| 1. |
- Alves, Luis, et al.
(författare)
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New Insights on the Role of Urea on the Dissolution and Thermally-Induced Gelation of Cellulose in Aqueous Alkali
- 2018
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Ingår i: GELS. - : MDPI AG. - 2310-2861. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- The gelation of cellulose in alkali solutions is quite relevant, but still a poorly understood process. Moreover, the role of certain additives, such as urea, is not consensual among the community. Therefore, in this work, an unusual set of characterization methods for cellulose solutions, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR) and diffusion wave spectroscopy (DWS) were employed to study the role of urea on the dissolution and gelation processes of cellulose in aqueous alkali. Cryo-TEM reveals that the addition of urea generally reduces the presence of undissolved cellulose fibrils in solution. These results are consistent with PTssNMR data, which show the reduction and in some cases the absence of crystalline portions of cellulose in solution, suggesting a pronounced positive effect of the urea on the dissolution efficiency of cellulose. Both conventional mechanical macrorheology and microrheology (DWS) indicate a significant delay of gelation induced by urea, being absent until ca. 60 degrees C for a system containing 5wt % cellulose, while a system without urea gels at a lower temperature. For higher cellulose concentrations, the samples containing urea form gels even at room temperature. It is argued that since urea facilitates cellulose dissolution, the high entanglement of the cellulose chains in solution (above the critical concentration, C*) results in a strong three-dimensional network.
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| 2. |
- Melro, Elodie, et al.
(författare)
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Dissolution of kraft lignin in alkaline solutions
- 2020
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 148, s. 688-695
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Tidskriftsartikel (refereegranskat)abstract
- Lignins are among the most abundant renewable resources on the planet. However, their application is limited by the lack of efficient dissolution and extraction methodologies. In this work, a systematic and quantitative analysis of the dissolution efficiency of different alkaline-based aqueous systems (i.e. lithium hydroxide, LiOH; sodium hydroxide, NaOH; potassium hydroxide, KOH; cuprammonium hydroxide, CuAOH; tetrapropylammonium hydroxide, TPAOH and tetrabutylammonium hydroxide, TBAOH) is reported, for the first time, for kraft lignin. Phase maps were determined for all systems and lignin solubility was found to decrease in the following order: LiOH > NaOH > KOH > CuAOH > TPAOH > TBAOH, thus suggesting that the size of the cation plays an important role on its solubility. The π∗ parameter has an opposite trend to the solubility, supporting the idea that cations of smaller size favor lignin solubility. Dissolution was observed to increase exponentially above pH 9–10 being the LiOH system the most efficient. The soluble and insoluble fractions of lignin in 0.1 M NaOH were collected and analyzed by several techniques. Overall, data suggests a greater amount of simple aromatic compounds, preferentially containing sulfur, in the soluble fraction while the insoluble fraction is very similar to the native kraft lignin.
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| 3. |
- Melro, Elodie, et al.
(författare)
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Levulinic acid : A novel sustainable solvent for lignin dissolution
- 2020
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 164, s. 3454-3461
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is a natural, renewable resource with potential to be used in biomaterials. Due to its complex structure, its efficient dissolution is still challenging, which hinders its applicability at large scale. This challenge become harder considering the current need of sustainable and environmentally friendly solvents. To the best of our knowledge, this work reports for the first time the dissolution of kraft lignin in levulinic acid, a “green” solvent, and compares its efficiency with common carboxylic acids and sulfuric acid. It has been found that levulinic acid has a high capacity to dissolve kraft lignin at room temperature (40 wt% solubility), and it efficiency is not compromised when diluting the acid with water (up to 40 wt% water content). The Kamlet-Taft π⁎ parameter of the different acidic solvents was estimated and found to correlate well with their solubility performance. Lignins previously dissolved in levulinic and formic acids were selected to be regenerated and minor differences were found in thermal stability and morphological structure, when compared to native kraft lignin. However, an increase in the content of the carbonyl groups in the regenerated lignin material was observed.
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| 4. |
- Alves, Luis, et al.
(författare)
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Revisiting the dissolution of cellulose in H3PO4(aq) through cryo-TEM, PTssNMR and DWS
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose can be dissolved in concentrated acidic aqueous solvents forming extremely viscous solutions, and, in some cases, liquid crystalline phases. In this work, the concentrated phosphoric acid aqueous solvent is revisited implementing a set of advanced techniques, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR), and diffusing wave spectroscopy (DWS). Cryo-TEM images confirm that this solvent system is capable to efficiently dissolve cellulose. No cellulose particles, fibrils, or aggregates are visible. Conversely, PTssNMR revealed a dominant CP signal at 25 °C, characteristic of C-H bond reorientation with correlation time longer than 100 ns and/or order parameter above 0.5, which was ascribed to a transient gel-like network or an anisotropic liquid crystalline phase. Increasing the temperature leads to a gradual transition from CP to INEPT-dominant signal and a loss of birefringence in optical microscopy, suggesting an anisotropic-to-isotropic phase transition. Finally, an excellent agreement between optical microrheology and conventional mechanical rheometry was also obtained.
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| 5. |
- Ascic, Ervin, et al.
(författare)
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Eliciting Anti-Tumor Immunity by Reprogramming Cancer Cells to Type 1 Conventional Dendritic Cells
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- IntroductionAn important hallmark of cancer is escaping the immune system. Despite advances in immunotherapy, only a subset of patients experiences clinical benefits. It was shown that adoptive T cell or checkpoint inhibition therapy rely on the presence of conventional dendritic cells type 1 (cDC1). cDC1 excel in recruiting and priming protective CD8+ T cells through cross-presentation. However, in tumors cDC1 are often impaired in function. Recently, we demonstrated that overexpression of PU.1, IRF8 and BATF3 (PIB) imposes a cDC1 fate in fibroblasts by direct cell reprogramming. As such, we hypothesise that a similar combination of transcription factors would reprogram cancer cells into tumor-antigen presenting cells (tumor-APCs) and set in motion antigen-specific immunity.Material and Methods30 mouse tumor lines were selected to evaluate reprogramming into tumor-APCs. Reprogramming was induced by overexpression of PIB via lentiviral transduction. The phenotype was profiled by flow cytometry for cDC1 markers CD45, MHC-II, CLEC9A, XCR1 and APC markers MHC-I, CD80/86. Population mRNA-seq was applied to assess transcriptional changes. To assess cDC1 functions, cytokine secretion, cross-presentation and T cell cytotoxicity assays were performed. In vivo, ovalbumin expressing tumors were established and treated by adoptive transfer of tumor-APCs. Tumor growth and animal survival were monitored.Results and DiscussionsUpon transduction with PIB, 26 solid tumor and 4 leukemia lines initiated expression of CD45, MHC-II, at efficiencies ranging from 0.5-57.7%. Reprogramming was accompanied by CLEC9A, XCR1 and MHC-I, CD80/86 upregulation. Transcriptomic analysis of low immunogenic lines B16 and LLC, reveals that PIB overwrites the cancer transcriptome and imposes antigen presentation and cDC1 gene signatures. Importantly, tumor-APCs present endogenous antigens on MHC-I and become prone to T cell mediated killing. Functionally, reprogrammed tumor-APCs secrete inflammatory cytokines such as IL12p70 and strikingly, acquire the ability to crosspresent antigens and prime naïve CD8+ T cells. In vivo, adoptive transfer of cross-presenting tumor-APCs delays tumor growth and extends survival of animals.ConclusionThis approach combines cDC1 antigen presentation abilities with endogenous generation of tumor antigens. The induction of a cDC1 identity in tumor cells sets in motion T cell responses and makes them target for T cell mediated killing. Our study represents a pioneering contribution merging cell reprogramming with immunotherapy.
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| 6. |
- Ascic, Ervin, et al.
(författare)
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Harnessing Dendritic Cell Reprogramming to Elucidate Mechanisms of Tumor Immunity
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The presence of conventional dendritic cells type 1 (cDC1) in the tumor correlates with positive treatment outcome. The ability to cross-present neoantigens and prime protective CD8+ T-cell responses, makes cDC1s central for tumor immunity. However, in tumors cDC1 are rare and often functionally impaired. Our group reported that overexpression of the transcription factors PU.1, IRF8 and BATF3 (PIB) converts mouse and human fibroblasts into cross-presenting cDC1-like cells. We employed the minimal gene regulatory network of highly immunogenic cDC1 and restored the immunogenicity of low immunogenic lung cancer and melanoma cell lines by reprogramming into professional tumor antigen presenting cells (tumor-APCs). Here, we report that upon transduction with PIB, 23 solid syngeneic cancer lines initiate reprogramming into cDC1-like cells expressing CD45 and MHC-II at efficiencies ranging from 0.5-57.7%. Functionally, PIB overexpression endows tumor cells with the capacity to cross-present exogenous antigen and prime naïve CD8+ T-cells. Adoptive transfer of ovalbumin cross-presenting B16 tumor-APCs into established ovalbumin expressing B16 tumors (B16-OVA) elicits tumor growth control and extends animal survival. Treated animals show a systemic antigen-specific T cell response against ovalbumin and endogenous tumor-associated antigen MuLV p15E. Intratumoral injection of reprogrammed B2905 and LLC into tumors shows differential response, correlating with their cross-presentation capacity. This approach combines cDC1 antigen cross-presentation abilities with the generation of tumor antigens. The induction of a cDC1 identity in tumor cells sets in motion T cell responses in vitro and in vivo. In the future of this project, dendritic cell reprogramming will be object in a 2-cell CRISPR/Cas9 screen using induced cDC1-like tumor cells and reporter T-cells to explore mechanistically cross-presentation regulators. The generation of cross-presenting tumor-APCs will be also used to map and characterize presented and cross-presented neoantigens. Finally, dendritic cell reprogramming of tumor cells will be explored in vivo by replenishing cDC1 within the tumor microenvironment through in vivo reprogramming. Ultimately, this project will provide insight into mechanisms of cross-presentation and pave the way for the development of novel cDC1-centric therapies.
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| 7. |
- Costa, Carolina, et al.
(författare)
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Cellulose-stabilized oil-in-water emulsions : Structural features, microrheology, and stability
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 252
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose-based oil-in-water (O/W) emulsions were studied by diffusing wave spectroscopy (DWS) regarding the effect of the cellulose concentration and mixing rate on the average droplet size, microrheological features and stability. Furthermore, the microstructure of these emulsions was imaged by cryo-scanning electron microscopy (cryo-SEM). The micrographs showed that cellulose was effectively adsorbed at the oil-water interface, resembling a film-like shell that protected the oil droplets from coalescing. The non-adsorbed cellulose that was observed in the continuous aqueous medium, contributed to the enhancement of the viscosity of the medium, leading to an improvement in the stability of the overall system. Generally, the higher the cellulose concentration and mixing rate, the smaller the emulsion droplets formed, and the higher was their stability. The combination of both techniques, DWS and cryo-SEM, revealed a very appealing and robust methodology for the characterization and design of novel emulsion-based formulations.
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| 8. |
- Costa, Carolina, et al.
(författare)
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Emulsion Formation and Stabilization by Biomolecules : The Leading Role of Cellulose.
- 2019
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Emulsion stabilization by native cellulose has been mainly hampered because of its insolubility in water. Chemical modification is normally needed to obtain water-soluble cellulose derivatives. These modified celluloses have been widely used for a range of applications by the food, cosmetic, pharmaceutic, paint and construction industries. In most cases, the modified celluloses are used as rheology modifiers (thickeners) or as emulsifying agents. In the last decade, the structural features of cellulose have been revisited, with particular focus on its structural anisotropy (amphiphilicity) and the molecular interactions leading to its resistance to dissolution. The amphiphilic behavior of native cellulose is evidenced by its capacity to adsorb at the interface between oil and aqueous solvent solutions, thus being capable of stabilizing emulsions. In this overview, the fundamentals of emulsion formation and stabilization by biomolecules are briefly revisited before different aspects around the emerging role of cellulose as emulsion stabilizer are addressed in detail. Particular focus is given to systems stabilized by native cellulose, either molecularly-dissolved or not (Pickering-like effect).
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| 9. |
- Costa, Carolina, et al.
(författare)
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On the formation and stability of cellulose-based emulsions in alkaline systems : Effect of the solvent quality
- 2022
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 286
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Tidskriftsartikel (refereegranskat)abstract
- With amphiphilic properties, cellulose molecules are expected to adsorb at the O/W interface and be capable of stabilizing emulsions. The effect of solvent quality on the formation and stability of cellulose-based O/W emulsions was evaluated in different alkaline systems: NaOH, NaOH-urea and tetrabutylammonium hydroxide (TBAH). The optimal solvency conditions for cellulose adsorption at the O/W interface were found for the alkaline solvent with an intermediate polarity (NaOH-urea), which is in line with the favorable conditions for adsorption of an amphiphilic polymer. A very good solvency (in TBAH) and the interfacial activity of the cation lead to lack of stability because of low cellulose adsorption. However, to achieve long-term stability and prevent oil separation in NaOH-urea systems, further reduction in cellulose's solvency was needed, which was achieved by a change in the pH of the emulsions, inducing the regeneration of cellulose at the surface of the oil droplets (in-situ regeneration).
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| 10. |
- Ferreira, Alexandra G, et al.
(författare)
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Reprogramming Cancer Cells to Antigen-presenting Cells
- 2023
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Ingår i: Bio-protocol. - 2331-8325. ; 13:22, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells evade the immune system by downregulating antigen presentation. Although immune checkpoint inhibitors (ICI) and adoptive T-cell therapies revolutionized cancer treatment, their efficacy relies on the intrinsic immunogenicity of tumor cells and antigen presentation by dendritic cells. Here, we describe a protocol to directly reprogram murine and human cancer cells into tumor-antigen-presenting cells (tumor-APCs), using the type 1 conventional dendritic cell (cDC1) transcription factors PU.1, IRF8, and BATF3 delivered by a lentiviral vector. Tumor-APCs acquire a cDC1 cell-like phenotype, transcriptional and epigenetic programs, and function within nine days (Zimmermannova et al., 2023). Tumor-APCs express the hematopoietic marker CD45 and acquire the antigen presentation complexes MHC class I and II as well as co-stimulatory molecules required for antigen presentation to T cells, but do not express high levels of negative immune checkpoint regulators. Enriched tumor-APCs present antigens to Naïve CD8 + and CD4 + T cells, are targeted by activated cytotoxic T lymphocytes, and elicit anti-tumor responses in vivo. The tumor-APC reprogramming protocol described here provides a simple and robust method to revert tumor evasion mechanisms by increasing antigen presentation in cancer cells. This platform has the potential to prime antigen-specific T-cell expansion, which can be leveraged for developing new cancer vaccines, neoantigen discovery, and expansion of tumor-infiltrating lymphocytes. Key features • This protocol describes the generation of antigen-presenting cells from cancer cells by direct reprogramming using lineage-instructive transcription factors of conventional dendritic cells type I. • Verification of reprogramming efficiency by flow cytometry and functional assessment of tumor-APCs by antigen presentation assays.
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