methods and can be successfully applied to a pharmacokinetic study of pramipexole in rats.

Recognition of lysine, arginine and histidine by novel p-sulfonatocalix[4]arene thiol functionalized gold nanoparticles in aqueous solution.

This communication reports novel p-sulfonatocalix[4]arene thiol modified gold nanoparticles as a colorimetric sensor to probe lysine, arginine and histidine in water.

Potassium ion recognition by facile dithiocarbamate assembly of benzo-15-crown-5-gold nanoparticles.

Here we demonstrate a facile strategy of preparing gold nanoparticle (AuNP) crown ether assemblies by the generation of strongly binding dithiocarbamate (DTC) modified benzo-15-crown-5; we also report the efficient and selective ion sensing property of the novel assembly for K(+).

Determination of Time since Death using Vitreous Humor Tryptophan.

Determination of time since death (TSD) plays very important role in forensic examination as it narrows down field of suspects and aids in deceased identification. This study utilizes the fluorescence property of vitreous humor (VH) tryptophan to determine TSD using o-phthalaldehyde (OPA). The detection limit of these fluorometric studies was found to be 8 ppb indicating sensitivity and high accuracy in TSD determination. The study was performed on selected 76 cadaver with known TSD ranging from 3 to 90 h. Excellent correlation between VH tryptophan and TSD was obtained with a coefficient of correlation R2 = 0.9590. Results showed statistically significant increase in vitreous tryptophan with TSD up to 90 h, and the proposed method was efficaciously applied for prediction of TSD as no systematic error exist. The regression equation obtained from the study is [Trp] = 2.21 + 2.98 * TSD.

Isolation of PCR ready-human DNA using copper nanoparticles from skeletal remains.

Present study represents a novel approach of PCR ready-human DNA extraction method from skeletal remains using copper nanoparticles (CuNPs) for personnel identification. To achieve rapid, cost effective, sensitive and non-hazardous method for DNA extraction we utilized CuNPs synthesized using microwave. The applicability of this approach was first tested in blood samples and afterwards, this system was extended to skeletal remains' samples also. This method yields good quality DNA that are ready for PCR reactions from small quantities of blood and skeletal remains. Consequently, even small quantities of nanoparticles could be potentially utilized for a highly efficient isolation of DNA from skeletal remains as well as from ancient archaeological samples. The present method has the advantages that it is quick with high yield, inexpensive, robust, environment friendly and does not require use of hazardous organic solvents.

Smart platform for the time since death determination from vitreous humor cystine.

In this work, we report the smart application of AgNPs based sensors for determination of time since death (TSD) via recognition and quantification of vitreous humor (VH) cystine as well as provide the portability for on spot determination of TSD. The lower detection limit was found to be 7.0ng/ml with prominent selectivity. It was found that there is a linear correlation between the VH cystine concentration and TSD as the concentration of cystine increases up to 96h±3.9h. Further for the first time TSD determination is given a smart approach and it proves to have a great utility up to 24h±2.6h. The linear regression equation between TSD (the dependent variable), RGB intensity of cystine concentration till 24h (the independent variable) was found to be TSD=26.69+-0.05*x. The proposed method gives the smart detection, portability, rapidity, sensitivity, selectivity as well as cost effectiveness for determination of time since death.

A simple and rapid creatinine sensing via DLS selectivity, using calix[4]arene thiol functionalized gold nanoparticles.

A new, simple, ultra-sensitive and selective approach has been reported for the "on spot" colorimetric detection of creatinine based on calix[4]arene functionalized gold nanoparticles (AuNPs) with excellent discrimination in the presence of other biomolecules. The lower detection limit of the method is 2.16nM. The gold nanoparticles and p-tert-butylcalix[4]arene were synthesized by microwave assisted method. Specifically, in our study, we used dynamic light scattering (DLS) which is a powerful method for the determination of small changes in particle size, improved selectivity and sensitivity of the creatinine detection system over colorimetric method. The nanoassembly is characterized by Transmission electron microscopy (TEM), DLS, UV-vis and ESI-MS spectroscopy, which demonstrates the binding affinity due its ability of hydrogen bonding and electrostatic interaction between -NH group of creatinine and pSDSC4. It exhibits fast response time (<60s) to creatinine and has long shelf-life (>5 weeks). The developed pSDSC4-AuNPs based creatinine biosensor will be established as simple, reliable and accurate tool for the determination of creatinine in human urine samples.

A novel calix[4]arene thiol functionalized silver nanoprobe for selective recognition of ferric ion with nanomolar sensitivity via DLS selectivity in human biological fluid.

A high concern for human health and safety has motivated dynamic research on the potential impact of transition metal ions and their toxic effects, thus it is very challenging to design transition-metal ion detection devices that are cost-effective, rapid and applicable to the biological milieus. Driven by the need to detect trace amounts of Fe(3+) from blood samples, we report a highly selective and ultrasensitive calix[4]arene modified silver nanoprobe for Fe(3+) recognition at the 9.4 nM level from aqueous solution with excellent discrimination against other heavy metals and biomolecules. The assembly was characterized by TEM (transmission electron microscopy), DLS (dynamic light scattering), UV-Vis, FT-IR, ESI-MS and (1)H NMR spectrometry, which demonstrate the higher binding affinity for Fe(3+). The biosensor has been successfully applied to estimate the ferric ion in human blood serum as well as in human hemoglobin.