Colorimetric detection of hydrogen peroxide and cholesterol using Fe3O4-brominated graphene nanocomposite.

Fe3O4-brominated graphene (Fe3O4-GBR) nanocomposites were synthesized via an in situ method using the precursors FeSO4.7H2O and GBR in different (1:1, 1:2, 2:1, 1:5, 1:10, 1:20, and 5:1) weight ratios at pH 11.5. The Fe3O4-GBR (1:5) nanocomposite in combination with H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB) showed swift and superior intrinsic peroxidase mimetic enzyme activity compared with the other Fe3O4-GBR composites, GBR and Fe3O4, as observed by colorimetry. It was characterized using high-resolution scanning electron microscopy (HRSEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Its catalytic activity was optimized by varying different parameters, and the optimum conditions for peroxidase mimetic activity were observed using 100 µL Fe3O4-GBR (1 mg/mL), 50 µL TMB (1 mg/mL), and 200 µL H2O2(1 mM) in 400 µL of acetate buffer of pH 2.3 at 30 °C temperature. Kinetic analysis has revealed the Michaelis-Menten kinetic behavior of peroxidase activity with Michaelis-Menten constants (Km) and maximum initial velocities (Vmax) of 0.082 mM and 14.1 nMs-1 respectively, for H2O2 and 0.086 mM and 5.1 nMs-1, respectively for TMB. The limit of detection and linear range were found to be 49.6 µM and 100-880 µM, respectively, for H2O2 and 41.9 µM and 47.6-952.3 µM, respectively, for cholesterol. On this basis, a simple, swift, sensitive, selective, and reproducible colorimetric assay to detect cholesterol levels in blood serum samples using Fe3O4-GBR nanocomposite has been developed. Thus, Fe3O4-GBR composite as compared to Fe3O4 and GBR has shown better peroxidase mimicking activity for biosensing.

Doxorubicin loaded pH responsive biodegradable ABA-type Amphiphilic PEG-b-aliphatic Polyketal-b-PEG block copolymer for therapy against aggressive murine lymphoma.

A novel ABA-type polyethylene glycol (PEG)-b-polyketal (PK)-b-PEG block copolymer was synthesized via click reactions between the monoazido-monomethoxy-PEG and dialkyne terminated aliphatic polyketal with no carboxylic/amide linkages. Formation of the novel block copolymer was confirmed by 1H NMR, GPC, TGA, and DSC studies. The formed copolymer has shown faster degradation at acidic pH. Self-assembly of this block copolymer (average size 6.2 nm) was assessed by fluorescence study using pyrene as a probe. Doxorubicin loaded block copolymeric micelles (69.9 nm) have shown pH dependent elevated drug release at pH 6.4, indicating its potential as a pH responsive nano-carrier for anticancer therapy. The nano-sized copolymer demonstrated tumoricidal activities against the lymphoma of murine and human origin with significant levels of growth inhibition and apoptosis. Therapy with doxorubicin loaded copolymer reduced the tumor size and augmented the life span of the tumor bearing animals with improved histopathological parameters, compared with the untreated control.

Highly selective fluorescence 'turn off' sensing of picric acid and efficient cell labelling by water-soluble luminescent anthracene-bridged poly(N-vinyl pyrrolidone).

A novel, water-soluble, luminescent anthracene-bridged AA-type bi-arm poly(N-vinylpyrrolidone) (ATC-PNVP) was synthesized using a click reaction between alkyne-terminated PNVP and 9,10-bis(azidomethyl)anthracene. The resultant anthracene-bridged PNVP (ATC-PNVP) was characterized using 1H NMR, FTIR, UV-Vis, and fluorescence spectroscopic methods and GPC analysis. ATC-PNVP showed effective fluorescence properties in an aqueous medium. It showed highly selective "turn off" sensing behaviour towards picric acid, a common nitro-aromatic explosive, with a wide linear range of detection of 0.01-0.3 mM and LOD value of 0.006 mM in water. ATC-PNVP-based paper sensors also showed very effective detection of picric acid in the concentration range 0.001-1.0 mM. Its binding with bovine serum albumin (BSA) was studied using steady-state, synchronous and 3D fluorescence spectroscopy and this study showed effective quenching of the intrinsic fluorescence of BSA and occurrence of a FRET-type interaction. Furthermore, this luminescent ATC-PNVP was efficiently used as a fluorescence microscopy labelling agent in NIH-3T3 and HeLa cells, and showed greater uptake and hence better fluorescent labelling in the cytosols of the tested cells than free 9,10-bis(azidomethyl) anthracene. The cell viability study also showed a very good biocompatible and non-toxic nature of ATC-PNVP at lower working concentrations towards each of the types of cells tested.

Study of the Fluorescence Based Applications of Pyrene-Tagged Poly(N-vinyl-2-pyrrolidone).

In this study we have explored the fluorescence based applications of luminescent pyrene-tagged PNVP (PyPNVP) reported in our previous work (Int. J. Polym. Mater. Polym. Biomater. 2016, 65, 269-276). PyPNVP has successfully acted as "turn off" chemosensor for metal ions Cu2+, Hg2+, and Pb2+. It has also successfully acted as a fluorescent probe for critical micellar concentration (CMC) determination of amphiphilic block copolymer of poly(d,l-lactide) and poly(N-vinylpyrrolidone) (PDLLA42-b-PNVP120) (Mn = 19 400 g/mol and PD = 1.52). It has also successfully shown an interaction with both plasmid and calf thymus (CT) deoxyribonucleic acids (DNAs) as evidenced by its fluorescence quenching. A different magnitude and type of quenching has been observed for both the cases which may be useful in distinguishing different kinds of DNAs. In order to further understand the potential of PyPNVP in various biotechnological processes, its binding property with bovine serum albumin (BSA) has also been studied. The efficient quenching of intrinsic fluorescence of BSA by PyPNVP through binding and the occurrence of the fluorescence resonance energy transfer (FRET) type of interaction have been studied using steady state, synchronous, and 3D fluorescence spectroscopies. Moreover, a fluorescence microscopic cell imaging study has revealed the significant uptake of PyPNVP in the nucleus of HEPG2 and U87 cells compared to free Py. In addition, the cytotoxicity study showed the tolerance of PyPNVP in all the cell lines tested with no significant cytotoxicity at lower concentrations.