Love Sarin

Mercury Vapor Release from Broken Compact Fluorescent Lamps and In Situ Capture by New Nanomaterial Sorbents

The projected increase in the use of compact fluorescent lamps (CFLs) motivates the development of methods to manage consumer exposure to mercury and its environmental release at the end of lamp life. This work characterizes the time-resolved release of mercury vapor from broken CFLs and from underlying substrates after removal of glass fragments to simulate cleanup. In new lamps, mercury vapor is released gradually in amounts that reach 1.3 mg or 30% of the total lamp inventory after four days. Similar time profiles but smaller amounts are released from spent lamps or from underlying substrates. Nanoscale formulations of S, Se, Cu, Ni, Zn, Ag, and WS2 are evaluated for capture of Hg vapor under these conditions and compared to conventional microscale formulations. Adsorption capacities range over 7 orders of magnitude, from 0.005 (Zn micropowder) to 188 000 μg/g (unstabilized nano-Se), depending on sorbent chemistry and particle size. Nanosynthesis offers clear advantages for most sorbent chemistries. Unstabilized nano-selenium in two forms (dry powder and impregnated cloth) was successfully used in a proof-of-principle test for the in situ, real-time suppression of Hg vapor escape following CFL fracture.

Opportunities for nanotechnology-enabled bioactive bone implants

Until recently, traditional orthopedic implant materials termed “bioactive” have been engineered to actively promote integration with living bone. We propose to look beyond this traditional form of bioactivity (specifically for orthopedics, in which bioactivity refers to osseointegration), and introduce the use of nanoscale surface features, fabricated using various nanotechnology tools, to provide extended functionality to implants and thus create a new class of “smarter” bioactive implant materials.

Differential effects of nanoselenium doping on healthy and cancerous osteoblasts in coculture on titanium

In the present study, selenium (Se) nanoclusters were grown through heterogeneous nucleation on titanium (Ti) surfaces, a common orthopedic implant material. Normal healthy osteoblasts (bone-forming cells) and cancerous osteoblasts (osteosarcoma) were cultured on the Se-doped surfaces having three different coating densities. For the first time, it is shown that substrates with Se nanoclusters promote normal osteoblast proliferation and inhibit cancerous osteoblast growth in both separate (mono-culture) and coculture experiment. This study suggests that Se surface nanoclusters can be properly engineered to inhibit bone cancer growth while simultaneously promoting the growth of normal bone tissue.

Selenium‐Carbon Bifunctional Nanoparticles for the Treatment of Malignant Mesothelioma

Malignant mesothelioma (MM) is an aggressive form of cancer that arises in the lining of the peritoneal, pleural or pericardial cavities. It has a long latency period, and the development of this rare cancer is typically associated with asbestos exposure. Mesothelioma may also be a concern for carbon nanotubes (CNTs), which are under development for biomedical applications[1-3] but have been recently shown to produce asbestos-like pathogenic behavior in mice, suggesting their potential to induce mesothelioma upon chronic exposure.[4-6] The diffuse nature of the tumors makes their surgical removal difficult, and they are resistant to conventional chemotherapy.[7,8] As an alternative strategy, non-conventional approaches involving new chemical agents, and targeting methods minimizing side effects are needed. Recently it has been shown that selenium, in the form of selenite and selenocysteine, can selectively inhibit growth and induce apoptotic cell death in MM cells compared to normal mesothelial cells,[9] i.e. exhibits differential toxicity. Selenium is believed to play a role in cancer prevention,[10,11] and selenium deficiency has been linked with increased cancer incidence.[11-13] The fundamental mechanisms of selenium chemo-prevention are not fully understood. At doses marginally higher than the essential dose (Recommended Daily Allowance = 55 μg/day, No Adverse Effect Level = 800 μg/day), selenium can cause toxicity.[14] The combination of the administered dose and the chemical form co-determine selenium’s activity as toxic or carcinostatic.[10,11] For example, the selenoenzyme glutathione peroxidase can protect cells from oxidative damage[15,16] and the seleno-enzymes, glutathione S-transferases, can repair damaged DNA and prevent mutation.[16] Other forms of selenium, however, can produce reactive oxygen species[10] leading to oxidative stress and cell death. In recent years, elemental nano-selenium (nSe) has gained special attention due to its therapeutic properties.[17,18] As a major advantage over other selenium forms, elemental (zero-valent) nanoparticles are a high-Se-density formulation with the potential for local delivery of high doses into cancer cells. To achieve this in practice requires a nSe formulation that is rapidly internalized by the target cell and is sufficiently stable in the extracellular fluid to reach the target cell intact. Here we synthesize two competing formulations of nano-selenium and evaluate their relative effectiveness for high-dose intracellular delivery. We show that a novel selenium-carbon composite nanostructure (CNPnSe) is highly effective in inducing death in malignant mesothelial cells in vitro and shows promise for the development of targeted therapy for malignant mesothelioma.[12]

Titanium surfaces with adherent selenium nanoclusters as a novel anticancer orthopedic material.

Current orthopedic implants have several problems that include poor osseointegration for extended periods of time, stress shielding and wear debris-associated bone cell death. In addition, numerous patients receive orthopedic implants as a result of bone cancer resection, yet current orthopedic materials were not designed to prevent either the occurrence or reoccurrence of cancer. The objective of this in vitro study was to create a new biomaterial which can both restore bone and prevent cancer growth at the implant-tissue interface. Elemental selenium was chosen as the biologically active agent in this study because of its known chemopreventive and chemotherapeutic properties. It was found that when selenite salts were reduced by glutathione in the presence of an immersed titanium substrate, elemental selenium nucleated and grew into adherent, hemispherical nanoclusters that formed a nanostructured composite surface. Three types of surfaces with different selenium surface densities on titanium were fabricated and confirmed by SEM images, AFM, and XPS profiles. Compared to conventional untreated titanium, a high-density selenium-doped surface inhibited cancerous bone cell proliferation while promoting healthy bone cell functions (including adhesion, proliferation, alkaline phosphatase activity and calcium deposition). These findings showed for the first time the potential of selenium nanoclusters as a chemopreventive titanium orthopedic material coating that can also promote healthy bone cell functions.

Novel Anti-Cancer, Anti-Bacterial Coatings for Biomaterial Applications: Selenium Nanoclusters

Two common problems with implantation after cancerous tumor resection are cancer recurrence and bacteria infection at the implant site. Tumor resection surgery sometimes can not remove all the cancerous cells, thus, cancer can return after implantation. In addition, bacteria infection is one of the leading causes of implant failure. Therefore, it is desirable to have anti-cancer and anti-bacterial molecules which both rapidly (for anti-infection purposes) and continuously (for anti-cancer purposes) are available at the implant site following implantation. Therefore, the objective of the present in vitro study was to create a multi-functional coating for anti-cancer and anti-bacterial orthopedic implant applications. Elemental selenium was chosen as the biologically active agent in this effort because of its known chemopreventive and anti-bacterial properties. To achieve that objective, titanium (Ti), a conventional orthopedic implant material was coated with selenium (Se) nanoclusters. Different coating densities were achieved by varying Se concentration in the reaction mixture. Titanium substrates coated with Se nanoclusters were shown to enhance healthy osteoblast (bone-forming cell) and inhibit cancerous osteoblast proliferation in co-culture experiments. Functions of S. epidermidis (one of the leading bacteria that infect implants) were inhibited on Ti coated with Se-nanoclusters compared to uncoated materials. Thus, this study provided for the first time a coating material (selenium nanoclusters) to the biomaterials’ community to promote healthy bone cells’ functions, inhibit cancer growth and prevent bacteria infection.

Selenium Nanocluster Coatings: Transforming Current Orthopedic Materials into Inhibiting Bone Cancer

Selenium (Se) nanoclusters were coated on three different orthopedic materials: Titanium, stainless steel and ultra high molecular weight polyethylene (UHMWPE). There different coating densities were achieved on each type of substrate. The uncoated and coated Ti and SS substrates were then used in experiments with either normal healthy osteoblasts (bone-forming cells) or cancerous osteoblasts (osteosarcoma) or a combination of both. For the first time, it was shown that the substrates coated with Se nanoclusters promoted (or at least maintained) normal osteoblast proliferation and inhibited cancerous osteoblast growth in both separate culture experiments and co-culture experiments. Thus, this study introduced to the orthopedic cancer community for the first time a coating material (Se) which may inhibit bone cancer growth and promote normal bone growth.

Selenium nanocluster coatings for anti-cancer orthopedic applications

There are currently no orthopedic materials which are made to prevent either the occurrence or reoccurrence of cancer. Due to the above, the objective of this study was to create a new biomaterial which can both restore bone and, at the same time, prevent cancer growth at the implant interface. In the present study, three types of surfaces with different surface densities were prepared. Competitive cell co-culture studies showed promoted growth of healthy bone cells and inhibited growth of cancerous cells when they were co-seeded on high dose selenium (Se) coated titanium (Ti) substrates. Thus, this study provided for the first time a material to the orthopedic community which may inhibit bone cancer growth and promote healthy bone growth.

Transforming Orthopedic Biomaterials Into Bone Cancer Inhibiting Implants: The Role of Selenium Nanoclusters

Current orthopedic implants have numerous problems that include poor osseointegration, stress shielding and wear debris-associated bone cell death. In addition, numerous patients receive orthopedic implants as a result of bone cancer resection, yet none of the current orthopedic materials are designed to prevent either the occurrence or reoccurrence of cancer. The objective of this study was to transform a traditional orthopedic material into an implant that can both restore bone and prevent bone cancer growth at the implant-tissue interface. Elemental selenium was chosen as the biologically active agent in this material because of its known chemopreventive and chemotherapeutic properties. It was found that when selenite salts were reduced by glutathione in the presence of an immersed substrate (titanium (Ti), stainless steel (SS) or ultra high molecular weigh polyethylene (UHMWPE)), elemental selenium nucleated and grew into adherent, hemispherical nanoclusters. For each type of substrate (Ti, SS and UHMWPE), three types of surfaces with different selenium surface densities were fabricated. The zero oxidation state of selenium was confirmed on Ti substrates by XPS profiles. Compared to uncoated Ti and SS substrates, the high-density selenium-coated surfaces inhibited cancerous bone cell functions while promoting healthy bone cell functions. Very little selenium was also found to release (about 250ppb) into the cell culture media after 3 days of immersion. These findings showed for the first time the potential of using selenium nanoclusters as a coating to transform a traditional orthopedic material into a bone cancer inhibiting implant.