| 1. |
- Chen, Hu, et al.
(författare)
-
Detection of Matrilysin Activity Using Polypeptide Functionalized Reduced Graphene Oxide Field-Effect Transistor Sensor
- 2016
-
Ingår i: Analytical Chemistry. - : AMER CHEMICAL SOC. - 0003-2700 .- 1520-6882. ; 88:6, s. 2994-2998
-
Tidskriftsartikel (refereegranskat)abstract
- A novel approach for rapid and sensitive detection of matrilysin (MMP-7, a biomarker involved in the degradation of various macromolecules) based on a polypeptide (JR2EC) functionalized reduced graphene oxide (rGO) field effect transistor (FET) is reported. MMP-7 specifically digests negatively charged JR2EC immobilized on rGO, thereby modulating the conductance of rGO-FET. The proposed assay enabled detection of MMP-7 at clinically relevant concentrations with a limit of detection (LOD) of 10 ng/mL (400 pM), attributed to the significant reduction of the net charge of JR2EC upon digestion by MMP-7. Quantitative detection of MMP-7 in human plasma was further demonstrated with a LOD of 40 ng/mL, illustrating the potential for the proposed methodology for tumor detection and carcinoma diagnostic (e.g., lung cancer and salivary gland cancer). Additionally, excellent specificity of the proposed assay was demonstrated using matrix metallopeptidase 1 (MMP-1), a protease of the same family. With appropriate selection and modification of polypeptides, the proposed assay could be extended for detection of other enzymes with polypeptide digestion capability.
|
|
| 2. |
- Koon Lim, Seng, et al.
(författare)
-
Tuning Liposome Membrane Permeability by Competitive Peptide Dimerization and Partitioning-Folding Interactions Regulated by Proteolytic Activity
- 2016
-
Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 6:21123, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- Membrane active peptides are of large interest for development of drug delivery vehicles and therapeutics for treatment of multiple drug resistant infections. Lack of specificity can be detrimental and finding routes to tune specificity and activity of membrane active peptides is vital for improving their therapeutic efficacy and minimize harmful side effects. We describe a de novo designed membrane active peptide that partition into lipid membranes only when specifically and covalently anchored to the membrane, resulting in pore-formation. Dimerization with a complementary peptide efficiently inhibits formation of pores. The effect can be regulated by proteolytic digestion of the inhibitory peptide by the matrix metalloproteinase MMP-7, an enzyme upregulated in many malignant tumors. This system thus provides a precise and specific route for tuning the permeability of lipid membranes and a novel strategy for development of recognition based membrane active peptides and indirect enzymatically controlled release of liposomal cargo.
|
|
| 3. |
- Lee, Hung-Hsun, 1961-, et al.
(författare)
-
Mixed Self-Assembled Monolayers with Terminal Deuterated Anchors : Characterization and Probing of Model Lipid Membrane Formation
- 2018
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 122:34, s. 8201-8210
-
Tidskriftsartikel (refereegranskat)abstract
- We describe herein a series of self-assembled monolayers (SAMs) on gold designed for adjustable tethering of model lipid membrane phases. The SAMs consist of deuterated aliphatic anchors, HS(CH2)(15)CONH-(CH2CH2O)(6)CH2CONH-X, where X is either -(CD2)(7)CD3 or -(CD2)(15)CD3, dispersed in a stable matrix of( )protein-repellent molecules, HS(CH2)(15)CONHCH2CH2OH. The mixed SAMs with variable surface densities of the anchors are thoroughly characterized before and after adsorption of phospholipids by means of ellipsometry, contact angle goniometry, and infrared reflection-absorption spectroscopy (IRRAS). In all cases, the bottom portions of the mixed SAMs (i.e., the h-alkyl thiol segments of the molecules) are arranged in a highly ordered all-trans conformation stabilized by a network of lateral hydrogen bonds. The terminal portions of the anchors (the oligo(ethylene glycol) spacer and deuterated alkyl segments, respectively), however, possess less ordered conformations in the mixed composition regime. For the SAMs containing the longer anchors (-(CD2)(15)CD3), the contact angle and infrared data point toward partial phase segregation. These findings are in excellent agreement with molecular dynamics simulations by Schulze and Stein. Upon analysis in air, the IRRAS data also indicate strong interaction between the adsorbed phospholipid molecules and the d-alkyl tails of the mixed SAM constituents. In such assemblies are the alkyl tails of the phospholipids aligned perpendicularly with respect to the supporting substrate, regardless of the anchor length. We also probed the in situ formation of a tethered bilayer lipid membrane (tBLM) via fusion of small unilamellar vesicles (SUVs) on the characterized SAMs using a quartz crystal microbalance with dissipation monitoring. Our experiments show that SUVs fuse efficiently of the two mixed SAMs with and without a pre-adsorbed lipid layer. Owing to the defined molecular composition and phase behavior, our SAM platform is attractive for detailed studies of tBLM formation and cell mimetic applications.
|
|
| 4. |
- Maleshlijski, S., et al.
(författare)
-
Imaging SPR combined with stereoscopic 3D tracking to study barnacle cyprid-surface interactions
- 2016
-
Ingår i: Surface Science. - : ELSEVIER SCIENCE BV. - 0039-6028 .- 1879-2758. ; 643, s. 172-177
-
Tidskriftsartikel (refereegranskat)abstract
- Barnacle larvae (cyprids) explore surfaces to identify suitable settlement sites. This process is selective, and cyprids respond to numerous surface cues. To better understand the settlement process, it is desirable to simultaneously monitor both the surface exploration behavior and any close interactions with the surface. Stereoscopic 3D tracking of the cyprids provides quantitative access to surface exploration and pre-settlement rituals. Imaging surface plasmon resonance (SPR) reveals any interactions with the surfaces, such as surface inspection during bipedal walking and deposition of temporary adhesives. We report on a combination of both techniques to bring together information on swimming behavior in the vicinity of the interface and physical interactions of the cyprid with the surface. The technical requirements are described, and we applied the setup to cyprids of Balanus amphitrite. Initial data shows the applicability of the combined instrument to correlate exploration and touchdown events on surfaces with different chemical termination. (C) 2015 Published by Elsevier B.V.
|
|
| 5. |
- Tai, Feng-I, 1982-
(författare)
-
Surface characterization and manipulation of polyampholytic hydrogel coatings
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is dedicated to building up fundamental knowledge about polyampholytic hydrogels, which are developed in our group for anti-fouling purposes. Charge-balanced polymers, where positive and negative charges balance each other, have emerged as interesting candidates for many applications in materials science. We have prepared charge-balanced materials by forming thickness gradients of oppositely charged polyelectrolytes, and use these as model systems for a systematic investigation of the materials and their responses to environmental changes. These hydrogel gradients were sequentially grafted from substrates via surface-initiated photografting and photopolymerization (SIPGP) of cationic and anionic polyelectrolytes. At some thickness ratios, these form a charge-balanced system where the net surface charge is zero, and with certain similarity to zwitterionic systems. The surface charge of the hydrogels is the principal parameter regulating non-specific protein adsorption, and among other things, we demonstrate that the position of the fouling-resistant charge-neutral region can be manipulated upon pH changes. The chemical compositions of the hydrogel gradients were characterized by microscopic infrared spectroscopy. Optical analysis by spectroscopic ellipsometry and imaging surface plasmon resonance were used to monitor the swelling of the hydrogel films, and protein adsorption onto these in real-time. Surface forces, i.e. the interactions with the hydrogels from an intermolecular perspective, which are related mainly to electrostatic and steric forces, were probed by direct force measurement using atomic force microscopy. Force curves were used to determine the surface charge distribution over the hydrogels, and to indicate the correlation between surface charge and protein adsorption. In the later work, hydrogel gradients were patterned as arrayed spots. Their thicknesses and surface roughness provide further information about the polymer structure and provides a basis for relating ellipsometric swelling profiles to thicknesses as obtained by atomic force microscopy. Finally, it is demonstrated how charged hydrogel films can be used as spacers to tune the optimum distance between silver nanoparticles and fluorophores for metal-enhanced fluorescence (MEF). The aim of this work is to understand polyampholytic hydrogels from various perspectives: surface charges and their distribution, the polymer structure, and surface interactions. The knowledge and experience obtained contribute to the general understanding of zwitterionic materials, and to the development of anti-fouling coatings, optical sensing platforms and other applications of charge-balanced hydrogels.
|
|
| 6. |
- Vater, Svenja M., et al.
(författare)
-
Holographic microscopy provides new insights into the settlement of zoospores of the green alga Ulva linza on cationic oligopeptide surfaces
- 2015
-
Ingår i: Biofouling (Print). - : Taylor & Francis: STM, Behavioural Science and Public Health Titles. - 0892-7014 .- 1029-2454. ; 31:2, s. 229-239
-
Tidskriftsartikel (refereegranskat)abstract
- Interaction of zoospores of Ulva linza with cationic, arginine-rich oligopeptide self-assembled monolayers (SAMs) is characterized by rapid settlement. Some spores settle (ie permanently attach) in a normal manner involving the secretion of a permanent adhesive, retraction of the flagella and cell wall formation, whilst others undergo pseudosettlement whereby motile spores are trapped (attached) on the SAM surface without undergoing the normal metamorphosis into a settled spore. Holographic microscopy was used to record videos of swimming zoospores in the vicinity of surfaces with different cationic oligopeptide concentrations to provide time-resolved insights into processes associated with attachment of spores. The data reveal that spore attachment rate increases with increasing cationic peptide content. Accordingly, the decrease in swimming activity in the volume of seawater above the surface accelerated with increasing surface charge. Three-dimensional trajectories of individual swimming spores showed a hit and stick motion pattern, exclusively observed for the arginine-rich peptide SAMs, whereby spores were immediately trapped upon contact with the surface.
|
|
| 7. |
- Wickham, Abeni
(författare)
-
Multifunctional Biomimetic Scaffolds Tailored for Cardiac Regeneration
- 2015
-
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.
|
|
| 8. |
- Yandi, Wetra, et al.
(författare)
-
Antialgal activity of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes against the marine alga Ulva
- 2017
-
Ingår i: Biofouling (Print). - : TAYLOR & FRANCIS LTD. - 0892-7014 .- 1029-2454. ; 33:2, s. 169-183
-
Tidskriftsartikel (refereegranskat)abstract
- Marine biofouling has detrimental effects on the environment and economy, and current antifouling coatings research is aimed at environmentally benign, non-toxic materials. The possibility of using contact-active coatings is explored, by considering the antialgal activity of cationic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes. The antialgal activity was investigated via zoospore settlement and sporeling growth assays of the marine algae Ulva linza and U. lactuca. The assay results for PDMAEMA brushes were compared to those for anionic and neutral surfaces. It was found that only PDMAEMA could disrupt zoospores that come into contact with it, and that it also inhibits the subsequent growth of normally settled spores. Based on the spore membrane properties, and characterization of the PDMAEMA brushes over a wide pH range, it is hypothesized that the algicidal mechanisms are similar to the bactericidal mechanisms of cationic polymers, and that further development could lead to successful contact-active antialgal coatings.
|
|
| 9. |
|
|
