S. Uday Kumar

Perturbation of cellular mechanistic system by silver nanoparticle toxicity: Cytotoxic, genotoxic and epigenetic potentials

Currently the applications of silver nanoparticles (Ag NPs) are gaining overwhelming response due to the advancement of nanotechnology. However, only limited information is available with regard to their toxicity mechanism in different species. It is very essential to understand the complete molecular mechanism to explore the functional and long term applications of Ag NPs. Ag NPs could be toxic at cellular, subcellular, biomolecular, and epigenetic levels. Toxicity effects induced by Ag NPs have been evaluated using numerous in vitro and in vivo models, but still there are contradictions in interpretations due to disparity in methodology, test endpoints and several other model parameters which needs to be considered. Thus, this review article focuses on the progressive elucidation of molecular mechanism of toxicity induced by Ag NPs in various in vitro and in vivo models. Apart from these, this review also highlights the various ignored factors which are to be considered during toxicity studies.

A novel one-step synthesis of PEG passivated multicolour fluorescent carbon dots for potential biolabeling application

Poly(ethylene glycol) passivated multicolour fluorescent carbon dots (CPs) were synthesised by a novel one-step method and their biolabeling mechanism was studied using S. aureus and recombinant green fluorescent protein (GFP)-expressing E.coli as model systems. The mechanism of formation of fluorescent carbon nanorods from CPs was also explored.

Controlled delivery of bPEI–niclosamide complexes by PEO nanofibers and evaluation of its anti-neoplastic potentials

Since the turn of the 21st century, nanofiber based drug delivery systems have evolved drastically to attain controlled and sustained delivery of various bioactive molecules. In spite of such efforts, the tangible interface existing between the target cells and the drug molecules could not be narrowed down. This drawback has been overcome in this work by realizing nanofiber based scaffold for delivery of polymer-drug complexes rather than just the drug. In course with this, in the present study a differentially cross-linkable bPEI-PEO (branched-polyethylenimine-poly(ethylene oxide)) based nanofiber is fabricated for tunable delivery of bPEI-niclosamide complexes. Hydrophilic bPEI-niclosamide complexes are pre-synthesized and stabilized by crosslinking agent, which were then incorporated into bPEI-PEO nanofibers by electrospinning. The niclosamide loaded nanofibers by virtue of bPEI moieties presence were then cross-linked to different degrees which in turn altered bPEI-niclosamide release profile. The release kinetics of bPEI-niclosamide complexes from nanofibers was elucidated further by Korsmeyer-Peppas model. Apart from this, the versatile nature of bPEI-PEO nanofibers was also validated for different drug loading concentration and extent of crosslinking. The fibers antitumor efficacy was then assessed against A549 (Non-small cell lung cancer cells) and U-87 MG (glioblastoma cells) at two different time points (at 48h and 96h) in order to realize the importance of release profile in manifestation of different therapeutic outcomes. Thus, this work endows niclosamide a new life for anticancer application which has remained elusive till date due to its hydrophobic nature.

Bionanotherapeutics: niclosamide encapsulated albumin nanoparticles as a novel drug delivery system for cancer therapy

One of the major unresolved challenges among the scientific community is to develop anticancer drugs that are safe and effective. A large number of anticancer drugs have been screened so far in this campaign. Among them niclosamide has shown tremendous anti-cancer potential as demonstrated in a surfeit of human cancer cell lines and animal models. But the extreme hydrophobicity and consequently, minimal systemic bioavailability associated with this drug limited its widespread clinical applications. Nanoparticles based drug delivery systems have the potential for realizing water soluble formulation of highly hydrophobic anticancer drugs like niclosamide, thus evading the drawbacks of poor solubility. In this work niclosamide was encapsulated into albumin nanoparticles through a desolvation method to improve its scope of application in cancer therapy. Physico-chemical characterization confirms that the prepared nanoparticles are spherical, highly monodispersed, and stable in aqueous systems. These drug encapsulated albumin nanoparticles, unlike the free drug demonstrate better in vitro therapeutic efficacy against human lung and breast cancer cell lines, as assessed by cell viability assay and morphological analyses. Further, the proficient induction of apoptosis by these nanoparticles was confirmed by semi-quantitative RT-PCR. This work open up a new avenue to extend the clinical gamut of this effectual agent by enabling its aqueous dispersion.

Differentially cross-linkable core–shell nanofibers for tunable delivery of anticancer drugs: synthesis, characterization and their anticancer efficacy

This work introduces a new dimension for controlled drug delivery by nanofiber based scaffolds for anticancer therapy. The model anticancer drugs adopted in this work are curcumin and 5-fluorouracil (5-FU). Most of the drug loaded nanofibers synthesized thus far have failed to address the needs of personalized medication due to poor scalability of drug loading and delivery kinetics. This work opens up new avenues for circumventing such complications by altering the drug release profile by a simple one-step crosslinking reaction. With an aim to emphasize the role of polymer crosslinking in drug release kinetics, two variations of dual drug loaded core–shell nanofibers were synthesized with different extents of crosslinking and polymer composition. These two variations of drug loaded nanofibers exhibited contrasting 5-FU release profiles and thus manifested different therapeutic efficacy at different time points against A549 (Non-Small Cell Lung cancer) cells. The drug release profile of these fibers was further corroborated by different kinetic models to gain a perspective on the underlying mechanism driving the drug release from type I and type II nanofibers. The synergistic therapeutic potential of curcumin and 5-FU loaded core–shell nanofibers (type I and type II nanofibers) was also validated against A549 cells. As an outcome of this work, a clear correlation of cell viability with time lag in drug delivery in the case of type I and type II nanofibers could be drawn, which makes nanofiber based drug delivery even more flexible and therapeutically effective with minimal side effects.

Prodrug encapsulated albumin nanoparticles as an alternative approach to manifest anti-proliferative effects of suicide gene therapy

Conventional anticancer agents are associated with limited therapeutic efficacy and substantial nonspecific cytotoxicity. Thus, there is an imminent need for an alternative approach that can specifically annihilate the cancer cells with minimal side effects. Among such alternative approaches, CD::UPRT (cytosine deaminase uracil phosphoribosyl transferase) suicide gene therapy has tremendous potential due to its high efficacy. Prodrug 5-Fluorocytosine (5-FC) used in combination with CD::UPRT suicide gene suffers from limited solubility which subsequently leads to decline in therapeutic efficacy. In order to overcome this, 5-FC encapsulated bovine serum albumin nanoparticles (BSA-5-FC NPs) were prepared in this work by desolvation method. Physico-chemical characterizations studies revealed amorphous nature of BSA-5-FC NPs with uniform spherical morphology. Apart from increase in solubility, encapsulated 5-FC followed slow and sustained release profile. Suicide gene expressing stable clone of L-132 cells were adapted for investigating therapeutic potential of BSA-5-FC NPs. These nanoparticles were readily taken up by the cells in a concentration dependent manner and subsequently manifested apoptosis, which was further confirmed by morphological examination and gene expression analysis. These findings clearly illustrate that CD::UPRT suicide gene therapy can be efficiently utilized in combination with this nanosystem for improved suicide gene therapy and tumor eradication.

Multifunctional carbon dots as efficient fluorescent nanotags for tracking cells through successive generations

Although extensive reports on the synthesis and application of diverse carbon dots (CDs) merely for the sake of live cell imaging already exists, their bid in fluorescence based cell assays still remains limited. Thus, taking the CDs bio-labelling application a step further, in the present work biocompatible multicolour fluorescent CDs have been synthesised from casein, which, in addition to labelling cells, also efficiently tracks them through successive generations. As an implication of this, these CDs, upon internalization by cells, could categorise an entire cell population into multiple generations with a resolution much better than that attained by commercial cell tracking organic dyes. In addition to this, as-prepared CDs also revealed an interesting inherent ability to selectively label E. coli (Gram negative) and exclude S. aureus (Gram positive) in a mixed population which further extends their scope for diagnostic applications. With an outcome of such intriguing applications of these CDs, the present work also outlines the synthesis of CDs followed by comprehensive characterization of fluorescence and physico-chemical properties of the as-prepared CDs. In brief, this study adds a new facet to commercial applications of CDs as an efficient alternative to organic dyes for bio-labelling assays.

Synthesis and bio-evaluation of xylan-5-fluorouracil-1-acetic acid conjugates as prodrugs for colon cancer treatment

In the present study, xylan-5-fluorouracil-1-acetic acid (Xyl-5-FUAC) conjugates as colon specific prodrugs were synthesized and evaluated by in-vitro release study. The chemical stability of the conjugates was performed in acidic (pH 1.2) and basic buffers (pH 7.4), which showed their stability in upper gastrointestinal tract. The in-vitro drug release profiles of the conjugates were studied in the presence of rats gastrointestinal contents. The results showed that the low amounts of drug 3-4% and 5-7% were released in gastric and small intestine contents respectively, while 53-61% of the drug was released in cecum and colonic contents. The cytotoxicity studies of the conjugates were also evaluated on human colorectal cancer cell line (HTC-15 and HT-29), which showed that the conjugates are more cytotoxic than the free drug. Therefore the results reveal that Xyl-5-FUAC conjugates are potential candidates for colon specific drug delivery in the treatment of colonic cancer with minimal undesirable side effects.

pH-responsive prodrug nanoparticles based on xylan-curcumin conjugate for the efficient delivery of curcumin in cancer therapy

In the present study, novel pH-responsive prodrug nanoparticles based on xylan-curcumin (xyl-cur) conjugate were developed to enhance the therapeutic efficacy of curcumin in cancer therapy. The synthesis of xyl-cur conjugate (prodrug) was confirmed by FT-IR, 1H NMR, UV-vis and fluorescence spectroscopy. The xyl-cur prodrug was subsequently self-assembled in to nanoparticles (xyl-cur prodrug NPs) in an aqueous medium with the average particle size 253 nm and the zeta potential of -18.76 mV. The xyl-cur prodrug NPs were highly pH-sensitive in nature and most of the drug was released at lower pH. The interaction of the xyl-cur prodrug NPs with blood components was tested by hemolysis study. The cytotoxic activity of the xyl-cur prodrug NPs against human colon cancer cells (HT-29, HCT-15) demonstrated that the prodrug NPs exhibits greater cytotoxic effect than curcumin. Therefore, these results reveal that xyl-cur prodrug NPs could be a promising candidate for improving the intracellular delivery of curcumin in cancer therapy.

Bioactive carbon dots lights up microtubules and destabilises cell cytoskeletal framework – A robust imaging agent with therapeutic activity

A class of bioactive, microtubule specific, self-targeted carbon dots (CDs) has been synthesised by simple one-step hydrothermal treatment with Catharanthus roseus as the precursor. Apart from excitation dependent multicolour fluorescence of as-prepared CDs, they were also attributed with an inherent affinity for microtubules of cell cytoskeletal framework. As prepared CDs in-vitro bio-labelling and live cell imaging studies in NIH 3T3 cells illustrates their tubulin specific bio-labelling potential which lights up the cell microtubule framework prominently under all filters. The ability of as-prepared CDs to simultaneously label tubulin and effectuate microtubule depolymerisation and fragmentation enables us to track its therapeutic potential on a real time basis. The cascade of events starting from cellular uptake, microtubule labelling and subsequent cytoskeletal changes (microtubule fragmentation, depolymerisation and cytoplasmic constriction) have been investigated comprehensively in this work by flow cytometer, confocal microscope, AFM microscopy (Peak Force QNM) and FE-SEM analysis. In summary, this work outlines the synthesis, characterization and application of a new class of highly fluorescent self-targeted microtubule specific CDs as a potent bioactive imaging nanotags.