Comparison of the photoluminescence properties of semiconductor quantum dots and non-blinking diamond nanoparticles. Observation of the diffusion of diamond nanoparticles in living cells

Long-term observations of photoluminescence at the single-molecule level were until recently very diffcult, due to the photobleaching of organic ?uorophore molecules. Although inorganic semiconductor nanocrystals can overcome this diffculty showing very low photobleaching yield, they suffer from photoblinking. A new marker has been recently introduced, relying on diamond nanoparticles containing photoluminescent color centers. In this work we compare the photoluminescence of single quantum dots (QDs) to the one of nanodiamonds containing a single-color center. Contrary to other markers, photoluminescent nanodiamonds present a perfect photostability and no photoblinking. At saturation of their excitation, nanodiamonds photoluminescence intensity is only three times smaller than the one of QDs. Moreover, the bright and stable photoluminescence of nanodiamonds allows wide field observations of single nanoparticles motion. We demonstrate the possibility of recording the tra jectory of such single particle in culture cells

Preclinical evaluation of nanoparticle enhanced breast cancer diagnosis and radiation therapy

Triple negative breast cancer (TNBC) is an aggressive type of cancer which makes up 15-20% of all newly diagnosed cases, lacking the main target molecules for tumor specific treatment. Surgery or systemic therapy by chemotherapy are frequently used in the clinic and combined with radiation therapy to improve locoregional control in breast cancer patients after surgery. With a poor prognosis, there is a clear need to explore new treatment options for TNBC. The aim of the here presented PhD project was to evaluate the feasibility to enhance the biological effect of radiation therapy and increase tumor contrast for diagnosis by applying an in vivo microCT imaging system in combination with barium nanoparticles (BaNPs) in a pH8N8 WAP-T-NP8 mouse model for TNBC. Characterization of the BaNPs revealed strong x-ray attenuation and no toxic effects in different cancer and normal cell lines. Furthermore, irradiation of cancer cells using low energy x-rays in the keV range by a microCT resulted in a significant reduction on colony formation capability. In vitro, this low energy irradiation effect on clonogenic tumor cell survival was enhanced in the presence of BaNPs. Next, a subcutaneous lung cancer mouse model in immunodeficient mice and an orthotopic syngeneic mouse model for breast cancer was applied for further in vivo evaluation. Once the treatment plan was optimized regarding the applied x-ray doses and the frequency of irradiation, low energy radiation therapy within a classical in vivo microCT significantly reduced tumor growth or even resulted in shrinkage of the tumors without visible side effects and weight loss in comparison to untreated controls. However, the intratumoral application of BaNPs was not able to increase the irradiation effect on tumor growth kinetics. This might be in part due to inhomogeneous distribution of BaNPs within the tumor observed by microCT imaging. K-edge subtraction imaging as well as x-ray fluorescence of explanted tumor samples confirmed these findings. To localize the BaNPs in 3D to specific sites within the tumor environment and to detect morphological alterations within the tumor due to irradiation in proximity to BaNPs an ex-vivo imaging based analytic platform was established, utilizing co-registration of microCT and histology data. This imaging approach co-localized BaNPs with CD68 positive phagocytic cells and revealed a non-uniform distribution of the BaNPs within the tumor, however with no signs of locally enhanced radiation effects. Furthermore, antibody functionalized BaNPs were generated for systemic application. Analysis of biodistribution revealed that EpCAM labeled BaNPs did not reach the tumor after intra-venous administration, but accumulated in liver and spleen, demonstrated by a strong CT contrast within these organs. In summary, I showed that low energy radiation therapy by applying an in vivo microCT significantly reduced tumor volumes in comparison to untreated tumors in a syngeneic breast cancer tumor mouse model resembling TNBC. However, BaNPs while enhancing the effectiveness of irradiation on tumor cells in vitro, did not improve the irradiation effect on tumor growth in vivo.2021-07-1

Acetylcholine Receptors and Concanavalin A-Binding Sites on Cultured Xenopus Muscle Cells: Electrophoresis, Diffusion, and Aggregation

Using digitally analyzed fluorescence videomicroscopy, we have examined the behavior of acetylcholine receptors and concanavalin A binding sites in response to externally applied electric fields. The distributions of these molecules on cultured Xenopus myoballs were used to test a simple model which assumes that electrophoresis and diffusion are the only important processes involved. The model describes the distribution of concanavalin A sites quite well over a fourfold range of electric field strengths; the results suggest an average diffusion constant of ~2.3 X 10^(-9) cm^2/s. At higher electric field strengths, the asymmetry seen is substantially less than that predicted by the model. Acetylcholine receptors subjected to electric fields show distributions substantially different from those predicted on the basis of simple electrophoresis and diffusion, and evidence a marked tendency to aggregate. Our results suggest that this aggregation is due to lateral migration of surface acetylcholine receptors, and is dependent on surface interactions, rather than the rearrangement of microfilaments or microtubules. The data are consistent with a diffusion-trap mechanism of receptor aggregation, and suggest that the event triggering receptor localization is a local increase in the concentration of acetylcholine receptors, or the electrophoretic concentration of some other molecular species. These observations suggest that, whatever mechanism(s) trigger initial clustering events in vivo, the accumulation of acetylcholine receptors can be substantially enhanced by passive, diffusion-mediated aggregation

Multifunctional Nanocomposites based on Bacterial Cellulose

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to 100 nm in diameter from bacteria in the culture medium. During the biosynthesis of BNC, shape-controlled hydrogels with well-defined network structure pore diameters below 10 µm can be easily achieved. For all the above-mentioned reasons, BNC is a highly promising platform material for the fabrication of functional composites through in situ growth or adsorption of pre-synthesized nanostructures on the nanoscale cellulose fibers. In this work, we have designed and demonstrated novel strategies to realize BNC-based functional nanocomposites with applications in sensing, water purification and energy storage. We have demonstrated a BNC film-based surface enhanced Raman scattering (SERS) substrate which has 3D porous structure and ultrafine fibers with uniform and dense adsorption of plasmonic nanostructures, resulting large SERS enhancement and excellent uniformity of SERS activity. For the first time, we have demonstrated a novel, highly scalable, cost-effective and green strategy to realize functional BNC-based foams/membranes. Functional materials such as graphene oxide (GO), polydopamine (PDA) can be efficiently incorporated within BNC matrix during its growth. Owing to the intercalation of functional materials within the layered BNC matrix, the functional composites showed excellent mechanical robustness and flexibility, which is crucial for efficient, large-scale applications, either as a foam or as a membrane. Specifically, we have designed and developed a bilayered hybrid biofoam comprised of BNC and RGO and a completely biodegradable bilayered foam based on BNC and PDA for highly efficient solar steam generation, which can be a sustainable solution to alleviate global water crisis. An innovative water filtration membrane based on BNC and RGO which harvests sunlight to kill microorganisms has been developed to provide a novel anti-biofouling approach. We have also demonstrated a robust filtration membrane based on BNC loaded with GO and PdNPs, which exhibited excellent dye degradation performance for highly efficient wastewater treatment. Furthermore, the in situ fabrication approach has been extended to polymeric materials such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to realize hybrid flexible supercapacitor electrodes based on RGO, BNC and PEDOT:PSS. The fabrication strategies and materials design demonstrated in this work can be easily extended to realize various BNC-based nanocomposites with applications in water purification, energy harvesting, sensing, catalysis, and life sciences

Multifunctional Nanocomposites based on Bacterial Cellulose

Cellulose is biodegradable, renewable, and abundant in nature thus cellulose (or paper)-based products can be inexpensively produced and recycled. Among cellulosic materials, bacterial nanocellulose (BNC) draws a special research attention due to the inherent three-dimensional nanofibrous structure, excellent mechanical flexibility, high purity and well-defined surface chemistry, and cost-efficient, scalable and environment-friendly synthesis. BNC can be biosynthesized by Gluconacetobacter xylinus, which is the most characterized BNC producer among various microorganisms. BNC is composed of highly pure cellulose nanofibrils, produced from well-defined dextrose through biochemical steps and subsequent self-assembling of the secreted cellulose fibrils which has the dimension ranges from 25 to 100 nm in diameter from bacteria in the culture medium. During the biosynthesis of BNC, shape-controlled hydrogels with well-defined network structure pore diameters below 10 µm can be easily achieved. For all the above-mentioned reasons, BNC is a highly promising platform material for the fabrication of functional composites through in situ growth or adsorption of pre-synthesized nanostructures on the nanoscale cellulose fibers. In this work, we have designed and demonstrated novel strategies to realize BNC-based functional nanocomposites with applications in sensing, water purification and energy storage. We have demonstrated a BNC film-based surface enhanced Raman scattering (SERS) substrate which has 3D porous structure and ultrafine fibers with uniform and dense adsorption of plasmonic nanostructures, resulting large SERS enhancement and excellent uniformity of SERS activity. For the first time, we have demonstrated a novel, highly scalable, cost-effective and green strategy to realize functional BNC-based foams/membranes. Functional materials such as graphene oxide (GO), polydopamine (PDA) can be efficiently incorporated within BNC matrix during its growth. Owing to the intercalation of functional materials within the layered BNC matrix, the functional composites showed excellent mechanical robustness and flexibility, which is crucial for efficient, large-scale applications, either as a foam or as a membrane. Specifically, we have designed and developed a bilayered hybrid biofoam comprised of BNC and RGO and a completely biodegradable bilayered foam based on BNC and PDA for highly efficient solar steam generation, which can be a sustainable solution to alleviate global water crisis. An innovative water filtration membrane based on BNC and RGO which harvests sunlight to kill microorganisms has been developed to provide a novel anti-biofouling approach. We have also demonstrated a robust filtration membrane based on BNC loaded with GO and PdNPs, which exhibited excellent dye degradation performance for highly efficient wastewater treatment. Furthermore, the in situ fabrication approach has been extended to polymeric materials such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to realize hybrid flexible supercapacitor electrodes based on RGO, BNC and PEDOT:PSS. The fabrication strategies and materials design demonstrated in this work can be easily extended to realize various BNC-based nanocomposites with applications in water purification, energy harvesting, sensing, catalysis, and life sciences