Nebras Al-Attar

Graphene oxide intercalation into self-assembled porphyrin J-aggregates

Studies are undertaken to examine graphene oxide intercalation into self-assembled J-aggregate porphyrin structures. Fluorescence lifetime and fluorescence anisotropy imaging were applied along with scanning electron microscopy to study the structure and optical properties of a graphene oxide/TMPyP hybrid composite material. It was seen that the presence of graphene oxide alters the macroscale and nanoscale self-assembled structures of TMPyP in addition graphene oxide also alters the optical activity reducing the emission intensity and exciton recombination lifetime. Evidence exists to support a model where planer-symmetric graphene oxide and TMPyP co-operate in the formation of self-assembled macro and nanostructures forming a composite with strong graphene oxide/TMPyP interaction.

Toluidine blue O-conjugated gold nanoparticles for photodynamic therapy of cultured colon cancer

Photodynamic therapy (PDT) is an emerging technique for the treatment of cancerous and non-cancerous conditions. Gold nanoparticles (GNPs) possess unique physical and chemical properties which allow them to act as multifunctional agents in nanomedicine. GNP- photosensitizer conjugates have attracted increasing attention in drug delivery for photodynamic cancer therapy. In the present investigation, we prepared covalent conjugates of the photosensitizer Toluidine Blue O (TBO) and thiol protected GNPs. The suitability of TBO- GNPs conjugates for in vitro PDT was assayed using the SW480 Human colon adenocarcinoma cell line. Our results suggest that gold nanoparticle conjugates are an excellent vehicle for delivery of photosensitizer agents in the photodynamic therapy of cultured tumour cells.

Surface-enhanced Raman scattering for rapid hematopoietic stem cell differentiation analysis

Raman-spectroscopy-based methods, such as surface-enhanced Raman spectroscopy, are a well-evolved method to molecular fingerprint cell types. Here we demonstrate that surface-enhanced Raman spectroscopy can enable us to distinguish cell development stages of bone marrow hematopoietic stem cells towards red blood cells through the identification of specific surface-enhanced Raman spectroscopy biomarkers. The approach taken here is to allow cells to take in gold nanoparticles as Raman enhancement platforms for kinetic structural observations presented here through the view of the multidimensional parameter contribution, thereby enabling profiling of bone marrow hematopoietic stem cells acquired from proliferation (stage one), differentiation (stage two), and mature red blood cells (stage three).

Single-Molecule Nonresonant Wide-Field Surface-Enhanced Raman Scattering from Ferroelectrically Defined Au Nanoparticle Microarrays

Single-molecule detection by surface-enhanced Raman scattering (SERS) is a powerful spectroscopic technique that is of interest for the sensor development field. An important aspect of optimizing the materials used in SERS-based sensors is the ability to have a high density of “hot spots” that enhance the SERS sensitivity to the single-molecule level. Photodeposition of gold (Au) nanoparticles through electric-field-directed self-assembly on a periodically proton-exchanged lithium niobate (PPELN) substrate provides conditions to form well-ordered microscale features consisting of closely packed Au nanoparticles. The resulting Au nanoparticle microstructure arrays (microarrays) are plasmon-active and support nonresonant single-molecule SERS at ultralow concentrations (<10–9–10–13 M) with excitation power densities <1 × 10–3 W cm–2 using wide-field imaging. The microarrays offer excellent SERS reproducibility, with an intensity variation of <7.5% across the substrate. As most biomarkers and molecules do not support resonance enhancement, this work demonstrates that PPELN is a suitable template for high-sensitivity, nonresonant sensing applications.

Photo-Induced Enhanced Raman from Lithium Niobate on Insulator Template

Photoinduced enhanced Raman spectroscopy from a lithium niobate on insulator (LNOI)-silver nanoparticle template is demonstrated both by irradiating the template with 254 nm ultraviolet (UV) light before adding an analyte and before placing the substrate in the Raman system (substrate irradiation) and by irradiating the sample in the Raman system after adding the molecule (sample irradiation). The photoinduced enhancement enables up to an ∼sevenfold increase of the surface-enhanced Raman scattering signal strength of an analyte following substrate irradiation, whereas an ∼threefold enhancement above the surface-enhanced signal is obtained for sample irradiation. The photoinduced enhancement relaxes over the course of ∼10 h for a substrate irradiation duration of 150 min before returning to initial signal levels. The increase in Raman scattering intensity following UV irradiation is attributed to photoinduced charge transfer from the LNOI template to the analyte. New Raman bands are observed following UV irradiation, the appearance of which is suggestive of a photocatalytic reaction and highlight the potential of LNOI as a photoactive surface-enhanced Raman spectroscopy substrate.

Optical Properties of Porphyrin: Graphene Oxide Composites

In this work we aim to (via a non-invasive functionalization approach) tune and alter the intrinsic features of optically “transparent” graphene, by integrating water-soluble porphyrin aggregates. We explore the potential to combine porphyrin aggregates and graphene oxide to assess the advantages of such as a composite compared to the individual systems. We apply a range of optical spectroscopy methods including photo-absorption, fluorescence assess ground-state and excited state interactions. Our studies show that comparing resonant Raman scattering with optical transmission and fluorescence microscopy that the presence of influences the microscopic structures of the resulting composites.

Raman spectroscopy for intracellular localisation of meso-tetraphenylporphyrin-gold nanoparticles conjugates

This study reports on the use of surface enhanced Raman scattering (SERS) as a non-destructive tool for detection and localisation of Porphyrin-Gold nanoparticles (GNP) conjugates at the subcellular level. Conjugates of the hydrophobic photosensitizer meso-Tetraphenylporphyrin (TPP) and GNPs were synthesized. The TPP-GNPs were characterized by by ultraviolet—visible absorption spectroscopy, fluorescence spectroscopy and transmission electron microscopy. TPPGNPs with a mean diameter of 12 nm were introduced into SW480 human colon adenocarcinoma cells. Single point SERS was applied in conjunction with fluorescence microscopy to localize the exogenous materials within the cells. Our results indicate that the TPP-GNP nanomaterials are distributed within cells in the cytoplasm. Overall our results indicate that Raman spectroscopy has the potential to be a high-throughput tool to localise nanoparticles in the subcellular environment.