Helen E. Townley

Biomimetics of photonic nanostructures

Biomimetics is the extraction of good design from nature. One approach to optical biomimetics focuses on the use of conventional engineering methods to make direct analogues of the reflectors and anti-reflectors found in nature. However, recent collaborations between biologists, physicists, engineers, chemists and materials scientists have ventured beyond experiments that merely mimic what happens in nature, leading to a thriving new area of research involving biomimetics through cell culture. In this new approach, the nanoengineering efficiency of living cells is harnessed and natural organisms such as diatoms and viruses are used to make nanostructures that could have commercial applications.

Ceramides induce programmed cell death in Arabidopsis cells in a calcium-dependent manner.

Abstract While the role of C2-ceramide in the induction of programmed cell death (PCD) in animal systems has been well documented, little is known of its role in plant cells. Here we show that C2-ceramide induces PCD in Arabidopsis suspension cultures, which is preceded by the generation of a calcium transient and an increase in reactive oxygen species (ROS). Inhibition of the calcium transient prevented cell death, whereas inhibition of ROS had no effect on cell survival. These observations suggest that calcium signalling plays a role in ceramide-induced PCD but is independent of the generation of ROS.

Calmodulin as a Potential Negative Regulator of Arabidopsis COR Gene Expression

Previous studies have implicated calmodulin as a signaling component required for the cold induction of COR ( c old o n r egulated) genes in Arabidopsis ([Braam and Davis, 1990][1]; [Tahtiharju et al., 1997][2]). Here, we present data that show that overexpression of calmodulin in planta causes

Characterization and Comparison of Mesoporous Silica Particles for Optimized Drug Delivery

In this study we have investigated the suitability of a number of different mesoporous silica nanoparticle structures for carrying a drug cargo. We have fully characterized the nanoparticles in terms of their physical parameters; size, surface area, internal pore size and structure. These data are all required if we are to make an informed judgement on the suitability of the structure for drug delivery in vivo. With these parameters in mind, we investigated the loading/unloading profile of a model therapeutic into the pore structure of the nanoparticles. We demonstrate that the release can be controlled by capping the pores on the nanoparticles to achieve temporal control of the unloading. We have also examined the rate and mechanism of the degradation of the nanoparticles over an extended period of time. The eventual dissolution of the nanoparticles after cargo release is a desirable property for a drug delivery system.

Modification of the physical and optical properties of the frustule of the diatom Coscinodiscus wailesii by nickel sulfate

In this paper we demonstrate how the photonic properties of a diatom can be altered by growth with a metal pollutant. Both the optical and physical properties of the silica frustule of the diatom Coscinodiscus wailesii were affected by the presence of nickel sulfate in sea water. It was found that a sublethal concentration of the metal both significantly modified the size of the pores of the valves and quenched the intrinsic PL of the amorphous silica. Since cytoplasmic structures may be involved in determining the frustule architecture, we also present TEMs of nickel-grown diatoms and show the affected organelles. The ability to modify the properties of the frustule shows that mechanisms exist for the alteration of existing structures in nature to optimize specific characteristics for exploitation in biotechnological applications.

Effects of mesoporous silica nanoparticles upon the function of mammalian sperm in vitro

UNLABELLED Nanomaterial-mediated delivery represents a promising technique for reproductive biology with a potential to improve the safety and efficacy of existing methodologies, including experimental gene therapy and sperm-mediated gene transfer. Mesoporous silica nanoparticles (MSNPs) have been characterised as a powerful and safe delivery tool, rendering them an excellent candidate for use in reproductive research. However, their effects upon mammalian gametes with highly specialised structure and functionality remain untested. Here, we show for the first time, that spherical MSNPs with hexagonal pore symmetry, functionalised with polyethileneimine and aminopropyltriethoxysilane, and optionally loaded with two common types of cargo (nucleic acid/protein), form strong associations with boar sperm following incubation in vitro and do not exert negative effect upon the main parameters of sperm function, including motility, viability, acrosomal status and DNA fragmentation index. Our findings provide a rationale for the use of MSNPs for the transfer of investigative, diagnostic and/or therapeutic compounds into mammalian sperm. FROM THE CLINICAL EDITOR Functionalized mesoporous silica nanoparticles (MSNPs) are demonstrated as efficient agents for the transfer of investigative, diagnostic, and/or therapeutic compounds into mammalian sperm. This promising technique has the potential to improve the safety and efficacy of existing methodologies, including experimental gene therapy and sperm-mediated gene transfer.

Nanoparticle augmented radiation treatment decreases cancer cell proliferation

UNLABELLED We report significant and controlled cell death using novel x-ray-activatable titania nanoparticles (NPs) doped with lanthanides. Preferential incorporation of such materials into tumor tissue can enhance the effect of radiation therapy. Herein, the incorporation of gadolinium into the NPs is designed to optimize localized energy absorption from a conventional medical x-ray. This result is further optimized by the addition of other rare earth elements. Upon irradiation, energy is transferred to the titania crystal structure, resulting in the generation of reactive oxygen species (ROS). FROM THE CLINICAL EDITOR The authors report significant and controlled cell death using x-ray-activated titania nanoparticles doped with lanthanides as enhancers. Upon irradiation X-ray energy is transferred to the titania crystal structure, resulting in the generation of reactive oxygen species.

Functionalization of mesoporous silica nanoparticles with a cell-penetrating peptide to target mammalian sperm in vitro

AIM This study aimed to investigate the effects of actively targeting mesoporous silica nanoparticles (MSNPs) toward mammalian sperm with a cell-penetrating peptide (C105Y), with subsequent analysis of binding rates and nano-safety profiles. MATERIALS & METHODS Boar sperm were exposed in vitro to C105Y-functionalized MSNPs or free C105Y, in a series of increasing doses for up to 2 h, followed by the evaluation of sperm motility, kinematic parameters, acrosome morphology, MSNP-sperm binding and cell fluorescence levels. RESULTS C105Y-functionalized MSNPs preserved their biocompatibility with sperm, and exhibited an approximately fourfold increase in affinity toward gametes, compared with unmodified MSNPs, during the early stages of incubation. CONCLUSION Our findings support the application of MSNPs and active targeting to sperm as valuable tools for reproductive biology.

Diatom Frustules: Physical, Optical, and Biotechnological Applications

Diatoms are unicellular photosynthetic eurkaryotes within the class Bacillariophyceae whose peculiarity amongst other microalgae is a siliceous cell wall (Round et al., 1990). Traditionally, diatoms have been subdivided into two major groups based upon their symmetry: the centrales have radial symmetry, whilst the pennales have bilateral symmetry. Diatoms are found in both freshwater and marine environments, as well as in soil, and on moist surfaces. Individual diatoms vary in size from 2 nm up to several mm in size, although only a few species are larger than 200 mm.

Direct quantification of rare earth doped titania nanoparticles in individual human cells

Abstract There are many possible biomedical applications for titania nanoparticles (NPs) doped with rare earth elements (REEs), from dose enhancement and diagnostic imaging in radiotherapy, to biosensing. However, there are concerns that the NPs could disintegrate in the body thus releasing toxic REE ions to undesired locations. As a first step, we investigate how accurately the Ti/REE ratio from the NPs can be measured inside human cells. A quantitative analysis of whole, unsectioned, individual human cells was performed using proton microprobe elemental microscopy. This method is unique in being able to quantitatively analyse all the elements in an unsectioned individual cell with micron resolution, while also scanning large fields of view. We compared the Ti/REE signal inside cells to NPs that were outside the cells, non-specifically absorbed onto the polypropylene substrate. We show that the REE signal in individual cells co-localises with the titanium signal, indicating that the NPs have remained intact. Within the uncertainty of the measurement, there is no difference between the Ti/REE ratio inside and outside the cells. Interestingly, we also show that there is considerable variation in the uptake of the NPs from cell-to-cell, by a factor of more than 10. We conclude that the NPs enter the cells and remain intact. The large heterogeneity in NP concentrations from cell-to-cell should be considered if they are to be used therapeutically.