Nikhil R. Jana

Synthesis of nanobioconjugates with a controlled average number of biomolecules between 1 and 100 per nanoparticle and observation of multivalency dependent interaction with proteins and cells.

Multivalency of nanoparticle and associated cooperative binding with biological interface is an important aspect in the development of nanoparticle based bioimaging probes. However, the preparation of such a nanobioconjugate with a controlled number of biomolecules per nanoparticle, typically between 1 and 100, is challenging. Here we report a generalized two-step bioconjugation method to prepare nanobioconjugates with a varied average number of biomolecules between 1 to 100 per nanoparticle that can be applied to different nanoparticles and biomolecules. Following this approach we have successfully synthesized quantum dot (QD) based bioconjugates with controlled average numbers of glucose or folate and found their number-dependent interaction with proteins and cells. We propose a method for exploiting the nanoparticle multivalency effect toward various biological interactions and preparing such nanobioconjugates for best performance.

Prevention of photooxidation in blue-green emitting Cu doped ZnSe nanocrystals

This communication highlights unstable blue-green emitting Cu doped ZnSe nanocrystals stabilized by diluting the surface Se with a calculated amount of S.

Gold nanoclusters with enhanced tunable fluorescence as bioimaging probes

Development of unique bioimaging probes offering essential informations about bio environments are an important step forward in biomedical science. Nanotechnology offers variety of novel imaging nanoprobes having high-photo stability as compared to conventional molecular probes which often experience rapid photo bleaching problem. Although great advances have been made on the development of semiconductor nanocrystals-based fluorescent imaging probes, potential toxicity issue by heavy metal component limits their in vivo therapeutic and clinical application. Recent works show that fluorescent gold clusters (FGCs) can be a promising nontoxic alternative of semiconductor nanocrystals. FGCs derived imaging nanoprobes offer stable and tunable visible emission, small hydrodynamic size, high biocompatibility and have been exploited in variety in vitro and in vivo imaging applications. In this review, we will focus on the synthetic advances and bioimaging application potentials of FGCs. In particular, we will emphasize on functional FGCs that are bright and stable enough to be useful as bioimaging probes.

Inhibition of Amyloid Fibril Growth and Dissolution of Amyloid Fibrils by Curcumin–Gold Nanoparticles

Inhibition of amyloid fibrillation and clearance of amyloid fibrils/plaques are essential for the prevention and treatment of various neurodegenerative disorders involving protein aggregation. Herein, we report curcumin-functionalized gold nanoparticles (Au-curcumin) of hydrodynamic diameter 10-25 nm, which serve to inhibit amyloid fibrillation and disintegrate/dissolve amyloid fibrils. In nanoparticle form, curcumin is water-soluble and can efficiently interact with amyloid protein/peptide, offering enhanced performance in inhibiting amyloid fibrillation and dissolving amyloid fibrils. Our results imply that nanoparticle-based artificial molecular chaperones may offer a promising therapeutic approach to combat neurodegenerative disease.

Synthesis of silver–graphene nanocomposite and its catalytic application for the one-pot three-component coupling reaction and one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles in water

A graphene based composite with silver nanoparticles has been synthesized via a simple chemical route and its catalytic activity has been tested for multi-component reactions and click reaction in a one-pot approach. This silver–graphene nanocomposite shows excellent catalytic activity at room temperature for three-component couplings between aldehydes, alkynes and amines (A3-coupling) and one-pot synthesis of 1,4-disubstituted 1,2,3-triazole via click reaction between in situ generated azides (derived from anilines or amines) and terminal acetylenes. This solid silver–graphene catalyst has been characterized by TEM, Raman, XRD and UV-Visible absorption spectra. The developed catalyst is air-stable, inexpensive, easy to prepare and can be facilely recovered and reused five times without significant decrease in activity and selectivity.

Enhanced catalytic performance by copper nanoparticle–graphene based composite

A graphene based composite with copper nanoparticles (Cu–G) has been synthesized and used as catalyst for N-arylation and O-arylation. The structure and composition of the nanocomposite have been characterized by TEM, AFM, Raman and XPS. The catalytic activity of the Cu–G has been tested for the N-arylation of N–H heterocycles using arylboronic acids and the O-arylation of phenols using aryl halides. The catalytic N-arylation produces N-aryl heterocyles and the catalytic O-arylation produces diaryl ethers, under mild reaction conditions with excellent yields and selectivities. The developed catalyst is air-stable, inexpensive, easy to prepare, easy to recover by simple filtration and can be reused without appreciable loss of activity.

Thiol‐Directed Synthesis of Highly Fluorescent Gold Clusters and Their Conversion into Stable Imaging Nanoprobes

Fluorescent gold clusters (FGCs) with tunable emission from blue to red and quantum yields in the range of 6-17% have been synthesized by simple modification of the conditions used for the synthesis of gold nanoparticles, namely by replacing the stronger reducing agent with a controlled amount of thiol. Various functional FGCs with hydrodynamic diameters of 5-12 nm have been successfully synthesized and used as cell labels. The results of our investigations strongly indicate that FGCs composed of Au(0) are more stable imaging probes than commonly reported red/NIR-emitting FGCs with a composition of Au(0)/Au(I), as this combination rapidly transforms into nonfluorescent large clusters on exposure to light. The FGC-based nanoprobes reported herein exhibit stable fluorescence upon continuous light exposure and can be used as imaging probes with low cytotoxicity.

Functional, mesoporous, superparamagnetic colloidal sorbents for efficient removal of toxic metals

γ-Fe(2)O(3) incorporated mesoporous silica particles of 50-100 nm size have been synthesized which are functionalized with chelating agents of metal ions. These particles are water dispersible but aggregate in response to the external magnetic field and have been used for high performance and selective removal of Cd, Pb, Hg and As.

Graphene-based composite with γ-Fe2O3 nanoparticle for the high-performance removal of endocrine-disrupting compounds from water.

Graphene is a 2D sp(2)-hybridized carbon sheet and an ideal material for the adsorption-based separation of organic pollutants. However, such potential applications of graphene are largely limited, owing to their poor solubility and extensive aggregation properties through graphene-graphene interactions. Herein, we report the synthesis of graphene-based composites with γ-Fe2O3 nanoparticle for the high-performance removal of endocrine-disrupting compounds (EDC) from water. The γ-Fe2O3 nanoparticles partially inhibit these graphene-graphene interactions and offer water dispersibility of the composite without compromising much of the high surface area of graphene. In their dispersed form, the graphene component offers the efficient adsorption of EDC, whilst the magnetic iron-oxide component offers easier magnetic separation of adsorbed EDC.

Dopamine functionalized polymeric nanoparticle for targeted drug delivery

A biocompatible drug delivery nanocarrier with cellular and subcellular targeting properties can greatly enhance the therapeutic effect towards various diseases. Here, we report polyaspartamide based functional polymeric nanoparticles as drug delivery carriers for targeting at the cellular and subcellular length scale. The polymeric nanoparticle has a polyaspartamide backbone with both octadecyl and dopamine functional groups and produces polymeric nanoparticles in water with the exposed dopamine. This polymeric nanoparticle has good encapsulation efficiency for hydrophobic drugs and offers cellular delivery of the drug into dopamine receptor positive human colon adenocarcinoma cells. Using this approach three different drugs (e.g. curcumin, camptothecin and doxorubicin) are selectively delivered to human colon adenocarcinoma cells. Subcellular imaging study shows that the delivered drugs retain their ability to target subcellular organelles and thus curcumin targets mitochondria and doxorubicin targets the nucleus. This polymeric nanoparticle can be used as an alternative drug delivery carrier for in vitro and in vivo applications.