| 1. |
- Shafaat, Atefeh
(författare)
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Development of Wireless Biosensors Integrated into the Radio Frequency Antenna for Chipless and Battery-less Monitoring of Biological Reactions
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Development of wireless sensors and biosensors is currently experiencing a rapid progress with a substantial focus directed toward highlighting their potential applications as non-invasive wearables, implants, and highly mobile point-of-care devices. Integration of wireless biosensors into the Internet of Things (IoT) is widely acknowledged as a technological advancement with the potential to significantly change daily life. To maximize this potential, simple integration of biosensors with wireless communication elements would be advantageous. In this regard, systems functioning in chipless, and battery-less modes outperform integrated circuit (IC) based and battery-powered wireless biosensors. Nevertheless, the accessibility of these wireless designs is still limited. In this study, we present a novel approach where incorporating silver nanoparticles(AgNPs) as a part of the radio frequency (RF) tag antenna enables the realization of simple, chipless, and battery-less wireless sensing of biological oxidation and reduction reactions. We exemplified the mechanism of operation in such systems by electronic wiring of enzymes through direct electron transfer (DET) and microorganisms through mediated electron transfer (MET) to the redox conversion of Ag/AgCl. The wiring was designed to facilitate the transformation of metallic AgNPs into AgCl (Ag → AgCl) or the conversion of AgCl particles back into metallic AgNPs (AgCl → Ag) when the enzymatic/microorganism based electron transfer reactions were present. These reactions occurring on the biosensor RF tag antenna strongly changed the impedance of the tag, which was wirelessly monitored by a radio frequency identification (RFID) reader. The functionality of the proposed setup in direct electron transfer coupling of the enzymatic reactions to the redox conversion of the Ag/AgCl was demonstrated by wireless detection of glucose in whole blood samples and hydrogen peroxide penetrated through the skin membrane using the enzymes glucose dehydrogenase(GDH) and horseradish peroxidase (HRP). Additionally, the capability of the proposed configuration in mediated electron transfer wiring of microorganisms to the Ag/AgCl electrochemistry was shown by wireless monitoring of medically relevant microbial biofilms in simulated wound fluid. Generalizing, the results of this work, for the first time, demonstrated that exploiting Ag/AgCl as a part of the tag antenna allows simple, chipless, and battery-less wireless sensing of biological oxidation and reduction reactions.
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| 2. |
- Selegård, Robert, 1934-
(författare)
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Polypeptide functionalized gold nanoparticles for bioanalytical applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Detection strategies that allow for simple, rapid, cost efficient and sensitive monitoring of proteins and their interactions with biomolecules are of great importance in drug development and diagnostics. This thesis describes the development of bioanalytical applications based on the tunable self-assembly of gold nanoparticles functionalized with a de novo designed polypeptide. Strategies for protein affinity sensing and for detection of several fundamentally important biological processes have been investigated, including Zn2+-mediated coordination between polypeptides and low molecular weight chelants and protease and phosphatase activity.A Zn2+ responsive synthetic polypeptide designed to fold into a helix-loop-helix motif and dimerize into a four-helix bundle has been used to control the stability and self-assembly of gold nanoparticles. This polypeptide has a high negative net charge at neutral pH as a consequence of its many glutamic acid residues, efficiently preventing folding and dimerization due to charge repulsion. Zn2+ coordination provides a means to trigger folding and dimerization at neutral pH. The polypeptide can be readily attached to gold nanoparticles via a cysteine residue in the loop region, retaining its folding properties and responsiveness to Zn2+. The polypeptide functionalized gold nanoparticles display excellent colloidal stability but aggregate reversibly after addition of millimolar concentrations of Zn2+. Aggregates are dense with a defined interparticle distance corresponding to the size of the four-helix bundle, resulting in a distinct red shift of the localized surface plasmon resonance band.Three completely different strategies for colorimetric biosensing have been developed, all being based on the same responsive hybrid nanomaterial. In the first strategy a synthetic receptor was co-immobilized on the gold nanoparticles together with the Zn2+ responsive polypeptide. Protein analyte binding to the receptor could be detected as this interaction sterically prevented aggregation induced by Zn2+. In the second strategy the reduction in colloidal stability caused by specific proteolytic cleavage of the immobilized polypeptide was exploited to monitor the enzymatic activity. The third strategy utilized the sensitivity of the system to small variations in Zn2+ concentration. The presence of low molecular weight chelants was found to influence the mode of aggregation, both by sequestering Zn2+ and through the formation of ternary complexes involving the polypeptides, which prevented dimerization and thus aggregation. This approach was further developed into a generic concept for phosphatase detection exploiting the different affinity of enzyme substrates and reaction products for Zn2+.The flexibility of the different detection schemes enables detection of a large number of analytes by exploiting the tunable stability of the nanoparticles and the possibilities to effectively decouple the recognition event and the nanoparticle stability modulation.
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| 3. |
- Martinsson, Erik, 1983-
(författare)
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Nanoplasmonic Sensing using Metal Nanoparticles
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In our modern society, we are surrounded by numerous sensors, constantly feeding us information about our physical environment. From small, wearable sensors that monitor our physiological status to large satellites orbiting around the earth, detecting global changes. Although, the performance of these sensors have been significantly improved during the last decades there is still a demand for faster and more reliable sensing systems with improved sensitivity and selectivity. The rapid progress in nanofabrication techniques has made a profound impact for the development of small, novel sensors that enables miniaturization and integration. A specific area where nanostructures are especially attractive is biochemical sensing, where the exceptional properties of nanomaterials can be utilized in order to detect and analyze biomolecular interactions. The focus of this thesis is to investigate plasmonic nanoparticles composed of gold or silver and optimize their performance as signal transducers in optical biosensors. Metal nanoparticles exhibit unique optical properties due to excitation of localized surface plasmons, which makes them highly sensitive probes for detecting small, local changes in their surrounding environment, for instance the binding of a biomolecule to the nanoparticle surface. This is the basic principle behind nanoplasmonic sensing based on refractometric detection, a sensing scheme that offers real-time and label-free detection of molecular interactions. This thesis shows that the sensitivity for detecting local refractive index changes is highly dependent on the geometry of the metal nanoparticles, their interaction with neighboring particles and their chemical composition and functionalization. An increased knowledge about how these parameters affects the sensitivity is essential when developing nanoplasmonic sensing devices with high performance based on metal nanoparticles.
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| 4. |
- Utterström, Johanna, 1993-
(författare)
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Design and Optimization of Membrane Active Peptides and Lipid Vesicles for Triggered Release
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Liposomes can reduce toxic side effects and improve the efficacy of drugs and several liposome-based drug formulations are approved for clinical use. The therapeutic effect is dependent on the bioavailability of the drug and a slow drug release from liposomes can reduce their efficacy. Multiple strategies have been proposed to control the release of drugs from liposomes using both external stimuli such as light, heat and ultrasound, and endogenous factors such as changes in pH or enzymatic activity. However, because of the difficulties to efficiently modulate lipid membrane permeability and the challenges to trigger drug release in the target tissue, no stimuli responsive liposomes have so far been approved. There is consequently a great need for new means to tune lipid membrane integrity for liposome cargo release to improve the development of new advanced drug delivery systems for better and safer treatment of patients. The aim of this thesis was to design and explore synthetic membrane active peptides for triggered release from liposomes and to expand the knowledge on how peptide-lipid conjugation strategies and lipid properties affect the membrane activity of the peptides. This work was based on two different de novo designed cationic and amphipathic, conjugation-dependent membrane active peptides (CKV4 and JR2KC). Both peptides fold and adopt α-helical structures upon conjugation to liposomes, triggering lipid membrane destabilization. Addition of cholesterol in the lipid membrane greatly enhanced the release efficiency of JR2KC due to a peptide-triggered lipid phase separation, resulting in domains with high local peptide concentrations. Additionally, both peptide surface concentrations and lipid net charge were found to be important factors for efficient release. However, when the zeta potential decreased below -75 mV, conjugation-independent release mechanisms were triggered. Liposome size was shown to only have minor effects on the release kinetics for both sets of peptides while a mixture of saturated and unsaturated lipids was beneficial for the peptide-triggered membrane destabilization, possibly due to increased propensity for lipid phase separation. In addition to changing lipid properties, peptide-lipid conjugation strategies proved to highly affect the release kinetics, where the Michael addition reaction between a cysteine in the peptide and maleimide-lipids was much more efficient in causing peptide-triggered membrane destabilization than strain-promoted alkyne azide cycloaddition reactions using azide-modified peptides and DBCO-functionalized lipids. However, thiols tend to oxidize under ambient conditions which complicates peptide-lipid conjugation. This was addressed by synthesizing a peptide with a cysteine modified with an enzyme labile thiol protection group. Enzymatic deprotection allowed efficient peptide-lipid conjugation, reducing the risk of peptide oxidation. To further find means to tailor peptide-lipid interactions, we explored the effect of a competing peptide heterodimerization process on lipid membrane destabilization. Addition of a charge complementary peptide to CKV4 resulted in heterodimerization and folding into a coiled coil, which inhibited its membrane activity. However, when the two peptides were synthesized as a single sequence, the membrane activity was altered, most likely due to the induced preorganization increasing membrane affinity. The results presented in this thesis provide new understandings of the complex peptide-lipid interactions that govern peptide-induced release from liposomes and will facilitate further optimization in peptide design for the future development of advanced liposome-based drug delivery systems.
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| 5. |
- Blasi Romero, Anna
(författare)
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Bioactive nanocellulose materials for the treatment of chronic wounds
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chronic wounds represent a burden for the healthcare system and significantly affect the quality of life of the patients. There is currently a lack of efficient treatments but new, improved therapeutic approaches are under development. Suggested innovative wound care therapies consist on the topical administration of bioactive compounds aimed at restoring the balance in the wound environment and promoting the healing. However, their effectiveness is limited due to the highly oxidative and proteolytic environment in the chronic wound. In the work presented in this thesis, a series of bioactive nanocellulose-based materials were developed with the aim of addressing some of the present demands in chronic wound care. Wood-derived cellulose nanofibrils (CNFs) were functionalized with selected bioactive molecules expected to endow CNFs with the ability to modulate the chronic wound environment. Different chemical approaches were explored to combine CNFs with the following biomolecules: the amino acid cysteine, the peptide oligoproline and the host defense peptide KR-12. Materials were characterized in terms of chemical structure, degree of substitution and bioactivity.The immobilization of cysteine onto CNFs (cys-CNF) provided the material with radical oxygen species (ROS) scavenging properties and the ability to inhibit protease activity, properties that were related to the presence of free thiol groups on the nanofibers. Storage conditions in an inert atmosphere or in the form of aerogel were proposed to assure the long-term activity of the cys-CNF material. Investigations on the use of the ROS-sensitive oligoproline to crosslink CNFs provided optimized protocols to maximize peptide substitution and the degree of crosslinking. The oligoproline-CNF materials were sensitive to ROS-mediated cleavage and provided a protective effect to cells exposed to oxidative conditions. Moreover, the feasibility of preparing ROS-responsive drug delivery hydrogels based on the oligoproline-CNF was demonstrated, with indications that tuning the length of the oligoproline peptide could be exploited to tailor the release rate of small proteins. CNF materials with antibacterial properties and the ability to modulate the response of pro-inflammatory macrophages were obtained by immobilizing KR-12 derivatives onto CNFs. This study highlighted the importance in the selection of the conjugation chemistry to preserve the activity of the peptide once immobilized. To conclude, this work has contributed with valuable strategies to develop bioactive CNF-based materials with the potential of paving the way for advanced solutions in the field of chronic wound care.
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| 6. |
- Jury, Michael, 1984-
(författare)
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Modular Hyaluronan-Based Hydrogels for 3D Cell Culture and Bioprinting
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three-dimensional (3D) cell culture facilitates development of biological relevant assays for drug screening and toxicity testing. Compared to conventional 2D cell culture, cells cultured in 3D can more accurately mimic human tissues and organs and thus provide ex vivo data with potentially better predictive value for cancer research, pharmacology, and toxicology, reducing the need for animal models, improving experimental reproducibility, and reducing time and costs in drug development. The most widely used options for scaffold-based 3D cell culture are, however, based on poorly defined biologically derived extracellular matrix (ECM) with limited possibilities to tailor material properties and that are difficult to combine with state-of-the art biofabrication techniques. The overall aim this thesis was to design and explore modular hyaluronan (HA) based ECM-mimicking hydrogels with tuneable physiochemical properties and biofunctionalities, for development of advanced 3D cell models and biofabrication. The thesis work is presented in five papers. In paper I, we used copper free click chemistry for both hydrogel cross-linking and functionalization with fibronectin derived peptide sequences for culture of human induced pluripotent-derived hepatocytes in a perfused microfluidic system. The tuneable and bioorthogonal cross-linking enabled both retention of high cell viabilities and fabrication of a functional liver-on-chip solution. In paper II, we combined the developed HA-based hydrogel system with homo- and heterodimerizing helix-loop-helix peptides for modulation of both cross-linking density and biofunctionalization. We further demonstrated the possibilities to use these hydrogels as bioinks for 3D bioprinting where both the molecular composition and the physical properties of the printed structures could be dynamically altered, providing new avenues for four-dimensional (4D) bioprinting. In paper III we investigated the possibilities to chemically conjugate full size recombinant human laminin-521 (LN521) in the HA-based hydrogels system using copper-free click chemistry, with the aim to enable 3D culture and 3D bioprinting of neurons. We quantified the impact of using different linkers to tether LN521 and the influence of LN-functionalization on the structural and mechanical properties of the hydrogels. We show that both differentiated and non-differentiated neuroblastoma cells and long-term self-renewing neuroepithelial stem cells (lt-NES) remained viable in the hydrogels. The hydrogels also had a protected effect on lt-NES during syringe ejection and bioprinting. In paper IV, we used HA-based hydrogels modified with peptides sequences derived from fibronectin and laminin for culture of fetal primary astrocytes (FPA). We explored both the interactions between the hydrogels and FPA and possibilities to 3D bioprint FPAs. Finally, in paper V, we developed HA-nanocellulose composite hydrogels with the aim to increase printing fidelity and enable fabrication of multi-layered bioprinted structures without the use of a support bath. In addition to HA, we used wood-fibre derived nanocellulose (NC) to increase the viscosity of the bioink during the printing process. The developed biorthogonal and modular hydrogel systems provide a large degree of flexibility that allows for encapsulation and culture of different cell types and processing using different techniques, which can contribute to further exploration of fabrication of biologically relevant tissue and disease models.
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| 7. |
- Naeimipour, Sajjad, 1987-
(författare)
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Modular Enzyme-Responsive Polysaccharide-Based Hydrogels for Biofabrication
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Engineered human tissue and disease models can decrease the cost and time of developing new drugs and treatments, facilitate personalized medicine, and eliminate the need for animal models that poorly represent the human body and are ethically problematic. However, the current conventional cell expansion methods using 2D culture flasks cannot enable the development of such complex multi-cellular 3D models. In general, hydrogels are considered promising materials that can make the biofabrication of tissue models possible. Hydrogels are highly hydrated materials comprised of either synthetic or naturally derived polymers, or a combination of both, and can form an environment mimicking the biomacromolecular network surrounding cells in the body. This network of biopolymers, known as extracellular matrix (ECM), is comprised of proteins such as collagen, laminin, fibronectin, and polysaccharides such as hyaluronan (HA), heparan, keratan, and chondroitin sulfate. The design of hydrogels representing the physical and biochemical properties of the ECM and which can be used for biofabrication is challenging but of increasing interest due to the rapid progress in the development of 3D and 4D bioprinting techniques. As the ECM properties differ between various tissues and disease conditions and change over time, a dynamic modular hydrogel system is needed to that can be optimized for each cell and tissue type. This thesis aims to develop modular enzyme-responsive polysaccharide-based hydrogels for 3D cell culture and biofabrication. The natural polysaccharides, hyaluronic acid (HA) and alginate (Alg) were used as the main backbone in the hydrogels developed in this thesis. HA was modified by conjugating bicyclo[6.1.0]non-4-yne (BCN) to the backbone to form HA-BCN-based hydrogels by a bioorthogonal strain-promoted alkyne-azide cycloaddition. The click reaction between BCN and azide groups allowed for modulating the biochemical and mechanical properties of the HA-BCN hydrogels. HA-BCN was further decorated with peptides to explore peptide folding and dimerization-mediated dynamic cross-linking and biofunctionalization. This system was further used to explore possibilities to dynamically alter the properties of 3D bioprinted structures, mimicking the biomineralization process in bone tissue. In a different study, a tumor model comprising fibroblast and breast cancer cells (MCF7) was bioprinted using HA-BCN cross-linked by matrix metalloporotease (MMP) cleavable and PEG-diazide MMP-resistant cross-linkers, demonstrating the synergistic relationship between hydrogel degradability and cancer cell growth, intensified by the presence of fibroblasts. The possibility of incorporating a conductive module into this hydrogel system was explored using the enzyme-assisted polymerization of ETE-S to form an interpenetrating conductive network inside HA-BCN hydrogel. The in situ and user-triggered polymerization of conductive ETE-S was demonstrated after 3D printing HA-BCN bioink containing ETE-S monomers into a lattice shape structure. We also demonstrated that cellulose nanofibrils (CNF) improved the printability of HA-BCN bioinks, and this hybrid bioink was used for printing self-standing cell-laden 3D structures. Besides these studies, a novel enzymatically triggered thiol-based chemistry was developed to address the unwanted oxidation of thiol-containing hydrogels and decrease the off-target thiol reactions during hydrogel synthesis and formation. Alginate containing sulfhydryl moieties, protected by an enzyme-labile Phacm group (AlgCP), was treated with penicillin G acylase and subsequently formed a disulfide cross-linked hydrogel. We studied the gelation kinetics and rheological properties of AlgCP and different modes of cross-linking by reversible disulfide bonds, a thiol-maleimide Micheale-type addition reaction, and ionic interactions between alginate and Ca2+ ions. MCF7 breast cancer cells cultured in the AlgCP hydrogels formed spheroids that could be harvested by GSH dissolution of the hydrogels. Finally, this novel chemistry enabled bioprinting of multi-material 3D structures with control over the printed structure's physiochemical properties, including the type and density of cross-linkers. Bioprinted fibroblasts formed extended morphology, and MCF7 cells formed spheroids in the bioprinted lattice structures. The hydrogel systems developed and explored in this thesis are modular and exhibit dynamic and tunable properties, and are applicable for a wide range of 3D cell culture and bioprinting applications. The hydrogels were either formed in response to the activity of an enzyme or remodeled by enzymes. Both enzyme-responsive HA-BCN and AlgCP hydrogel systems are promising bioinks for generating more elaborate and spatially defined cell-laden 3D structures whose features can be altered post-printing by cell-secreted and extrinsic reagents. These hydrogel-based toolkits can play a vital role in developing tissue and disease models that can make the drug discovery process faster, cheaper, and animal-free.
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| 8. |
- Wickham, Abeni
(författare)
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Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nature has had millions of years to perfect the structural components of the human body, but has also produced the dysfunctions that result in the cancers and diseases, which ruin that perfection. Congenital heart defects, and myocardial infarction lead to scarring that remodels heart muscle, decreasing the contractility of the heart, with profound consequences for the host. Regenerative medicine is the study of strategies to return diseased body parts to their evolutionarily optimum structure.Nature has had millions of years to perfect the structural components of the human body, but has also produced the dysfunctions that result in the cancers and diseases, which ruin that perfection. Congenital heart defects, and myocardial infarction lead to scarring that remodels heart muscle, decreasing the contractility of the heart, with profound consequences for the host. Regenerative medicine is the study of strategies to return diseased body parts to their evolutionarily optimum structure. Cells alone cannot develop into functional tissue, as they require mechanical support and chemical signals from the extracellular matrix in order to play the correct role in the body. In order to imitate the process of tissue formation optimized by nature, scaffolds are developed as the architectural support for tissue regeneration. To mimic the elasticity and strength seen in the heart muscle is one of the major scientific conundrums of our time. The development of new multifunctional materials for scaffolds is an accepted solution for repairing failing heart muscle. In this thesis I accept the notion that endogenous cardiac cells can play a major role in addressing this problem, if we can attract them to the site of defect or injury and make them proliferate. I then proceed to show how improving on a commonly used synthetic polymer was used to develop two new biomaterials.Polycaprolactone (PCL) fibers and sheets were studied for their ability to adsorb proteins based on their surface energies. We found that although the wettability of the PCL might be similar to positive controls for cell attachment, the large differences in surface energies may account for the increased serum protein adsorption and limit cell adhesion. The effect of fiber morphology was then investigated with respect to proliferation of mesenchymal stem cells and cardiac progenitor cells. PCL was also mechanically enhanced with thiophene conjugated single walled carbon nanotubes (T-CNT); where small concentrations of the T-CNT allowed for a 2.5 fold increase in the percentage of elongation, while retaining the proliferation profile of the cardiac progenitor cells. Although PCL is a well-known implant material, the ability to attract and adhere cardiac cells was limited. Therefore we sought to develop new biomaterials with fiber morphologies similar to the muscle fiber of the heart, but with surface energies similar to positive controls for cell attachment. Poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) was then explored as a ribbon fiber and compared to collagen with embryonic cardiac cells, in vitro, and then implanted into rats for in vivo long term evaluations. The cardiac cells had a preferential adhesion to the TQ1 fibers, and in vivo, the fibers attracted more blood vessels and regrew functional tissue compared to the collagen controls. TQ1 fibers had the added ability to emit light in the near infrared region, which would allow for consistent tracking of the material. Although this material offered the morphological preference for the cardiac cells, it does not degrade and nor did it offer electrical conductivity. The heart muscle is an electrically active muscle. The dead tissue that is formed in the ischemic area loses its ability to transfer the electrical signals. Hence, I have then developed collagen fibrous materials with silver nanowires to help store and inject charges that would be generated during the contraction of the heart muscle. The silver nanowires served to help carry charges whilst providing resistance to bacterial growth on the material. The collagen/silver nanowires composites were mechanically apt for the culture of embryonic cardiac cells.
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| 9. |
- Aili, Daniel, 1977-
(författare)
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Polypeptide-Based Nanoscale Materials
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-assembly has emerged as a promising technique for fabrication of novel hybrid materials and nanostructures. The work presented in this thesis has been focused on developing nanoscale materials based on synthetic de novo designed polypeptides. The polypeptides have been utilized for the assembly of gold nanoparticles, fibrous nanostructures, and for sensing applications.The 42-residue polypeptides are designed to fold into helix-loop-helix motifs and dimerize to form four-helix bundles. Folding is primarily driven by the formation of a hydrophobic core made up by the hydrophobic faces of the amphiphilic helices. The peptides have either a negative or positive net charge at neutral pH, depending on the relative abundance of Glu and Lys. Charge repulsion thus prevents homodimerization at pH 7 while promoting hetero-dimerization through the formation of stabilising salt bridges. A Cys incorporated in position 22, located in the loop region, allowed for directed, thiol-dependent, immobilization on planar gold surfaces and gold nanoparticles. The negatively charged (Glu-rich) peptide formed homodimers and folded in solution at pH < 6 or in the presence of certain metal ions, such as Zn2+. The folding properties of this peptide were retained when immobilized directly on gold, which enabled reversible assembly of gold nanoparticles resulting in aggregates with well-defined interparticle separations. Particle aggregation was found to induce folding of the immobilized peptides but folding could also be utilized to induce aggregation of the particles by exploiting the highly specific interactions involved in both homodimerization and hetero-association. The possibility to control the assembly of polypeptide-functionalized gold nanoparticles was utilized in a colorimetric protein assay. Analyte binding to immobilized ligands prevented the formation of dense particle aggregates when subjecting the particles to conditions normally causing extensive aggregation. Analyte binding could hence easily be distinguished by the naked eye. Moreover, the peptides were utilized to assemble gold nanoparticles on planar gold and silica substrates.Fibrous nanostructures were realized by linking monomers through a disulphide-bridge. The disulphide-linked peptides were found to spontaneously assemble into long and extremely thin peptide fibres as a result of a propagating association mediated by folding into four-helix bundles.
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| 10. |
- Eskilson, Olof, 1992-
(författare)
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Multifunctional Nanocellulose Composite Materials
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanoparticles (NPs) are particles with more than one dimension between 1 and 100 nm. Because of their small size, they typically display different physical and chemical properties than the corresponding bulk materials. NPs have been used in many different applications, such as in electronics, optics, catalysis, and in biomedicine. Due to their colloidal nature, NPs are often immobilized on a solid substrate, such as glass or polymer-based materials, including biopolymers. Nanocellulose is a biopolymerbased nanomaterial that can be obtained from plants or bacterial biofilms. They can be processed into thin and highly hydrated films with high mechanical strength and can serve as a versatile substrate for NPs. Bacterial cellulose (BC) is also an interesting material for generating wound dressings. The combination of NPs and BC results in soft and flexible nanocomposites (BC-NPs) that can demonstrate novel properties and improve the functionality of wound dressings. BC-NP nanocomposites have previously been obtained by impregnating BC with the reactants needed for synthesis of the NPs and allowing the reaction to proceed in situ, inside and on the surface of the BC. This strategy limits the possibilities to control NP geometry and NP concentration and make synthesis of nanocomposites with more sophisticated compositions very challenging. In addition, the synthesis conditions used can potentially have negative effects on the properties of BC. The work presented in this thesis shows the possibility to produce well-defined, tunable BC-NP nanocomposites using self-assembly under very benign conditions that enable functionalization of BC with a wide range of different types of NPs. In addition to exploring the self-assembly process and the physical properties of these new BC-NP composites, several different applications were investigated. The functionalization of BC with gold nanoparticles (AuNPs) of different sizes and geometries was demonstrated. The resulting materials were used for development of a new sensor transduction technology, exploiting the optical response upon mechanical compression to detect biomolecules. BC-AuNP nanocomposites were also developed for monitoring of protease activity of wound pathogens, for catalysis, and for fabrication of ultra-black materials with unique absorption and scattering profiles of light in the visible and near infrared spectral range. In addition, the self-assembly process could be adopted for generating BC-mesoporous silica nanoparticles (MSNs) nanocomposite wound dressings. The resulting high surface area materials could be used as carriers for pH sensitive dyes. The pH-responsive BC-MSNs demonstrated adequate biocompatibility and allowed for monitoring of wound pH and for assessment of wound status. The strategies for functionalization of BC with inorganic NPs that was developed and explored in this thesis are highly versatile and allow for fabrication of a wide range of multifunctional nanocomposite materials.
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| 11. |
- Skyttner, Camilla, 1985-
(författare)
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Peptide-Liposome Model Systems for Triggered Release
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Liposomes are widely used in drug delivery to improve drug efficacy and to reduce side effects. For liposome-encapsulated drugs to become bioavailable and provide a therapeutic effect they must be released, which typically is a slow process that primarily relies on passive diffusion, liposome rupture or endocytotic uptake. Achieving drug concentrations within the therapeutic window can thus be challenging, resulting in poor efficacy and higher risks drug resistance. Finding means to modulate lipid membrane integrity and to trigger rapid and efficient release of liposomal cargo is thus critical to improve current and future liposomal drug delivery systems. The possibilities to tailor lipid composition and surface functionalization is vital for drug delivery applications but also make liposomes attractive model systems for studies of membrane active biomolecules.The overall aim of this thesis work has been to develop new strategies for triggering and controlling changes in lipid membrane integrity and to study the interactions of membrane active peptides with model lipid membranes using both de novo designed and biologically derived synthetic amphipathic cationic peptides. Two different sets of designed peptides have been explored that can fold and heterodimerize into a coiled coil and helix-loop-helix fourhelix bundle, respectively. Conjugation of the cationic lysine rich peptides to liposomes triggered a rapid and concentration dependent release. The additions of their corresponding glutamic acid-rich complementary peptides inhibited the release of liposomal cargo. Possibilities to reduce the inhibitory effect by both proteolytic digestion of the inhibitory peptide and by means of heterodimer exchange have been investigated. Moreover, the effects of peptide size and composition and ability to fold have been studied in order to elucidate the factors that influence the membrane permeabilizing effects of the peptides.In addition, the membrane activity of a the two-peptide bacteriocin PLNC8α and PLNC8β has been explored using liposomes as a model system. PLNC8αβ are expressed by Lactobacillus plantarum and were shown to display pronounced membrane-partition folding coupling, leading to rapid release of liposome encapsulated carboxyfluorescein. PLNC8αβ also kill and suppressed growth of the gram-negative bacteria Porphyromonas gingivalis by efficiently damaging the bacterial membrane.Although membrane active peptides are highly efficient in perturbing lipid membrane integrity, possibilities to trigger release using external stimuli are also of large interest for therapeutic applications. Light-induced heating of liposome encapsulated gold nanoparticles (AuNPs) has been shown by others as a potential strategy to trigger drug release. To facilitate fabrication of thermoplasmonic liposome systems we developed a simple method for synthesis of small AuNPs inside liposomes, using the liposomes as nanoscale reaction vessels.The work presented in this thesis provides new knowledge and techniques for future development of liposome-based drug delivery systems, peptide-based therapeutics and increase our understanding of peptide-lipid interactions.
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