Shree Ram Singh

Functionalized Gold Nanoparticles and Their Biomedical Applications

Metal nanoparticles are being extensively used in various biomedical applications due to their small size to volume ratio and extensive thermal stability. Gold nanoparticles (GNPs) are an obvious choice due to their amenability of synthesis and functionalization, less toxicity and ease of detection. The present review focuses on various methods of functionalization of GNPs and their applications in biomedical research. Functionalization facilitates targeted delivery of these nanoparticles to various cell types, bioimaging, gene delivery, drug delivery and other therapeutic and diagnostic applications. This review is an amalgamation of recent advances in the field of functionalization of gold nanoparticles and their potential applications in the field of medicine and biology.

Functionalized carbon nanotubes: biomedical applications

Carbon nanotubes (CNTs) are emerging as novel nanomaterials for various biomedical applications. CNTs can be used to deliver a variety of therapeutic agents, including biomolecules, to the target disease sites. In addition, their unparalleled optical and electrical properties make them excellent candidates for bioimaging and other biomedical applications. However, the high cytotoxicity of CNTs limits their use in humans and many biological systems. The biocompatibility and low cytotoxicity of CNTs are attributed to size, dose, duration, testing systems, and surface functionalization. The functionalization of CNTs improves their solubility and biocompatibility and alters their cellular interaction pathways, resulting in much-reduced cytotoxic effects. Functionalized CNTs are promising novel materials for a variety of biomedical applications. These potential applications are particularly enhanced by their ability to penetrate biological membranes with relatively low cytotoxicity. This review is directed towards the overview of CNTs and their functionalization for biomedical applications with minimal cytotoxicity.

Enhanced intracellular translocation and biodistribution of gold nanoparticles functionalized with a cell-penetrating peptide (VG-21) from vesicular stomatitis virus.

Reduced toxicity and ease of modification make gold nanoparticles (GNPs) suitable for targeted delivery, bioimaging and theranostics by conjugating cell-penetrating peptides (CPPs). This study presents the biodistribution and enhanced intracellular uptake of GNPs functionalized with VG-21, a CPP derived from vesicular stomatitis virus glycoprotein (G). Cell penetrating efficiency of VG-21 was demonstrated using CellPPD web server, conjugated to GNPs and were characterized using, UV-visible and FTIR spectroscopy, transmission electron microscopy, dynamic light scattering and zeta potential. Uptake of VG-21 functionalized GNPs (fGNPs) was tested in eukaryotic cell lines, HEp-2, HeLa, Vero and Cos-7, using flow cytometry, fluorescence and transmission electron microscopy (TEM), and inductively coupled plasmon optical emission spectroscopy (ICP-OES). The effects of nanoparticles on stress and toxicity related genes were studied in HEp-2 cells. Cytokine response to fGNPs was studied in vitro and in vivo. Biodistribution of nanoparticles was studied in BALB/c mice using TEM and ICP-OES. VG-21, GNPs and fGNPs had little to no effect on cell viability. Upon exposure to fGNPs, HEp-2 cells revealed minimal down regulation of stress response genes. fGNPs displayed higher uptake than GNPs in all cell lines with highest internalization by HEp-2, HeLa and Cos-7 cells, in endocytotic vesicles and nuclei. Cytokine ELISA showed that mouse J774 cells exposed to fGNPs produced less IL-6 than did GNP-treated macrophage cells, whereas TNF-α levels were low in both treatment groups. Biodistribution studies in BALB/c mice revealed higher accumulation of fGNPs than GNPs in the liver and spleen. Histopathological analyses showed that fGNP-treated mice accumulated 35 ng/mg tissue and 20 ng/mg tissue gold in spleen and liver respectively, without any adverse effects. Likewise, serum cytokines were low in both GNP- and fGNP-treated mice. Thus, VG-21-conjugated GNPs have enhanced cellular internalization and are suitable for various biomedical applications as nano-conjugates.

JAK-STAT Is Restrained by Notch to Control Cell Proliferation of the Drosophila Intestinal Stem Cells

The Drosophila midgut epithelium undergoes continuous regeneration that is sustained by multipotent intestinal stem cells (ISCs) underneath. Notch signaling has dual functions to control ISC behavior: it slows down the ISC proliferation and drives the activated ISCs into different differentiation pathways at a dose‐dependent manner. Here we identified a molecular mechanism to unite these two contradictory functions. We found JAK–STAT signaling controls ISC proliferation and this ability is negatively regulated by Notch at least through a transcriptional control of the JAK–STAT signaling ligand, unpaired (upd). This study provides insight into how stem cells, under steady conditions, balance the processes of proliferation and differentiation to maintain the stable cellular composition of a healthy tissue. J. Cell. Biochem. 109: 992–999, 2010.

Synthesis of Ag/CNT hybrid nanoparticles and fabrication of their Nylon-6 polymer nanocomposite fibers for antimicrobial applications

Ag-coated CNTs hybrid nanoparticles (Ag/CNTs) were prepared by ultrasonic irradiation of dimethylformamide (DMF) and silver (I) acetate precursors in the presence of CNTs. The morphology of Ag/CNTs was characterized using x-ray diffraction and transmission electron microscopy (TEM) techniques. The Nylon-6 powder and 1 wt% Ag/CNTs mixture was dispersed uniformly using a noncontact spinning technique. The dried mixture was melted in a single screw extrusion machine and then extruded through an orifice. Extruded filaments were later stretched and stabilized by sequentially passing them through a set of tension adjusters and a secondary heater. The Nylon-6/Ag/CNT hybrid polymer nanocomposite (HPNC) fibers, which were of approximately 80 microm size, were tested for their tensile properties. The failure stress and modulus of the extruded HPNC fibers (doped with 1% Ag/CNTs) was about 72.19 % and 342.62% higher than the neat extruded Nylon-6 fiber, respectively. DSC results indicated an increase in the thermal stability and crystallization for HPNC fibers. The antibacterial activity of the Ag-coated CNTs, commercial Ag, neat Nylon-6 and plain CNTs were evaluated. Ag-coated CNTs at 25 microg demonstrated good antimicrobial activity against four common bacterial pathogens as tested by the Kirby-Bauer assay. The mean diameters of the zones of inhibition were 27.9 +/- 6.72 mm, 19.4 +/- 3.64 mm, 21.9 +/- 4.33 mm, and 24.1 +/- 4.14 mm, respectively, for Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Salmonella enterica serovar Typhimurium. By comparison, those obtained using the broad spectrum antibiotic amoxicillin-clavulanic acid were 37.7 +/- 2.13 mm, 28.6 +/- 4.27 mm, 22.6 +/- 1.27 mm, and 27.0 +/- 1.41 mm, respectively, for the same strains. The zones of inhibition obtained for Nylon-6 Ag-coated CNT powder at 25 microg were also high, ranging from 15.2 to 25.3 mm in contrast to commercial silver or neat Nylon-6, which did not inhibit the bacterial strains tested. Further, the Nylon-6 nanocomposite fibers infused with Ag/CNTs inhibited bacterial growth by 11-20%. Our results suggest that nylon nanocomposite fibers infused with Ag-coated CNTs have significant antimicrobial activity.

Interleukin-10 Anti-Inflammatory Response to Borrelia burgdorferi, the Agent of Lyme Disease: a Possible Role for Suppressors of Cytokine Signaling 1 and 3

ABSTRACT It has been established that interleukin-10 (IL-10) inhibits inflammatory cytokines produced by macrophages in response to Borrelia burgdorferi or its lipoproteins. The mechanism by which IL-10 exerts this anti-inflammatory effect is still unknown. Recent findings indicate that suppressors of cytokine signaling (SOCS) proteins are induced by cytokines and Toll-like receptor (TLR)-mediated stimuli, and in turn they can down-regulate cytokine and TLR signaling in macrophages. Because it is known that SOCS are induced by IL-10 and that B. burgdorferi and its lipoproteins most likely interact via TLR2 or the heterodimers TLR2/1 and/or TLR2/6, we hypothesized that SOCS are induced by IL-10 and B. burgdorferi and its lipoproteins in macrophages and that SOCS may mediate the inhibition by IL-10 of concomitantly elicited cytokines. We report here that mouse J774 macrophages incubated with IL-10 and added B. burgdorferi spirochetes (freeze-thawed, live, or sonicated) or lipidated outer surface protein A (L-OspA) augmented their SOCS1/SOCS3 mRNA and protein expression, with SOCS3 being more abundant. Pam3Cys, a synthetic lipopeptide, also induced SOCS1/SOCS3 expression under these conditions, but unlipidated OspA was ineffective. Neither endogenous IL-10 nor the translation inhibitor cycloheximide blocked SOCS1/SOCS3 induction by B. burgdorferi and its lipoproteins, indicating that the expression of other genes is not required. This temporally correlated with the IL-10-mediated inhibition of the inflammatory cytokines IL-1β, IL-6, IL-12p40, IL-18, and tumor necrosis factor α. Our data are evidence to suggest that expression of SOCS is part of the mechanism of IL-10-mediated inhibition of inflammatory cytokines elicited by B. burgdorferi and its lipoproteins.

Competitiveness for the niche and mutual dependence of the germline and somatic stem cells in the Drosophila testis are regulated by the JAK/STAT signaling

In many tissues, two or more types of stem cells share a niche, and how the stem cells coordinate their self‐renewal and differentiation is poorly understood. In the Drosophila testis, germ line stem cells (GSCs) and somatic cyst progenitor cells (CPCs) contact each other and share a niche (the hub). The hub expresses a growth factor unpaired (Upd) that activates the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in GSCs to regulate the stem cell self‐renewal. Here, we demonstrate that the JAK/STAT signaling also regulates CPCs self‐renewal. We also show that a negative regulator, the suppressor of cytokine signaling 36E (SOCS36E), suppresses JAK/STAT signaling in somatic cells, preventing them from out‐competing the GSCs. Furthermore, through selectively manipulating the JAK/STAT signaling level in either CPCs or GSCs, we demonstrate that the somatic JAK/STAT signaling is essential for self‐renewal and maintenance of both CPCs and GSCs. These data suggest that a single JAK/STAT signal from the niche orchestrate the competitive and dependent co‐existence of GSCs and CPCs in the Drosophila testis niche. J. Cell. Physiol. 223: 500–510, 2010.

Spermatogonial stem cells, infertility and testicular cancer

•  Introduction •  Spermatogonial stem cells ‐  Regulation of SSC maintenance and differentiation ‐  SSC culture, transplantation and plasticity •  SSC in infertility •  SSC in testicular germ cell tumours •  Conclusions

Gastric cancer stem cells: A novel therapeutic target

Gastric cancer remains one of the leading causes of global cancer mortality. Multipotent gastric stem cells have been identified in both mouse and human stomachs, and they play an essential role in the self-renewal and homeostasis of gastric mucosa. There are several environmental and genetic factors known to promote gastric cancer. In recent years, numerous in vitro and in vivo studies suggest that gastric cancer may originate from normal stem cells or bone marrow-derived mesenchymal cells, and that gastric tumors contain cancer stem cells. Cancer stem cells are believed to share a common microenvironment with normal niche, which play an important role in gastric cancer and tumor growth. This mini-review presents a brief overview of the recent developments in gastric cancer stem cell research. The knowledge gained by studying cancer stem cells in gastric mucosa will support the development of novel therapeutic strategies for gastric cancer.

Hypoxia and hypoxia inducible factors in tumor metabolism

Because of the abnormal vasculature, most growing solid tumors contain regions that experience either acute or chronic hypoxia. However, tumor cells can maintain a high glycolytic rate even when there is enough oxygen supply. Hypoxia-inducible factors (HIFs) play crucial role in the response of tumor cells to this distinct microenvironment by shifting energy production from mitochondria towards glycolysis. In this review, we focus on the metabolism of tumor cell survival in hypoxic microenvironments. Furthermore, we also emphasize the mechanisms by which hypoxia and HIFs regulate tumor metabolism.