Kris Janssen

Kris Janssen
KU Leuven | ku leuven · Department of Chemistry

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63
Publications
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2,756
Citations

Publications

Publications (63)
Article
Full-text available
Four years after its first report, expansion microscopy (ExM) is now being routinely applied in laboratories worldwide to achieve super-resolution imaging on conventional fluorescence microscopes. By chemically anchoring all molecules of interest to the polymer meshwork of an expandable hydrogel, their physical distance is increased by a factor of...
Article
Full-text available
The high-temperature all-inorganic CsPbI 3 perovskite black phase is metastable relative to its yellow non-perovskite phase, at room temperature. Since only the black phase is optically active, this represents an impediment for the use of CsPbI 3 in optoelectronic devices. We report the use of substrate clamping and biaxial strain to render stable,...
Article
Full-text available
Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray sca...
Article
Full-text available
The methyltransferase enzymes can be applied to deliver a range of modifications to pre-determined sites on large DNA molecules with exceptional specificity and efficiency. To date, however, a limited number of modifications have been delivered in this way because of the complex chemical synthesis that is needed to produce a cofactor analogue carry...
Article
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The impressive optoelectronic performance and low production cost of metal halide perovskites have inspired applications well beyond efficient so-lar cells. Herein, we widen the materials engineer-ing options available for the efficient and selective photocatalytic oxidation of benzylic alcohols - an industrially significant reaction - using forma-...
Article
Organic-inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challe...
Article
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Ever since the inception of light microscopy, the laws of physics have seemingly thwarted every attempt to visualize the processes of life at its most fundamental, sub- cellular, level. The diffraction limit has restricted our view to length scales well above 250 nm and in doing so, severely compromised our ability to gain true insights into many b...
Article
A Highly reproducible and controllable deposition procedure for gold nanostructures on a titanium dioxide (TiO2) surface using femtosecond laser light is demonstrated. This is realized by precise focusing onto the TiO2 surface in the presence of pure gold ion solution. The deposition is demonstrated both in dot array and line structures. Thanks to...
Article
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The performance of zeolites as solid acid catalysts is strongly influenced by the accessibility of active sites. However, synthetic zeolites typically grow as complex aggregates of small nanocrystallites rather than perfect single crystals. The structural complexity must therefore play a decisive role in zeolite catalyst applicability. Traditional...
Article
The development of novel molecular sieves opens opportunities in the development of more sensitive analytical devices. In this paper, metal organic frameworks (MOFs), specifically ZIF-8 and ZIF-93, are grown on fiber optic based surface plasmon resonance (FO-SPR) sensors. FO-SPR has enabled sensitive sensing capabilities in biomedical settings and...
Article
Photocatalytic reactions occur at the crystal-solution interface, hence specific crystal facet expression and surface defects can play an important role. Here, we investigate the structure related photoreduction at zinc oxide (ZnO) microparticles, via integrated light- and electron microscopy in combination with silver metal photodeposition. This e...
Article
Methyltransferases (MTases) compose a large family of enzymes which have the ability to methylate a diverse set of targets, ranging from the three major biopolymers DNA, RNA and protein to small molecules. Most of these MTases use the cofactor S-Adenosyl-L-Methionine (AdoMet) as their methyl source. Given the important biological role of methylatio...
Article
Methyltransferasen (MTasen) bilden eine große Familie von Enzymen, die vielfältige Zielstrukturen methylieren, von DNA, RNA und Proteinen bis zu niedermolekularen Verbindungen. Die meisten MTasen nutzen S-Adenosyl-l-methionin (AdoMet) als Methylquelle. In den letzten Jahren wurde intensiv an der Entwicklung von AdoMet-Analoga gearbeitet, mit dem Zi...
Article
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Photoluminescence (PL) of organometal halide perovskite materials reflects the charge dynamics inside of the material and thus contains important information for understanding the electro-optical properties of the material. Interpretation of PL blinking of methylammonium lead iodide (MAPbI3) nanostructures observed on polycrystalline samples remain...
Article
An integrated optical-electron microscope is presented that enables the in situ study of dynamic processes on photoactive materials. Here, the deposition of metallic silver nanostructures at ZnO photocatalyst particles is monitored in real time under ambient conditions by means of scanning electron microscopy. Zinc oxide crystals are immobilized on...
Article
Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monit...
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Supported metal nanoparticle catalysts are commonly obtained through deposition of metal precursors onto the support using incipient wetness impregnation. Typically, empirical relations between metal nanoparticle structure and catalytic performance are inferred from ensemble averaged data in combination with high-resolution electron microscopy. Thi...
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Spatial restrictions around catalytic sites, provided by molecular-sized micropores, are beneficial to reaction selectivity but also inherently limit diffusion. The molecular transport can be enhanced by introducing meso- and macropores. However, the impact of this extraframework porosity on the local nanoscale reactivity is relatively unexplored....
Article
We report an investigation on the effect of stabilization agents and surface curvatures on oxidative etching of three classes of anisotropically shaped gold nanoparticles namely, rods, bipyramids and prisms. In particular, the dual role of the commonly used stabilizing agent CTABr in the etching process is explored, showing how it acts both as a so...
Conference Paper
Detection of allergens and micro bacteria on a fiber optic SPR sensor is performed by means of an oligonucleotide bio-recognition surface. In this work, the DNA surface is optimized by mixing with PEG monolayers to suppress unspecific and enhance specific detection. Furthermore, due to the surface characteristic of DNA functionalized gold nanoparti...
Article
Full-text available
Detection of single nucleotide polymorphisms (SNPs) is a crucial challenge in the development of a novel generation of diagnostic tools. Accurate detection of SNPs can prove elusive, as the impact of a single variable nucleotide on the properties of a target sequence is limited, even if this sequence consists of only a few nucleotides. New, accurat...
Article
Structural and temporal inhomogeneities can have a marked influence on the performance of inorganic and biocatalytic systems alike. While these subtle variations are hardly ever accessible through bulk or ensemble averaged activity screening, insights into the molecular mechanisms underlying these diverse phenomena are absolutely critical for the d...
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Ever increasing demands in sensitivity and specificity of biosensors have recently established a trend towards the use of multivalent bioreceptors. This trend has also been introduced in the field of bacteriophage affinity peptides, where the entire phage is used as a receptor rather than the individual peptides. Although this approach is gaining i...
Conference Paper
Aptamers are short, single stranded DNA/RNA oligonucleotides with the ability to fold into well-defined three-dimensional structures, which are fundamental for their highly selective target recognition, rivaling thus antibodies in terms of affinity and specificity. Thanks to these properties, they have been integrated into different micro- and nano...
Article
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Major advancements in molecular biology and clinical diagnostics cannot be brought about strictly through the use of genomics based methods. Improved methods for protein detection and proteomic screening are an absolute necessity to complement to wealth of information offered by novel, high-throughput sequencing technologies. Only then will it be p...
Article
A home-built Fiber Optic Surface Plasmon Resonance platform (FO-SPR) was applied to directly screen PCR amplified DNA for mutations. The FO-SPR sensor was used for real-time monitoring of DNA duplex melting during high resolution temperature cycling. The signal of the DNA melting was enhanced by means of gold nanoparticle labels. This FO-SPR geneti...
Article
The rising prevalence to food allergies in the past two decades, together with the fact that the only existing therapy is avoidance of allergen-containing food next to the implementation of anti-allergic drugs, urges the need for improved performance of current assays to detect potential allergens in food products. Therein, the focus has been on ap...
Article
Affinity probe capillary electrophoresis (APCE) is potentially one of the most versatile technologies for protein diagnostics, offering an excellent balance between robustness, analysis speed and sensitivity. Combining the immunosensing and separating strength of capillary electrophoresis with the signal enhancement power of nucleic acid amplificat...
Article
Significant research efforts are continually being directed towards the development of sensitive and accurate surface plasmon resonance biosensors for sequence specific DNA detection. These sensors hold great potential for applications in healthcare and diagnostics. However, the performance of these sensors in practical usage scenarios is often lim...
Article
A new, ultra-sensitive genetic screening tool based on a fiber-optic (FO) surface plasmon biosensor and gold-labeled gene probes is presented. The assay allows for the detection and location of single-point mutations (SNP) at significantly reduced cost and high speed. The assay is evaluated for SNP detection of 3 different DNA targets, including a...
Article
Full-text available
In this paper a fiber optic surface plasmon resonance (FO-SPR) sensor was used to analyze the melting process of DNA linked to silica nanoparticles. Real-time monitoring of a DNA melting process has rarely been studied using surface plasmon resonance (SPR), since most commercial SPR setups do not allow for dynamic and accurate temperature control a...
Article
We present a novel strategy for patterning single magnetic beads by using digital microfluidics (DMF). A droplet containing a suspension of superparamagnetic particles is transported back and forth over an array of femtoliter-sized microwells by using electrowetting-on-dielectric actuation forces. Compared to existing methods, this technique allows...
Article
Affinity probecapillary electrophoresis (APCE) holds promise to be a powerful tool in diagnostic applications that rely on the selective and sensitive detection ofproteins. Aptamers can serve to unlock the full potential of the technology since their use opens up possibilities to unite the immuno-sensing and separating strength of capillary electro...
Article
The cationic dyes 9-aminoacridine (9AA) and safranine (Sf) were entrapped into silica spheres of about 0.2 μm diameter prepared by modified Stöber method. The fluorescent materials are investigated by steady-state and time-resolved emission, in addition of confocal fluorescence microscopy. Silica particles containing 9-aminoacridine (SP9AA) and saf...
Article
Real-time monitoring of solid-phase DNA amplification using a surface plasmon resonance sensor (SPR) with gold nanobead signal enhancement is presented. The sensor is applied in the quantification of a DNA aptamer and subsequent melting curve analysis. The system is suited for application in medical and food-safety diagnostics, and for the study an...
Article
Like antibodies, aptamers are highly valuable as bioreceptor molecules for protein biomarkers because of their excellent selectivity, specificity and stability. The integration of aptamers with semiconducting materials offers great potential for the development of reliable aptasensors. In this paper we present an aptamer-based impedimetric biosenso...
Article
This paper is the first report of a fiber optic SPR biosensor with nanobead signal enhancement. We evaluated the system with a bioassay for the fast and accurate detection of peanut allergens in complex food matrices. Three approaches of an immunoassay to detect Ara h1 peanut allergens in chocolate candy bars were compared; a label-free assay, a se...
Article
We report the first next generation sequencing (NGS) application to identify and quantify proteins. Customization of protein specific aptamers enabled direct conversion of serum protein information into NGS read outs. The intrinsic ability of aptamer sequencing to highly multiplex protein detection and quantification, together with the prospect of...
Article
The direct conversion of C3 sugars (or trioses) to alkyl lactates was achieved using zeolitecatalysts. This reaction represents a key step towards the efficient conversion of bio-glycerol or formaldehyde to added-value chemicals such as lactate derivatives. The highest yields and selectivities towards the desired lactate product were obtained with...
Article
We report a rationale for identifying superior dyes for stimulated-emission depletion (STED) microscopy. We compared the dyes pPDI and pTDI, which displayed excellent photostability in single-molecule spectroscopy. Surprisingly, their photostability and performance in STED microscopy differed significantly. While single pTDI molecules could be visu...
Article
Full-text available
We have selected aptamers binding to lysozyme from a DNA library using capillary electrophoresis-systematic evolution of ligands by exponential enrichment. During the selection process the dissociation constant of the ssDNA pool decreased from the micromolar to the low nanomolar range within five rounds of selection. The final aptamer had a dissoci...
Article
In this paper we present a fiber optic surface plasmon resonance (SPR) sensor as a reusable, cost-effective and label free biosensor for measuring DNA hybridization and DNA-protein interactions. This is the first paper that combines the concept of a fiber-based SPR system with DNA aptamer bioreceptors. The fibers were sputtered with a 50nm gold lay...
Article
The conversion of dihydroxyacetone to ethyl lactate catalysed by different solid acids was investigated by means of High-Throughput Experimentation. A mesoporous amorphous aluminosilicate catalyst displaying very high selectivity and a good yield towards the lactate was identified. The correlation between the type of acid sites and the catalytic be...
Article
Direct conversion of biomass derived trioses such as dihydroxyacetone (DHA) and glyceraldehyde (GLA) to alkyl lactates was carried out using alcohols over various Y type zeolite materials. The conversion takes place through a pyruvic aldehyde intermediate which subsequently undergoes esterification. The screened catalysts can be grouped based on th...
Article
A high-throughput research platform was developed for the preparation and subsequent catalytic liquid-phase screening of ion-exchanged zeolites, for instance with regard to their use as heterogeneous catalysts. In this system aqueous solutions and other liquid as well as solid reagents are employed as starting materials and 24 samples are prepared...
Article
Herein we report a new, one-step procedure for the metal-free ketonization of unsaturated fatty acid methyl esters and triacylglycerol mixtures with nitrous oxide (N2O). The conversion of various substrates can be tuned by parameters such as temperature, reaction time and N2O partial pressure. This ketonization chemistry offers various advantages o...
Article
Plasma coating technologies have been demonstrated as being promising for the fabrication of bioactive and biocompatible materials, among others. Reported efforts are exclusively focused on the two-step approaches, in which the bioactive component is first immobilized on a substrate, followed by a (vacuum) plasma polymerization treatment or vice ve...
Article
Various transition-metal-free oxides have been studied as catalysts for the epoxidation of cyclooctene with hydrogen peroxide by means of high-throughput experimentation. Different boron, aluminium, and gallium oxides were prepared according to various synthesis methods. A number of pure aluminium and gallium oxides showed very good catalytic perfo...

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