Liesbeth Hartsuiker

In vitro toxicity studies of polymer-coated gold nanorods

We evaluated cellular responses to polymer-treated gold nanorods, which were synthesized using the standard wet-chemistry method that utilizes hexadecyltrimethylammonium bromide (CTAB). The nanorod dispersions were coated with either polystyrene sulfonate (PSS) or polyethylene glycol (PEG). Two sizes of nanorods were tested, with optical responses peaking at 628 and 773 nm. The cells were from mammary adenocarcinoma (SKBR3), Chinese Hamster Ovary (CHO), mouse myoblast (C2C12) and Human Leukemia (HL60) cell lines. Their mitochondrial function following exposure to the nanorods were assessed using the MTS assay. We found PEGylated particles to have superior biocompatibility compared with PSS-coated nanorods, which showed substantial cytotoxicity. Electron microscopy showed no cellular uptake of PEGylated particles compared with their PSS counterparts. PEGylated gold nanorods also exhibited better dispersion stability in the presence of cell growth medium; PSS-coated rods tended to flocculate or cluster. In the case of the PSS particles, toxicity correlated with surface area across the two sizes of nanorods studied.

COHERENT ANTI-STOKES RAMAN SCATTERING MICROSCOPY TO MONITOR DRUG DISSOLUTION IN DIFFERENT ORAL PHARMACEUTICAL TABLETS

Coherent anti-Stokes Raman scattering (CARS) microscopy is used to visualize the release of a model drug (theophylline) from a lipid (tripalmitin) based tablet during dissolution. The effects of transformation and dissolution of the drug are imaged in real time. This study reveals that the manufacturing process causes significant differences in the release process: tablets prepared from powder show formation of theophylline monohydrate on the surface which prevents a controlled drug release, whereas solid lipid extrudates did not show formation of monohydrate. This visualization technique can aid future tablet design.

Designing porosity and topography of poly(1,3-trimethylene carbonate) scaffolds

Using phase separation micromolding (PSmicroM) we developed porous micro-patterned sheets from amorphous poly(1,3-trimethylene carbonate) (PTMC). The use of these PTMC sheets can be advantageous in tissue engineering applications requiring highly flexible constructs. Addition of poly(ethylene oxide) (PEO) in various amounts to PTMC casting solutions provides PTMC sheets with tailored porosity and pore sizes in the range 2-20 microm. The pore-forming effect of PEO during the phase separation process is evaluated and glucose transport measurements show that the pores are highly interconnected. Additionally, tailoring the micro-pattern design yields PTMC sheets with various surface topographies. Cell culturing experiments with C2C12 pre-myoblasts revealed that cell attachment and proliferation on these sheets is relatively high and that the micro-pattern topography induces a clearly defined cell organization.

Raman and Fluorescence Spectral Imaging of Live Breast Cancer Cells Incubated with PEGylated Gold Nanorods

The optical properties of PEGylated gold nanorods (PEG-GNR) in interaction with cells have been investigated with Raman and fluorescence microspectroscopic imaging. The emission spectra were compared with those from dispersions of GNR, which can be characterized by a broad emission bandwidth of approximately 60 nm with a band maximum around 675 nm. These properties are in good agreement with observations from various other gold substrates and (nano)particles. The emission spectra from cells incubated with PEG-GNR were dominated by Raman scattering from locations where no GNR were present. Intense fluorescence spectral lines, with peak amplitude comparable with the Raman scattering from cells, were observed from locations containing GNR. The frequency range of the fluorescence emission spectra coincided mainly with the Raman fingerprint region from 500 cm−1 to 1800 cm−1, excited by the laser emission line at 647.1 nm. No surface-enhanced Raman spectra were observed. It was furthermore observed from cluster analysis of the Raman and fluorescence hyperspectral datasets that the GNR-related integrated fluorescence emission band from an individual cell could be sub-divided in multiple bands with slightly varying band maxima. Raman difference spectra of cells with GNR minus control cells showed that the amplitude of lipid signal in cells incubated with PEG-GNR was increased. An excellent correlation was found between the increased lipid signals and locations of the nanorods. This positive correlation between Raman signals from lipids and fluorescence signals from gold nanorods supports that gold nanorods are locally accumulating in lipid vesicles within the cells.

Quantitative detection of gold nanoparticles on individual, unstained cancer cells by scanning electron microscopy

Gold nanoparticles are rapidly emerging for use in biomedical applications. Characterization of the interaction and delivery of nanoparticles to cells through microscopy is important. Scanning electron microscopes have the intrinsic resolution to visualize gold nanoparticles on cells. A novel sample preparation protocol was developed to enable imaging of cells and gold nanoparticles with a conventional below lens scanning electron microscopes. The negative influence of ‘charging’ on the quality of scanning electron microscopes’ images could be limited by deposition of biological cells on a conductive (gold) surface. The novel protocol enabled high‐resolution scanning electron microscopes’ imaging of small clusters and individual gold nanoparticles on uncoated cell surfaces. Gold nanoparticles could be counted on cancer cells with automated routines.

Effect of Metal–Liquid Interface Composition on the Adsorption of a Cyanine Dye onto Gold Nanoparticles

Synthesis of asymmetric nanoparticles, such as gold nanorods, with tunable optical properties providing metal structures with improved SERS performance is playing a critical role in expanding the use of SERS to imaging and sensing applications. However, the synthetic methods usually require surfactants or polymers as shape-directing agents. These chemicals normally remain firmly bound to the metal after the synthesis, preventing the direct adsorption of a large number of potential analytes and often hampering the chemical functionalization of the surface unless extended, and critical for the nanoparticle stability, postremoval steps were performed. For this reason, it is of great importance for the full exploitation of these nanostructures to gain a deeper insight into the dependence of the analyte-metal interaction to the metal-liquid interface composition. In this article, we investigated in detail the role played by each component of the gold nanorod (GNR) interface in the adsorption of indocyanine green (ICG) as a probe molecule. Citrate-reduced gold nanospheres were used as a model substrate since the negative citrate anions adsorbed onto the metal surface can be easily displaced by those chemicals usually involved in the GNR synthesis, allowing the GNR-like interface composition to be progressively rebuilt and modified at will on the citrate-capped nanoparticles. The obtained results provide a meticulous description of the role played by each individual component of the metal-liquid interface on the ICG interaction with the metal, illustrating how apparently minor experimental changes can dramatically modify the affinity and optical properties of the ICG probe adsorbed onto the nanoparticle.

Gold nanoparticles for tumour detection and treatment

The use of nanoparticles in biomedical applications is emerging rapidly. Recent developments have led to numerous studies of noble metal nanoparticles, down to the level of single molecule detection in living cells. The application of noble metal nanoparticles in diagnostics and treatment of early stage carcinomas is the subject of many present studies. Gold nanoparticles are particularly interesting for optical biomedical applications due to their biocompatibility and moreover, their enhanced absorption cross-sections. The latter is a result of surface plasmon resonance, which can be tuned by altering the shape of the nanoparticles enabling usage of the near infrared tissue transparent optical window. This paper presents a brief overview of the variety of shapes, size and surface chemistries of the gold nanoparticles used for cancer detection and treatment, as well as their effects in different tumour models that have recently been investigated, both in vitro and in vivo.