Jasminder Singh

Selective chemosensing of spermidine based on fluorescent organic nanoparticles in aqueous media via a Fe3+ displacement assay

A novel fluorescent chemosensor based on fluorescent organic nanoparticles (F1) has been synthesized. This tripodal framework shows significant fluorescence quenching for Fe3+ ions from among nineteen metal ions due to the formation of a F1·Fe3+ complex. The lowest detectable concentration of F1 for Fe3+ ions was found to be 1.66 μM. Upon the addition of spermidine (a biologically active amine), the fluorescence intensity of the aqueous solution of complex increases with a detection limit of 3.68 μM indicating that spermidine can displace Fe3+ ions from the F1·Fe3+ complex. Moreover, the recognition of spermidine was selective with no interference from other biogenic amines studied. Thus, F1·Fe3+ acts as a potential sensor for spermidine through a cation displacement assay in aqueous media.

Naphthalimide-based organic nanoparticles for aluminium recognition in acidic soil and aqueous media

An organic compound 1 was prepared using 1,8-naphthalimide and diethylenetriamine, and the resultant receptor showed interesting potential for metal recognition. The chemosensor activity of the naphthalimide-based receptor was evaluated following the synthesis of the organic nanoparticles (ONPs) using a reprecipitation method. The organic nanoparticles were evaluated for their photophysical properties, mainly using fluorescence spectroscopy in aqueous media, and the studies revealed that the ONPs selectively recognized aluminium ions in aqueous media. The sensor showed competitive binding for Al3+ and none of the other metal ions tested caused any interference in the detection of Al3+. Titrations were performed with aluminium ions, and the lowest detection limit calculated was 677 nM. The sensor was used to determine the Al3+ content of river water and acidic soils; results were validated using existing methods and the performance of the ONPs was found to be in a satisfactory error range. Finally, the mechanism of fluorescence recognition was further confirmed using DFT calculations, which showed that the aluminium, upon addition to receptor 1, takes away the excess electrons i.e. a lone pair from the central nitrogen of the diethylenetriamine part of receptor 1. This causes a reduction in photo-induced electron transfer (PET) and an increase in fluorescence intensity, which was authenticated using NMR and UV-Visible spectroscopic titrations of receptor 1 with Al3+ ions.

Fluorescent organic nanoparticles of tripodal receptor as sensors for HSO4− in aqueous medium: application to real sample analysis

A tripodal framework bearing mixed donor sites was synthesized using simple reactions and was used for sensor applications in an aqueous medium by subjecting it to a nano-aggregate (N1) formation using a re-precipitation method. The characteristic fluorescence profile of the receptor due to the naphthyl moiety was observed. N1 showed selective recognition behaviour towards HSO4− in aqueous medium with a good linear range of 0–65 μM. N1, the prepared nano-aggregates can be used to determine a lower concentration, as the detection limit for HSO4− ions in aqueous samples is 1.12 μM in a wide pH range; thus, making them appropriate for the use in environmental or biological samples.

Fluorometric appraisal of HSO4− in aqueous media and daily utilities using organic–inorganic nanohybrids

Receptor 1 based on rhodamine dye was designed and characterized using 1H, 13C NMR and mass spectroscopy like spectroscopic techniques. Re-precipitation methods have been used for developing nano-aggregates of 1 (N1) in aqueous medium, which were further used for preparation of inorganic–organic hybrid nanomaterial (H1) i.e. by coating organic nanoparticles with gold nanoparticles. Changes in the photophysical profile by anion binding of N1 and H1 were evaluated using fluorescence spectroscopy. No selectivity was perceived with nano-aggregates (N1) for any anion. However, the hybrid nanomaterial (H1) selectively recognized HSO4− through enhancement of fluorescence emission intensity in aqueous medium. Thus, the hybrid nanomaterial (H1) has been established for sensing of HSO4− and was considered for various parameters like rapid response, good stability in water and is validated for determination of HSO4− ions in daily use items.

Urea based organic nanoparticles for selective determination of NADH

Dipodal receptor 1 was synthesized using a single step procedure. The prepared receptor was subjected to organic nanoparticles (N1) and its sensor activities were tested with various biomolecules on the basis of changes in its photo-physical properties. Receptor responded selectively for reduced nicotineamide adenine dinucleotide; with a linear detection range upto 340 nM, having a detection limit of 96 nM, selective determination of NADH using N1 was not affected by the presence of any other potential interfering biomolecule or even in the presence of a higher concentration of salt.

Calix[4]arene based dipodal receptor nanohybrids for selective determination of chloride ions in aqueous media

A chemical sensor based on p-tert butyl calix[4]arene has been synthesized and characterized using an assortment of spectroscopic techniques such as (1)H NMR, (13)C NMR, and elemental analysis. For sensor application, organic nanoparticles (N1) of 1 have been primed by implementing re-precipitation technique, which were further employed for preparing organic-inorganic hybrid (H1) by decorating N1 with gold nanoparticles. Both N1 and H1 were characterized using UV-visible, fluorescence, and DLS studies. Photo-physical changes due to anion binding with H1 were scrutinized using UV-visible absorption spectrometer and found it to promptly and selectively recognize Cl(-) ions in aqueous media. Thus, H1 can be effectively used for recognition of Cl(-) ions in aqueous media over a wide pH range, in samples of real time importance with a detection limit of 2.84×10(-9) M with a linear detection range up to 50 μM.

Fe(III) conjugated fluorescent organic nanoparticles for ratiometric detection of tyramine in aqueous medium: A novel method to determine food quality

A tetrapodal receptor was synthesized and was processed into fluorescent organic nanoparticles (FONs) for determination of important analytes in aqueous medium. The receptor was fully characterized using characterization techniques. Recognition behavior of FONs towards different metal ions was investigated with fluorescence spectroscopy, amongst them Fe3+ ions showed quenching behavior in the emission spectra. The Fe3+ ion complex of FONs based sensor was further tested with different biogenic amines and ratiometric response was obtained for tyramine. Fluorescence emission profile of FONs. Fe3+ ion complex showed no change in the pH in wide range; thereby increasing their utility in biological and environmental samples. Tyramine detection was linearly proportional in response with the detection limit of 377 nM.

An organic–inorganic nanohybrid of a calix[4]arene based chromogenic chemosensor for simultaneous estimation of ADP and NADH

The versatility in the environmental and biological applications of nanohybrids encouraged us to prepare a novel chemosensor based on an organic–inorganic nanohybrid (H1) employing receptor 1 (R1), which was synthesized via the Schiff’s base condensation reaction of a calix[4]arene derivative and an aliphatic amine. Techniques such as DLS and TEM were employed for the characterization of organic nanoparticles (N1) and H1. Further, sensor properties of H1 were explored towards various biologically important molecules in aqueous media using UV-visible spectroscopy. The proposed sensor responded effectively for the selective and simultaneous nanomolar determination of adenosine diphosphate (ADP) and reduced nicotiniamide adenine dinucleotide (NADH). The response was not affected by the presence of each analyte or any other potentially interfering biomolecule or a high concentration of salt. The proposed sensor was also found to show a stable response in an extensive pH range thus widening its practical applicability. H1 was able to detect a minimum concentration (detection limit) of 6.11 × 10−9 M of ADP and 4.87 × 10−9 M of NADH. The prepared hybrid was subjected to real sample analysis for the determination of ADP and NADH in samples prepared artificially by adding known concentrations of NADH and ADP in solution and also in a mixture of both.

Cerebral Venous Sinus Thrombosis Presenting as Cortical Blindness

Dear Editor, A 30-year-old male, alcoholic, smoker presented with a headache of moderate intensity, associated with multiple episodes of vomiting, which he had for the past three days. The headache was associated with bilateral vision loss that started one day ago before admission. On examination, the patient was conscious and well oriented to time place and person. The vitals of the patient was normal. On neurologic examination, higher mental functions were intact. Ophthalmologic examination revealed that visual acuity was reduced to a perception of light bilaterally, both eyes exhibited normal pupillary reflex without movement restriction. The patient’s fundus examination showed bilateral hyperaemic discs and a mildly swollen left disc (Figure 1). Bilateral plantar reflexes were flexor, and the rest of the neurologic examination was unremarkable. The patients routine blood parameters (hematologic and biochemical) were normal. A contrast-enhanced computed tomography scan of the brain showed a non-enhancing hypodensity in the bilateral occipital and left parieto-temporal region involving both gray and white matter not restricted to an arterial territory (1). The patient’s brain magnetic resonance imaging (MRI) and MRI venography was performed, which showed acute infarct in the bilateral parieto-occipital region (Figure 2). MRI venography revealed diffuse attenuation of flow-related enhancement of the right transverse, right sigmoid sinus, proximal part of left transverse sinus and right internal jugular vein suggestive of thrombosis (Figure 3). Treatment with body weight-adjusted low-molecular-weight heparin (2) initially and followed later by warfarin resulted in partial recovery of vision and relief of headache. Currently, the patient is on our regular follow-up, and he has been advised against alcohol intake. Later an extensive search for any underlying hypercoagulable state (3) was performed including protein C and S level, anti-thrombin three levels, factor 5 Leiden and prothrombin gene mutations, anti-phospholipids antibodies, anti-nuclear

Retroperitoneal Haematoma in a Patient with Dengue Haemorrhagic Fever: A Rare Case Report

Dengue Haemorrhagic Fever (DHF) has diverse manifestations ranging from asymptomatic petechial skin haemorrhages to life threatening cerebral, pulmonary, gastrointestinal and genitourinary haemorrhages. However, the association of spontaneous retroperitoneal haematomas with DHF is not well documented in literature. We report a rare case of spontaneous retroperitoneal haematoma complicating DHF.