1,720,986 research outputs found
Gold nanoparticle uptake in synchronized cell populations and the effect on radiation sensitization
Full text linkTo overcome the challenge in radiation therapy of delivering the prescribed dose to cancer cells while sparing normal tissue, preferential introduction of high Z material to tumour cells works as a method of radiation sensitization. Gold nanoparticles (GNPs) are very useful in this respect. It has been shown that the size, shape, and surface properties of GNPs affect their cellular uptake. Manipulation of the cell cycle to arrest cells at different stages offers a unique strategy to study the molecular and structural events as the cell cycle progresses. To optimize delivery of GNPs into tumour cells and enhance the effect of radiosensitization, nanoparticle (NP) uptake in synchronized populations of MDA-MB-231 breast cancer cells was investigated.
Populations of MDA-MB-231 cells were first synchronized in S-phase using double-thymidine block, and allowed to progress through cell cycle in synchronization. Synchronized cells were incubated with 5 nm GNPs, 15 nm GNPs, 46 nm GNPs and two formulations of lipid NP encapsulated 5 nm GNPs. Uptake of NPs was visualized using hyperspectral optical imaging and quantified with inductively coupled plasma mass spectrometry (ICP-MS). Following internalization of GNPs, cells were irradiated with 6 MV photon beams from a linear accelerator, and the survival fraction and induced deoxyribonucleic acid (DNA) damage were studied.
Cell cycle analysis after a double-thymidine block showed that the cell population was well synchronized. Uptake of NPs was 1.5-2 times higher in synchronized cell population compared to the control where cells were at different stages of the cell cycle. Clonogenic studies were used to evaluate the cell survival following radiation treatment. After a dose of 2 Gy, there was a decrease in cell survival fraction in synchronized cells treated with GNPs prior to radiation treatment compared to unsynchronized cells (control) indicating GNP-mediated dose-enhancement. The protein γ-H2AX, which is recruited to sites of DNA double strand breaks, was fluorescently labeled to evaluate damage due to the radiation treatment. Our results show more DNA double strand breaks in cells treated with GNPs prior to radiation. Interaction of ionization radiation with GNPs inside of cells produce secondary electrons. These secondary electrons can interact with water molecules and produce additional free radicals. These low energy electrons and free radicals interact with important cell structures and could cause cellular damage. Cell cycle synchronization has been shown to enhance GNP/PEG/RGD uptake in MDA-MB-231 cells resulting in greater cell radiosensitization and cellular damage. Cell synchronization is therefore an additional method available that can be employed to improve GNP uptake in cells.Graduat
Modulation of nanoparticle uptake, intracellular distribution, and retention with docetaxel to enhance radiotherapy
No full textOBJECTIVE:
One of the major issues in current radiotherapy (RT) is the normal tissue toxicity. A smart combination of agents within the tumor would allow lowering the RT dose required while minimizing the damage to healthy tissue surrounding the tumor. We chose gold nanoparticles (GNPs) and docetaxel (DTX) as our choice of two radiosensitizing agents. They have a different mechanism of action which could lead to synergistic effect. Our first goal was to assess the variation in GNP uptake, distribution, and retention in the presence of DTX. Our second goal was to assess the therapeutic results of the triple combination, RT/GNPs/DTX.
METHODS:
We used HeLa and MDA-MB-231 cells for our study. Cells were incubated with GNPs (0.2nM) in the absence and presence of DTX (50nM) for 24 hrs for determination of uptake, distribution, and retention of NPs. For RT experiment, treated cells were given a 2 Gy dose of 6 MV photons using a linear accelerator.
RESULTS:
Concurrent treatment of DTX and GNPs resulted in over 85% retention of GNPs in tumor cells. DTX treatment also forced GNPs to be closer to the most important target, the nucleus, resulting in a significant decrease in cell survival with the triple combination of RT, GNPs, and DTX vs. RT plus DTX alone. Our experimental therapeutics results are supported by Monte Carlo simulations.
CONCLUSION:
The ability to not only trap GNPs at clinically feasible doses but also to retain them within the cells could lead to meaningful fractionated treatments in future combined cancer therapy. Furthermore, the suggested triple combination of RT/GNPs/DTX may allow lowering the RT dose to spare surrounding healthy tissue.
ADVANCES IN KNOWLEDGE: This is the first study to show intracellular GNP transport disruption by DTX, and its advantage in radiosensitization.Graduate2020-10-3
A Novel Synergetic Combined Modality of Nanotechnology, Chemotherapy, and Radiotherapy for the Treatment of Pancreatic Cancer
No full textPancreatic cancer is one of the deadliest types of cancer, with a five-year survival rate of less than 8%. Despite the current advances in medicine, innovative treatment options are needed. Nanotechnology offers a novel perspective to treat such deadly cancers through their incorporation into radiotherapy (RT), as radiosensitizers, and chemotherapy, as drug carriers, for the goal of having better therapeutic efficacy and reducing normal tissue toxicity. However, the interaction of nanoparticles (NPs) with major cells of the tumor microenvironment (TME) is yet to be understood. Therefore, our first goal was to shed light on the dynamics of NPs within a TME of pancreatic origin. In addition to cancer cells, normal fibroblasts (NFs) and cancer-associated fibroblasts (CAFs) were examined due to their important yet opposite roles of suppressing tumor growth and promoting tumor growth, respectively. Gold nanoparticles (GNPs) were used as promising radiosensitizers due to their biocompatibility and physical and chemical proprieties. Our in vitro 2D monocultures studies revealed that NFs take up less than 50% of GNPs compared to cancer cells, while CAFs had over 300% increase in GNPs uptake compared to cancer cells. Cancer cells, CAFs, and NFs lost ~ 25% of GNPs 24 h post-dosing. We were able to significantly enhance the uptake and retention using the radiosensitizing drug docetaxel (DTX). GNP uptake was improved by a factor of three in cancer cells and a factor of two in CAFs. Both cell lines were able to retain ~ 70% of GNPs even 72 h post-treatment with DTX.
Drawing on these encouraging findings, our second goal was to create a 2D co-culture of CAFs and cancer cells to model the interaction between cancer and stromal cells in the TME and allow for better testing of therapeutic combinations. To test the proposed co-culture model, cells were grown in co-culture with different ratios of CAFs to cancer cells. Co-cultured cells were treated with 2 Gy of radiation following GNP incubation. DNA damage and cell proliferation were examined to assess the combined effect of radiation and GNPs. Cancer cells in co-culture exhibited up to a 23% decrease in DNA double strand breaks (DSB) and up to a 35% increase in proliferation compared to monocultures. GNP/RT induced up to a 25% increase in DNA DSBs and up to a 15% decrease in proliferation compared to RT alone in both monocultured and co-cultured cells. The observed resistance in the co-culture system may be attributed to the role of CAFs in supporting cancer cells. In parallel, our third goal was to explore encapsulating the toxic DTX prodrug in lipid nanoparticles (LNPDTX-P) and how that affect GNP uptake in vitro and in vivo in NRG mice. The results show that LNPDTX-P treated tumor samples have double the amount GNPs compared to control samples in both in vitro and in vivo.
Based on the outcomes of the preceding studies, we aimed to evaluate the anti-cancer efficacy of GNPs and LNPDTX-P in combination with RT on a 3D co-culture spheroid model. GNPs/RT and RT/LNPDTX-P showed a significant reduction in the spheroid size of 7% and 33%, respectively, and an increase in DNA DSB damage of 20% for RT/GNPs. However, the combination of the two nanoparticles with RT significantly enhanced the anti-cancer efficacy resulting in a 46% decrease in spheroid size and a 39% increase in DNA DSB. The combination of GNPs and LNPDTX-P with RT showed a synergistic effect due to their radiosensitizing properties improving the therapeutic efficacy of each treatment modality alone even in the more treatment resistant co-culture spheroid model. This triple modality presents a promising approach for enhancing cancer treatment while reducing side effects, and ongoing research in this area holds great promise for improving outcomes for cancer patients.Graduate2025-01-1
An examination of the use of the chemotherapy drug doxorubicin, gold nanoparticles, and radiation in combined cancer therapy
Full text linkThe chemotherapy drug doxorubicin (DOX) is a widespread and effective treatment for many different types of cancer. However, it is known for causing significant and dangerous side effects due to high cardiotoxicity. Gold nanoparticles (GNPs) are a promising field of nanomedicine due to their stability, customizability, and radiosensitization properties as demonstrated using in vitro and mice models. They accumulate preferentially in tumours due to the enhanced permeability and retention effect. The combination of GNP mediated radiotherapy and DOX has the potential to deliver highly targeted and effective therapeutics while sparing surrounding healthy tissue.
This work used GNPs conjugated with PEG and RGD, DOX, and radiotherapy in combination to investigate possible synergistic cancer therapeutics. MDA-MB-231 cells were dosed for 48 hours with GNPs at a clinically relevant concentration of 7.5 μg/mL. DOX was dosed at the measured IC50 concentration of 144.4 nM for a 48 hour exposure. Radiation doses of 2 Gy and 5 Gy were used, as 2 Gy is commonly used for fractionated radiotherapy and recent clinical trials have also shown 5 Gy to be an effective fractionated radiation dose.
A cytotoxicity assay was conducted to determine the IC50 of DOX which was used as the dosing concentration for all other assays. Live cell images were taken to demonstrate the internalization of DOX and GNPs in the cells. To quantify if DOX affected the uptake of GNPs into the cells, a cellular uptake study was conducted. As previous research has indicated that DOX causes cell cycle arrest, a cell cycle assay was conducted. To assess the cytotoxicity and radiosensitization properties of GNPs and DOX, a cellular proliferation study and a clonogenic assay were conducted. Additionally, a DNA double strand break assay was conducted to assess the amount of DNA damage caused.
The cellular uptake study revealed that DOX caused an increase in GNP uptake, with (1.27±0.16)×10^6 GNPs per cell when treated with DOX, and (0.76±0.05)×10^6 GNPs per cell when untreated. DOX showed evidence of radiosensitization in the proliferation assay with the combination of DOX and radiation causing a (54±2)% reduction in cell growth when 2 Gy was administered, and a (69±8)% reduction in cell growth when 5 Gy was administered. However, this effect was not synergistic. In the other assays conducted, DOX caused cell cycle arrest, extensive DNA damage, and no clonogenic growth. It was concluded that DOX was inducing senescence at the given dose.
GNPs showed some radiosensitization in the proliferation assay at 2 Gy, with (24±2)% reduction in growth after 3 days in the 2 Gy GNP sampled compared to (15±2)% reduction in growth in the 2 Gy control sample. No other significant differences in growth due to GNPs were seen in the proliferation assay. The clonogenic assay showed that 2 Gy radiation caused a (67±5)% decrease and 5 Gy caused a (97.9±0.6)% decrease in clonogenic survival of cells treated with radiation only when compared to the unirradiated control. The GNP incubated sample demonstrated some radiosensitivity in the clonogenic assay as it had a (78±3)% lower surviving fraction when irradiated with 2 Gy then the unirradiated control. The GNPs also showed toxicity in the unirradiated sample, with (30±11)% lower surviving fraction than the control in the clonogenic assay. A Bliss independence test found the GNPs and 2 Gy radiation to have independent effects. There was no significant difference between the GNP and control cells in the clonogenic assay when irradiated with 5 Gy. The DNA double strand break assay showed that 2 Gy radiation caused an increase in DNA damage foci from 2.0±0.2 to 5.1±0.5 foci per cell. No significant difference in foci was seen between the control and the GNP incubated cells.
While the results from this work did not demonstrate a conclusive benefit from the combined therapy of doxorubicin, GNPs, and radiation, the system is still of interest. Future experiments could be performed using a reduced doxorubicin concentration such as the IC20, to reduce the toxicity while still causing an effect. If a synergistic effect can be observed, it could be exploited to significantly reduce normal tissue toxicity in cancer patients while still delivering a lethal dose of chemotherapy and radiotherapy to the tumour.Graduat
Three dimensional spheroids and gold nanoparticles in combined cancer therapy
Full text linkOne of the major issues in cancer radiotherapy (RT) is normal tissue toxicity.
Introduction of radiosensitizers like gold nanoparticles (GNPs) into cancer cells to
enhance the local RT dose is a promising technique that is being explored. However,
a large portion of experimentation involving GNPs has been done in simple two-dimensional (2D) monolayer models that cannot properly encapsulate the complex
heterogeneous interactions that occur in vivo. By introducing an in vitro three-dimensional (3D) model that better mimics the tumour microenvironment (TME),
we can more rapidly facilitate a quicker translation of various treatment technologies
like GNPs to the clinic. Further, clinical trials show that the chemotherapy drug
docetaxel (DTX) given in conjunction with RT can improve survival in high-risk
cancers. Addition of GNPs to this current DTX/RT protocol is expected to further
improve therapeutic benefits. Elucidation of a combined therapy of GNPs, DTX, and
RT to optimize treatment can better improve patient outcome and reduce normal
tissue toxicity by specifically targeting tumours and is completely novel research.
The work in this dissertation explores the application of GNPs to various elements
that are present in a TME. Many cell types are present in TME and contribute in
different ways to the proliferation of cancer. One of these cell lines, cancer associated
fibroblasts (CAFs), which can promote tumour growth and metastasis, was compared
to cancer epithelial cells and normal fibroblasts (FBs). Hence, we used FBs and CAFs
to evaluate the differences in GNP uptake and resulting radiation induced damage.
It was found that the CAFs had a much larger uptake of GNPs relative to the other
cells, with on average 265% more GNPs relative to cervical cancer cells while FBs
had only 7.55% the uptake of the tumour cells and 2.87% the uptake of CAFs. This
translated to increases in 53BP1-related DNA damage foci in CAFs (13.5%) and
tumour cells (9.8%) along with FBs (8.8%), compared to control with RT treatment.
This difference in DNA damage due to selective targeting of cancer associated cells
over normal cells may allow GNPs to be an effective tool in future cancer RT to battle
normal tissue toxicity while improving local RT dose to the tumour.
To expedite a quicker clinical translation, 3D tumor spheroid models were optimized and compared to 2D monolayer. The uptake of various sizes of GNPs was
tested on monolayer and spheroids to evaluate the differences between a 2D and 3D
model in similar conditions. Moreover, combined treatment of GNPs with DTX was
introduced and how they effect the uptake of the GNPs was elucidated.iv
In the 2D monolayer model, the addition of DTX induced a small increase of
uptake of GNPs of between 13% and 24%, while in the 3D spheroid model, DTX
increased uptake by between 47% and 186%. It was observed that the more complex
spheroid, which introduces an extracellular matrix, had larger uptake and penetration
of smaller GNPs (15 nm) relative to larger GNPs (50 nm). Moreover, while the
addition of DTX had a beneficial effect on the uptake of GNPs into cells, it also
synchronized the cells into a radiosensitive cell cycle phase. This translated to a larger
effect when radiation was introduced, in a combined treatment modality with GNP,
DTX, and RT. In spheroids, the addition of GNPs to the treatment regime decreased
the surviving tumour cells by 16-32% compared to samples not treated with GNPs.
Further, the addition of DTX seems to synergistically increase damage in some cancer
cell lines. This work highlights the necessity to optimize GNP treatment conditions in
a more realistic tumor-like environment. A 3D spheroid model can capture important
details which are absent from a simple 2D monolayer model.Graduat
Experimental Testing Of a 400 Kwh Steel Slag-Based Thermal Energy Storage Prototype For Industrial Waste Heat Recovery Applications
Full text linkPublisher Copyright: © 2023, Avestia Publishing. All rights reserved.There is a clear need to develop cost-effective thermal energy storage systems to improve industrial energy efficiency since great amounts of energy is lost as waste heat. In this paper, a cost-effective 400 kWh thermal energy storage prototype for waste heat recovery at high temperature is tested over different charging and discharging conditions. The technology studied is based on the use of steel slag as thermal energy storage material and air as heat transfer fluid, in a packed bed reactor of 1 m3. Since the steel slag is a byproduct of the steelmaking industry its cost is almost negligible, whilst its thermomechanical properties make it very attractive to store heat. The aim of the testing studies is to gather information regarding the heat exchange efficiency between the heat transfer fluid and the slag in different temperature levels, reproducing common industrial off-gas waste heat release. Finally, with these results a technoeconomic calculation approach is provided in the frame of a real waste heat recovery plant in the steelmaking industry, which confirms this technology as a very promising candidate for waste heat recovery solutions.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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